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623dce13c6
freebsd-dev/sys/netinet/tcp_input.c
Robert Watson 623dce13c6 Update TCP for infrastructural changes to the socket/pcb refcount model, 
pru_abort(), pru_detach(), and in_pcbdetach():

- Universally support and enforce the invariant that so_pcb is
  never NULL, converting dozens of unnecessary NULL checks into
  assertions, and eliminating dozens of unnecessary error handling
  cases in protocol code.

- In some cases, eliminate unnecessary pcbinfo locking, as it is no
  longer required to ensure so_pcb != NULL.  For example, the receive
  code no longer requires the pcbinfo lock, and the send code only
  requires it if building a new connection on an otherwise unconnected
  socket triggered via sendto() with an address.  This should
  significnatly reduce tcbinfo lock contention in the receive and send
  cases.

- In order to support the invariant that so_pcb != NULL, it is now
  necessary for the TCP code to not discard the tcpcb any time a
  connection is dropped, but instead leave the tcpcb until the socket
  is shutdown.  This case is handled by setting INP_DROPPED, to
  substitute for using a NULL so_pcb to indicate that the connection
  has been dropped.  This requires the inpcb lock, but not the pcbinfo
  lock.

- Unlike all other protocols in the tree, TCP may need to retain access
  to the socket after the file descriptor has been closed.  Set
  SS_PROTOREF in tcp_detach() in order to prevent the socket from being
  freed, and add a flag, INP_SOCKREF, so that the TCP code knows whether
  or not it needs to free the socket when the connection finally does
  close.  The typical case where this occurs is if close() is called on
  a TCP socket before all sent data in the send socket buffer has been
  transmitted or acknowledged.  If INP_SOCKREF is found when the
  connection is dropped, we release the inpcb, tcpcb, and socket instead
  of flagging INP_DROPPED.

- Abort and detach protocol switch methods no longer return failures,
  nor attempt to free sockets, as the socket layer does this.

- Annotate the existence of a long-standing race in the TCP timer code,
  in which timers are stopped but not drained when the socket is freed,
  as waiting for drain may lead to deadlocks, or have to occur in a
  context where waiting is not permitted.  This race has been handled
  by testing to see if the tcpcb pointer in the inpcb is NULL (and vice
  versa), which is not normally permitted, but may be true of a inpcb
  and tcpcb have been freed.  Add a counter to test how often this race
  has actually occurred, and a large comment for each instance where
  we compare potentially freed memory with NULL.  This will have to be
  fixed in the near future, but requires is to further address how to
  handle the timer shutdown shutdown issue.

- Several TCP calls no longer potentially free the passed inpcb/tcpcb,
  so no longer need to return a pointer to indicate whether the argument
  passed in is still valid.

- Un-macroize debugging and locking setup for various protocol switch
  methods for TCP, as it lead to more obscurity, and as locking becomes
  more customized to the methods, offers less benefit.

- Assert copyright on tcp_usrreq.c due to significant modifications that
  have been made as part of this work.

These changes significantly modify the memory management and connection
logic of our TCP implementation, and are (as such) High Risk Changes,
and likely to contain serious bugs.  Please report problems to the
current@ mailing list ASAP, ideally with simple test cases, and
optionally, packet traces.

MFC after:	3 months
2006-04-01 16:36:36 +00:00

3271 lines
91 KiB
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Raw Blame History

/*-
* 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
* $FreeBSD$
*/
#include "opt_ipfw.h" /* for ipfw_fwd */
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_ipsec.h"
#include "opt_mac.h"
#include "opt_tcpdebug.h"
#include "opt_tcp_input.h"
#include "opt_tcp_sack.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/mac.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 <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>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif /* TCPDEBUG */
#ifdef FAST_IPSEC
#include <netipsec/ipsec.h>
#include <netipsec/ipsec6.h>
#endif /*FAST_IPSEC*/
#ifdef IPSEC
#include <netinet6/ipsec.h>
#include <netinet6/ipsec6.h>
#include <netkey/key.h>
#endif /*IPSEC*/
#include <machine/in_cksum.h>
static const int tcprexmtthresh = 3;
struct tcpstat tcpstat;
SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW,
&tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
static int log_in_vain = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
&log_in_vain, 0, "Log all incoming TCP connections");
static int blackhole = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW,
&blackhole, 0, "Do not send RST when dropping refused connections");
int tcp_delack_enabled = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW,
&tcp_delack_enabled, 0,
"Delay ACK to try and piggyback it onto a data packet");
#ifdef TCP_DROP_SYNFIN
static int drop_synfin = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW,
&drop_synfin, 0, "Drop TCP packets with SYN+FIN set");
#endif
static int tcp_do_rfc3042 = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW,
&tcp_do_rfc3042, 0, "Enable RFC 3042 (Limited Transmit)");
static int tcp_do_rfc3390 = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW,
&tcp_do_rfc3390, 0,
"Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
static int tcp_insecure_rst = 0;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW,
&tcp_insecure_rst, 0,
"Follow the old (insecure) criteria for accepting RST packets.");
SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
"TCP Segment Reassembly Queue");
static int tcp_reass_maxseg = 0;
SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RDTUN,
&tcp_reass_maxseg, 0,
"Global maximum number of TCP Segments in Reassembly Queue");
int tcp_reass_qsize = 0;
SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD,
&tcp_reass_qsize, 0,
"Global number of TCP Segments currently in Reassembly Queue");
static int tcp_reass_maxqlen = 48;
SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxqlen, CTLFLAG_RW,
&tcp_reass_maxqlen, 0,
"Maximum number of TCP Segments per individual Reassembly Queue");
static int tcp_reass_overflows = 0;
SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD,
&tcp_reass_overflows, 0,
"Global number of TCP Segment Reassembly Queue Overflows");
struct inpcbhead tcb;
#define tcb6 tcb /* for KAME src sync over BSD*'s */
struct inpcbinfo tcbinfo;
struct mtx *tcbinfo_mtx;
static void tcp_dooptions(struct tcpopt *, u_char *, int, int);
static void tcp_pulloutofband(struct socket *,
struct tcphdr *, struct mbuf *, int);
static int tcp_reass(struct tcpcb *, struct tcphdr *, int *,
struct mbuf *);
static void tcp_xmit_timer(struct tcpcb *, int);
static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
static int tcp_timewait(struct tcptw *, struct tcpopt *,
struct tcphdr *, struct mbuf *, int);
/* 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) \
((!callout_active(tp->tt_delack) && \
(tp->t_flags & TF_RXWIN0SENT) == 0) && \
(tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
/* Initialize TCP reassembly queue */
uma_zone_t tcp_reass_zone;
void
tcp_reass_init()
{
tcp_reass_maxseg = nmbclusters / 16;
TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
&tcp_reass_maxseg);
tcp_reass_zone = uma_zcreate("tcpreass", sizeof (struct tseg_qent),
NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
uma_zone_set_max(tcp_reass_zone, tcp_reass_maxseg);
}
static int
tcp_reass(tp, th, tlenp, m)
register struct tcpcb *tp;
register struct tcphdr *th;
int *tlenp;
struct mbuf *m;
{
struct tseg_qent *q;
struct tseg_qent *p = NULL;
struct tseg_qent *nq;
struct tseg_qent *te = NULL;
struct socket *so = tp->t_inpcb->inp_socket;
int flags;
INP_LOCK_ASSERT(tp->t_inpcb);
/*
* XXX: tcp_reass() is rather inefficient with its data structures
* and should be rewritten (see NetBSD for optimizations). While
* doing that it should move to its own file tcp_reass.c.
