ip: fix udp/tcp checksum corner cases

[vpp.git] / src / vnet / ip / ip4_forward.c

diff --git a/src/vnet/ip/ip4_forward.c b/src/vnet/ip/ip4_forward.c
index caf02d1..ecb3595 100644 (file)
--- a/src/vnet/ip/ip4_forward.c
+++ b/src/vnet/ip/ip4_forward.c
@@ -1303,7 +1303,8 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
   u32 ip_header_length, payload_length_host_byte_order;
   u32 n_this_buffer, n_bytes_left, n_ip_bytes_this_buffer;
   u16 sum16;
-  void *data_this_buffer;
+  u8 *data_this_buffer;
+  u8 length_odd;
 
   /* Initialize checksum with ip header. */
   ip_header_length = ip4_header_bytes (ip0);
@@ -1327,7 +1328,7 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
       ip_csum_with_carry (sum0, clib_mem_unaligned (&ip0->src_address, u64));
 
   n_bytes_left = n_this_buffer = payload_length_host_byte_order;
-  data_this_buffer = (void *) ip0 + ip_header_length;
+  data_this_buffer = (u8 *) ip0 + ip_header_length;
   n_ip_bytes_this_buffer =
     p0->current_length - (((u8 *) ip0 - p0->data) - p0->current_data);
   if (n_this_buffer + ip_header_length > n_ip_bytes_this_buffer)
@@ -1335,6 +1336,7 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
       n_this_buffer = n_ip_bytes_this_buffer > ip_header_length ?
        n_ip_bytes_this_buffer - ip_header_length : 0;
     }
+
   while (1)
     {
       sum0 = ip_incremental_checksum (sum0, data_this_buffer, n_this_buffer);
@@ -1346,13 +1348,23 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
       if (!(p0->flags & VLIB_BUFFER_NEXT_PRESENT))
        return 0xfefe;
 
+      length_odd = (n_this_buffer & 1);
+
       p0 = vlib_get_buffer (vm, p0->next_buffer);
       data_this_buffer = vlib_buffer_get_current (p0);
       n_this_buffer = clib_min (p0->current_length, n_bytes_left);
+
+      if (PREDICT_FALSE (length_odd))
+       {
+         /* Prepend a 0 or the resulting checksum will be incorrect. */
+         data_this_buffer--;
+         n_this_buffer++;
+         n_bytes_left++;
+         data_this_buffer[0] = 0;
+       }
     }
 
   sum16 = ~ip_csum_fold (sum0);
-
   return sum16;
 }