linux-kernel - Re: [PATCH 4.9 27/75] net: igmp: Use correct source address on IGMPv3 reports

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Date:   Tue, 16 Jan 2018 04:50:39 +0100
From:   Sebastian Gottschall <s.gottschall@...wrt.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org
Cc:     stable@...r.kernel.org, Kevin Cernekee <cernekee@...omium.org>,
        Andrew Lunn <andrew@...n.ch>,
        "David S. Miller" <davem@...emloft.net>
Subject: Re: [PATCH 4.9 27/75] net: igmp: Use correct source address on IGMPv3
 reports

please revert that on 4.9 and 4.14
it breaks igmp routing. it can be reproduced with any iptv connection 
using igmp-proxy. reverting this patch fixes the issue.

Sebastian



Am 01.01.2018 um 15:32 schrieb Greg Kroah-Hartman:
> 4.9-stable review patch.  If anyone has any objections, please let me know.
>
> ------------------
>
> From: Kevin Cernekee <cernekee@...omium.org>
>
>
> [ Upstream commit a46182b00290839fa3fa159d54fd3237bd8669f0 ]
>
> Closing a multicast socket after the final IPv4 address is deleted
> from an interface can generate a membership report that uses the
> source IP from a different interface.  The following test script, run
> from an isolated netns, reproduces the issue:
>
>      #!/bin/bash
>
>      ip link add dummy0 type dummy
>      ip link add dummy1 type dummy
>      ip link set dummy0 up
>      ip link set dummy1 up
>      ip addr add 10.1.1.1/24 dev dummy0
>      ip addr add 192.168.99.99/24 dev dummy1
>
>      tcpdump -U -i dummy0 &
>      socat EXEC:"sleep 2" \
>          UDP4-DATAGRAM:239.101.1.68:8889,ip-add-membership=239.0.1.68:10.1.1.1 &
>
>      sleep 1
>      ip addr del 10.1.1.1/24 dev dummy0
>      sleep 5
>      kill %tcpdump
>
> RFC 3376 specifies that the report must be sent with a valid IP source
> address from the destination subnet, or from address 0.0.0.0.  Add an
> extra check to make sure this is the case.
>
> Signed-off-by: Kevin Cernekee <cernekee@...omium.org>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: David S. Miller <davem@...emloft.net>
> Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> ---
>   net/ipv4/igmp.c |   20 +++++++++++++++++++-
>   1 file changed, 19 insertions(+), 1 deletion(-)
>
> --- a/net/ipv4/igmp.c
> +++ b/net/ipv4/igmp.c
> @@ -89,6 +89,7 @@
>   #include <linux/rtnetlink.h>
>   #include <linux/times.h>
>   #include <linux/pkt_sched.h>
> +#include <linux/byteorder/generic.h>
>   
>   #include <net/net_namespace.h>
>   #include <net/arp.h>
> @@ -321,6 +322,23 @@ igmp_scount(struct ip_mc_list *pmc, int
>   	return scount;
>   }
>   
> +/* source address selection per RFC 3376 section 4.2.13 */
> +static __be32 igmpv3_get_srcaddr(struct net_device *dev,
> +				 const struct flowi4 *fl4)
> +{
> +	struct in_device *in_dev = __in_dev_get_rcu(dev);
> +
> +	if (!in_dev)
> +		return htonl(INADDR_ANY);
> +
> +	for_ifa(in_dev) {
> +		if (inet_ifa_match(fl4->saddr, ifa))
> +			return fl4->saddr;
> +	} endfor_ifa(in_dev);
> +
> +	return htonl(INADDR_ANY);
> +}
> +
>   static struct sk_buff *igmpv3_newpack(struct net_device *dev, unsigned int mtu)
>   {
>   	struct sk_buff *skb;
> @@ -368,7 +386,7 @@ static struct sk_buff *igmpv3_newpack(st
>   	pip->frag_off = htons(IP_DF);
>   	pip->ttl      = 1;
>   	pip->daddr    = fl4.daddr;
> -	pip->saddr    = fl4.saddr;
> +	pip->saddr    = igmpv3_get_srcaddr(dev, &fl4);
>   	pip->protocol = IPPROTO_IGMP;
>   	pip->tot_len  = 0;	/* filled in later */
>   	ip_select_ident(net, skb, NULL);
>
>
>

-- 
Mit freundlichen Grüssen / Regards

Sebastian Gottschall / CTO

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