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freebsd-dev/sys/netinet/tcp_input.c
Robert Watson 66f80e90ef Wrap use of rw_try_upgrade() on pcbinfo with macro INP_INFO_TRY_UPGRADE() 
to match other pcbinfo locking macros.

MFC after:	1 week
2010-03-06 21:24:11 +00:00

3441 lines
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/*-
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
* 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.
* 4. 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.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_ipfw.h" /* for ipfw_fwd */
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_tcpdebug.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/proc.h> /* for proc0 declaration */
#include <sys/protosw.h>
#include <sys/signalvar.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
#include <vm/uma.h>
#include <net/if.h>
#include <net/route.h>
#include <net/vnet.h>
#define TCPSTATES /* for logging */
#include <netinet/in.h>
#include <netinet/in_pcb.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h> /* required for icmp_var.h */
#include <netinet/icmp_var.h> /* for ICMP_BANDLIM */
#include <netinet/ip_var.h>
#include <netinet/ip_options.h>
#include <netinet/ip6.h>
#include <netinet/icmp6.h>
#include <netinet6/in6_pcb.h>
#include <netinet6/ip6_var.h>
#include <netinet6/nd6.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 <netinet6/tcp6_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_syncache.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif /* TCPDEBUG */
#ifdef IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#endif /*IPSEC*/
#include <machine/in_cksum.h>
#include <security/mac/mac_framework.h>
static const int tcprexmtthresh = 3;
VNET_DEFINE(struct tcpstat, tcpstat);
VNET_DEFINE(int, blackhole);
VNET_DEFINE(int, tcp_delack_enabled);
VNET_DEFINE(int, drop_synfin);
VNET_DEFINE(int, tcp_do_rfc3042);
VNET_DEFINE(int, tcp_do_rfc3390);
VNET_DEFINE(int, tcp_do_ecn);
VNET_DEFINE(int, tcp_ecn_maxretries);
VNET_DEFINE(int, tcp_insecure_rst);
VNET_DEFINE(int, tcp_do_autorcvbuf);
VNET_DEFINE(int, tcp_autorcvbuf_inc);
VNET_DEFINE(int, tcp_autorcvbuf_max);
VNET_DEFINE(int, tcp_do_rfc3465);
VNET_DEFINE(int, tcp_abc_l_var);
SYSCTL_VNET_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
&VNET_NAME(tcpstat), tcpstat,
"TCP statistics (struct tcpstat, netinet/tcp_var.h)");
int tcp_log_in_vain = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
&tcp_log_in_vain, 0,
"Log all incoming TCP segments to closed ports");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
&VNET_NAME(blackhole), 0,
"Do not send RST on segments to closed ports");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
&VNET_NAME(tcp_delack_enabled), 0,
"Delay ACK to try and piggyback it onto a data packet");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
&VNET_NAME(drop_synfin), 0,
"Drop TCP packets with SYN+FIN set");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
&VNET_NAME(tcp_do_rfc3042), 0,
"Enable RFC 3042 (Limited Transmit)");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
&VNET_NAME(tcp_do_rfc3390), 0,
"Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW,
&VNET_NAME(tcp_do_rfc3465), 0,
"Enable RFC 3465 (Appropriate Byte Counting)");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW,
&VNET_NAME(tcp_abc_l_var), 2,
"Cap the max cwnd increment during slow-start to this number of segments");
SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW,
&VNET_NAME(tcp_do_ecn), 0,
"TCP ECN support");
SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW,
&VNET_NAME(tcp_ecn_maxretries), 0,
"Max retries before giving up on ECN");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
&VNET_NAME(tcp_insecure_rst), 0,
"Follow the old (insecure) criteria for accepting RST packets");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW,
&VNET_NAME(tcp_do_autorcvbuf), 0,
"Enable automatic receive buffer sizing");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW,
&VNET_NAME(tcp_autorcvbuf_inc), 0,
"Incrementor step size of automatic receive buffer");
SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW,
&VNET_NAME(tcp_autorcvbuf_max), 0,
"Max size of automatic receive buffer");
int tcp_read_locking = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, read_locking, CTLFLAG_RW,
&tcp_read_locking, 0, "Enable read locking strategy");
VNET_DEFINE(struct inpcbhead, tcb);
VNET_DEFINE(struct inpcbinfo, tcbinfo);
#define tcb6 tcb /* for KAME src sync over BSD*'s */
static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
static void tcp_do_segment(struct mbuf *, struct tcphdr *,
struct socket *, struct tcpcb *, int, int, uint8_t,
int);
static void tcp_dropwithreset(struct mbuf *, struct tcphdr *,
struct tcpcb *, int, int);
static void tcp_pulloutofband(struct socket *,
struct tcphdr *, struct mbuf *, int);
static void tcp_xmit_timer(struct tcpcb *, int);
static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
static void inline
tcp_congestion_exp(struct tcpcb *);
/*
* Kernel module interface for updating tcpstat. The argument is an index
* into tcpstat treated as an array of u_long. While this encodes the
* general layout of tcpstat into the caller, it doesn't encode its location,
* so that future changes to add, for example, per-CPU stats support won't
* cause binary compatibility problems for kernel modules.
*/
void
kmod_tcpstat_inc(int statnum)
{
(*((u_long *)&V_tcpstat + statnum))++;
}
static void inline
tcp_congestion_exp(struct tcpcb *tp)
{
u_int win;
win = min(tp->snd_wnd, tp->snd_cwnd) /
2 / tp->t_maxseg;
if (win < 2)
win = 2;
tp->snd_ssthresh = win * tp->t_maxseg;
ENTER_FASTRECOVERY(tp);
tp->snd_recover = tp->snd_max;
if (tp->t_flags & TF_ECN_PERMIT)
tp->t_flags |= TF_ECN_SND_CWR;
}
/* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */
#ifdef INET6
#define ND6_HINT(tp) \
do { \
if ((tp) && (tp)->t_inpcb && \
((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \
nd6_nud_hint(NULL, NULL, 0); \
} while (0)
#else
#define ND6_HINT(tp)
#endif
/*
* Indicate whether this ack should be delayed. We can delay the ack if
* - there is no delayed ack timer in progress and
* - our last ack wasn't a 0-sized window. We never want to delay
* the ack that opens up a 0-sized window and
* - delayed acks are enabled or
* - this is a half-synchronized T/TCP connection.
*/
#define DELAY_ACK(tp) \
((!tcp_timer_active(tp, TT_DELACK) && \
(tp->t_flags & TF_RXWIN0SENT) == 0) && \
(V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
/*
* TCP input handling is split into multiple parts:
* tcp6_input is a thin wrapper around tcp_input for the extended
* ip6_protox[] call format in ip6_input
* tcp_input handles primary segment validation, inpcb lookup and
* SYN processing on listen sockets
* tcp_do_segment processes the ACK and text of the segment for
* establishing, established and closing connections
*/
#ifdef INET6
int
tcp6_input(struct mbuf **mp, int *offp, int proto)
{
struct mbuf *m = *mp;
struct in6_ifaddr *ia6;
IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
/*
* draft-itojun-ipv6-tcp-to-anycast
* better place to put this in?
*/
ia6 = ip6_getdstifaddr(m);
if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
struct ip6_hdr *ip6;
ifa_free(&ia6->ia_ifa);
ip6 = mtod(m, struct ip6_hdr *);
icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
(caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
return IPPROTO_DONE;
}
tcp_input(m, *offp);
return IPPROTO_DONE;
}
#endif
void
tcp_input(struct mbuf *m, int off0)
{
struct tcphdr *th;
struct ip *ip = NULL;
struct ipovly *ipov;
struct inpcb *inp = NULL;
struct tcpcb *tp = NULL;
struct socket *so = NULL;
u_char *optp = NULL;
int optlen = 0;
int len, tlen, off;
int drop_hdrlen;
int thflags;
int rstreason = 0; /* For badport_bandlim accounting purposes */
uint8_t iptos;
#ifdef IPFIREWALL_FORWARD
struct m_tag *fwd_tag;
#endif
#ifdef INET6
struct ip6_hdr *ip6 = NULL;
int isipv6;
#else
const void *ip6 = NULL;
const int isipv6 = 0;
#endif
struct tcpopt to; /* options in this segment */
char *s = NULL; /* address and port logging */
int ti_locked;
#define TI_UNLOCKED 1
#define TI_RLOCKED 2
#define TI_WLOCKED 3
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
#ifdef INET6
isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
#endif
to.to_flags = 0;
TCPSTAT_INC(tcps_rcvtotal);
if (isipv6) {
#ifdef INET6
/* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
ip6 = mtod(m, struct ip6_hdr *);
tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) {
TCPSTAT_INC(tcps_rcvbadsum);
goto drop;
}
th = (struct tcphdr *)((caddr_t)ip6 + off0);
/*
* 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;
}
#else
th = NULL; /* XXX: Avoid compiler warning. */
#endif
} else {
/*
* Get IP and TCP header together in first mbuf.
* Note: IP leaves IP header in first mbuf.
*/
if (off0 > sizeof (struct ip)) {
ip_stripoptions(m, (struct mbuf *)0);
off0 = sizeof(struct ip);
}
if (m->m_len < sizeof (struct tcpiphdr)) {
if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
== NULL) {
TCPSTAT_INC(tcps_rcvshort);
return;
}
}
ip = mtod(m, struct ip *);
ipov = (struct ipovly *)ip;
th = (struct tcphdr *)((caddr_t)ip + off0);
tlen = ip->ip_len;
if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
th->th_sum = m->m_pkthdr.csum_data;
else
th->th_sum = in_pseudo(ip->ip_src.s_addr,
ip->ip_dst.s_addr,
htonl(m->m_pkthdr.csum_data +
ip->ip_len +
IPPROTO_TCP));
th->th_sum ^= 0xffff;
#ifdef TCPDEBUG
ipov->ih_len = (u_short)tlen;
ipov->ih_len = htons(ipov->ih_len);
#endif
} else {
/*
* Checksum extended TCP header and data.
