[Qemu-devel] [PATCH V2 1/2] COLO-compare: Optimize tcp compare for option field

[Zhang Chen <zhangchen.fnst@cn.fujitsu.com>]

In this patch we support packet that have tcp options field.
Add tcp options field check, If the packet have options
field we just skip it and compare tcp payload,
Avoid unnecessary checkpoint, optimize performance.

Signed-off-by: Zhang Chen <zhangchen.fnst@cn.fujitsu.com>
---
 net/colo-compare.c | 27 ++++++++++++++++++++++++++-
 1 file changed, 26 insertions(+), 1 deletion(-)

diff --git a/net/colo-compare.c b/net/colo-compare.c
index aada04e..049f6f8 100644
--- a/net/colo-compare.c
+++ b/net/colo-compare.c
@@ -248,7 +248,32 @@ static int colo_packet_compare_tcp(Packet *spkt, Packet *ppkt)
         spkt->ip->ip_sum = ppkt->ip->ip_sum;
     }
 
-    if (ptcp->th_sum == stcp->th_sum) {
+    /*
+     * Check tcp header length for tcp option field.
+     * th_off > 5 means this tcp packet have options field.
+     * The tcp options maybe always different.
+     * for example:
+     * From RFC 7323.
+     * TCP Timestamps option (TSopt):
+     * Kind: 8
+     *
+     * Length: 10 bytes
+     *
+     *    +-------+-------+---------------------+---------------------+
+     *    |Kind=8 |  10   |   TS Value (TSval)  |TS Echo Reply (TSecr)|
+     *    +-------+-------+---------------------+---------------------+
+     *       1       1              4                     4
+     *
+     * In this case the primary guest's timestamp always different with
+     * the secondary guest's timestamp. COLO just focus on payload,
+     * so we just need skip this field.
+     */
+    if (ptcp->th_off > 5) {
+        ptrdiff_t tcp_offset;
+        tcp_offset = ppkt->transport_header - (uint8_t *)ppkt->data
+                     + (ptcp->th_off * 4);
+        res = colo_packet_compare_common(ppkt, spkt, tcp_offset);
+    } else if (ptcp->th_sum == stcp->th_sum) {
         res = colo_packet_compare_common(ppkt, spkt, ETH_HLEN);
     } else {
         res = -1;
-- 
2.7.4