Re: panic in TCP Limited Transmit after RTO
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Limited Transmit is supposed to send new data, and, we are out of SACK recovery at this point, so I think we can safely ignore any old SACK blocks. Please try this patch.
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Index: tcp_input.c
===================================================================
RCS file: /j/dragonfly/dcvs/src/sys/netinet/tcp_input.c,v
retrieving revision 1.54
diff -u -p -r1.54 tcp_input.c
--- tcp_input.c 9 Mar 2005 06:57:29 -0000 1.54
+++ tcp_input.c 12 Mar 2005 22:28:35 -0000
@@ -1954,9 +1954,10 @@ fastretransmit:
(tp->t_dupacks - tp->snd_limited);
} else if (tcp_do_limitedtransmit) {
u_long oldcwnd = tp->snd_cwnd;
- tcp_seq oldsndmax = tp->snd_max;
+ u_long oldssthresh = tp->snd_ssthresh;
+ tcp_seq oldsndnxt = tp->snd_nxt;
/* outstanding data */
- uint32_t ownd = tp->snd_max - tp->snd_una;
+ uint32_t ownd = tp->snd_nxt - tp->snd_una;
u_int sent;
#define iceildiv(n, d) (((n)+(d)-1) / (d))
@@ -1969,9 +1970,11 @@ fastretransmit:
tp->snd_cwnd = ownd +
(tp->t_dupacks - tp->snd_limited) *
tp->t_maxseg;
+ tp->snd_ssthresh = tp->snd_cwnd;
tcp_output(tp);
tp->snd_cwnd = oldcwnd;
- sent = tp->snd_max - oldsndmax;
+ tp->snd_ssthresh = oldssthresh;
+ sent = tp->snd_nxt - oldsndnxt;
if (sent > tp->t_maxseg) {
KASSERT((tp->t_dupacks == 2 &&
tp->snd_limited == 0) ||
Index: tcp_output.c
===================================================================
RCS file: /j/dragonfly/dcvs/src/sys/netinet/tcp_output.c,v
retrieving revision 1.25
diff -u -p -r1.25 tcp_output.c
--- tcp_output.c 9 Mar 2005 06:54:34 -0000 1.25
+++ tcp_output.c 12 Mar 2005 22:23:00 -0000
@@ -193,13 +193,13 @@ tcp_output(tp)
else
tp->t_flags &= ~TF_LASTIDLE;
- if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
+ if (TCP_DO_SACK(tp) && (tp->snd_cwnd < tp->snd_ssthresh) &&
!IN_FASTRECOVERY(tp))
nsacked = tcp_sack_bytes_below(&tp->scb, tp->snd_nxt);
again:
/* Make use of SACK information when slow-starting after a RTO. */
- if (TCP_DO_SACK(tp) && tp->snd_nxt != tp->snd_max &&
+ if (TCP_DO_SACK(tp) && (tp->snd_cwnd < tp->snd_ssthresh) &&
!IN_FASTRECOVERY(tp)) {
tcp_seq old_snd_nxt = tp->snd_nxt;
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