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SubjectRe: [PATCH net-next] udp: allow forwarding of plain (non-fraglisted) UDP GRO packets
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On 1/12/21 1:16 PM, Alexander Lobakin wrote:
> Commit 9fd1ff5d2ac7 ("udp: Support UDP fraglist GRO/GSO.") actually
> not only added a support for fraglisted UDP GRO, but also tweaked
> some logics the way that non-fraglisted UDP GRO started to work for
> forwarding too.
> Tests showed that currently forwarding and NATing of plain UDP GRO
> packets are performed fully correctly, regardless if the target
> netdevice has a support for hardware/driver GSO UDP L4 or not.
> Add the last element and allow to form plain UDP GRO packets if
> there is no socket -> we are on forwarding path.
>
> Plain UDP GRO forwarding even shows better performance than fraglisted
> UDP GRO in some cases due to not wasting one skbuff_head per every
> segment.
>
> Signed-off-by: Alexander Lobakin <alobakin@pm.me>
> ---
> net/ipv4/udp_offload.c | 5 +++--
> 1 file changed, 3 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index ff39e94781bf..9d71df3d52ce 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -460,12 +460,13 @@ struct sk_buff *udp_gro_receive(struct list_head *head, struct sk_buff *skb,
> if (skb->dev->features & NETIF_F_GRO_FRAGLIST)
> NAPI_GRO_CB(skb)->is_flist = sk ? !udp_sk(sk)->gro_enabled: 1;
>
> - if ((sk && udp_sk(sk)->gro_enabled) || NAPI_GRO_CB(skb)->is_flist) {
> + if (!sk || (sk && udp_sk(sk)->gro_enabled) ||
> + NAPI_GRO_CB(skb)->is_flist) {
> pp = call_gro_receive(udp_gro_receive_segment, head, skb);
> return pp;
> }
>

The second check for sk in "(sk && udp_sk(sk)->gro_enabled)" is
redundant and can be dropped. You already verified it is present when
you checked for !sk before the logical OR.

> - if (!sk || NAPI_GRO_CB(skb)->encap_mark ||
> + if (NAPI_GRO_CB(skb)->encap_mark ||
> (skb->ip_summed != CHECKSUM_PARTIAL &&
> NAPI_GRO_CB(skb)->csum_cnt == 0 &&
> !NAPI_GRO_CB(skb)->csum_valid) ||
>

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