netdev - Re: [PATCH net-next 2/3] net: ipv4: simplify drop reason handling in ip_rcv_finish

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Message-ID: <4aa939a8-256e-4045-bb4a-01a380a1c519@kernel.org>
Date: Mon, 15 Sep 2025 09:49:38 -0600
From: David Ahern <dsahern@...nel.org>
To: Antoine Tenart <atenart@...nel.org>, davem@...emloft.net,
 kuba@...nel.org, pabeni@...hat.com, edumazet@...gle.com
Cc: netdev@...r.kernel.org
Subject: Re: [PATCH net-next 2/3] net: ipv4: simplify drop reason handling in
 ip_rcv_finish_core

On 9/15/25 3:19 AM, Antoine Tenart wrote:
> diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
> index 8878e865ddf6..93b8286e526a 100644
> --- a/net/ipv4/ip_input.c
> +++ b/net/ipv4/ip_input.c
> @@ -335,7 +335,6 @@ static int ip_rcv_finish_core(struct net *net,
>  			goto drop_error;
>  	}
>  
> -	drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;

since you are touching this function for drop reason cleanups,
drop_reason should be changed from `int` to `enum skb_drop_reason`

>  	if (READ_ONCE(net->ipv4.sysctl_ip_early_demux) &&
>  	    !skb_dst(skb) &&
>  	    !skb->sk &&
> @@ -354,7 +353,6 @@ static int ip_rcv_finish_core(struct net *net,
>  				drop_reason = udp_v4_early_demux(skb);
>  				if (unlikely(drop_reason))

This should be `drop_reason != SKB_NOT_DROPPED_YET`

>  					goto drop_error;
> -				drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>  
>  				/* must reload iph, skb->head might have changed */
>  				iph = ip_hdr(skb);
> @@ -372,7 +370,6 @@ static int ip_rcv_finish_core(struct net *net,
>  						   ip4h_dscp(iph), dev);
>  		if (unlikely(drop_reason))

similarly here.

>  			goto drop_error;
> -		drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>  	} else {
>  		struct in_device *in_dev = __in_dev_get_rcu(dev);
>  
> @@ -391,8 +388,10 @@ static int ip_rcv_finish_core(struct net *net,
>  	}
>  #endif
>  
> -	if (iph->ihl > 5 && ip_rcv_options(skb, dev))
> +	if (iph->ihl > 5 && ip_rcv_options(skb, dev)) {
> +		drop_reason = SKB_DROP_REASON_NOT_SPECIFIED;
>  		goto drop;
> +	}
>  
>  	rt = skb_rtable(skb);
>  	if (rt->rt_type == RTN_MULTICAST) {