*/
/*
* Call with th==NULL after become established to
* force pre-ESTABLISHED data up to user socket.
*/
if (th == NULL)
goto present;
/*
* Limit the number of segments in the reassembly queue to prevent
* holding on to too many segments (and thus running out of mbufs).
* Make sure to let the missing segment through which caused this
* queue. Always keep one global queue entry spare to be able to
* process the missing segment.
*/
if (th->th_seq != tp->rcv_nxt &&
(tcp_reass_qsize + 1 >= tcp_reass_maxseg ||
tp->t_segqlen >= tcp_reass_maxqlen)) {
tcp_reass_overflows++;
tcpstat.tcps_rcvmemdrop++;
m_freem(m);
*tlenp = 0;
return (0);
}
/*
* Allocate a new queue entry. If we can't, or hit the zone limit
* just drop the pkt.
*/
te = uma_zalloc(tcp_reass_zone, M_NOWAIT);
if (te == NULL) {
tcpstat.tcps_rcvmemdrop++;
m_freem(m);
*tlenp = 0;
return (0);
}
tp->t_segqlen++;
tcp_reass_qsize++;
/*
* Find a segment which begins after this one does.
*/
LIST_FOREACH(q, &tp->t_segq, tqe_q) {
if (SEQ_GT(q->tqe_th->th_seq, th->th_seq))
break;
p = q;
}
/*
* If there is a preceding segment, it may provide some of
* our data already. If so, drop the data from the incoming
* segment. If it provides all of our data, drop us.
*/
if (p != NULL) {
register int i;
/* conversion to int (in i) handles seq wraparound */
i = p->tqe_th->th_seq + p->tqe_len - th->th_seq;
if (i > 0) {
if (i >= *tlenp) {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += *tlenp;
m_freem(m);
uma_zfree(tcp_reass_zone, te);
tp->t_segqlen--;
tcp_reass_qsize--;
/*
* Try to present any queued data
* at the left window edge to the user.
* This is needed after the 3-WHS
* completes.
*/
goto present; /* ??? */
}
m_adj(m, i);
*tlenp -= i;
th->th_seq += i;
}
}
tcpstat.tcps_rcvoopack++;
tcpstat.tcps_rcvoobyte += *tlenp;
/*
* While we overlap succeeding segments trim them or,
* if they are completely covered, dequeue them.
*/
while (q) {
register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq;
if (i <= 0)
break;
if (i < q->tqe_len) {
q->tqe_th->th_seq += i;
q->tqe_len -= i;
m_adj(q->tqe_m, i);
break;
}
nq = LIST_NEXT(q, tqe_q);
LIST_REMOVE(q, tqe_q);
m_freem(q->tqe_m);
uma_zfree(tcp_reass_zone, q);
tp->t_segqlen--;
tcp_reass_qsize--;
q = nq;
}
/* Insert the new segment queue entry into place. */
te->tqe_m = m;
te->tqe_th = th;
te->tqe_len = *tlenp;
if (p == NULL) {
LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q);
} else {
LIST_INSERT_AFTER(p, te, tqe_q);
}
present:
/*
* Present data to user, advancing rcv_nxt through
* completed sequence space.
*/
if (!TCPS_HAVEESTABLISHED(tp->t_state))
return (0);
q = LIST_FIRST(&tp->t_segq);
if (!q || q->tqe_th->th_seq != tp->rcv_nxt)
return (0);
SOCKBUF_LOCK(&so->so_rcv);
do {
tp->rcv_nxt += q->tqe_len;
flags = q->tqe_th->th_flags & TH_FIN;
nq = LIST_NEXT(q, tqe_q);
LIST_REMOVE(q, tqe_q);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
m_freem(q->tqe_m);
else
sbappendstream_locked(&so->so_rcv, q->tqe_m);
uma_zfree(tcp_reass_zone, q);
tp->t_segqlen--;
tcp_reass_qsize--;
q = nq;
} while (q && q->tqe_th->th_seq == tp->rcv_nxt);
ND6_HINT(tp);
sorwakeup_locked(so);
return (flags);
}
/*
* TCP input routine, follows pages 65-76 of the
* protocol specification dated September, 1981 very closely.
