IP-local: any IP can appear as the source (VPP-1522)

Change-Id: Ib0d9b533d72c899b77c9a7bd1daa9b4a55b7221c
Signed-off-by: Neale Ranns <nranns@cisco.com>

2 files changed, 34 insertions, 3 deletions

diff --git a/src/vnet/ip/ip4_forward.c b/src/vnet/ip/ip4_forward.c
index 1911f088008..1ca4f9309e6 100644
--- a/src/vnet/ip/ip4_forward.c
+++ b/src/vnet/ip/ip4_forward.c
@@ -1334,6 +1334,7 @@ typedef struct
   ip4_address_t src;
   u32 lbi;
   u8 error;
+  u8 first;
 } ip4_local_last_check_t;
 
 static inline void
@@ -1350,7 +1351,8 @@ ip4_local_check_src (vlib_buffer_t * b, ip4_header_t * ip0,
     vnet_buffer (b)->sw_if_index[VLIB_TX] != ~0 ?
     vnet_buffer (b)->sw_if_index[VLIB_TX] : vnet_buffer (b)->ip.fib_index;
 
-  if (PREDICT_FALSE (last_check->src.as_u32 != ip0->src_address.as_u32))
+  if (PREDICT_FALSE (last_check->first ||
+		     (last_check->src.as_u32 != ip0->src_address.as_u32)))
     {
       mtrie0 = &ip4_fib_get (vnet_buffer (b)->ip.fib_index)->mtrie;
       leaf0 = ip4_fib_mtrie_lookup_step_one (mtrie0, &ip0->src_address);
@@ -1392,6 +1394,7 @@ ip4_local_check_src (vlib_buffer_t * b, ip4_header_t * ip0,
       vnet_buffer (b)->ip.adj_index[VLIB_TX] = last_check->lbi;
       vnet_buffer (b)->ip.adj_index[VLIB_RX] = last_check->lbi;
       *error0 = last_check->error;
+      last_check->first = 0;
     }
 }
 
@@ -1403,9 +1406,10 @@ ip4_local_check_src_x2 (vlib_buffer_t ** b, ip4_header_t ** ip,
   ip4_fib_mtrie_t *mtrie[2];
   const dpo_id_t *dpo[2];
   load_balance_t *lb[2];
-  u32 not_last_hit = 0;
+  u32 not_last_hit;
   u32 lbi[2];
 
+  not_last_hit = last_check->first;
   not_last_hit |= ip[0]->src_address.as_u32 ^ last_check->src.as_u32;
   not_last_hit |= ip[1]->src_address.as_u32 ^ last_check->src.as_u32;
 
@@ -1482,6 +1486,7 @@ ip4_local_check_src_x2 (vlib_buffer_t ** b, ip4_header_t ** ip,
 
       error[0] = last_check->error;
       error[1] = last_check->error;
+      last_check->first = 0;
     }
 }
 
@@ -1532,9 +1537,16 @@ ip4_local_inline (vlib_main_t * vm,
   u8 error[2], pt[2];
 
   ip4_local_last_check_t last_check = {
+    /*
+     * 0.0.0.0 can appear as the source address of an IP packet,
+     * as can any other address, hence the need to use the 'first'
+     * member to make sure the .lbi is initialised for the first
+     * packet.
+     */
     .src = {.as_u32 = 0},
     .lbi = ~0,
-    .error = IP4_ERROR_UNKNOWN_PROTOCOL
+    .error = IP4_ERROR_UNKNOWN_PROTOCOL,
+    .first = 1,
   };
 
   from = vlib_frame_vector_args (frame);
diff --git a/test/test_ip4.py b/test/test_ip4.py
index c13024115e0..54090445dac 100644
--- a/test/test_ip4.py
+++ b/test/test_ip4.py
@@ -1470,6 +1470,25 @@ class TestIPInput(VppTestCase):
         # Reset MTU for subsequent tests
         self.vapi.sw_interface_set_mtu(self.pg1.sw_if_index, [9000, 0, 0, 0])
 
+        #
+        # source address 0.0.0.0 and 25.255.255.255 and for-us
+        #
+        p_s0 = (Ether(src=self.pg0.remote_mac,
+                      dst=self.pg0.local_mac) /
+                IP(src="0.0.0.0",
+                   dst=self.pg0.local_ip4) /
+                ICMP(id=4, seq=4) /
+                Raw(load='\x0a' * 18))
+        rx = self.send_and_assert_no_replies(self.pg0, p_s0 * 17)
+
+        p_s0 = (Ether(src=self.pg0.remote_mac,
+                      dst=self.pg0.local_mac) /
+                IP(src="255.255.255.255",
+                   dst=self.pg0.local_ip4) /
+                ICMP(id=4, seq=4) /
+                Raw(load='\x0a' * 18))
+        rx = self.send_and_assert_no_replies(self.pg0, p_s0 * 17)
+
 
 class TestIPDirectedBroadcast(VppTestCase):
     """ IPv4 Directed Broadcast """