ipv4: Don't reset ->flowi4_scope in ip_rt_fix_tos().

JIRA: https://issues.redhat.com/browse/RHEL-59754
Upstream Status: net.git commit 16a2826

commit 16a2826
Author: Guillaume Nault <gnault@redhat.com>
Date:   Thu Apr 21 01:21:24 2022 +0200

    ipv4: Don't reset ->flowi4_scope in ip_rt_fix_tos().

    All callers already initialise ->flowi4_scope with RT_SCOPE_UNIVERSE,
    either by manual field assignment, memset(0) of the whole structure or
    implicit structure initialisation of on-stack variables
    (RT_SCOPE_UNIVERSE actually equals 0).

    Therefore, we don't need to always initialise ->flowi4_scope in
    ip_rt_fix_tos(). We only need to reduce the scope to RT_SCOPE_LINK when
    the special RTO_ONLINK flag is present in the tos.

    This will allow some code simplification, like removing
    ip_rt_fix_tos(). Also, the long term idea is to remove RTO_ONLINK
    entirely by properly initialising ->flowi4_scope, instead of
    overloading ->flowi4_tos with a special flag. Eventually, this will
    allow to convert ->flowi4_tos to dscp_t.

    Signed-off-by: Guillaume Nault <gnault@redhat.com>
    Reviewed-by: David Ahern <dsahern@kernel.org>
    Signed-off-by: David S. Miller <davem@davemloft.net>

Signed-off-by: Hangbin Liu <haliu@redhat.com>

Author: Hangbin Liu

net/ipv4/route.c

@@ -512,8 +512,8 @@ static void ip_rt_fix_tos(struct flowi4 *fl4)
 	__u8 tos = RT_FL_TOS(fl4);
 
 	fl4->flowi4_tos = tos & IPTOS_RT_MASK;
-	fl4->flowi4_scope = tos & RTO_ONLINK ?
-			    RT_SCOPE_LINK : RT_SCOPE_UNIVERSE;
+	if (tos & RTO_ONLINK)
+		fl4->flowi4_scope = RT_SCOPE_LINK;
 }
 
 static void __build_flow_key(const struct net *net, struct flowi4 *fl4,