*/
len = sizeof (struct ip) + tlen;
bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
ipov->ih_len = (u_short)tlen;
ipov->ih_len = htons(ipov->ih_len);
th->th_sum = in_cksum(m, len);
}
if (th->th_sum) {
TCPSTAT_INC(tcps_rcvbadsum);
goto drop;
}
/* Re-initialization for later version check */
ip->ip_v = IPVERSION;
}
#ifdef INET6
if (isipv6)
iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
else
#endif
iptos = ip->ip_tos;
/*
* 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_INC(tcps_rcvbadoff);
goto drop;
}
tlen -= off; /* tlen is used instead of ti->ti_len */
if (off > sizeof (struct tcphdr)) {
if (isipv6) {
#ifdef INET6
IP6_EXTHDR_CHECK(m, off0, off, );
ip6 = mtod(m, struct ip6_hdr *);
th = (struct tcphdr *)((caddr_t)ip6 + off0);
#endif
} else {
if (m->m_len < sizeof(struct ip) + off) {
if ((m = m_pullup(m, sizeof (struct ip) + off))
== NULL) {
TCPSTAT_INC(tcps_rcvshort);
return;
}
ip = mtod(m, struct ip *);
ipov = (struct ipovly *)ip;
th = (struct tcphdr *)((caddr_t)ip + off0);
}
}
optlen = off - sizeof (struct tcphdr);
optp = (u_char *)(th + 1);
}
thflags = th->th_flags;
/*
* Convert TCP protocol specific fields to host format.
*/
th->th_seq = ntohl(th->th_seq);
th->th_ack = ntohl(th->th_ack);
th->th_win = ntohs(th->th_win);
th->th_urp = ntohs(th->th_urp);
/*
* Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
*/
drop_hdrlen = off0 + off;
/*
* Locate pcb for segment, which requires a lock on tcbinfo.
* Optimisticaly acquire a global read lock rather than a write lock
* unless header flags necessarily imply a state change. There are
* two cases where we might discover later we need a write lock
* despite the flags: ACKs moving a connection out of the syncache,
* and ACKs for a connection in TIMEWAIT.
*/
if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
tcp_read_locking == 0) {
INP_INFO_WLOCK(&V_tcbinfo);
ti_locked = TI_WLOCKED;
} else {
INP_INFO_RLOCK(&V_tcbinfo);
ti_locked = TI_RLOCKED;
}
findpcb:
#ifdef INVARIANTS
if (ti_locked == TI_RLOCKED)
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
else
panic("%s: findpcb ti_locked %d\n", __func__, ti_locked);
#endif
#ifdef IPFIREWALL_FORWARD
/*
* Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
*/
fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
if (fwd_tag != NULL && isipv6 == 0) { /* IPv6 support is not yet */
struct sockaddr_in *next_hop;
next_hop = (struct sockaddr_in *)(fwd_tag+1);
/*
* Transparently forwarded. Pretend to be the destination.
* already got one like this?
*/
inp = in_pcblookup_hash(&V_tcbinfo,
ip->ip_src, th->th_sport,
ip->ip_dst, th->th_dport,
0, m->m_pkthdr.rcvif);
if (!inp) {
/* It's new. Try to find the ambushing socket. */
inp = in_pcblookup_hash(&V_tcbinfo,
ip->ip_src, th->th_sport,
next_hop->sin_addr,
next_hop->sin_port ?
ntohs(next_hop->sin_port) :
th->th_dport,
INPLOOKUP_WILDCARD,
m->m_pkthdr.rcvif);
}
/* Remove the tag from the packet. We don't need it anymore. */
m_tag_delete(m, fwd_tag);
} else
#endif /* IPFIREWALL_FORWARD */
{
if (isipv6) {
#ifdef INET6
inp = in6_pcblookup_hash(&V_tcbinfo,
&ip6->ip6_src, th->th_sport,
&ip6->ip6_dst, th->th_dport,
INPLOOKUP_WILDCARD,
m->m_pkthdr.rcvif);
#endif
} else
inp = in_pcblookup_hash(&V_tcbinfo,
ip->ip_src, th->th_sport,
ip->ip_dst, th->th_dport,
INPLOOKUP_WILDCARD,
m->m_pkthdr.rcvif);
}
/*
* If the INPCB does not exist then all data in the incoming
* segment is discarded and an appropriate RST is sent back.
* XXX MRT Send RST using which routing table?
*/
if (inp == NULL) {
/*
* Log communication attempts to ports that are not
* in use.
*/
if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
tcp_log_in_vain == 2) {
if ((s = tcp_log_addrs(NULL, th, (void *)ip, ip6)))
log(LOG_INFO, "%s; %s: Connection attempt "
"to closed port\n", s, __func__);
}
/*
* When blackholing do not respond with a RST but
* completely ignore the segment and drop it.
*/
if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
V_blackhole == 2)
goto dropunlock;
rstreason = BANDLIM_RST_CLOSEDPORT;
goto dropwithreset;
}
INP_WLOCK(inp);
if (!(inp->inp_flags & INP_HW_FLOWID)
&& (m->m_flags & M_FLOWID)
&& ((inp->inp_socket == NULL)
|| !(inp->inp_socket->so_options & SO_ACCEPTCONN))) {
inp->inp_flags |= INP_HW_FLOWID;
inp->inp_flags &= ~INP_SW_FLOWID;
inp->inp_flowid = m->m_pkthdr.flowid;
}
#ifdef IPSEC
#ifdef INET6
if (isipv6 && ipsec6_in_reject(m, inp)) {
V_ipsec6stat.in_polvio++;
goto dropunlock;
} else
#endif /* INET6 */
if (ipsec4_in_reject(m, inp) != 0) {
V_ipsec4stat.in_polvio++;
goto dropunlock;
}
#endif /* IPSEC */
/*
* Check the minimum TTL for socket.
*/
if (inp->inp_ip_minttl != 0) {
#ifdef INET6
if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
goto dropunlock;
else
#endif
if (inp->inp_ip_minttl > ip->ip_ttl)
goto dropunlock;
}
/*
* A previous connection in TIMEWAIT state is supposed to catch stray
* or duplicate segments arriving late. If this segment was a
* legitimate new connection attempt the old INPCB gets removed and
* we can try again to find a listening socket.
*
* At this point, due to earlier optimism, we may hold a read lock on
* the inpcbinfo, rather than a write lock. If so, we need to
* upgrade, or if that fails, acquire a reference on the inpcb, drop
* all locks, acquire a global write lock, and then re-acquire the
* inpcb lock. We may at that point discover that another thread has
* tried to free the inpcb, in which case we need to loop back and
* try to find a new inpcb to deliver to.
*/
relocked:
if (inp->inp_flags & INP_TIMEWAIT) {
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("%s: INP_TIMEWAIT ti_locked %d", __func__, ti_locked));
if (ti_locked == TI_RLOCKED) {
if (INP_INFO_TRY_UPGRADE(&V_tcbinfo) == 0) {
in_pcbref(inp);
INP_WUNLOCK(inp);
INP_INFO_RUNLOCK(&V_tcbinfo);
INP_INFO_WLOCK(&V_tcbinfo);
ti_locked = TI_WLOCKED;
INP_WLOCK(inp);
if (in_pcbrele(inp)) {
inp = NULL;
goto findpcb;
}
} else
ti_locked = TI_WLOCKED;
}
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
if (thflags & TH_SYN)
tcp_dooptions(&to, optp, optlen, TO_SYN);
/*
* NB: tcp_twcheck unlocks the INP and frees the mbuf.
*/
if (tcp_twcheck(inp, &to, th, m, tlen))
goto findpcb;
INP_INFO_WUNLOCK(&V_tcbinfo);
return;
}
/*
* The TCPCB may no longer exist if the connection is winding
* down or it is in the CLOSED state. Either way we drop the
* segment and send an appropriate response.
*/
tp = intotcpcb(inp);
if (tp == NULL || tp->t_state == TCPS_CLOSED) {
rstreason = BANDLIM_RST_CLOSEDPORT;
goto dropwithreset;
}
/*
* We've identified a valid inpcb, but it could be that we need an
* inpcbinfo write lock and have only a read lock. In this case,
* attempt to upgrade/relock using the same strategy as the TIMEWAIT
* case above. If we relock, we have to jump back to 'relocked' as
* the connection might now be in TIMEWAIT.
*/
if (tp->t_state != TCPS_ESTABLISHED ||
(thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
tcp_read_locking == 0) {
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("%s: upgrade check ti_locked %d", __func__, ti_locked));
if (ti_locked == TI_RLOCKED) {
if (INP_INFO_TRY_UPGRADE(&V_tcbinfo) == 0) {
in_pcbref(inp);
INP_WUNLOCK(inp);
INP_INFO_RUNLOCK(&V_tcbinfo);
INP_INFO_WLOCK(&V_tcbinfo);
ti_locked = TI_WLOCKED;
INP_WLOCK(inp);
if (in_pcbrele(inp)) {
inp = NULL;
goto findpcb;
}
goto relocked;
} else
ti_locked = TI_WLOCKED;
}
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
}
#ifdef MAC
INP_WLOCK_ASSERT(inp);
if (mac_inpcb_check_deliver(inp, m))
goto dropunlock;
#endif
so = inp->inp_socket;
KASSERT(so != NULL, ("%s: so == NULL", __func__));
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG) {
ostate = tp->t_state;
if (isipv6) {
#ifdef INET6
bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
#endif
} else
bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
tcp_savetcp = *th;
}
#endif
/*
* When the socket is accepting connections (the INPCB is in LISTEN
* state) we look into the SYN cache if this is a new connection
* attempt or the completion of a previous one.
*/
if (so->so_options & SO_ACCEPTCONN) {
struct in_conninfo inc;
KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
"tp not listening", __func__));
bzero(&inc, sizeof(inc));
#ifdef INET6
if (isipv6) {
inc.inc_flags |= INC_ISIPV6;
inc.inc6_faddr = ip6->ip6_src;
inc.inc6_laddr = ip6->ip6_dst;
} else
#endif
{
inc.inc_faddr = ip->ip_src;
inc.inc_laddr = ip->ip_dst;
}
inc.inc_fport = th->th_sport;
inc.inc_lport = th->th_dport;
inc.inc_fibnum = so->so_fibnum;
/*
* Check for an existing connection attempt in syncache if
* the flag is only ACK. A successful lookup creates a new
* socket appended to the listen queue in SYN_RECEIVED state.
*/
if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
/*
* Parse the TCP options here because
* syncookies need access to the reflected
* timestamp.
*/
tcp_dooptions(&to, optp, optlen, 0);
/*
* NB: syncache_expand() doesn't unlock
* inp and tcpinfo locks.
*/
if (!syncache_expand(&inc, &to, th, &so, m)) {
/*
* No syncache entry or ACK was not
* for our SYN/ACK. Send a RST.
