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MFC r298408:

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Prevent underflows in tp->snd_wnd if the remote side ACKs more than
  tp->snd_wnd. This can happen, for example, when the remote side responds
  to a window probe by ACKing the one byte it contains.
This commit is contained in:
jtl 2016-05-06 01:26:58 +00:00
parent 5cba75d7c7
commit fdef3ab021
1 changed files with 11 additions and 2 deletions
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13
sys/netinet/tcp_input.c
View File

@ -2733,6 +2733,9 @@ process_ACK:
INP_WLOCK_ASSERT(tp->t_inpcb);
acked = BYTES_THIS_ACK(tp, th);
KASSERT(acked >= 0, ("%s: acked unexepectedly negative "
"(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__,
tp->snd_una, th->th_ack, tp, m));
TCPSTAT_INC(tcps_rcvackpack);
TCPSTAT_ADD(tcps_rcvackbyte, acked);
@ -2802,13 +2805,19 @@ process_ACK:
SOCKBUF_LOCK(&so->so_snd);
if (acked > so->so_snd.sb_cc) {
tp->snd_wnd -= so->so_snd.sb_cc;
if (tp->snd_wnd >= so->so_snd.sb_cc)
tp->snd_wnd -= so->so_snd.sb_cc;
else
tp->snd_wnd = 0;
mfree = sbcut_locked(&so->so_snd,
(int)so->so_snd.sb_cc);
ourfinisacked = 1;
} else {
mfree = sbcut_locked(&so->so_snd, acked);
tp->snd_wnd -= acked;
if (tp->snd_wnd >= (u_long) acked)
tp->snd_wnd -= acked;
else
tp->snd_wnd = 0;
ourfinisacked = 0;
}
/* NB: sowwakeup_locked() does an implicit unlock. */