[PATCH v1] gro: bug fix in identifying 0 length tcp packets

[kumaraparameshwaran rathinavel]

Hi Jiayu,
Can you please  suggest if the patch can be used ? When timestamps are
disabled we would unnecessarily indulge pure TCP ack packets in the GRO
layer. Or can we have a fix where if the TCP timestamp option is not
present in the packet, do not process the packet, return immediately ?

Thanks,
Param

On Mon, Apr 25, 2022 at 11:36 PM kumaraparameshwaran rathinavel <
kumaraparamesh92 at gmail.com> wrote:

> Hi,
>
> I would like you to review this patch and let me know what you think of
> it.
>
> Thanks,
> Kumara.
>
> ---------- Forwarded message ---------
> From: Kumara Parameshwaran <kumaraparamesh92 at gmail.com>
> Date: Sun, Apr 3, 2022 at 5:20 PM
> Subject: [PATCH v1] gro: bug fix in identifying 0 length tcp packets
> To: <jiayu.hu at intel.com>
> Cc: <dev at dpdk.org>, Kumara Parameshwaran <kumaraparamesh92 at gmail.com>, <
> stable at dpdk.org>, Kumara Parameshwaran <kparameshwar at vmware.com>
>
>
> As the minimum Ethernet frame size is 64 bytes, a 0 length
> tcp payload without tcp options would be 54 bytes and hence
> there would be padding. So it would be incorrect to use the
> packet length to determine the tcp data length.
>
> Fixes: 1e4cf4d6d4fb ("gro: cleanup")
> Cc: stable at dpdk.org
>
> Signed-off-by: Kumara Parameshwaran <kparameshwar at vmware.com>
> ---
> v1:
>         Do not use packet length to determine the tcp data length as
>         the packet length could have padded bytes. This would lead
>         to addition of 0 length tcp packets into the GRO layer when
>         there ethernet fram is padded.
>  lib/gro/gro_tcp4.c | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/lib/gro/gro_tcp4.c b/lib/gro/gro_tcp4.c
> index 7498c66..45e3f48 100644
> --- a/lib/gro/gro_tcp4.c
> +++ b/lib/gro/gro_tcp4.c
> @@ -198,7 +198,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>         struct rte_tcp_hdr *tcp_hdr;
>         uint32_t sent_seq;
>         int32_t tcp_dl;
> -       uint16_t ip_id, hdr_len, frag_off;
> +       uint16_t ip_id, frag_off;
>         uint8_t is_atomic;
>
>         struct tcp4_flow_key key;
> @@ -217,7 +217,6 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>         eth_hdr = rte_pktmbuf_mtod(pkt, struct rte_ether_hdr *);
>         ipv4_hdr = (struct rte_ipv4_hdr *)((char *)eth_hdr + pkt->l2_len);
>         tcp_hdr = (struct rte_tcp_hdr *)((char *)ipv4_hdr + pkt->l3_len);
> -       hdr_len = pkt->l2_len + pkt->l3_len + pkt->l4_len;
>
>         /*
>          * Don't process the packet which has FIN, SYN, RST, PSH, URG, ECE
> @@ -229,7 +228,7 @@ gro_tcp4_reassemble(struct rte_mbuf *pkt,
>          * Don't process the packet whose payload length is less than or
>          * equal to 0.
>          */
> -       tcp_dl = pkt->pkt_len - hdr_len;
> +       tcp_dl = rte_be_to_cpu_16(ipv4_hdr->total_length) - (pkt->l3_len +
> pkt->l4_len);
>         if (tcp_dl <= 0)
>                 return -1;
>
> --
> 2.7.4
>
>
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