[PATCH 2/3] net: checksum: Add IP header checksum calculation

[Bin Meng <bmeng.cn@gmail.com>]

From: Guishan Qin <guishan.qin@windriver.com>

At present net_checksum_calculate() only calculates TCP/UDP checksum
in an IP packet, but assumes the IP header checksum to be provided
by the software, e.g.: Linux kernel always calculates the IP header
checksum. However this might not always be the case, e.g.: for an IP
checksum offload enabled stack like VxWorks, the IP header chcksum
can be zero.

This adds the checksum calculation of the IP header.

Signed-off-by: Guishan Qin <guishan.qin@windriver.com>
Signed-off-by: Yabing Liu <yabing.liu@windriver.com>
Signed-off-by: Bin Meng <bin.meng@windriver.com>
---

 net/checksum.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/checksum.c b/net/checksum.c
index 5cb8b2c..dabd290 100644
--- a/net/checksum.c
+++ b/net/checksum.c
@@ -61,6 +61,7 @@ void net_checksum_calculate(uint8_t *data, int length)
 {
     int mac_hdr_len, ip_len;
     struct ip_header *ip;
+    uint16_t csum;
 
     /*
      * Note: We cannot assume "data" is aligned, so the all code uses
@@ -106,6 +107,11 @@ void net_checksum_calculate(uint8_t *data, int length)
         return; /* not IPv4 */
     }
 
+    /* Calculate IP checksum */
+    stw_he_p(&ip->ip_sum, 0);
+    csum = net_raw_checksum((uint8_t *)ip, IP_HDR_GET_LEN(ip));
+    stw_be_p(&ip->ip_sum, csum);
+
     if (IP4_IS_FRAGMENT(ip)) {
         return; /* a fragmented IP packet */
     }
@@ -122,7 +128,6 @@ void net_checksum_calculate(uint8_t *data, int length)
     switch (ip->ip_p) {
     case IP_PROTO_TCP:
     {
-        uint16_t csum;
         tcp_header *tcp = (tcp_header *)(ip + 1);
 
         if (ip_len < sizeof(tcp_header)) {
@@ -143,7 +148,6 @@ void net_checksum_calculate(uint8_t *data, int length)
     }
     case IP_PROTO_UDP:
     {
-        uint16_t csum;
         udp_header *udp = (udp_header *)(ip + 1);
 
         if (ip_len < sizeof(udp_header)) {
-- 
2.7.4