/* $OpenBSD: tcp_input.c,v 1.207 2007/06/15 18:23:06 markus Exp $ */
/* $NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $ */
/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)COPYRIGHT 1.1 (NRL) 17 January 1995
*
* NRL grants permission for redistribution and use in source and binary
* forms, with or without modification, of the software and documentation
* created at NRL provided that the following conditions are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgements:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* This product includes software developed at the Information
* Technology Division, US Naval Research Laboratory.
* 4. Neither the name of the NRL nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL AND CONTRIBUTORS ``AS
* IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
* PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL NRL OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* The views and conclusions contained in the software and documentation
* are those of the authors and should not be interpreted as representing
* official policies, either expressed or implied, of the US Naval
* Research Laboratory (NRL).
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/kernel.h>
#include <dev/rndvar.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_debug.h>
struct tcpiphdr tcp_saveti;
int tcp_mss_adv(struct ifnet *, int);
#ifdef INET6
#include <netinet6/in6_var.h>
#include <netinet6/nd6.h>
struct tcpipv6hdr tcp_saveti6;
/* for the packet header length in the mbuf */
#define M_PH_LEN(m) (((struct mbuf *)(m))->m_pkthdr.len)
#define M_V6_LEN(m) (M_PH_LEN(m) - sizeof(struct ip6_hdr))
#define M_V4_LEN(m) (M_PH_LEN(m) - sizeof(struct ip))
#endif /* INET6 */
int tcprexmtthresh = 3;
int tcptv_keep_init = TCPTV_KEEP_INIT;
extern u_long sb_max;
int tcp_rst_ppslim = 100; /* 100pps */
int tcp_rst_ppslim_count = 0;
struct timeval tcp_rst_ppslim_last;
int tcp_ackdrop_ppslim = 100; /* 100pps */
int tcp_ackdrop_ppslim_count = 0;
struct timeval tcp_ackdrop_ppslim_last;
#define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
/* for modulo comparisons of timestamps */
#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
/* for TCP SACK comparisons */
#define SEQ_MIN(a,b) (SEQ_LT(a,b) ? (a) : (b))
#define SEQ_MAX(a,b) (SEQ_GT(a,b) ? (a) : (b))
/*
* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint.
*/
#ifdef INET6
#define ND6_HINT(tp) \
do { \
if (tp && tp->t_inpcb && (tp->t_inpcb->inp_flags & INP_IPV6) && \
tp->t_inpcb->inp_route6.ro_rt) { \
nd6_nud_hint(tp->t_inpcb->inp_route6.ro_rt, NULL, 0); \
} \
} while (0)
#else
#define ND6_HINT(tp)
#endif
#ifdef TCP_ECN
/*
* ECN (Explicit Congestion Notification) support based on RFC3168
* implementation note:
* snd_last is used to track a recovery phase.
* when cwnd is reduced, snd_last is set to snd_max.
* while snd_last > snd_una, the sender is in a recovery phase and
* its cwnd should not be reduced again.
* snd_last follows snd_una when not in a recovery phase.
*/
#endif
/*
* Macro to compute ACK transmission behavior. Delay the ACK unless
* we have already delayed an ACK (must send an ACK every two segments).
* We also ACK immediately if we received a PUSH and the ACK-on-PUSH
* option is enabled.
*/
#define TCP_SETUP_ACK(tp, tiflags) \
do { \
if ((tp)->t_flags & TF_DELACK || \
(tcp_ack_on_push && (tiflags) & TH_PUSH)) \
tp->t_flags |= TF_ACKNOW; \
else \
TCP_SET_DELACK(tp); \
} while (0)
/*
* Insert segment ti into reassembly queue of tcp with
* control block tp. Return TH_FIN if reassembly now includes
* a segment with FIN. The macro form does the common case inline
* (segment is the next to be received on an established connection,
* and the queue is empty), avoiding linkage into and removal
* from the queue and repetition of various conversions.
* Set DELACK for segments received in order, but ack immediately
* when segments are out of order (so fast retransmit can work).
*/
int
tcp_reass(tp, th, m, tlen)
struct tcpcb *tp;
struct tcphdr *th;
struct mbuf *m;
int *tlen;
{
struct tcpqent *p, *q, *nq, *tiqe;
struct socket *so = tp->t_inpcb->inp_socket;
int flags;
/*
* Call with th==0 after become established to
* force pre-ESTABLISHED data up to user socket.
*/
if (th == 0)
goto present;
/*
* Allocate a new queue entry, before we throw away any data.
* If we can't, just drop the packet. XXX
*/
tiqe = pool_get(&tcpqe_pool, PR_NOWAIT);
if (tiqe == NULL) {
tiqe = TAILQ_LAST(&tp->t_segq, tcpqehead);
if (tiqe != NULL && th->th_seq == tp->rcv_nxt) {
/* Reuse last entry since new segment fills a hole */
m_freem(tiqe->tcpqe_m);
TAILQ_REMOVE(&tp->t_segq, tiqe, tcpqe_q);
}
if (tiqe == NULL || th->th_seq != tp->rcv_nxt) {
/* Flush segment queue for this connection */
tcp_freeq(tp);
tcpstat.tcps_rcvmemdrop++;
m_freem(m);
return (0);
}
}
/*
* Find a segment which begins after this one does.
*/
for (p = NULL, q = TAILQ_FIRST(&tp->t_segq); q != NULL;
p = q, q = TAILQ_NEXT(q, tcpqe_q))
if (SEQ_GT(q->tcpqe_tcp->th_seq, th->th_seq))
break;
/*
* If there is a preceding segment, it may provide some of
* our data already. If so, drop the data from the incoming
* segment. If it provides all of our data, drop us.
*/
if (p != NULL) {
struct tcphdr *phdr = p->tcpqe_tcp;
int i;
/* conversion to int (in i) handles seq wraparound */
i = phdr->th_seq + phdr->th_reseqlen - th->th_seq;
if (i > 0) {
if (i >= *tlen) {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += *tlen;
m_freem(m);
pool_put(&tcpqe_pool, tiqe);
return (0);
}
m_adj(m, i);
*tlen -= i;
th->th_seq += i;
}
}
tcpstat.tcps_rcvoopack++;
tcpstat.tcps_rcvoobyte += *tlen;
/*
* While we overlap succeeding segments trim them or,
* if they are completely covered, dequeue them.
*/
for (; q != NULL; q = nq) {
struct tcphdr *qhdr = q->tcpqe_tcp;
int i = (th->th_seq + *tlen) - qhdr->th_seq;
if (i <= 0)
break;
if (i < qhdr->th_reseqlen) {
qhdr->th_seq += i;
qhdr->th_reseqlen -= i;
m_adj(q->tcpqe_m, i);
break;
}
nq = TAILQ_NEXT(q, tcpqe_q);
m_freem(q->tcpqe_m);
TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q);
pool_put(&tcpqe_pool, q);
}
/* Insert the new segment queue entry into place. */
tiqe->tcpqe_m = m;
th->th_reseqlen = *tlen;
tiqe->tcpqe_tcp = th;
if (p == NULL) {
TAILQ_INSERT_HEAD(&tp->t_segq, tiqe, tcpqe_q);
} else {
TAILQ_INSERT_AFTER(&tp->t_segq, p, tiqe, tcpqe_q);
}
present:
/*
* Present data to user, advancing rcv_nxt through
* completed sequence space.
*/
if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
return (0);
q = TAILQ_FIRST(&tp->t_segq);
if (q == NULL || q->tcpqe_tcp->th_seq != tp->rcv_nxt)
return (0);
if (tp->t_state == TCPS_SYN_RECEIVED && q->tcpqe_tcp->th_reseqlen)
return (0);
do {
tp->rcv_nxt += q->tcpqe_tcp->th_reseqlen;
flags = q->tcpqe_tcp->th_flags & TH_FIN;
nq = TAILQ_NEXT(q, tcpqe_q);
TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q);
ND6_HINT(tp);
if (so->so_state & SS_CANTRCVMORE)
m_freem(q->tcpqe_m);
else
sbappendstream(&so->so_rcv, q->tcpqe_m);
pool_put(&tcpqe_pool, q);
q = nq;
} while (q != NULL && q->tcpqe_tcp->th_seq == tp->rcv_nxt);
sorwakeup(so);
return (flags);
}
#ifdef INET6
int
tcp6_input(mp, offp, proto)
struct mbuf **mp;
int *offp, proto;
{
struct mbuf *m = *mp;
#if defined(NFAITH) && 0 < NFAITH
if (m->m_pkthdr.rcvif) {
if (m->m_pkthdr.rcvif->if_type == IFT_FAITH) {
/* XXX send icmp6 host/port unreach? */
m_freem(m);
return IPPROTO_DONE;
}
}
#endif
/*
* draft-itojun-ipv6-tcp-to-anycast
* better place to put this in?
*/
if (m->m_flags & M_ANYCAST6) {
if (m->m_len >= sizeof(struct ip6_hdr)) {
struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *);
icmp6_error(m, ICMP6_DST_UNREACH,
ICMP6_DST_UNREACH_ADDR,
(caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
} else
m_freem(m);
return IPPROTO_DONE;
}
tcp_input(m, *offp, proto);
return IPPROTO_DONE;
}
#endif
/*
* TCP input routine, follows pages 65-76 of the
* protocol specification dated September, 1981 very closely.
*/
void
tcp_input(struct mbuf *m, ...)
{
struct ip *ip;
struct inpcb *inp;
u_int8_t *optp = NULL;
int optlen = 0;
int tlen, off;
struct tcpcb *tp = 0;
int tiflags;
struct socket *so = NULL;
int todrop, acked, ourfinisacked, needoutput = 0;
int hdroptlen = 0;
short ostate = 0;
tcp_seq iss, *reuse = NULL;
u_long tiwin;
struct tcp_opt_info opti;
int iphlen;
va_list ap;
struct tcphdr *th;
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
#endif /* INET6 */
#ifdef IPSEC
struct m_tag *mtag;
struct tdb_ident *tdbi;
struct tdb *tdb;
int error, s;
#endif /* IPSEC */
int af;
#ifdef TCP_ECN
u_char iptos;
#endif
va_start(ap, m);
iphlen = va_arg(ap, int);
va_end(ap);
tcpstat.tcps_rcvtotal++;
opti.ts_present = 0;
opti.maxseg = 0;
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
* See below for AF specific multicast.
*/
if (m->m_flags & (M_BCAST|M_MCAST))
goto drop;
/*
* Before we do ANYTHING, we have to figure out if it's TCP/IPv6 or
* TCP/IPv4.
*/
switch (mtod(m, struct ip *)->ip_v) {
#ifdef INET6
case 6:
af = AF_INET6;
break;
#endif
case 4:
af = AF_INET;
break;
default:
m_freem(m);
return; /*EAFNOSUPPORT*/
}
/*
* Get IP and TCP header together in first mbuf.
* Note: IP leaves IP header in first mbuf.
*/
switch (af) {
case AF_INET:
#ifdef DIAGNOSTIC
if (iphlen < sizeof(struct ip)) {
m_freem(m);
return;
}
#endif /* DIAGNOSTIC */
break;
#ifdef INET6
case AF_INET6:
#ifdef DIAGNOSTIC
if (iphlen < sizeof(struct ip6_hdr)) {
m_freem(m);
return;
}
#endif /* DIAGNOSTIC */
break;
#endif
default:
m_freem(m);
return;
}
IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, sizeof(*th));
if (!th) {
tcpstat.tcps_rcvshort++;
return;
}
tlen = m->m_pkthdr.len - iphlen;
ip = NULL;
#ifdef INET6
ip6 = NULL;
#endif
switch (af) {
case AF_INET:
ip = mtod(m, struct ip *);
if (IN_MULTICAST(ip->ip_dst.s_addr) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
#ifdef TCP_ECN
/* save ip_tos before clearing it for checksum */
iptos = ip->ip_tos;
#endif
/*
* Checksum extended TCP header and data.
*/
if ((m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_OK) == 0) {
if (m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_BAD) {
tcpstat.tcps_inhwcsum++;
tcpstat.tcps_rcvbadsum++;
goto drop;
}
if (in4_cksum(m, IPPROTO_TCP, iphlen, tlen) != 0) {
tcpstat.tcps_rcvbadsum++;
goto drop;
}
} else {
m->m_pkthdr.csum_flags &= ~M_TCP_CSUM_IN_OK;
tcpstat.tcps_inhwcsum++;
}
break;
#ifdef INET6
case AF_INET6:
ip6 = mtod(m, struct ip6_hdr *);
#ifdef TCP_ECN
iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
#endif
/* Be proactive about malicious use of IPv4 mapped address */
if (IN6_IS_ADDR_V4MAPPED(&ip6->ip6_src) ||
IN6_IS_ADDR_V4MAPPED(&ip6->ip6_dst)) {
/* XXX stat */
goto drop;
}
/*
* Be proactive about unspecified IPv6 address in source.
* As we use all-zero to indicate unbounded/unconnected pcb,
* unspecified IPv6 address can be used to confuse us.
*
* Note that packets with unspecified IPv6 destination is
* already dropped in ip6_input.
*/
if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
/* XXX stat */
goto drop;
}
/* Discard packets to multicast */
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) {
/* XXX stat */
goto drop;
}
/*
* Checksum extended TCP header and data.
*/
if (in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), tlen)) {
tcpstat.tcps_rcvbadsum++;
goto drop;
}
break;
#endif
}
/*
* Check that TCP offset makes sense,
* pull out TCP options and adjust length. XXX
*/
off = th->th_off << 2;
if (off < sizeof(struct tcphdr) || off > tlen) {
tcpstat.tcps_rcvbadoff++;
goto drop;
}
tlen -= off;
if (off > sizeof(struct tcphdr)) {
IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, off);
if (!th) {
tcpstat.tcps_rcvshort++;
return;
}
optlen = off - sizeof(struct tcphdr);
optp = (u_int8_t *)(th + 1);
/*
* Do quick retrieval of timestamp options ("options
* prediction?"). If timestamp is the only option and it's
* formatted as recommended in RFC 1323 appendix A, we
* quickly get the values now and not bother calling
* tcp_dooptions(), etc.
*/
if ((optlen == TCPOLEN_TSTAMP_APPA ||
(optlen > TCPOLEN_TSTAMP_APPA &&
optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
*(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
(th->th_flags & TH_SYN) == 0) {
opti.ts_present = 1;
opti.ts_val = ntohl(*(u_int32_t *)(optp + 4));
opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
optp = NULL; /* we've parsed the options */
}
}
tiflags = th->th_flags;
/*
* Convert TCP protocol specific fields to host format.
*/
NTOHL(th->th_seq);
NTOHL(th->th_ack);
NTOHS(th->th_win);
NTOHS(th->th_urp);
/*
* Locate pcb for segment.
*/
findpcb:
switch (af) {
#ifdef INET6
case AF_INET6:
inp = in6_pcbhashlookup(&tcbtable, &ip6->ip6_src, th->th_sport,
&ip6->ip6_dst, th->th_dport);
break;
#endif
case AF_INET:
inp = in_pcbhashlookup(&tcbtable, ip->ip_src, th->th_sport,
ip->ip_dst, th->th_dport);
break;
}
if (inp == 0) {
int inpl_flags = 0;
if (m->m_pkthdr.pf.flags & PF_TAG_TRANSLATE_LOCALHOST)
inpl_flags = INPLOOKUP_WILDCARD;
++tcpstat.tcps_pcbhashmiss;
switch (af) {
#ifdef INET6
case AF_INET6:
inp = in6_pcblookup_listen(&tcbtable,
&ip6->ip6_dst, th->th_dport, inpl_flags);
break;
#endif /* INET6 */
case AF_INET:
inp = in_pcblookup_listen(&tcbtable,
ip->ip_dst, th->th_dport, inpl_flags);
break;
}
/*
* If the state is CLOSED (i.e., TCB does not exist) then
* all data in the incoming segment is discarded.
