fib: Always honour flow hash flag

Type: fix

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: Id7b27edf3712aaa3c277e752b9ca78bb91d184a1

2 files changed, 18 insertions, 1 deletions

diff --git a/src/vnet/adj/.clang-format b/src/vnet/adj/.clang-format
new file mode 100644
index 00000000000..9d159247d51
--- /dev/null
+++ b/src/vnet/adj/.clang-format
@@ -0,0 +1,2 @@
+DisableFormat: true
+SortIncludes: false
diff --git a/src/vnet/adj/adj_midchain.c b/src/vnet/adj/adj_midchain.c
index 93cfb550e3e..a21cd21ea25 100644
--- a/src/vnet/adj/adj_midchain.c
+++ b/src/vnet/adj/adj_midchain.c
@@ -623,8 +623,23 @@ adj_nbr_midchain_stack_on_fib_entry (adj_index_t ai,
                 choice = load_balance_get_bucket_i (lb, hash & lb->lb_n_buckets_minus_1);
                 dpo_copy (&tmp, choice);
             }
-            else if (adj->ia_flags & ADJ_FLAG_MIDCHAIN_FIXUP_FLOW_HASH)
+            else if (lb->lb_n_buckets > 1)
             {
+                /*
+                 * the client has chosen not to use the stacking to select a
+                 * bucket, and there are more than one buckets. there's no
+                 * value in using the midchain's fixed rewrite string to select
+                 * the path, so force a flow hash on the inner.
+                 */
+                adj->rewrite_header.flags |= VNET_REWRITE_FIXUP_FLOW_HASH;
+            }
+
+            if (adj->ia_flags & ADJ_FLAG_MIDCHAIN_FIXUP_FLOW_HASH)
+            {
+                /*
+                 * The client, for reasons unbeknownst to adj, wants to force
+                 * a flow hash on the inner, we will oblige.
+                 */
                 adj->rewrite_header.flags |= VNET_REWRITE_FIXUP_FLOW_HASH;
             }
         }