[ovs-dev] [PATCH] packets: fix l4 pseudo csum incremental update

Jun Xiao jun.xiao at cloudnetengine.com
Tue Nov 23 16:16:36 UTC 2021


When a packet requests l4 csum offload, the l4 csum field includes
a pseudo csum instead of a full csum. The pseudo csum doesn't do
the final one's complement, and it must be updated differently
than a full csum.

Signed-off-by: Jun Xiao <jun.xiao at cloudnetengine.com>
---
 lib/packets.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/packets.c b/lib/packets.c
index 4a7643c5d..910d14379 100644
--- a/lib/packets.c
+++ b/lib/packets.c
@@ -1088,11 +1088,17 @@ packet_set_ipv4_addr(struct dp_packet *packet,
         struct tcp_header *th = dp_packet_l4(packet);
 
         th->tcp_csum = recalc_csum32(th->tcp_csum, old_addr, new_addr);
+        if (dp_packet_hwol_tx_l4_checksum(packet)) {
+            th->tcp_csum = ~th->tcp_csum;
+        }
     } else if (nh->ip_proto == IPPROTO_UDP && l4_size >= UDP_HEADER_LEN ) {
         struct udp_header *uh = dp_packet_l4(packet);
 
         if (uh->udp_csum) {
             uh->udp_csum = recalc_csum32(uh->udp_csum, old_addr, new_addr);
+            if (dp_packet_hwol_tx_l4_checksum(packet)) {
+                uh->udp_csum = ~uh->udp_csum;
+            }
             if (!uh->udp_csum) {
                 uh->udp_csum = htons(0xffff);
             }
@@ -1196,11 +1202,17 @@ packet_update_csum128(struct dp_packet *packet, uint8_t proto,
         struct tcp_header *th = dp_packet_l4(packet);
 
         th->tcp_csum = recalc_csum128(th->tcp_csum, addr, new_addr);
+        if (dp_packet_hwol_tx_l4_checksum(packet)) {
+            th->tcp_csum = ~th->tcp_csum;
+        }
     } else if (proto == IPPROTO_UDP && l4_size >= UDP_HEADER_LEN) {
         struct udp_header *uh = dp_packet_l4(packet);
 
         if (uh->udp_csum) {
             uh->udp_csum = recalc_csum128(uh->udp_csum, addr, new_addr);
+            if (dp_packet_hwol_tx_l4_checksum(packet)) {
+                uh->udp_csum = ~uh->udp_csum;
+            }
             if (!uh->udp_csum) {
                 uh->udp_csum = htons(0xffff);
             }
-- 
2.25.1



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