Merge branch 'tcp-rework-tcp_v-4-6-_send_check'

Eric Dumazet says:

====================
tcp: rework tcp_v{4,6}_send_check()

tcp_v{4,6}_send_check() are only called from __tcp_transmit_skb()

They currently are in different files (tcp_ipv4.c and tcp_ipv6.c)
thus out of line.

This series move them close to their caller so that compiler
can inline them.

For all patches in the series:

$ scripts/bloat-o-meter -t vmlinux.0 vmlinux.3
add/remove: 0/2 grow/shrink: 1/3 up/down: 102/-178 (-76)
Function                                     old     new   delta
__tcp_transmit_skb                          3321    3423    +102
tcp_v4_send_check                            136     132      -4
__tcp_v4_send_check                          130     121      -9
mptcp_subflow_init                           777     763     -14
__pfx_tcp_v6_send_check                       16       -     -16
tcp_v6_send_check                            135       -    -135
Total: Before=25143100, After=25143024, chg -0.00%
====================

Link: https://patch.msgid.link/20260223100729.3761597-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

7 files changed, 33 insertions, 39 deletions

diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h
index ecb362025c4e..bbc9355871c7 100644
--- a/include/net/inet_connection_sock.h
+++ b/include/net/inet_connection_sock.h
@@ -34,7 +34,7 @@ struct tcp_congestion_ops;
  */
 struct inet_connection_sock_af_ops {
 	int	    (*queue_xmit)(struct sock *sk, struct sk_buff *skb, struct flowi *fl);
-	void	    (*send_check)(struct sock *sk, struct sk_buff *skb);
+	u16	    net_header_len;
 	int	    (*rebuild_header)(struct sock *sk);
 	void	    (*sk_rx_dst_set)(struct sock *sk, const struct sk_buff *skb);
 	int	    (*conn_request)(struct sock *sk, struct sk_buff *skb);
@@ -43,7 +43,6 @@ struct inet_connection_sock_af_ops {
 				      struct dst_entry *dst,
 				      struct request_sock *req_unhash,
 				      bool *own_req);
-	u16	    net_header_len;
 	int	    (*setsockopt)(struct sock *sk, int level, int optname,
 				  sockptr_t optval, unsigned int optlen);
 	int	    (*getsockopt)(struct sock *sk, int level, int optname,
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 40e72b9cb85f..dfcd38089f11 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -531,7 +531,6 @@ u16 tcp_get_syncookie_mss(struct request_sock_ops *rsk_ops,
  *	TCP v4 functions exported for the inet6 API
  */
 
-void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
 void tcp_v4_mtu_reduced(struct sock *sk);
 void tcp_req_err(struct sock *sk, u32 seq, bool abort);
 void tcp_ld_RTO_revert(struct sock *sk, u32 seq);
@@ -1132,7 +1131,6 @@ static inline int tcp_v6_sdif(const struct sk_buff *skb)
 
 extern const struct inet_connection_sock_af_ops ipv6_specific;
 
-INDIRECT_CALLABLE_DECLARE(void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb));
 INDIRECT_CALLABLE_DECLARE(int tcp_v6_rcv(struct sk_buff *skb));
 void tcp_v6_early_demux(struct sk_buff *skb);
 
@@ -2382,7 +2380,15 @@ void tcp_gro_complete(struct sk_buff *skb);
 static inline void tcp_gro_complete(struct sk_buff *skb) { }
 #endif
 
-void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
+static inline void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr,
+				       __be32 daddr)
+{
+	struct tcphdr *th = tcp_hdr(skb);
+
+	th->check = ~tcp_v4_check(skb->len, saddr, daddr, 0);
+	skb->csum_start = skb_transport_header(skb) - skb->head;
+	skb->csum_offset = offsetof(struct tcphdr, check);
+}
 
 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
 {
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 6264fc0b2be5..bd613e401d48 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -661,24 +661,6 @@ out:
 	return 0;
 }
 
-void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr)
-{
-	struct tcphdr *th = tcp_hdr(skb);
-
-	th->check = ~tcp_v4_check(skb->len, saddr, daddr, 0);
-	skb->csum_start = skb_transport_header(skb) - skb->head;
-	skb->csum_offset = offsetof(struct tcphdr, check);
-}
-
-/* This routine computes an IPv4 TCP checksum. */
-void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
-{
-	const struct inet_sock *inet = inet_sk(sk);
-
-	__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
-}
-EXPORT_IPV6_MOD(tcp_v4_send_check);
-
 #define REPLY_OPTIONS_LEN      (MAX_TCP_OPTION_SPACE / sizeof(__be32))
 
 static bool tcp_v4_ao_sign_reset(const struct sock *sk, struct sk_buff *skb,
@@ -2423,7 +2405,6 @@ EXPORT_IPV6_MOD(inet_sk_rx_dst_set);
 
 const struct inet_connection_sock_af_ops ipv4_specific = {
 	.queue_xmit	   = ip_queue_xmit,
-	.send_check	   = tcp_v4_send_check,
 	.rebuild_header	   = inet_sk_rebuild_header,
 	.sk_rx_dst_set	   = inet_sk_rx_dst_set,
 	.conn_request	   = tcp_v4_conn_request,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 326b58ff1118..1ef419c66a0e 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -1496,7 +1496,23 @@ static void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb)
 
