The following reply was made to PR kern/177456; it has been noted by GNATS.
From: Gleb Smirnoff <gleb...@freebsd.org>
To: ?????? <lglion...@163.com>
Cc: bug-follo...@freebsd.org
Subject: Re: misc/177456: An error of calculating TCP sequence number will
resault in the machine to restart
Date: Wed, 3 Apr 2013 19:21:12 +0400
Hi!
On Wed, Apr 03, 2013 at 07:52:42AM +0800, ?????? wrote:
?> I mean there is a bug in FreeBSD's tcp code. I'm trying to describe it by
pictuer. Pelease see the attachments??
I am trying to model what you are describing in the picture by
special crafted code.
I intentionally model memory allocation failure on first two
packets for a connection that has special socket option.
I'm modelling allocation failure at tcp_output.c near line 900:
Index: tcp_output.c
===================================================================
--- tcp_output.c (revision 249051)
+++ tcp_output.c (working copy)
@@ -898,6 +898,13 @@ send:
else
TCPSTAT_INC(tcps_sndwinup);
+ /* Fail allocating first 2 packets. */
+ if (tp->t_flags & TF_ZHOPA && tp->t_zhopa < 2) {
+ tp->t_zhopa++;
+ m = NULL;
+ error = ENOBUFS;
+ goto out;
+ } else
m = m_gethdr(M_NOWAIT, MT_DATA);
if (m == NULL) {
error = ENOBUFS;
I have no success in reproducing your problems. With above code,
first 2 packets are failing to allocate, but third retransmission
succeeds and connection is established with no problems.
May be I incorrectly understand your description :( Please don't
give up and try to explain again.
A modelling code that demonstrates problem would be appreciated.
--
Totus tuus, Glebius.
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