* If the TCB exists but is in CLOSED state, it is embryonic,
* but should either do a listen or a connect soon.
*/
if (inp == 0) {
++tcpstat.tcps_noport;
goto dropwithreset_ratelim;
}
}
/* Check the minimum TTL for socket. */
if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl)
goto drop;
tp = intotcpcb(inp);
if (tp == 0)
goto dropwithreset_ratelim;
if (tp->t_state == TCPS_CLOSED)
goto drop;
/* Unscale the window into a 32-bit value. */
if ((tiflags & TH_SYN) == 0)
tiwin = th->th_win << tp->snd_scale;
else
tiwin = th->th_win;
so = inp->inp_socket;
if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) {
union syn_cache_sa src;
union syn_cache_sa dst;
bzero(&src, sizeof(src));
bzero(&dst, sizeof(dst));
switch (af) {
#ifdef INET
case AF_INET:
src.sin.sin_len = sizeof(struct sockaddr_in);
src.sin.sin_family = AF_INET;
src.sin.sin_addr = ip->ip_src;
src.sin.sin_port = th->th_sport;
dst.sin.sin_len = sizeof(struct sockaddr_in);
dst.sin.sin_family = AF_INET;
dst.sin.sin_addr = ip->ip_dst;
dst.sin.sin_port = th->th_dport;
break;
#endif
#ifdef INET6
case AF_INET6:
src.sin6.sin6_len = sizeof(struct sockaddr_in6);
src.sin6.sin6_family = AF_INET6;
src.sin6.sin6_addr = ip6->ip6_src;
src.sin6.sin6_port = th->th_sport;
dst.sin6.sin6_len = sizeof(struct sockaddr_in6);
dst.sin6.sin6_family = AF_INET6;
dst.sin6.sin6_addr = ip6->ip6_dst;
dst.sin6.sin6_port = th->th_dport;
break;
#endif /* INET6 */
default:
goto badsyn; /*sanity*/
}
if (so->so_options & SO_DEBUG) {
ostate = tp->t_state;
switch (af) {
#ifdef INET6
case AF_INET6:
bcopy(ip6, &tcp_saveti6.ti6_i, sizeof(*ip6));
bcopy(th, &tcp_saveti6.ti6_t, sizeof(*th));
break;
#endif
case AF_INET:
bcopy(ip, &tcp_saveti.ti_i, sizeof(*ip));
bcopy(th, &tcp_saveti.ti_t, sizeof(*th));
break;
}
}
if (so->so_options & SO_ACCEPTCONN) {
if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
if (tiflags & TH_RST) {
syn_cache_reset(&src.sa, &dst.sa, th);
} else if ((tiflags & (TH_ACK|TH_SYN)) ==
(TH_ACK|TH_SYN)) {
/*
* Received a SYN,ACK. This should
* never happen while we are in
* LISTEN. Send an RST.
*/
goto badsyn;
} else if (tiflags & TH_ACK) {
so = syn_cache_get(&src.sa, &dst.sa,
th, iphlen, tlen, so, m);
if (so == NULL) {
/*
* We don't have a SYN for
* this ACK; send an RST.
*/
goto badsyn;
} else if (so ==
(struct socket *)(-1)) {
/*
* We were unable to create
* the connection. If the
* 3-way handshake was
* completed, and RST has
* been sent to the peer.
* Since the mbuf might be
* in use for the reply,
* do not free it.
*/
m = NULL;
} else {
/*
* We have created a
* full-blown connection.
*/
tp = NULL;
inp = (struct inpcb *)so->so_pcb;
tp = intotcpcb(inp);
if (tp == NULL)
goto badsyn; /*XXX*/
/*
* Compute proper scaling
* value from buffer space
*/
tcp_rscale(tp, so->so_rcv.sb_hiwat);
goto after_listen;
}
} else {
/*
* None of RST, SYN or ACK was set.
* This is an invalid packet for a
* TCB in LISTEN state. Send a RST.
*/
goto badsyn;
}
} else {
/*
* Received a SYN.
*/
#ifdef INET6
/*
* If deprecated address is forbidden, we do
* not accept SYN to deprecated interface
* address to prevent any new inbound
* connection from getting established.
* When we do not accept SYN, we send a TCP
* RST, with deprecated source address (instead
* of dropping it). We compromise it as it is
* much better for peer to send a RST, and
* RST will be the final packet for the
* exchange.
*
* If we do not forbid deprecated addresses, we
* accept the SYN packet. RFC2462 does not
* suggest dropping SYN in this case.
* If we decipher RFC2462 5.5.4, it says like
* this:
* 1. use of deprecated addr with existing
* communication is okay - "SHOULD continue
* to be used"
* 2. use of it with new communication:
* (2a) "SHOULD NOT be used if alternate
* address with sufficient scope is
* available"
* (2b) nothing mentioned otherwise.
* Here we fall into (2b) case as we have no
* choice in our source address selection - we
* must obey the peer.
*
* The wording in RFC2462 is confusing, and
* there are multiple description text for
* deprecated address handling - worse, they
* are not exactly the same. I believe 5.5.4
* is the best one, so we follow 5.5.4.
*/
if (ip6 && !ip6_use_deprecated) {
struct in6_ifaddr *ia6;
if ((ia6 = in6ifa_ifpwithaddr(m->m_pkthdr.rcvif,
&ip6->ip6_dst)) &&
(ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
tp = NULL;
goto dropwithreset;
}
}
#endif
/*
* LISTEN socket received a SYN
* from itself? This can't possibly
* be valid; drop the packet.
*/
if (th->th_dport == th->th_sport) {
switch (af) {
#ifdef INET6
case AF_INET6:
if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_src,
&ip6->ip6_dst)) {
tcpstat.tcps_badsyn++;
goto drop;
}
break;
#endif /* INET6 */
case AF_INET:
if (ip->ip_dst.s_addr == ip->ip_src.s_addr) {
tcpstat.tcps_badsyn++;
goto drop;
}
break;
}
}
/*
* SYN looks ok; create compressed TCP
* state for it.
*/
if (so->so_qlen <= so->so_qlimit &&
syn_cache_add(&src.sa, &dst.sa, th, iphlen,
so, m, optp, optlen, &opti, reuse))
m = NULL;
}
goto drop;
}
}
after_listen:
#ifdef DIAGNOSTIC
/*
* Should not happen now that all embryonic connections
* are handled with compressed state.
*/
if (tp->t_state == TCPS_LISTEN)
panic("tcp_input: TCPS_LISTEN");
#endif
#ifdef IPSEC
/* Find most recent IPsec tag */
mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL);
s = splnet();
if (mtag != NULL) {
tdbi = (struct tdb_ident *)(mtag + 1);
tdb = gettdb(tdbi->spi, &tdbi->dst, tdbi->proto);
} else
tdb = NULL;
ipsp_spd_lookup(m, af, iphlen, &error, IPSP_DIRECTION_IN,
tdb, inp);
if (error) {
splx(s);
goto drop;
}
/* Latch SA */
if (inp->inp_tdb_in != tdb) {
if (tdb) {
tdb_add_inp(tdb, inp, 1);
if (inp->inp_ipo == NULL) {
inp->inp_ipo = ipsec_add_policy(inp, af,
IPSP_DIRECTION_OUT);
if (inp->inp_ipo == NULL) {
splx(s);
goto drop;
}
}
if (inp->inp_ipo->ipo_dstid == NULL &&
tdb->tdb_srcid != NULL) {
inp->inp_ipo->ipo_dstid = tdb->tdb_srcid;
tdb->tdb_srcid->ref_count++;
}
if (inp->inp_ipsec_remotecred == NULL &&
tdb->tdb_remote_cred != NULL) {
inp->inp_ipsec_remotecred =
tdb->tdb_remote_cred;
tdb->tdb_remote_cred->ref_count++;
}
if (inp->inp_ipsec_remoteauth == NULL &&
tdb->tdb_remote_auth != NULL) {
inp->inp_ipsec_remoteauth =
tdb->tdb_remote_auth;
tdb->tdb_remote_auth->ref_count++;
}
} else { /* Just reset */
TAILQ_REMOVE(&inp->inp_tdb_in->tdb_inp_in, inp,
inp_tdb_in_next);
inp->inp_tdb_in = NULL;
}
}
splx(s);
#endif /* IPSEC */
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
*/
tp->t_rcvtime = tcp_now;
if (TCPS_HAVEESTABLISHED(tp->t_state))
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
#ifdef TCP_SACK
if (tp->sack_enable)
tcp_del_sackholes(tp, th); /* Delete stale SACK holes */
#endif /* TCP_SACK */
/*
* Process options.
*/
#ifdef TCP_SIGNATURE
if (optp || (tp->t_flags & TF_SIGNATURE))
#else
if (optp)
#endif
if (tcp_dooptions(tp, optp, optlen, th, m, iphlen, &opti))
goto drop;
if (opti.ts_present && opti.ts_ecr) {
int rtt_test;
/* subtract out the tcp timestamp modulator */
opti.ts_ecr -= tp->ts_modulate;
/* make sure ts_ecr is sensible */
rtt_test = tcp_now - opti.ts_ecr;
if (rtt_test < 0 || rtt_test > TCP_RTT_MAX)
opti.ts_ecr = 0;
}
#ifdef TCP_ECN
/* if congestion experienced, set ECE bit in subsequent packets. */
if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE) {
tp->t_flags |= TF_RCVD_CE;
tcpstat.tcps_ecn_rcvce++;
}
#endif
/*
* Header prediction: check for the two common cases
* of a uni-directional data xfer. If the packet has
* no control flags, is in-sequence, the window didn't
* change and we're not retransmitting, it's a
* candidate. If the length is zero and the ack moved
* forward, we're the sender side of the xfer. Just
* free the data acked & wake any higher level process
* that was blocked waiting for space. If the length
* is non-zero and the ack didn't move, we're the
* receiver side. If we're getting packets in-order
* (the reassembly queue is empty), add the data to
* the socket buffer and note that we need a delayed ack.
*/
if (tp->t_state == TCPS_ESTABLISHED &&
#ifdef TCP_ECN
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ECE|TH_CWR|TH_ACK)) == TH_ACK &&
#else
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
#endif
(!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) &&
th->th_seq == tp->rcv_nxt &&
tiwin && tiwin == tp->snd_wnd &&
tp->snd_nxt == tp->snd_max) {
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* Fix from Braden, see Stevens p. 870
*/
if (opti.ts_present && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = tcp_now;
tp->ts_recent = opti.ts_val;
}
if (tlen == 0) {
if (SEQ_GT(th->th_ack, tp->snd_una) &&
SEQ_LEQ(th->th_ack, tp->snd_max) &&
tp->snd_cwnd >= tp->snd_wnd &&
tp->t_dupacks == 0) {
/*
* this is a pure ack for outstanding data.
*/
++tcpstat.tcps_predack;
if (opti.ts_present && opti.ts_ecr)
tcp_xmit_timer(tp, tcp_now - opti.ts_ecr);
else if (tp->t_rtttime &&
SEQ_GT(th->th_ack, tp->t_rtseq))
tcp_xmit_timer(tp,
tcp_now - tp->t_rtttime);
acked = th->th_ack - tp->snd_una;
tcpstat.tcps_rcvackpack++;
tcpstat.tcps_rcvackbyte += acked;
ND6_HINT(tp);
sbdrop(&so->so_snd, acked);
/*
* If we had a pending ICMP message that
* referres to data that have just been
* acknowledged, disregard the recorded ICMP
* message.
*/
if ((tp->t_flags & TF_PMTUD_PEND) &&
SEQ_GT(th->th_ack, tp->t_pmtud_th_seq))
tp->t_flags &= ~TF_PMTUD_PEND;
/*
* Keep track of the largest chunk of data
* acknowledged since last PMTU update
*/
if (tp->t_pmtud_mss_acked < acked)
tp->t_pmtud_mss_acked = acked;
tp->snd_una = th->th_ack;
#if defined(TCP_SACK) || defined(TCP_ECN)
/*
* We want snd_last to track snd_una so
* as to avoid sequence wraparound problems
* for very large transfers.
*/
#ifdef TCP_ECN
if (SEQ_GT(tp->snd_una, tp->snd_last))
#endif
tp->snd_last = tp->snd_una;
#endif /* TCP_SACK */
#if defined(TCP_SACK) && defined(TCP_FACK)
tp->snd_fack = tp->snd_una;
tp->retran_data = 0;
#endif /* TCP_FACK */
m_freem(m);
/*
* If all outstanding data are acked, stop
* retransmit timer, otherwise restart timer
* using current (possibly backed-off) value.
* If process is waiting for space,
* wakeup/selwakeup/signal. If data
* are ready to send, let tcp_output
* decide between more output or persist.
*/
if (tp->snd_una == tp->snd_max)
TCP_TIMER_DISARM(tp, TCPT_REXMT);
else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
if (sb_notify(&so->so_snd))
sowwakeup(so);
if (so->so_snd.sb_cc)
(void) tcp_output(tp);
return;
}
} else if (th->th_ack == tp->snd_una &&
TAILQ_EMPTY(&tp->t_segq) &&
tlen <= sbspace(&so->so_rcv)) {
/*
* This is a pure, in-sequence data packet
* with nothing on the reassembly queue and
* we have enough buffer space to take it.
*/
#ifdef TCP_SACK
/* Clean receiver SACK report if present */
if (tp->sack_enable && tp->rcv_numsacks)
tcp_clean_sackreport(tp);
#endif /* TCP_SACK */
++tcpstat.tcps_preddat;
tp->rcv_nxt += tlen;
tcpstat.tcps_rcvpack++;
tcpstat.tcps_rcvbyte += tlen;
ND6_HINT(tp);
/*
* Drop TCP, IP headers and TCP options then add data
* to socket buffer.
*/
if (so->so_state & SS_CANTRCVMORE)
m_freem(m);
else {
m_adj(m, iphlen + off);
sbappendstream(&so->so_rcv, m);
}
sorwakeup(so);
TCP_SETUP_ACK(tp, tiflags);
if (tp->t_flags & TF_ACKNOW)
(void) tcp_output(tp);
return;
}
}
/*
* Compute mbuf offset to TCP data segment.
*/
hdroptlen = iphlen + off;
/*
* Calculate amount of space in receive window,
* and then do TCP input processing.
* Receive window is amount of space in rcv queue,
* but not less than advertised window.
*/
{ int win;
win = sbspace(&so->so_rcv);
if (win < 0)
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
}
switch (tp->t_state) {
/*
* If the state is SYN_RECEIVED:
* if seg contains SYN/ACK, send an RST.
* if seg contains an ACK, but not for our SYN/ACK, send an RST
*/
case TCPS_SYN_RECEIVED:
if (tiflags & TH_ACK) {
if (tiflags & TH_SYN) {
tcpstat.tcps_badsyn++;
goto dropwithreset;
}
if (SEQ_LEQ(th->th_ack, tp->snd_una) ||
SEQ_GT(th->th_ack, tp->snd_max))
goto dropwithreset;
}
break;
/*
* If the state is SYN_SENT:
* if seg contains an ACK, but not for our SYN, drop the input.
* if seg contains a RST, then drop the connection.
* if seg does not contain SYN, then drop it.
