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NetBSD/sys/netinet/tcp_input.c
thorpej 4ed600dbd0 Fix several annoyances related to MSS handling in BSD TCP: 
- Don't overload t_maxseg.  Previous behavior was to set it to the min
  of the peer's advertised MSS, our advertised MSS, and tcp_mssdflt
  (for non-local networks).  This breaks PMTU discovery running on
  either host.  Instead, remember the MSS we advertise, and use it
  as appropriate (in silly window avoidance).
- Per last bullet, split tcp_mss() into several functions for handling
  MSS (ours and peer's), and performing various tasks when a connection
  becomes ESTABLISHED.
- Introduce a new function, tcp_segsize(), which computes the max size
  for every segment transmitted in tcp_output().  This will eventually
  be used to hook in PMTU discovery.
1997-09-22 21:49:55 +00:00

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/* $NetBSD: tcp_input.c,v 1.32 1997/09/22 21:49:55 thorpej Exp $ */
/*
* Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 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 8.5 (Berkeley) 4/10/94
*/
/*
* TODO list for SYN cache stuff:
*
* (a) The definition of "struct syn_cache" says:
*
* This structure should not exceeed 32 bytes.
*
* but it's 40 bytes on the Alpha. Can reduce memory use one
* of two ways:
*
* (1) Use a dynamically-sized hash table, and handle
* collisions by rehashing. Then sc_next is unnecessary.
*
* (2) Allocate syn_cache structures in pages (or some other
* large chunk). This would probably be desirable for
* maintaining locality of reference anyway.
*
* If you do this, you can change sc_next to a page/index
* value, and make it a 32-bit (or maybe even 16-bit)
* integer, thus partly obviating the need for the previous
* hack.
*
* It's also worth noting this this is necessary for IPv6, as well,
* where we use 32 bytes just for the IP addresses, so eliminating
* wastage is going to become more important. (BTW, has anyone
* integreated these changes with one fo the IPv6 status that are
* available?)
*
* (b) Find room for a "state" field, which is needed to keep a
* compressed state for TIME_WAIT TCBs. It's been noted already
* that this is fairly important for very high-volume web and
* mail servers, which use a large number of short-lived
* connections.
*/
#ifndef TUBA_INCLUDE
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/errno.h>
#include <net/if.h>
#include <net/route.h>
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/ip.h>
#include <netinet/in_pcb.h>
#include <netinet/ip_var.h>
#include <netinet/tcp.h>
#include <netinet/tcp_fsm.h>
#include <netinet/tcp_seq.h>
#include <netinet/tcp_timer.h>
#include <netinet/tcp_var.h>
#include <netinet/tcpip.h>
#include <netinet/tcp_debug.h>
#include <machine/stdarg.h>
int tcprexmtthresh = 3;
struct tcpiphdr tcp_saveti;
extern u_long sb_max;
#endif /* TUBA_INCLUDE */
#define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ)
/* for modulo comparisons of timestamps */
#define TSTMP_LT(a,b) ((int)((a)-(b)) < 0)
#define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0)
/*
* Insert segment ti into reassembly queue of tcp with
* control block tp. Return TH_FIN if reassembly now includes
* a segment with FIN. The macro form does the common case inline
* (segment is the next to be received on an established connection,
* and the queue is empty), avoiding linkage into and removal
* from the queue and repetition of various conversions.
* Set DELACK for segments received in order, but ack immediately
* when segments are out of order (so fast retransmit can work).
*/
#define TCP_REASS(tp, ti, m, so, flags) { \
if ((ti)->ti_seq == (tp)->rcv_nxt && \
(tp)->segq.lh_first == NULL && \
(tp)->t_state == TCPS_ESTABLISHED) { \
if ((ti)->ti_flags & TH_PUSH) \
tp->t_flags |= TF_ACKNOW; \
else \
tp->t_flags |= TF_DELACK; \
(tp)->rcv_nxt += (ti)->ti_len; \
flags = (ti)->ti_flags & TH_FIN; \
tcpstat.tcps_rcvpack++;\
tcpstat.tcps_rcvbyte += (ti)->ti_len;\
sbappend(&(so)->so_rcv, (m)); \
sorwakeup(so); \
} else { \
(flags) = tcp_reass((tp), (ti), (m)); \
tp->t_flags |= TF_ACKNOW; \
} \
}
#ifndef TUBA_INCLUDE
int
tcp_reass(tp, ti, m)
register struct tcpcb *tp;
register struct tcpiphdr *ti;
struct mbuf *m;
{
register struct ipqent *p, *q, *nq, *tiqe;
struct socket *so = tp->t_inpcb->inp_socket;
int flags;
/*
* Call with ti==0 after become established to
* force pre-ESTABLISHED data up to user socket.
*/
if (ti == 0)
goto present;
/*
* Allocate a new queue entry, before we throw away any data.
* If we can't, just drop the packet. XXX
*/
MALLOC(tiqe, struct ipqent *, sizeof (struct ipqent), M_IPQ, M_NOWAIT);
if (tiqe == NULL) {
tcpstat.tcps_rcvmemdrop++;
m_freem(m);
return (0);
}
/*
* Find a segment which begins after this one does.
*/
for (p = NULL, q = tp->segq.lh_first; q != NULL;
p = q, q = q->ipqe_q.le_next)
if (SEQ_GT(q->ipqe_tcp->ti_seq, ti->ti_seq))
break;
/*
* If there is a preceding segment, it may provide some of
* our data already. If so, drop the data from the incoming
* segment. If it provides all of our data, drop us.
*/
if (p != NULL) {
register struct tcpiphdr *phdr = p->ipqe_tcp;
register int i;
/* conversion to int (in i) handles seq wraparound */
i = phdr->ti_seq + phdr->ti_len - ti->ti_seq;
if (i > 0) {
if (i >= ti->ti_len) {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += ti->ti_len;
m_freem(m);
FREE(tiqe, M_IPQ);
return (0);
}
m_adj(m, i);
ti->ti_len -= i;
ti->ti_seq += i;
}
}
tcpstat.tcps_rcvoopack++;
tcpstat.tcps_rcvoobyte += ti->ti_len;
/*
* While we overlap succeeding segments trim them or,
* if they are completely covered, dequeue them.
*/
for (; q != NULL; q = nq) {
register struct tcpiphdr *qhdr = q->ipqe_tcp;
register int i = (ti->ti_seq + ti->ti_len) - qhdr->ti_seq;
if (i <= 0)
break;
if (i < qhdr->ti_len) {
qhdr->ti_seq += i;
qhdr->ti_len -= i;
m_adj(q->ipqe_m, i);
break;
}
nq = q->ipqe_q.le_next;
m_freem(q->ipqe_m);
LIST_REMOVE(q, ipqe_q);
FREE(q, M_IPQ);
}
/* Insert the new fragment queue entry into place. */
tiqe->ipqe_m = m;
tiqe->ipqe_tcp = ti;
if (p == NULL) {
LIST_INSERT_HEAD(&tp->segq, tiqe, ipqe_q);
} else {
LIST_INSERT_AFTER(p, tiqe, ipqe_q);
}
present:
/*
* Present data to user, advancing rcv_nxt through
* completed sequence space.
