ipv4: Remove RTO_ONLINK.

RTO_ONLINK was a flag used in ->flowi4_tos that allowed to alter the
scope of an IPv4 route lookup. Setting this flag was equivalent to
specifying RT_SCOPE_LINK in ->flowi4_scope.

With commit ec20b283 ("ipv4: Set scope explicitly in
ip_route_output()."), the last users of RTO_ONLINK have been removed.
Therefore, we can now drop the code that checked this bit and stop
modifying ->flowi4_scope in ip_route_output_key_hash().
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Przemek Kitszel <przemyslaw.kitszel@intel.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://lore.kernel.org/r/57de760565cab55df7b129f523530ac6475865b2.1712754146.git.gnault@redhat.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

include/net/route.h

@@ -35,8 +35,6 @@
 #include <linux/cache.h>
 #include <linux/security.h>
 
-#define RTO_ONLINK	0x01
-
 static inline __u8 ip_sock_rt_scope(const struct sock *sk)
 {
 	if (sock_flag(sk, SOCK_LOCALROUTE))

net/ipv4/route.c

@@ -106,9 +106,6 @@
 
 #include "fib_lookup.h"
 
-#define RT_FL_TOS(oldflp4) \
-	((oldflp4)->flowi4_tos & (IPTOS_RT_MASK | RTO_ONLINK))
-
 #define RT_GC_TIMEOUT (300*HZ)
 
 #define DEFAULT_MIN_PMTU (512 + 20 + 20)
@@ -498,15 +495,6 @@ void __ip_select_ident(struct net *net, struct iphdr *iph, int segs)
 }
 EXPORT_SYMBOL(__ip_select_ident);
 
-static void ip_rt_fix_tos(struct flowi4 *fl4)
-{
-	__u8 tos = RT_FL_TOS(fl4);
-
-	fl4->flowi4_tos = tos & IPTOS_RT_MASK;
-	if (tos & RTO_ONLINK)
-		fl4->flowi4_scope = RT_SCOPE_LINK;
-}
-
 static void __build_flow_key(const struct net *net, struct flowi4 *fl4,
 			     const struct sock *sk, const struct iphdr *iph,
 			     int oif, __u8 tos, u8 prot, u32 mark,
@@ -2636,7 +2624,7 @@ struct rtable *ip_route_output_key_hash(struct net *net, struct flowi4 *fl4,
 	struct rtable *rth;
 
 	fl4->flowi4_iif = LOOPBACK_IFINDEX;
-	ip_rt_fix_tos(fl4);
+	fl4->flowi4_tos &= IPTOS_RT_MASK;
 
 	rcu_read_lock();
 	rth = ip_route_output_key_hash_rcu(net, fl4, &res, skb);