* NB: syncache did its own logging
* of the failure cause.
*/
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
if (so == NULL) {
/*
* We completed the 3-way handshake
* but could not allocate a socket
* either due to memory shortage,
* listen queue length limits or
* global socket limits. Send RST
* or wait and have the remote end
* retransmit the ACK for another
* try.
*/
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Socket allocation failed due to "
"limits or memory shortage, %s\n",
s, __func__,
V_tcp_sc_rst_sock_fail ?
"sending RST" : "try again");
if (V_tcp_sc_rst_sock_fail) {
rstreason = BANDLIM_UNLIMITED;
goto dropwithreset;
} else
goto dropunlock;
}
/*
* Socket is created in state SYN_RECEIVED.
* Unlock the listen socket, lock the newly
* created socket and update the tp variable.
*/
INP_WUNLOCK(inp); /* listen socket */
inp = sotoinpcb(so);
INP_WLOCK(inp); /* new connection */
tp = intotcpcb(inp);
KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
("%s: ", __func__));
/*
* Process the segment and the data it
* contains. tcp_do_segment() consumes
* the mbuf chain and unlocks the inpcb.
*/
tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
iptos, ti_locked);
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
return;
}
/*
* Segment flag validation for new connection attempts:
*
* Our (SYN|ACK) response was rejected.
* Check with syncache and remove entry to prevent
* retransmits.
*
* NB: syncache_chkrst does its own logging of failure
* causes.
*/
if (thflags & TH_RST) {
syncache_chkrst(&inc, th);
goto dropunlock;
}
/*
* We can't do anything without SYN.
*/
if ((thflags & TH_SYN) == 0) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"SYN is missing, segment ignored\n",
s, __func__);
TCPSTAT_INC(tcps_badsyn);
goto dropunlock;
}
/*
* (SYN|ACK) is bogus on a listen socket.
*/
if (thflags & TH_ACK) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"SYN|ACK invalid, segment rejected\n",
s, __func__);
syncache_badack(&inc); /* XXX: Not needed! */
TCPSTAT_INC(tcps_badsyn);
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
/*
* If the drop_synfin option is enabled, drop all
* segments with both the SYN and FIN bits set.
* This prevents e.g. nmap from identifying the
* TCP/IP stack.
* XXX: Poor reasoning. nmap has other methods
* and is constantly refining its stack detection
* strategies.
* XXX: This is a violation of the TCP specification
* and was used by RFC1644.
*/
if ((thflags & TH_FIN) && V_drop_synfin) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"SYN|FIN segment ignored (based on "
"sysctl setting)\n", s, __func__);
TCPSTAT_INC(tcps_badsyn);
goto dropunlock;
}
/*
* Segment's flags are (SYN) or (SYN|FIN).
*
* TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
* as they do not affect the state of the TCP FSM.
* The data pointed to by TH_URG and th_urp is ignored.
*/
KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
("%s: Listen socket: TH_RST or TH_ACK set", __func__));
KASSERT(thflags & (TH_SYN),
("%s: Listen socket: TH_SYN not set", __func__));
#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 (isipv6 && !V_ip6_use_deprecated) {
struct in6_ifaddr *ia6;
ia6 = ip6_getdstifaddr(m);
if (ia6 != NULL &&
(ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
ifa_free(&ia6->ia_ifa);
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt to deprecated "
"IPv6 address rejected\n",
s, __func__);
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
ifa_free(&ia6->ia_ifa);
}
#endif
/*
* Basic sanity checks on incoming SYN requests:
* Don't respond if the destination is a link layer
* broadcast according to RFC1122 4.2.3.10, p. 104.
* If it is from this socket it must be forged.
* Don't respond if the source or destination is a
* global or subnet broad- or multicast address.
* Note that it is quite possible to receive unicast
* link-layer packets with a broadcast IP address. Use
* in_broadcast() to find them.
*/
if (m->m_flags & (M_BCAST|M_MCAST)) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt from broad- or multicast "
"link layer address ignored\n", s, __func__);
goto dropunlock;
}
if (isipv6) {
#ifdef INET6
if (th->th_dport == th->th_sport &&
IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt to/from self "
"ignored\n", s, __func__);
goto dropunlock;
}
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt from/to multicast "
"address ignored\n", s, __func__);
goto dropunlock;
}
#endif
} else {
if (th->th_dport == th->th_sport &&
ip->ip_dst.s_addr == ip->ip_src.s_addr) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt from/to self "
"ignored\n", s, __func__);
goto dropunlock;
}
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
log(LOG_DEBUG, "%s; %s: Listen socket: "
"Connection attempt from/to broad- "
"or multicast address ignored\n",
s, __func__);
goto dropunlock;
}
}
/*
* SYN appears to be valid. Create compressed TCP state
* for syncache.
*/
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen, &tcp_savetcp, 0);
#endif
tcp_dooptions(&to, optp, optlen, TO_SYN);
syncache_add(&inc, &to, th, inp, &so, m);
/*
* Entry added to syncache and mbuf consumed.
* Everything already unlocked by syncache_add().
*/
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
return;
}
/*
* Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
* state. tcp_do_segment() always consumes the mbuf chain, unlocks
* the inpcb, and unlocks pcbinfo.
*/
tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
return;
dropwithreset:
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: dropwithreset ti_locked %d", __func__, ti_locked);
ti_locked = TI_UNLOCKED;
if (inp != NULL) {
tcp_dropwithreset(m, th, tp, tlen, rstreason);
INP_WUNLOCK(inp);
} else
tcp_dropwithreset(m, th, NULL, tlen, rstreason);
m = NULL; /* mbuf chain got consumed. */
goto drop;
dropunlock:
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: dropunlock ti_locked %d", __func__, ti_locked);
ti_locked = TI_UNLOCKED;
if (inp != NULL)
INP_WUNLOCK(inp);
drop:
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
if (s != NULL)
free(s, M_TCPLOG);
if (m != NULL)
m_freem(m);
}
static void
tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
int ti_locked)
{
int thflags, acked, ourfinisacked, needoutput = 0;
int rstreason, todrop, win;
u_long tiwin;
struct tcpopt to;
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[IP6_HDR_LEN];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
thflags = th->th_flags;
/*
* If this is either a state-changing packet or current state isn't
* established, we require a write lock on tcbinfo. Otherwise, we
* allow either a read lock or a write lock, as we may have acquired
* a write lock due to a race.
*
* Require a global write lock for SYN/FIN/RST segments or
* non-established connections; otherwise accept either a read or
* write lock, as we may have conservatively acquired a write lock in
* certain cases in tcp_input() (is this still true?). Currently we
* will never enter with no lock, so we try to drop it quickly in the
* common pure ack/pure data cases.
*/
if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
tp->t_state != TCPS_ESTABLISHED) {
KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for "
"SYN/FIN/RST/!EST", __func__, ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
} else {
#ifdef INVARIANTS
if (ti_locked == TI_RLOCKED)
INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
else
panic("%s: ti_locked %d for EST", __func__,
ti_locked);
#endif
}
INP_WLOCK_ASSERT(tp->t_inpcb);
KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
__func__));
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
__func__));
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
* XXX: This should be done after segment
* validation to ignore broken/spoofed segs.
*/
tp->t_rcvtime = ticks;
if (TCPS_HAVEESTABLISHED(tp->t_state))
tcp_timer_activate(tp, TT_KEEP, tcp_keepidle);
/*
* Unscale the window into a 32-bit value.
* For the SYN_SENT state the scale is zero.
*/
tiwin = th->th_win << tp->snd_scale;
/*
* TCP ECN processing.
*/
if (tp->t_flags & TF_ECN_PERMIT) {
switch (iptos & IPTOS_ECN_MASK) {
case IPTOS_ECN_CE:
tp->t_flags |= TF_ECN_SND_ECE;
TCPSTAT_INC(tcps_ecn_ce);
break;
case IPTOS_ECN_ECT0:
TCPSTAT_INC(tcps_ecn_ect0);
break;
case IPTOS_ECN_ECT1:
TCPSTAT_INC(tcps_ecn_ect1);
break;
}
if (thflags & TH_CWR)
tp->t_flags &= ~TF_ECN_SND_ECE;
/*
* Congestion experienced.
* Ignore if we are already trying to recover.
*/
if ((thflags & TH_ECE) &&
SEQ_LEQ(th->th_ack, tp->snd_recover)) {
TCPSTAT_INC(tcps_ecn_rcwnd);
tcp_congestion_exp(tp);
}
}
/*
* Parse options on any incoming segment.
*/
tcp_dooptions(&to, (u_char *)(th + 1),
(th->th_off << 2) - sizeof(struct tcphdr),
(thflags & TH_SYN) ? TO_SYN : 0);
/*
* If echoed timestamp is later than the current time,
* fall back to non RFC1323 RTT calculation. Normalize
* timestamp if syncookies were used when this connection
* was established.
*/
if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
to.to_tsecr -= tp->ts_offset;
if (TSTMP_GT(to.to_tsecr, ticks))
to.to_tsecr = 0;
}
/*
* Process options only when we get SYN/ACK back. The SYN case
* for incoming connections is handled in tcp_syncache.
* According to RFC1323 the window field in a SYN (i.e., a <SYN>
* or <SYN,ACK>) segment itself is never scaled.
* XXX this is traditional behavior, may need to be cleaned up.
*/
if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
if ((to.to_flags & TOF_SCALE) &&
(tp->t_flags & TF_REQ_SCALE)) {
tp->t_flags |= TF_RCVD_SCALE;
tp->snd_scale = to.to_wscale;
}
/*
* Initial send window. It will be updated with
* the next incoming segment to the scaled value.
*/
tp->snd_wnd = th->th_win;
if (to.to_flags & TOF_TS) {
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = to.to_tsval;
tp->ts_recent_age = ticks;
}
if (to.to_flags & TOF_MSS)
tcp_mss(tp, to.to_mss);
if ((tp->t_flags & TF_SACK_PERMIT) &&
(to.to_flags & TOF_SACKPERM) == 0)
tp->t_flags &= ~TF_SACK_PERMIT;
}
/*
* 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.
* Make sure that the hidden state-flags are also off.
* Since we check for TCPS_ESTABLISHED first, it can only
* be TH_NEEDSYN.
