Author: cperciva
Date: Tue Jul 5 18:43:54 2011
New Revision: 223797
URL: http://svn.freebsd.org/changeset/base/223797
Log:
Don't allow lro->len to exceed 65535, as this will result in overflow
when len is inserted back into the synthetic IP packet and cause a
multiple of 2^16 bytes of TCP "packet loss".
This improves Linux->FreeBSD netperf bandwidth by a factor of 300 in
testing on Amazon EC2.
Reviewed by: jfv
MFC after: 2 weeks
Modified:
head/sys/netinet/tcp_lro.c
Modified: head/sys/netinet/tcp_lro.c
==============================================================================
--- head/sys/netinet/tcp_lro.c Tue Jul 5 18:42:10 2011 (r223796)
+++ head/sys/netinet/tcp_lro.c Tue Jul 5 18:43:54 2011 (r223797)
@@ -277,6 +277,14 @@ tcp_lro_rx(struct lro_ctrl *cntl, struct
lro->dest_port == tcp->th_dport &&
lro->source_ip == ip->ip_src.s_addr &&
lro->dest_ip == ip->ip_dst.s_addr) {
+ /* Flush now if appending will result in overflow. */
+ if (lro->len > (65535 - tcp_data_len)) {
+ SLIST_REMOVE(&cntl->lro_active, lro,
+ lro_entry, next);
+ tcp_lro_flush(cntl, lro);
+ break;
+ }
+
/* Try to append it */
if (__predict_false(seq != lro->next_seq ||
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