*/
#ifdef INET6
int
tcp6_input(mp, offp, proto)
struct mbuf **mp;
int *offp, proto;
{
register 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;
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(m, off0)
register struct mbuf *m;
int off0;
{
register struct tcphdr *th;
register struct ip *ip = NULL;
register struct ipovly *ipov;
register struct inpcb *inp = NULL;
u_char *optp = NULL;
int optlen = 0;
int len, tlen, off;
int drop_hdrlen;
register struct tcpcb *tp = 0;
register int thflags;
struct socket *so = 0;
int todrop, acked, ourfinisacked, needoutput = 0;
u_long tiwin;
struct tcpopt to; /* options in this segment */
int headlocked = 0;
#ifdef IPFIREWALL_FORWARD
struct m_tag *fwd_tag;
#endif
int rstreason; /* For badport_bandlim accounting purposes */
struct ip6_hdr *ip6 = NULL;
#ifdef INET6
int isipv6;
#else
const int isipv6 = 0;
#endif
#ifdef TCPDEBUG
/*
* The size of tcp_saveipgen must be the size of the max ip header,
* now IPv6.
*/
u_char tcp_saveipgen[40];
struct tcphdr tcp_savetcp;
short ostate = 0;
#endif
#ifdef INET6
isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
#endif
bzero((char *)&to, sizeof(to));
tcpstat.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.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))) == 0) {
tcpstat.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.tcps_rcvbadsum++;
goto drop;
}
#ifdef INET6
/* Re-initialization for later version check */
ip->ip_v = IPVERSION;
#endif
}
/*
* Check that TCP offset makes sense,
* pull out TCP options and adjust length. XXX
*/
off = th->th_off << 2;
if (off < sizeof (struct tcphdr) || off > tlen) {
tcpstat.tcps_rcvbadoff++;
goto drop;
}
tlen -= off; /* 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))
== 0) {
tcpstat.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;
#ifdef TCP_DROP_SYNFIN
/*
* If the drop_synfin option is enabled, drop all packets with
* both the SYN and FIN bits set. This prevents e.g. nmap from
* identifying the TCP/IP stack.
*
* This is a violation of the TCP specification.
*/
if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN))
goto drop;
#endif
/*
* 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,
* until after ip6_savecontrol() is called and before other functions
* which don't want those proto headers.
* Because ip6_savecontrol() is going to parse the mbuf to
* search for data to be passed up to user-land, it wants mbuf
* parameters to be unchanged.
* XXX: the call of ip6_savecontrol() has been obsoleted based on
* latest version of the advanced API (20020110).
*/
drop_hdrlen = off0 + off;
/*
* Locate pcb for segment.
*/
INP_INFO_WLOCK(&tcbinfo);
headlocked = 1;
findpcb:
KASSERT(headlocked, ("tcp_input: findpcb: head not locked"));
#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(&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(&tcbinfo,
ip->ip_src, th->th_sport,
next_hop->sin_addr,
next_hop->sin_port ?
ntohs(next_hop->sin_port) :
th->th_dport,
1, 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(&tcbinfo,
&ip6->ip6_src, th->th_sport,
&ip6->ip6_dst, th->th_dport,
1, m->m_pkthdr.rcvif);
#endif
} else
inp = in_pcblookup_hash(&tcbinfo,
ip->ip_src, th->th_sport,
ip->ip_dst, th->th_dport,
1, m->m_pkthdr.rcvif);
#ifdef IPFIREWALL_FORWARD
}
#endif /* IPFIREWALL_FORWARD */
#if defined(IPSEC) || defined(FAST_IPSEC)
#ifdef INET6
if (isipv6) {
if (inp != NULL && ipsec6_in_reject(m, inp)) {
#ifdef IPSEC
ipsec6stat.in_polvio++;
#endif
goto drop;
}
} else
#endif /* INET6 */
if (inp != NULL && ipsec4_in_reject(m, inp)) {
#ifdef IPSEC
ipsecstat.in_polvio++;
#endif
goto drop;
}
#endif /*IPSEC || FAST_IPSEC*/
/*
* If the state is CLOSED (i.e., TCB does not exist) then
* all data in the incoming segment is discarded.
* If the TCB exists but is in CLOSED state, it is embryonic,
* but should either do a listen or a connect soon.
*/
if (inp == NULL) {
if (log_in_vain) {
#ifdef INET6
char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2];
#else
char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"];
#endif
if (isipv6) {
#ifdef INET6
strcpy(dbuf, "[");
strcpy(sbuf, "[");
strcat(dbuf, ip6_sprintf(&ip6->ip6_dst));
strcat(sbuf, ip6_sprintf(&ip6->ip6_src));
strcat(dbuf, "]");
strcat(sbuf, "]");
#endif
} else {
strcpy(dbuf, inet_ntoa(ip->ip_dst));
strcpy(sbuf, inet_ntoa(ip->ip_src));
}
switch (log_in_vain) {
case 1:
if ((thflags & TH_SYN) == 0)
break;
/* FALLTHROUGH */
case 2:
log(LOG_INFO,
"Connection attempt to TCP %s:%d "
"from %s:%d flags:0x%02x\n",
dbuf, ntohs(th->th_dport), sbuf,
ntohs(th->th_sport), thflags);
break;
default:
break;
}
}
if (blackhole) {
switch (blackhole) {
case 1:
if (thflags & TH_SYN)
goto drop;
break;
case 2:
goto drop;
default:
goto drop;
}
}
rstreason = BANDLIM_RST_CLOSEDPORT;
goto dropwithreset;
}
INP_LOCK(inp);
/* Check the minimum TTL for socket. */
if (inp->inp_ip_minttl != 0) {
#ifdef INET6
if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
goto drop;
else
#endif
if (inp->inp_ip_minttl > ip->ip_ttl)
goto drop;
}
if (inp->inp_vflag & INP_TIMEWAIT) {
/*
* The only option of relevance is TOF_CC, and only if
* present in a SYN segment. See tcp_timewait().