* Otherwise this is an acceptable SYN segment
* initialize tp->rcv_nxt and tp->irs
* if seg contains ack then advance tp->snd_una
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
* arrange for segment to be acked (eventually)
* continue processing rest of data/controls, beginning with URG
*/
case TCPS_SYN_SENT:
if ((tiflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->iss) ||
SEQ_GT(th->th_ack, tp->snd_max)))
goto dropwithreset;
if (tiflags & TH_RST) {
#ifdef TCP_ECN
/* if ECN is enabled, fall back to non-ecn at rexmit */
if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN))
goto drop;
#endif
if (tiflags & TH_ACK)
tp = tcp_drop(tp, ECONNREFUSED);
goto drop;
}
if ((tiflags & TH_SYN) == 0)
goto drop;
if (tiflags & TH_ACK) {
tp->snd_una = th->th_ack;
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
}
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->irs = th->th_seq;
tcp_mss(tp, opti.maxseg);
/* Reset initial window to 1 segment for retransmit */
if (tp->t_rxtshift > 0)
tp->snd_cwnd = tp->t_maxseg;
tcp_rcvseqinit(tp);
tp->t_flags |= TF_ACKNOW;
#ifdef TCP_SACK
/*
* If we've sent a SACK_PERMITTED option, and the peer
* also replied with one, then TF_SACK_PERMIT should have
* been set in tcp_dooptions(). If it was not, disable SACKs.
*/
if (tp->sack_enable)
tp->sack_enable = tp->t_flags & TF_SACK_PERMIT;
#endif
#ifdef TCP_ECN
/*
* if ECE is set but CWR is not set for SYN-ACK, or
* both ECE and CWR are set for simultaneous open,
* peer is ECN capable.
*/
if (tcp_do_ecn) {
if ((tiflags & (TH_ACK|TH_ECE|TH_CWR))
== (TH_ACK|TH_ECE) ||
(tiflags & (TH_ACK|TH_ECE|TH_CWR))
== (TH_ECE|TH_CWR)) {
tp->t_flags |= TF_ECN_PERMIT;
tiflags &= ~(TH_ECE|TH_CWR);
tcpstat.tcps_ecn_accepts++;
}
}
#endif
if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
tcpstat.tcps_connects++;
soisconnected(so);
tp->t_state = TCPS_ESTABLISHED;
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
/* Do window scaling on this connection? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
tcp_reass_lock(tp);
(void) tcp_reass(tp, (struct tcphdr *)0,
(struct mbuf *)0, &tlen);
tcp_reass_unlock(tp);
/*
* if we didn't have to retransmit the SYN,
* use its rtt as our initial srtt & rtt var.
*/
if (tp->t_rtttime)
tcp_xmit_timer(tp, tcp_now - tp->t_rtttime);
/*
* Since new data was acked (the SYN), open the
* congestion window by one MSS. We do this
* here, because we won't go through the normal
* ACK processing below. And since this is the
* start of the connection, we know we are in
* the exponential phase of slow-start.
*/
tp->snd_cwnd += tp->t_maxseg;
} else
tp->t_state = TCPS_SYN_RECEIVED;
#if 0
trimthenstep6:
#endif
/*
* Advance th->th_seq to correspond to first data byte.
* If data, trim to stay within window,
* dropping FIN if necessary.
*/
th->th_seq++;
if (tlen > tp->rcv_wnd) {
todrop = tlen - tp->rcv_wnd;
m_adj(m, -todrop);
tlen = tp->rcv_wnd;
tiflags &= ~TH_FIN;
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += todrop;
}
tp->snd_wl1 = th->th_seq - 1;
tp->rcv_up = th->th_seq;
goto step6;
/*
* If a new connection request is received while in TIME_WAIT,
* drop the old connection and start over if the if the
* timestamp or the sequence numbers are above the previous
* ones.
*/
case TCPS_TIME_WAIT:
if (((tiflags & (TH_SYN|TH_ACK)) == TH_SYN) &&
((opti.ts_present &&
TSTMP_LT(tp->ts_recent, opti.ts_val)) ||
SEQ_GT(th->th_seq, tp->rcv_nxt))) {
/*
* Advance the iss by at least 32768, but
* clear the msb in order to make sure
* that SEG_LT(snd_nxt, iss).
*/
iss = tp->snd_nxt +
((arc4random() & 0x7fffffff) | 0x8000);
reuse = &iss;
tp = tcp_close(tp);
goto findpcb;
}
}
/*
* States other than LISTEN or SYN_SENT.
* First check timestamp, if present.
* Then check that at least some bytes of segment are within
* receive window. If segment begins before rcv_nxt,
* drop leading data (and SYN); if nothing left, just ack.
*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than opti.ts_recent, drop it.
*/
if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
TSTMP_LT(opti.ts_val, tp->ts_recent)) {
/* Check to see if ts_recent is over 24 days old. */
if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
/*
* Invalidate ts_recent. If this segment updates
* ts_recent, the age will be reset later and ts_recent
* will get a valid value. If it does not, setting
* ts_recent to zero will at least satisfy the
* requirement that zero be placed in the timestamp
* echo reply when ts_recent isn't valid. The
* age isn't reset until we get a valid ts_recent
* because we don't want out-of-order segments to be
* dropped when ts_recent is old.
*/
tp->ts_recent = 0;
} else {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += tlen;
tcpstat.tcps_pawsdrop++;
goto dropafterack;
}
}
todrop = tp->rcv_nxt - th->th_seq;
if (todrop > 0) {
if (tiflags & TH_SYN) {
tiflags &= ~TH_SYN;
th->th_seq++;
if (th->th_urp > 1)
th->th_urp--;
else
tiflags &= ~TH_URG;
todrop--;
}
if (todrop > tlen ||
(todrop == tlen && (tiflags & TH_FIN) == 0)) {
/*
* Any valid FIN must be to the left of the
* window. At this point, FIN must be a
* duplicate or out-of-sequence, so drop it.
*/
tiflags &= ~TH_FIN;
/*
* Send ACK to resynchronize, and drop any data,
* but keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_rcvdupbyte += todrop = tlen;
tcpstat.tcps_rcvduppack++;
} else {
tcpstat.tcps_rcvpartduppack++;
tcpstat.tcps_rcvpartdupbyte += todrop;
}
hdroptlen += todrop; /* drop from head afterwards */
th->th_seq += todrop;
tlen -= todrop;
if (th->th_urp > todrop)
th->th_urp -= todrop;
else {
tiflags &= ~TH_URG;
th->th_urp = 0;
}
}
/*
* If new data are received on a connection after the
* user processes are gone, then RST the other end.
*/
if ((so->so_state & SS_NOFDREF) &&
tp->t_state > TCPS_CLOSE_WAIT && tlen) {
tp = tcp_close(tp);
tcpstat.tcps_rcvafterclose++;
goto dropwithreset;
}
/*
* If segment ends after window, drop trailing data
* (and PUSH and FIN); if nothing left, just ACK.
*/
todrop = (th->th_seq + tlen) - (tp->rcv_nxt+tp->rcv_wnd);
if (todrop > 0) {
tcpstat.tcps_rcvpackafterwin++;
if (todrop >= tlen) {
tcpstat.tcps_rcvbyteafterwin += tlen;
/*
* If window is closed can only take segments at
* window edge, and have to drop data and PUSH from
* incoming segments. Continue processing, but
* remember to ack. Otherwise, drop segment
* and ack.
*/
if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_rcvwinprobe++;
} else
goto dropafterack;
} else
tcpstat.tcps_rcvbyteafterwin += todrop;
m_adj(m, -todrop);
tlen -= todrop;
tiflags &= ~(TH_PUSH|TH_FIN);
}
/*
* If last ACK falls within this segment's sequence numbers,
* record its timestamp if it's more recent.
* Cf fix from Braden, see Stevens p. 870
*/
if (opti.ts_present && TSTMP_GEQ(opti.ts_val, tp->ts_recent) &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
if (SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
((tiflags & (TH_SYN|TH_FIN)) != 0)))
tp->ts_recent = opti.ts_val;
else
tp->ts_recent = 0;
tp->ts_recent_age = tcp_now;
}
/*
* If the RST bit is set examine the state:
* SYN_RECEIVED STATE:
* If passive open, return to LISTEN state.
* If active open, inform user that connection was refused.
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
* Inform user that connection was reset, and close tcb.
* CLOSING, LAST_ACK, TIME_WAIT STATES
* Close the tcb.
*/
if (tiflags & TH_RST) {
if (th->th_seq != tp->last_ack_sent &&
th->th_seq != tp->rcv_nxt &&
th->th_seq != (tp->rcv_nxt + 1))
goto drop;
switch (tp->t_state) {
case TCPS_SYN_RECEIVED:
#ifdef TCP_ECN
/* if ECN is enabled, fall back to non-ecn at rexmit */
if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN))
goto drop;
#endif
so->so_error = ECONNREFUSED;
goto close;
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
so->so_error = ECONNRESET;
close:
tp->t_state = TCPS_CLOSED;
tcpstat.tcps_drops++;
tp = tcp_close(tp);
goto drop;
case TCPS_CLOSING:
case TCPS_LAST_ACK:
case TCPS_TIME_WAIT:
tp = tcp_close(tp);
goto drop;
}
}
/*
* If a SYN is in the window, then this is an
* error and we ACK and drop the packet.
*/
if (tiflags & TH_SYN)
goto dropafterack_ratelim;
/*
* If the ACK bit is off we drop the segment and return.
*/
if ((tiflags & TH_ACK) == 0) {
if (tp->t_flags & TF_ACKNOW)
goto dropafterack;
else
goto drop;
}
/*
* Ack processing.
*/
switch (tp->t_state) {
/*
* In SYN_RECEIVED state, the ack ACKs our SYN, so enter
* ESTABLISHED state and continue processing.
* The ACK was checked above.
*/
case TCPS_SYN_RECEIVED:
tcpstat.tcps_connects++;
soisconnected(so);
tp->t_state = TCPS_ESTABLISHED;
TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle);
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
tcp_reass_lock(tp);
(void) tcp_reass(tp, (struct tcphdr *)0, (struct mbuf *)0,
&tlen);
tcp_reass_unlock(tp);
tp->snd_wl1 = th->th_seq - 1;
/* fall into ... */
/*
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
* ACKs. If the ack is in the range
* tp->snd_una < th->th_ack <= tp->snd_max
* then advance tp->snd_una to th->th_ack and drop
* data from the retransmission queue. If this ACK reflects
* more up to date window information we update our window information.
*/
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
case TCPS_CLOSING:
case TCPS_LAST_ACK:
case TCPS_TIME_WAIT:
#ifdef TCP_ECN
/*
* if we receive ECE and are not already in recovery phase,
* reduce cwnd by half but don't slow-start.
* advance snd_last to snd_max not to reduce cwnd again
* until all outstanding packets are acked.
*/
if (tcp_do_ecn && (tiflags & TH_ECE)) {
if ((tp->t_flags & TF_ECN_PERMIT) &&
SEQ_GEQ(tp->snd_una, tp->snd_last)) {
u_int win;
win = min(tp->snd_wnd, tp->snd_cwnd) / tp->t_maxseg;
if (win > 1) {
tp->snd_ssthresh = win / 2 * tp->t_maxseg;
tp->snd_cwnd = tp->snd_ssthresh;
tp->snd_last = tp->snd_max;
tp->t_flags |= TF_SEND_CWR;
tcpstat.tcps_cwr_ecn++;
}
}
tcpstat.tcps_ecn_rcvece++;
}
/*
* if we receive CWR, we know that the peer has reduced
* its congestion window. stop sending ecn-echo.
*/
if ((tiflags & TH_CWR)) {
tp->t_flags &= ~TF_RCVD_CE;
tcpstat.tcps_ecn_rcvcwr++;
}
#endif /* TCP_ECN */
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
/*
* Duplicate/old ACK processing.
* Increments t_dupacks:
* Pure duplicate (same seq/ack/window, no data)
* Doesn't affect t_dupacks:
* Data packets.
* Normal window updates (window opens)
* Resets t_dupacks:
* New data ACKed.
* Window shrinks
* Old ACK
*/
if (tlen) {
/* Drop very old ACKs unless th_seq matches */
if (th->th_seq != tp->rcv_nxt &&
SEQ_LT(th->th_ack,
tp->snd_una - tp->max_sndwnd)) {
tcpstat.tcps_rcvacktooold++;
goto drop;
}
break;
}
/*
* If we get an old ACK, there is probably packet
* reordering going on. Be conservative and reset
* t_dupacks so that we are less agressive in
* doing a fast retransmit.
*/
if (th->th_ack != tp->snd_una) {
tp->t_dupacks = 0;
break;
}
if (tiwin == tp->snd_wnd) {
tcpstat.tcps_rcvdupack++;
/*
* If we have outstanding data (other than
* a window probe), this is a completely
* duplicate ack (ie, window info didn't
* change), the ack is the biggest we've
* seen and we've seen exactly our rexmt
* threshold of them, assume a packet
* has been dropped and retransmit it.
* Kludge snd_nxt & the congestion
* window so we send only this one
* packet.
*
* We know we're losing at the current
* window size so do congestion avoidance
* (set ssthresh to half the current window
* and pull our congestion window back to
* the new ssthresh).
*
* Dup acks mean that packets have left the
* network (they're now cached at the receiver)
* so bump cwnd by the amount in the receiver
* to keep a constant cwnd packets in the
* network.
*/
if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0)
tp->t_dupacks = 0;
#if defined(TCP_SACK) && defined(TCP_FACK)
/*
* In FACK, can enter fast rec. if the receiver
* reports a reass. queue longer than 3 segs.
*/
else if (++tp->t_dupacks == tcprexmtthresh ||
((SEQ_GT(tp->snd_fack, tcprexmtthresh *
tp->t_maxseg + tp->snd_una)) &&
SEQ_GT(tp->snd_una, tp->snd_last))) {
#else
else if (++tp->t_dupacks == tcprexmtthresh) {
#endif /* TCP_FACK */
tcp_seq onxt = tp->snd_nxt;
u_long win =
ulmin(tp->snd_wnd, tp->snd_cwnd) /
2 / tp->t_maxseg;
#if defined(TCP_SACK) || defined(TCP_ECN)
if (SEQ_LT(th->th_ack, tp->snd_last)){
/*
* False fast retx after
* timeout. Do not cut window.
*/
tp->t_dupacks = 0;
goto drop;
}
#endif
if (win < 2)
win = 2;
tp->snd_ssthresh = win * tp->t_maxseg;
#if defined(TCP_SACK)
tp->snd_last = tp->snd_max;
#endif
#ifdef TCP_SACK
if (tp->sack_enable) {
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->t_rtttime = 0;
#ifdef TCP_ECN
tp->t_flags |= TF_SEND_CWR;
#endif
#if 1 /* TCP_ECN */
tcpstat.tcps_cwr_frecovery++;
#endif
tcpstat.tcps_sack_recovery_episode++;
#if defined(TCP_SACK) && defined(TCP_FACK)
tp->t_dupacks = tcprexmtthresh;
(void) tcp_output(tp);
/*
* During FR, snd_cwnd is held
* constant for FACK.
*/
tp->snd_cwnd = tp->snd_ssthresh;
#else
/*
* tcp_output() will send
* oldest SACK-eligible rtx.
