ipv4: ipmr: Unmask upper DSCP bits in ipmr_queue_xmit()

Unmask the upper DSCP bits when calling ip_route_output_ports() so that
in the future it could perform the FIB lookup according to the full DSCP
value.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20240903135327.2810535-3-idosch@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/ipmr.c

@@ -1869,15 +1869,15 @@ static void ipmr_queue_xmit(struct net *net, struct mr_table *mrt,
 					   vif->remote, vif->local,
 					   0, 0,
 					   IPPROTO_IPIP,
-					   RT_TOS(iph->tos), vif->link);
+					   iph->tos & INET_DSCP_MASK, vif->link);
 		if (IS_ERR(rt))
 			goto out_free;
 		encap = sizeof(struct iphdr);
 	} else {
 		rt = ip_route_output_ports(net, &fl4, NULL, iph->daddr, 0,
 					   0, 0,
 					   IPPROTO_IPIP,
-					   RT_TOS(iph->tos), vif->link);
+					   iph->tos & INET_DSCP_MASK, vif->link);
 		if (IS_ERR(rt))
 			goto out_free;
 	}