Re: [PATCH] app/testpmd: fix L4 protocol retrieval from L3 header

[Stephen Hemminger <stephen@networkplumber.org>]

On Sat, 30 Aug 2025 09:29:13 +0800
Dengdui Huang <huangdengdui@huawei.com> wrote:

> Currently, when retrieving the L4 protocol from the L3 header,
> the case of IPv6 with extension headers is not handled correctly.
> This patch fixes it.
> 
> Fixes: 76730c7b9b5a ("app/testpmd: use packet type parsing API")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Dengdui Huang <huangdengdui@huawei.com>
> ---
>  app/test-pmd/csumonly.c | 39 ++++++++++++++++-----------------------
>  1 file changed, 16 insertions(+), 23 deletions(-)
> 
> diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
> index d355dbd8c0..a6e872e5a4 100644
> --- a/app/test-pmd/csumonly.c
> +++ b/app/test-pmd/csumonly.c
> @@ -525,20 +525,8 @@ get_tunnel_ol_flags_by_ptype(uint32_t ptype)
>  	}
>  }
>  
> -static void
> -parse_inner_l4_proto(void *outer_l3_hdr,
> -			struct testpmd_offload_info *info)
> -{
> -	struct rte_ipv4_hdr *ipv4_hdr = outer_l3_hdr;
> -	struct rte_ipv6_hdr *ipv6_hdr = outer_l3_hdr;
> -	if (info->ethertype == _htons(RTE_ETHER_TYPE_IPV4))
> -		info->l4_proto = ipv4_hdr->next_proto_id;
> -	else
> -		info->l4_proto = ipv6_hdr->proto;
> -}
> -
>  static uint8_t
> -parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype)
> +parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype, bool parse_inner)
>  {
>  	int frag = 0, ret;
>  
> @@ -557,16 +545,19 @@ parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype)
>  		if (unlikely(ip6h == NULL))
>  			return 0;
>  
> -		if ((ptype & RTE_PTYPE_INNER_L3_MASK) ==
> -				RTE_PTYPE_INNER_L3_IPV6_EXT) {
> -			ret = rte_net_skip_ip6_ext(ip6h->proto, m, &off, &frag);
> -			if (ret < 0)
> -				return 0;
> -			return ret;
> -		}
> +		if (!parse_inner && (ptype & RTE_PTYPE_L3_MASK) != RTE_PTYPE_L3_IPV6_EXT)
> +			return ip6h->proto;
> +
> +		if (parse_inner && (ptype & RTE_PTYPE_INNER_L3_MASK) != RTE_PTYPE_INNER_L3_IPV6_EXT)
> +			return ip6h->proto;
>  
> -		return ip6h->proto;
> +		off += sizeof(struct rte_ipv6_hdr);
> +		ret = rte_net_skip_ip6_ext(ip6h->proto, m, &off, &frag);
> +		if (ret < 0)
> +			return 0;
> +		return ret;
>  	}
> +
>  	return 0;
>  }
>  
> @@ -705,7 +696,7 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
>  		info.l4_len = hdr_lens.l4_len;
>  		info.ethertype = get_ethertype_by_ptype(eth_hdr,
>  					ptype & RTE_PTYPE_L3_MASK);
> -		info.l4_proto = parse_l4_proto(m, info.l2_len, ptype);
> +		info.l4_proto = parse_l4_proto(m, info.l2_len, ptype, false);


Setting parse_inner to false would cause l4_proto to be set to the extension
header type (rather than the real L4 protocol). Was this change intentional?
Looks like it would cause checksum to be computed incorrectly for simple
case of IPV6 with extension header and TCP.