Re: [PATCH v6 04/13] arp: Check all configured addresses in ARP filtering

[Stefano Brivio <sbrivio@redhat.com>]

On Sat, 21 Mar 2026 20:43:24 -0400
Jon Maloy <jmaloy@redhat.com> wrote:

> As a preparation for handling multiple addresses, we update ignore_arp()
> to check against all addresses in the unified addrs[] array using the
> for_each_addr() macro.
> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> Reviewed-by: David Gibson <david@gibson.dropbear.id.au>
> 
> ---
> v3: -Adapted to single-array changes earlier in this series
> v6: -Made loop in ignore_arp() a little more palatable,
>      but not entirely as suggested by David.
> ---
>  arp.c | 11 +++++++----
>  1 file changed, 7 insertions(+), 4 deletions(-)
> 
> diff --git a/arp.c b/arp.c
> index 18ff5de..6614804 100644
> --- a/arp.c
> +++ b/arp.c
> @@ -41,7 +41,8 @@
>  static bool ignore_arp(const struct ctx *c,
>  		       const struct arphdr *ah, const struct arpmsg *am)
>  {
> -	const struct guest_addr *a = fwd_get_addr(c, AF_INET, 0, 0);
> +	const struct guest_addr *a;
> +	union inany_addr addr;
>  
>  	if (ah->ar_hrd != htons(ARPHRD_ETHER)	||
>  	    ah->ar_pro != htons(ETH_P_IP)	||
> @@ -55,9 +56,11 @@ static bool ignore_arp(const struct ctx *c,
>  	    !memcmp(am->sip, am->tip, sizeof(am->sip)))
>  		return true;
>  
> -	/* Don't resolve the guest's assigned address, either. */
> -	if (a && !memcmp(am->tip, inany_v4(&a->addr), sizeof(am->tip)))
> -		return true;
> +	/* Don't resolve any of the guest's addresses */
> +	inany_from_af(&addr, AF_INET, am->tip);
> +	for_each_addr(a, c, AF_INET)

It's not really obvious that this iterates over c->addrs. I think it
might be clearer to build for_each_addr() to take c->addrs instead,
even if it's slightly more verbose (but it shouldn't add lines either).

Nit: curly brackets around blocks with multiple lines.

> +		if (inany_equals(&addr, &a->addr))
> +			return true;
>  
>  	return false;
>  }

-- 
Stefano