vxlan: reuse inner packet flow hash for tunnel outer header load balance

Type: fix

Several tunnels encapsulation use udp as outer header and udp src port
is set by inner header flow hash, such as gtpu, geneve, vxlan, vxlan-gbd
Since flow hash of inner header is already been calculated, keeping it
to vnet_buffere[b]->ip.flow_hash should save load-balance node work to
select ECMP uplinks.

Change-Id: I0e4e2b27178f4fcc5785e221d6d1f3e8747d0d59
Signed-off-by: Shawn Ji <xiaji@tethrnet.com>
diff --git a/src/vnet/vxlan-gbp/encap.c b/src/vnet/vxlan-gbp/encap.c
index 4bba49a..a606b89 100644
--- a/src/vnet/vxlan-gbp/encap.c
+++ b/src/vnet/vxlan-gbp/encap.c
@@ -309,6 +309,10 @@
 		udp1->checksum = 0xffff;
 	    }
 
+	  /* save inner packet flow_hash for load-balance node */
+	  vnet_buffer (b[0])->ip.flow_hash = flow_hash0;
+	  vnet_buffer (b[1])->ip.flow_hash = flow_hash1;
+
 	  vlib_increment_combined_counter (tx_counter, thread_index,
 					   sw_if_index0, 1, len0);
 	  vlib_increment_combined_counter (tx_counter, thread_index,
@@ -451,6 +455,9 @@
 		udp0->checksum = 0xffff;
 	    }
 
+	  /* save inner packet flow_hash for load-balance node */
+	  vnet_buffer (b[0])->ip.flow_hash = flow_hash0;
+
 	  vlib_increment_combined_counter (tx_counter, thread_index,
 					   sw_if_index0, 1, len0);
 	  pkts_encapsulated++;