*/
(void) tcp_output(tp);
tp->snd_cwnd = tp->snd_ssthresh+
tp->t_maxseg * tp->t_dupacks;
#endif /* TCP_FACK */
goto drop;
}
#endif /* TCP_SACK */
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->t_rtttime = 0;
tp->snd_nxt = th->th_ack;
tp->snd_cwnd = tp->t_maxseg;
#ifdef TCP_ECN
tp->t_flags |= TF_SEND_CWR;
#endif
#if 1 /* TCP_ECN */
tcpstat.tcps_cwr_frecovery++;
#endif
tcpstat.tcps_sndrexmitfast++;
(void) tcp_output(tp);
tp->snd_cwnd = tp->snd_ssthresh +
tp->t_maxseg * tp->t_dupacks;
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
goto drop;
} else if (tp->t_dupacks > tcprexmtthresh) {
#if defined(TCP_SACK) && defined(TCP_FACK)
/*
* while (awnd < cwnd)
* sendsomething();
*/
if (tp->sack_enable) {
if (tp->snd_awnd < tp->snd_cwnd)
tcp_output(tp);
goto drop;
}
#endif /* TCP_FACK */
tp->snd_cwnd += tp->t_maxseg;
(void) tcp_output(tp);
goto drop;
}
} else if (tiwin < tp->snd_wnd) {
/*
* The window was retracted! Previous dup
* ACKs may have been due to packets arriving
* after the shrunken window, not a missing
* packet, so play it safe and reset t_dupacks
*/
tp->t_dupacks = 0;
}
break;
}
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
#if defined(TCP_SACK)
if (tp->sack_enable) {
if (tp->t_dupacks >= tcprexmtthresh) {
/* Check for a partial ACK */
if (tcp_sack_partialack(tp, th)) {
#if defined(TCP_SACK) && defined(TCP_FACK)
/* Force call to tcp_output */
if (tp->snd_awnd < tp->snd_cwnd)
needoutput = 1;
#else
tp->snd_cwnd += tp->t_maxseg;
needoutput = 1;
#endif /* TCP_FACK */
} else {
/* Out of fast recovery */
tp->snd_cwnd = tp->snd_ssthresh;
if (tcp_seq_subtract(tp->snd_max,
th->th_ack) < tp->snd_ssthresh)
tp->snd_cwnd =
tcp_seq_subtract(tp->snd_max,
th->th_ack);
tp->t_dupacks = 0;
#if defined(TCP_SACK) && defined(TCP_FACK)
if (SEQ_GT(th->th_ack, tp->snd_fack))
tp->snd_fack = th->th_ack;
#endif /* TCP_FACK */
}
}
} else {
if (tp->t_dupacks >= tcprexmtthresh &&
!tcp_newreno(tp, th)) {
/* Out of fast recovery */
tp->snd_cwnd = tp->snd_ssthresh;
if (tcp_seq_subtract(tp->snd_max, th->th_ack) <
tp->snd_ssthresh)
tp->snd_cwnd =
tcp_seq_subtract(tp->snd_max,
th->th_ack);
tp->t_dupacks = 0;
}
}
if (tp->t_dupacks < tcprexmtthresh)
tp->t_dupacks = 0;
#else /* else no TCP_SACK */
if (tp->t_dupacks >= tcprexmtthresh &&
tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
tp->t_dupacks = 0;
#endif
if (SEQ_GT(th->th_ack, tp->snd_max)) {
tcpstat.tcps_rcvacktoomuch++;
goto dropafterack_ratelim;
}
acked = th->th_ack - tp->snd_una;
tcpstat.tcps_rcvackpack++;
tcpstat.tcps_rcvackbyte += acked;
/*
* If we have a timestamp reply, update smoothed
* round trip time. If no timestamp is present but
* transmit timer is running and timed sequence
* number was acked, update smoothed round trip time.
* Since we now have an rtt measurement, cancel the
* timer backoff (cf., Phil Karn's retransmit alg.).
* Recompute the initial retransmit timer.
*/
if (opti.ts_present && opti.ts_ecr)
tcp_xmit_timer(tp, tcp_now - opti.ts_ecr);
else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq))
tcp_xmit_timer(tp, tcp_now - tp->t_rtttime);
/*
* If all outstanding data is acked, stop retransmit
* timer and remember to restart (more output or persist).
* If there is more data to be acked, restart retransmit
* timer, using current (possibly backed-off) value.
*/
if (th->th_ack == tp->snd_max) {
TCP_TIMER_DISARM(tp, TCPT_REXMT);
needoutput = 1;
} else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0)
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
/*
* When new data is acked, open the congestion window.
* If the window gives us less than ssthresh packets
* in flight, open exponentially (maxseg per packet).
* Otherwise open linearly: maxseg per window
* (maxseg^2 / cwnd per packet).
*/
{
u_int cw = tp->snd_cwnd;
u_int incr = tp->t_maxseg;
if (cw > tp->snd_ssthresh)
incr = incr * incr / cw;
#if defined (TCP_SACK)
if (tp->t_dupacks < tcprexmtthresh)
#endif
tp->snd_cwnd = ulmin(cw + incr, TCP_MAXWIN<<tp->snd_scale);
}
ND6_HINT(tp);
if (acked > so->so_snd.sb_cc) {
tp->snd_wnd -= so->so_snd.sb_cc;
sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
ourfinisacked = 1;
} else {
sbdrop(&so->so_snd, acked);
tp->snd_wnd -= acked;
ourfinisacked = 0;
}
if (sb_notify(&so->so_snd))
sowwakeup(so);
/*
* If we had a pending ICMP message that referred to data
* that have just been acknowledged, disregard the recorded
* ICMP message.
*/
if ((tp->t_flags & TF_PMTUD_PEND) &&
SEQ_GT(th->th_ack, tp->t_pmtud_th_seq))
tp->t_flags &= ~TF_PMTUD_PEND;
/*
* Keep track of the largest chunk of data acknowledged
* since last PMTU update
*/
if (tp->t_pmtud_mss_acked < acked)
tp->t_pmtud_mss_acked = acked;
tp->snd_una = th->th_ack;
#ifdef TCP_ECN
/* sync snd_last with snd_una */
if (SEQ_GT(tp->snd_una, tp->snd_last))
tp->snd_last = tp->snd_una;
#endif
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
#if defined (TCP_SACK) && defined (TCP_FACK)
if (SEQ_GT(tp->snd_una, tp->snd_fack)) {
tp->snd_fack = tp->snd_una;
/* Update snd_awnd for partial ACK
* without any SACK blocks.
*/
tp->snd_awnd = tcp_seq_subtract(tp->snd_nxt,
tp->snd_fack) + tp->retran_data;
}
#endif
switch (tp->t_state) {
/*
* In FIN_WAIT_1 STATE in addition to the processing
* for the ESTABLISHED state if our FIN is now acknowledged
* then enter FIN_WAIT_2.
*/
case TCPS_FIN_WAIT_1:
if (ourfinisacked) {
/*
* If we can't receive any more
* data, then closing user can proceed.
* Starting the timer is contrary to the
* specification, but if we don't get a FIN
* we'll hang forever.
*/
if (so->so_state & SS_CANTRCVMORE) {
soisdisconnected(so);
TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_maxidle);
}
tp->t_state = TCPS_FIN_WAIT_2;
}
break;
/*
* In CLOSING STATE in addition to the processing for
* the ESTABLISHED state if the ACK acknowledges our FIN
* then enter the TIME-WAIT state, otherwise ignore
* the segment.
*/
case TCPS_CLOSING:
if (ourfinisacked) {
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL);
soisdisconnected(so);
}
break;
/*
* In LAST_ACK, we may still be waiting for data to drain
* and/or to be acked, as well as for the ack of our FIN.
* If our FIN is now acknowledged, delete the TCB,
* enter the closed state and return.
*/
case TCPS_LAST_ACK:
if (ourfinisacked) {
tp = tcp_close(tp);
goto drop;
}
break;
/*
* In TIME_WAIT state the only thing that should arrive
* is a retransmission of the remote FIN. Acknowledge
* it and restart the finack timer.
*/
case TCPS_TIME_WAIT:
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL);
goto dropafterack;
}
}
step6:
/*
* Update window information.
* Don't look at window if no ACK: TAC's send garbage on first SYN.
*/
if ((tiflags & TH_ACK) &&
(SEQ_LT(tp->snd_wl1, th->th_seq) || (tp->snd_wl1 == th->th_seq &&
(SEQ_LT(tp->snd_wl2, th->th_ack) ||
(tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
/* keep track of pure window updates */
if (tlen == 0 &&
tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
tcpstat.tcps_rcvwinupd++;
tp->snd_wnd = tiwin;
tp->snd_wl1 = th->th_seq;
tp->snd_wl2 = th->th_ack;
if (tp->snd_wnd > tp->max_sndwnd)
tp->max_sndwnd = tp->snd_wnd;
needoutput = 1;
}
/*
* Process segments with URG.
*/
if ((tiflags & TH_URG) && th->th_urp &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
/*
* This is a kludge, but if we receive and accept
* random urgent pointers, we'll crash in
* soreceive. It's hard to imagine someone
* actually wanting to send this much urgent data.
*/
if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
th->th_urp = 0; /* XXX */
tiflags &= ~TH_URG; /* XXX */
goto dodata; /* XXX */
}
/*
* If this segment advances the known urgent pointer,
* then mark the data stream. This should not happen
* in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
* a FIN has been received from the remote side.
* In these states we ignore the URG.
*
* According to RFC961 (Assigned Protocols),
* the urgent pointer points to the last octet
* of urgent data. We continue, however,
* to consider it to indicate the first octet
* of data past the urgent section as the original
* spec states (in one of two places).
*/
if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
tp->rcv_up = th->th_seq + th->th_urp;
so->so_oobmark = so->so_rcv.sb_cc +
(tp->rcv_up - tp->rcv_nxt) - 1;
if (so->so_oobmark == 0)
so->so_state |= SS_RCVATMARK;
sohasoutofband(so);
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
}
/*
* Remove out of band data so doesn't get presented to user.
* This can happen independent of advancing the URG pointer,
* but if two URG's are pending at once, some out-of-band
* data may creep in... ick.
*/
if (th->th_urp <= (u_int16_t) tlen
#ifdef SO_OOBINLINE
&& (so->so_options & SO_OOBINLINE) == 0
#endif
)
tcp_pulloutofband(so, th->th_urp, m, hdroptlen);
} else
/*
* If no out of band data is expected,
* pull receive urgent pointer along
* with the receive window.
*/
if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
tp->rcv_up = tp->rcv_nxt;
dodata: /* XXX */
/*
* Process the segment text, merging it into the TCP sequencing queue,
* and arranging for acknowledgment of receipt if necessary.
* This process logically involves adjusting tp->rcv_wnd as data
* is presented to the user (this happens in tcp_usrreq.c,
* case PRU_RCVD). If a FIN has already been received on this
* connection then we just ignore the text.
*/
if ((tlen || (tiflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
#ifdef TCP_SACK
tcp_seq laststart = th->th_seq;
tcp_seq lastend = th->th_seq + tlen;
#endif
tcp_reass_lock(tp);
if (th->th_seq == tp->rcv_nxt && TAILQ_EMPTY(&tp->t_segq) &&
tp->t_state == TCPS_ESTABLISHED) {
tcp_reass_unlock(tp);
TCP_SETUP_ACK(tp, tiflags);
tp->rcv_nxt += tlen;
tiflags = th->th_flags & TH_FIN;
tcpstat.tcps_rcvpack++;
tcpstat.tcps_rcvbyte += tlen;
ND6_HINT(tp);
if (so->so_state & SS_CANTRCVMORE)
m_freem(m);
else {
m_adj(m, hdroptlen);
sbappendstream(&so->so_rcv, m);
}
sorwakeup(so);
} else {
m_adj(m, hdroptlen);
tiflags = tcp_reass(tp, th, m, &tlen);
tcp_reass_unlock(tp);
tp->t_flags |= TF_ACKNOW;
}
#ifdef TCP_SACK
if (tp->sack_enable)
tcp_update_sack_list(tp, laststart, lastend);
#endif
/*
* variable len never referenced again in modern BSD,
* so why bother computing it ??
*/
#if 0
/*
* Note the amount of data that peer has sent into
* our window, in order to estimate the sender's
* buffer size.
*/
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
#endif /* 0 */
} else {
m_freem(m);
tiflags &= ~TH_FIN;
}
/*
* If FIN is received ACK the FIN and let the user know
* that the connection is closing. Ignore a FIN received before
* the connection is fully established.
*/
if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) {
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
socantrcvmore(so);
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt++;
}
switch (tp->t_state) {
/*
* In ESTABLISHED STATE enter the CLOSE_WAIT state.
*/
case TCPS_ESTABLISHED:
tp->t_state = TCPS_CLOSE_WAIT;
break;
/*
* If still in FIN_WAIT_1 STATE FIN has not been acked so
* enter the CLOSING state.
*/
case TCPS_FIN_WAIT_1:
tp->t_state = TCPS_CLOSING;
break;
/*
* In FIN_WAIT_2 state enter the TIME_WAIT state,
* starting the time-wait timer, turning off the other
* standard timers.
*/
case TCPS_FIN_WAIT_2:
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL);
soisdisconnected(so);
break;
/*
* In TIME_WAIT state restart the 2 MSL time_wait timer.
*/
case TCPS_TIME_WAIT:
TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL);
break;
}
}
if (so->so_options & SO_DEBUG) {
switch (tp->pf) {
#ifdef INET6
case PF_INET6:
tcp_trace(TA_INPUT, ostate, tp, (caddr_t) &tcp_saveti6,
0, tlen);
break;
#endif /* INET6 */
case PF_INET:
tcp_trace(TA_INPUT, ostate, tp, (caddr_t) &tcp_saveti,
0, tlen);
break;
}
}
/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW)) {
(void) tcp_output(tp);
}
return;
badsyn:
/*
* Received a bad SYN. Increment counters and dropwithreset.
*/
tcpstat.tcps_badsyn++;
tp = NULL;
goto dropwithreset;
dropafterack_ratelim:
if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count,
tcp_ackdrop_ppslim) == 0) {
/* XXX stat */
goto drop;
}
/* ...fall into dropafterack... */
dropafterack:
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*/
if (tiflags & TH_RST)
goto drop;
m_freem(m);
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
return;
dropwithreset_ratelim:
/*
* We may want to rate-limit RSTs in certain situations,
* particularly if we are sending an RST in response to
* an attempt to connect to or otherwise communicate with
* a port for which we have no socket.
*/
if (ppsratecheck(&tcp_rst_ppslim_last, &tcp_rst_ppslim_count,
tcp_rst_ppslim) == 0) {
/* XXX stat */
goto drop;
}
/* ...fall into dropwithreset... */
dropwithreset:
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
* Don't bother to respond to RST.
*/
if (tiflags & TH_RST)
goto drop;
if (tiflags & TH_ACK) {
tcp_respond(tp, mtod(m, caddr_t), m, (tcp_seq)0, th->th_ack,
TH_RST);
} else {
if (tiflags & TH_SYN)
tlen++;
tcp_respond(tp, mtod(m, caddr_t), m, th->th_seq + tlen,
(tcp_seq)0, TH_RST|TH_ACK);
}
return;
drop:
/*
* Drop space held by incoming segment and return.
*/
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) {
switch (tp->pf) {
#ifdef INET6
case PF_INET6:
tcp_trace(TA_DROP, ostate, tp, (caddr_t) &tcp_saveti6,
0, tlen);
break;
#endif /* INET6 */
case PF_INET:
tcp_trace(TA_DROP, ostate, tp, (caddr_t) &tcp_saveti,
0, tlen);
break;
}
}
m_freem(m);
return;
}
int
tcp_dooptions(tp, cp, cnt, th, m, iphlen, oi)
struct tcpcb *tp;
u_char *cp;
int cnt;
struct tcphdr *th;
struct mbuf *m;
int iphlen;
struct tcp_opt_info *oi;
{
u_int16_t mss = 0;
int opt, optlen;
#ifdef TCP_SIGNATURE
caddr_t sigp = NULL;
struct tdb *tdb = NULL;
#endif /* TCP_SIGNATURE */
for (; cp && cnt > 0; cnt -= optlen, cp += optlen) {
opt = cp[0];
if (opt == TCPOPT_EOL)
break;
if (opt == TCPOPT_NOP)
optlen = 1;
else {
if (cnt < 2)
break;
optlen = cp[1];
if (optlen < 2 || optlen > cnt)
break;
}
switch (opt) {
default:
continue;
case TCPOPT_MAXSEG:
if (optlen != TCPOLEN_MAXSEG)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
bcopy((char *) cp + 2, (char *) &mss, sizeof(mss));
NTOHS(mss);
oi->maxseg = mss;
break;
case TCPOPT_WINDOW:
if (optlen != TCPOLEN_WINDOW)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
tp->t_flags |= TF_RCVD_SCALE;
tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
break;
case TCPOPT_TIMESTAMP:
if (optlen != TCPOLEN_TIMESTAMP)
continue;
oi->ts_present = 1;
bcopy(cp + 2, &oi->ts_val, sizeof(oi->ts_val));
NTOHL(oi->ts_val);
bcopy(cp + 6, &oi->ts_ecr, sizeof(oi->ts_ecr));
NTOHL(oi->ts_ecr);
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
/*
* A timestamp received in a SYN makes
* it ok to send timestamp requests and replies.
