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freebsd-skq/sys/netinet/tcp_reass.c
rrs f87b4f4276 This change represents a substantial restructure of the way we 
reassembly inbound tcp segments. The old algorithm just blindly
dropped in segments without coalescing. This meant that every
segment could take up greater and greater room on the linked list
of segments. This of course is now subject to a tighter limit (100)
of segments which in a high BDP situation will cause us to be a
lot more in-efficent as we drop segments beyond 100 entries that
we receive. What this restructure does is cause the reassembly
buffer to coalesce segments putting an emphasis on the two
common cases (which avoid walking the list of segments) i.e.
where we add to the back of the queue of segments and where we
add to the front. We also have the reassembly buffer supporting
a couple of debug options (black box logging as well as counters
for code coverage). These are compiled out by default but can
be added by uncommenting the defines.

Sponsored by:	Netflix Inc.
Differential Revision:	https://reviews.freebsd.org/D16626
2018-08-20 12:43:18 +00:00

1079 lines
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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 tseg_qent tqs;
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 ((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
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 (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 ((th->th_seq != tp->rcv_nxt || !TCPS_HAVEESTABLISHED(tp->t_state)) &&
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;
if (q != &tqs)
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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