*/
if (thflags & TH_SYN)
tcp_dooptions(&to, optp, optlen, 1);
if (tcp_timewait((struct tcptw *)inp->inp_ppcb,
&to, th, m, tlen))
goto findpcb;
/*
* tcp_timewait unlocks inp.
*/
INP_INFO_WUNLOCK(&tcbinfo);
return;
}
tp = intotcpcb(inp);
if (tp == 0) {
INP_UNLOCK(inp);
rstreason = BANDLIM_RST_CLOSEDPORT;
goto dropwithreset;
}
if (tp->t_state == TCPS_CLOSED)
goto drop;
#ifdef MAC
INP_LOCK_ASSERT(inp);
if (mac_check_inpcb_deliver(inp, m))
goto drop;
#endif
so = inp->inp_socket;
KASSERT(so != NULL, ("tcp_input: so == NULL"));
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG) {
ostate = tp->t_state;
if (isipv6)
bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
else
bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
tcp_savetcp = *th;
}
#endif
if (so->so_options & SO_ACCEPTCONN) {
struct in_conninfo inc;
#ifdef INET6
inc.inc_isipv6 = isipv6;
#endif
if (isipv6) {
inc.inc6_faddr = ip6->ip6_src;
inc.inc6_laddr = ip6->ip6_dst;
} else {
inc.inc_faddr = ip->ip_src;
inc.inc_laddr = ip->ip_dst;
}
inc.inc_fport = th->th_sport;
inc.inc_lport = th->th_dport;
/*
* If the state is LISTEN then ignore segment if it contains
* a RST. If the segment contains an ACK then it is bad and
* send a RST. If it does not contain a SYN then it is not
* interesting; drop it.
*
* If the state is SYN_RECEIVED (syncache) and seg contains
* an ACK, but not for our SYN/ACK, send a RST. If the seg
* contains a RST, check the sequence number to see if it
* is a valid reset segment.
*/
if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
if (!syncache_expand(&inc, th, &so, m)) {
/*
* No syncache entry, or ACK was not
* for our SYN/ACK. Send a RST.
*/
tcpstat.tcps_badsyn++;
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
if (so == NULL) {
/*
* Could not complete 3-way handshake,
* connection is being closed down, and
* syncache has free'd mbuf.
*/
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
return;
}
/*
* Socket is created in state SYN_RECEIVED.
* Continue processing segment.
*/
INP_UNLOCK(inp);
inp = sotoinpcb(so);
INP_LOCK(inp);
tp = intotcpcb(inp);
/*
* This is what would have happened in
* tcp_output() when the SYN,ACK was sent.
*/
tp->snd_up = tp->snd_una;
tp->snd_max = tp->snd_nxt = tp->iss + 1;
tp->last_ack_sent = tp->rcv_nxt;
goto after_listen;
}
if (thflags & TH_RST) {
syncache_chkrst(&inc, th);
goto drop;
}
if (thflags & TH_ACK) {
syncache_badack(&inc);
tcpstat.tcps_badsyn++;
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
goto drop;
}
/*
* Segment's flags are (SYN) or (SYN|FIN).
*/
#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 && !ip6_use_deprecated) {
struct in6_ifaddr *ia6;
if ((ia6 = ip6_getdstifaddr(m)) &&
(ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
INP_UNLOCK(inp);
tp = NULL;
rstreason = BANDLIM_RST_OPENPORT;
goto dropwithreset;
}
}
#endif
/*
* If it is from this socket, drop it, it must be forged.
* Don't bother responding if the destination was a broadcast.
*/
if (th->th_dport == th->th_sport) {
if (isipv6) {
if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst,
&ip6->ip6_src))
goto drop;
} else {
if (ip->ip_dst.s_addr == ip->ip_src.s_addr)
goto drop;
}
}
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
*
* 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))
goto drop;
if (isipv6) {
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
goto drop;
} else {
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;
}
/*
* SYN appears to be valid; create compressed TCP state
* for syncache, or perform t/tcp connection.
*/
if (so->so_qlen <= so->so_qlimit) {
#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, 1);
if (!syncache_add(&inc, &to, th, &so, m))
goto drop;
if (so == NULL) {
/*
* Entry added to syncache, mbuf used to
* send SYN,ACK packet.
*/
KASSERT(headlocked, ("headlocked"));
INP_UNLOCK(inp);
INP_INFO_WUNLOCK(&tcbinfo);
return;
}
/*
* Segment passed TAO tests.
* XXX: Can't happen at the moment.
*/
INP_UNLOCK(inp);
inp = sotoinpcb(so);
INP_LOCK(inp);
tp = intotcpcb(inp);
tp->t_starttime = ticks;
tp->t_state = TCPS_ESTABLISHED;
/*
* T/TCP logic:
* If there is a FIN or if there is data, then
* delay SYN,ACK(SYN) in the hope of piggy-backing
* it on a response segment. Otherwise must send
* ACK now in case the other side is slow starting.
*/
if (thflags & TH_FIN || tlen != 0)
tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
else
tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
tiwin = th->th_win << tp->snd_scale;
tcpstat.tcps_connects++;
soisconnected(so);
goto trimthenstep6;
}
goto drop;
}
after_listen:
KASSERT(headlocked, ("tcp_input: after_listen: head not locked"));
INP_LOCK_ASSERT(inp);
/* Syncache takes care of sockets in the listen state. */
KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN"));
/*
* This is the second part of the MSS DoS prevention code (after
* minmss on the sending side) and it deals with too many too small
* tcp packets in a too short timeframe (1 second).
*
* For every full second we count the number of received packets
* and bytes. If we get a lot of packets per second for this connection
* (tcp_minmssoverload) we take a closer look at it and compute the
* average packet size for the past second. If that is less than
* tcp_minmss we get too many packets with very small payload which
* is not good and burdens our system (and every packet generates
* a wakeup to the process connected to our socket). We can reasonable
* expect this to be small packet DoS attack to exhaust our CPU
* cycles.