*/
if (TCPS_HAVEESTABLISHED(tp->t_state) == 0)
return (0);
q = tp->segq.lh_first;
if (q == NULL || q->ipqe_tcp->ti_seq != tp->rcv_nxt)
return (0);
if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_tcp->ti_len)
return (0);
do {
tp->rcv_nxt += q->ipqe_tcp->ti_len;
flags = q->ipqe_tcp->ti_flags & TH_FIN;
nq = q->ipqe_q.le_next;
LIST_REMOVE(q, ipqe_q);
if (so->so_state & SS_CANTRCVMORE)
m_freem(q->ipqe_m);
else
sbappend(&so->so_rcv, q->ipqe_m);
FREE(q, M_IPQ);
q = nq;
} while (q != NULL && q->ipqe_tcp->ti_seq == tp->rcv_nxt);
sorwakeup(so);
return (flags);
}
/*
* TCP input routine, follows pages 65-76 of the
* protocol specification dated September, 1981 very closely.
*/
void
#if __STDC__
tcp_input(struct mbuf *m, ...)
#else
tcp_input(m, va_alist)
register struct mbuf *m;
#endif
{
register struct tcpiphdr *ti;
register struct inpcb *inp;
caddr_t optp = NULL;
int optlen = 0;
int len, tlen, off, hdroptlen;
register struct tcpcb *tp = 0;
register int tiflags;
struct socket *so = NULL;
int todrop, acked, ourfinisacked, needoutput = 0;
short ostate = 0;
int iss = 0;
u_long tiwin;
struct tcp_opt_info opti;
int iphlen;
va_list ap;
va_start(ap, m);
iphlen = va_arg(ap, int);
va_end(ap);
tcpstat.tcps_rcvtotal++;
opti.ts_present = 0;
opti.maxseg = 0;
/*
* Get IP and TCP header together in first mbuf.
* Note: IP leaves IP header in first mbuf.
*/
ti = mtod(m, struct tcpiphdr *);
if (iphlen > sizeof (struct ip))
ip_stripoptions(m, (struct mbuf *)0);
if (m->m_len < sizeof (struct tcpiphdr)) {
if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) {
tcpstat.tcps_rcvshort++;
return;
}
ti = mtod(m, struct tcpiphdr *);
}
/*
* Checksum extended TCP header and data.
*/
tlen = ((struct ip *)ti)->ip_len;
len = sizeof (struct ip) + tlen;
bzero(ti->ti_x1, sizeof ti->ti_x1);
ti->ti_len = (u_int16_t)tlen;
HTONS(ti->ti_len);
if ((ti->ti_sum = in_cksum(m, len)) != 0) {
tcpstat.tcps_rcvbadsum++;
goto drop;
}
#endif /* TUBA_INCLUDE */
/*
* Check that TCP offset makes sense,
* pull out TCP options and adjust length. XXX
*/
off = ti->ti_off << 2;
if (off < sizeof (struct tcphdr) || off > tlen) {
tcpstat.tcps_rcvbadoff++;
goto drop;
}
tlen -= off;
ti->ti_len = tlen;
if (off > sizeof (struct tcphdr)) {
if (m->m_len < sizeof(struct ip) + off) {
if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) {
tcpstat.tcps_rcvshort++;
return;
}
ti = mtod(m, struct tcpiphdr *);
}
optlen = off - sizeof (struct tcphdr);
optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr);
/*
* Do quick retrieval of timestamp options ("options
* prediction?"). If timestamp is the only option and it's
* formatted as recommended in RFC 1323 appendix A, we
* quickly get the values now and not bother calling
* tcp_dooptions(), etc.
*/
if ((optlen == TCPOLEN_TSTAMP_APPA ||
(optlen > TCPOLEN_TSTAMP_APPA &&
optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) &&
*(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) &&
(ti->ti_flags & TH_SYN) == 0) {
opti.ts_present = 1;
opti.ts_val = ntohl(*(u_int32_t *)(optp + 4));
opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8));
optp = NULL; /* we've parsed the options */
}
}
tiflags = ti->ti_flags;
/*
* Convert TCP protocol specific fields to host format.
*/
NTOHL(ti->ti_seq);
NTOHL(ti->ti_ack);
NTOHS(ti->ti_win);
NTOHS(ti->ti_urp);
/*
* Locate pcb for segment.
*/
findpcb:
inp = in_pcblookup_connect(&tcbtable, ti->ti_src, ti->ti_sport,
ti->ti_dst, ti->ti_dport);
if (inp == 0) {
++tcpstat.tcps_pcbhashmiss;
inp = in_pcblookup_bind(&tcbtable, ti->ti_dst, ti->ti_dport);
if (inp == 0) {
++tcpstat.tcps_noport;
goto dropwithreset;
}
}
/*
* 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.
*/
tp = intotcpcb(inp);
if (tp == 0)
goto dropwithreset;
if (tp->t_state == TCPS_CLOSED)
goto drop;
/* Unscale the window into a 32-bit value. */
if ((tiflags & TH_SYN) == 0)
tiwin = ti->ti_win << tp->snd_scale;
else
tiwin = ti->ti_win;
so = inp->inp_socket;
if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) {
if (so->so_options & SO_DEBUG) {
ostate = tp->t_state;
tcp_saveti = *ti;
}
if (so->so_options & SO_ACCEPTCONN) {
if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
if (tiflags & TH_RST)
syn_cache_reset(ti);
else if (tiflags & TH_ACK) {
so = syn_cache_get(so, m);
if (so == NULL) {
/*
* We don't have a SYN for
* this ACK; send an RST.
*/
tcpstat.tcps_badsyn++;
tp = NULL;
goto dropwithreset;
} else if (so ==
(struct socket *)(-1)) {
/*
* We were unable to create
* the connection. If the
* 3-way handshake was
* completeed, and RST has
* been sent to the peer.
* Since the mbuf might be
* in use for the reply,
* do not free it.
*/
m = NULL;
} else {
/*
* We have created a
* full-blown connection.
*/
inp = sotoinpcb(so);
tp = intotcpcb(inp);
tiwin <<= tp->snd_scale;
goto after_listen;
}
}
} else {
/*
* Received a SYN; create compressed
* TCP state for it.
*/
if (so->so_qlen <= so->so_qlimit &&
syn_cache_add(so, m, optp, optlen, &opti))
m = NULL;
}
goto drop;
}
}
after_listen:
#ifdef DIAGNOSTIC
/*
* Should not happen now that all embryonic connections
* are handled with compressed state.
*/
if (tp->t_state == TCPS_LISTEN)
panic("tcp_input: TCPS_LISTEN");
#endif
/*
* Segment received on connection.
* Reset idle time and keep-alive timer.
*/
tp->t_idle = 0;
if (TCPS_HAVEESTABLISHED(tp->t_state))
tp->t_timer[TCPT_KEEP] = tcp_keepidle;
/*
* Process options.
*/
if (optp)
tcp_dooptions(tp, optp, optlen, ti, &opti);
/*
* Header prediction: check for the two common cases
* of a uni-directional data xfer. If the packet has
* no control flags, is in-sequence, the window didn't
* change and we're not retransmitting, it's a
* candidate. If the length is zero and the ack moved
* forward, we're the sender side of the xfer. Just
* free the data acked & wake any higher level process
* that was blocked waiting for space. If the length
* is non-zero and the ack didn't move, we're the
* receiver side. If we're getting packets in-order
* (the reassembly queue is empty), add the data to
* the socket buffer and note that we need a delayed ack.
*/
if (tp->t_state == TCPS_ESTABLISHED &&
(tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
(!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) &&
ti->ti_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.