 INDIRECT_CALLABLE_DECLARE(int ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
 INDIRECT_CALLABLE_DECLARE(int inet6_csk_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl));
-INDIRECT_CALLABLE_DECLARE(void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb));
+
+/* This routine computes an IPv4 TCP checksum. */
+static void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb)
+{
+	const struct inet_sock *inet = inet_sk(sk);
+
+	__tcp_v4_send_check(skb, inet->inet_saddr, inet->inet_daddr);
+}
+
+#if IS_ENABLED(CONFIG_IPV6)
+#include <net/ip6_checksum.h>
+
+static void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
+{
+	__tcp_v6_send_check(skb, &sk->sk_v6_rcv_saddr, &sk->sk_v6_daddr);
+}
+#endif
 
 /* This routine actually transmits TCP packets queued in by
  * tcp_do_sendmsg().  This is used by both the initial
@@ -1659,9 +1675,12 @@ static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb,
 	/* BPF prog is the last one writing header option */
 	bpf_skops_write_hdr_opt(sk, skb, NULL, NULL, 0, &opts);
 
-	INDIRECT_CALL_INET(icsk->icsk_af_ops->send_check,
-			   tcp_v6_send_check, tcp_v4_send_check,
-			   sk, skb);
+#if IS_ENABLED(CONFIG_IPV6)
+	if (likely(icsk->icsk_af_ops->net_header_len == sizeof(struct ipv6hdr)))
+		tcp_v6_send_check(sk, skb);
+	else
+#endif
+		tcp_v4_send_check(sk, skb);
 
 	if (likely(tcb->tcp_flags & TCPHDR_ACK))
 		tcp_event_ack_sent(sk, rcv_nxt);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index d10487b4e5bf..f17da56b449e 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -2015,14 +2015,8 @@ static struct timewait_sock_ops tcp6_timewait_sock_ops = {
 	.twsk_obj_size	= sizeof(struct tcp6_timewait_sock),
 };
 
-INDIRECT_CALLABLE_SCOPE void tcp_v6_send_check(struct sock *sk, struct sk_buff *skb)
-{
-	__tcp_v6_send_check(skb, &sk->sk_v6_rcv_saddr, &sk->sk_v6_daddr);
-}
-
 const struct inet_connection_sock_af_ops ipv6_specific = {
 	.queue_xmit	   = inet6_csk_xmit,
-	.send_check	   = tcp_v6_send_check,
 	.rebuild_header	   = inet6_sk_rebuild_header,
 	.sk_rx_dst_set	   = inet6_sk_rx_dst_set,
 	.conn_request	   = tcp_v6_conn_request,
@@ -2054,7 +2048,6 @@ static const struct tcp_sock_af_ops tcp_sock_ipv6_specific = {
  */
 static const struct inet_connection_sock_af_ops ipv6_mapped = {
 	.queue_xmit	   = ip_queue_xmit,
-	.send_check	   = tcp_v4_send_check,
 	.rebuild_header	   = inet_sk_rebuild_header,
 	.sk_rx_dst_set	   = inet_sk_rx_dst_set,
 	.conn_request	   = tcp_v6_conn_request,
diff --git a/net/mptcp/subflow.c b/net/mptcp/subflow.c
index f66129f1e649..dd79c5b37a6b 100644
--- a/net/mptcp/subflow.c
+++ b/net/mptcp/subflow.c
@@ -2190,7 +2190,6 @@ void __init mptcp_subflow_init(void)
 
 	subflow_v6m_specific = subflow_v6_specific;
 	subflow_v6m_specific.queue_xmit = ipv4_specific.queue_xmit;
-	subflow_v6m_specific.send_check = ipv4_specific.send_check;
 	subflow_v6m_specific.net_header_len = ipv4_specific.net_header_len;
 	subflow_v6m_specific.mtu_reduced = ipv4_specific.mtu_reduced;
 	subflow_v6m_specific.rebuild_header = subflow_rebuild_header;
diff --git a/net/tls/tls_device_fallback.c b/net/tls/tls_device_fallback.c
index 03d508a45aae..de7d86bdd7ec 100644
--- a/net/tls/tls_device_fallback.c
+++ b/net/tls/tls_device_fallback.c
@@ -149,9 +149,6 @@ static int tls_enc_records(struct aead_request *aead_req,
 	return rc;
 }
 
-/* Can't use icsk->icsk_af_ops->send_check here because the ip addresses
- * might have been changed by NAT.
- */
 static void update_chksum(struct sk_buff *skb, int headln)
 {
 	struct tcphdr *th = tcp_hdr(skb);