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

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Date:	Tue, 29 Mar 2011 11:11:45 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Timo Teräs <timo.teras@....fi>
Cc:	netdev@...r.kernel.org, Doug Kehn <rdkehn@...oo.com>
Subject: Re: [PATCH] net: gre: provide multicast mappings for ipv4 and ipv6

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 <rdkehn@...oo.com>
> Signed-off-by: Timo Teräs <timo.teras@....fi>
> ---
> 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;
> +}


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