*/
if (opti.ts_present &&
SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
tp->ts_recent_age = tcp_now;
tp->ts_recent = opti.ts_val;
}
if (ti->ti_len == 0) {
if (SEQ_GT(ti->ti_ack, tp->snd_una) &&
SEQ_LEQ(ti->ti_ack, tp->snd_max) &&
tp->snd_cwnd >= tp->snd_wnd &&
tp->t_dupacks < tcprexmtthresh) {
/*
* this is a pure ack for outstanding data.
*/
++tcpstat.tcps_predack;
if (opti.ts_present)
tcp_xmit_timer(tp,
tcp_now-opti.ts_ecr+1);
else if (tp->t_rtt &&
SEQ_GT(ti->ti_ack, tp->t_rtseq))
tcp_xmit_timer(tp, tp->t_rtt);
acked = ti->ti_ack - tp->snd_una;
tcpstat.tcps_rcvackpack++;
tcpstat.tcps_rcvackbyte += acked;
sbdrop(&so->so_snd, acked);
tp->snd_una = ti->ti_ack;
m_freem(m);
/*
* If all outstanding data are acked, stop
* retransmit timer, otherwise restart timer
* using current (possibly backed-off) value.
* If process is waiting for space,
* wakeup/selwakeup/signal. If data
* are ready to send, let tcp_output
* decide between more output or persist.
*/
if (tp->snd_una == tp->snd_max)
tp->t_timer[TCPT_REXMT] = 0;
else if (tp->t_timer[TCPT_PERSIST] == 0)
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
if (sb_notify(&so->so_snd))
sowwakeup(so);
if (so->so_snd.sb_cc)
(void) tcp_output(tp);
return;
}
} else if (ti->ti_ack == tp->snd_una &&
tp->segq.lh_first == NULL &&
ti->ti_len <= sbspace(&so->so_rcv)) {
/*
* this is a pure, in-sequence data packet
* with nothing on the reassembly queue and
* we have enough buffer space to take it.
*/
++tcpstat.tcps_preddat;
tp->rcv_nxt += ti->ti_len;
tcpstat.tcps_rcvpack++;
tcpstat.tcps_rcvbyte += ti->ti_len;
/*
* Drop TCP, IP headers and TCP options then add data
* to socket buffer.
*/
m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr);
sbappend(&so->so_rcv, m);
sorwakeup(so);
if (ti->ti_flags & TH_PUSH)
tp->t_flags |= TF_ACKNOW;
else
tp->t_flags |= TF_DELACK;
return;
}
}
/*
* Drop TCP, IP headers and TCP options.
*/
hdroptlen = sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr);
m->m_data += hdroptlen;
m->m_len -= hdroptlen;
/*
* 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_SENT:
* if seg contains an ACK, but not for our SYN, drop the input.
* if seg contains a RST, then drop the connection.
* if seg does not contain SYN, then drop it.
* Otherwise this is an acceptable SYN segment
* initialize tp->rcv_nxt and tp->irs
* if seg contains ack then advance tp->snd_una
* if SYN has been acked change to ESTABLISHED else SYN_RCVD state
* arrange for segment to be acked (eventually)
* continue processing rest of data/controls, beginning with URG
*/
case TCPS_SYN_SENT:
if ((tiflags & TH_ACK) &&
(SEQ_LEQ(ti->ti_ack, tp->iss) ||
SEQ_GT(ti->ti_ack, tp->snd_max)))
goto dropwithreset;
if (tiflags & TH_RST) {
if (tiflags & TH_ACK)
tp = tcp_drop(tp, ECONNREFUSED);
goto drop;
}
if ((tiflags & TH_SYN) == 0)
goto drop;
if (tiflags & TH_ACK) {
tp->snd_una = ti->ti_ack;
if (SEQ_LT(tp->snd_nxt, tp->snd_una))
tp->snd_nxt = tp->snd_una;
}
tp->t_timer[TCPT_REXMT] = 0;
tp->irs = ti->ti_seq;
tcp_rcvseqinit(tp);
tp->t_flags |= TF_ACKNOW;
tcp_mss_from_peer(tp, opti.maxseg);
tcp_rmx_rtt(tp);
if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
tcpstat.tcps_connects++;
soisconnected(so);
tcp_established(tp);
/* Do window scaling on this connection? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
(void) tcp_reass(tp, (struct tcpiphdr *)0,
(struct mbuf *)0);
/*
* if we didn't have to retransmit the SYN,
* use its rtt as our initial srtt & rtt var.
*/
if (tp->t_rtt)
tcp_xmit_timer(tp, tp->t_rtt);
} else
tp->t_state = TCPS_SYN_RECEIVED;
/*
* Advance ti->ti_seq to correspond to first data byte.
* If data, trim to stay within window,
* dropping FIN if necessary.
*/
ti->ti_seq++;
if (ti->ti_len > tp->rcv_wnd) {
todrop = ti->ti_len - tp->rcv_wnd;
m_adj(m, -todrop);
ti->ti_len = tp->rcv_wnd;
tiflags &= ~TH_FIN;
tcpstat.tcps_rcvpackafterwin++;
tcpstat.tcps_rcvbyteafterwin += todrop;
}
tp->snd_wl1 = ti->ti_seq - 1;
tp->rcv_up = ti->ti_seq;
goto step6;
/*
* If the state is SYN_RECEIVED:
* If seg contains an ACK, but not for our SYN, drop the input
* and generate an RST. See page 36, rfc793
*/
case TCPS_SYN_RECEIVED:
if ((tiflags & TH_ACK) &&
(SEQ_LEQ(ti->ti_ack, tp->iss) ||
SEQ_GT(ti->ti_ack, tp->snd_max)))
goto dropwithreset;
break;
}
/*
* States other than LISTEN or SYN_SENT.
* First check timestamp, if present.
* Then check that at least some bytes of segment are within
* receive window. If segment begins before rcv_nxt,
* drop leading data (and SYN); if nothing left, just ack.
*
* RFC 1323 PAWS: If we have a timestamp reply on this segment
* and it's less than ts_recent, drop it.
*/
if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
TSTMP_LT(opti.ts_val, tp->ts_recent)) {
/* Check to see if ts_recent is over 24 days old. */
if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
/*
* Invalidate ts_recent. If this segment updates
* ts_recent, the age will be reset later and ts_recent
* will get a valid value. If it does not, setting
* ts_recent to zero will at least satisfy the
* requirement that zero be placed in the timestamp
* echo reply when ts_recent isn't valid. The
* age isn't reset until we get a valid ts_recent
* because we don't want out-of-order segments to be
* dropped when ts_recent is old.
*/
tp->ts_recent = 0;
} else {
tcpstat.tcps_rcvduppack++;
tcpstat.tcps_rcvdupbyte += ti->ti_len;
tcpstat.tcps_pawsdrop++;
goto dropafterack;
}
}
todrop = tp->rcv_nxt - ti->ti_seq;
if (todrop > 0) {
if (tiflags & TH_SYN) {
tiflags &= ~TH_SYN;
ti->ti_seq++;
if (ti->ti_urp > 1)
ti->ti_urp--;
else {
tiflags &= ~TH_URG;
ti->ti_urp = 0;
}
todrop--;
}
if (todrop >= ti->ti_len) {
/*
* Any valid FIN must be to the left of the
* window. At this point, FIN must be a
* duplicate or out-of-sequence, so drop it.
