ip: improve ip4_header_checksum_is_valid

It is cheaper to include checksum field in calculation and simply
compare result with zero.

Type: improvement

Change-Id: I6f77632c0a4d2f2c632d044d3a5d2fcf2b5bac62
Signed-off-by: Damjan Marion <damarion@cisco.com>

diff --git a/src/vnet/ip/ip4_packet.h b/src/vnet/ip/ip4_packet.h
index 6abb6a9..0653092 100644 (file)
--- a/src/vnet/ip/ip4_packet.h
+++ b/src/vnet/ip/ip4_packet.h
@@ -205,8 +205,8 @@ ip4_next_header (ip4_header_t * i)
 WARN_OFF(array-bounds)
 /* *INDENT-ON* */
 
-always_inline u16
-ip4_header_checksum (ip4_header_t * i)
+static_always_inline u16
+ip4_header_checksum_inline (ip4_header_t * i, int with_checksum)
 {
   int option_len = (i->ip_version_and_header_length & 0xf) - 5;
   uword sum = 0;
@@ -215,7 +215,7 @@ ip4_header_checksum (ip4_header_t * i)
 
   sum += iphdr[0];
   sum += iphdr[1];
-  sum += *(u16 *) (iphdr + 2);
+  sum += with_checksum ? iphdr[2] : *(u16 *) (iphdr + 2);
   /* skip checksum */
   sum += iphdr[3];
   sum += iphdr[4];
@@ -256,7 +256,8 @@ ip4_header_checksum (ip4_header_t * i)
   sum += iphdr[2];
   sum += iphdr[3];
   sum += iphdr[4];
-  /* skip checksum */
+  if (with_checksum)
+    sum += iphdr[5];
   sum += iphdr[6];
   sum += iphdr[7];
   sum += iphdr[8];
@@ -309,6 +310,12 @@ ip4_header_checksum (ip4_header_t * i)
 WARN_ON(array-bounds)
 /* *INDENT-ON* */
 
+always_inline u16
+ip4_header_checksum (ip4_header_t * i)
+{
+  return ip4_header_checksum_inline (i, /* with_checksum */ 0);
+}
+
 always_inline void
 ip4_header_set_dscp (ip4_header_t * ip4, ip_dscp_t dscp)
 {
@@ -376,7 +383,7 @@ ip4_header_get_df (const ip4_header_t * ip4)
 static inline uword
 ip4_header_checksum_is_valid (ip4_header_t * i)
 {
-  return i->checksum == ip4_header_checksum (i);
+  return ip4_header_checksum_inline (i, /* with_checksum */ 1) == 0;
 }
 
 #define ip4_partial_header_checksum_x1(ip0,sum0)                       \