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09423f72fd
freebsd-skq/sys/netinet/tcp_reass.c
Michael Tuexen 09423f72fd Fix a regression in the TCP handling of received segments. 
When receiving TCP segments the stack protects itself by limiting
the resources allocated for a TCP connections. This patch adds
an exception to these limitations for the TCP segement which is the next
expected in-sequence segment. Without this patch, TCP connections
may stall and finally fail in some cases of packet loss.

Reported by:		jhb@
Reviewed by:		jtl@, rrs@
MFC after:		3 days
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D18580
2018-12-20 16:05:30 +00:00

1095 lines
30 KiB
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/*-
* SPDX-License-Identifier: BSD-3-Clause
*
* 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.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include "opt_inet.h"
#include "opt_inet6.h"
#include "opt_tcpdebug.h"
#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/eventhandler.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/socket.h>
#include <sys/socketvar.h>
#include <sys/sysctl.h>
#include <sys/syslog.h>
#include <sys/systm.h>
#include <vm/uma.h>
#include <net/if.h>
#include <net/if_var.h>
#include <net/route.h>
#include <net/vnet.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_var.h>
#include <netinet/ip_options.h>
#include <netinet/ip6.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 <netinet/tcp_log_buf.h>
#include <netinet/tcp_hpts.h>
#include <netinet6/tcp6_var.h>
#include <netinet/tcpip.h>
#ifdef TCPDEBUG
#include <netinet/tcp_debug.h>
#endif /* TCPDEBUG */
#define TCP_R_LOG_ADD 1
#define TCP_R_LOG_LIMIT_REACHED 2
#define TCP_R_LOG_APPEND 3
#define TCP_R_LOG_PREPEND 4
#define TCP_R_LOG_REPLACE 5
#define TCP_R_LOG_MERGE_INTO 6
#define TCP_R_LOG_NEW_ENTRY 7
#define TCP_R_LOG_READ 8
#define TCP_R_LOG_ZERO 9
#define TCP_R_LOG_DUMP 10
#define TCP_R_LOG_TRIM 11
/* For debugging we want counters and BB logging */
/* #define TCP_REASS_COUNTERS 1 */
/* #define TCP_REASS_LOGGING 1 */
static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0,
"TCP Segment Reassembly Queue");
static SYSCTL_NODE(_net_inet_tcp_reass, OID_AUTO, stats, CTLFLAG_RW, 0,
"TCP Segment Reassembly stats");
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");
static uma_zone_t tcp_reass_zone;
SYSCTL_UMA_CUR(_net_inet_tcp_reass, OID_AUTO, cursegments, 0,
&tcp_reass_zone,
"Global number of TCP Segments currently in Reassembly Queue");
static u_int tcp_reass_maxqueuelen = 100;
SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, maxqueuelen, CTLFLAG_RWTUN,
&tcp_reass_maxqueuelen, 0,
"Maximum number of TCP Segments per Reassembly Queue");
static int tcp_new_limits = 0;
SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, new_limit, CTLFLAG_RWTUN,
&tcp_new_limits, 0,
"Do we use the new limit method we are discussing?");
static u_int tcp_reass_queue_guard = 16;
SYSCTL_UINT(_net_inet_tcp_reass, OID_AUTO, queueguard, CTLFLAG_RWTUN,
&tcp_reass_queue_guard, 16,
"Number of TCP Segments in Reassembly Queue where we flip over to guard mode");
#ifdef TCP_REASS_COUNTERS
counter_u64_t reass_entry;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, entry, CTLFLAG_RD,
&reass_entry, "A segment entered reassembly ");
