net: igmp: Use correct source address on IGMPv3 reports

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@chromium.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index 50448a220a1f26e29715bffc1b86f1f749e5a61d..726f6b6082748896686ae603546fa189348f9142 100644 (file)
--- 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 type, int gdeleted, int sdeleted)
        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(struct net_device *dev, unsigned int mtu)
        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);