*/
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = oi->ts_val;
tp->ts_recent_age = tcp_now;
break;
#ifdef TCP_SACK
case TCPOPT_SACK_PERMITTED:
if (!tp->sack_enable || optlen!=TCPOLEN_SACK_PERMITTED)
continue;
if (!(th->th_flags & TH_SYN))
continue;
if (TCPS_HAVERCVDSYN(tp->t_state))
continue;
/* MUST only be set on SYN */
tp->t_flags |= TF_SACK_PERMIT;
break;
case TCPOPT_SACK:
tcp_sack_option(tp, th, cp, optlen);
break;
#endif
#ifdef TCP_SIGNATURE
case TCPOPT_SIGNATURE:
if (optlen != TCPOLEN_SIGNATURE)
continue;
if (sigp && bcmp(sigp, cp + 2, 16))
return (-1);
sigp = cp + 2;
break;
#endif /* TCP_SIGNATURE */
}
}
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE) {
union sockaddr_union src, dst;
memset(&src, 0, sizeof(union sockaddr_union));
memset(&dst, 0, sizeof(union sockaddr_union));
switch (tp->pf) {
case 0:
#ifdef INET
case AF_INET:
src.sa.sa_len = sizeof(struct sockaddr_in);
src.sa.sa_family = AF_INET;
src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
dst.sa.sa_len = sizeof(struct sockaddr_in);
dst.sa.sa_family = AF_INET;
dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
break;
#endif
#ifdef INET6
case AF_INET6:
src.sa.sa_len = sizeof(struct sockaddr_in6);
src.sa.sa_family = AF_INET6;
src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
dst.sa.sa_len = sizeof(struct sockaddr_in6);
dst.sa.sa_family = AF_INET6;
dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
break;
#endif /* INET6 */
}
tdb = gettdbbysrcdst(0, &src, &dst, IPPROTO_TCP);
/*
* We don't have an SA for this peer, so we turn off
* TF_SIGNATURE on the listen socket
*/
if (tdb == NULL && tp->t_state == TCPS_LISTEN)
tp->t_flags &= ~TF_SIGNATURE;
}
if ((sigp ? TF_SIGNATURE : 0) ^ (tp->t_flags & TF_SIGNATURE)) {
tcpstat.tcps_rcvbadsig++;
return (-1);
}
if (sigp) {
char sig[16];
if (tdb == NULL) {
tcpstat.tcps_rcvbadsig++;
return (-1);
}
if (tcp_signature(tdb, tp->pf, m, th, iphlen, 1, sig) < 0)
return (-1);
if (bcmp(sig, sigp, 16)) {
tcpstat.tcps_rcvbadsig++;
return (-1);
}
tcpstat.tcps_rcvgoodsig++;
}
#endif /* TCP_SIGNATURE */
return (0);
}
#if defined(TCP_SACK)
u_long
tcp_seq_subtract(a, b)
u_long a, b;
{
return ((long)(a - b));
}
#endif
#ifdef TCP_SACK
/*
* This function is called upon receipt of new valid data (while not in header
* prediction mode), and it updates the ordered list of sacks.
*/
void
tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart,
tcp_seq rcv_lastend)
{
/*
* First reported block MUST be the most recent one. Subsequent
* blocks SHOULD be in the order in which they arrived at the
* receiver. These two conditions make the implementation fully
* compliant with RFC 2018.
*/
int i, j = 0, count = 0, lastpos = -1;
struct sackblk sack, firstsack, temp[MAX_SACK_BLKS];
/* First clean up current list of sacks */
for (i = 0; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (sack.start == 0 && sack.end == 0) {
count++; /* count = number of blocks to be discarded */
continue;
}
if (SEQ_LEQ(sack.end, tp->rcv_nxt)) {
tp->sackblks[i].start = tp->sackblks[i].end = 0;
count++;
} else {
temp[j].start = tp->sackblks[i].start;
temp[j++].end = tp->sackblks[i].end;
}
}
tp->rcv_numsacks -= count;
if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */
tcp_clean_sackreport(tp);
if (SEQ_LT(tp->rcv_nxt, rcv_laststart)) {
/* ==> need first sack block */
tp->sackblks[0].start = rcv_laststart;
tp->sackblks[0].end = rcv_lastend;
tp->rcv_numsacks = 1;
}
return;
}
/* Otherwise, sack blocks are already present. */
for (i = 0; i < tp->rcv_numsacks; i++)
tp->sackblks[i] = temp[i]; /* first copy back sack list */
if (SEQ_GEQ(tp->rcv_nxt, rcv_lastend))
return; /* sack list remains unchanged */
/*
* From here, segment just received should be (part of) the 1st sack.
* Go through list, possibly coalescing sack block entries.
*/
firstsack.start = rcv_laststart;
firstsack.end = rcv_lastend;
for (i = 0; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (SEQ_LT(sack.end, firstsack.start) ||
SEQ_GT(sack.start, firstsack.end))
continue; /* no overlap */
if (sack.start == firstsack.start && sack.end == firstsack.end){
/*
* identical block; delete it here since we will
* move it to the front of the list.
*/
tp->sackblks[i].start = tp->sackblks[i].end = 0;
lastpos = i; /* last posn with a zero entry */
continue;
}
if (SEQ_LEQ(sack.start, firstsack.start))
firstsack.start = sack.start; /* merge blocks */
if (SEQ_GEQ(sack.end, firstsack.end))
firstsack.end = sack.end; /* merge blocks */
tp->sackblks[i].start = tp->sackblks[i].end = 0;
lastpos = i; /* last posn with a zero entry */
}
if (lastpos != -1) { /* at least one merge */
for (i = 0, j = 1; i < tp->rcv_numsacks; i++) {
sack = tp->sackblks[i];
if (sack.start == 0 && sack.end == 0)
continue;
temp[j++] = sack;
}
tp->rcv_numsacks = j; /* including first blk (added later) */
for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */
tp->sackblks[i] = temp[i];
} else { /* no merges -- shift sacks by 1 */
if (tp->rcv_numsacks < MAX_SACK_BLKS)
tp->rcv_numsacks++;
for (i = tp->rcv_numsacks-1; i > 0; i--)
tp->sackblks[i] = tp->sackblks[i-1];
}
tp->sackblks[0] = firstsack;
return;
}
/*
* Process the TCP SACK option. tp->snd_holes is an ordered list
* of holes (oldest to newest, in terms of the sequence space).
*/
void
tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen)
{
int tmp_olen;
u_char *tmp_cp;
struct sackhole *cur, *p, *temp;
if (!tp->sack_enable)
return;
/* SACK without ACK doesn't make sense. */
if ((th->th_flags & TH_ACK) == 0)
return;
/* Make sure the ACK on this segment is in [snd_una, snd_max]. */
if (SEQ_LT(th->th_ack, tp->snd_una) ||
SEQ_GT(th->th_ack, tp->snd_max))
return;
/* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */
if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
return;
/* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */
tmp_cp = cp + 2;
tmp_olen = optlen - 2;
tcpstat.tcps_sack_rcv_opts++;
if (tp->snd_numholes < 0)
tp->snd_numholes = 0;
if (tp->t_maxseg == 0)
panic("tcp_sack_option"); /* Should never happen */
while (tmp_olen > 0) {
struct sackblk sack;
bcopy(tmp_cp, (char *) &(sack.start), sizeof(tcp_seq));
NTOHL(sack.start);
bcopy(tmp_cp + sizeof(tcp_seq),
(char *) &(sack.end), sizeof(tcp_seq));
NTOHL(sack.end);
tmp_olen -= TCPOLEN_SACK;
tmp_cp += TCPOLEN_SACK;
if (SEQ_LEQ(sack.end, sack.start))
continue; /* bad SACK fields */
if (SEQ_LEQ(sack.end, tp->snd_una))
continue; /* old block */
#if defined(TCP_SACK) && defined(TCP_FACK)
/* Updates snd_fack. */
if (SEQ_GT(sack.end, tp->snd_fack))
tp->snd_fack = sack.end;
#endif /* TCP_FACK */
if (SEQ_GT(th->th_ack, tp->snd_una)) {
if (SEQ_LT(sack.start, th->th_ack))
continue;
}
if (SEQ_GT(sack.end, tp->snd_max))
continue;
if (tp->snd_holes == NULL) { /* first hole */
tp->snd_holes = (struct sackhole *)
pool_get(&sackhl_pool, PR_NOWAIT);
if (tp->snd_holes == NULL) {
/* ENOBUFS, so ignore SACKed block for now*/
goto done;
}
cur = tp->snd_holes;
cur->start = th->th_ack;
cur->end = sack.start;
cur->rxmit = cur->start;
cur->next = NULL;
tp->snd_numholes = 1;
tp->rcv_lastsack = sack.end;
/*
* dups is at least one. If more data has been
* SACKed, it can be greater than one.
*/
cur->dups = min(tcprexmtthresh,
((sack.end - cur->end)/tp->t_maxseg));
if (cur->dups < 1)
cur->dups = 1;
continue; /* with next sack block */
}
/* Go thru list of holes: p = previous, cur = current */
p = cur = tp->snd_holes;
while (cur) {
if (SEQ_LEQ(sack.end, cur->start))
/* SACKs data before the current hole */
break; /* no use going through more holes */
if (SEQ_GEQ(sack.start, cur->end)) {
/* SACKs data beyond the current hole */
cur->dups++;
if (((sack.end - cur->end)/tp->t_maxseg) >=
tcprexmtthresh)
cur->dups = tcprexmtthresh;
p = cur;
cur = cur->next;
continue;
}
if (SEQ_LEQ(sack.start, cur->start)) {
/* Data acks at least the beginning of hole */
#if defined(TCP_SACK) && defined(TCP_FACK)
if (SEQ_GT(sack.end, cur->rxmit))
tp->retran_data -=
tcp_seq_subtract(cur->rxmit,
cur->start);
else
tp->retran_data -=
tcp_seq_subtract(sack.end,
cur->start);
#endif /* TCP_FACK */
if (SEQ_GEQ(sack.end, cur->end)) {
/* Acks entire hole, so delete hole */
if (p != cur) {
p->next = cur->next;
pool_put(&sackhl_pool, cur);
cur = p->next;
} else {
cur = cur->next;
pool_put(&sackhl_pool, p);
p = cur;
tp->snd_holes = p;
}
tp->snd_numholes--;
continue;
}
/* otherwise, move start of hole forward */
cur->start = sack.end;
cur->rxmit = SEQ_MAX(cur->rxmit, cur->start);
p = cur;
cur = cur->next;
continue;
}
/* move end of hole backward */
if (SEQ_GEQ(sack.end, cur->end)) {
#if defined(TCP_SACK) && defined(TCP_FACK)
if (SEQ_GT(cur->rxmit, sack.start))
tp->retran_data -=
tcp_seq_subtract(cur->rxmit,
sack.start);
#endif /* TCP_FACK */
cur->end = sack.start;
cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
cur->dups++;
if (((sack.end - cur->end)/tp->t_maxseg) >=
tcprexmtthresh)
cur->dups = tcprexmtthresh;
p = cur;
cur = cur->next;
continue;
}
if (SEQ_LT(cur->start, sack.start) &&
SEQ_GT(cur->end, sack.end)) {
/*
* ACKs some data in middle of a hole; need to
* split current hole
*/
temp = (struct sackhole *)
pool_get(&sackhl_pool, PR_NOWAIT);
if (temp == NULL)
goto done; /* ENOBUFS */
#if defined(TCP_SACK) && defined(TCP_FACK)
if (SEQ_GT(cur->rxmit, sack.end))
tp->retran_data -=
tcp_seq_subtract(sack.end,
sack.start);
else if (SEQ_GT(cur->rxmit, sack.start))
tp->retran_data -=
tcp_seq_subtract(cur->rxmit,
sack.start);
#endif /* TCP_FACK */
temp->next = cur->next;
temp->start = sack.end;
temp->end = cur->end;
temp->dups = cur->dups;
temp->rxmit = SEQ_MAX(cur->rxmit, temp->start);
cur->end = sack.start;
cur->rxmit = SEQ_MIN(cur->rxmit, cur->end);
cur->dups++;
if (((sack.end - cur->end)/tp->t_maxseg) >=
tcprexmtthresh)
cur->dups = tcprexmtthresh;
cur->next = temp;
p = temp;
cur = p->next;
tp->snd_numholes++;
}
}
/* At this point, p points to the last hole on the list */
if (SEQ_LT(tp->rcv_lastsack, sack.start)) {
/*
* Need to append new hole at end.
* Last hole is p (and it's not NULL).
*/
temp = (struct sackhole *)
pool_get(&sackhl_pool, PR_NOWAIT);
if (temp == NULL)
goto done; /* ENOBUFS */
temp->start = tp->rcv_lastsack;
temp->end = sack.start;
temp->dups = min(tcprexmtthresh,
((sack.end - sack.start)/tp->t_maxseg));
if (temp->dups < 1)
temp->dups = 1;
temp->rxmit = temp->start;
temp->next = 0;
p->next = temp;
tp->rcv_lastsack = sack.end;
tp->snd_numholes++;
}
}
done:
#if defined(TCP_SACK) && defined(TCP_FACK)
/*
* Update retran_data and snd_awnd. Go through the list of
* holes. Increment retran_data by (hole->rxmit - hole->start).
*/
tp->retran_data = 0;
cur = tp->snd_holes;
while (cur) {
tp->retran_data += cur->rxmit - cur->start;
cur = cur->next;
}
tp->snd_awnd = tcp_seq_subtract(tp->snd_nxt, tp->snd_fack) +
tp->retran_data;
#endif /* TCP_FACK */
return;
}
/*
* Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if
* it is completely acked; otherwise, tcp_sack_option(), called from
* tcp_dooptions(), will fix up the hole.
*/
void
tcp_del_sackholes(tp, th)
struct tcpcb *tp;
struct tcphdr *th;
{
if (tp->sack_enable && tp->t_state != TCPS_LISTEN) {
/* max because this could be an older ack just arrived */
tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ?
th->th_ack : tp->snd_una;
struct sackhole *cur = tp->snd_holes;
struct sackhole *prev;
while (cur)
if (SEQ_LEQ(cur->end, lastack)) {
prev = cur;
cur = cur->next;
pool_put(&sackhl_pool, prev);
tp->snd_numholes--;
} else if (SEQ_LT(cur->start, lastack)) {
cur->start = lastack;
if (SEQ_LT(cur->rxmit, cur->start))
cur->rxmit = cur->start;
break;
} else
break;
tp->snd_holes = cur;
}
}
/*
* Delete all receiver-side SACK information.
*/
void
tcp_clean_sackreport(tp)
struct tcpcb *tp;
{
int i;
tp->rcv_numsacks = 0;
for (i = 0; i < MAX_SACK_BLKS; i++)
tp->sackblks[i].start = tp->sackblks[i].end=0;
}
/*
* Checks for partial ack. If partial ack arrives, turn off retransmission
* timer, deflate the window, do not clear tp->t_dupacks, and return 1.
* If the ack advances at least to tp->snd_last, return 0.
