Subject: Re: [PATCH] net: gre: provide multicast mappings for ipv4 and ipv6

From: Timo Teräs <[email-masked]>
Date: Tue, 29 Mar 2011 13:00:32 +0300

On 03/29/2011 12:11 PM, Eric Dumazet wrote:
> Le mardi 29 mars 2011 à 11:40 +0300, Timo Teräs a écrit :
>> My commit 6d55cb91a0020ac0 (gre: fix hard header destination
>> address checking) broke multicast.
>>
>> The reason is that ip_gre used to get ipgre_header() calls with
>> zero destination if we have NOARP or multicast destination. Instead
>> the actual target was decided at ipgre_tunnel_xmit() time based on
>> per-protocol dissection.
>>
>> Instead of allowing the "abuse" of ->header() calls with invalid
>> destination, this creates multicast mappings for ip_gre. This also
>> fixes "ip neigh show nud noarp" to display the proper multicast
>> mappings used by the gre device.
>>
>> Reported-by: Doug Kehn <[email-masked]>
>> Signed-off-by: Timo Teräs <[email-masked]>
>> ---
>> Compile tested only. Doug tested IPv4 side with the earlier patch.
> 
> 
>> +static inline int ipv6_ipgre_mc_map(const struct in6_addr *addr,
>> +				    const unsigned char *broadcast, char *buf)
>> +{
>> +	if ((broadcast[0] | broadcast[1] | broadcast[2] | broadcast[3]) != 0) {
>> +		memcpy(buf, broadcast, 4);
>> +	} else {
>> +		/* v4mapped? */
>> +		if ((addr->s6_addr32[0] | addr->s6_addr32[1] |
>> +		     (addr->s6_addr32[2] ^ htonl(0x0000ffff))) != 0)
>> +			return -EINVAL;
> 
> 		if (ipv6_addr_v4mapped(addr))
> 
> 
>> +		memcpy(buf, &addr->s6_addr32[3], 4);
>> +	}
>> +	return 0;
>> +}

I wanted to put the function same header as all other similar ones:
net/if_inet6.h. However, ipv6_addr_v4mapped() is defined in net/ipv6.h
which includes net/if_inet6.h. So I can't really use that function there.