*
* Care has to be taken for the minimum packet overload value. This
* value defines the minimum number of packets per second before we
* start to worry. This must not be too low to avoid killing for
* example interactive connections with many small packets like
* telnet or SSH.
*
* Setting either tcp_minmssoverload or tcp_minmss to "0" disables
* this check.
*
* Account for packet if payload packet, skip over ACK, etc.
*/
if (tcp_minmss && tcp_minmssoverload &&
tp->t_state == TCPS_ESTABLISHED && tlen > 0) {
if ((unsigned int)(tp->rcv_second - ticks) < hz) {
tp->rcv_pps++;
tp->rcv_byps += tlen + off;
if (tp->rcv_pps > tcp_minmssoverload) {
if ((tp->rcv_byps / tp->rcv_pps) < tcp_minmss) {
printf("too many small tcp packets from "
"%s:%u, av. %lubyte/packet, "
"dropping connection\n",
#ifdef INET6
isipv6 ?
ip6_sprintf(&inp->inp_inc.inc6_faddr) :
#endif
inet_ntoa(inp->inp_inc.inc_faddr),
inp->inp_inc.inc_fport,
tp->rcv_byps / tp->rcv_pps);
KASSERT(headlocked, ("tcp_input: "
"after_listen: tcp_drop: head "
"not locked"));
tp = tcp_drop(tp, ECONNRESET);
tcpstat.tcps_minmssdrops++;
goto drop;
}
}
} else {
tp->rcv_second = ticks + hz;
tp->rcv_pps = 1;
tp->rcv_byps = tlen + off;
}
}
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
*/
tp->t_rcvtime = ticks;
if (TCPS_HAVEESTABLISHED(tp->t_state))
callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp);
/*
* Unscale the window into a 32-bit value.
* This value is bogus for the TCPS_SYN_SENT state
* and is overwritten later.
*/
tiwin = th->th_win << tp->snd_scale;
/*
* Process options only when we get SYN/ACK back. The SYN case
* for incoming connections is handled in tcp_syncache.
* XXX this is traditional behavior, may need to be cleaned up.
*/
tcp_dooptions(&to, optp, optlen, thflags & TH_SYN);
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_requested_s_scale;
tp->snd_wnd = th->th_win << tp->snd_scale;
tiwin = tp->snd_wnd;
}
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->sack_enable) {
if (!(to.to_flags & TOF_SACK))
tp->sack_enable = 0;
else
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 above, it can only
* be TH_NEEDSYN.
*/
if (tp->t_state == TCPS_ESTABLISHED &&
(thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
((to.to_flags & TOF_TS) == 0 ||
TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd &&
tp->snd_nxt == tp->snd_max) {
/*
* If last ACK falls within this segment's sequence numbers,
* record the timestamp.
* 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 &&
((!tcp_do_newreno && !tp->sack_enable &&
tp->t_dupacks < tcprexmtthresh) ||
((tcp_do_newreno || tp->sack_enable) &&
!IN_FASTRECOVERY(tp) && to.to_nsacks == 0 &&
TAILQ_EMPTY(&tp->snd_holes)))) {
KASSERT(headlocked, ("headlocked"));
INP_INFO_WUNLOCK(&tcbinfo);
headlocked = 0;
/*
* this is a pure ack for outstanding data.
*/
++tcpstat.tcps_predack;
/*
* "bad retransmit" recovery
*/
if (tp->t_rxtshift == 1 &&
ticks < tp->t_badrxtwin) {
++tcpstat.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.tcps_rcvackpack++;
tcpstat.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 done */
/*
* 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)
callout_stop(tp->tt_rexmt);
else if (!callout_active(tp->tt_persist))
callout_reset(tp->tt_rexmt,
tp->t_rxtcur,
tcp_timer_rexmt, tp);
sowwakeup(so);
if (so->so_snd.sb_cc)
(void) tcp_output(tp);
goto check_delack;
}
} else if (th->th_ack == tp->snd_una &&
LIST_EMPTY(&tp->t_segq) &&
tlen <= sbspace(&so->so_rcv)) {
KASSERT(headlocked, ("headlocked"));
INP_INFO_WUNLOCK(&tcbinfo);
headlocked = 0;
/*
* this is a pure, in-sequence data packet
* with nothing on the reassembly queue and
* we have enough buffer space to take it.
*/
/* Clean receiver SACK report if present */
if (tp->sack_enable && tp->rcv_numsacks)
tcp_clean_sackreport(tp);
++tcpstat.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.tcps_rcvpack++;
tcpstat.tcps_rcvbyte += tlen;
ND6_HINT(tp); /* some progress has been done */
/*
#ifdef TCPDEBUG
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp,
(void *)tcp_saveipgen, &tcp_savetcp, 0);
#endif
* Add data to socket buffer.
*/
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
m_freem(m);
} else {
m_adj(m, drop_hdrlen); /* delayed header drop */
sbappendstream_locked(&so->so_rcv, m);
}
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.
