map: Fix TCP MSS clamping for MAP-E traffic.

[vpp.git] / src / plugins / map / ip4_map.c

diff --git a/src/plugins/map/ip4_map.c b/src/plugins/map/ip4_map.c
index f2a0090..68c3d73 100644 (file)
--- a/src/plugins/map/ip4_map.c
+++ b/src/plugins/map/ip4_map.c
@@ -209,6 +209,20 @@ ip4_map (vlib_main_t * vm, vlib_node_runtime_t * node, vlib_frame_t * frame)
           */
          port0 = ip4_map_port_and_security_check (d0, p0, &error0);
 
+         /*
+          * Clamp TCP MSS value.
+          */
+         if (ip40->protocol == IP_PROTOCOL_TCP)
+           {
+             tcp_header_t *tcp = ip4_next_header (ip40);
+             if (mm->tcp_mss > 0 && tcp_syn (tcp))
+               {
+                 ip_csum_t csum = tcp->checksum;
+                 map_mss_clamping (tcp, &csum, mm->tcp_mss);
+                 tcp->checksum = ip_csum_fold (csum);
+               }
+           }
+
          /* Decrement IPv4 TTL */
          ip4_map_decrement_ttl (ip40, &error0);
          bool df0 =