Re: [PATCH 1/2] app/testpmd: revert L4 protocol retrieval from L3 header

[fengchengwen <fengchengwen@huawei.com>]

On 11/5/2025 10:47 AM, Mingjin Ye wrote:
> This reverts commit 496159613ffc7b6ba592432a1ba4d1a38f6935de.
> 
> When the TX IP checksum offload feature is enabled, it may result in
> internal UDP checksum errors in VXLAN tunnel packets.
> 
> Fixes: 496159613ffc ("app/testpmd: fix L4 protocol retrieval from L3 header")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Mingjin Ye <mingjinx.ye@intel.com>
> ---
>  app/test-pmd/csumonly.c | 39 +++++++++++++++++++++++----------------
>  1 file changed, 23 insertions(+), 16 deletions(-)
> 
> diff --git a/app/test-pmd/csumonly.c b/app/test-pmd/csumonly.c
> index a6e872e5a4..d355dbd8c0 100644
> --- a/app/test-pmd/csumonly.c
> +++ b/app/test-pmd/csumonly.c
> @@ -525,8 +525,20 @@ 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;

this function get L4 proto direct from header which can't handle inner IPv6 with option.

> +}
> +
>  static uint8_t
> -parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype, bool parse_inner)
> +parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype)
>  {
>  	int frag = 0, ret;
>  
> @@ -545,19 +557,16 @@ parse_l4_proto(const struct rte_mbuf *m, uint32_t off, uint32_t ptype, bool pars
>  		if (unlikely(ip6h == NULL))
>  			return 0;
>  
> -		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;
> +		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;

this logic has problem: parse_l4_proto was used to prase outer L4 if in tunnel case, but it depend on
whether inner is L3_IPV6_EXT.

> +			return ret;
> +		}
>  
> -		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 ip6h->proto;
>  	}
> -
>  	return 0;
>  }
>  
> @@ -696,7 +705,7 @@ 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, false);
> +		info.l4_proto = parse_l4_proto(m, info.l2_len, ptype);
>  
>  		l3_hdr = (char *)eth_hdr + info.l2_len;
>  		/* check if it's a supported tunnel */
> @@ -714,11 +723,9 @@ pkt_burst_checksum_forward(struct fwd_stream *fs)
>  		}
>  		/* update l3_hdr and outer_l3_hdr if a tunnel was parsed */
>  		if (info.is_tunnel) {
> -			uint16_t l3_off = info.outer_l2_len +  info.outer_l3_len + info.l2_len;
> -
>  			outer_l3_hdr = l3_hdr;
>  			l3_hdr = (char *)l3_hdr + info.outer_l3_len + info.l2_len;
> -			info.l4_proto = parse_l4_proto(m, l3_off, ptype, true);
> +			parse_inner_l4_proto(l3_hdr, &info);
>  		}
>  		/* step 2: depending on user command line configuration,
>  		 * recompute checksum either in software or flag the