counter_u64_t reass_path1;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path1, CTLFLAG_RD,
&reass_path1, "Took path 1");
counter_u64_t reass_path2;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path2, CTLFLAG_RD,
&reass_path2, "Took path 2");
counter_u64_t reass_path3;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path3, CTLFLAG_RD,
&reass_path3, "Took path 3");
counter_u64_t reass_path4;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path4, CTLFLAG_RD,
&reass_path4, "Took path 4");
counter_u64_t reass_path5;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path5, CTLFLAG_RD,
&reass_path5, "Took path 5");
counter_u64_t reass_path6;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path6, CTLFLAG_RD,
&reass_path6, "Took path 6");
counter_u64_t reass_path7;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, path7, CTLFLAG_RD,
&reass_path7, "Took path 7");
counter_u64_t reass_fullwalk;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, fullwalk, CTLFLAG_RD,
&reass_fullwalk, "Took a full walk ");
counter_u64_t reass_nospace;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, nospace, CTLFLAG_RD,
&reass_nospace, "Had no mbuf capacity ");
counter_u64_t merge_fwd;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_fwd, CTLFLAG_RD,
&merge_fwd, "Ran merge fwd");
counter_u64_t merge_into;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, merge_into, CTLFLAG_RD,
&merge_into, "Ran merge into");
counter_u64_t tcp_zero_input;
SYSCTL_COUNTER_U64(_net_inet_tcp_reass_stats, OID_AUTO, zero_input, CTLFLAG_RD,
&tcp_zero_input, "The reassembly buffer saw a zero len segment etc");
#endif
/* Initialize TCP reassembly queue */
static void
tcp_reass_zone_change(void *tag)
{
/* Set the zone limit and read back the effective value. */
tcp_reass_maxseg = nmbclusters / 16;
tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
tcp_reass_maxseg);
}
#ifdef TCP_REASS_LOGGING
static void
tcp_log_reassm(struct tcpcb *tp, struct tseg_qent *q, struct tseg_qent *p,
tcp_seq seq, int len, uint8_t action, int instance)
{
uint32_t cts;
struct timeval tv;
if (tp->t_logstate != TCP_LOG_STATE_OFF) {
union tcp_log_stackspecific log;
memset(&log, 0, sizeof(log));
cts = tcp_get_usecs(&tv);
log.u_bbr.flex1 = seq;
log.u_bbr.cur_del_rate = (uint64_t)q;
log.u_bbr.delRate = (uint64_t)p;
if (q != NULL) {
log.u_bbr.flex2 = q->tqe_start;
log.u_bbr.flex3 = q->tqe_len;
log.u_bbr.flex4 = q->tqe_mbuf_cnt;
log.u_bbr.hptsi_gain = q->tqe_flags;
}
if (p != NULL) {
log.u_bbr.flex5 = p->tqe_start;
log.u_bbr.pkts_out = p->tqe_len;
log.u_bbr.epoch = p->tqe_mbuf_cnt;
log.u_bbr.cwnd_gain = p->tqe_flags;
}
log.u_bbr.flex6 = tp->t_segqmbuflen;
log.u_bbr.flex7 = instance;
log.u_bbr.flex8 = action;
log.u_bbr.timeStamp = cts;
TCP_LOG_EVENTP(tp, NULL,
&tp->t_inpcb->inp_socket->so_rcv,
&tp->t_inpcb->inp_socket->so_snd,
TCP_LOG_REASS, 0,
len, &log, false, &tv);
}
}
static void
tcp_reass_log_dump(struct tcpcb *tp)
{
struct tseg_qent *q;
if (tp->t_logstate != TCP_LOG_STATE_OFF) {
TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
tcp_log_reassm(tp, q, NULL, q->tqe_start, q->tqe_len, TCP_R_LOG_DUMP, 0);
}
};
}
static void
tcp_reass_log_new_in(struct tcpcb *tp, tcp_seq seq, int len, struct mbuf *m,
int logval, struct tseg_qent *q)
{
int cnt;
struct mbuf *t;
cnt = 0;
t = m;
while (t) {
cnt += t->m_len;