*/
int
tcp_sack_partialack(tp, th)
struct tcpcb *tp;
struct tcphdr *th;
{
if (SEQ_LT(th->th_ack, tp->snd_last)) {
/* Turn off retx. timer (will start again next segment) */
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->t_rtttime = 0;
#ifndef TCP_FACK
/*
* Partial window deflation. This statement relies on the
* fact that tp->snd_una has not been updated yet. In FACK
* hold snd_cwnd constant during fast recovery.
*/
if (tp->snd_cwnd > (th->th_ack - tp->snd_una)) {
tp->snd_cwnd -= th->th_ack - tp->snd_una;
tp->snd_cwnd += tp->t_maxseg;
} else
tp->snd_cwnd = tp->t_maxseg;
#endif
return (1);
}
return (0);
}
#endif /* TCP_SACK */
/*
* Pull out of band byte out of a segment so
* it doesn't appear in the user's data queue.
* It is still reflected in the segment length for
* sequencing purposes.
*/
void
tcp_pulloutofband(so, urgent, m, off)
struct socket *so;
u_int urgent;
struct mbuf *m;
int off;
{
int cnt = off + urgent - 1;
while (cnt >= 0) {
if (m->m_len > cnt) {
char *cp = mtod(m, caddr_t) + cnt;
struct tcpcb *tp = sototcpcb(so);
tp->t_iobc = *cp;
tp->t_oobflags |= TCPOOB_HAVEDATA;
bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
m->m_len--;
return;
}
cnt -= m->m_len;
m = m->m_next;
if (m == 0)
break;
}
panic("tcp_pulloutofband");
}
/*
* Collect new round-trip time estimate
* and update averages and current timeout.
*/
void
tcp_xmit_timer(tp, rtt)
struct tcpcb *tp;
short rtt;
{
short delta;
short rttmin;
if (rtt < 0)
rtt = 0;
else if (rtt > TCP_RTT_MAX)
rtt = TCP_RTT_MAX;
tcpstat.tcps_rttupdated++;
if (tp->t_srtt != 0) {
/*
* delta is fixed point with 2 (TCP_RTT_BASE_SHIFT) bits
* after the binary point (scaled by 4), whereas
* srtt is stored as fixed point with 5 bits after the
* binary point (i.e., scaled by 32). The following magic
* is equivalent to the smoothing algorithm in rfc793 with
* an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
* point).
*/
delta = (rtt << TCP_RTT_BASE_SHIFT) -
(tp->t_srtt >> TCP_RTT_SHIFT);
if ((tp->t_srtt += delta) <= 0)
tp->t_srtt = 1 << TCP_RTT_BASE_SHIFT;
/*
* We accumulate a smoothed rtt variance (actually, a
* smoothed mean difference), then set the retransmit
* timer to smoothed rtt + 4 times the smoothed variance.
* rttvar is stored as fixed point with 4 bits after the
* binary point (scaled by 16). The following is
* equivalent to rfc793 smoothing with an alpha of .75
* (rttvar = rttvar*3/4 + |delta| / 4). This replaces
* rfc793's wired-in beta.
*/
if (delta < 0)
delta = -delta;
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
if ((tp->t_rttvar += delta) <= 0)
tp->t_rttvar = 1 << TCP_RTT_BASE_SHIFT;
} else {
/*
* No rtt measurement yet - use the unsmoothed rtt.
* Set the variance to half the rtt (so our first
* retransmit happens at 3*rtt).
*/
tp->t_srtt = (rtt + 1) << (TCP_RTT_SHIFT + TCP_RTT_BASE_SHIFT);
tp->t_rttvar = (rtt + 1) <<
(TCP_RTTVAR_SHIFT + TCP_RTT_BASE_SHIFT - 1);
}
tp->t_rtttime = 0;
tp->t_rxtshift = 0;
/*
* the retransmit should happen at rtt + 4 * rttvar.
* Because of the way we do the smoothing, srtt and rttvar
* will each average +1/2 tick of bias. When we compute
* the retransmit timer, we want 1/2 tick of rounding and
* 1 extra tick because of +-1/2 tick uncertainty in the
* firing of the timer. The bias will give us exactly the
* 1.5 tick we need. But, because the bias is
* statistical, we have to test that we don't drop below
* the minimum feasible timer (which is 2 ticks).
*/
rttmin = min(max(rtt + 2, tp->t_rttmin), TCPTV_REXMTMAX);
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX);
/*
* We received an ack for a packet that wasn't retransmitted;
* it is probably safe to discard any error indications we've
* received recently. This isn't quite right, but close enough
* for now (a route might have failed after we sent a segment,
* and the return path might not be symmetrical).
*/
tp->t_softerror = 0;
}
/*
* Determine a reasonable value for maxseg size.
* If the route is known, check route for mtu.
* If none, use an mss that can be handled on the outgoing
* interface without forcing IP to fragment; if bigger than
* an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
* to utilize large mbufs. If no route is found, route has no mtu,
* or the destination isn't local, use a default, hopefully conservative
* size (usually 512 or the default IP max size, but no more than the mtu
* of the interface), as we can't discover anything about intervening
* gateways or networks. We also initialize the congestion/slow start
* window to be a single segment if the destination isn't local.
* While looking at the routing entry, we also initialize other path-dependent
* parameters from pre-set or cached values in the routing entry.
*
* Also take into account the space needed for options that we
* send regularly. Make maxseg shorter by that amount to assure
* that we can send maxseg amount of data even when the options
* are present. Store the upper limit of the length of options plus
* data in maxopd.
*
* NOTE: offer == -1 indicates that the maxseg size changed due to
* Path MTU discovery.
*/
int
tcp_mss(tp, offer)
struct tcpcb *tp;
int offer;
{
struct rtentry *rt;
struct ifnet *ifp;
int mss, mssopt;
int iphlen;
struct inpcb *inp;
inp = tp->t_inpcb;
mssopt = mss = tcp_mssdflt;
rt = in_pcbrtentry(inp);
if (rt == NULL)
goto out;
ifp = rt->rt_ifp;
switch (tp->pf) {
#ifdef INET6
case AF_INET6:
iphlen = sizeof(struct ip6_hdr);
break;
#endif
case AF_INET:
iphlen = sizeof(struct ip);
break;
default:
/* the family does not support path MTU discovery */
goto out;
}
#ifdef RTV_MTU
/*
* if there's an mtu associated with the route and we support
* path MTU discovery for the underlying protocol family, use it.
*/
if (rt->rt_rmx.rmx_mtu) {
/*
* One may wish to lower MSS to take into account options,
* especially security-related options.
*/
if (tp->pf == AF_INET6 && rt->rt_rmx.rmx_mtu < IPV6_MMTU) {
/*
* RFC2460 section 5, last paragraph: if path MTU is
* smaller than 1280, use 1280 as packet size and
* attach fragment header.
*/
mss = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) -
sizeof(struct tcphdr);
} else
mss = rt->rt_rmx.rmx_mtu - iphlen - sizeof(struct tcphdr);
} else
#endif /* RTV_MTU */
if (!ifp)
/*
* ifp may be null and rmx_mtu may be zero in certain
* v6 cases (e.g., if ND wasn't able to resolve the
* destination host.
*/
goto out;
else if (ifp->if_flags & IFF_LOOPBACK)
mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
else if (tp->pf == AF_INET) {
if (ip_mtudisc)
mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
else if (inp && in_localaddr(inp->inp_faddr))
mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
}
#ifdef INET6
else if (tp->pf == AF_INET6) {
/*
* for IPv6, path MTU discovery is always turned on,
* or the node must use packet size <= 1280.
*/
mss = IN6_LINKMTU(ifp) - iphlen - sizeof(struct tcphdr);
}
#endif /* INET6 */
/* Calculate the value that we offer in TCPOPT_MAXSEG */
if (offer != -1) {
#ifndef INET6
mssopt = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
#else
if (tp->pf == AF_INET6)
mssopt = IN6_LINKMTU(ifp) - iphlen -
sizeof(struct tcphdr);
else
mssopt = ifp->if_mtu - iphlen - sizeof(struct tcphdr);
#endif
mssopt = max(tcp_mssdflt, mssopt);
}
out:
/*
* The current mss, t_maxseg, is initialized to the default value.
* If we compute a smaller value, reduce the current mss.
* If we compute a larger value, return it for use in sending
* a max seg size option, but don't store it for use
* unless we received an offer at least that large from peer.
*
* However, do not accept offers lower than the minimum of
* the interface MTU and 216.
*/
if (offer > 0)
tp->t_peermss = offer;
if (tp->t_peermss)
mss = min(mss, max(tp->t_peermss, 216));
/* sanity - at least max opt. space */
mss = max(mss, 64);
/*
* maxopd stores the maximum length of data AND options
* in a segment; maxseg is the amount of data in a normal
* segment. We need to store this value (maxopd) apart
* from maxseg, because now every segment carries options
* and thus we normally have somewhat less data in segments.
*/
tp->t_maxopd = mss;
if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
(tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
mss -= TCPOLEN_TSTAMP_APPA;
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE)
mss -= TCPOLEN_SIGLEN;
#endif
if (offer == -1) {
/* mss changed due to Path MTU discovery */
tp->t_flags &= ~TF_PMTUD_PEND;
tp->t_pmtud_mtu_sent = 0;
tp->t_pmtud_mss_acked = 0;
if (mss < tp->t_maxseg) {
/*
* Follow suggestion in RFC 2414 to reduce the
* congestion window by the ratio of the old
* segment size to the new segment size.
*/
tp->snd_cwnd = ulmax((tp->snd_cwnd / tp->t_maxseg) *
mss, mss);
}
} else if (tcp_do_rfc3390) {
/* increase initial window */
tp->snd_cwnd = ulmin(4 * mss, ulmax(2 * mss, 4380));
} else
tp->snd_cwnd = mss;
tp->t_maxseg = mss;
return (offer != -1 ? mssopt : mss);
}
u_int
tcp_hdrsz(struct tcpcb *tp)
{
u_int hlen;
switch (tp->pf) {
#ifdef INET6
case AF_INET6:
hlen = sizeof(struct ip6_hdr);
break;
#endif
case AF_INET:
hlen = sizeof(struct ip);
break;
default:
hlen = 0;
break;
}
hlen += sizeof(struct tcphdr);
if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
(tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
hlen += TCPOLEN_TSTAMP_APPA;
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE)
hlen += TCPOLEN_SIGLEN;
#endif
return (hlen);
}
/*
* Set connection variables based on the effective MSS.
* We are passed the TCPCB for the actual connection. If we
* are the server, we are called by the compressed state engine
* when the 3-way handshake is complete. If we are the client,
* we are called when we receive the SYN,ACK from the server.
*
* NOTE: The t_maxseg value must be initialized in the TCPCB
* before this routine is called!
*/
void
tcp_mss_update(tp)
struct tcpcb *tp;
{
int mss;
u_long bufsize;
struct rtentry *rt;
struct socket *so;
so = tp->t_inpcb->inp_socket;
mss = tp->t_maxseg;
rt = in_pcbrtentry(tp->t_inpcb);
if (rt == NULL)
return;
bufsize = so->so_snd.sb_hiwat;
if (bufsize < mss) {
mss = bufsize;
/* Update t_maxseg and t_maxopd */
tcp_mss(tp, mss);
} else {
bufsize = roundup(bufsize, mss);
if (bufsize > sb_max)
bufsize = sb_max;
(void)sbreserve(&so->so_snd, bufsize);
}
bufsize = so->so_rcv.sb_hiwat;
if (bufsize > mss) {
bufsize = roundup(bufsize, mss);
if (bufsize > sb_max)
bufsize = sb_max;
(void)sbreserve(&so->so_rcv, bufsize);
}
}
#if defined (TCP_SACK)
/*
* Checks for partial ack. If partial ack arrives, force the retransmission
* of the next unacknowledged segment, do not clear tp->t_dupacks, and return
* 1. By setting snd_nxt to ti_ack, this forces retransmission timer to
* be started again. If the ack advances at least to tp->snd_last, return 0.
*/
int
tcp_newreno(tp, th)
struct tcpcb *tp;
struct tcphdr *th;
{
if (SEQ_LT(th->th_ack, tp->snd_last)) {
/*
* snd_una has not been updated and the socket send buffer
* not yet drained of the acked data, so we have to leave
* snd_una as it was to get the correct data offset in
* tcp_output().
*/
tcp_seq onxt = tp->snd_nxt;
u_long ocwnd = tp->snd_cwnd;
TCP_TIMER_DISARM(tp, TCPT_REXMT);
tp->t_rtttime = 0;
tp->snd_nxt = th->th_ack;
/*
* Set snd_cwnd to one segment beyond acknowledged offset
* (tp->snd_una not yet updated when this function is called)
*/
tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
(void) tcp_output(tp);
tp->snd_cwnd = ocwnd;
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
/*
* Partial window deflation. Relies on fact that tp->snd_una
* not updated yet.
*/
if (tp->snd_cwnd > th->th_ack - tp->snd_una)
tp->snd_cwnd -= th->th_ack - tp->snd_una;
else
tp->snd_cwnd = 0;
tp->snd_cwnd += tp->t_maxseg;
return 1;
}
return 0;
}
#endif /* TCP_SACK */
int
tcp_mss_adv(struct ifnet *ifp, int af)
{
int mss = 0;
int iphlen;
switch (af) {
case AF_INET:
if (ifp != NULL)
mss = ifp->if_mtu;
iphlen = sizeof(struct ip);
break;
#ifdef INET6
case AF_INET6:
if (ifp != NULL)
mss = IN6_LINKMTU(ifp);
iphlen = sizeof(struct ip6_hdr);
break;
#endif
}
mss = mss - iphlen - sizeof(struct tcphdr);
return (max(mss, tcp_mssdflt));
}
/*
* TCP compressed state engine. Currently used to hold compressed
* state for SYN_RECEIVED.
*/
u_long syn_cache_count;
u_int32_t syn_hash1, syn_hash2;
#define SYN_HASH(sa, sp, dp) \
((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \
((u_int32_t)(sp)))^syn_hash2)))
#ifndef INET6
#define SYN_HASHALL(hash, src, dst) \
do { \
hash = SYN_HASH(&((struct sockaddr_in *)(src))->sin_addr, \
((struct sockaddr_in *)(src))->sin_port, \
((struct sockaddr_in *)(dst))->sin_port); \
} while (/*CONSTCOND*/ 0)
#else
#define SYN_HASH6(sa, sp, dp) \
((((sa)->s6_addr32[0] ^ (sa)->s6_addr32[3] ^ syn_hash1) * \
(((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp)))^syn_hash2)) \
& 0x7fffffff)
#define SYN_HASHALL(hash, src, dst) \
do { \
switch ((src)->sa_family) { \
case AF_INET: \
hash = SYN_HASH(&((struct sockaddr_in *)(src))->sin_addr, \
((struct sockaddr_in *)(src))->sin_port, \
((struct sockaddr_in *)(dst))->sin_port); \
break; \
case AF_INET6: \
hash = SYN_HASH6(&((struct sockaddr_in6 *)(src))->sin6_addr, \
((struct sockaddr_in6 *)(src))->sin6_port, \
((struct sockaddr_in6 *)(dst))->sin6_port); \
break; \
default: \
hash = 0; \
} \
} while (/*CONSTCOND*/0)
#endif /* INET6 */
#define SYN_CACHE_RM(sc) \
do { \
(sc)->sc_flags |= SCF_DEAD; \
TAILQ_REMOVE(&tcp_syn_cache[(sc)->sc_bucketidx].sch_bucket, \
(sc), sc_bucketq); \
(sc)->sc_tp = NULL; \
LIST_REMOVE((sc), sc_tpq); \
tcp_syn_cache[(sc)->sc_bucketidx].sch_length--; \
timeout_del(&(sc)->sc_timer); \
syn_cache_count--; \
} while (/*CONSTCOND*/0)
#define SYN_CACHE_PUT(sc) \
do { \
if ((sc)->sc_ipopts) \
(void) m_free((sc)->sc_ipopts); \
if ((sc)->sc_route4.ro_rt != NULL) \
RTFREE((sc)->sc_route4.ro_rt); \
timeout_set(&(sc)->sc_timer, syn_cache_reaper, (sc)); \
timeout_add(&(sc)->sc_timer, 0); \
} while (/*CONSTCOND*/0)
struct pool syn_cache_pool;
/*
* We don't estimate RTT with SYNs, so each packet starts with the default
* RTT and each timer step has a fixed timeout value.
