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)

4 files changed, 97 insertions, 100 deletions

diff --git a/src/vnet/ip/ip.h b/src/vnet/ip/ip.h
index 7a82dcf8f2b..65ccaef40c2 100644
--- a/src/vnet/ip/ip.h
+++ b/src/vnet/ip/ip.h
@@ -195,6 +195,85 @@ ip_incremental_checksum_buffer (vlib_main_t * vm,
   return sum;
 }
 
+always_inline u16
+ip_calculate_l4_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
+			  ip_csum_t sum0, u32 payload_length,
+			  u8 * iph, u32 ip_header_size, u8 * l4h)
+{
+  u16 sum16;
+  u8 *data_this_buffer, length_odd;
+  u32 n_bytes_left, n_this_buffer, n_ip_bytes_this_buffer;
+
+  n_bytes_left = payload_length;
+
+  if (l4h)			/* packet l4 header and no buffer chain involved */
+    {
+      ASSERT (p0 == NULL);
+      n_this_buffer = payload_length;
+      data_this_buffer = l4h;
+    }
+  else
+    {
+      ASSERT (p0);
+      if (iph)			/* ip header pointer set to packet in buffer */
+	{
+	  ASSERT (ip_header_size);
+	  n_this_buffer = payload_length;
+	  data_this_buffer = iph + ip_header_size;	/* at l4 header */
+	  n_ip_bytes_this_buffer =
+	    p0->current_length - (((u8 *) iph - p0->data) - p0->current_data);
+	  if (PREDICT_FALSE (payload_length + ip_header_size >
+			     n_ip_bytes_this_buffer))
+	    {
+	      n_this_buffer = n_ip_bytes_this_buffer - ip_header_size;
+	      if (PREDICT_FALSE (n_this_buffer >> 31))
+		{		/*  error - ip header don't fit this buffer */
+		  ASSERT (0);
+		  return 0xfefe;
+		}
+	    }
+	}
+      else			/* packet in buffer with no ip header  */
+	{			/* buffer current pointer at l4 header */
+	  n_this_buffer = p0->current_length;
+	  data_this_buffer = vlib_buffer_get_current (p0);
+	}
+      n_this_buffer = clib_min (n_this_buffer, n_bytes_left);
+    }
+
+  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;
+
+      if (!(p0->flags & VLIB_BUFFER_NEXT_PRESENT))
+	{
+	  ASSERT (0);		/* error - more buffer expected */
+	  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 byte to maintain 2-byte checksum alignment */
+	  data_this_buffer--;
+	  n_this_buffer++;
+	  n_bytes_left++;
+	  data_this_buffer[0] = 0;
+	}
+    }
+
+  sum16 = ~ip_csum_fold (sum0);
+  return sum16;
+}
+
 void ip_del_all_interface_addresses (vlib_main_t * vm, u32 sw_if_index);
 
 extern vlib_node_registration_t ip4_inacl_node;
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
diff --git a/src/vnet/ip/ip6.h b/src/vnet/ip/ip6.h
index 810fd70ff0c..94c5080a0aa 100644
--- a/src/vnet/ip/ip6.h
+++ b/src/vnet/ip/ip6.h
@@ -683,7 +683,8 @@ vlib_buffer_push_ip6 (vlib_main_t * vm, vlib_buffer_t * b,
 		    sizeof (ip6h->src_address));
   clib_memcpy_fast (ip6h->dst_address.as_u8, dst->as_u8,
 		    sizeof (ip6h->src_address));
-  b->flags |= VNET_BUFFER_F_IS_IP6;
+  vnet_buffer (b)->l3_hdr_offset = (u8 *) ip6h - b->data;
+  b->flags |= VNET_BUFFER_F_IS_IP6 | VNET_BUFFER_F_L3_HDR_OFFSET_VALID;
 
   return ip6h;
 }
diff --git a/src/vnet/ip/ip6_forward.c b/src/vnet/ip/ip6_forward.c
index ea13116d8aa..47fb57ae201 100644
--- a/src/vnet/ip/ip6_forward.c
+++ b/src/vnet/ip/ip6_forward.c
@@ -1011,11 +1011,10 @@ ip6_tcp_udp_icmp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
 				   ip6_header_t * ip0, int *bogus_lengthp)
 {
   ip_csum_t sum0;
-  u16 sum16, payload_length_host_byte_order;
-  u32 i, n_this_buffer, n_bytes_left;
+  u16 payload_length_host_byte_order;
+  u32 i;
   u32 headers_size = sizeof (ip0[0]);
   u8 *data_this_buffer;
-  u8 length_odd;
 
   ASSERT (bogus_lengthp);
   *bogus_lengthp = 0;
@@ -1027,14 +1026,10 @@ ip6_tcp_udp_icmp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
 
   for (i = 0; i < ARRAY_LEN (ip0->src_address.as_uword); i++)
     {
-      sum0 = ip_csum_with_carry (sum0,
-				 clib_mem_unaligned (&ip0->
-						     src_address.as_uword[i],
-						     uword));
-      sum0 =
-	ip_csum_with_carry (sum0,
-			    clib_mem_unaligned (&ip0->dst_address.as_uword[i],
-						uword));
+      sum0 = ip_csum_with_carry
+	(sum0, clib_mem_unaligned (&ip0->src_address.as_uword[i], uword));
+      sum0 = ip_csum_with_carry
+	(sum0, clib_mem_unaligned (&ip0->dst_address.as_uword[i], uword));
     }
 
   /* some icmp packets may come with a "router alert" hop-by-hop extension header (e.g., mldv2 packets)
@@ -1056,52 +1051,14 @@ ip6_tcp_udp_icmp_compute_checksum (vlib_main_t * vm, vlib_buffer_t * p0,
       headers_size += skip_bytes;
     }
 
-  n_bytes_left = n_this_buffer = payload_length_host_byte_order;
-
   if (p0)
-    {
-      u32 n_ip_bytes_this_buffer =
-	p0->current_length - (((u8 *) ip0 - p0->data) - p0->current_data);
-      if (n_this_buffer + headers_size > n_ip_bytes_this_buffer)
-	{
-	  n_this_buffer = p0->current_length > headers_size ?
-	    n_ip_bytes_this_buffer - headers_size : 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))
-	{
-	  *bogus_lengthp = 1;
-	  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, headers_size, NULL);
+  else
+    return ip_calculate_l4_checksum (vm, 0, sum0,
+				     payload_length_host_byte_order, NULL, 0,
+				     data_this_buffer);
 }
 
 u32