Re: [PATCH v2] app/testpmd: compute checksum in icmpecho replies

[Olivier MATZ <olivier.matz@6wind.com>]

Hi Adrien,

On 05/22/2015 07:03 PM, Adrien Mazarguil wrote:
> ICMP echo replies with invalid checksums may be dropped by network nodes or
> ignored by the ping utility.
> 
> Signed-off-by: Adrien Mazarguil <adrien.mazarguil@6wind.com>
> Acked-by: Ivan Boule <ivan.boule@6wind.com>

Acked-by: Olivier Matz <olivier.matz@6wind.com>



> ---
> 
> v2:
> - Compute correct checksum value by taking overflow into account.
> 
>  app/test-pmd/icmpecho.c | 11 +++++++++--
>  1 file changed, 9 insertions(+), 2 deletions(-)
> 
> diff --git a/app/test-pmd/icmpecho.c b/app/test-pmd/icmpecho.c
> index c5933f4..e249e71 100644
> --- a/app/test-pmd/icmpecho.c
> +++ b/app/test-pmd/icmpecho.c
> @@ -295,6 +295,7 @@ reply_to_icmp_echo_rqsts(struct fwd_stream *fs)
>  	uint16_t vlan_id;
>  	uint16_t arp_op;
>  	uint16_t arp_pro;
> +	uint32_t cksum;
>  	uint8_t  i;
>  	int l2_len;
>  #ifdef RTE_TEST_PMD_RECORD_CORE_CYCLES
> @@ -445,7 +446,8 @@ reply_to_icmp_echo_rqsts(struct fwd_stream *fs)
>  		 * - switch IPv4 source and destinations addresses,
>  		 * - set IP_ICMP_ECHO_REPLY in ICMP header.
>  		 * No need to re-compute the IP header checksum.
> -		 * Reset ICMP checksum.
> +		 * ICMP checksum is computed by assuming it is valid in the
> +		 * echo request and not verified.
>  		 */
>  		ether_addr_copy(&eth_h->s_addr, &eth_addr);
>  		ether_addr_copy(&eth_h->d_addr, &eth_h->s_addr);
> @@ -454,7 +456,12 @@ reply_to_icmp_echo_rqsts(struct fwd_stream *fs)
>  		ip_h->src_addr = ip_h->dst_addr;
>  		ip_h->dst_addr = ip_addr;
>  		icmp_h->icmp_type = IP_ICMP_ECHO_REPLY;
> -		icmp_h->icmp_cksum = 0;
> +		cksum = ~icmp_h->icmp_cksum & 0xffff;
> +		cksum += ~htons(IP_ICMP_ECHO_REQUEST << 8) & 0xffff;
> +		cksum += htons(IP_ICMP_ECHO_REPLY << 8);
> +		cksum = (cksum & 0xffff) + (cksum >> 16);
> +		cksum = (cksum & 0xffff) + (cksum >> 16);
> +		icmp_h->icmp_cksum = ~cksum;
>  		pkts_burst[nb_replies++] = pkt;
>  	}
>  
>