*/
#define SYN_CACHE_TIMER_ARM(sc) \
do { \
TCPT_RANGESET((sc)->sc_rxtcur, \
TCPTV_SRTTDFLT * tcp_backoff[(sc)->sc_rxtshift], TCPTV_MIN, \
TCPTV_REXMTMAX); \
if (!timeout_initialized(&(sc)->sc_timer)) \
timeout_set(&(sc)->sc_timer, syn_cache_timer, (sc)); \
timeout_add(&(sc)->sc_timer, (sc)->sc_rxtcur * (hz / PR_SLOWHZ)); \
} while (/*CONSTCOND*/0)
#define SYN_CACHE_TIMESTAMP(sc) tcp_now + (sc)->sc_modulate
void
syn_cache_init()
{
int i;
/* Initialize the hash buckets. */
for (i = 0; i < tcp_syn_cache_size; i++)
TAILQ_INIT(&tcp_syn_cache[i].sch_bucket);
/* Initialize the syn cache pool. */
pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, 0, 0,
"synpl", NULL);
}
void
syn_cache_insert(sc, tp)
struct syn_cache *sc;
struct tcpcb *tp;
{
struct syn_cache_head *scp;
struct syn_cache *sc2;
int s;
/*
* If there are no entries in the hash table, reinitialize
* the hash secrets.
*/
if (syn_cache_count == 0) {
syn_hash1 = arc4random();
syn_hash2 = arc4random();
}
SYN_HASHALL(sc->sc_hash, &sc->sc_src.sa, &sc->sc_dst.sa);
sc->sc_bucketidx = sc->sc_hash % tcp_syn_cache_size;
scp = &tcp_syn_cache[sc->sc_bucketidx];
/*
* Make sure that we don't overflow the per-bucket
* limit or the total cache size limit.
*/
s = splsoftnet();
if (scp->sch_length >= tcp_syn_bucket_limit) {
tcpstat.tcps_sc_bucketoverflow++;
/*
* The bucket is full. Toss the oldest element in the
* bucket. This will be the first entry in the bucket.
*/
sc2 = TAILQ_FIRST(&scp->sch_bucket);
#ifdef DIAGNOSTIC
/*
* This should never happen; we should always find an
* entry in our bucket.
*/
if (sc2 == NULL)
panic("syn_cache_insert: bucketoverflow: impossible");
#endif
SYN_CACHE_RM(sc2);
SYN_CACHE_PUT(sc2);
} else if (syn_cache_count >= tcp_syn_cache_limit) {
struct syn_cache_head *scp2, *sce;
tcpstat.tcps_sc_overflowed++;
/*
* The cache is full. Toss the oldest entry in the
* first non-empty bucket we can find.
*
* XXX We would really like to toss the oldest
* entry in the cache, but we hope that this
* condition doesn't happen very often.
*/
scp2 = scp;
if (TAILQ_EMPTY(&scp2->sch_bucket)) {
sce = &tcp_syn_cache[tcp_syn_cache_size];
for (++scp2; scp2 != scp; scp2++) {
if (scp2 >= sce)
scp2 = &tcp_syn_cache[0];
if (! TAILQ_EMPTY(&scp2->sch_bucket))
break;
}
#ifdef DIAGNOSTIC
/*
* This should never happen; we should always find a
* non-empty bucket.
*/
if (scp2 == scp)
panic("syn_cache_insert: cacheoverflow: "
"impossible");
#endif
}
sc2 = TAILQ_FIRST(&scp2->sch_bucket);
SYN_CACHE_RM(sc2);
SYN_CACHE_PUT(sc2);
}
/*
* Initialize the entry's timer.
*/
sc->sc_rxttot = 0;
sc->sc_rxtshift = 0;
SYN_CACHE_TIMER_ARM(sc);
/* Link it from tcpcb entry */
LIST_INSERT_HEAD(&tp->t_sc, sc, sc_tpq);
/* Put it into the bucket. */
TAILQ_INSERT_TAIL(&scp->sch_bucket, sc, sc_bucketq);
scp->sch_length++;
syn_cache_count++;
tcpstat.tcps_sc_added++;
splx(s);
}
/*
* Walk the timer queues, looking for SYN,ACKs that need to be retransmitted.
* If we have retransmitted an entry the maximum number of times, expire
* that entry.
*/
void
syn_cache_timer(void *arg)
{
struct syn_cache *sc = arg;
int s;
s = splsoftnet();
if (sc->sc_flags & SCF_DEAD) {
splx(s);
return;
}
if (__predict_false(sc->sc_rxtshift == TCP_MAXRXTSHIFT)) {
/* Drop it -- too many retransmissions. */
goto dropit;
}
/*
* Compute the total amount of time this entry has
* been on a queue. If this entry has been on longer
* than the keep alive timer would allow, expire it.
*/
sc->sc_rxttot += sc->sc_rxtcur;
if (sc->sc_rxttot >= tcptv_keep_init)
goto dropit;
tcpstat.tcps_sc_retransmitted++;
(void) syn_cache_respond(sc, NULL);
/* Advance the timer back-off. */
sc->sc_rxtshift++;
SYN_CACHE_TIMER_ARM(sc);
splx(s);
return;
dropit:
tcpstat.tcps_sc_timed_out++;
SYN_CACHE_RM(sc);
SYN_CACHE_PUT(sc);
splx(s);
}
void
syn_cache_reaper(void *arg)
{
struct syn_cache *sc = arg;
int s;
s = splsoftnet();
pool_put(&syn_cache_pool, (sc));
splx(s);
return;
}
/*
* Remove syn cache created by the specified tcb entry,
* because this does not make sense to keep them
* (if there's no tcb entry, syn cache entry will never be used)
*/
void
syn_cache_cleanup(tp)
struct tcpcb *tp;
{
struct syn_cache *sc, *nsc;
int s;
s = splsoftnet();
for (sc = LIST_FIRST(&tp->t_sc); sc != NULL; sc = nsc) {
nsc = LIST_NEXT(sc, sc_tpq);
#ifdef DIAGNOSTIC
if (sc->sc_tp != tp)
panic("invalid sc_tp in syn_cache_cleanup");
#endif
SYN_CACHE_RM(sc);
SYN_CACHE_PUT(sc);
}
/* just for safety */
LIST_INIT(&tp->t_sc);
splx(s);
}
/*
* Find an entry in the syn cache.
*/
struct syn_cache *
syn_cache_lookup(src, dst, headp)
struct sockaddr *src;
struct sockaddr *dst;
struct syn_cache_head **headp;
{
struct syn_cache *sc;
struct syn_cache_head *scp;
u_int32_t hash;
int s;
SYN_HASHALL(hash, src, dst);
scp = &tcp_syn_cache[hash % tcp_syn_cache_size];
*headp = scp;
s = splsoftnet();
for (sc = TAILQ_FIRST(&scp->sch_bucket); sc != NULL;
sc = TAILQ_NEXT(sc, sc_bucketq)) {
if (sc->sc_hash != hash)
continue;
if (!bcmp(&sc->sc_src, src, src->sa_len) &&
!bcmp(&sc->sc_dst, dst, dst->sa_len)) {
splx(s);
return (sc);
}
}
splx(s);
return (NULL);
}
/*
* This function gets called when we receive an ACK for a
* socket in the LISTEN state. We look up the connection
* in the syn cache, and if its there, we pull it out of
* the cache and turn it into a full-blown connection in
* the SYN-RECEIVED state.
*
* The return values may not be immediately obvious, and their effects
* can be subtle, so here they are:
*
* NULL SYN was not found in cache; caller should drop the
* packet and send an RST.
*
* -1 We were unable to create the new connection, and are
* aborting it. An ACK,RST is being sent to the peer
* (unless we got screwey sequence numbners; see below),
* because the 3-way handshake has been completed. Caller
* should not free the mbuf, since we may be using it. If
* we are not, we will free it.
*
* Otherwise, the return value is a pointer to the new socket
* associated with the connection.
*/
struct socket *
syn_cache_get(src, dst, th, hlen, tlen, so, m)
struct sockaddr *src;
struct sockaddr *dst;
struct tcphdr *th;
unsigned int hlen, tlen;
struct socket *so;
struct mbuf *m;
{
struct syn_cache *sc;
struct syn_cache_head *scp;
struct inpcb *inp = NULL;
struct tcpcb *tp = 0;
struct mbuf *am;
int s;
struct socket *oso;
s = splsoftnet();
if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) {
splx(s);
return (NULL);
}
/*
* Verify the sequence and ack numbers. Try getting the correct
* response again.
*/
if ((th->th_ack != sc->sc_iss + 1) ||
SEQ_LEQ(th->th_seq, sc->sc_irs) ||
SEQ_GT(th->th_seq, sc->sc_irs + 1 + sc->sc_win)) {
(void) syn_cache_respond(sc, m);
splx(s);
return ((struct socket *)(-1));
}
/* Remove this cache entry */
SYN_CACHE_RM(sc);
splx(s);
/*
* Ok, create the full blown connection, and set things up
* as they would have been set up if we had created the
* connection when the SYN arrived. If we can't create
* the connection, abort it.
*/
oso = so;
so = sonewconn(so, SS_ISCONNECTED);
if (so == NULL)
goto resetandabort;
inp = sotoinpcb(oso);
#ifdef IPSEC
/*
* We need to copy the required security levels
* from the old pcb. Ditto for any other
* IPsec-related information.
*/
{
struct inpcb *newinp = (struct inpcb *)so->so_pcb;
bcopy(inp->inp_seclevel, newinp->inp_seclevel,
sizeof(inp->inp_seclevel));
newinp->inp_secrequire = inp->inp_secrequire;
if (inp->inp_ipo != NULL) {
newinp->inp_ipo = inp->inp_ipo;
inp->inp_ipo->ipo_ref_count++;
}
if (inp->inp_ipsec_remotecred != NULL) {
newinp->inp_ipsec_remotecred = inp->inp_ipsec_remotecred;
inp->inp_ipsec_remotecred->ref_count++;
}
if (inp->inp_ipsec_remoteauth != NULL) {
newinp->inp_ipsec_remoteauth
= inp->inp_ipsec_remoteauth;
inp->inp_ipsec_remoteauth->ref_count++;
}
}
#endif /* IPSEC */
#ifdef INET6
/*
* inp still has the OLD in_pcb stuff, set the
* v6-related flags on the new guy, too.
*/
{
int flags = inp->inp_flags;
struct inpcb *oldinpcb = inp;
inp = (struct inpcb *)so->so_pcb;
inp->inp_flags |= (flags & INP_IPV6);
if ((inp->inp_flags & INP_IPV6) != 0) {
inp->inp_ipv6.ip6_hlim =
oldinpcb->inp_ipv6.ip6_hlim;
}
}
#else /* INET6 */
inp = (struct inpcb *)so->so_pcb;
#endif /* INET6 */
inp->inp_lport = th->th_dport;
switch (src->sa_family) {
#ifdef INET6
case AF_INET6:
inp->inp_laddr6 = ((struct sockaddr_in6 *)dst)->sin6_addr;
break;
#endif /* INET6 */
case AF_INET:
inp->inp_laddr = ((struct sockaddr_in *)dst)->sin_addr;
inp->inp_options = ip_srcroute();
if (inp->inp_options == NULL) {
inp->inp_options = sc->sc_ipopts;
sc->sc_ipopts = NULL;
}
break;
}
in_pcbrehash(inp);
/*
* Give the new socket our cached route reference.
*/
if (src->sa_family == AF_INET)
inp->inp_route = sc->sc_route4; /* struct assignment */
#ifdef INET6
else
inp->inp_route6 = sc->sc_route6;
#endif
sc->sc_route4.ro_rt = NULL;
am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */
if (am == NULL)
goto resetandabort;
am->m_len = src->sa_len;
bcopy(src, mtod(am, caddr_t), src->sa_len);
switch (src->sa_family) {
case AF_INET:
/* drop IPv4 packet to AF_INET6 socket */
if (inp->inp_flags & INP_IPV6) {
(void) m_free(am);
goto resetandabort;
}
if (in_pcbconnect(inp, am)) {
(void) m_free(am);
goto resetandabort;
}
break;
#ifdef INET6
case AF_INET6:
if (in6_pcbconnect(inp, am)) {
(void) m_free(am);
goto resetandabort;
}
break;
#endif
}
(void) m_free(am);
tp = intotcpcb(inp);
tp->t_flags = sototcpcb(oso)->t_flags & TF_NODELAY;
if (sc->sc_request_r_scale != 15) {
tp->requested_s_scale = sc->sc_requested_s_scale;
tp->request_r_scale = sc->sc_request_r_scale;
tp->snd_scale = sc->sc_requested_s_scale;
tp->rcv_scale = sc->sc_request_r_scale;
tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE;
}
if (sc->sc_flags & SCF_TIMESTAMP)
tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP;
tp->t_template = tcp_template(tp);
if (tp->t_template == 0) {
tp = tcp_drop(tp, ENOBUFS); /* destroys socket */
so = NULL;
m_freem(m);
goto abort;
}
#ifdef TCP_SACK
tp->sack_enable = sc->sc_flags & SCF_SACK_PERMIT;
#endif
tp->ts_modulate = sc->sc_modulate;
tp->iss = sc->sc_iss;
tp->irs = sc->sc_irs;
tcp_sendseqinit(tp);
#if defined (TCP_SACK) || defined(TCP_ECN)
tp->snd_last = tp->snd_una;
#endif /* TCP_SACK */
#if defined(TCP_SACK) && defined(TCP_FACK)
tp->snd_fack = tp->snd_una;
tp->retran_data = 0;
tp->snd_awnd = 0;
#endif /* TCP_FACK */
#ifdef TCP_ECN
if (sc->sc_flags & SCF_ECN_PERMIT) {
tp->t_flags |= TF_ECN_PERMIT;
tcpstat.tcps_ecn_accepts++;
}
#endif
#ifdef TCP_SACK
if (sc->sc_flags & SCF_SACK_PERMIT)
tp->t_flags |= TF_SACK_PERMIT;
#endif
#ifdef TCP_SIGNATURE
if (sc->sc_flags & SCF_SIGNATURE)
tp->t_flags |= TF_SIGNATURE;
#endif
tcp_rcvseqinit(tp);
tp->t_state = TCPS_SYN_RECEIVED;
tp->t_rcvtime = tcp_now;
TCP_TIMER_ARM(tp, TCPT_KEEP, tcptv_keep_init);
tcpstat.tcps_accepts++;
tcp_mss(tp, sc->sc_peermaxseg); /* sets t_maxseg */
if (sc->sc_peermaxseg)
tcp_mss_update(tp);
/* Reset initial window to 1 segment for retransmit */
if (sc->sc_rxtshift > 0)
tp->snd_cwnd = tp->t_maxseg;
tp->snd_wl1 = sc->sc_irs;
tp->rcv_up = sc->sc_irs + 1;
/*
* This is what whould have happened in tcp_output() when
* the SYN,ACK was sent.
