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

[Akhil Goyal <akhil.goyal@nxp.com>]

On 1/15/2018 6:12 PM, Akhil Goyal wrote:
> 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@nxp.com>
> ---
This patch is an update to a very old patch which was rejected earlier.
http://dpdk.org/dev/patchwork/patch/16113/

>   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;
>