*/
{ int win;
win = sbspace(&so->so_rcv);
if (win < 0)
win = 0;
tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
}
switch (tp->t_state) {
/*
* If the state is SYN_RECEIVED:
* if seg contains 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 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_RST) {
if (thflags & TH_ACK) {
KASSERT(headlocked, ("tcp_input: after_listen"
": tcp_drop.2: head not locked"));
tp = tcp_drop(tp, ECONNREFUSED);
}
goto drop;
}
if ((thflags & TH_SYN) == 0)
goto drop;
/* Initial send window, already scaled. */
tp->snd_wnd = th->th_win;
tp->irs = th->th_seq;
tcp_rcvseqinit(tp);
if (thflags & TH_ACK) {
tcpstat.tcps_connects++;
soisconnected(so);
#ifdef MAC
SOCK_LOCK(so);
mac_set_socket_peer_from_mbuf(m, so);
SOCK_UNLOCK(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)
callout_reset(tp->tt_delack, tcp_delacktime,
tcp_timer_delack, tp);
else
tp->t_flags |= TF_ACKNOW;
/*
* 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;
callout_reset(tp->tt_keep, tcp_keepidle,
tcp_timer_keep, tp);
}
} 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);
callout_stop(tp->tt_rexmt);
tp->t_state = TCPS_SYN_RECEIVED;
}
trimthenstep6:
KASSERT(headlocked, ("tcp_input: trimthenstep6: head not "
"locked"));
INP_LOCK_ASSERT(inp);
/*
* 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.tcps_rcvpackafterwin++;
tcpstat.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:
case TCPS_TIME_WAIT:
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
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 intial 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) &&
SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
(tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
switch (tp->t_state) {
case TCPS_SYN_RECEIVED:
so->so_error = ECONNREFUSED;
goto close;
case TCPS_ESTABLISHED:
if (tp->last_ack_sent != th->th_seq &&
tcp_insecure_rst == 0) {
tcpstat.tcps_badrst++;
goto drop;
}
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
so->so_error = ECONNRESET;
close:
tp->t_state = TCPS_CLOSED;
tcpstat.tcps_drops++;
KASSERT(headlocked, ("tcp_input: "
"trimthenstep6: tcp_close: head not "
"locked"));
tp = tcp_close(tp);
break;
case TCPS_CLOSING:
case TCPS_LAST_ACK:
KASSERT(headlocked, ("trimthenstep6: "
"tcp_close.2: head not locked"));
tp = tcp_close(tp);
break;
case TCPS_TIME_WAIT:
KASSERT(tp->t_state != TCPS_TIME_WAIT,
("timewait"));
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 ((int)(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.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += tlen;
tcpstat.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 (thflags & TH_SYN) {
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.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += todrop;
} else {
tcpstat.tcps_rcvpartduppack++;
tcpstat.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) {
KASSERT(headlocked, ("trimthenstep6: tcp_close.3: head not "
"locked"));
tp = tcp_close(tp);
tcpstat.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.tcps_rcvpackafterwin++;
if (todrop >= tlen) {
tcpstat.tcps_rcvbyteafterwin += tlen;
/*
* If a new connection request is received
* while in TIME_WAIT, drop the old connection
* and start over if the sequence numbers
* are above the previous ones.
*/
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
if (thflags & TH_SYN &&
tp->t_state == TCPS_TIME_WAIT &&
SEQ_GT(th->th_seq, tp->rcv_nxt)) {
KASSERT(headlocked, ("trimthenstep6: "
"tcp_close.4: head not locked"));
tp = tcp_close(tp);
goto findpcb;
}
/*
* If window is closed can only take segments at
* window edge, and have to drop data and PUSH from
* incoming segments. Continue processing, but
* remember to ack. Otherwise, drop segment
* and ack.
*/
if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_rcvwinprobe++;
} else
goto dropafterack;
} else
tcpstat.tcps_rcvbyteafterwin += todrop;
m_adj(m, -todrop);
tlen -= todrop;
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(headlocked, ("tcp_input: tcp_drop: trimthenstep6: "
"head not locked"));
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
goto drop;
}
/*
* Ack processing.
*/
switch (tp->t_state) {
/*
* In SYN_RECEIVED state, the ack ACKs our SYN, so enter
* ESTABLISHED state and continue processing.
* The ACK was checked above.
*/
case TCPS_SYN_RECEIVED:
tcpstat.tcps_connects++;
soisconnected(so);
/* 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;
callout_reset(tp->tt_keep, tcp_keepidle,
tcp_timer_keep, tp);
}
/*
* 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:
case TCPS_TIME_WAIT:
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
if (SEQ_GT(th->th_ack, tp->snd_max)) {
tcpstat.tcps_rcvacktoomuch++;
goto dropafterack;
}
if (tp->sack_enable &&
(to.to_nsacks > 0 || !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.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.
*/
if (!callout_active(tp->tt_rexmt) ||
th->th_ack != tp->snd_una)
tp->t_dupacks = 0;
else if (++tp->t_dupacks > tcprexmtthresh ||
((tcp_do_newreno || tp->sack_enable) &&
IN_FASTRECOVERY(tp))) {
if (tp->sack_enable && 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;
u_int win;
/*
* 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->sack_enable) {
if (IN_FASTRECOVERY(tp)) {
tp->t_dupacks = 0;
break;
}
} else if (tcp_do_newreno) {
if (SEQ_LEQ(th->th_ack,
tp->snd_recover)) {
tp->t_dupacks = 0;
break;
}
}
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;
callout_stop(tp->tt_rexmt);
tp->t_rtttime = 0;
if (tp->sack_enable) {
tcpstat.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,
("tp->snd_limited too big"));
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 (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,
("dupacks not 1 or 2"));
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),
("sent too much"));
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), ("th_ack <= snd_una"));
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
if (tcp_do_newreno || tp->sack_enable) {
if (IN_FASTRECOVERY(tp)) {
if (SEQ_LT(th->th_ack, tp->snd_recover)) {
if (tp->sack_enable)
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:
KASSERT(headlocked, ("tcp_input: process_ACK: head not "
"locked"));
INP_LOCK_ASSERT(inp);
acked = th->th_ack - tp->snd_una;
tcpstat.tcps_rcvackpack++;
tcpstat.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 && ticks < tp->t_badrxtwin) {
++tcpstat.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) {
callout_stop(tp->tt_rexmt);
needoutput = 1;
} else if (!callout_active(tp->tt_persist))
callout_reset(tp->tt_rexmt, tp->t_rxtcur,
tcp_timer_rexmt, tp);
/*
* 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.
* If the window gives us less than ssthresh packets
* in flight, open exponentially (maxseg per packet).
* Otherwise open linearly: maxseg per window
* (maxseg^2 / cwnd per packet).
