ping: correct the fib-index used for the reply

Type: fix

if original packet was to the link local, then the
fib index in the buffer is that of the LL table, we can't use that
to foward the response if the new destination
is global, so reset to the fib index of the link.
In other case, the fib index we need has been written
to the buffer already.

Add a test for IPv6 ping in an MPLS-VPN where int inout interface is
not the the same VRF as the response should be sent.

Signed-off-by: Neale Ranns <neale@graphiant.com>
Change-Id: I18a232d90ddd3ef051a52476c5d861c87060e76f

2 files changed, 62 insertions, 29 deletions

diff --git a/src/plugins/ping/ping.c b/src/plugins/ping/ping.c
index 2cc6b771268..050048211e6 100644
--- a/src/plugins/ping/ping.c
+++ b/src/plugins/ping/ping.c
@@ -662,15 +662,20 @@ ip6_icmp_echo_request (vlib_main_t *vm, vlib_node_runtime_t *node,
 	  ip0->hop_limit = im->host_config.ttl;
 	  ip1->hop_limit = im->host_config.ttl;
 
-	  /* Determine the correct lookup fib indices... */
-	  fib_index0 = vec_elt (im->fib_index_by_sw_if_index,
-				vnet_buffer (p0)->sw_if_index[VLIB_RX]);
-	  vnet_buffer (p0)->sw_if_index[VLIB_TX] = fib_index0;
-	  /* Determine the correct lookup fib indices... */
-	  fib_index1 = vec_elt (im->fib_index_by_sw_if_index,
-				vnet_buffer (p1)->sw_if_index[VLIB_RX]);
-	  vnet_buffer (p1)->sw_if_index[VLIB_TX] = fib_index1;
-
+	  if (ip6_address_is_link_local_unicast (&ip0->src_address) &&
+	      !ip6_address_is_link_local_unicast (&ip0->dst_address))
+	    {
+	      fib_index0 = vec_elt (im->fib_index_by_sw_if_index,
+				    vnet_buffer (p0)->sw_if_index[VLIB_RX]);
+	      vnet_buffer (p0)->sw_if_index[VLIB_TX] = fib_index0;
+	    }
+	  if (ip6_address_is_link_local_unicast (&ip1->src_address) &&
+	      !ip6_address_is_link_local_unicast (&ip1->dst_address))
+	    {
+	      fib_index1 = vec_elt (im->fib_index_by_sw_if_index,
+				    vnet_buffer (p1)->sw_if_index[VLIB_RX]);
+	      vnet_buffer (p1)->sw_if_index[VLIB_TX] = fib_index1;
+	    }
 	  p0->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
 	  p1->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
 
@@ -722,12 +727,19 @@ ip6_icmp_echo_request (vlib_main_t *vm, vlib_node_runtime_t *node,
 
 	  ip0->hop_limit = im->host_config.ttl;
 
-	  /* if the packet is link local, we'll bounce through the link-local
-	   * table with the RX interface correctly set */
-	  fib_index0 = vec_elt (im->fib_index_by_sw_if_index,
-				vnet_buffer (p0)->sw_if_index[VLIB_RX]);
-	  vnet_buffer (p0)->sw_if_index[VLIB_TX] = fib_index0;
-
+	  if (ip6_address_is_link_local_unicast (&ip0->src_address) &&
+	      !ip6_address_is_link_local_unicast (&ip0->dst_address))
+	    {
+	      /* if original packet was to the link local, then the
+	       * fib index is that of the LL table, we can't use that
+	       * to foward the response if the new destination
+	       * is global, so reset to the fib index of the link.
+	       * In other case, the fib index we need has been written
+	       * to the buffer already. */
+	      fib_index0 = vec_elt (im->fib_index_by_sw_if_index,
+				    vnet_buffer (p0)->sw_if_index[VLIB_RX]);
+	      vnet_buffer (p0)->sw_if_index[VLIB_TX] = fib_index0;
+	    }
 	  p0->flags |= VNET_BUFFER_F_LOCALLY_ORIGINATED;
 	  /* Verify speculative enqueue, maybe switch current next frame */
 	  vlib_validate_buffer_enqueue_x1 (vm, node, next_index, to_next,
diff --git a/test/test_mpls.py b/test/test_mpls.py
index f7709d10cc1..4cc7a0759f2 100644
--- a/test/test_mpls.py
+++ b/test/test_mpls.py
@@ -18,7 +18,7 @@ import scapy.compat
 from scapy.packet import Raw
 from scapy.layers.l2 import Ether, ARP
 from scapy.layers.inet import IP, UDP, ICMP
-from scapy.layers.inet6 import IPv6, ICMPv6TimeExceeded
+from scapy.layers.inet6 import IPv6, ICMPv6TimeExceeded, ICMPv6EchoRequest
 from scapy.contrib.mpls import MPLS
 
