Re: [PATCH net] net: fix segmentation after TCP/UDP fraglist GRO

[Richard Gobert]

Felix Fietkau wrote:
> Since "net: gro: use cb instead of skb->network_header", the skb network
> header is no longer set in the GRO path.
> This breaks fraglist segmentation, which relies on ip_hdr()/tcp_hdr()
> to check for address/port changes.
> Fix this regression by selectively setting the network header for merged
> segment skbs.
> 
> Fixes: 186b1ea73ad8 ("net: gro: use cb instead of skb->network_header")
> Signed-off-by: Felix Fietkau <nbd@xxxxxxxx>
> ---
>  net/ipv4/tcp_offload.c | 1 +
>  net/ipv4/udp_offload.c | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index d293087b426d..be5c2294610e 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -359,6 +359,7 @@ struct sk_buff *tcp_gro_receive(struct list_head *head, struct sk_buff *skb,
>  		flush |= skb->ip_summed != p->ip_summed;
>  		flush |= skb->csum_level != p->csum_level;
>  		flush |= NAPI_GRO_CB(p)->count >= 64;
> +		skb_set_network_header(skb, skb_gro_receive_network_offset(skb));
>  
>  		if (flush || skb_gro_receive_list(p, skb))
>  			mss = 1;
> diff --git a/net/ipv4/udp_offload.c b/net/ipv4/udp_offload.c
> index 85b5aa82d7d7..e0a6bfa95118 100644
> --- a/net/ipv4/udp_offload.c
> +++ b/net/ipv4/udp_offload.c
> @@ -767,6 +767,7 @@ static struct sk_buff *udp_gro_receive_segment(struct list_head *head,
>  					NAPI_GRO_CB(skb)->flush = 1;
>  					return NULL;
>  				}
> +				skb_set_network_header(skb, skb_gro_receive_network_offset(skb));
>  				ret = skb_gro_receive_list(p, skb);
>  			} else {
>  				skb_gro_postpull_rcsum(skb, uh,

Isn't it better to set the network header in skb_gro_receive_list instead?

Other than that, LGTM.