t = t->m_next;
}
tcp_log_reassm(tp, q, NULL, seq, len, logval, cnt);
}
#endif
void
tcp_reass_global_init(void)
{
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, 0);
/* Set the zone limit and read back the effective value. */
tcp_reass_maxseg = uma_zone_set_max(tcp_reass_zone,
tcp_reass_maxseg);
#ifdef TCP_REASS_COUNTERS
reass_path1 = counter_u64_alloc(M_WAITOK);
reass_path2 = counter_u64_alloc(M_WAITOK);
reass_path3 = counter_u64_alloc(M_WAITOK);
reass_path4 = counter_u64_alloc(M_WAITOK);
reass_path5 = counter_u64_alloc(M_WAITOK);
reass_path6 = counter_u64_alloc(M_WAITOK);
reass_path7 = counter_u64_alloc(M_WAITOK);
reass_fullwalk = counter_u64_alloc(M_WAITOK);
reass_nospace = counter_u64_alloc(M_WAITOK);
reass_entry = counter_u64_alloc(M_WAITOK);
merge_fwd = counter_u64_alloc(M_WAITOK);
merge_into = counter_u64_alloc(M_WAITOK);
tcp_zero_input = counter_u64_alloc(M_WAITOK);
#endif
EVENTHANDLER_REGISTER(nmbclusters_change,
tcp_reass_zone_change, NULL, EVENTHANDLER_PRI_ANY);
}
void
tcp_reass_flush(struct tcpcb *tp)
{
struct tseg_qent *qe;
INP_WLOCK_ASSERT(tp->t_inpcb);
while ((qe = TAILQ_FIRST(&tp->t_segq)) != NULL) {
TAILQ_REMOVE(&tp->t_segq, qe, tqe_q);
m_freem(qe->tqe_m);
uma_zfree(tcp_reass_zone, qe);
tp->t_segqlen--;
}
tp->t_segqmbuflen = 0;
KASSERT((tp->t_segqlen == 0),
("TCP reass queue %p segment count is %d instead of 0 after flush.",
tp, tp->t_segqlen));
}
static void
tcp_reass_append(struct tcpcb *tp, struct tseg_qent *last,
struct mbuf *m, struct tcphdr *th, int tlen,
struct mbuf *mlast, int lenofoh)
{
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, last, NULL, th->th_seq, tlen, TCP_R_LOG_APPEND, 0);
#endif
last->tqe_len += tlen;
last->tqe_m->m_pkthdr.len += tlen;
/* Preserve the FIN bit if its there */
last->tqe_flags |= (th->th_flags & TH_FIN);
last->tqe_last->m_next = m;
last->tqe_last = mlast;
last->tqe_mbuf_cnt += lenofoh;
tp->t_rcvoopack++;
TCPSTAT_INC(tcps_rcvoopack);
TCPSTAT_ADD(tcps_rcvoobyte, tlen);
#ifdef TCP_REASS_LOGGING
tcp_reass_log_new_in(tp, last->tqe_start, lenofoh, last->tqe_m,
TCP_R_LOG_APPEND,
last);
#endif
}
static void
tcp_reass_prepend(struct tcpcb *tp, struct tseg_qent *first, struct mbuf *m, struct tcphdr *th,
int tlen, struct mbuf *mlast, int lenofoh)
{
int i;
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, first, NULL, th->th_seq, tlen, TCP_R_LOG_PREPEND, 0);
#endif
if (SEQ_GT((th->th_seq + tlen), first->tqe_start)) {
/* The new data overlaps into the old */
i = (th->th_seq + tlen) - first->tqe_start;
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 1);
#endif
m_adj(first->tqe_m, i);
first->tqe_len -= i;
first->tqe_start += i;
}
/* Ok now setup our chain to point to the old first */
mlast->m_next = first->tqe_m;
first->tqe_m = m;
first->tqe_len += tlen;
first->tqe_start = th->th_seq;
first->tqe_m->m_pkthdr.len = first->tqe_len;
first->tqe_mbuf_cnt += lenofoh;
tp->t_rcvoopack++;
TCPSTAT_INC(tcps_rcvoopack);
TCPSTAT_ADD(tcps_rcvoobyte, tlen);
#ifdef TCP_REASS_LOGGING
tcp_reass_log_new_in(tp, first->tqe_start, lenofoh, first->tqe_m,
TCP_R_LOG_PREPEND,
first);
#endif
}
static void
tcp_reass_replace(struct tcpcb *tp, struct tseg_qent *q, struct mbuf *m,
tcp_seq seq, int len, struct mbuf *mlast, int mbufoh, uint8_t flags)
{
/*
* Free the data in q, and replace
* it with the new segment.
