[dpdk-dev] [PATCH] examples/ipsec-secgw: update incremental checksum

[Akhil Goyal]

When TTL is decremented or ecn is updated in IP header
before forwarding the packet, checksum needs to be updated.

In this patch an incremental checksum is added for ipv4 case.

Signed-off-by: Akhil Goyal <akhil.goyal at nxp.com>
---
 examples/ipsec-secgw/ipip.h | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/examples/ipsec-secgw/ipip.h b/examples/ipsec-secgw/ipip.h
index fb6a6fa..13b8455 100644
--- a/examples/ipsec-secgw/ipip.h
+++ b/examples/ipsec-secgw/ipip.h
@@ -27,6 +27,10 @@ ipip_outbound(struct rte_mbuf *m, uint32_t offset, uint32_t is_ipv6,
 	if (inip4->ip_v == IPVERSION) {
 		/* XXX This should be done by the forwarding engine instead */
 		inip4->ip_ttl -= 1;
+		if (inip4->ip_sum >= rte_cpu_to_be_16(0xffff - 0x100))
+			inip4->ip_sum += rte_cpu_to_be_16(0x100) + 1;
+		else
+			inip4->ip_sum += rte_cpu_to_be_16(0x100);
 		ds_ecn = inip4->ip_tos;
 	} else {
 		inip6 = (struct ip6_hdr *)inip4;
@@ -95,8 +99,17 @@ ip6ip_outbound(struct rte_mbuf *m, uint32_t offset,
 static inline void
 ip4_ecn_setup(struct ip *ip4)
 {
-	if (ip4->ip_tos & IPTOS_ECN_MASK)
+	if (ip4->ip_tos & IPTOS_ECN_MASK) {
+		unsigned long sum;
+		uint8_t old;
+
+		old = ip4->ip_tos;
 		ip4->ip_tos |= IPTOS_ECN_CE;
+		sum = old + (~(*(uint8_t *)&ip4->ip_tos) & 0xff);
+		sum += rte_be_to_cpu_16(ip4->ip_sum);
+		sum = (sum & 0xffff) + (sum >> 16);
+		ip4->ip_sum = rte_cpu_to_be_16(sum + (sum >> 16));
+	}
 }
 
 static inline void
@@ -140,6 +153,10 @@ ipip_inbound(struct rte_mbuf *m, uint32_t offset)
 			ip4_ecn_setup(inip4);
 		/* XXX This should be done by the forwarding engine instead */
 		inip4->ip_ttl -= 1;
+		if (inip4->ip_sum >= rte_cpu_to_be_16(0xffff - 0x100))
+			inip4->ip_sum += rte_cpu_to_be_16(0x100) + 1;
+		else
+			inip4->ip_sum += rte_cpu_to_be_16(0x100);
 		m->packet_type &= ~RTE_PTYPE_L4_MASK;
 		if (inip4->ip_p == IPPROTO_UDP)
 			m->packet_type |= RTE_PTYPE_L4_UDP;
-- 
2.9.3