*/
tiflags &= ~TH_FIN;
/*
* Send ACK to resynchronize, and drop any data,
* but keep on processing for RST or ACK.
*/
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_rcvdupbyte += todrop = ti->ti_len;
tcpstat.tcps_rcvduppack++;
} else {
tcpstat.tcps_rcvpartduppack++;
tcpstat.tcps_rcvpartdupbyte += todrop;
}
m_adj(m, todrop);
ti->ti_seq += todrop;
ti->ti_len -= todrop;
if (ti->ti_urp > todrop)
ti->ti_urp -= todrop;
else {
tiflags &= ~TH_URG;
ti->ti_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 && ti->ti_len) {
tp = tcp_close(tp);
tcpstat.tcps_rcvafterclose++;
goto dropwithreset;
}
/*
* If segment ends after window, drop trailing data
* (and PUSH and FIN); if nothing left, just ACK.
*/
todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd);
if (todrop > 0) {
tcpstat.tcps_rcvpackafterwin++;
if (todrop >= ti->ti_len) {
tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
/*
* 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 (tiflags & TH_SYN &&
tp->t_state == TCPS_TIME_WAIT &&
SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
iss = tp->rcv_nxt + TCP_ISSINCR;
tp = tcp_close(tp);
/*
* We have already advanced the mbuf
* pointers past the IP+TCP headers and
* options. Restore those pointers before
* attempting to use the TCP header again.
*/
m->m_data -= hdroptlen;
m->m_len += hdroptlen;
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 && ti->ti_seq == tp->rcv_nxt) {
tp->t_flags |= TF_ACKNOW;
tcpstat.tcps_rcvwinprobe++;
} else
goto dropafterack;
} else
tcpstat.tcps_rcvbyteafterwin += todrop;
m_adj(m, -todrop);
ti->ti_len -= todrop;
tiflags &= ~(TH_PUSH|TH_FIN);
}
/*
* If last ACK falls within this segment's sequence numbers,
* record its timestamp.
*/
if (opti.ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
((tiflags & (TH_SYN|TH_FIN)) != 0))) {
tp->ts_recent_age = tcp_now;
tp->ts_recent = opti.ts_val;
}
/*
* If the RST bit is set examine the state:
* SYN_RECEIVED STATE:
* If passive open, return to LISTEN state.
* If active open, inform user that connection was refused.
* ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
* Inform user that connection was reset, and close tcb.
* CLOSING, LAST_ACK, TIME_WAIT STATES
* Close the tcb.
*/
if (tiflags&TH_RST) switch (tp->t_state) {
case TCPS_SYN_RECEIVED:
so->so_error = ECONNREFUSED;
goto close;
case TCPS_ESTABLISHED:
case TCPS_FIN_WAIT_1:
case TCPS_FIN_WAIT_2:
case TCPS_CLOSE_WAIT:
so->so_error = ECONNRESET;
close:
tp->t_state = TCPS_CLOSED;
tcpstat.tcps_drops++;
tp = tcp_close(tp);
goto drop;
case TCPS_CLOSING:
case TCPS_LAST_ACK:
case TCPS_TIME_WAIT:
tp = tcp_close(tp);
goto drop;
}
/*
* If a SYN is in the window, then this is an
* error and we send an RST and drop the connection.
*/
if (tiflags & TH_SYN) {
tp = tcp_drop(tp, ECONNRESET);
goto dropwithreset;
}
/*
* If the ACK bit is off we drop the segment and return.
*/
if ((tiflags & TH_ACK) == 0)
goto drop;
/*
* Ack processing.
*/
switch (tp->t_state) {
/*
* In SYN_RECEIVED state if the ack ACKs our SYN then enter
* ESTABLISHED state and continue processing, otherwise
* send an RST.
*/
case TCPS_SYN_RECEIVED:
if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
SEQ_GT(ti->ti_ack, tp->snd_max))
goto dropwithreset;
tcpstat.tcps_connects++;
soisconnected(so);
tcp_established(tp);
/* Do window scaling? */
if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
tp->snd_scale = tp->requested_s_scale;
tp->rcv_scale = tp->request_r_scale;
}
(void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
tp->snd_wl1 = ti->ti_seq - 1;
/* fall into ... */
/*
* In ESTABLISHED state: drop duplicate ACKs; ACK out of range
* ACKs. If the ack is in the range
* tp->snd_una < ti->ti_ack <= tp->snd_max
* then advance tp->snd_una to ti->ti_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:
if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
if (ti->ti_len == 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 (tp->t_timer[TCPT_REXMT] == 0 ||
ti->ti_ack != tp->snd_una)
tp->t_dupacks = 0;
else if (++tp->t_dupacks == tcprexmtthresh) {
tcp_seq onxt = tp->snd_nxt;
u_int win =
min(tp->snd_wnd, tp->snd_cwnd) / 2 /
tp->t_maxseg;
if (win < 2)
win = 2;
tp->snd_ssthresh = win * tp->t_maxseg;
tp->t_timer[TCPT_REXMT] = 0;
tp->t_rtt = 0;
tp->snd_nxt = ti->ti_ack;
tp->snd_cwnd = tp->t_maxseg;
(void) tcp_output(tp);
tp->snd_cwnd = tp->snd_ssthresh +
tp->t_maxseg * tp->t_dupacks;
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
goto drop;
} else if (tp->t_dupacks > tcprexmtthresh) {
tp->snd_cwnd += tp->t_maxseg;
(void) tcp_output(tp);
goto drop;
}
} else
tp->t_dupacks = 0;
break;
}
/*
* If the congestion window was inflated to account
* for the other side's cached packets, retract it.
*/
if (tp->t_dupacks >= tcprexmtthresh &&
tp->snd_cwnd > tp->snd_ssthresh)
tp->snd_cwnd = tp->snd_ssthresh;
tp->t_dupacks = 0;
if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
tcpstat.tcps_rcvacktoomuch++;
goto dropafterack;
}
acked = ti->ti_ack - tp->snd_una;
tcpstat.tcps_rcvackpack++;
tcpstat.tcps_rcvackbyte += acked;
/*
* If we have a timestamp reply, update smoothed
* round trip time. If no timestamp is present but
* transmit timer is running and timed sequence
* number was acked, update smoothed round trip time.
* Since we now have an rtt measurement, cancel the
* timer backoff (cf., Phil Karn's retransmit alg.).
* Recompute the initial retransmit timer.
*/
if (opti.ts_present)
tcp_xmit_timer(tp, tcp_now - opti.ts_ecr + 1);
else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq))
tcp_xmit_timer(tp,tp->t_rtt);
/*
* 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 (ti->ti_ack == tp->snd_max) {
tp->t_timer[TCPT_REXMT] = 0;
needoutput = 1;
} else if (tp->t_timer[TCPT_PERSIST] == 0)
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
/*
* When new data is acked, open the congestion window.
* If the window gives us less than ssthresh packets
* in flight, open exponentially (maxseg per packet).
* Otherwise open linearly: maxseg per window
* (maxseg^2 / cwnd per packet), plus a constant
* fraction of a packet (maxseg/8) to help larger windows
* open quickly enough.
*/
{
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);
}
if (acked > so->so_snd.sb_cc) {
tp->snd_wnd -= so->so_snd.sb_cc;
sbdrop(&so->so_snd, (int)so->so_snd.sb_cc);
ourfinisacked = 1;
} else {
sbdrop(&so->so_snd, acked);
tp->snd_wnd -= acked;
ourfinisacked = 0;
}
if (sb_notify(&so->so_snd))
sowwakeup(so);
tp->snd_una = ti->ti_ack;
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.
