Re: [Qemu-devel] [PATCH v2 3/3] filter-rewriter: skip net_checksum_calculate() while offset = 0

[Zhang Chen]

On 02/27/2017 09:36 AM, Hailiang Zhang wrote:

On 2017/2/24 16:08, Zhang Chen wrote:

On 02/22/2017 11:46 AM, zhanghailiang wrote:

While the offset of packets's sequence for primary side and

secondary side is zero, it is unnecessary to call net_checksum_calculate()

to recalculate the checksume value of packets.

Signed-off-by: zhanghailiang <zhang.zhanghaili...@huawei.com>
---
   net/filter-rewriter.c | 18 +++++++++++-------
   1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/net/filter-rewriter.c b/net/filter-rewriter.c
index 7e7ec35..c9a6d43 100644
--- a/net/filter-rewriter.c
+++ b/net/filter-rewriter.c

@@ -93,10 +93,12 @@ static int handle_primary_tcp_pkt(RewriterState *rf,

               conn->offset -= (ntohl(tcp_pkt->th_ack) - 1);
               conn->syn_flag = 0;
           }
-        /* handle packets to the secondary from the primary */

- tcp_pkt->th_ack = htonl(ntohl(tcp_pkt->th_ack) + conn->offset);

+        if (conn->offset) {

This is wrong, conn->offset maybe is a negative value(like -1000),
So you can change here to  "if (conn->offset == 0) {"

Er, if it is a negative value, it can still go into this if (conn->offset)

branch, and we need to adjust the checksum value in this case.

Sorry, I misunderstand it, ignore.

Thanks
Zhang Chen

+            /* handle packets to the secondary from the primary */

+ tcp_pkt->th_ack = htonl(ntohl(tcp_pkt->th_ack) + conn->offset);

-        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+            net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+        }
           /*
            * Case 1:

* The *server* side of this connect is VM, *client* tries to close @@ -112,7 +114,6 @@ static int handle_primary_tcp_pkt(RewriterState *rf,

            */
           if ((conn->tcp_state == TCPS_LAST_ACK) &&
               (ntohl(tcp_pkt->th_ack) == (conn->fin_ack_seq + 1))) {
-            fprintf(stderr, "Remove conn "

Here need fix.

OK.

g_hash_table_remove(rf->connection_track_table, key);
           }
       }

@@ -159,10 +160,13 @@ static int handle_secondary_tcp_pkt(RewriterState *rf,

       }

       if ((tcp_pkt->th_flags & (TH_ACK | TH_SYN)) == TH_ACK) {
-        /* handle packets to the primary from the secondary*/

- tcp_pkt->th_seq = htonl(ntohl(tcp_pkt->th_seq) - conn->offset);

+        /* Only need to adjust seq while offset is Non-zero */
+        if (conn->offset) {

Refer to the above comments.

Thanks
Zhang Chen

+            /* handle packets to the primary from the secondary*/

+ tcp_pkt->th_seq = htonl(ntohl(tcp_pkt->th_seq) - conn->offset);

-        net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+            net_checksum_calculate((uint8_t *)pkt->data, pkt->size);
+        }
           /*
            * Case 2:

* The *server* side of this connect is VM, *server* tries to close

.

--
Thanks
Zhang Chen