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In a situation where:

Browse Source 
- The remote host sends a FIN
	- in an ACK for a sequence number for which an ACK has already
	  been received
	- There is still unacked data on route to the remote host
	- The packet does not contain a window update

The packet may be dropped without processing the FIN flag.

PR:		kern/99188
Submitted by:	Staffan Ulfberg <staffan@ulfberg.se>
Discussed with:	andre
MFC after:	never
This commit is contained in:
Eitan Adler 2013-12-02 03:11:25 +00:00
parent ca38150ce3
commit 5f30ec9b63
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=258821
1 changed files with 4 additions and 2 deletions
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6
sys/netinet/tcp_input.c
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@ -2429,13 +2429,15 @@ tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
hhook_run_tcp_est_in(tp, th, &to);
if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
if (tlen == 0 && tiwin == tp->snd_wnd) {
if (tlen == 0 && tiwin == tp->snd_wnd &&
!(thflags & TH_FIN)) {
TCPSTAT_INC(tcps_rcvdupack);
/*
* If we have outstanding data (other than
* a window probe), this is a completely
* duplicate ack (ie, window info didn't
* change), the ack is the biggest we've
* change and FIN isn't set),
* the ack is the biggest we've
* seen and we've seen exactly our rexmt
* threshhold of them, assume a packet
* has been dropped and retransmit it.