*/
if (so->so_state & SS_CANTRCVMORE) {
soisdisconnected(so);
tp->t_timer[TCPT_2MSL] = tcp_maxidle;
}
tp->t_state = TCPS_FIN_WAIT_2;
}
break;
/*
* In CLOSING STATE in addition to the processing for
* the ESTABLISHED state if the ACK acknowledges our FIN
* then enter the TIME-WAIT state, otherwise ignore
* the segment.
*/
case TCPS_CLOSING:
if (ourfinisacked) {
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
soisdisconnected(so);
}
break;
/*
* In LAST_ACK, we may still be waiting for data to drain
* and/or to be acked, as well as for the ack of our FIN.
* If our FIN is now acknowledged, delete the TCB,
* enter the closed state and return.
*/
case TCPS_LAST_ACK:
if (ourfinisacked) {
tp = tcp_close(tp);
goto drop;
}
break;
/*
* In TIME_WAIT state the only thing that should arrive
* is a retransmission of the remote FIN. Acknowledge
* it and restart the finack timer.
*/
case TCPS_TIME_WAIT:
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
goto dropafterack;
}
}
step6:
/*
* Update window information.
* Don't look at window if no ACK: TAC's send garbage on first SYN.
*/
if (((tiflags & TH_ACK) && SEQ_LT(tp->snd_wl1, ti->ti_seq)) ||
(tp->snd_wl1 == ti->ti_seq && SEQ_LT(tp->snd_wl2, ti->ti_ack)) ||
(tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)) {
/* keep track of pure window updates */
if (ti->ti_len == 0 &&
tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd)
tcpstat.tcps_rcvwinupd++;
tp->snd_wnd = tiwin;
tp->snd_wl1 = ti->ti_seq;
tp->snd_wl2 = ti->ti_ack;
if (tp->snd_wnd > tp->max_sndwnd)
tp->max_sndwnd = tp->snd_wnd;
needoutput = 1;
}
/*
* Process segments with URG.
*/
if ((tiflags & TH_URG) && ti->ti_urp &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
/*
* This is a kludge, but if we receive and accept
* random urgent pointers, we'll crash in
* soreceive. It's hard to imagine someone
* actually wanting to send this much urgent data.
*/
if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) {
ti->ti_urp = 0; /* XXX */
tiflags &= ~TH_URG; /* XXX */
goto dodata; /* XXX */
}
/*
* If this segment advances the known urgent pointer,
* then mark the data stream. This should not happen
* in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
* a FIN has been received from the remote side.
* In these states we ignore the URG.
*
* According to RFC961 (Assigned Protocols),
* the urgent pointer points to the last octet
* of urgent data. We continue, however,
* to consider it to indicate the first octet
* of data past the urgent section as the original
* spec states (in one of two places).
*/
if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) {
tp->rcv_up = ti->ti_seq + ti->ti_urp;
so->so_oobmark = so->so_rcv.sb_cc +
(tp->rcv_up - tp->rcv_nxt) - 1;
if (so->so_oobmark == 0)
so->so_state |= SS_RCVATMARK;
sohasoutofband(so);
tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
}
/*
* Remove out of band data so doesn't get presented to user.
* This can happen independent of advancing the URG pointer,
* but if two URG's are pending at once, some out-of-band
* data may creep in... ick.
*/
if (ti->ti_urp <= (u_int16_t) ti->ti_len
#ifdef SO_OOBINLINE
&& (so->so_options & SO_OOBINLINE) == 0
#endif
)
tcp_pulloutofband(so, ti, m);
} else
/*
* If no out of band data is expected,
* pull receive urgent pointer along
* with the receive window.
*/
if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
tp->rcv_up = tp->rcv_nxt;
dodata: /* XXX */
/*
* Process the segment text, merging it into the TCP sequencing queue,
* and arranging for acknowledgment of receipt if necessary.
* This process logically involves adjusting tp->rcv_wnd as data
* is presented to the user (this happens in tcp_usrreq.c,
* case PRU_RCVD). If a FIN has already been received on this
* connection then we just ignore the text.
*/
if ((ti->ti_len || (tiflags & TH_FIN)) &&
TCPS_HAVERCVDFIN(tp->t_state) == 0) {
TCP_REASS(tp, ti, m, so, tiflags);
/*
* 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);
tiflags &= ~TH_FIN;
}
/*
* If FIN is received ACK the FIN and let the user know
* that the connection is closing. Ignore a FIN received before
* the connection is fully established.
*/
if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) {
if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
socantrcvmore(so);
tp->t_flags |= TF_ACKNOW;
tp->rcv_nxt++;
}
switch (tp->t_state) {
/*
* In ESTABLISHED STATE enter the CLOSE_WAIT state.
*/
case TCPS_ESTABLISHED:
tp->t_state = TCPS_CLOSE_WAIT;
break;
/*
* If still in FIN_WAIT_1 STATE FIN has not been acked so
* enter the CLOSING state.
*/
case TCPS_FIN_WAIT_1:
tp->t_state = TCPS_CLOSING;
break;
/*
* In FIN_WAIT_2 state enter the TIME_WAIT state,
* starting the time-wait timer, turning off the other
* standard timers.
*/
case TCPS_FIN_WAIT_2:
tp->t_state = TCPS_TIME_WAIT;
tcp_canceltimers(tp);
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
soisdisconnected(so);
break;
/*
* In TIME_WAIT state restart the 2 MSL time_wait timer.
*/
case TCPS_TIME_WAIT:
tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL;
break;
}
}
if (so->so_options & SO_DEBUG)
tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0);
/*
* Return any desired output.
*/
if (needoutput || (tp->t_flags & TF_ACKNOW))
(void) tcp_output(tp);
return;
dropafterack:
/*
* Generate an ACK dropping incoming segment if it occupies
* sequence space, where the ACK reflects our state.
*/
if (tiflags & TH_RST)
goto drop;
m_freem(m);
tp->t_flags |= TF_ACKNOW;
(void) tcp_output(tp);
return;
dropwithreset:
/*
* Generate a RST, dropping incoming segment.
* Make ACK acceptable to originator of segment.
* Don't bother to respond if destination was broadcast/multicast.
*/
if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) ||
IN_MULTICAST(ti->ti_dst.s_addr))
goto drop;
if (tiflags & TH_ACK)
(void)tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST);
else {
if (tiflags & TH_SYN)
ti->ti_len++;
(void)tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0,
TH_RST|TH_ACK);
}
return;
drop:
/*
* Drop space held by incoming segment and return.
