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 <[email protected]>
---
net/ipv4/igmp.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
diff --git a/net/ipv4/igmp.c b/net/ipv4/igmp.c
index d1f8f302dbf3..0672264c9d93 100644
--- 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);
--
2.15.1.424.g9478a66081-goog
On Mon, Dec 11, 2017 at 11:13:45AM -0800, Kevin Cernekee wrote:
> 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 <[email protected]>
Reviewed-by: Andrew Lunn <[email protected]>
Andrew
From: Kevin Cernekee <[email protected]>
Date: Mon, 11 Dec 2017 11:13:45 -0800
> 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 <[email protected]>
...
> + 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);
Ok, and I checked that MC source address validation on the receiver
will pass because:
if (ipv4_is_zeronet(saddr)) {
if (!ipv4_is_local_multicast(daddr))
return -EINVAL;
that check in ip_mc_validate_source() won't trigger.