Improve the error reporting for a IP multicast RPF miss.

now we get:

00:00:04:288925: pg-input
 ...
00:00:04:289345: ethernet-input
 ...
00:00:04:289524: ip6-input
 ...
00:00:04:289553: ip6-mfib-forward-lookup
 ...
00:00:04:289584: ip6-mfib-forward-rpf
  entry 14 itf 2 flags Forward,
00:00:04:289754: ip6-drop
    UDP: 2002::1 -> ff01:2::255
      tos 0x00, flow label 0x0, hop limit 64, payload length 21
    UDP: 1234 -> 1234
      length 21, checksum 0x90d1
00:00:04:289802: error-drop
  ip4-input: Multicast RPF check failed

08:36:44,517    Count                    Node                  Reason
       182                ip4-input               Multicast RPF check failed
         8             ip6-icmp-input             neighbor advertisements sent
         8             ip6-icmp-input             router advertisements sent
         8                arp-input               ARP replies sent

Change-Id: I1b29cda4ec77a88db45bfb25c7473cd64bbf501a
Signed-off-by: Neale Ranns <nranns@cisco.com>

3 files changed, 25 insertions, 3 deletions

diff --git a/src/vnet/ip/ip4_error.h b/src/vnet/ip/ip4_error.h
index d9b56bc2f49..4e545aeda3c 100644
--- a/src/vnet/ip/ip4_error.h
+++ b/src/vnet/ip/ip4_error.h
@@ -75,7 +75,10 @@
                                                                         \
   /* Errors singalled by ip4-inacl */                                   \
   _ (INACL_TABLE_MISS, "input ACL table-miss drops")                    \
-  _ (INACL_SESSION_DENY, "input ACL session deny drops")
+  _ (INACL_SESSION_DENY, "input ACL session deny drops")                \
+                                                                        \
+  /* Erros from mfib-forward */                                         \
+  _ (RPF_FAILURE, "Multicast RPF check failed")
 
 typedef enum
 {
diff --git a/src/vnet/mfib/mfib_forward.c b/src/vnet/mfib/mfib_forward.c
index 3d8f4f98cb0..3d0e0d47996 100644
--- a/src/vnet/mfib/mfib_forward.c
+++ b/src/vnet/mfib/mfib_forward.c
@@ -252,8 +252,8 @@ format_mfib_forward_rpf_trace (u8 * s, va_list * args)
     mfib_forward_rpf_trace_t * t = va_arg (*args, mfib_forward_rpf_trace_t *);
 
     s = format (s, "entry %d", t->entry_index);
-    s = format (s, " %d", t->sw_if_index);
-    s = format (s, " %U", format_mfib_itf_flags, t->itf_flags);
+    s = format (s, " itf %d", t->sw_if_index);
+    s = format (s, " flags %U", format_mfib_itf_flags, t->itf_flags);
 
     return s;
 }
@@ -342,7 +342,12 @@ mfib_forward_rpf (vlib_main_t * vm,
 {
     u32 n_left_from, n_left_to_next, * from, * to_next;
     mfib_forward_rpf_next_t next;
+    vlib_node_runtime_t *error_node;
 
+    if (is_v4)
+        error_node = vlib_node_get_runtime (vm, ip4_input_node.index);
+    else
+        error_node = vlib_node_get_runtime (vm, ip6_input_node.index);
     from = vlib_frame_vector_args (frame);
     n_left_from = frame->n_vectors;
     next = MFIB_FORWARD_RPF_NEXT_DROP;
@@ -361,6 +366,7 @@ mfib_forward_rpf (vlib_main_t * vm,
             u32 pi0, next0;
             mfib_itf_flags_t iflags0;
             mfib_entry_flags_t eflags0;
+            u8 error0;
 
             pi0 = from[0];
             to_next[0] = pi0;
@@ -369,6 +375,7 @@ mfib_forward_rpf (vlib_main_t * vm,
             n_left_to_next -= 1;
             n_left_from -= 1;
 
+            error0 = IP4_ERROR_NONE;
             b0 = vlib_get_buffer (vm, pi0);
             mfei0 = vnet_buffer (b0)->ip.adj_index[VLIB_TX];
             mfe0 = mfib_entry_get(mfei0);
@@ -444,8 +451,11 @@ mfib_forward_rpf (vlib_main_t * vm,
             else
             {
                 next0 = MFIB_FORWARD_RPF_NEXT_DROP;
+                error0 = IP4_ERROR_RPF_FAILURE;
             }
 
+            b0->error = error0 ? error_node->errors[error0] : 0;
+
             if (b0->flags & VLIB_BUFFER_IS_TRACED)
             {
                 mfib_forward_rpf_trace_t *t0;
diff --git a/test/test_ip_mcast.py b/test/test_ip_mcast.py
index f3d23a612db..b4554c67f42 100644
--- a/test/test_ip_mcast.py
+++ b/test/test_ip_mcast.py
@@ -406,6 +406,15 @@ class TestIPMcast(VppTestCase):
 
         #
         # a stream that matches the route for (*, ff01::/16)
+        # sent on the non-accepting interface
+        #
+        self.vapi.cli("clear trace")
+        tx = self.create_stream_ip6(self.pg1, "2002::1", "ff01:2::255")
+        self.send_and_assert_no_replies(self.pg1, tx, "RPF miss")
+
+        #
+        # a stream that matches the route for (*, ff01::/16)
+        # sent on the accepting interface
         #
         self.vapi.cli("clear trace")
         tx = self.create_stream_ip6(self.pg0, "2002::1", "ff01:2::255")