*/
int len_dif;
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, q, NULL, seq, len, TCP_R_LOG_REPLACE, 0);
#endif
m_freem(q->tqe_m);
KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
("Tp:%p seg queue goes negative", tp));
tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
q->tqe_mbuf_cnt = mbufoh;
q->tqe_m = m;
q->tqe_last = mlast;
q->tqe_start = seq;
if (len > q->tqe_len)
len_dif = len - q->tqe_len;
else
len_dif = 0;
tp->t_rcvoopack++;
TCPSTAT_INC(tcps_rcvoopack);
TCPSTAT_ADD(tcps_rcvoobyte, len_dif);
q->tqe_len = len;
q->tqe_flags = (flags & TH_FIN);
q->tqe_m->m_pkthdr.len = q->tqe_len;
tp->t_segqmbuflen += mbufoh;
}
static void
tcp_reass_merge_into(struct tcpcb *tp, struct tseg_qent *ent,
struct tseg_qent *q)
{
/*
* Merge q into ent and free q from the list.
*/
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, q, ent, 0, 0, TCP_R_LOG_MERGE_INTO, 0);
#endif
#ifdef TCP_REASS_COUNTERS
counter_u64_add(merge_into, 1);
#endif
ent->tqe_last->m_next = q->tqe_m;
ent->tqe_last = q->tqe_last;
ent->tqe_len += q->tqe_len;
ent->tqe_mbuf_cnt += q->tqe_mbuf_cnt;
ent->tqe_m->m_pkthdr.len += q->tqe_len;
ent->tqe_flags |= (q->tqe_flags & TH_FIN);
TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
uma_zfree(tcp_reass_zone, q);
tp->t_segqlen--;
}
static void
tcp_reass_merge_forward(struct tcpcb *tp, struct tseg_qent *ent)
{
struct tseg_qent *q, *qtmp;
int i;
tcp_seq max;
/*
* Given an entry merge forward anyplace
* that ent overlaps forward.
*/
max = ent->tqe_start + ent->tqe_len;
q = TAILQ_NEXT(ent, tqe_q);
if (q == NULL) {
/* Nothing left */
return;
}
TAILQ_FOREACH_FROM_SAFE(q, &tp->t_segq, tqe_q, qtmp) {
if (SEQ_GT(q->tqe_start, max)) {
/* Beyond q */
break;
}
/* We have some or all that are overlapping */
if (SEQ_GEQ(max, (q->tqe_start + q->tqe_len))) {
/* It consumes it all */
tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
m_freem(q->tqe_m);
TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
uma_zfree(tcp_reass_zone, q);
tp->t_segqlen--;
continue;
}
/*
* Trim the q entry to dovetail to this one
* and then merge q into ent updating max
* in the process.
*/
i = max - q->tqe_start;
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, q, NULL, 0, i, TCP_R_LOG_TRIM, 2);
#endif
m_adj(q->tqe_m, i);
q->tqe_len -= i;
q->tqe_start += i;
tcp_reass_merge_into(tp, ent, q);
max = ent->tqe_start + ent->tqe_len;
}
#ifdef TCP_REASS_COUNTERS
counter_u64_add(merge_fwd, 1);
#endif
}
static int
tcp_reass_overhead_of_chain(struct mbuf *m, struct mbuf **mlast)
{
int len = MSIZE;
if (m->m_flags & M_EXT)
len += m->m_ext.ext_size;
while (m->m_next != NULL) {
m = m->m_next;
len += MSIZE;
if (m->m_flags & M_EXT)
len += m->m_ext.ext_size;
}
*mlast = m;
return (len);
}
/*
* NOTE!!! the new tcp-reassembly code *must not* use
* m_adj() with a negative index. That alters the chain
* of mbufs (by possibly chopping trailing mbufs). At
* the front of tcp_reass we count the mbuf overhead
* and setup the tail pointer. If we use m_adj(m, -5)
* we could corrupt the tail pointer. Currently the
* code only uses m_adj(m, postive-num). If this
* changes appropriate changes to update mlast would
* be needed.
