MAP: Decrement TTL of payload IPv4 packet.

[vpp.git] / vnet / vnet / map / ip4_map.c

diff --git a/vnet/vnet/map/ip4_map.c b/vnet/vnet/map/ip4_map.c
index 6ed176c..c8ee276 100644 (file)
--- a/vnet/vnet/map/ip4_map.c
+++ b/vnet/vnet/map/ip4_map.c
@@ -155,6 +155,28 @@ ip4_map_ip6_lookup_bypass (vlib_buffer_t *p0, ip4_header_t *ip)
   return (false);
 }
 
+/*
+ * ip4_map_ttl
+ */
+static inline void
+ip4_map_decrement_ttl (ip4_header_t *ip, u8 *error)
+{
+  i32 ttl = ip->ttl;
+
+  /* Input node should have reject packets with ttl 0. */
+  ASSERT (ip->ttl > 0);
+
+  u32 checksum = ip->checksum + clib_host_to_net_u16(0x0100);
+  checksum += checksum >= 0xffff;
+  ip->checksum = checksum;
+  ttl -= 1;
+  ip->ttl = ttl;
+  *error = ttl <= 0 ? IP4_ERROR_TIME_EXPIRED : *error;
+
+  /* Verify checksum. */
+  ASSERT (ip->checksum == ip4_header_checksum(ip));
+}
+
 /*
  * ip4_map
  */
@@ -345,6 +367,9 @@ ip4_map (vlib_main_t *vm,
        */
       port0 = ip4_map_port_and_security_check(d0, ip40, &next0, &error0);
 
+      /* Decrement IPv4 TTL */
+      ip4_map_decrement_ttl(ip40, &error0);
+
       /* MAP calc */
       u32 da40 = clib_net_to_host_u32(ip40->dst_address.as_u32);
       u16 dp40 = clib_net_to_host_u16(port0);