sepherosa_gmail.com created this revision.
sepherosa_gmail.com added reviewers: rrs, gallatin, hselasky, np, glebius.
sepherosa_gmail.com added a subscriber: freebsd-net-list.
Herald added a reviewer: transport.
REVISION SUMMARY
This keeps the segments/ACK/FIN delivery order.
Before this patch, it was observed: if A sent FIN immediately after
an ACK, B would deliver FIN first to the TCP stack, then the ACK.
This out-of-order delivery causes one unnecessary ACK sent from B.
Obtained from: gallatin, rrs
REVISION DETAIL
https://reviews.freebsd.org/D7415
AFFECTED FILES
sys/netinet/tcp_lro.c
EMAIL PREFERENCES
https://reviews.freebsd.org/settings/panel/emailpreferences/
To: sepherosa_gmail.com, #transport, rrs, gallatin, hselasky, np, glebius
Cc: freebsd-net-list
diff --git a/sys/netinet/tcp_lro.c b/sys/netinet/tcp_lro.c
--- a/sys/netinet/tcp_lro.c
+++ b/sys/netinet/tcp_lro.c
@@ -603,6 +603,7 @@
int error, ip_len, l;
uint16_t eh_type, tcp_data_len;
struct lro_head *bucket;
+ int force_flush = 0;
/* We expect a contiguous header [eh, ip, tcp]. */
@@ -669,8 +670,15 @@
* Check TCP header constraints.
*/
/* Ensure no bits set besides ACK or PSH. */
- if ((th->th_flags & ~(TH_ACK | TH_PUSH)) != 0)
- return (TCP_LRO_CANNOT);
+ if ((th->th_flags & ~(TH_ACK | TH_PUSH)) != 0) {
+ if (th->th_flags & TH_SYN)
+ return (TCP_LRO_CANNOT);
+ /*
+ * Make sure that previously seen segements/ACKs are delivered
+ * before this segement, e.g. FIN.
+ */
+ force_flush = 1;
+ }
/* XXX-BZ We lose a ACK|PUSH flag concatenating multiple segments. */
/* XXX-BZ Ideally we'd flush on PUSH? */
@@ -686,8 +694,13 @@
ts_ptr = (uint32_t *)(th + 1);
if (l != 0 && (__predict_false(l != TCPOLEN_TSTAMP_APPA) ||
(*ts_ptr != ntohl(TCPOPT_NOP<<24|TCPOPT_NOP<<16|
- TCPOPT_TIMESTAMP<<8|TCPOLEN_TIMESTAMP))))
- return (TCP_LRO_CANNOT);
+ TCPOPT_TIMESTAMP<<8|TCPOLEN_TIMESTAMP)))) {
+ /*
+ * Make sure that previously seen segements/ACKs are delivered
+ * before this segement.
+ */
+ force_flush = 1;
+ }
/* If the driver did not pass in the checksum, set it now. */
if (csum == 0x0000)
@@ -754,6 +767,13 @@
#endif
}
+ if (force_flush) {
+ /* Timestamps mismatch; this is a FIN, etc */
+ tcp_lro_active_remove(le);
+ tcp_lro_flush(lc, le);
+ return (TCP_LRO_CANNOT);
+ }
+
/* Flush now if appending will result in overflow. */
if (le->p_len > (lc->lro_length_lim - tcp_data_len)) {
tcp_lro_active_remove(le);
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