*/
int
tcp_reass(struct tcpcb *tp, struct tcphdr *th, tcp_seq *seq_start,
int *tlenp, struct mbuf *m)
{
struct tseg_qent *q, *last, *first;
struct tseg_qent *p = NULL;
struct tseg_qent *nq = NULL;
struct tseg_qent *te = NULL;
struct mbuf *mlast = NULL;
struct sockbuf *sb;
struct socket *so = tp->t_inpcb->inp_socket;
char *s = NULL;
int flags, i, lenofoh;
INP_WLOCK_ASSERT(tp->t_inpcb);
/*
* XXX: tcp_reass() is rather inefficient with its data structures
* and should be rewritten (see NetBSD for optimizations).
*/
/*
* Call with th==NULL after become established to
* force pre-ESTABLISHED data up to user socket.
*/
if (th == NULL)
goto present;
KASSERT(SEQ_GEQ(th->th_seq, tp->rcv_nxt),
("Attempt to add old entry to reassembly queue (th=%p, tp=%p)",
th, tp));
#ifdef TCP_REASS_LOGGING
tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_ADD, NULL);
#endif
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_entry, 1);
#endif
/*
* Check for zero length data.
*/
if ((*tlenp == 0) && ((th->th_flags & TH_FIN) == 0)) {
/*
* A zero length segment does no
* one any good. We could check
* the rcv_nxt <-> rcv_wnd but thats
* already done for us by the caller.
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(tcp_zero_input, 1);
#endif
m_freem(m);
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
return (0);
}
/*
* Will it fit?
*/
lenofoh = tcp_reass_overhead_of_chain(m, &mlast);
sb = &tp->t_inpcb->inp_socket->so_rcv;
if ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
(sb->sb_mbcnt + tp->t_segqmbuflen + lenofoh) > sb->sb_mbmax) {
/* No room */
TCPSTAT_INC(tcps_rcvreassfull);
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_nospace, 1);
#endif
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, NULL, NULL, th->th_seq, lenofoh, TCP_R_LOG_LIMIT_REACHED, 0);
#endif
if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: mbuf count limit reached, "
"segment dropped\n", s, __func__);
free(s, M_TCPLOG);
}
m_freem(m);
*tlenp = 0;
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
return (0);
}
/*
* First lets deal with two common cases, the
* segment appends to the back of our collected
* segments. Or the segment is the next in line.
*/
last = TAILQ_LAST_FAST(&tp->t_segq, tseg_qent, tqe_q);
if (last != NULL) {
if ((th->th_flags & TH_FIN) &&
SEQ_LT((th->th_seq + *tlenp), (last->tqe_start + last->tqe_len))) {
/*
* Someone is trying to game us, dump
* the segment.
*/
*tlenp = 0;
m_freem(m);
return (0);
}
if ((SEQ_GEQ(th->th_seq, last->tqe_start)) &&
(SEQ_GEQ((last->tqe_start + last->tqe_len), th->th_seq))) {
/* Common case, trailing segment is added */
/**
* +--last
* v
* reassembly buffer |---| |---| |---|
* new segment |---|
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path1, 1);
#endif
if (SEQ_GT((last->tqe_start + last->tqe_len), th->th_seq)) {
i = (last->tqe_start + last->tqe_len) - th->th_seq;
if (i < *tlenp) {
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, last, NULL, 0, i, TCP_R_LOG_TRIM, 3);
th->th_seq += i;
#endif
m_adj(m, i);
*tlenp -= i;
} else {
/* Complete overlap */
TCPSTAT_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
m_freem(m);
*tlenp = last->tqe_len;
*seq_start = last->tqe_start;
return (0);
}
}
if (last->tqe_flags & TH_FIN) {
/*
* We have data after the FIN on the last?
*/
*tlenp = 0;
m_freem(m);
return(0);
}
tcp_reass_append(tp, last, m, th, *tlenp, mlast, lenofoh);
tp->t_segqmbuflen += lenofoh;
*seq_start = last->tqe_start;
*tlenp = last->tqe_len;
return (0);
} else if (SEQ_GT(th->th_seq, (last->tqe_start + last->tqe_len))) {
/*
* Second common case, we missed
* another one and have something more
* for the end.
*/
/**
* +--last
* v
* reassembly buffer |---| |---| |---|
* new segment |---|
*/
if (last->tqe_flags & TH_FIN) {
/*
* We have data after the FIN on the last?
