netdev - [PATCH net-next 5/8] inet: add dst4_mtu() and dst6

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Message-ID: <20260130210303.3888261-6-edumazet@google.com>
Date: Fri, 30 Jan 2026 21:03:00 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, 
	Paolo Abeni <pabeni@...hat.com>
Cc: Simon Horman <horms@...nel.org>, David Ahern <dsahern@...nel.org>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, netdev@...r.kernel.org, eric.dumazet@...il.com, 
	Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH net-next 5/8] inet: add dst4_mtu() and dst6_mtu() helpers

With CONFIG_MITIGATION_RETPOLINE=y dst_mtu() is a bit fat,
because it is generic.

Indeed, clang does not always inline it.

Add dst4_mtu() and dst6_mtu() helpers for callers that
expect either ipv4_mtu() or ip6_mtu() to be called.

These helpers are always inlined.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/dst.h       | 6 ++++++
 include/net/ip6_route.h | 6 ++++++
 2 files changed, 12 insertions(+)

diff --git a/include/net/dst.h b/include/net/dst.h
index f8aa1239b4db639bd6b63f4ddb4ec4d7ee459ac0..307073eae7f83456aa80dfa8686f839b302ca004 100644
--- a/include/net/dst.h
+++ b/include/net/dst.h
@@ -219,6 +219,12 @@ static inline u32 dst_mtu(const struct dst_entry *dst)
 	return INDIRECT_CALL_INET(dst->ops->mtu, ip6_mtu, ipv4_mtu, dst);
 }
 
+/* Variant of dst_mtu() for IPv4 users. */
+static inline u32 dst4_mtu(const struct dst_entry *dst)
+{
+	return INDIRECT_CALL_1(dst->ops->mtu, ipv4_mtu, dst);
+}
+
 /* RTT metrics are stored in milliseconds for user ABI, but used as jiffies */
 static inline unsigned long dst_metric_rtt(const struct dst_entry *dst, int metric)
 {
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 7c5512baa4b2b7503494b1ae02756df29ef93666..a55f9bf95fe393311967b9b94073acb3860214aa 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -266,6 +266,12 @@ static inline bool ipv6_anycast_destination(const struct dst_entry *dst,
 int ip6_fragment(struct net *net, struct sock *sk, struct sk_buff *skb,
 		 int (*output)(struct net *, struct sock *, struct sk_buff *));
 
+/* Variant of dst_mtu() for IPv6 users */
+static inline u32 dst6_mtu(const struct dst_entry *dst)
+{
+	return INDIRECT_CALL_1(dst->ops->mtu, ip6_mtu, dst);
+}
+
 static inline unsigned int ip6_skb_dst_mtu(const struct sk_buff *skb)
 {
 	const struct ipv6_pinfo *np = skb->sk && !dev_recursion_level() ?
-- 
2.53.0.rc1.225.gd81095ad13-goog