[dpdk-dev] [PATCH] net/tap: Allow all-zero checksum for UDP over IPv4
Ferruh Yigit
ferruh.yigit at intel.com
Tue Nov 10 16:59:29 CET 2020
On 11/9/2020 2:22 PM, Michael Pfeiffer wrote:
> Unlike TCP, UDP checksums are optional and may be zero to indicate "not
> set" [RFC 768] (except for IPv6, where this prohibited [RFC 8200]). Add
> this special case to the checksum offload emulation in net/tap.
>
> Signed-off-by: Michael Pfeiffer <michael.pfeiffer at tu-ilmenau.de>
> ---
> drivers/net/tap/rte_eth_tap.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/net/tap/rte_eth_tap.c b/drivers/net/tap/rte_eth_tap.c
> index 2f8abb12c..e486b41c5 100644
> --- a/drivers/net/tap/rte_eth_tap.c
> +++ b/drivers/net/tap/rte_eth_tap.c
> @@ -303,6 +303,7 @@ tap_verify_csum(struct rte_mbuf *mbuf)
> uint16_t cksum = 0;
> void *l3_hdr;
> void *l4_hdr;
> + struct rte_udp_hdr *udp_hdr;
>
> if (l2 == RTE_PTYPE_L2_ETHER_VLAN)
> l2_len += 4;
> @@ -349,10 +350,18 @@ tap_verify_csum(struct rte_mbuf *mbuf)
> /* Don't verify checksum for multi-segment packets. */
> if (mbuf->nb_segs > 1)
> return;
> - if (l3 == RTE_PTYPE_L3_IPV4)
> + if (l3 == RTE_PTYPE_L3_IPV4) {
> + if (l4 == RTE_PTYPE_L4_UDP) {
> + udp_hdr = (struct rte_udp_hdr *)l4_hdr;
> + if (udp_hdr->dgram_cksum == 0) {
Overall patch looks good to me, but can you please add a comment on top of above
check to describe why checksum can be zero, as done in the commit log.
> + mbuf->ol_flags |= PKT_RX_L4_CKSUM_NONE;
> + return;
> + }
> + }
> cksum = ~rte_ipv4_udptcp_cksum(l3_hdr, l4_hdr);
> - else if (l3 == RTE_PTYPE_L3_IPV6)
> + } else if (l3 == RTE_PTYPE_L3_IPV6) {
> cksum = ~rte_ipv6_udptcp_cksum(l3_hdr, l4_hdr);
> + }
> mbuf->ol_flags |= cksum ?
> PKT_RX_L4_CKSUM_BAD :
> PKT_RX_L4_CKSUM_GOOD;
>
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