 NUM_PKTS = 67
@@ -196,7 +196,8 @@ class TestMPLS(VppTestCase):
         return pkts
 
     def create_stream_labelled_ip6(self, src_if, mpls_labels,
-                                   hlim=64, dst_ip=None):
+                                   hlim=64, dst_ip=None,
+                                   ping=0, ip_itf=None):
         if dst_ip is None:
             dst_ip = src_if.remote_ip6
         self.reset_packet_infos()
@@ -208,9 +209,14 @@ class TestMPLS(VppTestCase):
             for l in mpls_labels:
                 p = p / MPLS(label=l.value, ttl=l.ttl, cos=l.exp)
 
-            p = p / (IPv6(src=src_if.remote_ip6, dst=dst_ip, hlim=hlim) /
-                     UDP(sport=1234, dport=1234) /
-                     Raw(payload))
+            if ping:
+                p = p / (IPv6(src=ip_itf.remote_ip6,
+                              dst=ip_itf.local_ip6) /
+                         ICMPv6EchoRequest())
+            else:
+                p = p / (IPv6(src=src_if.remote_ip6, dst=dst_ip, hlim=hlim) /
+                         UDP(sport=1234, dport=1234) /
+                         Raw(payload))
             info.data = p.copy()
             pkts.append(p)
         return pkts
@@ -337,7 +343,8 @@ class TestMPLS(VppTestCase):
             raise
 
     def verify_capture_ip6(self, src_if, capture, sent,
-                           ip_hlim=None, ip_dscp=0):
+                           ip_hlim=None, ip_dscp=0,
+                           ping_resp=0):
         try:
             self.assertEqual(len(capture), len(sent))
 
@@ -352,15 +359,18 @@ class TestMPLS(VppTestCase):
                 tx_ip = tx[IPv6]
                 rx_ip = rx[IPv6]
 
-                self.assertEqual(rx_ip.src, tx_ip.src)
-                self.assertEqual(rx_ip.dst, tx_ip.dst)
-                self.assertEqual(rx_ip.tc,  ip_dscp)
-                # IP processing post pop has decremented the TTL
-                if not ip_hlim:
-                    self.assertEqual(rx_ip.hlim + 1, tx_ip.hlim)
+                if not ping_resp:
+                    self.assertEqual(rx_ip.src, tx_ip.src)
+                    self.assertEqual(rx_ip.dst, tx_ip.dst)
+                    self.assertEqual(rx_ip.tc,  ip_dscp)
+                    # IP processing post pop has decremented the TTL
+                    if not ip_hlim:
+                        self.assertEqual(rx_ip.hlim + 1, tx_ip.hlim)
+                    else:
+                        self.assertEqual(rx_ip.hlim, ip_hlim)
                 else:
-                    self.assertEqual(rx_ip.hlim, ip_hlim)
-
+                    self.assertEqual(rx_ip.src, tx_ip.dst)
+                    self.assertEqual(rx_ip.dst, tx_ip.src)
         except:
             raise
 
@@ -1170,6 +1180,13 @@ class TestMPLS(VppTestCase):
                                                   0xffffffff,
                                                   nh_table_id=1)])
         route_35_eos.add_vpp_config()
+        route_356_eos = VppMplsRoute(
+            self, 356, 1,
+            [VppRoutePath("0::0",
+                          0xffffffff,
+                          nh_table_id=1)],
+            eos_proto=FibPathProto.FIB_PATH_NH_PROTO_IP6)
+        route_356_eos.add_vpp_config()
 
         #
         # ping an interface in the non-default table
@@ -1180,6 +1197,10 @@ class TestMPLS(VppTestCase):
             self.pg0, [VppMplsLabel(35)], ping=1, ip_itf=self.pg1)
         rx = self.send_and_expect(self.pg0, tx, self.pg1)
         self.verify_capture_ip4(self.pg1, rx, tx, ping_resp=1)
+        tx = self.create_stream_labelled_ip6(
+            self.pg0, [VppMplsLabel(356)], ping=1, ip_itf=self.pg1)
+        rx = self.send_and_expect(self.pg0, tx, self.pg1)
+        self.verify_capture_ip6(self.pg1, rx, tx, ping_resp=1)
 
         #
         # Double pop