[dpdk-dev] [PATCH v2] app/testpmd: compute checksum in icmpecho replies

[Adrien Mazarguil]

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 at 6wind.com>
Acked-by: Ivan Boule <ivan.boule at 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;
        }

-- 
2.1.0