*/
*tlenp = 0;
m_freem(m);
return(0);
}
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path2, 1);
#endif
p = last;
goto new_entry;
}
} else {
/* First segment (it's NULL). */
goto new_entry;
}
first = TAILQ_FIRST(&tp->t_segq);
if (SEQ_LT(th->th_seq, first->tqe_start) &&
SEQ_GEQ((th->th_seq + *tlenp),first->tqe_start) &&
SEQ_LT((th->th_seq + *tlenp), (first->tqe_start + first->tqe_len))) {
/*
* The head of the queue is prepended by this and
* it may be the one I want most.
*/
/**
* first-------+
* v
* rea: |---| |---| |---|
* new: |---|
* Note the case we do not deal with here is:
* rea= |---| |---| |---|
* new= |----|
* Due to the fact that it could be
* new |--------------------|
* And we might need to merge forward.
*/
#ifdef INVARIANTS
struct mbuf *firstmbuf;
#endif
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path3, 1);
#endif
if (SEQ_LT(th->th_seq, tp->rcv_nxt)) {
/*
* The resend was even before
* what we have. We need to trim it.
* Note TSNH (it should be trimmed
* before the call to tcp_reass()).
*/
#ifdef INVARIANTS
panic("th->th_seq:%u rcv_nxt:%u tp:%p not pre-trimmed",
th->th_seq, tp->rcv_nxt, tp);
#else
i = tp->rcv_nxt - th->th_seq;
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, first, NULL, 0, i, TCP_R_LOG_TRIM, 4);
#endif
m_adj(m, i);
th->th_seq += i;
*tlenp -= i;
#endif
}
#ifdef INVARIANTS
firstmbuf = first->tqe_m;
#endif
tcp_reass_prepend(tp, first, m, th, *tlenp, mlast, lenofoh);
#ifdef INVARIANTS
if (firstmbuf == first->tqe_m) {
panic("First stayed same m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
m, firstmbuf, first->tqe_m, tp, first);
} else if (first->tqe_m != m) {
panic("First did not change to m:%p foobar:%p first->tqe_m:%p tp:%p first:%p",
m, firstmbuf, first->tqe_m, tp, first);
}
#endif
tp->t_segqmbuflen += lenofoh;
*seq_start = first->tqe_start;
*tlenp = first->tqe_len;
goto present;
} else if (SEQ_LT((th->th_seq + *tlenp), first->tqe_start)) {
/* New segment is before our earliest segment. */
/**
* first---->+
* v
* rea= |---| ....
* new" |---|
*
*/
goto new_entry;
}
/*
* Find a segment which begins after this one does.
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_fullwalk, 1);
#endif
TAILQ_FOREACH(q, &tp->t_segq, tqe_q) {
if (SEQ_GT(q->tqe_start, th->th_seq))
break;
}
p = TAILQ_PREV(q, tsegqe_head, tqe_q);
/**
* Now is this fit just in-between only?
* i.e.:
* p---+ +----q
* v v
* res= |--| |--| |--|
* nee |-|
*/
if (SEQ_LT((th->th_seq + *tlenp), q->tqe_start) &&
((p == NULL) || (SEQ_GT(th->th_seq, (p->tqe_start + p->tqe_len))))) {
/* Yep no overlap */
goto new_entry;
}
/**
* If we reach here we have some (possibly all) overlap
* such as:
* res= |--| |--| |--|
* new= |----|
* or new= |-----------------|
* or new= |--------|
* or new= |---|
* or new= |-----------|
*/
if ((p != NULL) &&
(SEQ_LEQ(th->th_seq, (p->tqe_start + p->tqe_len)))) {
/* conversion to int (in i) handles seq wraparound */
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path4, 1);
#endif
i = p->tqe_start + p->tqe_len - th->th_seq;
if (i >= 0) {
if (i >= *tlenp) {
/**
* prev seg---->+
* v
* reassembly buffer |---|
* new segment |-|
*/
TCPSTAT_INC(tcps_rcvduppack);
TCPSTAT_ADD(tcps_rcvdupbyte, *tlenp);
*tlenp = p->tqe_len;
*seq_start = p->tqe_start;
m_freem(m);
/*
* Try to present any queued data
* at the left window edge to the user.
