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Improve r265338. When inserting mbufs into TCP reassembly queue,

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try to collapse adjacent pieces using m_catpkt(). In best case
scenario it copies data and frees mbufs, making mbuf exhaustion
attack harder.

Suggested by:		Jonathan Looney <jonlooney gmail.com>
Security:		Hardens against remote mbuf exhaustion attack.
Sponsored by:		Netflix
Sponsored by:		Nginx, Inc.
This commit is contained in:
Gleb Smirnoff 2014-09-04 09:15:44 +00:00
parent 1967edba02
commit ba32fcfff9
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=271089
1 changed files with 20 additions and 7 deletions
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27
sys/netinet/tcp_reass.c
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@ -214,16 +214,29 @@ tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m)
mq = nq;
}
/* Insert the new segment queue entry into place. */
/*
* Insert the new segment queue entry into place. Try to collapse
* mbuf chains if segments are adjacent.
*/
if (mp) {
m->m_nextpkt = mp->m_nextpkt;
mp->m_nextpkt = m;
if (M_TCPHDR(mp)->th_seq + mp->m_pkthdr.len == th->th_seq)
m_catpkt(mp, m);
else {
m->m_nextpkt = mp->m_nextpkt;
mp->m_nextpkt = m;
m->m_pkthdr.pkt_tcphdr = th;
}
} else {
m->m_nextpkt = tp->t_segq;
tp->t_segq = m ;
mq = tp->t_segq;
tp->t_segq = m;
if (mq && th->th_seq + *tlenp == M_TCPHDR(mq)->th_seq) {
m->m_nextpkt = mq->m_nextpkt;
m_catpkt(m, mq);
} else
m->m_nextpkt = mq;
m->m_pkthdr.pkt_tcphdr = th;
}
m->m_pkthdr.pkt_tcphdr = th;
tp->t_segqlen += m->m_pkthdr.len;
tp->t_segqlen += *tlenp;
present:
/*