*/
if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
m_freem(m);
return;
#ifndef TUBA_INCLUDE
}
void
tcp_dooptions(tp, cp, cnt, ti, oi)
struct tcpcb *tp;
u_char *cp;
int cnt;
struct tcpiphdr *ti;
struct tcp_opt_info *oi;
{
u_int16_t mss;
int opt, optlen;
for (; cnt > 0; cnt -= optlen, cp += optlen) {
opt = cp[0];
if (opt == TCPOPT_EOL)
break;
if (opt == TCPOPT_NOP)
optlen = 1;
else {
optlen = cp[1];
if (optlen <= 0)
break;
}
switch (opt) {
default:
continue;
case TCPOPT_MAXSEG:
if (optlen != TCPOLEN_MAXSEG)
continue;
if (!(ti->ti_flags & TH_SYN))
continue;
bcopy(cp + 2, &mss, sizeof(mss));
oi->maxseg = ntohs(mss);
break;
case TCPOPT_WINDOW:
if (optlen != TCPOLEN_WINDOW)
continue;
if (!(ti->ti_flags & TH_SYN))
continue;
tp->t_flags |= TF_RCVD_SCALE;
tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT);
break;
case TCPOPT_TIMESTAMP:
if (optlen != TCPOLEN_TIMESTAMP)
continue;
oi->ts_present = 1;
bcopy(cp + 2, &oi->ts_val, sizeof(oi->ts_val));
NTOHL(oi->ts_val);
bcopy(cp + 6, &oi->ts_ecr, sizeof(oi->ts_ecr));
NTOHL(oi->ts_ecr);
/*
* A timestamp received in a SYN makes
* it ok to send timestamp requests and replies.
*/
if (ti->ti_flags & TH_SYN) {
tp->t_flags |= TF_RCVD_TSTMP;
tp->ts_recent = oi->ts_val;
tp->ts_recent_age = tcp_now;
}
break;
}
}
}
/*
* Pull out of band byte out of a segment so
* it doesn't appear in the user's data queue.
* It is still reflected in the segment length for
* sequencing purposes.
*/
void
tcp_pulloutofband(so, ti, m)
struct socket *so;
struct tcpiphdr *ti;
register struct mbuf *m;
{
int cnt = ti->ti_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--;
return;
}
cnt -= m->m_len;
m = m->m_next;
if (m == 0)
break;
}
panic("tcp_pulloutofband");
}
/*
* Collect new round-trip time estimate
* and update averages and current timeout.
*/
void
tcp_xmit_timer(tp, rtt)
register struct tcpcb *tp;
short rtt;
{
register short delta;
tcpstat.tcps_rttupdated++;
--rtt;
if (tp->t_srtt != 0) {
/*
* srtt is stored as fixed point with 3 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 << 2) - (tp->t_srtt >> TCP_RTT_SHIFT);
if ((tp->t_srtt += delta) <= 0)
tp->t_srtt = 1 << 2;
/*
* 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 2 bits after the
* binary point (scaled by 4). The following is
* equivalent to rfc793 smoothing with an alpha of .75
* (rttvar = rttvar*3/4 + |delta| / 4). This replaces
* rfc793's wired-in beta.
*/
if (delta < 0)
delta = -delta;
delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT);
if ((tp->t_rttvar += delta) <= 0)
tp->t_rttvar = 1 << 2;
} 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 + 2);
tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1);
}
tp->t_rtt = 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),
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;
}
/*
* TCP compressed state engine. Currently used to hold compressed
* state for SYN_RECEIVED.
*/
u_long syn_cache_count;
u_int32_t syn_hash1, syn_hash2;
#define SYN_HASH(sa, sp, dp) \
((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \
((u_int32_t)(sp)))^syn_hash2)) \
& 0x7fffffff)
#define eptosp(ep, e, s) ((struct s *)((char *)(ep) - \
((char *)(&((struct s *)0)->e) - (char *)0)))
#define SYN_CACHE_RM(sc, p, scp) { \
*(p) = (sc)->sc_next; \
if ((sc)->sc_next) \
(sc)->sc_next->sc_timer += (sc)->sc_timer; \
else { \
(scp)->sch_timer_sum -= (sc)->sc_timer; \
if ((scp)->sch_timer_sum <= 0) \
(scp)->sch_timer_sum = -1; \
/* If need be, fix up the last pointer */ \
if ((scp)->sch_first) \
(scp)->sch_last = eptosp(p, sc_next, syn_cache); \
} \
(scp)->sch_length--; \
syn_cache_count--; \
}
void
syn_cache_insert(sc, prevp, headp)
struct syn_cache *sc;
struct syn_cache ***prevp;
struct syn_cache_head **headp;
{
struct syn_cache_head *scp, *scp2, *sce;
struct syn_cache *sc2;
static u_int timeo_val;
int s;
/* Initialize the hash secrets when adding the first entry */
if (syn_cache_count == 0) {
struct timeval tv;
microtime(&tv);
syn_hash1 = random() ^ (u_long)&sc;
syn_hash2 = random() ^ tv.tv_usec;
}
sc->sc_hash = SYN_HASH(&sc->sc_src, sc->sc_sport, sc->sc_dport);
sc->sc_next = NULL;
scp = &tcp_syn_cache[sc->sc_hash % tcp_syn_cache_size];
*headp = scp;
/*
* Make sure that we don't overflow the per-bucket
* limit or the total cache size limit.
*/
s = splsoftnet();
if (scp->sch_length >= tcp_syn_bucket_limit) {
tcpstat.tcps_sc_bucketoverflow++;
sc2 = scp->sch_first;
scp->sch_first = sc2->sc_next;
FREE(sc2, M_PCB);
} else if (syn_cache_count >= tcp_syn_cache_limit) {
tcpstat.tcps_sc_overflowed++;
/*
* The cache is full. Toss the first (i.e, oldest)
* element in this bucket.
*/
scp2 = scp;
if (scp2->sch_first == NULL) {
sce = &tcp_syn_cache[tcp_syn_cache_size];
for (++scp2; scp2 != scp; scp2++) {
if (scp2 >= sce)
scp2 = &tcp_syn_cache[0];
if (scp2->sch_first)
break;
}
}
sc2 = scp2->sch_first;
if (sc2 == NULL) {
FREE(sc, M_PCB);
return;
}
if ((scp2->sch_first = sc2->sc_next) == NULL)
scp2->sch_last = NULL;
else
sc2->sc_next->sc_timer += sc2->sc_timer;
FREE(sc2, M_PCB);
} else {
scp->sch_length++;
syn_cache_count++;
}
tcpstat.tcps_sc_added++;
/*
* Put it into the bucket.
*/
if (scp->sch_first == NULL)
*prevp = &scp->sch_first;
else {
*prevp = &scp->sch_last->sc_next;
tcpstat.tcps_sc_collisions++;
}
**prevp = sc;
scp->sch_last = sc;
/*
* If the timeout value has changed
* 1) force it to fit in a u_char
* 2) Run the timer routine to truncate all
* existing entries to the new timeout value.
*/
if (timeo_val != tcp_syn_cache_timeo) {
tcp_syn_cache_timeo = min(tcp_syn_cache_timeo, UCHAR_MAX);
if (timeo_val > tcp_syn_cache_timeo)
syn_cache_timer(timeo_val - tcp_syn_cache_timeo);
timeo_val = tcp_syn_cache_timeo;
}
if (scp->sch_timer_sum > 0)
sc->sc_timer = tcp_syn_cache_timeo - scp->sch_timer_sum;
else if (scp->sch_timer_sum == 0) {
/* When the bucket timer is 0, it is not in the cache queue. */
scp->sch_headq = tcp_syn_cache_first;
tcp_syn_cache_first = scp;
sc->sc_timer = tcp_syn_cache_timeo;
}
scp->sch_timer_sum = tcp_syn_cache_timeo;
splx(s);
}
/*
* Walk down the cache list, decrementing the timer of
* the first element on each entry. If the timer goes
* to zero, remove it and all successive entries with
* a zero timer.