* This is needed after the 3-WHS
* completes. Note this probably
* will not work and we will return.
*/
return (0);
}
if (i > 0) {
/**
* prev seg---->+
* v
* reassembly buffer |---|
* new segment |-----|
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path5, 1);
#endif
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, p, NULL, 0, i, TCP_R_LOG_TRIM, 5);
#endif
m_adj(m, i);
*tlenp -= i;
th->th_seq += i;
}
}
if (th->th_seq == (p->tqe_start + p->tqe_len)) {
/*
* If dovetails in with this one
* append it.
*/
/**
* prev seg---->+
* v
* reassembly buffer |--| |---|
* new segment |--|
* (note: it was trimmed above if it overlapped)
*/
tcp_reass_append(tp, p, m, th, *tlenp, mlast, lenofoh);
tp->t_segqmbuflen += lenofoh;
} else {
#ifdef INVARIANTS
panic("Impossible cut th_seq:%u p->seq:%u(%d) p:%p tp:%p",
th->th_seq, p->tqe_start, p->tqe_len,
p, tp);
#endif
*tlenp = 0;
m_freem(m);
return (0);
}
q = p;
} else {
/*
* The new data runs over the
* top of previously sack'd data (in q).
* It may be partially overlapping, or
* it may overlap the entire segment.
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path6, 1);
#endif
if (SEQ_GEQ((th->th_seq + *tlenp), (q->tqe_start + q->tqe_len))) {
/* It consumes it all */
/**
* next seg---->+
* v
* reassembly buffer |--| |---|
* new segment |----------|
*/
#ifdef TCP_REASS_COUNTERS
counter_u64_add(reass_path7, 1);
#endif
tcp_reass_replace(tp, q, m, th->th_seq, *tlenp, mlast, lenofoh, th->th_flags);
} else {
/*
* We just need to prepend the data
* to this. It does not overrun
* the end.
*/
/**
* next seg---->+
* v
* reassembly buffer |--| |---|
* new segment |----------|
*/
tcp_reass_prepend(tp, q, m, th, *tlenp, mlast, lenofoh);
tp->t_segqmbuflen += lenofoh;
}
}
/* Now does it go further than that? */
tcp_reass_merge_forward(tp, q);
*seq_start = q->tqe_start;
*tlenp = q->tqe_len;
goto present;
/*
* When we reach here we can't combine it
* with any existing segment.
*
* Limit the number of segments that can be queued to reduce the
* potential for mbuf exhaustion. For best performance, we want to be
* able to queue a full window's worth of segments. The size of the
* socket receive buffer determines our advertised window and grows
* automatically when socket buffer autotuning is enabled. Use it as the
* basis for our queue limit.
*
* However, allow the user to specify a ceiling for the number of
* segments in each queue.
*
* Always let the missing segment through which caused this queue.
* NB: Access to the socket buffer is left intentionally unlocked as we
* can tolerate stale information here.
*
* XXXLAS: Using sbspace(so->so_rcv) instead of so->so_rcv.sb_hiwat
* should work but causes packets to be dropped when they shouldn't.
* Investigate why and re-evaluate the below limit after the behaviour
* is understood.
*/
new_entry:
if (th->th_seq == tp->rcv_nxt && TCPS_HAVEESTABLISHED(tp->t_state)) {
tp->rcv_nxt += *tlenp;
flags = th->th_flags & TH_FIN;
TCPSTAT_INC(tcps_rcvoopack);
TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
SOCKBUF_LOCK(&so->so_rcv);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
m_freem(m);
} else {
sbappendstream_locked(&so->so_rcv, m, 0);
}
sorwakeup_locked(so);
return (flags);
}
if (tcp_new_limits) {
if ((tp->t_segqlen > tcp_reass_queue_guard) &&
(*tlenp < MSIZE)) {
/*
* This is really a lie, we are not full but
* are getting a segment that is above
* guard threshold. If it is and its below
* a mbuf size (256) we drop it if it
* can't fill in some place.