*/
if (tp->t_state == TCPS_ESTABLISHED &&
th->th_seq == tp->rcv_nxt &&
(thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
tp->snd_nxt == tp->snd_max &&
tiwin && tiwin == tp->snd_wnd &&
((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
LIST_EMPTY(&tp->t_segq) &&
((to.to_flags & TOF_TS) == 0 ||
TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* NOTE that the test is modified according to the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
*/
if ((to.to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
tp->ts_recent_age = ticks;
tp->ts_recent = to.to_tsval;
}
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 &&
((!V_tcp_do_newreno &&
!(tp->t_flags & TF_SACK_PERMIT) &&
tp->t_dupacks < tcprexmtthresh) ||
((V_tcp_do_newreno ||
(tp->t_flags & TF_SACK_PERMIT)) &&
!IN_FASTRECOVERY(tp) &&
(to.to_flags & TOF_SACK) == 0 &&
TAILQ_EMPTY(&tp->snd_holes)))) {
/*
* This is a pure ack for outstanding data.
*/
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: ti_locked %d on pure ACK",
__func__, ti_locked);
ti_locked = TI_UNLOCKED;
TCPSTAT_INC(tcps_predack);
/*
* "bad retransmit" recovery.
*/
if (tp->t_rxtshift == 1 &&
(int)(ticks - tp->t_badrxtwin) < 0) {
TCPSTAT_INC(tcps_sndrexmitbad);
tp->snd_cwnd = tp->snd_cwnd_prev;
tp->snd_ssthresh =
tp->snd_ssthresh_prev;
tp->snd_recover = tp->snd_recover_prev;
if (tp->t_flags & TF_WASFRECOVERY)
ENTER_FASTRECOVERY(tp);
tp->snd_nxt = tp->snd_max;
tp->t_badrxtwin = 0;
}
/*
* Recalculate the transmit timer / rtt.
*
* Some boxes send broken timestamp replies
* during the SYN+ACK phase, ignore
* timestamps of 0 or we could calculate a
* huge RTT and blow up the retransmit timer.
*/
if ((to.to_flags & TOF_TS) != 0 &&
to.to_tsecr) {
if (!tp->t_rttlow ||
tp->t_rttlow > ticks - to.to_tsecr)
tp->t_rttlow = ticks - to.to_tsecr;
tcp_xmit_timer(tp,
ticks - to.to_tsecr + 1);
} else if (tp->t_rtttime &&
SEQ_GT(th->th_ack, tp->t_rtseq)) {
if (!tp->t_rttlow ||
tp->t_rttlow > ticks - tp->t_rtttime)
tp->t_rttlow = ticks - tp->t_rtttime;
tcp_xmit_timer(tp,
ticks - tp->t_rtttime);
}
tcp_xmit_bandwidth_limit(tp, th->th_ack);
acked = th->th_ack - tp->snd_una;
TCPSTAT_INC(tcps_rcvackpack);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
sbdrop(&so->so_snd, acked);
if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
tp->snd_una = th->th_ack;
/*
* Pull snd_wl2 up to prevent seq wrap relative
* to th_ack.
*/
tp->snd_wl2 = th->th_ack;
tp->t_dupacks = 0;
m_freem(m);
ND6_HINT(tp); /* Some progress has been made. */
/*
* 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.
*/
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (tp->snd_una == tp->snd_max)
tcp_timer_activate(tp, TT_REXMT, 0);
else if (!tcp_timer_active(tp, TT_PERSIST))
tcp_timer_activate(tp, TT_REXMT,
tp->t_rxtcur);
sowwakeup(so);
if (so->so_snd.sb_cc)
(void) tcp_output(tp);
goto check_delack;
}
} else if (th->th_ack == tp->snd_una &&
tlen <= sbspace(&so->so_rcv)) {
int newsize = 0; /* automatic sockbuf scaling */
/*
* This is a pure, in-sequence data packet with
* nothing on the reassembly queue and we have enough
* buffer space to take it.
*/
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: ti_locked %d on pure data "
"segment", __func__, ti_locked);
ti_locked = TI_UNLOCKED;
/* Clean receiver SACK report if present */
if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
tcp_clean_sackreport(tp);
TCPSTAT_INC(tcps_preddat);
tp->rcv_nxt += tlen;
/*
* Pull snd_wl1 up to prevent seq wrap relative to
* th_seq.
*/
tp->snd_wl1 = th->th_seq;
/*
* Pull rcv_up up to prevent seq wrap relative to
* rcv_nxt.
*/
tp->rcv_up = tp->rcv_nxt;
TCPSTAT_INC(tcps_rcvpack);
TCPSTAT_ADD(tcps_rcvbyte, tlen);
ND6_HINT(tp); /* Some progress has been made */
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen, &tcp_savetcp, 0);
#endif
/*
* Automatic sizing of receive socket buffer. Often the send
* buffer size is not optimally adjusted to the actual network
* conditions at hand (delay bandwidth product). Setting the
* buffer size too small limits throughput on links with high
* bandwidth and high delay (eg. trans-continental/oceanic links).
*
* On the receive side the socket buffer memory is only rarely
* used to any significant extent. This allows us to be much
* more aggressive in scaling the receive socket buffer. For
* the case that the buffer space is actually used to a large
* extent and we run out of kernel memory we can simply drop
* the new segments; TCP on the sender will just retransmit it
* later. Setting the buffer size too big may only consume too
* much kernel memory if the application doesn't read() from
* the socket or packet loss or reordering makes use of the
* reassembly queue.
*
* The criteria to step up the receive buffer one notch are:
* 1. the number of bytes received during the time it takes
* one timestamp to be reflected back to us (the RTT);
* 2. received bytes per RTT is within seven eighth of the
* current socket buffer size;
* 3. receive buffer size has not hit maximal automatic size;
*
* This algorithm does one step per RTT at most and only if
* we receive a bulk stream w/o packet losses or reorderings.
* Shrinking the buffer during idle times is not necessary as
* it doesn't consume any memory when idle.
*
* TODO: Only step up if the application is actually serving
* the buffer to better manage the socket buffer resources.
*/
if (V_tcp_do_autorcvbuf &&
to.to_tsecr &&
(so->so_rcv.sb_flags & SB_AUTOSIZE)) {
if (to.to_tsecr > tp->rfbuf_ts &&
to.to_tsecr - tp->rfbuf_ts < hz) {
if (tp->rfbuf_cnt >
(so->so_rcv.sb_hiwat / 8 * 7) &&
so->so_rcv.sb_hiwat <
V_tcp_autorcvbuf_max) {
newsize =
min(so->so_rcv.sb_hiwat +
V_tcp_autorcvbuf_inc,
V_tcp_autorcvbuf_max);
}
/* Start over with next RTT. */
tp->rfbuf_ts = 0;
tp->rfbuf_cnt = 0;
} else
tp->rfbuf_cnt += tlen; /* add up */
}
/* Add data to socket buffer. */
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
m_freem(m);
} else {
/*
* Set new socket buffer size.
* Give up when limit is reached.
*/
if (newsize)
if (!sbreserve_locked(&so->so_rcv,
newsize, so, NULL))
so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
m_adj(m, drop_hdrlen); /* delayed header drop */
sbappendstream_locked(&so->so_rcv, m);
}
/* NB: sorwakeup_locked() does an implicit unlock. */
sorwakeup_locked(so);
if (DELAY_ACK(tp)) {
tp->t_flags |= TF_DELACK;
} else {
tp->t_flags |= TF_ACKNOW;
tcp_output(tp);
}
goto check_delack;
}
}
/*
* 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.
*/
win = sbspace(&so->so_rcv);
if (win < 0)
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
/* Reset receive buffer auto scaling when not in bulk receive mode. */
tp->rfbuf_ts = 0;
tp->rfbuf_cnt = 0;
switch (tp->t_state) {
/*
* If the state is SYN_RECEIVED:
* if seg contains an ACK, but not for our SYN/ACK, send a RST.
*/
case TCPS_SYN_RECEIVED:
if ((thflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->snd_una) ||
SEQ_GT(th->th_ack, tp->snd_max))) {
rstreason = BANDLIM_RST_OPENPORT;
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 seg contains an ECE and ECN support is enabled, the stream
* is ECN capable.
* 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 ((thflags & TH_ACK) &&
(SEQ_LEQ(th->th_ack, tp->iss) ||
SEQ_GT(th->th_ack, tp->snd_max))) {
rstreason = BANDLIM_UNLIMITED;
goto dropwithreset;
}
if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST))
tp = tcp_drop(tp, ECONNREFUSED);
if (thflags & TH_RST)
goto drop;
if (!(thflags & TH_SYN))
goto drop;
tp->irs = th->th_seq;
tcp_rcvseqinit(tp);
if (thflags & TH_ACK) {
TCPSTAT_INC(tcps_connects);
soisconnected(so);
#ifdef MAC
mac_socketpeer_set_from_mbuf(m, so);
#endif
/* Do window scaling on this connection? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
}
tp->rcv_adv += tp->rcv_wnd;
tp->snd_una++; /* SYN is acked */
/*
* If there's data, delay ACK; if there's also a FIN
* ACKNOW will be turned on later.
*/
if (DELAY_ACK(tp) && tlen != 0)
tcp_timer_activate(tp, TT_DELACK,
tcp_delacktime);
else
tp->t_flags |= TF_ACKNOW;
if ((thflags & TH_ECE) && V_tcp_do_ecn) {
tp->t_flags |= TF_ECN_PERMIT;
TCPSTAT_INC(tcps_ecn_shs);
}
/*
* Received <SYN,ACK> in SYN_SENT[*] state.
* Transitions:
* SYN_SENT --> ESTABLISHED
* SYN_SENT* --> FIN_WAIT_1
*/
tp->t_starttime = ticks;
if (tp->t_flags & TF_NEEDFIN) {
tp->t_state = TCPS_FIN_WAIT_1;
tp->t_flags &= ~TF_NEEDFIN;
thflags &= ~TH_SYN;
} else {
tp->t_state = TCPS_ESTABLISHED;
tcp_timer_activate(tp, TT_KEEP, tcp_keepidle);
}
} else {
/*
* Received initial SYN in SYN-SENT[*] state =>
* simultaneous open. If segment contains CC option
* and there is a cached CC, apply TAO test.
* If it succeeds, connection is * half-synchronized.
* Otherwise, do 3-way handshake:
* SYN-SENT -> SYN-RECEIVED
* SYN-SENT* -> SYN-RECEIVED*
* If there was no CC option, clear cached CC value.
