Subject: Re: [PATCH nf-next 5/6] netfilter: use nf_ip6_check_hbh_len in nf_ct_skb_network_trim

From: Simon Horman <[email-masked]>
Date: Mon, 6 Mar 2023 17:35:11 +0100

On Fri, Mar 03, 2023 at 07:12:41PM -0500, Xin Long wrote:
> For IPv6 Jumbo packets, the ipv6_hdr(skb)->payload_len is always 0,
> and its real payload_len ( > 65535) is saved in hbh exthdr. With 0
> length for the jumbo packets, all data and exthdr will be trimmed
> in nf_ct_skb_network_trim().
> 
> This patch is to call nf_ip6_check_hbh_len() to get real pkt_len
> of the IPv6 packet, similar to br_validate_ipv6().
> 
> Signed-off-by: Xin Long <[email-masked]>

Reviewed-by: Simon Horman <[email-masked]>

...

> diff --git a/net/netfilter/nf_conntrack_ovs.c b/net/netfilter/nf_conntrack_ovs.c
> index 52b776bdf526..2016a3b05f86 100644
> --- a/net/netfilter/nf_conntrack_ovs.c
> +++ b/net/netfilter/nf_conntrack_ovs.c

...

> @@ -114,14 +115,20 @@ EXPORT_SYMBOL_GPL(nf_ct_add_helper);
>  int nf_ct_skb_network_trim(struct sk_buff *skb, int family)
>  {
>  	unsigned int len;
> +	int err;
>  
>  	switch (family) {
>  	case NFPROTO_IPV4:
>  		len = skb_ip_totlen(skb);
>  		break;
>  	case NFPROTO_IPV6:
> -		len = sizeof(struct ipv6hdr)
> -			+ ntohs(ipv6_hdr(skb)->payload_len);
> +		len = ntohs(ipv6_hdr(skb)->payload_len);
> +		if (ipv6_hdr(skb)->nexthdr == NEXTHDR_HOP) {

nit: if you spin a v2,
     you may consider reducing the scope of err to this block.

> +			err = nf_ip6_check_hbh_len(skb, &len);
> +			if (err)
> +				return err;
> +		}
> +		len += sizeof(struct ipv6hdr);
>  		break;
>  	default:
>  		len = skb->len;
> -- 
> 2.39.1
>