Re: [PATCH RESEND net-next v4 9/9] net: ip: make ip_route_use_hint() return drop reasons

[Paolo Abeni <pabeni@xxxxxxxxxx>]

On 10/30/24 02:41, Menglong Dong wrote:
> diff --git a/net/ipv4/route.c b/net/ipv4/route.c
> index e248e5577d0e..7f969c865c81 100644
> --- a/net/ipv4/route.c
> +++ b/net/ipv4/route.c
> @@ -2142,28 +2142,34 @@ ip_mkroute_input(struct sk_buff *skb, struct fib_result *res,
>   * assuming daddr is valid and the destination is not a local broadcast one.
>   * Uses the provided hint instead of performing a route lookup.
>   */
> -int ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
> -		      dscp_t dscp, struct net_device *dev,
> -		      const struct sk_buff *hint)
> +enum skb_drop_reason
> +ip_route_use_hint(struct sk_buff *skb, __be32 daddr, __be32 saddr,
> +		  dscp_t dscp, struct net_device *dev,
> +		  const struct sk_buff *hint)
>  {
> +	enum skb_drop_reason reason = SKB_DROP_REASON_NOT_SPECIFIED;
>  	struct in_device *in_dev = __in_dev_get_rcu(dev);
>  	struct rtable *rt = skb_rtable(hint);
>  	struct net *net = dev_net(dev);
> -	enum skb_drop_reason reason;
> -	int err = -EINVAL;
>  	u32 tag = 0;
>  
>  	if (!in_dev)
> -		return -EINVAL;
> +		return reason;
>  
> -	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr))
> +	if (ipv4_is_multicast(saddr) || ipv4_is_lbcast(saddr)) {
> +		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
>  		goto martian_source;
> +	}
>  
> -	if (ipv4_is_zeronet(saddr))
> +	if (ipv4_is_zeronet(saddr)) {
> +		reason = SKB_DROP_REASON_IP_INVALID_SOURCE;
>  		goto martian_source;
> +	}
>  
> -	if (ipv4_is_loopback(saddr) && !IN_DEV_NET_ROUTE_LOCALNET(in_dev, net))
> +	if (ipv4_is_loopback(saddr) && !IN_DEV_NET_ROUTE_LOCALNET(in_dev, net)) {
> +		reason = IP_LOCALNET;
>  		goto martian_source;
> +	}
>  
>  	if (rt->rt_type != RTN_LOCAL)
>  		goto skip_validate_source;

Please explicitly replace also the

	return 0;

with

	return SKB_NOT_DROPPED_YET;

So that is clear the drop reason is always specified.

Thanks,

Paolo