net: add sock_set_reuseaddr

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

For this the iscsi target now has to formally depend on inet to avoid
a mostly theoretical compile failure. For actual operation it already
did depend on having ipv4 or ipv6 support.

Signed-off-by: Christoph Hellwig <[e-mail]>
Acked-by: Sagi Grimberg <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/infiniband/sw/siw/siw_cm.c

···
 static int kernel_bindconnect(struct socket *s, struct sockaddr *laddr,
 			      struct sockaddr *raddr)
 {
-	int rv, flags = 0, s_val = 1;
+	int rv, flags = 0;
 	size_t size = laddr->sa_family == AF_INET ?
 		sizeof(struct sockaddr_in) : sizeof(struct sockaddr_in6);
 
 	/*
 	 * Make address available again asap.
 	 */
-	rv = kernel_setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *)&s_val,
-			       sizeof(s_val));
-	if (rv < 0)
-		return rv;
+	sock_set_reuseaddr(s->sk);
 
 	rv = s->ops->bind(s, laddr, size);
 	if (rv < 0)
···
 	struct siw_cep *cep = NULL;
 	struct siw_device *sdev = to_siw_dev(id->device);
 	int addr_family = id->local_addr.ss_family;
-	int rv = 0, s_val;
+	int rv = 0;
 
 	if (addr_family != AF_INET && addr_family != AF_INET6)
 		return -EAFNOSUPPORT;
···
 	/*
 	 * Allow binding local port when still in TIME_WAIT from last close.
 	 */
-	s_val = 1;
-	rv = kernel_setsockopt(s, SOL_SOCKET, SO_REUSEADDR, (char *)&s_val,
-			       sizeof(s_val));
-	if (rv) {
-		siw_dbg(id->device, "setsockopt error: %d\n", rv);
-		goto error;
-	}
+	sock_set_reuseaddr(s->sk);
+
 	if (addr_family == AF_INET) {
 		struct sockaddr_in *laddr = &to_sockaddr_in(id->local_addr);
 

drivers/nvme/target/tcp.c

···
 	port->sock->sk->sk_user_data = port;
 	port->data_ready = port->sock->sk->sk_data_ready;
 	port->sock->sk->sk_data_ready = nvmet_tcp_listen_data_ready;
+	sock_set_reuseaddr(port->sock->sk);
 
 	opt = 1;
 	ret = kernel_setsockopt(port->sock, IPPROTO_TCP,
 			TCP_NODELAY, (char *)&opt, sizeof(opt));
 	if (ret) {
 		pr_err("failed to set TCP_NODELAY sock opt %d\n", ret);
-		goto err_sock;
-	}
-
-	ret = kernel_setsockopt(port->sock, SOL_SOCKET, SO_REUSEADDR,
-			(char *)&opt, sizeof(opt));
-	if (ret) {
-		pr_err("failed to set SO_REUSEADDR sock opt %d\n", ret);
 		goto err_sock;
 	}
 

drivers/target/iscsi/Kconfig

···
 # SPDX-License-Identifier: GPL-2.0-only
 config ISCSI_TARGET
 	tristate "Linux-iSCSI.org iSCSI Target Mode Stack"
-	depends on NET
+	depends on INET
 	select CRYPTO
 	select CRYPTO_CRC32C
 	select CRYPTO_CRC32C_INTEL if X86

drivers/target/iscsi/iscsi_target_login.c

···
 		}
 	}
 
-	/* FIXME: Someone please explain why this is endian-safe */
-	ret = kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
-			(char *)&opt, sizeof(opt));
-	if (ret < 0) {
-		pr_err("kernel_setsockopt() for SO_REUSEADDR"
-			" failed\n");
-		goto fail;
-	}
+	sock_set_reuseaddr(sock->sk);
 
 	ret = kernel_setsockopt(sock, IPPROTO_IP, IP_FREEBIND,
 			(char *)&opt, sizeof(opt));

fs/dlm/lowcomms.c

···
 	kernel_setsockopt(sock, SOL_TCP, TCP_NODELAY, (char *)&one,
 			  sizeof(one));
 
-	result = kernel_setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
-				   (char *)&one, sizeof(one));
+	sock_set_reuseaddr(sock->sk);
 
-	if (result < 0) {
-		log_print("Failed to set SO_REUSEADDR on socket: %d", result);
-	}
 	write_lock_bh(&sock->sk->sk_callback_lock);
 	sock->sk->sk_user_data = con;
 	save_listen_callbacks(sock);

include/net/sock.h

···
 
 void sock_def_readable(struct sock *sk);
 
+void sock_set_reuseaddr(struct sock *sk);
+
 #endif	/* _SOCK_H */

net/core/sock.c

···
 }
 EXPORT_SYMBOL(sk_mc_loop);
 
+void sock_set_reuseaddr(struct sock *sk)
+{
+	lock_sock(sk);
+	sk->sk_reuse = SK_CAN_REUSE;
+	release_sock(sk);
+}
+EXPORT_SYMBOL(sock_set_reuseaddr);
+
 /*
  *	This is meant for all protocols to use and covers goings on
  *	at the socket level. Everything here is generic.