Subject: Re: [PATCH 1/3] netfilter: xt_ipvs (netfilter matcher for IPVS)

From: Patrick McHardy <[email-masked]>
Date: Wed, 02 Sep 2009 17:36:04 +0200

Hannes Eder wrote:
> On Wed, Sep 2, 2009 at 16:54, Patrick McHardy<[email-masked]> wrote:
>> Hannes Eder wrote:
>>> This implements the kernel-space side of the netfilter matcher
>>> xt_ipvs.
>> Looks mostly fine to me, just one question:
>>
>>> +bool ipvs_mt(const struct sk_buff *skb, const struct xt_match_param *par)
>>> +{
>>> +     const struct xt_ipvs *data = par->matchinfo;
>>> +     const u_int8_t family = par->family;
>>> +     struct ip_vs_iphdr iph;
>>> +     struct ip_vs_protocol *pp;
>>> +     struct ip_vs_conn *cp;
>>> +     int af;
>>> +     bool match = true;
>>> +
>>> +     if (data->bitmask == XT_IPVS_IPVS_PROPERTY) {
>>> +             match = skb->ipvs_property ^
>>> +                     !!(data->invert & XT_IPVS_IPVS_PROPERTY);
>>> +             goto out;
>>> +     }
>>> +
>>> +     /* other flags than XT_IPVS_IPVS_PROPERTY are set */
>>> +     if (!skb->ipvs_property) {
>>> +             match = false;
>>> +             goto out;
>>> +     }
>>> +
>>> +     switch (skb->protocol) {
>>> +     case  htons(ETH_P_IP):
>>> +             af = AF_INET;
>>> +             break;
>>> +#ifdef CONFIG_IP_VS_IPV6
>>> +     case  htons(ETH_P_IPV6):
>>> +             af = AF_INET6;
>>> +             break;
>>> +#endif
>>> +     default:
>>> +             match = false;
>>> +             goto out;
>>> +     }
>> In the NF_INET_LOCAL_OUT hook skb->protocol is invalid. So if you
>> don't need this, it would make sense to restrict the match to the
>> other hooks.
>>
>> Even easier would be to use par->family, which contains the address
>> family and doesn't need any translation.
> 
> Nice, I'll use par->family.
> 
> So in theory I do not even need a check like the following in the beginning?
> 
> 	if (family != NFPROTO_IPV4
> #ifdef CONFIG_IP_VS_IPV6
> 	    && family != NFPROTO_IPV6
> #endif
> 		) {
> 		match = false;
> 		goto out;
> 	}

With the AF_UNSPEC registration of your match, it might be used
with different families. But you could add two seperate IPV4/IPV6
registrations or catch an invalid family in ->checkentry() and
remove the runtime check.