*/
tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
tcp_timer_activate(tp, TT_REXMT, 0);
tp->t_state = TCPS_SYN_RECEIVED;
}
KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: "
"ti_locked %d", __func__, ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* 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;
thflags &= ~TH_FIN;
TCPSTAT_INC(tcps_rcvpackafterwin);
TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
}
tp->snd_wl1 = th->th_seq - 1;
tp->rcv_up = th->th_seq;
/*
* Client side of transaction: already sent SYN and data.
* If the remote host used T/TCP to validate the SYN,
* our data will be ACK'd; if so, enter normal data segment
* processing in the middle of step 5, ack processing.
* Otherwise, goto step 6.
*/
if (thflags & TH_ACK)
goto process_ACK;
goto step6;
/*
* If the state is LAST_ACK or CLOSING or TIME_WAIT:
* do normal processing.
*
* NB: Leftover from RFC1644 T/TCP. Cases to be reused later.
*/
case TCPS_LAST_ACK:
case TCPS_CLOSING:
break; /* continue normal processing */
}
/*
* States other than LISTEN or SYN_SENT.
* First check the RST flag and sequence number since reset segments
* are exempt from the timestamp and connection count tests. This
* fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
* below which allowed reset segments in half the sequence space
* to fall though and be processed (which gives forged reset
* segments with a random sequence number a 50 percent chance of
* killing a connection).
* Then check timestamp, if present.
* Then check the connection count, 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.
*
*
* If the RST bit is set, check the sequence number to see
* if this is a valid reset segment.
* RFC 793 page 37:
* In all states except SYN-SENT, all reset (RST) segments
* are validated by checking their SEQ-fields. A reset is
* valid if its sequence number is in the window.
* Note: this does not take into account delayed ACKs, so
* we should test against last_ack_sent instead of rcv_nxt.
* The sequence number in the reset segment is normally an
* echo of our outgoing acknowlegement numbers, but some hosts
* send a reset with the sequence number at the rightmost edge
* of our receive window, and we have to handle this case.
* Note 2: Paul Watson's paper "Slipping in the Window" has shown
* that brute force RST attacks are possible. To combat this,
* we use a much stricter check while in the ESTABLISHED state,
* only accepting RSTs where the sequence number is equal to
* last_ack_sent. In all other states (the states in which a
* RST is more likely), the more permissive check is used.
* If we have multiple segments in flight, the initial reset
* segment sequence numbers will be to the left of last_ack_sent,
* but they will eventually catch up.
* In any case, it never made sense to trim reset segments to
* fit the receive window since RFC 1122 says:
* 4.2.2.12 RST Segment: RFC-793 Section 3.4
*
* A TCP SHOULD allow a received RST segment to include data.
*
* DISCUSSION
* It has been suggested that a RST segment could contain
* ASCII text that encoded and explained the cause of the
* RST. No standard has yet been established for such
* data.
*
* If the reset segment passes the sequence number test 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_WAIT_2, CLOSE_WAIT STATES:
* Inform user that connection was reset, and close tcb.
* CLOSING, LAST_ACK STATES:
* Close the tcb.
* TIME_WAIT STATE:
* Drop the segment - see Stevens, vol. 2, p. 964 and
* RFC 1337.
*/
if (thflags & TH_RST) {
if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) {
switch (tp->t_state) {
case TCPS_SYN_RECEIVED:
so->so_error = ECONNREFUSED;
goto close;
case TCPS_ESTABLISHED:
if (V_tcp_insecure_rst == 0 &&
!(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) &&
SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) &&
!(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) {
TCPSTAT_INC(tcps_badrst);
goto drop;
}
/* FALLTHROUGH */
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
so->so_error = ECONNRESET;
close:
KASSERT(ti_locked == TI_WLOCKED,
("tcp_do_segment: TH_RST 1 ti_locked %d",
ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
tp->t_state = TCPS_CLOSED;
TCPSTAT_INC(tcps_drops);
tp = tcp_close(tp);
break;
case TCPS_CLOSING:
case TCPS_LAST_ACK:
KASSERT(ti_locked == TI_WLOCKED,
("tcp_do_segment: TH_RST 2 ti_locked %d",
ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
tp = tcp_close(tp);
break;
}
}
goto drop;
}
/*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than ts_recent, drop it.
*/
if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
TSTMP_LT(to.to_tsval, tp->ts_recent)) {
/* Check to see if ts_recent is over 24 days old. */
if (ticks - 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_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, tlen);
TCPSTAT_INC(tcps_pawsdrop);
if (tlen)
goto dropafterack;
goto drop;
}
}
/*
* In the SYN-RECEIVED state, validate that the packet belongs to
* this connection before trimming the data to fit the receive
* window. Check the sequence number versus IRS since we know
* the sequence numbers haven't wrapped. This is a partial fix
* for the "LAND" DoS attack.
*/
if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) {
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
todrop = tp->rcv_nxt - th->th_seq;
if (todrop > 0) {
/*
* If this is a duplicate SYN for our current connection,
* advance over it and pretend and it's not a SYN.
*/
if (thflags & TH_SYN && th->th_seq == tp->irs) {
thflags &= ~TH_SYN;
th->th_seq++;
if (th->th_urp > 1)
th->th_urp--;
else
thflags &= ~TH_URG;
todrop--;
}
/*
* Following if statement from Stevens, vol. 2, p. 960.
*/
if (todrop > tlen
|| (todrop == tlen && (thflags & TH_FIN) == 0)) {
/*
* Any valid FIN must be to the left of the window.
* At this point the FIN must be a duplicate or out
* of sequence; drop it.
*/
thflags &= ~TH_FIN;
/*
* Send an ACK to resynchronize and drop any data.
* But keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
todrop = tlen;
TCPSTAT_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, todrop);
} else {
TCPSTAT_INC(tcps_rcvpartduppack);
TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop);
}
drop_hdrlen += todrop; /* drop from the top afterwards */
th->th_seq += todrop;
tlen -= todrop;
if (th->th_urp > todrop)
th->th_urp -= todrop;
else {
thflags &= ~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) {
char *s;
KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && "
"CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket "
"was closed, sending RST and removing tcpcb\n",
s, __func__, tcpstates[tp->t_state], tlen);
free(s, M_TCPLOG);
}
tp = tcp_close(tp);
TCPSTAT_INC(tcps_rcvafterclose);
rstreason = BANDLIM_UNLIMITED;
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_INC(tcps_rcvpackafterwin);
if (todrop >= tlen) {
TCPSTAT_ADD(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_INC(tcps_rcvwinprobe);
} else
goto dropafterack;
} else
TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
m_adj(m, -todrop);
tlen -= todrop;
thflags &= ~(TH_PUSH|TH_FIN);
}
/*
* If last ACK falls within this segment's sequence numbers,
* record its timestamp.
* NOTE:
* 1) That the test incorporates suggestions from the latest
* proposal of the tcplw@cray.com list (Braden 1993/04/26).
* 2) That updating only on newer timestamps interferes with
* our earlier PAWS tests, so this check should be solely
* predicated on the sequence space of this segment.
* 3) That we modify the segment boundary check to be
* Last.ACK.Sent <= SEG.SEQ + SEG.Len
* instead of RFC1323's
* Last.ACK.Sent < SEG.SEQ + SEG.Len,
* This modified check allows us to overcome RFC1323's
* limitations as described in Stevens TCP/IP Illustrated
* Vol. 2 p.869. In such cases, we can still calculate the
* RTT correctly when RCV.NXT == Last.ACK.Sent.
*/
if ((to.to_flags & TOF_TS) != 0 &&
SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
((thflags & (TH_SYN|TH_FIN)) != 0))) {
tp->ts_recent_age = ticks;
tp->ts_recent = to.to_tsval;
}
/*
* If a SYN is in the window, then this is an
* error and we send an RST and drop the connection.
*/
if (thflags & TH_SYN) {
KASSERT(ti_locked == TI_WLOCKED,
("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
tp = tcp_drop(tp, ECONNRESET);
rstreason = BANDLIM_UNLIMITED;
goto drop;
}
/*
* If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN
* flag is on (half-synchronized state), then queue data for
* later processing; else drop segment and return.
*/
if ((thflags & TH_ACK) == 0) {
if (tp->t_state == TCPS_SYN_RECEIVED ||
(tp->t_flags & TF_NEEDSYN))
goto step6;
else 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_INC(tcps_connects);
soisconnected(so);
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
tp->snd_wnd = tiwin;
}
/*
* Make transitions:
* SYN-RECEIVED -> ESTABLISHED
* SYN-RECEIVED* -> FIN-WAIT-1
*/
tp->t_starttime = ticks;
if (tp->t_flags & TF_NEEDFIN) {
tp->t_state = TCPS_FIN_WAIT_1;
tp->t_flags &= ~TF_NEEDFIN;
} else {
tp->t_state = TCPS_ESTABLISHED;
tcp_timer_activate(tp, TT_KEEP, tcp_keepidle);
}
/*
* If segment contains data or ACK, will call tcp_reass()
* later; if not, do so now to pass queued data to user.
*/
if (tlen == 0 && (thflags & TH_FIN) == 0)
(void) tcp_reass(tp, (struct tcphdr *)0, 0,
(struct mbuf *)0);
tp->snd_wl1 = th->th_seq - 1;
/* FALLTHROUGH */
/*
* 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:
if (SEQ_GT(th->th_ack, tp->snd_max)) {
TCPSTAT_INC(tcps_rcvacktoomuch);
goto dropafterack;
}
if ((tp->t_flags & TF_SACK_PERMIT) &&
((to.to_flags & TOF_SACK) ||
!TAILQ_EMPTY(&tp->snd_holes)))
tcp_sack_doack(tp, &to, th->th_ack);
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
if (tlen == 0 && tiwin == tp->snd_wnd) {
TCPSTAT_INC(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
* threshhold 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.
*
* When using TCP ECN, notify the peer that
* we reduced the cwnd.
*/
if (!tcp_timer_active(tp, TT_REXMT) ||
th->th_ack != tp->snd_una)
tp->t_dupacks = 0;
else if (++tp->t_dupacks > tcprexmtthresh ||
((V_tcp_do_newreno ||
(tp->t_flags & TF_SACK_PERMIT)) &&
IN_FASTRECOVERY(tp))) {
if ((tp->t_flags & TF_SACK_PERMIT) &&
IN_FASTRECOVERY(tp)) {
int awnd;
/*
* Compute the amount of data in flight first.
* We can inject new data into the pipe iff
* we have less than 1/2 the original window's
* worth of data in flight.
