Re: [PATCH net-next v3 02/10] net: ip: make fib_validate_source() return drop reason

[Paolo Abeni <pabeni@redhat.com>]

On 10/15/24 16:07, Menglong Dong wrote:
> diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
> index 90ff815f212b..b3f7a1562140 100644
> --- a/include/net/ip_fib.h
> +++ b/include/net/ip_fib.h
> @@ -452,13 +452,16 @@ int __fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
>  			  dscp_t dscp, int oif, struct net_device *dev,
>  			  struct in_device *idev, u32 *itag);
>  
> -static inline int
> +static inline enum skb_drop_reason
>  fib_validate_source(struct sk_buff *skb, __be32 src, __be32 dst,
>  		    dscp_t dscp, int oif, struct net_device *dev,
>  		    struct in_device *idev, u32 *itag)
>  {
> -	return __fib_validate_source(skb, src, dst, dscp, oif, dev, idev,
> -				     itag);
> +	int err = __fib_validate_source(skb, src, dst, dscp, oif, dev, idev,
> +					itag);
> +	if (err < 0)
> +		return -err;
> +	return SKB_NOT_DROPPED_YET;
>  }

It looks like the code churn in patch 1 is not needed??? You could just
define here a fib_validate_source_reason() helper doing the above, and
replace fib_validate_source with the the new helper as needed. Would
that work?

> @@ -1785,9 +1785,10 @@ static int __mkroute_input(struct sk_buff *skb, const struct fib_result *res,
>  		return -EINVAL;
>  	}
>  
> -	err = fib_validate_source(skb, saddr, daddr, dscp, FIB_RES_OIF(*res),
> -				  in_dev->dev, in_dev, &itag);
> +	err = __fib_validate_source(skb, saddr, daddr, dscp, FIB_RES_OIF(*res),
> +				    in_dev->dev, in_dev, &itag);
>  	if (err < 0) {
> +		err = -EINVAL;
>  		ip_handle_martian_source(in_dev->dev, in_dev, skb, daddr,
>  					 saddr);

I'm sorry for not noticing this issue before, but must preserve (at
least) the -EXDEV error code from the unpatched version or RP Filter MIB
accounting in ip_rcv_finish_core() will be fooled.

Thanks,

Paolo