net: igmp: Use correct source address on IGMPv3 reports (a46182b0) · Commits · 戴 / test

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>

net/ipv4/igmp.c

+19 −1

Original line number	Diff line number	Diff line
		@@ -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);

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