*/
awnd = (tp->snd_nxt - tp->snd_fack) +
tp->sackhint.sack_bytes_rexmit;
if (awnd < tp->snd_ssthresh) {
tp->snd_cwnd += tp->t_maxseg;
if (tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
}
} else
tp->snd_cwnd += tp->t_maxseg;
(void) tcp_output(tp);
goto drop;
} else if (tp->t_dupacks == tcprexmtthresh) {
tcp_seq onxt = tp->snd_nxt;
/*
* If we're doing sack, check to
* see if we're already in sack
* recovery. If we're not doing sack,
* check to see if we're in newreno
* recovery.
*/
if (tp->t_flags & TF_SACK_PERMIT) {
if (IN_FASTRECOVERY(tp)) {
tp->t_dupacks = 0;
break;
}
} else if (V_tcp_do_newreno ||
V_tcp_do_ecn) {
if (SEQ_LEQ(th->th_ack,
tp->snd_recover)) {
tp->t_dupacks = 0;
break;
}
}
tcp_congestion_exp(tp);
tcp_timer_activate(tp, TT_REXMT, 0);
tp->t_rtttime = 0;
if (tp->t_flags & TF_SACK_PERMIT) {
TCPSTAT_INC(
tcps_sack_recovery_episode);
tp->sack_newdata = tp->snd_nxt;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);
goto drop;
}
tp->snd_nxt = th->th_ack;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);
KASSERT(tp->snd_limited <= 2,
("%s: tp->snd_limited too big",
__func__));
tp->snd_cwnd = tp->snd_ssthresh +
tp->t_maxseg *
(tp->t_dupacks - tp->snd_limited);
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
goto drop;
} else if (V_tcp_do_rfc3042) {
u_long oldcwnd = tp->snd_cwnd;
tcp_seq oldsndmax = tp->snd_max;
u_int sent;
KASSERT(tp->t_dupacks == 1 ||
tp->t_dupacks == 2,
("%s: dupacks not 1 or 2",
__func__));
if (tp->t_dupacks == 1)
tp->snd_limited = 0;
tp->snd_cwnd =
(tp->snd_nxt - tp->snd_una) +
(tp->t_dupacks - tp->snd_limited) *
tp->t_maxseg;
(void) tcp_output(tp);
sent = tp->snd_max - oldsndmax;
if (sent > tp->t_maxseg) {
KASSERT((tp->t_dupacks == 2 &&
tp->snd_limited == 0) ||
(sent == tp->t_maxseg + 1 &&
tp->t_flags & TF_SENTFIN),
("%s: sent too much",
__func__));
tp->snd_limited = 2;
} else if (sent > 0)
++tp->snd_limited;
tp->snd_cwnd = oldcwnd;
goto drop;
}
} else
tp->t_dupacks = 0;
break;
}
KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
("%s: th_ack <= snd_una", __func__));
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
if (V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) {
if (IN_FASTRECOVERY(tp)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (tp->t_flags & TF_SACK_PERMIT)
tcp_sack_partialack(tp, th);
else
tcp_newreno_partial_ack(tp, th);
} else {
/*
* Out of fast recovery.
* Window inflation should have left us
* with approximately snd_ssthresh
* outstanding data.
* But in case we would be inclined to
* send a burst, better to do it via
* the slow start mechanism.
*/
if (SEQ_GT(th->th_ack +
tp->snd_ssthresh,
tp->snd_max))
tp->snd_cwnd = tp->snd_max -
th->th_ack +
tp->t_maxseg;
else
tp->snd_cwnd = tp->snd_ssthresh;
}
}
} else {
if (tp->t_dupacks >= tcprexmtthresh &&
tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
}
tp->t_dupacks = 0;
/*
* If we reach this point, ACK is not a duplicate,
* i.e., it ACKs something we sent.
*/
if (tp->t_flags & TF_NEEDSYN) {
/*
* T/TCP: Connection was half-synchronized, and our
* SYN has been ACK'd (so connection is now fully
* synchronized). Go to non-starred state,
* increment snd_una for ACK of SYN, and check if
* we can do window scaling.
*/
tp->t_flags &= ~TF_NEEDSYN;
tp->snd_una++;
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->rcv_scale = tp->request_r_scale;
/* Send window already scaled. */
}
}
process_ACK:
INP_INFO_LOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("tcp_input: process_ACK ti_locked %d", ti_locked));
INP_WLOCK_ASSERT(tp->t_inpcb);
acked = th->th_ack - tp->snd_una;
TCPSTAT_INC(tcps_rcvackpack);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
/*
* If we just performed our first retransmit, and the ACK
* arrives within our recovery window, then it was a mistake
* to do the retransmit in the first place. Recover our
* original cwnd and ssthresh, and proceed to transmit where
* we left off.
*/
if (tp->t_rxtshift == 1 && (int)(ticks - tp->t_badrxtwin) < 0) {
TCPSTAT_INC(tcps_sndrexmitbad);
tp->snd_cwnd = tp->snd_cwnd_prev;
tp->snd_ssthresh = tp->snd_ssthresh_prev;
tp->snd_recover = tp->snd_recover_prev;
if (tp->t_flags & TF_WASFRECOVERY)
ENTER_FASTRECOVERY(tp);
tp->snd_nxt = tp->snd_max;
tp->t_badrxtwin = 0; /* XXX probably not required */
}
/*
* 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.
*
* Some boxes send broken timestamp replies
* during the SYN+ACK phase, ignore
* timestamps of 0 or we could calculate a
* huge RTT and blow up the retransmit timer.
*/
if ((to.to_flags & TOF_TS) != 0 &&
to.to_tsecr) {
if (!tp->t_rttlow || tp->t_rttlow > ticks - to.to_tsecr)
tp->t_rttlow = ticks - to.to_tsecr;
tcp_xmit_timer(tp, ticks - to.to_tsecr + 1);
} else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
tp->t_rttlow = ticks - tp->t_rtttime;
tcp_xmit_timer(tp, ticks - tp->t_rtttime);
}
tcp_xmit_bandwidth_limit(tp, th->th_ack);
/*
* 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_activate(tp, TT_REXMT, 0);
needoutput = 1;
} else if (!tcp_timer_active(tp, TT_PERSIST))
tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
/*
* If no data (only SYN) was ACK'd,
* skip rest of ACK processing.
*/
if (acked == 0)
goto step6;
/*
* When new data is acked, open the congestion window.
* Method depends on which congestion control state we're
* in (slow start or cong avoid) and if ABC (RFC 3465) is
* enabled.
*
* slow start: cwnd <= ssthresh
* cong avoid: cwnd > ssthresh
*
* slow start and ABC (RFC 3465):
* Grow cwnd exponentially by the amount of data
* ACKed capping the max increment per ACK to
* (abc_l_var * maxseg) bytes.
*
* slow start without ABC (RFC 2581):
* Grow cwnd exponentially by maxseg per ACK.
*
* cong avoid and ABC (RFC 3465):
* Grow cwnd linearly by maxseg per RTT for each
* cwnd worth of ACKed data.
*
* cong avoid without ABC (RFC 2581):
* Grow cwnd linearly by approximately maxseg per RTT using
* maxseg^2 / cwnd per ACK as the increment.
* If cwnd > maxseg^2, fix the cwnd increment at 1 byte to
* avoid capping cwnd.
*/
if ((!V_tcp_do_newreno && !(tp->t_flags & TF_SACK_PERMIT)) ||
!IN_FASTRECOVERY(tp)) {
u_int cw = tp->snd_cwnd;
u_int incr = tp->t_maxseg;
/* In congestion avoidance? */
if (cw > tp->snd_ssthresh) {
if (V_tcp_do_rfc3465) {
tp->t_bytes_acked += acked;
if (tp->t_bytes_acked >= tp->snd_cwnd)
tp->t_bytes_acked -= cw;
else
incr = 0;
}
else
incr = max((incr * incr / cw), 1);
/*
* In slow-start with ABC enabled and no RTO in sight?
* (Must not use abc_l_var > 1 if slow starting after an
* RTO. On RTO, snd_nxt = snd_una, so the snd_nxt ==
* snd_max check is sufficient to handle this).
*/
} else if (V_tcp_do_rfc3465 &&
tp->snd_nxt == tp->snd_max)
incr = min(acked,
V_tcp_abc_l_var * tp->t_maxseg);
/* ABC is on by default, so (incr == 0) frequently. */
if (incr > 0)
tp->snd_cwnd = min(cw+incr, TCP_MAXWIN<<tp->snd_scale);
}
SOCKBUF_LOCK(&so->so_snd);
if (acked > so->so_snd.sb_cc) {
tp->snd_wnd -= so->so_snd.sb_cc;
sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc);
ourfinisacked = 1;
} else {
sbdrop_locked(&so->so_snd, acked);
tp->snd_wnd -= acked;
ourfinisacked = 0;
}
/* NB: sowwakeup_locked() does an implicit unlock. */
sowwakeup_locked(so);
/* Detect una wraparound. */
if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) &&
!IN_FASTRECOVERY(tp) &&
SEQ_GT(tp->snd_una, tp->snd_recover) &&
SEQ_LEQ(th->th_ack, tp->snd_recover))
tp->snd_recover = th->th_ack - 1;
if ((V_tcp_do_newreno || (tp->t_flags & TF_SACK_PERMIT)) &&
IN_FASTRECOVERY(tp) &&
SEQ_GEQ(th->th_ack, tp->snd_recover)) {
EXIT_FASTRECOVERY(tp);
tp->t_bytes_acked = 0;
}
tp->snd_una = th->th_ack;
if (tp->t_flags & TF_SACK_PERMIT) {
if (SEQ_GT(tp->snd_una, tp->snd_recover))
tp->snd_recover = tp->snd_una;
}
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
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.
*
* XXXjl:
* we should release the tp also, and use a
* compressed state.
*/
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
int timeout;
soisdisconnected(so);
timeout = (tcp_fast_finwait2_recycle) ?
tcp_finwait2_timeout : tcp_maxidle;
tcp_timer_activate(tp, TT_2MSL, timeout);
}
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) {
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
tcp_twstart(tp);
INP_INFO_WUNLOCK(&V_tcbinfo);
m_freem(m);
return;
}
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) {
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
tp = tcp_close(tp);
goto drop;
}
break;
}
}
step6:
INP_INFO_LOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("tcp_do_segment: step6 ti_locked %d", ti_locked));
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* Update window information.
