netdev - Re: [PATCH nf-next 3/6] netfilter: bridge: move pskb_trim_rcsum out of br_nf_check_hbh

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Date:   Mon, 6 Mar 2023 17:26:58 +0100
From:   Simon Horman <simon.horman@...igine.com>
To:     Xin Long <lucien.xin@...il.com>
Cc:     netfilter-devel@...r.kernel.org,
        network dev <netdev@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...filter.org>,
        Florian Westphal <fw@...len.de>, davem@...emloft.net,
        kuba@...nel.org, Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Pravin B Shelar <pshelar@....org>,
        Aaron Conole <aconole@...hat.com>
Subject: Re: [PATCH nf-next 3/6] netfilter: bridge: move pskb_trim_rcsum out
 of br_nf_check_hbh_len

On Fri, Mar 03, 2023 at 07:12:39PM -0500, Xin Long wrote:
> br_nf_check_hbh_len() is a function to check the Hop-by-hop option
> header, and shouldn't do pskb_trim_rcsum() there. This patch is to
> pass pkt_len out to br_validate_ipv6() and do pskb_trim_rcsum()
> after calling br_validate_ipv6() instead.
> 
> Signed-off-by: Xin Long <lucien.xin@...il.com>

Reviewed-by: Simon Horman <simon.horman@...igine.com>

> ---
>  net/bridge/br_netfilter_ipv6.c | 33 ++++++++++++++-------------------
>  1 file changed, 14 insertions(+), 19 deletions(-)
> 
> diff --git a/net/bridge/br_netfilter_ipv6.c b/net/bridge/br_netfilter_ipv6.c
> index 50f564c33551..07289e4f3213 100644
> --- a/net/bridge/br_netfilter_ipv6.c
> +++ b/net/bridge/br_netfilter_ipv6.c
> @@ -43,11 +43,11 @@
>  /* We only check the length. A bridge shouldn't do any hop-by-hop stuff
>   * anyway
>   */
> -static int br_nf_check_hbh_len(struct sk_buff *skb)
> +static int br_nf_check_hbh_len(struct sk_buff *skb, u32 *plen)
>  {
>  	int len, off = sizeof(struct ipv6hdr);
>  	unsigned char *nh;
> -	u32 pkt_len;
> +	u32 pkt_len = 0;
>  
>  	if (!pskb_may_pull(skb, off + 8))
>  		return -1;
> @@ -83,10 +83,6 @@ static int br_nf_check_hbh_len(struct sk_buff *skb)
>  				return -1;
>  			if (pkt_len > skb->len - sizeof(struct ipv6hdr))
>  				return -1;
> -			if (pskb_trim_rcsum(skb,
> -					    pkt_len + sizeof(struct ipv6hdr)))
> -				return -1;
> -			nh = skb_network_header(skb);

nit: Something you may want to consider if you spin a v2.

     It seems that pkt_len is only set here.
     So *plen could also be set here, simplifying the return path slightly.

     Also, if so, then a not entirely related clean-up would
     be to reduce the scope of pkt_len to this block.

>  		}
>  		off += optlen;
>  		len -= optlen;
> @@ -94,6 +90,8 @@ static int br_nf_check_hbh_len(struct sk_buff *skb)
>  	if (len)
>  		return -1;
>  
> +	if (pkt_len)
> +		*plen = pkt_len;
>  	return 0;
>  }
>  

...