xfrm: Unmask upper DSCP bits in xfrm_get_tos()

The function returns a value that is used to initialize 'flowi4_tos'
before being passed to the FIB lookup API in the following call chain:

xfrm_bundle_create()
	tos = xfrm_get_tos(fl, family)
	xfrm_dst_lookup(..., tos, ...)
		__xfrm_dst_lookup(..., tos, ...)
			xfrm4_dst_lookup(..., tos, ...)
				__xfrm4_dst_lookup(..., tos, ...)
					fl4->flowi4_tos = tos
					__ip_route_output_key(net, fl4)

Unmask the upper DSCP bits so that in the future the output route lookup
could be performed according to the full DSCP value.

Remove IPTOS_RT_MASK since it is no longer used.
Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/route.h

@@ -266,8 +266,6 @@ static inline void ip_rt_put(struct rtable *rt)
 	dst_release(&rt->dst);
 }
 
-#define IPTOS_RT_MASK	(IPTOS_TOS_MASK & ~3)
-
 extern const __u8 ip_tos2prio[16];
 
 static inline char rt_tos2priority(u8 tos)

net/xfrm/xfrm_policy.c

@@ -45,6 +45,7 @@
 #ifdef CONFIG_XFRM_ESPINTCP
 #include <net/espintcp.h>
 #endif
+#include <net/inet_dscp.h>
 
 #include "xfrm_hash.h"
 
@@ -2561,7 +2562,7 @@ xfrm_tmpl_resolve(struct xfrm_policy **pols, int npols, const struct flowi *fl,
 static int xfrm_get_tos(const struct flowi *fl, int family)
 {
 	if (family == AF_INET)
-		return IPTOS_RT_MASK & fl->u.ip4.flowi4_tos;
+		return fl->u.ip4.flowi4_tos & INET_DSCP_MASK;
 
 	return 0;
 }