*/
TCPSTAT_INC(tcps_rcvreassfull);
*tlenp = 0;
if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: queue limit reached, "
"segment dropped\n", s, __func__);
free(s, M_TCPLOG);
}
m_freem(m);
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
return (0);
}
} else {
if (tp->t_segqlen >= min((so->so_rcv.sb_hiwat / tp->t_maxseg) + 1,
tcp_reass_maxqueuelen)) {
TCPSTAT_INC(tcps_rcvreassfull);
*tlenp = 0;
if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) {
log(LOG_DEBUG, "%s; %s: queue limit reached, "
"segment dropped\n", s, __func__);
free(s, M_TCPLOG);
}
m_freem(m);
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
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_INC(tcps_rcvmemdrop);
m_freem(m);
*tlenp = 0;
if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL,
NULL))) {
log(LOG_DEBUG, "%s; %s: global zone limit "
"reached, segment dropped\n", s, __func__);
free(s, M_TCPLOG);
}
return (0);
}
tp->t_segqlen++;
tp->t_rcvoopack++;
TCPSTAT_INC(tcps_rcvoopack);
TCPSTAT_ADD(tcps_rcvoobyte, *tlenp);
/* Insert the new segment queue entry into place. */
te->tqe_m = m;
te->tqe_flags = th->th_flags;
te->tqe_len = *tlenp;
te->tqe_start = th->th_seq;
te->tqe_last = mlast;
te->tqe_mbuf_cnt = lenofoh;
tp->t_segqmbuflen += te->tqe_mbuf_cnt;
if (p == NULL) {
TAILQ_INSERT_HEAD(&tp->t_segq, te, tqe_q);
} else {
TAILQ_INSERT_AFTER(&tp->t_segq, p, te, tqe_q);
}
#ifdef TCP_REASS_LOGGING
tcp_reass_log_new_in(tp, th->th_seq, *tlenp, m, TCP_R_LOG_NEW_ENTRY, te);
#endif
present:
/*
* Present data to user, advancing rcv_nxt through
* completed sequence space.
*/
if (!TCPS_HAVEESTABLISHED(tp->t_state))
return (0);
q = TAILQ_FIRST(&tp->t_segq);
KASSERT(q == NULL || SEQ_GEQ(q->tqe_start, tp->rcv_nxt),
("Reassembly queue for %p has stale entry at head", tp));
if (!q || q->tqe_start != tp->rcv_nxt) {
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
return (0);
}
SOCKBUF_LOCK(&so->so_rcv);
do {
tp->rcv_nxt += q->tqe_len;
flags = q->tqe_flags & TH_FIN;
nq = TAILQ_NEXT(q, tqe_q);
TAILQ_REMOVE(&tp->t_segq, q, tqe_q);
if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
m_freem(q->tqe_m);
} else {
#ifdef TCP_REASS_LOGGING
tcp_reass_log_new_in(tp, q->tqe_start, q->tqe_len, q->tqe_m, TCP_R_LOG_READ, q);
tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 1);
#endif
sbappendstream_locked(&so->so_rcv, q->tqe_m, 0);
}
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, q, NULL, th->th_seq, *tlenp, TCP_R_LOG_READ, 2);
#endif
KASSERT(tp->t_segqmbuflen >= q->tqe_mbuf_cnt,
("tp:%p seg queue goes negative", tp));
tp->t_segqmbuflen -= q->tqe_mbuf_cnt;
uma_zfree(tcp_reass_zone, q);
tp->t_segqlen--;
q = nq;
} while (q && q->tqe_start == tp->rcv_nxt);
if (TAILQ_EMPTY(&tp->t_segq) &&
(tp->t_segqmbuflen != 0)) {
#ifdef INVARIANTS
panic("tp:%p segq:%p len:%d queue empty",
tp, &tp->t_segq, tp->t_segqmbuflen);
#else
#ifdef TCP_REASS_LOGGING
tcp_log_reassm(tp, NULL, NULL, th->th_seq, *tlenp, TCP_R_LOG_ZERO, 0);
#endif
tp->t_segqmbuflen = 0;
#endif
}
#ifdef TCP_REASS_LOGGING
tcp_reass_log_dump(tp);
#endif
sorwakeup_locked(so);
return (flags);
}
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