From: Christoph Hellwig <hch@lst.de>
Date: Thu, 28 May 2020 07:12:21 +0200
Subject: tcp: add tcp_sock_set_syncnt
Patch-mainline: v5.8-rc1
Git-commit: 557eadfcc5ee8f8fa98a795e05ed21db58a65db5
References: bsc#1177028

Add a helper to directly set the TCP_SYNCNT sockopt from kernel space
without going through a fake uaccess.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Gary Lin <glin@suse.com>
---
 drivers/nvme/host/tcp.c |    9 +--------
 include/linux/tcp.h     |    1 +
 net/ipv4/tcp.c          |   12 ++++++++++++
 3 files changed, 14 insertions(+), 8 deletions(-)

--- a/drivers/nvme/host/tcp.c
+++ b/drivers/nvme/host/tcp.c
@@ -1363,14 +1363,7 @@ static int nvme_tcp_alloc_queue(struct n
 	}
 
 	/* Single syn retry */
-	opt = 1;
-	ret = kernel_setsockopt(queue->sock, IPPROTO_TCP, TCP_SYNCNT,
-			(char *)&opt, sizeof(opt));
-	if (ret) {
-		dev_err(nctrl->device,
-			"failed to set TCP_SYNCNT sock opt %d\n", ret);
-		goto err_sock;
-	}
+	tcp_sock_set_syncnt(queue->sock->sk, 1);
 
 	/* Set TCP no delay */
 	tcp_sock_set_nodelay(queue->sock->sk);
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -490,5 +490,6 @@ int tcp_skb_shift(struct sk_buff *to, st
 void tcp_sock_set_cork(struct sock *sk, bool on);
 void tcp_sock_set_nodelay(struct sock *sk);
 void tcp_sock_set_quickack(struct sock *sk, int val);
+int tcp_sock_set_syncnt(struct sock *sk, int val);
 
 #endif	/* _LINUX_TCP_H */
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2875,6 +2875,18 @@ void tcp_sock_set_quickack(struct sock *
 }
 EXPORT_SYMBOL(tcp_sock_set_quickack);
 
+int tcp_sock_set_syncnt(struct sock *sk, int val)
+{
+	if (val < 1 || val > MAX_TCP_SYNCNT)
+		return -EINVAL;
+
+	lock_sock(sk);
+	inet_csk(sk)->icsk_syn_retries = val;
+	release_sock(sk);
+	return 0;
+}
+EXPORT_SYMBOL(tcp_sock_set_syncnt);
+
 /*
  *	Socket option code for TCP.
  */