From: Dave Barach <dave@barachs.net>
Date: Fri, 29 May 2020 20:34:50 +0000 (-0400)
Subject: nat: update ip4-udp src port for checksum == 0 pkts
X-Git-Tag: v21.01-rc0~322
X-Git-Url: https://gerrit.fd.io/r/gitweb?a=commitdiff_plain;h=refs%2Fchanges%2F47%2F27347%2F2;p=vpp.git

nat: update ip4-udp src port for checksum == 0 pkts

Otherwise, the out2in path will discard return-path traffic with
probability 1.0.

Type: fix
Fixes: gerrit 23963 / f126e746fc01c75bc99329d10ce9127b26b23814

Signed-off-by: Dave Barach <dave@barachs.net>
Change-Id: I621ed99329c04ef358035747dde599c0016b58f5
---

diff --git a/src/plugins/nat/in2out.c b/src/plugins/nat/in2out.c
index 8f92bae0302..a448867cd4f 100644
--- a/src/plugins/nat/in2out.c
+++ b/src/plugins/nat/in2out.c
@@ -1118,10 +1118,11 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
 	    {
 	      if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
 		{
+		  udp0->src_port = s0->out2in.port;
 		  if (PREDICT_FALSE (udp0->checksum))
 		    {
 		      old_port0 = vnet_buffer (b0)->ip.reass.l4_src_port;
-		      new_port0 = udp0->src_port = s0->out2in.port;
+		      new_port0 = udp0->src_port;
 		      sum0 = udp0->checksum;
 		      sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t, dst_address	/* changed member */
 			);
@@ -1325,10 +1326,11 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
 	    {
 	      if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
 		{
+		  udp1->src_port = s1->out2in.port;
 		  if (PREDICT_FALSE (udp1->checksum))
 		    {
 		      old_port1 = vnet_buffer (b1)->ip.reass.l4_src_port;
-		      new_port1 = udp1->src_port = s1->out2in.port;
+		      new_port1 = udp1->src_port;
 		      sum1 = udp1->checksum;
 		      sum1 = ip_csum_update (sum1, old_addr1, new_addr1, ip4_header_t, dst_address	/* changed member */
 			);
@@ -1567,10 +1569,11 @@ snat_in2out_node_fn_inline (vlib_main_t * vm,
 	    {
 	      if (!vnet_buffer (b0)->ip.reass.is_non_first_fragment)
 		{
+		  udp0->src_port = s0->out2in.port;
 		  if (PREDICT_FALSE (udp0->checksum))
 		    {
 		      old_port0 = vnet_buffer (b0)->ip.reass.l4_src_port;
-		      new_port0 = udp0->src_port = s0->out2in.port;
+		      new_port0 = udp0->src_port;
 		      sum0 = udp0->checksum;
 		      sum0 = ip_csum_update (sum0, old_addr0, new_addr0, ip4_header_t, dst_address	/* changed member */
 			);