netdev - [PATCH net-next 4/7] net: Switch to skb_dst_reset/skb_dst_restore for ip_route

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Message-ID: <20250812155245.507012-5-sdf@fomichev.me>
Date: Tue, 12 Aug 2025 08:52:42 -0700
From: Stanislav Fomichev <sdf@...ichev.me>
To: netdev@...r.kernel.org
Cc: davem@...emloft.net,
	edumazet@...gle.com,
	kuba@...nel.org,
	pabeni@...hat.com,
	ayush.sawal@...lsio.com,
	andrew+netdev@...n.ch,
	gregkh@...uxfoundation.org,
	horms@...nel.org,
	dsahern@...nel.org,
	pablo@...filter.org,
	kadlec@...filter.org,
	steffen.klassert@...unet.com,
	sdf@...ichev.me,
	mhal@...x.co,
	abhishektamboli9@...il.com,
	linux-kernel@...r.kernel.org,
	linux-staging@...ts.linux.dev,
	netfilter-devel@...r.kernel.org,
	coreteam@...filter.org,
	herbert@...dor.apana.org.au
Subject: [PATCH net-next 4/7] net: Switch to skb_dst_reset/skb_dst_restore for ip_route_input callers

Going forward skb_dst_set will assert that skb dst_entry
is empty during skb_dst_set. skb_dst_reset is added to reset
existing entry without doing refcnt. skb_dst_restore should
be used to restore the previous entry. Convert icmp_route_lookup
and ip_options_rcv_srr to these helpers. Add extra call to
skb_dst_drop to icmp_route_lookup to clear the ip_route_input
entry.

Signed-off-by: Stanislav Fomichev <sdf@...ichev.me>
---
 net/ipv4/icmp.c       | 7 ++++---
 net/ipv4/ip_options.c | 5 ++---
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index 2ffe73ea644f..93a166a7ec8d 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -544,14 +544,15 @@ static struct rtable *icmp_route_lookup(struct net *net, struct flowi4 *fl4,
 			goto relookup_failed;
 		}
 		/* Ugh! */
-		orefdst = skb_in->_skb_refdst; /* save old refdst */
-		skb_dst_set(skb_in, NULL);
+		orefdst = skb_dst_reset(skb_in);
 		err = ip_route_input(skb_in, fl4_dec.daddr, fl4_dec.saddr,
 				     dscp, rt2->dst.dev) ? -EINVAL : 0;
 
 		dst_release(&rt2->dst);
 		rt2 = skb_rtable(skb_in);
-		skb_in->_skb_refdst = orefdst; /* restore old refdst */
+		/* steal dst entry from skb_in, don't drop refcnt */
+		skb_dst_reset(skb_in);
+		skb_dst_restore(skb_in, orefdst);
 	}
 
 	if (err)
diff --git a/net/ipv4/ip_options.c b/net/ipv4/ip_options.c
index e3321932bec0..95f113dc37d8 100644
--- a/net/ipv4/ip_options.c
+++ b/net/ipv4/ip_options.c
@@ -615,14 +615,13 @@ int ip_options_rcv_srr(struct sk_buff *skb, struct net_device *dev)
 		}
 		memcpy(&nexthop, &optptr[srrptr-1], 4);
 
-		orefdst = skb->_skb_refdst;
-		skb_dst_set(skb, NULL);
+		orefdst = skb_dst_reset(skb);
 		err = ip_route_input(skb, nexthop, iph->saddr, ip4h_dscp(iph),
 				     dev) ? -EINVAL : 0;
 		rt2 = skb_rtable(skb);
 		if (err || (rt2->rt_type != RTN_UNICAST && rt2->rt_type != RTN_LOCAL)) {
 			skb_dst_drop(skb);
-			skb->_skb_refdst = orefdst;
+			skb_dst_restore(skb, orefdst);
 			return -EINVAL;
 		}
 		refdst_drop(orefdst);
-- 
2.50.1