*/
if ((!tcp_do_newreno && !tp->sack_enable) ||
!IN_FASTRECOVERY(tp)) {
register u_int cw = tp->snd_cwnd;
register u_int incr = tp->t_maxseg;
if (cw > tp->snd_ssthresh)
incr = incr * incr / cw;
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;
}
sowwakeup_locked(so);
/* detect una wraparound */
if ((tcp_do_newreno || tp->sack_enable) &&
!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 ((tcp_do_newreno || tp->sack_enable) &&
IN_FASTRECOVERY(tp) &&
SEQ_GEQ(th->th_ack, tp->snd_recover))
EXIT_FASTRECOVERY(tp);
tp->snd_una = th->th_ack;
if (tp->sack_enable) {
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) {
soisdisconnected(so);
callout_reset(tp->tt_2msl, tcp_maxidle,
tcp_timer_2msl, tp);
}
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) {
KASSERT(headlocked, ("tcp_input: process_ACK: "
"head not locked"));
tcp_twstart(tp);
INP_INFO_WUNLOCK(&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) {
KASSERT(headlocked, ("tcp_input: process_ACK:"
" tcp_close: head not locked"));
tp = tcp_close(tp);
goto drop;
}
break;
/*
* In TIME_WAIT state the only thing that should arrive
* is a retransmission of the remote FIN. Acknowledge
* it and restart the finack timer.
*/
case TCPS_TIME_WAIT:
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
callout_reset(tp->tt_2msl, 2 * tcp_msl,
tcp_timer_2msl, tp);
goto dropafterack;
}
}
step6:
KASSERT(headlocked, ("tcp_input: step6: head not locked"));
INP_LOCK_ASSERT(inp);
/*
* 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.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 */
KASSERT(headlocked, ("tcp_input: dodata: head not locked"));
INP_LOCK_ASSERT(inp);
/*
* 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;
tcp_seq save_end = th->th_seq + tlen;
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.tcps_rcvpack++;
tcpstat.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);
sorwakeup_locked(so);
} else {
thflags = tcp_reass(tp, th, &tlen, m);
tp->t_flags |= TF_ACKNOW;
}
if (tlen > 0 && tp->sack_enable)
tcp_update_sack_list(tp, save_start, save_end);
/*
* Note the amount of data that peer has sent into
* our window, in order to estimate the sender's
* buffer size.
*/
len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
} 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:
KASSERT(headlocked == 1, ("tcp_input: dodata: "
"TCP_FIN_WAIT_2: head not locked"));
tcp_twstart(tp);
INP_INFO_WUNLOCK(&tcbinfo);
return;
/*
* In TIME_WAIT state restart the 2 MSL time_wait timer.
*/
case TCPS_TIME_WAIT:
KASSERT(tp->t_state != TCPS_TIME_WAIT, ("timewait"));
callout_reset(tp->tt_2msl, 2 * tcp_msl,
tcp_timer_2msl, tp);
break;
}
}
INP_INFO_WUNLOCK(&tcbinfo);
headlocked = 0;
#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(headlocked == 0, ("tcp_input: check_delack: head locked"));
INP_LOCK_ASSERT(inp);
if (tp->t_flags & TF_DELACK) {
tp->t_flags &= ~TF_DELACK;
callout_reset(tp->tt_delack, tcp_delacktime,
tcp_timer_delack, tp);
}
INP_UNLOCK(inp);
return;
dropafterack:
KASSERT(headlocked, ("tcp_input: dropafterack: head not 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
KASSERT(headlocked, ("headlocked should be 1"));
INP_INFO_WUNLOCK(&tcbinfo);
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
INP_UNLOCK(inp);
m_freem(m);
return;
dropwithreset:
KASSERT(headlocked, ("tcp_input: dropwithreset: head not locked"));
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
* Don't bother to respond if destination was broadcast/multicast.
*/
if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
goto drop;
if (isipv6) {
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
goto drop;
} else {
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;
}
/* IPv6 anycast check is done at tcp6_input() */
/*
* Perform bandwidth limiting.
*/
if (badport_bandlim(rstreason) < 0)
goto drop;
#ifdef TCPDEBUG
if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
&tcp_savetcp, 0);
#endif
if (thflags & TH_ACK)
/* mtod() below is safe as long as hdr dropping is delayed */
tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack,
TH_RST);
else {
if (thflags & TH_SYN)
tlen++;
/* mtod() below is safe as long as hdr dropping is delayed */
tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
(tcp_seq)0, TH_RST|TH_ACK);
}
if (tp != NULL)
INP_UNLOCK(inp);
if (headlocked)
INP_INFO_WUNLOCK(&tcbinfo);
return;
drop:
/*
* 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_UNLOCK(inp);
if (headlocked)
INP_INFO_WUNLOCK(&tcbinfo);
m_freem(m);
return;
}
/*
* Parse TCP options and place in tcpopt.
*/
static void
tcp_dooptions(to, cp, cnt, is_syn)
struct tcpopt *to;
u_char *cp;
int cnt;
int is_syn;
{
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 (!is_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 (! is_syn)
continue;
to->to_flags |= TOF_SCALE;
to->to_requested_s_scale = 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);
/*
* If echoed timestamp is later than the current time,
* fall back to non RFC1323 RTT calculation.
*/
if ((to->to_tsecr != 0) && TSTMP_GT(to->to_tsecr, ticks))
to->to_tsecr = 0;
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 | TOF_SIGLEN);
break;
#endif
case TCPOPT_SACK_PERMITTED:
if (!tcp_do_sack ||
optlen != TCPOLEN_SACK_PERMITTED)
continue;
if (is_syn) {
/* MUST only be set on SYN */
to->to_flags |= TOF_SACK;
}
break;
case TCPOPT_SACK:
if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
continue;
to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
to->to_sacks = cp + 2;
tcpstat.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(so, th, m, off)
struct socket *so;
struct tcphdr *th;
register struct mbuf *m;
int off; /* delayed to be droped hdrlen */
{
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);
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 == 0)
break;
}
panic("tcp_pulloutofband");
}
/*
* Collect new round-trip time estimate
* and update averages and current timeout.
