net: Fix prefsrc lookups

A bug report (https://bugzilla.kernel.org/show_bug.cgi?id=107071) noted
that the follwoing ip command is failing with v4.3:

    $ ip route add 10.248.5.0/24 dev bond0.250 table vlan_250 src 10.248.5.154
    RTNETLINK answers: Invalid argument

021dd3b8a142d changed the lookup of the given preferred source address to
use the table id passed in, but this assumes the local entries are in the
given table which is not necessarily true for non-VRF use cases. When
validating the preferred source fallback to the local table on failure.

Fixes: 021dd3b8a142d ("net: Add routes to the table associated with the device")
Signed-off-by: David Ahern <dsa@cumulusnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/fib_semantics.c

@@ -923,14 +923,21 @@ static bool fib_valid_prefsrc(struct fib_config *cfg, __be32 fib_prefsrc)
 	if (cfg->fc_type != RTN_LOCAL || !cfg->fc_dst ||
 	    fib_prefsrc != cfg->fc_dst) {
 		u32 tb_id = cfg->fc_table;
+		int rc;
 
 		if (tb_id == RT_TABLE_MAIN)
 			tb_id = RT_TABLE_LOCAL;
 
-		if (inet_addr_type_table(cfg->fc_nlinfo.nl_net,
-					 fib_prefsrc, tb_id) != RTN_LOCAL) {
-			return false;
+		rc = inet_addr_type_table(cfg->fc_nlinfo.nl_net,
+					  fib_prefsrc, tb_id);
+
+		if (rc != RTN_LOCAL && tb_id != RT_TABLE_LOCAL) {
+			rc = inet_addr_type_table(cfg->fc_nlinfo.nl_net,
+						  fib_prefsrc, RT_TABLE_LOCAL);
 		}
+
+		if (rc != RTN_LOCAL)
+			return false;
 	}
 	return true;
 }