inet: introduce dst_rtable() helper

I added dst_rt6_info() in commit
e8dfd42c17fa ("ipv6: introduce dst_rt6_info() helper")

This patch does a similar change for IPv4.

Instead of (struct rtable *)dst casts, we can use :

 #define dst_rtable(_ptr) \
             container_of_const(_ptr, struct rtable, dst)

Patch is smaller than IPv6 one, because IPv4 has skb_rtable() helper.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Link: https://lore.kernel.org/r/20240429133009.1227754-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

1 files changed, 11 insertions, 13 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index f89ff2e5a05b..0fd9a3d7ac4a 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -819,7 +819,7 @@ static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buf
 	u32 mark = skb->mark;
 	__u8 tos = iph->tos;
 
-	rt = (struct rtable *) dst;
+	rt = dst_rtable(dst);
 
 	__build_flow_key(net, &fl4, sk, iph, oif, tos, prot, mark, 0);
 	__ip_do_redirect(rt, skb, &fl4, true);
@@ -827,7 +827,7 @@ static void ip_do_redirect(struct dst_entry *dst, struct sock *sk, struct sk_buf
 
 static struct dst_entry *ipv4_negative_advice(struct dst_entry *dst)
 {
-	struct rtable *rt = (struct rtable *)dst;
+	struct rtable *rt = dst_rtable(dst);
 	struct dst_entry *ret = dst;
 
 	if (rt) {
@@ -1044,7 +1044,7 @@ static void ip_rt_update_pmtu(struct dst_entry *dst, struct sock *sk,
 			      struct sk_buff *skb, u32 mtu,
 			      bool confirm_neigh)
 {
-	struct rtable *rt = (struct rtable *) dst;
+	struct rtable *rt = dst_rtable(dst);
 	struct flowi4 fl4;
 
 	ip_rt_build_flow_key(&fl4, sk, skb);
@@ -1115,7 +1115,7 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
 
 	__build_flow_key(net, &fl4, sk, iph, 0, 0, 0, 0, 0);
 
-	rt = (struct rtable *)odst;
+	rt = dst_rtable(odst);
 	if (odst->obsolete && !odst->ops->check(odst, 0)) {
 		rt = ip_route_output_flow(sock_net(sk), &fl4, sk);
 		if (IS_ERR(rt))
@@ -1124,7 +1124,7 @@ void ipv4_sk_update_pmtu(struct sk_buff *skb, struct sock *sk, u32 mtu)
 		new = true;
 	}
 
-	__ip_rt_update_pmtu((struct rtable *)xfrm_dst_path(&rt->dst), &fl4, mtu);
+	__ip_rt_update_pmtu(dst_rtable(xfrm_dst_path(&rt->dst)), &fl4, mtu);
 
 	if (!dst_check(&rt->dst, 0)) {
 		if (new)
@@ -1181,7 +1181,7 @@ EXPORT_SYMBOL_GPL(ipv4_sk_redirect);
 INDIRECT_CALLABLE_SCOPE struct dst_entry *ipv4_dst_check(struct dst_entry *dst,
 							 u32 cookie)
 {
-	struct rtable *rt = (struct rtable *) dst;
+	struct rtable *rt = dst_rtable(dst);
 
 	/* All IPV4 dsts are created with ->obsolete set to the value
 	 * DST_OBSOLETE_FORCE_CHK which forces validation calls down
@@ -1516,10 +1516,8 @@ void rt_del_uncached_list(struct rtable *rt)
 
 static void ipv4_dst_destroy(struct dst_entry *dst)
 {
-	struct rtable *rt = (struct rtable *)dst;
-
 	ip_dst_metrics_put(dst);
-	rt_del_uncached_list(rt);
+	rt_del_uncached_list(dst_rtable(dst));
 }
 
 void rt_flush_dev(struct net_device *dev)
@@ -2820,7 +2818,7 @@ static struct dst_ops ipv4_dst_blackhole_ops = {
 
 struct dst_entry *ipv4_blackhole_route(struct net *net, struct dst_entry *dst_orig)
 {
-	struct rtable *ort = (struct rtable *) dst_orig;
+	struct rtable *ort = dst_rtable(dst_orig);
 	struct rtable *rt;
 
 	rt = dst_alloc(&ipv4_dst_blackhole_ops, NULL, DST_OBSOLETE_DEAD, 0);
@@ -2865,9 +2863,9 @@ struct rtable *ip_route_output_flow(struct net *net, struct flowi4 *flp4,
 
 	if (flp4->flowi4_proto) {
 		flp4->flowi4_oif = rt->dst.dev->ifindex;
-		rt = (struct rtable *)xfrm_lookup_route(net, &rt->dst,
-							flowi4_to_flowi(flp4),
-							sk, 0);
+		rt = dst_rtable(xfrm_lookup_route(net, &rt->dst,
+						  flowi4_to_flowi(flp4),
+						  sk, 0));
 	}
 
 	return rt;