tcp: fix fib index buffer tagging

Change-Id: I373cc252df3621d44879b8eca70aed17d7752a2a
Signed-off-by: Florin Coras <fcoras@cisco.com>
diff --git a/src/vnet/tcp/tcp_input.c b/src/vnet/tcp/tcp_input.c
index 07f1838..3b37bcd 100644
--- a/src/vnet/tcp/tcp_input.c
+++ b/src/vnet/tcp/tcp_input.c
@@ -2757,6 +2757,7 @@
 	  child0->c_rmt_port = th0->src_port;
 	  child0->c_is_ip4 = is_ip4;
 	  child0->state = TCP_STATE_SYN_RCVD;
+	  child0->c_fib_index = lc0->c_fib_index;
 
 	  if (is_ip4)
 	    {