commit aa7cfd04e7bb89208afe57cd84e96ced32153044
author Neale Ranns <neale@graphiant.com> Thu Mar 24 12:28:42 2022 +0000
committer Florin Coras <florin.coras@gmail.com> Thu Mar 24 15:39:16 2022 +0000
tree 7eb689d8d54aa30930c889b78de594d068e4e169
parent e99f762346ae018ce5b76b729a12f0cd091aec43

ip: The check for 'same packet' must include the FIB index

Type: fix

otherwise if two packets arrive with the same source address but from different VRFs, then they are treated as the same and they use the same LB and thus share the same fate. but the lookup, when done, results in two different LBs, and hence the fate can be different.

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: Id6e16f7c577a561d9ddd7066339fa4385361d07f

src/vnet/ip/ip4_forward.c

diff --git a/src/vnet/ip/ip4_forward.c b/src/vnet/ip/ip4_forward.c
index 3556d35..c1bfc7d 100644
--- a/src/vnet/ip/ip4_forward.c
+++ b/src/vnet/ip/ip4_forward.c
@@ -1517,7 +1517,9 @@
 
 typedef struct
 {
+  /* The src and fib-index together determine if packet n is the same as n-1 */
   ip4_address_t src;
+  u32 fib_index;
   u32 lbi;
   u8 error;
   u8 first;
@@ -1551,7 +1553,8 @@
    * vnet_buffer()->ip.adj_index[VLIB_TX] will be set to the index of the
    *  adjacency for the source address (the remote sender's address)
    */
-  if (PREDICT_TRUE (last_check->src.as_u32 != ip0->src_address.as_u32) ||
+  if (PREDICT_TRUE ((last_check->src.as_u32 != ip0->src_address.as_u32)) ||
+      (last_check->fib_index != vnet_buffer (b)->ip.fib_index) ||
       last_check->first)
     {
       lbi0 = ip4_fib_forwarding_lookup (vnet_buffer (b)->ip.fib_index,
@@ -1587,6 +1590,7 @@
       last_check->lbi = lbi0;
       last_check->error = *error0;
       last_check->first = 0;
+      last_check->fib_index = vnet_buffer (b)->ip.fib_index;
     }
   else
     {
@@ -1621,6 +1625,9 @@
     vnet_buffer (b[1])->sw_if_index[VLIB_TX] :
     vnet_buffer (b[1])->ip.fib_index;
 
+  not_last_hit |= vnet_buffer (b[0])->ip.fib_index ^ last_check->fib_index;
+  not_last_hit |= vnet_buffer (b[1])->ip.fib_index ^ last_check->fib_index;
+
   if (is_receive_dpo)
     {
       const receive_dpo_t *rd0, *rd1;
@@ -1683,6 +1690,7 @@
       last_check->lbi = lbi[1];
       last_check->error = error[1];
       last_check->first = 0;
+      last_check->fib_index = vnet_buffer (b[1])->ip.fib_index;
     }
   else
     {
@@ -1752,10 +1760,11 @@
      * member to make sure the .lbi is initialised for the first
      * packet.
      */
-    .src = {.as_u32 = 0},
+    .src = { .as_u32 = 0 },
     .lbi = ~0,
     .error = IP4_ERROR_UNKNOWN_PROTOCOL,
     .first = 1,
+    .fib_index = 0,
   };
 
   from = vlib_frame_vector_args (frame);