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/*
* Copyright (c) 2018-2023, OARC, Inc.
* 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 copyright holder 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDER 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.
*/
#include "config.h"
#include "tcpstate.h"
#include "iaddr.h"
#include "log.h"
#include "tcpreasm.h"
#include "hashtbl.h"
#ifndef s6_addr32
#define s6_addr32 __u6_addr.__u6_addr32
#endif
#define MAX_TCP_IDLE_TIME 600
#define MAX_TCP_IDLE_COUNT 4096
#define TCP_GC_TIME 60
static hashtbl* _hash = 0;
tcpstate_ptr tcpstate_find(iaddr from, iaddr to, unsigned sport, unsigned dport, time_t t)
{
static time_t next_gc = 0;
tcpstate_ptr tcpstate;
#ifndef __clang_analyzer__
/* disabled during scan-build due to false-positives */
if (t >= next_gc || tcpstate_count > MAX_TCP_IDLE_COUNT) {
/* garbage collect stale states */
while ((tcpstate = TAIL(tcpstates)) && tcpstate->last_use < t - MAX_TCP_IDLE_TIME) {
tcpstate_discard(tcpstate, "gc stale");
}
next_gc = t + TCP_GC_TIME;
}
#endif
tcpstate_key key = {
.saddr = &from,
.daddr = &to,
.sport = sport,
.dport = dport
};
tcpstate = hash_find(&key, _hash);
if (tcpstate != NULL) {
tcpstate->last_use = t;
if (tcpstate != HEAD(tcpstates)) {
/* move to beginning of list */
UNLINK(tcpstates, tcpstate, link);
PREPEND(tcpstates, tcpstate, link);
}
}
return tcpstate;
}
unsigned int tcpstate_hash(const tcpstate_key* key)
{
uint32_t h = 0;
switch (key->saddr->af) {
case AF_INET:
h = hashword(&key->saddr->u.a4.s_addr, 1, h);
break;
case AF_INET6:
h = hashword(key->saddr->u.a6.s6_addr32, 4, h);
break;
}
switch (key->daddr->af) {
case AF_INET:
h = hashword(&key->daddr->u.a4.s_addr, 1, h);
break;
case AF_INET6:
h = hashword(key->daddr->u.a6.s6_addr32, 4, h);
break;
}
uint32_t p = (key->sport << 16) | (key->dport & 0xffff);
return hashword(&p, 1, h);
}
int tcpstate_cmp(const tcpstate_key* a, const tcpstate_key* b)
{
if (ia_equalp(a->saddr, b->saddr) && ia_equalp(a->daddr, b->daddr) && a->sport == b->sport && a->dport == b->dport)
return 0;
return 1;
}
tcpstate_ptr _curr_tcpstate = 0;
tcpstate_ptr tcpstate_new(iaddr from, iaddr to, unsigned sport, unsigned dport)
{
if (!_hash) {
_hash = hash_create(65535, (hashkey_func)tcpstate_hash, (hashkeycmp_func)tcpstate_cmp, 0);
assert(_hash);
}
tcpstate_ptr tcpstate = calloc(1, sizeof *tcpstate);
if (tcpstate == NULL) {
/* Out of memory; recycle the least recently used */
logerr("warning: out of memory, "
"discarding some TCP state early");
tcpstate = TAIL(tcpstates);
assert(tcpstate != NULL);
UNLINK(tcpstates, tcpstate, link);
if (tcpstate->reasm) {
tcpreasm_free(tcpstate->reasm);
}
if (_curr_tcpstate == tcpstate) {
_curr_tcpstate = 0;
}
hash_remove(&tcpstate->key, _hash);
memset(tcpstate, 0, sizeof(*tcpstate));
} else {
tcpstate_count++;
}
tcpstate->saddr = from;
tcpstate->daddr = to;
tcpstate->sport = sport;
tcpstate->dport = dport;
INIT_LINK(tcpstate, link);
PREPEND(tcpstates, tcpstate, link);
tcpstate->key.saddr = &tcpstate->saddr;
tcpstate->key.daddr = &tcpstate->daddr;
tcpstate->key.sport = sport;
tcpstate->key.dport = dport;
hash_add(&tcpstate->key, tcpstate, _hash);
return tcpstate;
}
tcpstate_ptr tcpstate_getcurr(void)
{
return _curr_tcpstate;
}
/* Discard this packet. If it's part of TCP stream, all subsequent pkts on
* the same tcp stream will also be discarded. */
void tcpstate_discard(tcpstate_ptr tcpstate, const char* msg)
{
if (dumptrace >= 3 && msg)
fprintf(stderr, "discarding packet: %s\n", msg);
if (tcpstate) {
UNLINK(tcpstates, tcpstate, link);
if (tcpstate->reasm) {
tcpreasm_free(tcpstate->reasm);
}
hash_remove(&tcpstate->key, _hash);
free(tcpstate);
if (_curr_tcpstate == tcpstate) {
_curr_tcpstate = 0;
}
tcpstate_count--;
}
}
void tcpstate_reset(tcpstate_ptr tcpstate, const char* msg)
{
if (options.allow_reset_tcpstate && tcpstate) {
if (dumptrace >= 3 && msg)
fprintf(stderr, "resetting tcpstate: %s\n", msg);
tcpstate->start = tcpstate->currseq;
tcpstate->maxdiff = 0;
tcpstate->dnslen = 0;
tcpstate->lastdns = tcpstate->currseq + tcpstate->currlen;
if (tcpstate->reasm) {
tcpreasm_reset(tcpstate->reasm);
tcpstate->reasm->seq_start = tcpstate->start;
}
}
}
void tcpstate_free(tcpstate_ptr tcpstate)
{
if (tcpstate) {
UNLINK(tcpstates, tcpstate, link);
if (tcpstate->reasm) {
tcpreasm_free(tcpstate->reasm);
}
hash_remove(&tcpstate->key, _hash);
free(tcpstate);
if (_curr_tcpstate == tcpstate) {
_curr_tcpstate = 0;
}
tcpstate_count--;
}
}
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