net: l3mdev: address selection should only consider devices in L3 domain
David Lamparter noted a use case where the source address selection fails
to pick an address from a VRF interface - unnumbered interfaces.
Relevant commands from his script:
ip addr add 9.9.9.9/32 dev lo
ip link set lo up
ip link add name vrf0 type vrf table 101
ip rule add oif vrf0 table 101
ip rule add iif vrf0 table 101
ip link set vrf0 up
ip addr add 10.0.0.3/32 dev vrf0
ip link add name dummy2 type dummy
ip link set dummy2 master vrf0 up
--> note dummy2 has no address - unnumbered device
ip route add 10.2.2.2/32 dev dummy2 table 101
ip neigh add 10.2.2.2 dev dummy2 lladdr 02:00:00:00:00:02
tcpdump -ni dummy2 &
And using ping instead of his socat example:
$ ping -I vrf0 -c1 10.2.2.2
ping: Warning: source address might be selected on device other than vrf0.
PING 10.2.2.2 (10.2.2.2) from 9.9.9.9 vrf0: 56(84) bytes of data.
>From tcpdump:
12:57:29.449128 IP 9.9.9.9 > 10.2.2.2: ICMP echo request, id 2491, seq 1, length 64
Note the source address is from lo and is not a VRF local address. With
this patch:
$ ping -I vrf0 -c1 10.2.2.2
PING 10.2.2.2 (10.2.2.2) from 10.0.0.3 vrf0: 56(84) bytes of data.
>From tcpdump:
12:59:25.096426 IP 10.0.0.3 > 10.2.2.2: ICMP echo request, id 2113, seq 1, length 64
Now the source address comes from vrf0.
The ipv4 function for selecting source address takes a const argument.
Removing the const requires touching a lot of places, so instead
l3mdev_master_ifindex_rcu is changed to take a const argument and then
do the typecast to non-const as required by netdev_master_upper_dev_get_rcu.
This is similar to what l3mdev_fib_table_rcu does.
IPv6 for unnumbered interfaces appears to be selecting the addresses
properly.
Cc: David Lamparter <david@opensourcerouting.org>
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv4/devinet.c b/net/ipv4/devinet.c
index 29b8d3a..18d510f 100644
--- a/net/ipv4/devinet.c
+++ b/net/ipv4/devinet.c
@@ -1194,6 +1194,7 @@
__be32 addr = 0;
struct in_device *in_dev;
struct net *net = dev_net(dev);
+ int master_idx;
rcu_read_lock();
in_dev = __in_dev_get_rcu(dev);
@@ -1214,12 +1215,16 @@
if (addr)
goto out_unlock;
no_in_dev:
+ master_idx = l3mdev_master_ifindex_rcu(dev);
/* Not loopback addresses on loopback should be preferred
in this case. It is important that lo is the first interface
in dev_base list.
*/
for_each_netdev_rcu(net, dev) {
+ if (l3mdev_master_ifindex_rcu(dev) != master_idx)
+ continue;
+
in_dev = __in_dev_get_rcu(dev);
if (!in_dev)
continue;