*/
tp->snd_up = tp->snd_una;
tp->snd_max = tp->snd_nxt = tp->iss+1;
TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur);
if (sc->sc_win > 0 && SEQ_GT(tp->rcv_nxt + sc->sc_win, tp->rcv_adv))
tp->rcv_adv = tp->rcv_nxt + sc->sc_win;
tp->last_ack_sent = tp->rcv_nxt;
tcpstat.tcps_sc_completed++;
SYN_CACHE_PUT(sc);
return (so);
resetandabort:
tcp_respond(NULL, mtod(m, caddr_t), m, (tcp_seq)0, th->th_ack, TH_RST);
abort:
if (so != NULL)
(void) soabort(so);
SYN_CACHE_PUT(sc);
tcpstat.tcps_sc_aborted++;
return ((struct socket *)(-1));
}
/*
* This function is called when we get a RST for a
* non-existent connection, so that we can see if the
* connection is in the syn cache. If it is, zap it.
*/
void
syn_cache_reset(src, dst, th)
struct sockaddr *src;
struct sockaddr *dst;
struct tcphdr *th;
{
struct syn_cache *sc;
struct syn_cache_head *scp;
int s = splsoftnet();
if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) {
splx(s);
return;
}
if (SEQ_LT(th->th_seq, sc->sc_irs) ||
SEQ_GT(th->th_seq, sc->sc_irs+1)) {
splx(s);
return;
}
SYN_CACHE_RM(sc);
splx(s);
tcpstat.tcps_sc_reset++;
SYN_CACHE_PUT(sc);
}
void
syn_cache_unreach(src, dst, th)
struct sockaddr *src;
struct sockaddr *dst;
struct tcphdr *th;
{
struct syn_cache *sc;
struct syn_cache_head *scp;
int s;
s = splsoftnet();
if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) {
splx(s);
return;
}
/* If the sequence number != sc_iss, then it's a bogus ICMP msg */
if (ntohl (th->th_seq) != sc->sc_iss) {
splx(s);
return;
}
/*
* If we've retransmitted 3 times and this is our second error,
* we remove the entry. Otherwise, we allow it to continue on.
* This prevents us from incorrectly nuking an entry during a
* spurious network outage.
*
* See tcp_notify().
*/
if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtshift < 3) {
sc->sc_flags |= SCF_UNREACH;
splx(s);
return;
}
SYN_CACHE_RM(sc);
splx(s);
tcpstat.tcps_sc_unreach++;
SYN_CACHE_PUT(sc);
}
/*
* Given a LISTEN socket and an inbound SYN request, add
* this to the syn cache, and send back a segment:
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
* to the source.
*
* IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN.
* Doing so would require that we hold onto the data and deliver it
* to the application. However, if we are the target of a SYN-flood
* DoS attack, an attacker could send data which would eventually
* consume all available buffer space if it were ACKed. By not ACKing
* the data, we avoid this DoS scenario.
*/
int
syn_cache_add(src, dst, th, iphlen, so, m, optp, optlen, oi, issp)
struct sockaddr *src;
struct sockaddr *dst;
struct tcphdr *th;
unsigned int iphlen;
struct socket *so;
struct mbuf *m;
u_char *optp;
int optlen;
struct tcp_opt_info *oi;
tcp_seq *issp;
{
struct tcpcb tb, *tp;
long win;
struct syn_cache *sc;
struct syn_cache_head *scp;
struct mbuf *ipopts;
tp = sototcpcb(so);
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
*
* Note this check is performed in tcp_input() very early on.
*/
/*
* Initialize some local state.
*/
win = sbspace(&so->so_rcv);
if (win > TCP_MAXWIN)
win = TCP_MAXWIN;
#ifdef TCP_SIGNATURE
if (optp || (tp->t_flags & TF_SIGNATURE)) {
#else
if (optp) {
#endif
tb.pf = tp->pf;
#ifdef TCP_SACK
tb.sack_enable = tp->sack_enable;
#endif
tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0;
#ifdef TCP_SIGNATURE
if (tp->t_flags & TF_SIGNATURE)
tb.t_flags |= TF_SIGNATURE;
#endif
tb.t_state = TCPS_LISTEN;
if (tcp_dooptions(&tb, optp, optlen, th, m, iphlen, oi))
return (0);
} else
tb.t_flags = 0;
switch (src->sa_family) {
#ifdef INET
case AF_INET:
/*
* Remember the IP options, if any.
*/
ipopts = ip_srcroute();
break;
#endif
default:
ipopts = NULL;
}
/*
* See if we already have an entry for this connection.
* If we do, resend the SYN,ACK. We do not count this
* as a retransmission (XXX though maybe we should).
*/
if ((sc = syn_cache_lookup(src, dst, &scp)) != NULL) {
tcpstat.tcps_sc_dupesyn++;
if (ipopts) {
/*
* If we were remembering a previous source route,
* forget it and use the new one we've been given.
*/
if (sc->sc_ipopts)
(void) m_free(sc->sc_ipopts);
sc->sc_ipopts = ipopts;
}
sc->sc_timestamp = tb.ts_recent;
if (syn_cache_respond(sc, m) == 0) {
tcpstat.tcps_sndacks++;
tcpstat.tcps_sndtotal++;
}
return (1);
}
sc = pool_get(&syn_cache_pool, PR_NOWAIT);
if (sc == NULL) {
if (ipopts)
(void) m_free(ipopts);
return (0);
}
/*
* Fill in the cache, and put the necessary IP and TCP
* options into the reply.
*/
bzero(sc, sizeof(struct syn_cache));
bzero(&sc->sc_timer, sizeof(sc->sc_timer));
bcopy(src, &sc->sc_src, src->sa_len);
bcopy(dst, &sc->sc_dst, dst->sa_len);
sc->sc_flags = 0;
sc->sc_ipopts = ipopts;
sc->sc_irs = th->th_seq;
#ifdef TCP_COMPAT_42
tcp_iss += TCP_ISSINCR/2;
sc->sc_iss = tcp_iss;
#else
sc->sc_iss = issp ? *issp : arc4random();
#endif
sc->sc_peermaxseg = oi->maxseg;
sc->sc_ourmaxseg = tcp_mss_adv(m->m_flags & M_PKTHDR ?
m->m_pkthdr.rcvif : NULL, sc->sc_src.sa.sa_family);
sc->sc_win = win;
sc->sc_timestamp = tb.ts_recent;
if ((tb.t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP)) ==
(TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
sc->sc_flags |= SCF_TIMESTAMP;
sc->sc_modulate = arc4random();
}
if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
sc->sc_requested_s_scale = tb.requested_s_scale;
sc->sc_request_r_scale = 0;
while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT &&
TCP_MAXWIN << sc->sc_request_r_scale <
so->so_rcv.sb_hiwat)
sc->sc_request_r_scale++;
} else {
sc->sc_requested_s_scale = 15;
sc->sc_request_r_scale = 15;
}
#ifdef TCP_ECN
/*
* if both ECE and CWR flag bits are set, peer is ECN capable.
*/
if (tcp_do_ecn &&
(th->th_flags & (TH_ECE|TH_CWR)) == (TH_ECE|TH_CWR))
sc->sc_flags |= SCF_ECN_PERMIT;
#endif
#ifdef TCP_SACK
/*
* Set SCF_SACK_PERMIT if peer did send a SACK_PERMITTED option
* (i.e., if tcp_dooptions() did set TF_SACK_PERMIT).
*/
if (tb.sack_enable && (tb.t_flags & TF_SACK_PERMIT))
sc->sc_flags |= SCF_SACK_PERMIT;
#endif
#ifdef TCP_SIGNATURE
if (tb.t_flags & TF_SIGNATURE)
sc->sc_flags |= SCF_SIGNATURE;
#endif
sc->sc_tp = tp;
if (syn_cache_respond(sc, m) == 0) {
syn_cache_insert(sc, tp);
tcpstat.tcps_sndacks++;
tcpstat.tcps_sndtotal++;
} else {
SYN_CACHE_PUT(sc);
tcpstat.tcps_sc_dropped++;
}
return (1);
}
int
syn_cache_respond(sc, m)
struct syn_cache *sc;
struct mbuf *m;
{
struct route *ro;
u_int8_t *optp;
int optlen, error;
u_int16_t tlen;
struct ip *ip = NULL;
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
#endif
struct tcphdr *th;
u_int hlen;
struct inpcb *inp;
switch (sc->sc_src.sa.sa_family) {
case AF_INET:
hlen = sizeof(struct ip);
ro = &sc->sc_route4;
break;
#ifdef INET6
case AF_INET6:
hlen = sizeof(struct ip6_hdr);
ro = (struct route *)&sc->sc_route6;
break;
#endif
default:
if (m)
m_freem(m);
return (EAFNOSUPPORT);
}
/* Compute the size of the TCP options. */
optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) +
#ifdef TCP_SACK
((sc->sc_flags & SCF_SACK_PERMIT) ? 4 : 0) +
#endif
#ifdef TCP_SIGNATURE
((sc->sc_flags & SCF_SIGNATURE) ? TCPOLEN_SIGLEN : 0) +
#endif
((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0);
tlen = hlen + sizeof(struct tcphdr) + optlen;
/*
* Create the IP+TCP header from scratch.
*/
if (m)
m_freem(m);
#ifdef DIAGNOSTIC
if (max_linkhdr + tlen > MCLBYTES)
return (ENOBUFS);
#endif
MGETHDR(m, M_DONTWAIT, MT_DATA);
if (m && max_linkhdr + tlen > MHLEN) {
MCLGET(m, M_DONTWAIT);
if ((m->m_flags & M_EXT) == 0) {
m_freem(m);
m = NULL;
}
}
if (m == NULL)
return (ENOBUFS);
/* Fixup the mbuf. */
m->m_data += max_linkhdr;
m->m_len = m->m_pkthdr.len = tlen;
m->m_pkthdr.rcvif = NULL;
memset(mtod(m, u_char *), 0, tlen);
switch (sc->sc_src.sa.sa_family) {
case AF_INET:
ip = mtod(m, struct ip *);
ip->ip_dst = sc->sc_src.sin.sin_addr;
ip->ip_src = sc->sc_dst.sin.sin_addr;
ip->ip_p = IPPROTO_TCP;
th = (struct tcphdr *)(ip + 1);
th->th_dport = sc->sc_src.sin.sin_port;
th->th_sport = sc->sc_dst.sin.sin_port;
break;
#ifdef INET6
case AF_INET6:
ip6 = mtod(m, struct ip6_hdr *);
ip6->ip6_dst = sc->sc_src.sin6.sin6_addr;
ip6->ip6_src = sc->sc_dst.sin6.sin6_addr;
ip6->ip6_nxt = IPPROTO_TCP;
/* ip6_plen will be updated in ip6_output() */
th = (struct tcphdr *)(ip6 + 1);
th->th_dport = sc->sc_src.sin6.sin6_port;
th->th_sport = sc->sc_dst.sin6.sin6_port;
break;
#endif
default:
th = NULL;
}
th->th_seq = htonl(sc->sc_iss);
th->th_ack = htonl(sc->sc_irs + 1);
th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
th->th_flags = TH_SYN|TH_ACK;
#ifdef TCP_ECN
/* Set ECE for SYN-ACK if peer supports ECN. */
if (tcp_do_ecn && (sc->sc_flags & SCF_ECN_PERMIT))
th->th_flags |= TH_ECE;
#endif
th->th_win = htons(sc->sc_win);
/* th_sum already 0 */
/* th_urp already 0 */
/* Tack on the TCP options. */
optp = (u_int8_t *)(th + 1);
*optp++ = TCPOPT_MAXSEG;
*optp++ = 4;
*optp++ = (sc->sc_ourmaxseg >> 8) & 0xff;
*optp++ = sc->sc_ourmaxseg & 0xff;
#ifdef TCP_SACK
/* Include SACK_PERMIT_HDR option if peer has already done so. */
if (sc->sc_flags & SCF_SACK_PERMIT) {
*((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMIT_HDR);
optp += 4;
}
#endif
if (sc->sc_request_r_scale != 15) {
*((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 |
TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
sc->sc_request_r_scale);
optp += 4;
}
if (sc->sc_flags & SCF_TIMESTAMP) {
u_int32_t *lp = (u_int32_t *)(optp);
/* Form timestamp option as shown in appendix A of RFC 1323. */
*lp++ = htonl(TCPOPT_TSTAMP_HDR);
*lp++ = htonl(SYN_CACHE_TIMESTAMP(sc));
*lp = htonl(sc->sc_timestamp);
optp += TCPOLEN_TSTAMP_APPA;
}
#ifdef TCP_SIGNATURE
if (sc->sc_flags & SCF_SIGNATURE) {
union sockaddr_union src, dst;
struct tdb *tdb;
bzero(&src, sizeof(union sockaddr_union));
bzero(&dst, sizeof(union sockaddr_union));
src.sa.sa_len = sc->sc_src.sa.sa_len;
src.sa.sa_family = sc->sc_src.sa.sa_family;
dst.sa.sa_len = sc->sc_dst.sa.sa_len;
dst.sa.sa_family = sc->sc_dst.sa.sa_family;
switch (sc->sc_src.sa.sa_family) {
case 0: /*default to PF_INET*/
#ifdef INET
case AF_INET:
src.sin.sin_addr = mtod(m, struct ip *)->ip_src;
dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst;
break;
#endif /* INET */
#ifdef INET6
case AF_INET6:
src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src;
dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst;
break;
#endif /* INET6 */
}
tdb = gettdbbysrcdst(0, &src, &dst, IPPROTO_TCP);
if (tdb == NULL) {
if (m)
m_freem(m);
return (EPERM);
}
/* Send signature option */
*(optp++) = TCPOPT_SIGNATURE;
*(optp++) = TCPOLEN_SIGNATURE;
if (tcp_signature(tdb, sc->sc_src.sa.sa_family, m, th,
hlen, 0, optp) < 0) {
if (m)
m_freem(m);
return (EINVAL);
}
optp += 16;
/* Pad options list to the next 32 bit boundary and
* terminate it.
*/
*optp++ = TCPOPT_NOP;
*optp++ = TCPOPT_EOL;
}
#endif /* TCP_SIGNATURE */
/* Compute the packet's checksum. */
switch (sc->sc_src.sa.sa_family) {
case AF_INET:
ip->ip_len = htons(tlen - hlen);
th->th_sum = 0;
th->th_sum = in_cksum(m, tlen);
break;
#ifdef INET6
case AF_INET6:
ip6->ip6_plen = htons(tlen - hlen);
th->th_sum = 0;
th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen);
break;
#endif
}
/* use IPsec policy and ttl from listening socket, on SYN ACK */
inp = sc->sc_tp ? sc->sc_tp->t_inpcb : NULL;
/*
* Fill in some straggling IP bits. Note the stack expects
* ip_len to be in host order, for convenience.
*/
switch (sc->sc_src.sa.sa_family) {
#ifdef INET
case AF_INET:
ip->ip_len = htons(tlen);
ip->ip_ttl = inp ? inp->inp_ip.ip_ttl : ip_defttl;
/* XXX tos? */
break;
#endif
#ifdef INET6
case AF_INET6:
ip6->ip6_vfc &= ~IPV6_VERSION_MASK;
ip6->ip6_vfc |= IPV6_VERSION;
ip6->ip6_plen = htons(tlen - hlen);
/* ip6_hlim will be initialized afterwards */
/* leave flowlabel = 0, it is legal and require no state mgmt */
break;
#endif
}
switch (sc->sc_src.sa.sa_family) {
#ifdef INET
case AF_INET:
error = ip_output(m, sc->sc_ipopts, ro,
(ip_mtudisc ? IP_MTUDISC : 0),
(struct ip_moptions *)NULL, inp);
break;
#endif
#ifdef INET6
case AF_INET6:
ip6->ip6_hlim = in6_selecthlim(NULL,
ro->ro_rt ? ro->ro_rt->rt_ifp : NULL);
error = ip6_output(m, NULL /*XXX*/, (struct route_in6 *)ro, 0,
(struct ip6_moptions *)0, NULL, NULL);
break;
#endif
default:
error = EAFNOSUPPORT;
break;
}
return (error);
}
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