Output interface MTU check ignored in double-loop

In the double loop of ip4-rewrite, when forwarding packets,
the outbound interface MTU check occurs too late in the
double-loop to be actioned.

Change-Id: Ifc44e65d6ddb832aa0161d0685b1a28378541905
Signed-off-by: Chris Luke <chrisy@flirble.org>

diff --git a/vnet/vnet/ip/ip4_forward.c b/vnet/vnet/ip/ip4_forward.c
index 1de0b40..3075e0c 100644 (file)
--- a/vnet/vnet/ip/ip4_forward.c
+++ b/vnet/vnet/ip/ip4_forward.c
@@ -2641,6 +2641,15 @@ ip4_rewrite_inline (vlib_main_t * vm,
           /* Worth pipelining. No guarantee that adj0,1 are hot... */
          rw_len0 = adj0[0].rewrite_header.data_bytes;
          rw_len1 = adj1[0].rewrite_header.data_bytes;
+
+          /* Check MTU of outgoing interface. */
+          error0 = (vlib_buffer_length_in_chain (vm, p0) > adj0[0].rewrite_header.max_l3_packet_bytes
+                    ? IP4_ERROR_MTU_EXCEEDED
+                    : error0);
+          error1 = (vlib_buffer_length_in_chain (vm, p1) > adj1[0].rewrite_header.max_l3_packet_bytes
+                    ? IP4_ERROR_MTU_EXCEEDED
+                    : error1);
+
          next0 = (error0 == IP4_ERROR_NONE) 
             ? adj0[0].rewrite_header.next_index : 0;
 
@@ -2670,14 +2679,6 @@ ip4_rewrite_inline (vlib_main_t * vm,
                    /* packet increment */ 0,
                    /* byte increment */ rw_len1-sizeof(ethernet_header_t));
 
-         /* Check MTU of outgoing interface. */
-         error0 = (vlib_buffer_length_in_chain (vm, p0) > adj0[0].rewrite_header.max_l3_packet_bytes
-                   ? IP4_ERROR_MTU_EXCEEDED
-                   : error0);
-         error1 = (vlib_buffer_length_in_chain (vm, p1) > adj1[0].rewrite_header.max_l3_packet_bytes
-                   ? IP4_ERROR_MTU_EXCEEDED
-                   : error1);
-
          p0->current_data -= rw_len0;
          p1->current_data -= rw_len1;