Date: Mon, 6 Apr 2009 09:57:13 +0200 From: "Blapp, Martin" <Martin.Blapp@t-systems.ch> To: "freebsd-stable@freebsd.org" <freebsd-stable@freebsd.org> Subject: AW: FreeBSD 7.2-BETA1 tcp retransmit crash Message-ID: <509A7CA1EA3EA046B1A5BA2FCFDB3C8EC764853902@TSS-EXCH01.t-systems.ch> In-Reply-To: <20090405180621.F15361@maildrop.int.zabbadoz.net> References: <509A7CA1EA3EA046B1A5BA2FCFDB3C8EC764853900@TSS-EXCH01.t-systems.ch> <20090405163705.U15361@maildrop.int.zabbadoz.net>, <20090405180621.F15361@maildrop.int.zabbadoz.net>
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Hi,
(kgdb) frame 7
#7 0xc07c6cb0 in sbsndptr (sb=0xc342ede4, off=112, len=113, moff=0xc2f9ca04) at /usr/src/sys/kern/uipc_sockbuf.c:939
This is also interesting. Is this an OffByOne somewhere ?
As I said it's just a workaround, and for now it didn't crash anymore :-)
I could modify this patch to see what happens exactly, dumpping the mbuf.
The workaround I currently use is just skipping and dropping this mbuf:
--- sys/kern/uipc_sockbuf.c.orig 2009-04-05 18:01:35.000000000 +0200
+++ sys/kern/uipc_sockbuf.c 2009-04-05 18:01:46.000000000 +0200
@@ -930,6 +930,13 @@
return (sb->sb_mb);
}
+ /*
+ * Try to avoid some retransmit panics
+ */
+ if (sb->sb_sndptr == NULL && sb->sb_mb == NULL) {
+ return (NULL);
+ }
+
/* Return closest mbuf in chain for current offset. */
*moff = off - sb->sb_sndptroff;
m = ret = sb->sb_sndptr ? sb->sb_sndptr : sb->sb_mb;
--- sys/netinet/tcp_output.c.orig 2009-04-05 18:01:29.000000000 +0200
+++ sys/netinet/tcp_output.c 2009-04-05 18:04:17.000000000 +0200
@@ -797,6 +797,17 @@
*/
mb = sbsndptr(&so->so_snd, off, len, &moff);
+
+ /*
+ * Avoid panics. Mask the error with ENETDOWN
+ */
+ if (mb == NULL) {
+ SOCKBUF_UNLOCK(&so->so_snd);
+ (void) m_free(m);
+ error = ENETDOWN;
+ goto out;
+ }
+
if (len <= MHLEN - hdrlen - max_linkhdr) {
m_copydata(mb, moff, (int)len,
mtod(m, caddr_t) + hdrlen);
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