mlxsw: spectrum_router: Allow programming link-local prefix routes

The device has a trap for IPv6 packets that need be routed and have a
unicast link-local destination IP (i.e., fe80::/10). This allows mlxsw
to ignore link-local routes, as the packets will be trapped to the CPU
in any case.

However, since link-local routes are not programmed, it is possible for
routed packets to hit the default route which might also be programmed
to trap packets. This means that packets with a link-local destination
IP might be trapped for the wrong reason.

To overcome this, allow programming link-local prefix routes (usually
one fe80::/64 per-table), so that the packets will be forwarded until
reaching the link-local trap.
Signed-off-by: Ido Schimmel <idosch@mellanox.com>
Reviewed-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlxsw/spectrum_router.c

@@ -5003,9 +5003,11 @@ static bool mlxsw_sp_fib6_rt_should_ignore(const struct fib6_info *rt)
 {
 	/* Packets with link-local destination IP arriving to the router
 	 * are trapped to the CPU, so no need to program specific routes
-	 * for them.
+	 * for them. Only allow prefix routes (usually one fe80::/64) so
+	 * that packets are trapped for the right reason.
 	 */
-	if (ipv6_addr_type(&rt->fib6_dst.addr) & IPV6_ADDR_LINKLOCAL)
+	if ((ipv6_addr_type(&rt->fib6_dst.addr) & IPV6_ADDR_LINKLOCAL) &&
+	    (rt->fib6_flags & (RTF_LOCAL | RTF_ANYCAST)))
 		return true;
 
 	/* Multicast routes aren't supported, so ignore them. Neighbour