*/
void
syn_cache_timer(interval)
int interval;
{
struct syn_cache_head *scp, **pscp;
struct syn_cache *sc, *scn;
int n, s;
pscp = &tcp_syn_cache_first;
scp = tcp_syn_cache_first;
s = splsoftnet();
while (scp) {
/*
* Remove any empty hash buckets
* from the cache queue.
*/
if ((sc = scp->sch_first) == NULL) {
*pscp = scp->sch_headq;
scp->sch_headq = NULL;
scp->sch_timer_sum = 0;
scp->sch_first = scp->sch_last = NULL;
scp->sch_length = 0;
scp = *pscp;
continue;
}
scp->sch_timer_sum -= interval;
if (scp->sch_timer_sum <= 0)
scp->sch_timer_sum = -1;
n = interval;
while (sc->sc_timer <= n) {
n -= sc->sc_timer;
scn = sc->sc_next;
tcpstat.tcps_sc_timed_out++;
syn_cache_count--;
FREE(sc, M_PCB);
scp->sch_length--;
if ((sc = scn) == NULL)
break;
}
if ((scp->sch_first = sc) != NULL) {
sc->sc_timer -= n;
pscp = &scp->sch_headq;
scp = scp->sch_headq;
}
}
splx(s);
}
/*
* Find an entry in the syn cache.
*/
struct syn_cache *
syn_cache_lookup(ti, prevp, headp)
struct tcpiphdr *ti;
struct syn_cache ***prevp;
struct syn_cache_head **headp;
{
struct syn_cache *sc, **prev;
struct syn_cache_head *head;
u_int32_t hash;
int s;
hash = SYN_HASH(&ti->ti_src, ti->ti_sport, ti->ti_dport);
head = &tcp_syn_cache[hash % tcp_syn_cache_size];
*headp = head;
prev = &head->sch_first;
s = splsoftnet();
for (sc = head->sch_first; sc; prev = &sc->sc_next, sc = sc->sc_next) {
if (sc->sc_hash != hash)
continue;
if (sc->sc_src.s_addr == ti->ti_src.s_addr &&
sc->sc_sport == ti->ti_sport &&
sc->sc_dport == ti->ti_dport &&
sc->sc_dst.s_addr == ti->ti_dst.s_addr) {
*prevp = prev;
splx(s);
return (sc);
}
}
splx(s);
return (NULL);
}
/*
* This function gets called when we receive an ACK for a
* socket in the LISTEN state. We look up the connection
* in the syn cache, and if its there, we pull it out of
* the cache and turn it into a full-blown connection in
* the SYN-RECEIVED state.
*
* The return values may not be immediately obvious, and their effects
* can be subtle, so here they are:
*
* NULL SYN was not found in cache; caller should drop the
* packet and send an RST.
*
* -1 We were unable to create the new connection, and are
* aborting it. An ACK,RST is being sent to the peer
* (unless we got screwey sequence numbners; see below),
* because the 3-way handshake has been completed. Caller
* should not free the mbuf, since we may be using it. If
* we are not, we will free it.
*
* Otherwise, the return value is a pointer to the new socket
* associated with the connection.
*/
struct socket *
syn_cache_get(so, m)
struct socket *so;
struct mbuf *m;
{
struct syn_cache *sc, **sc_prev;
struct syn_cache_head *head;
register struct inpcb *inp;
register struct tcpcb *tp = 0;
register struct tcpiphdr *ti;
struct sockaddr_in *sin;
struct mbuf *am;
long win;
int s;
ti = mtod(m, struct tcpiphdr *);
s = splsoftnet();
if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) {
splx(s);
return (NULL);
}
win = sbspace(&so->so_rcv);
if (win > TCP_MAXWIN)
win = TCP_MAXWIN;
/*
* Verify the sequence and ack numbers.
*/
if ((ti->ti_ack != sc->sc_iss + 1) ||
SEQ_LEQ(ti->ti_seq, sc->sc_irs) ||
SEQ_GT(ti->ti_seq, sc->sc_irs + 1 + win)) {
(void) syn_cache_respond(sc, m, ti, win, 0);
splx(s);
return ((struct socket *)(-1));
}
/* Remove this cache entry */
SYN_CACHE_RM(sc, sc_prev, head);
splx(s);
/*
* Ok, create the full blown connection, and set things up
* as they would have been set up if we had created the
* connection when the SYN arrived. If we can't create
* the connection, abort it.
*/
so = sonewconn(so, SS_ISCONNECTED);
if (so == NULL)
goto resetandabort;
inp = sotoinpcb(so);
inp->inp_laddr = sc->sc_dst;
inp->inp_lport = sc->sc_dport;
in_pcbstate(inp, INP_BOUND);
#if BSD>=43
inp->inp_options = ip_srcroute();
#endif
am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */
if (am == NULL) {
m_freem(m);
goto resetandabort;
}
am->m_len = sizeof(struct sockaddr_in);
sin = mtod(am, struct sockaddr_in *);
sin->sin_family = AF_INET;
sin->sin_len = sizeof(*sin);
sin->sin_addr = sc->sc_src;
sin->sin_port = sc->sc_sport;
bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero));
if (in_pcbconnect(inp, am)) {
(void) m_free(am);
m_freem(m);
goto resetandabort;
}
(void) m_free(am);
tp = intotcpcb(inp);
if (sc->sc_request_r_scale != 15) {
tp->requested_s_scale = sc->sc_requested_s_scale;
tp->request_r_scale = sc->sc_request_r_scale;
tp->snd_scale = sc->sc_requested_s_scale;
tp->rcv_scale = sc->sc_request_r_scale;
tp->t_flags |= TF_RCVD_SCALE;
}
if (sc->sc_tstmp)
tp->t_flags |= TF_RCVD_TSTMP;
tp->t_template = tcp_template(tp);
if (tp->t_template == 0) {
tp = tcp_drop(tp, ENOBUFS); /* destroys socket */
so = NULL;
m_freem(m);
goto abort;
}
tp->iss = sc->sc_iss;
tp->irs = sc->sc_irs;
tcp_sendseqinit(tp);
tcp_rcvseqinit(tp);
tp->t_state = TCPS_SYN_RECEIVED;
tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
tcpstat.tcps_accepts++;
/* Initialize tp->t_ourmss before we deal with the peer's! */
tp->t_ourmss = sc->sc_ourmaxseg;
tcp_mss_from_peer(tp, sc->sc_peermaxseg);
tcp_rmx_rtt(tp);
tp->snd_wl1 = sc->sc_irs;
tp->rcv_up = sc->sc_irs + 1;
/*
* This is what whould have happened in tcp_ouput() when
* the SYN,ACK was sent.
*/
tp->snd_up = tp->snd_una;
tp->snd_max = tp->snd_nxt = tp->iss+1;
tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
tp->rcv_adv = tp->rcv_nxt + win;
tp->last_ack_sent = tp->rcv_nxt;
tcpstat.tcps_sc_completed++;
FREE(sc, M_PCB);
return (so);
resetandabort:
(void) tcp_respond(NULL, ti, m, ti->ti_seq+ti->ti_len,
(tcp_seq)0, TH_RST|TH_ACK);
abort:
if (so != NULL)
(void) soabort(so);
FREE(sc, M_PCB);
tcpstat.tcps_sc_aborted++;
return ((struct socket *)(-1));
}
/*
* This function is called when we get a RST for a
* non-existant connection, so that we can see if the
* connection is in the syn cache. If it is, zap it.
