[PATCH net-next] tcp: move inet6_csk_update_pmtu() to tcp_ipv6.c

[PATCH net-next] tcp: move inet6_csk_update_pmtu() to tcp_ipv6.c

[Eric Dumazet]

This function is only called from tcp_v6_mtu_reduced() and can be
(auto)inlined by the compiler.

Note that inet6_csk_route_socket() is no longer (auto)inlined,
which is a good thing as it is slow path.

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1

add/remove: 0/2 grow/shrink: 2/0 up/down: 93/-129 (-36)
Function                                     old     new   delta
tcp_v6_mtu_reduced                           139     228     +89
inet6_csk_route_socket                       486     490      +4
__pfx_inet6_csk_update_pmtu                   16       -     -16
inet6_csk_update_pmtu                        113       -    -113
Total: Before=25076512, After=25076476, chg -0.00%

Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 include/net/inet6_connection_sock.h |  4 +++-
 net/ipv6/inet6_connection_sock.c    | 19 ++-----------------
 net/ipv6/tcp_ipv6.c                 | 15 +++++++++++++++
 3 files changed, 20 insertions(+), 18 deletions(-)

diff --git a/include/net/inet6_connection_sock.h b/include/net/inet6_connection_sock.h
index ece8dabd209a5b2fb42ec88b9acbc81c01b4174e..b814e1acc512186108f500702836d98647cbd165 100644
--- a/include/net/inet6_connection_sock.h
+++ b/include/net/inet6_connection_sock.h
@@ -18,6 +18,9 @@ struct sk_buff;
 struct sock;
 struct sockaddr;
 
+struct dst_entry *inet6_csk_route_socket(struct sock *sk,
+					 struct flowi6 *fl6);
+
 struct dst_entry *inet6_csk_route_req(const struct sock *sk,
 				      struct dst_entry *dst,
 				      struct flowi6 *fl6,
@@ -25,5 +28,4 @@ struct dst_entry *inet6_csk_route_req(const struct sock *sk,
 
 int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl);
 
-struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu);
 #endif /* _INET6_CONNECTION_SOCK_H */
diff --git a/net/ipv6/inet6_connection_sock.c b/net/ipv6/inet6_connection_sock.c
index 11fc2f7de2fe981ddb48dc008bf7fd4ae1e4e2f6..37534e1168992c44e1400dacab87e79d04c64a41 100644
--- a/net/ipv6/inet6_connection_sock.c
+++ b/net/ipv6/inet6_connection_sock.c
@@ -56,8 +56,8 @@ struct dst_entry *inet6_csk_route_req(const struct sock *sk,
 	return dst;
 }
 
-static struct dst_entry *inet6_csk_route_socket(struct sock *sk,
-						struct flowi6 *fl6)
+struct dst_entry *inet6_csk_route_socket(struct sock *sk,
+					 struct flowi6 *fl6)
 {
 	struct inet_sock *inet = inet_sk(sk);
 	struct ipv6_pinfo *np = inet6_sk(sk);
@@ -118,18 +118,3 @@ int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl_unused
 	return res;
 }
 EXPORT_SYMBOL_GPL(inet6_csk_xmit);
-
-struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu)
-{
-	struct flowi6 *fl6 = &inet_sk(sk)->cork.fl.u.ip6;
-	struct dst_entry *dst;
-
-	dst = inet6_csk_route_socket(sk, fl6);
-
-	if (IS_ERR(dst))
-		return NULL;
-	dst->ops->update_pmtu(dst, sk, NULL, mtu, true);
-
-	dst = inet6_csk_route_socket(sk, fl6);
-	return IS_ERR(dst) ? NULL : dst;
-}
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d10487b4e5bff87d4ff2a7b912a826964101a163..010f3aa72499358a96327fcf096e7542bbb5cc81 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -349,6 +349,21 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr_unsized *uaddr,
 	return err;
 }
 
+static struct dst_entry *inet6_csk_update_pmtu(struct sock *sk, u32 mtu)
+{
+	struct flowi6 *fl6 = &inet_sk(sk)->cork.fl.u.ip6;
+	struct dst_entry *dst;
+
+	dst = inet6_csk_route_socket(sk, fl6);
+
+	if (IS_ERR(dst))
+		return NULL;
+	dst->ops->update_pmtu(dst, sk, NULL, mtu, true);
+
+	dst = inet6_csk_route_socket(sk, fl6);
+	return IS_ERR(dst) ? NULL : dst;
+}
+
 static void tcp_v6_mtu_reduced(struct sock *sk)
 {
 	struct dst_entry *dst;
-- 
2.53.0.345.g96ddfc5eaa-goog

Re: [PATCH net-next] tcp: move inet6_csk_update_pmtu() to tcp_ipv6.c

[Kuniyuki Iwashima]

On Mon, Feb 23, 2026 at 7:30 AM Eric Dumazet <edumazet@google.com> wrote:
>
> This function is only called from tcp_v6_mtu_reduced() and can be
> (auto)inlined by the compiler.
>
> Note that inet6_csk_route_socket() is no longer (auto)inlined,
> which is a good thing as it is slow path.
>
> $ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1
>
> add/remove: 0/2 grow/shrink: 2/0 up/down: 93/-129 (-36)
> Function                                     old     new   delta
> tcp_v6_mtu_reduced                           139     228     +89
> inet6_csk_route_socket                       486     490      +4
> __pfx_inet6_csk_update_pmtu                   16       -     -16
> inet6_csk_update_pmtu                        113       -    -113
> Total: Before=25076512, After=25076476, chg -0.00%
>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>

Re: [PATCH net-next] tcp: move inet6_csk_update_pmtu() to tcp_ipv6.c

[patchwork-bot+netdevbpf]

Hello:

This patch was applied to netdev/net-next.git (main)
by Jakub Kicinski <kuba@kernel.org>:

On Mon, 23 Feb 2026 15:30:47 +0000 you wrote:
> This function is only called from tcp_v6_mtu_reduced() and can be
> (auto)inlined by the compiler.
> 
> Note that inet6_csk_route_socket() is no longer (auto)inlined,
> which is a good thing as it is slow path.
> 
> $ scripts/bloat-o-meter -t vmlinux.0 vmlinux.1
> 
> [...]

Here is the summary with links:
  - [net-next] tcp: move inet6_csk_update_pmtu() to tcp_ipv6.c
    https://git.kernel.org/netdev/net-next/c/539a6cf0844d

You are awesome, thank you!
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