*/
static void
tcp_xmit_timer(tp, rtt)
register struct tcpcb *tp;
int rtt;
{
register int delta;
INP_LOCK_ASSERT(tp->t_inpcb);
tcpstat.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(tp, offer)
struct tcpcb *tp;
int offer;
{
int rtt, mss;
u_long bufsize;
u_long maxmtu;
struct inpcb *inp = tp->t_inpcb;
struct socket *so;
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
/* initialize */
#ifdef INET6
if (isipv6) {
maxmtu = tcp_maxmtu6(&inp->inp_inc);
tp->t_maxopd = tp->t_maxseg = tcp_v6mssdflt;
} else
#endif
{
maxmtu = tcp_maxmtu(&inp->inp_inc);
tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
}
so = inp->inp_socket;
/*
* no route to sender, stay with default mss and return
*/
if (maxmtu == 0)
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.
*/
offer =
#ifdef INET6
isipv6 ? tcp_v6mssdflt :
#endif
tcp_mssdflt;
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, tcp_minmss);
/*
* 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.
*/
offer = max(offer, 64);
}
/*
* rmx information is now retrieved from tcp_hostcache
*/
tcp_hc_get(&inp->inp_inc, &metrics);
/*
* 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 (!path_mtu_discovery &&
!in6_localaddr(&inp->in6p_faddr))
mss = min(mss, tcp_v6mssdflt);
} else
#endif
{
mss = maxmtu - min_protoh;
if (!path_mtu_discovery &&
!in_localaddr(inp->inp_faddr))
mss = min(mss, tcp_mssdflt);
}
}
mss = min(mss, offer);
/*
* 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;
tp->t_maxseg = mss;
#if (MCLBYTES & (MCLBYTES - 1)) == 0
if (mss > MCLBYTES)
mss &= ~(MCLBYTES-1);
#else
if (mss > MCLBYTES)
mss = mss / MCLBYTES * MCLBYTES;
#endif
tp->t_maxseg = mss;
/*
* 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.
*/
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.tcps_usedrtt++;
if (metrics.rmx_rttvar) {
tp->t_rttvar = metrics.rmx_rttvar;
tcpstat.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.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 (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 * ss_fltsz_local;
else
tp->snd_cwnd = mss * ss_fltsz;
}
/*
* Determine the MSS option to send on an outgoing SYN.
*/
int
tcp_mssopt(inc)
struct in_conninfo *inc;
{
int mss = 0;
u_long maxmtu = 0;
u_long thcmtu = 0;
size_t min_protoh;
#ifdef INET6
int isipv6 = inc->inc_isipv6 ? 1 : 0;
#endif
KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
#ifdef INET6
if (isipv6) {
mss = tcp_v6mssdflt;
maxmtu = tcp_maxmtu6(inc);
thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
} else
#endif
{
mss = tcp_mssdflt;
maxmtu = tcp_maxmtu(inc);
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(tp, th)
struct tcpcb *tp;
struct tcphdr *th;
{
tcp_seq onxt = tp->snd_nxt;
u_long ocwnd = tp->snd_cwnd;
callout_stop(tp->tt_rexmt);
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;
}
/*
* Returns 1 if the TIME_WAIT state was killed and we should start over,
* looking for a pcb in the listen state. Returns 0 otherwise.
*/
static int
tcp_timewait(tw, to, th, m, tlen)
struct tcptw *tw;
struct tcpopt *to;
struct tcphdr *th;
struct mbuf *m;
int tlen;
{
int thflags;
tcp_seq seq;
#ifdef INET6
int isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
#else
const int isipv6 = 0;
#endif
/* tcbinfo lock required for tcp_twclose(), tcp_2msl_reset. */
INP_INFO_WLOCK_ASSERT(&tcbinfo);
INP_LOCK_ASSERT(tw->tw_inpcb);
thflags = th->th_flags;
/*
* NOTE: for FIN_WAIT_2 (to be added later),
* must validate sequence number before accepting RST
*/
/*
* If the segment contains RST:
* Drop the segment - see Stevens, vol. 2, p. 964 and
* RFC 1337.
*/
if (thflags & TH_RST)
goto drop;
#if 0
/* PAWS not needed at the moment */
/*
* 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)) {
if ((thflags & TH_ACK) == 0)
goto drop;
goto ack;
}
/*
* ts_recent is never updated because we never accept new segments.
*/
#endif
/*
* If a new connection request is received
* while in TIME_WAIT, drop the old connection
* and start over if the sequence numbers
* are above the previous ones.
*/
if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
tcp_twclose(tw, 0);
return (1);
}
/*
* Drop the the segment if it does not contain an ACK.
*/
if ((thflags & TH_ACK) == 0)
goto drop;
/*
* Reset the 2MSL timer if this is a duplicate FIN.
*/
if (thflags & TH_FIN) {
seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
if (seq + 1 == tw->rcv_nxt)
tcp_timer_2msl_reset(tw, 2 * tcp_msl);
}
/*
* Acknowledge the segment if it has data or is not a duplicate ACK.
*/
if (thflags != TH_ACK || tlen != 0 ||
th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
tcp_twrespond(tw, TH_ACK);
goto drop;
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
* Don't bother to respond if destination was broadcast/multicast.
*/
if (m->m_flags & (M_BCAST|M_MCAST))
goto drop;
if (isipv6) {
struct ip6_hdr *ip6;
/* IPv6 anycast check is done at tcp6_input() */
ip6 = mtod(m, struct ip6_hdr *);
if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
goto drop;
} else {
struct ip *ip;
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;
}
if (thflags & TH_ACK) {
tcp_respond(NULL,
mtod(m, void *), th, m, 0, th->th_ack, TH_RST);
} else {
seq = th->th_seq + (thflags & TH_SYN ? 1 : 0);
tcp_respond(NULL,
mtod(m, void *), th, m, seq, 0, TH_RST|TH_ACK);
}
INP_UNLOCK(tw->tw_inpcb);
return (0);
drop:
INP_UNLOCK(tw->tw_inpcb);
m_freem(m);
return (0);
}
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