* Don't look at window if no ACK: TAC's send garbage on first SYN.
*/
if ((thflags & 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_INC(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 ((thflags & 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.
*/
SOCKBUF_LOCK(&so->so_rcv);
if (th->th_urp + so->so_rcv.sb_cc > sb_max) {
th->th_urp = 0; /* XXX */
thflags &= ~TH_URG; /* XXX */
SOCKBUF_UNLOCK(&so->so_rcv); /* 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_rcv.sb_state |= SBS_RCVATMARK;
sohasoutofband(so);
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
}
SOCKBUF_UNLOCK(&so->so_rcv);
/*
* 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_long)tlen &&
!(so->so_options & SO_OOBINLINE)) {
/* hdr drop is delayed */
tcp_pulloutofband(so, th, m, drop_hdrlen);
}
} 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 */
INP_INFO_LOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("tcp_do_segment: dodata ti_locked %d", ti_locked));
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* 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 || (thflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
tcp_seq save_start = th->th_seq;
m_adj(m, drop_hdrlen); /* delayed header drop */
/*
* Insert segment which includes th into TCP reassembly queue
* with control block tp. Set thflags to whether reassembly now
* includes a segment with FIN. This handles 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).
*/
if (th->th_seq == tp->rcv_nxt &&
LIST_EMPTY(&tp->t_segq) &&
TCPS_HAVEESTABLISHED(tp->t_state)) {
if (DELAY_ACK(tp))
tp->t_flags |= TF_DELACK;
else
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt += tlen;
thflags = th->th_flags & TH_FIN;
TCPSTAT_INC(tcps_rcvpack);
TCPSTAT_ADD(tcps_rcvbyte, tlen);
ND6_HINT(tp);
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
m_freem(m);
else
sbappendstream_locked(&so->so_rcv, m);
/* NB: sorwakeup_locked() does an implicit unlock. */
sorwakeup_locked(so);
} else {
/*
* XXX: Due to the header drop above "th" is
* theoretically invalid by now. Fortunately
* m_adj() doesn't actually frees any mbufs
* when trimming from the head.
*/
thflags = tcp_reass(tp, th, &tlen, m);
tp->t_flags |= TF_ACKNOW;
}
if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
tcp_update_sack_list(tp, save_start, save_start + tlen);
#if 0
/*
* Note the amount of data that peer has sent into
* our window, in order to estimate the sender's
* buffer size.
* XXX: Unused.
*/
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
#endif
} else {
m_freem(m);
thflags &= ~TH_FIN;
}
/*
* If FIN is received ACK the FIN and let the user know
* that the connection is closing.
*/
if (thflags & TH_FIN) {
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
socantrcvmore(so);
/*
* If connection is half-synchronized
* (ie NEEDSYN flag on) then delay ACK,
* so it may be piggybacked when SYN is sent.
* Otherwise, since we received a FIN then no
* more input can be expected, send ACK now.
*/
if (tp->t_flags & TF_NEEDSYN)
tp->t_flags |= TF_DELACK;
else
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt++;
}
switch (tp->t_state) {
/*
* In SYN_RECEIVED and ESTABLISHED STATES
* enter the CLOSE_WAIT state.
*/
case TCPS_SYN_RECEIVED:
tp->t_starttime = ticks;
/* FALLTHROUGH */
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:
INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata "
"TCP_FIN_WAIT_2 ti_locked: %d", __func__,
ti_locked));
tcp_twstart(tp);
INP_INFO_WUNLOCK(&V_tcbinfo);
return;
}
}
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: dodata epilogue ti_locked %d", __func__,
ti_locked);
ti_locked = TI_UNLOCKED;
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW))
(void) tcp_output(tp);
check_delack:
KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
__func__, ti_locked));
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
INP_WLOCK_ASSERT(tp->t_inpcb);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
}
INP_WUNLOCK(tp->t_inpcb);
return;
dropafterack:
KASSERT(ti_locked == TI_RLOCKED || ti_locked == TI_WLOCKED,
("tcp_do_segment: dropafterack ti_locked %d", ti_locked));
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*
* We can now skip the test for the RST flag since all
* paths to this code happen after packets containing
* RST have been dropped.
*
* In the SYN-RECEIVED state, don't send an ACK unless the
* segment we received passes the SYN-RECEIVED ACK test.
* If it fails send a RST. This breaks the loop in the
* "LAND" DoS attack, and also prevents an ACK storm
* between two listening ports that have been sent forged
* SYN segments, each with the source address of the other.
*/
if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
(SEQ_GT(tp->snd_una, th->th_ack) ||
SEQ_GT(th->th_ack, tp->snd_max)) ) {
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: dropafterack epilogue ti_locked %d", __func__,
ti_locked);
ti_locked = TI_UNLOCKED;
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
INP_WUNLOCK(tp->t_inpcb);
m_freem(m);
return;
dropwithreset:
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
else
panic("%s: dropwithreset ti_locked %d", __func__, ti_locked);
ti_locked = TI_UNLOCKED;
if (tp != NULL) {
tcp_dropwithreset(m, th, tp, tlen, rstreason);
INP_WUNLOCK(tp->t_inpcb);
} else
tcp_dropwithreset(m, th, NULL, tlen, rstreason);
return;
drop:
if (ti_locked == TI_RLOCKED)
INP_INFO_RUNLOCK(&V_tcbinfo);
else if (ti_locked == TI_WLOCKED)
INP_INFO_WUNLOCK(&V_tcbinfo);
#ifdef INVARIANTS
else
INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
#endif
ti_locked = TI_UNLOCKED;
/*
* Drop space held by incoming segment and return.
*/
#ifdef TCPDEBUG
if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (tp != NULL)
INP_WUNLOCK(tp->t_inpcb);
m_freem(m);
}
/*
* Issue RST and make ACK acceptable to originator of segment.
* The mbuf must still include the original packet header.
* tp may be NULL.
*/
static void
tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
int tlen, int rstreason)
{
struct ip *ip;
#ifdef INET6
struct ip6_hdr *ip6;
#endif
if (tp != NULL) {
INP_WLOCK_ASSERT(tp->t_inpcb);
}
/* Don't bother if destination was broadcast/multicast. */
if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
goto drop;
#ifdef INET6
if (mtod(m, struct ip *)->ip_v == 6) {
ip6 = mtod(m, struct ip6_hdr *);
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
goto drop;
/* IPv6 anycast check is done at tcp6_input() */
} else
#endif
{
ip = mtod(m, struct ip *);
if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
goto drop;
}
/* Perform bandwidth limiting. */
if (badport_bandlim(rstreason) < 0)
goto drop;
/* tcp_respond consumes the mbuf chain. */
if (th->th_flags & TH_ACK) {
tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
th->th_ack, TH_RST);
} else {
if (th->th_flags & TH_SYN)
tlen++;
tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
(tcp_seq)0, TH_RST|TH_ACK);
}
return;
drop:
m_freem(m);
}
/*
* Parse TCP options and place in tcpopt.
*/
static void
tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
{
int opt, optlen;
to->to_flags = 0;
for (; 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) {
case TCPOPT_MAXSEG:
if (optlen != TCPOLEN_MAXSEG)
continue;
if (!(flags & TO_SYN))
continue;
to->to_flags |= TOF_MSS;
bcopy((char *)cp + 2,
(char *)&to->to_mss, sizeof(to->to_mss));
to->to_mss = ntohs(to->to_mss);
break;
case TCPOPT_WINDOW:
if (optlen != TCPOLEN_WINDOW)
continue;
if (!(flags & TO_SYN))
continue;
to->to_flags |= TOF_SCALE;
to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
break;
case TCPOPT_TIMESTAMP:
if (optlen != TCPOLEN_TIMESTAMP)
continue;
to->to_flags |= TOF_TS;
bcopy((char *)cp + 2,
(char *)&to->to_tsval, sizeof(to->to_tsval));
to->to_tsval = ntohl(to->to_tsval);
bcopy((char *)cp + 6,
(char *)&to->to_tsecr, sizeof(to->to_tsecr));
to->to_tsecr = ntohl(to->to_tsecr);
break;
#ifdef TCP_SIGNATURE
/*
* XXX In order to reply to a host which has set the
* TCP_SIGNATURE option in its initial SYN, we have to
* record the fact that the option was observed here
* for the syncache code to perform the correct response.
*/
case TCPOPT_SIGNATURE:
if (optlen != TCPOLEN_SIGNATURE)
continue;
to->to_flags |= TOF_SIGNATURE;
to->to_signature = cp + 2;
break;
#endif
case TCPOPT_SACK_PERMITTED:
if (optlen != TCPOLEN_SACK_PERMITTED)
continue;
if (!(flags & TO_SYN))
continue;
if (!V_tcp_do_sack)
continue;
to->to_flags |= TOF_SACKPERM;
break;
case TCPOPT_SACK:
if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
continue;
if (flags & TO_SYN)
continue;
to->to_flags |= TOF_SACK;
to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
to->to_sacks = cp + 2;
TCPSTAT_INC(tcps_sack_rcv_blocks);
break;
default:
continue;
}
}
}
/*
* 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.
*/
static void
tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
int off)
{
int cnt = off + th->th_urp - 1;
while (cnt >= 0) {
if (m->m_len > cnt) {
char *cp = mtod(m, caddr_t) + cnt;
struct tcpcb *tp = sototcpcb(so);
INP_WLOCK_ASSERT(tp->t_inpcb);
tp->t_iobc = *cp;
tp->t_oobflags |= TCPOOB_HAVEDATA;
bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
m->m_len--;
if (m->m_flags & M_PKTHDR)
m->m_pkthdr.len--;
return;
}
cnt -= m->m_len;
m = m->m_next;
if (m == NULL)
break;
}
panic("tcp_pulloutofband");
}
/*
* Collect new round-trip time estimate
* and update averages and current timeout.
*/
static void
tcp_xmit_timer(struct tcpcb *tp, int rtt)
{
int delta;
INP_WLOCK_ASSERT(tp->t_inpcb);
TCPSTAT_INC(tcps_rttupdated);
tp->t_rttupdated++;
if (tp->t_srtt != 0) {
/*
* srtt is stored as fixed point with 5 bits after the
* binary point (i.e., scaled by 8). 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). Adjust rtt to origin 0.
