@@ -487,6 +487,8 @@ static void sctp_v4_get_dst(struct sctp_transport *t, union sctp_addr *saddr,
*/
rcu_read_lock();
list_for_each_entry_rcu(laddr, &bp->address_list, list) {
+ struct net_device *odev;
+
if (!laddr->valid)
continue;
if (laddr->state != SCTP_ADDR_SRC ||
@@ -504,6 +506,14 @@ static void sctp_v4_get_dst(struct sctp_transport *t, union sctp_addr *saddr,
if (IS_ERR(rt))
continue;
+ /* Ensure the src address belongs to the output
+ * interface.
+ */
+ odev = __ip_dev_find(sock_net(sk), laddr->a.v4.sin_addr.s_addr,
+ false);
+ if (!odev || odev->ifindex != fl4->flowi4_oif)
+ continue;
+
dst = &rt->dst;
break;
}
In short, sctp is likely to incorrectly choose src address if socket is bound to secondary addresses. This patch fixes it by adding a new check that checks if such src address belongs to the interface that routing identified as output. This is enough to avoid rp_filter drops on remote peer. Details: Currently, sctp will do a routing attempt without specifying the src address and compare the returned value (preferred source) with the addresses that the socket is bound to. When using secondary addresses, this will not match. Then it will try specifying each of the addresses that the socket is bound to and re-routing, checking if that address is valid as src for that dst. Thing is, this check alone is weak: # ip r l 192.168.100.0/24 dev eth1 proto kernel scope link src 192.168.100.149 192.168.122.0/24 dev eth0 proto kernel scope link src 192.168.122.147 # ip a l 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:15:18:6a brd ff:ff:ff:ff:ff:ff inet 192.168.122.147/24 brd 192.168.122.255 scope global dynamic eth0 valid_lft 2160sec preferred_lft 2160sec inet 192.168.122.148/24 scope global secondary eth0 valid_lft forever preferred_lft forever inet6 fe80::5054:ff:fe15:186a/64 scope link valid_lft forever preferred_lft forever 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:b3:91:46 brd ff:ff:ff:ff:ff:ff inet 192.168.100.149/24 brd 192.168.100.255 scope global dynamic eth1 valid_lft 2162sec preferred_lft 2162sec inet 192.168.100.148/24 scope global secondary eth1 valid_lft forever preferred_lft forever inet6 fe80::5054:ff:feb3:9146/64 scope link valid_lft forever preferred_lft forever 4: ens9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000 link/ether 52:54:00:05:47:ee brd ff:ff:ff:ff:ff:ff inet6 fe80::5054:ff:fe05:47ee/64 scope link valid_lft forever preferred_lft forever # ip r g 192.168.100.193 from 192.168.122.148 192.168.100.193 from 192.168.122.148 dev eth1 cache Even if you specify an interface: # ip r g 192.168.100.193 from 192.168.122.148 oif eth1 192.168.100.193 from 192.168.122.148 dev eth1 cache Although this would be valid, peers using rp_filter will drop such packets as their src doesn't match the routes for that interface. Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com> --- net/sctp/protocol.c | 10 ++++++++++ 1 file changed, 10 insertions(+)