tcp: custom checksum calculations for Ipv4/Ipv6

Type: feature

Based on the configuration, we can disable checksum offload capability
and calculate checksum while pushing the TCP & IP header.
This saves some cycles when VPP stack is used in legacy hardware devices.

Signed-off-by: Srikanth A <srakula@cisco.com>
Change-Id: Ic1b3fcf3040917e47ee65263694ebf7437ac5668
(cherry picked from commit 3642782a2748503f5b5ccf89d1575c1d489948ef)

1 files changed, 3 insertions, 43 deletions

diff --git a/src/vnet/ip/ip4_forward.c b/src/vnet/ip/ip4_forward.c
index d4717c6db4b..40c396c4f3b 100644
--- a/src/vnet/ip/ip4_forward.c
+++ b/src/vnet/ip/ip4_forward.c
@@ -1303,10 +1303,6 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
 {
   ip_csum_t sum0;
   u32 ip_header_length, payload_length_host_byte_order;
-  u32 n_this_buffer, n_bytes_left, n_ip_bytes_this_buffer;
-  u16 sum16;
-  u8 *data_this_buffer;
-  u8 length_odd;
 
   /* Initialize checksum with ip header. */
   ip_header_length = ip4_header_bytes (ip0);
@@ -1329,45 +1325,9 @@ ip4_tcp_udp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
     sum0 =
       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 = (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)
-    {
-      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);
-      n_bytes_left -= n_this_buffer;
-      if (n_bytes_left == 0)
-	break;
-
-      ASSERT (p0->flags & VLIB_BUFFER_NEXT_PRESENT);
-      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;
+  return ip_calculate_l4_checksum (vm, p0, sum0,
+				   payload_length_host_byte_order, (u8 *) ip0,
+				   ip_header_length, NULL);
 }
 
 u32