*/
delta = ((rtt - 1) << TCP_DELTA_SHIFT)
- (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
if ((tp->t_srtt += delta) <= 0)
tp->t_srtt = 1;
/*
* 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 - TCP_DELTA_SHIFT);
if ((tp->t_rttvar += delta) <= 0)
tp->t_rttvar = 1;
if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
} 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 << TCP_RTT_SHIFT;
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
}
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).
*/
TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
max(tp->t_rttmin, rtt + 2), 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.
*
* In case of T/TCP, we call this routine during implicit connection
* setup as well (offer = -1), to initialize maxseg from the cached
* MSS of our peer.
*
* NOTE that this routine is only called when we process an incoming
* segment. Outgoing SYN/ACK MSS settings are handled in tcp_mssopt().
*/
void
tcp_mss_update(struct tcpcb *tp, int offer,
struct hc_metrics_lite *metricptr, int *mtuflags)
{
int mss;
u_long maxmtu;
struct inpcb *inp = tp->t_inpcb;
struct hc_metrics_lite metrics;
int origoffer = offer;
#ifdef INET6
int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
size_t min_protoh = isipv6 ?
sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
sizeof (struct tcpiphdr);
#else
const size_t min_protoh = sizeof(struct tcpiphdr);
#endif
INP_WLOCK_ASSERT(tp->t_inpcb);
/* Initialize. */
#ifdef INET6
if (isipv6) {
maxmtu = tcp_maxmtu6(&inp->inp_inc, mtuflags);
tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
} else
#endif
{
maxmtu = tcp_maxmtu(&inp->inp_inc, mtuflags);
tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
}
/*
* No route to sender, stay with default mss and return.
*/
if (maxmtu == 0) {
/*
* In case we return early we need to initialize metrics
* to a defined state as tcp_hc_get() would do for us
* if there was no cache hit.
*/
if (metricptr != NULL)
bzero(metricptr, sizeof(struct hc_metrics_lite));
return;
}
/* What have we got? */
switch (offer) {
case 0:
/*
* Offer == 0 means that there was no MSS on the SYN
* segment, in this case we use tcp_mssdflt as
* already assigned to t_maxopd above.
*/
offer = tp->t_maxopd;
break;
case -1:
/*
* Offer == -1 means that we didn't receive SYN yet.
*/
/* FALLTHROUGH */
default:
/*
* Prevent DoS attack with too small MSS. Round up
* to at least minmss.
*/
offer = max(offer, V_tcp_minmss);
}
/*
* rmx information is now retrieved from tcp_hostcache.
*/
tcp_hc_get(&inp->inp_inc, &metrics);
if (metricptr != NULL)
bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
/*
* If there's a discovered mtu int tcp hostcache, use it
* else, use the link mtu.
*/
if (metrics.rmx_mtu)
mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
else {
#ifdef INET6
if (isipv6) {
mss = maxmtu - min_protoh;
if (!V_path_mtu_discovery &&
!in6_localaddr(&inp->in6p_faddr))
mss = min(mss, V_tcp_v6mssdflt);
} else
#endif
{
mss = maxmtu - min_protoh;
if (!V_path_mtu_discovery &&
!in_localaddr(inp->inp_faddr))
mss = min(mss, V_tcp_mssdflt);
}
/*
* XXX - The above conditional (mss = maxmtu - min_protoh)
* probably violates the TCP spec.
* The problem is that, since we don't know the
* other end's MSS, we are supposed to use a conservative
* default. But, if we do that, then MTU discovery will
* never actually take place, because the conservative
* default is much less than the MTUs typically seen
* on the Internet today. For the moment, we'll sweep
* this under the carpet.
*
* The conservative default might not actually be a problem
* if the only case this occurs is when sending an initial
* SYN with options and data to a host we've never talked
* to before. Then, they will reply with an MSS value which
* will get recorded and the new parameters should get
* recomputed. For Further Study.
*/
}
mss = min(mss, offer);
/*
* Sanity check: make sure that maxopd will be large
* enough to allow some data on segments even if the
* all the option space is used (40bytes). Otherwise
* funny things may happen in tcp_output.
*/
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;
/*
* origoffer==-1 indicates that no segments were received yet.
* In this case we just guess.
*/
if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
(origoffer == -1 ||
(tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
mss -= TCPOLEN_TSTAMP_APPA;
#if (MCLBYTES & (MCLBYTES - 1)) == 0
if (mss > MCLBYTES)
mss &= ~(MCLBYTES-1);
#else
if (mss > MCLBYTES)
mss = mss / MCLBYTES * MCLBYTES;
#endif
tp->t_maxseg = mss;
}
void
tcp_mss(struct tcpcb *tp, int offer)
{
int rtt, mss;
u_long bufsize;
struct inpcb *inp;
struct socket *so;
struct hc_metrics_lite metrics;
int mtuflags = 0;
#ifdef INET6
int isipv6;
#endif
KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
tcp_mss_update(tp, offer, &metrics, &mtuflags);
mss = tp->t_maxseg;
inp = tp->t_inpcb;
#ifdef INET6
isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
#endif
/*
* If there's a pipesize, change the socket buffer to that size,
* don't change if sb_hiwat is different than default (then it
* has been changed on purpose with setsockopt).
* Make the socket buffers an integral number of mss units;
* if the mss is larger than the socket buffer, decrease the mss.
*/
so = inp->inp_socket;
SOCKBUF_LOCK(&so->so_snd);
if ((so->so_snd.sb_hiwat == tcp_sendspace) && metrics.rmx_sendpipe)
bufsize = metrics.rmx_sendpipe;
else
bufsize = so->so_snd.sb_hiwat;
if (bufsize < mss)
mss = bufsize;
else {
bufsize = roundup(bufsize, mss);
if (bufsize > sb_max)
bufsize = sb_max;
if (bufsize > so->so_snd.sb_hiwat)
(void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
}
SOCKBUF_UNLOCK(&so->so_snd);
tp->t_maxseg = mss;
SOCKBUF_LOCK(&so->so_rcv);
if ((so->so_rcv.sb_hiwat == tcp_recvspace) && metrics.rmx_recvpipe)
bufsize = metrics.rmx_recvpipe;
else
bufsize = so->so_rcv.sb_hiwat;
if (bufsize > mss) {
bufsize = roundup(bufsize, mss);
if (bufsize > sb_max)
bufsize = sb_max;
if (bufsize > so->so_rcv.sb_hiwat)
(void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
}
SOCKBUF_UNLOCK(&so->so_rcv);
/*
* While we're here, check the others too.
*/
if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
tp->t_srtt = rtt;
tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
TCPSTAT_INC(tcps_usedrtt);
if (metrics.rmx_rttvar) {
tp->t_rttvar = metrics.rmx_rttvar;
TCPSTAT_INC(tcps_usedrttvar);
} else {
/* default variation is +- 1 rtt */
tp->t_rttvar =
tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
}
TCPT_RANGESET(tp->t_rxtcur,
((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
tp->t_rttmin, TCPTV_REXMTMAX);
}
if (metrics.rmx_ssthresh) {
/*
* There's some sort of gateway or interface
* buffer limit on the path. Use this to set
* the slow start threshhold, but set the
* threshold to no less than 2*mss.
*/
tp->snd_ssthresh = max(2 * mss, metrics.rmx_ssthresh);
TCPSTAT_INC(tcps_usedssthresh);
}
if (metrics.rmx_bandwidth)
tp->snd_bandwidth = metrics.rmx_bandwidth;
/*
* Set the slow-start flight size depending on whether this
* is a local network or not.
*
* Extend this so we cache the cwnd too and retrieve it here.
* Make cwnd even bigger than RFC3390 suggests but only if we
* have previous experience with the remote host. Be careful
* not make cwnd bigger than remote receive window or our own
* send socket buffer. Maybe put some additional upper bound
* on the retrieved cwnd. Should do incremental updates to
* hostcache when cwnd collapses so next connection doesn't
* overloads the path again.
*
* RFC3390 says only do this if SYN or SYN/ACK didn't got lost.
* We currently check only in syncache_socket for that.
*/
#define TCP_METRICS_CWND
#ifdef TCP_METRICS_CWND
if (metrics.rmx_cwnd)
tp->snd_cwnd = max(mss,
min(metrics.rmx_cwnd / 2,
min(tp->snd_wnd, so->so_snd.sb_hiwat)));
else
#endif
if (V_tcp_do_rfc3390)
tp->snd_cwnd = min(4 * mss, max(2 * mss, 4380));
#ifdef INET6
else if ((isipv6 && in6_localaddr(&inp->in6p_faddr)) ||
(!isipv6 && in_localaddr(inp->inp_faddr)))
#else
else if (in_localaddr(inp->inp_faddr))
#endif
tp->snd_cwnd = mss * V_ss_fltsz_local;
else
tp->snd_cwnd = mss * V_ss_fltsz;
/* Check the interface for TSO capabilities. */
if (mtuflags & CSUM_TSO)
tp->t_flags |= TF_TSO;
}
/*
* Determine the MSS option to send on an outgoing SYN.
*/
int
tcp_mssopt(struct in_conninfo *inc)
{
int mss = 0;
u_long maxmtu = 0;
u_long thcmtu = 0;
size_t min_protoh;
KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
#ifdef INET6
if (inc->inc_flags & INC_ISIPV6) {
mss = V_tcp_v6mssdflt;
maxmtu = tcp_maxmtu6(inc, NULL);
thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
} else
#endif
{
mss = V_tcp_mssdflt;
maxmtu = tcp_maxmtu(inc, NULL);
thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
min_protoh = sizeof(struct tcpiphdr);
}
if (maxmtu && thcmtu)
mss = min(maxmtu, thcmtu) - min_protoh;
else if (maxmtu || thcmtu)
mss = max(maxmtu, thcmtu) - min_protoh;
return (mss);
}
/*
* On a partial ack arrives, force the retransmission of the
* next unacknowledged segment. Do not clear tp->t_dupacks.
* By setting snd_nxt to ti_ack, this forces retransmission timer to
* be started again.
*/
static void
tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
{
tcp_seq onxt = tp->snd_nxt;
u_long ocwnd = tp->snd_cwnd;
INP_WLOCK_ASSERT(tp->t_inpcb);
tcp_timer_activate(tp, TT_REXMT, 0);
tp->t_rtttime = 0;
tp->snd_nxt = th->th_ack;
/*
* Set snd_cwnd to one segment beyond acknowledged offset.
* (tp->snd_una has not yet been updated when this function is called.)
*/
tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una);
tp->t_flags |= TF_ACKNOW;
(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;
}
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