*/
void
syn_cache_reset(ti)
register struct tcpiphdr *ti;
{
struct syn_cache *sc, **sc_prev;
struct syn_cache_head *head;
int s = splsoftnet();
if ((sc = syn_cache_lookup(ti, &sc_prev, &head)) == NULL) {
splx(s);
return;
}
if (SEQ_LT(ti->ti_seq,sc->sc_irs) ||
SEQ_GT(ti->ti_seq, sc->sc_irs+1)) {
splx(s);
return;
}
SYN_CACHE_RM(sc, sc_prev, head);
splx(s);
tcpstat.tcps_sc_reset++;
FREE(sc, M_PCB);
}
void
syn_cache_unreach(ip, th)
struct ip *ip;
struct tcphdr *th;
{
struct syn_cache *sc, **sc_prev;
struct syn_cache_head *head;
struct tcpiphdr ti2;
int s;
ti2.ti_src.s_addr = ip->ip_dst.s_addr;
ti2.ti_dst.s_addr = ip->ip_src.s_addr;
ti2.ti_sport = th->th_dport;
ti2.ti_dport = th->th_sport;
s = splsoftnet();
if ((sc = syn_cache_lookup(&ti2, &sc_prev, &head)) == NULL) {
splx(s);
return;
}
/* If the sequence number != sc_iss, then it's a bogus ICMP msg */
if (ntohl (th->th_seq) != sc->sc_iss) {
splx(s);
return;
}
SYN_CACHE_RM(sc, sc_prev, head);
splx(s);
tcpstat.tcps_sc_unreach++;
FREE(sc, M_PCB);
}
/*
* Given a LISTEN socket and an inbound SYN request, add
* this to the syn cache, and send back a segment:
* <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
* to the source.
*
* XXX We don't properly handle SYN-with-data!
*/
int
syn_cache_add(so, m, optp, optlen, oi)
struct socket *so;
struct mbuf *m;
u_char *optp;
int optlen;
struct tcp_opt_info *oi;
{
register struct tcpiphdr *ti;
struct tcpcb tb, *tp;
long win;
struct syn_cache *sc, **sc_prev;
struct syn_cache_head *scp;
extern int tcp_do_rfc1323;
tp = sototcpcb(so);
ti = mtod(m, struct tcpiphdr *);
/*
* RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN
* in_broadcast() should never return true on a received
* packet with M_BCAST not set.
*/
if (m->m_flags & (M_BCAST|M_MCAST) ||
IN_MULTICAST(ti->ti_src.s_addr) ||
IN_MULTICAST(ti->ti_dst.s_addr))
return (0);
/*
* Initialize some local state.
*/
win = sbspace(&so->so_rcv);
if (win > TCP_MAXWIN)
win = TCP_MAXWIN;
if (optp) {
tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0;
tcp_dooptions(&tb, optp, optlen, ti, oi);
} else
tb.t_flags = 0;
/*
* See if we already have an entry for this connection.
*/
if ((sc = syn_cache_lookup(ti, &sc_prev, &scp)) != NULL) {
tcpstat.tcps_sc_dupesyn++;
if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) {
tcpstat.tcps_sndacks++;
tcpstat.tcps_sndtotal++;
}
return (1);
}
MALLOC(sc, struct syn_cache *, sizeof(*sc), M_PCB, M_NOWAIT);
if (sc == NULL)
return (0);
/*
* Fill in the cache, and put the necessary TCP
* options into the reply.
*/
sc->sc_src.s_addr = ti->ti_src.s_addr;
sc->sc_dst.s_addr = ti->ti_dst.s_addr;
sc->sc_sport = ti->ti_sport;
sc->sc_dport = ti->ti_dport;
sc->sc_irs = ti->ti_seq;
sc->sc_iss = tcp_iss;
tcp_iss += TCP_ISSINCR/2;
sc->sc_peermaxseg = oi->maxseg;
sc->sc_ourmaxseg = tcp_mss_to_advertise(tp);
sc->sc_tstmp = (tcp_do_rfc1323 && (tb.t_flags & TF_RCVD_TSTMP)) ? 1 : 0;
if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
(TF_RCVD_SCALE|TF_REQ_SCALE)) {
sc->sc_requested_s_scale = tb.requested_s_scale;
sc->sc_request_r_scale = 0;
while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT &&
TCP_MAXWIN << sc->sc_request_r_scale <
so->so_rcv.sb_hiwat)
sc->sc_request_r_scale++;
} else {
sc->sc_requested_s_scale = 15;
sc->sc_request_r_scale = 15;
}
if (syn_cache_respond(sc, m, ti, win, tb.ts_recent) == 0) {
syn_cache_insert(sc, &sc_prev, &scp);
tcpstat.tcps_sndacks++;
tcpstat.tcps_sndtotal++;
} else {
FREE(sc, M_PCB);
tcpstat.tcps_sc_dropped++;
}
return (1);
}
int
syn_cache_respond(sc, m, ti, win, ts)
struct syn_cache *sc;
struct mbuf *m;
register struct tcpiphdr *ti;
long win;
u_long ts;
{
u_int8_t *optp;
int optlen;
/*
* Tack on the TCP options. If there isn't enough trailing
* space for them, move up the fixed header to make space.
*/
optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) +
(sc->sc_tstmp ? TCPOLEN_TSTAMP_APPA : 0);
if (optlen > M_TRAILINGSPACE(m)) {
if (M_LEADINGSPACE(m) >= optlen) {
m->m_data -= optlen;
m->m_len += optlen;
} else {
struct mbuf *m0 = m;
if ((m = m_gethdr(M_DONTWAIT, MT_HEADER)) == NULL) {
m_freem(m0);
return (ENOBUFS);
}
MH_ALIGN(m, sizeof(*ti) + optlen);
m->m_next = m0; /* this gets freed below */
}
ovbcopy((caddr_t)ti, mtod(m, caddr_t), sizeof(*ti));
ti = mtod(m, struct tcpiphdr *);
}
optp = (u_int8_t *)(ti + 1);
optp[0] = TCPOPT_MAXSEG;
optp[1] = 4;
optp[2] = (sc->sc_ourmaxseg >> 8) & 0xff;
optp[3] = sc->sc_ourmaxseg & 0xff;
optlen = 4;
if (sc->sc_request_r_scale != 15) {
*((u_int32_t *)(optp + optlen)) = htonl(TCPOPT_NOP << 24 |
TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 |
sc->sc_request_r_scale);
optlen += 4;
}
if (sc->sc_tstmp) {
u_int32_t *lp = (u_int32_t *)(optp + optlen);
/* Form timestamp option as shown in appendix A of RFC 1323. */
*lp++ = htonl(TCPOPT_TSTAMP_HDR);
*lp++ = htonl(tcp_now);
*lp = htonl(ts);
optlen += TCPOLEN_TSTAMP_APPA;
}
/*
* Toss any trailing mbufs. No need to worry about
* m_len and m_pkthdr.len, since tcp_respond() will
* unconditionally set them.
*/
if (m->m_next) {
m_freem(m->m_next);
m->m_next = NULL;
}
/*
* Fill in the fields that tcp_respond() will not touch, and
* then send the response.
*/
ti->ti_off = (sizeof(struct tcphdr) + optlen) >> 2;
ti->ti_win = htons(win);
return (tcp_respond(NULL, ti, m, sc->sc_irs + 1, sc->sc_iss,
TH_SYN|TH_ACK));
}
#endif /* TUBA_INCLUDE */
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