ipv4: add ip_sock_set_tos

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

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

drivers/nvme/host/tcp.c

···
 {
 	struct nvme_tcp_ctrl *ctrl = to_tcp_ctrl(nctrl);
 	struct nvme_tcp_queue *queue = &ctrl->queues[qid];
-	int ret, opt, rcv_pdu_size;
+	int ret, rcv_pdu_size;
 
 	queue->ctrl = ctrl;
 	INIT_LIST_HEAD(&queue->send_list);
···
 		sock_set_priority(queue->sock->sk, so_priority);
 
 	/* Set socket type of service */
-	if (nctrl->opts->tos >= 0) {
-		opt = nctrl->opts->tos;
-		ret = kernel_setsockopt(queue->sock, SOL_IP, IP_TOS,
-				(char *)&opt, sizeof(opt));
-		if (ret) {
-			dev_err(nctrl->device,
-				"failed to set IP_TOS sock opt %d\n", ret);
-			goto err_sock;
-		}
-	}
+	if (nctrl->opts->tos >= 0)
+		ip_sock_set_tos(queue->sock->sk, nctrl->opts->tos);
 
 	queue->sock->sk->sk_allocation = GFP_ATOMIC;
 	nvme_tcp_set_queue_io_cpu(queue);

drivers/nvme/target/tcp.c

···
 		sock_set_priority(sock->sk, so_priority);
 
 	/* Set socket type of service */
-	if (inet->rcv_tos > 0) {
-		int tos = inet->rcv_tos;
-
-		ret = kernel_setsockopt(sock, SOL_IP, IP_TOS,
-				(char *)&tos, sizeof(tos));
-		if (ret)
-			return ret;
-	}
+	if (inet->rcv_tos > 0)
+		ip_sock_set_tos(sock->sk, inet->rcv_tos);
 
 	write_lock_bh(&sock->sk->sk_callback_lock);
 	sock->sk->sk_user_data = queue;

include/net/ip.h

···
 	return likely(mtu >= IPV4_MIN_MTU);
 }
 
+void ip_sock_set_tos(struct sock *sk, int val);
+
 #endif	/* _IP_H */

net/ipv4/ip_sockglue.c

···
 	return err;
 }
 
+static void __ip_sock_set_tos(struct sock *sk, int val)
+{
+	if (sk->sk_type == SOCK_STREAM) {
+		val &= ~INET_ECN_MASK;
+		val |= inet_sk(sk)->tos & INET_ECN_MASK;
+	}
+	if (inet_sk(sk)->tos != val) {
+		inet_sk(sk)->tos = val;
+		sk->sk_priority = rt_tos2priority(val);
+		sk_dst_reset(sk);
+	}
+}
+
+void ip_sock_set_tos(struct sock *sk, int val)
+{
+	lock_sock(sk);
+	__ip_sock_set_tos(sk, val);
+	release_sock(sk);
+}
+EXPORT_SYMBOL(ip_sock_set_tos);
 
 /*
  *	Socket option code for IP. This is the end of the line after any
···
 			inet->cmsg_flags &= ~IP_CMSG_RECVFRAGSIZE;
 		break;
 	case IP_TOS:	/* This sets both TOS and Precedence */
-		if (sk->sk_type == SOCK_STREAM) {
-			val &= ~INET_ECN_MASK;
-			val |= inet->tos & INET_ECN_MASK;
-		}
-		if (inet->tos != val) {
-			inet->tos = val;
-			sk->sk_priority = rt_tos2priority(val);
-			sk_dst_reset(sk);
-		}
+		__ip_sock_set_tos(sk, val);
 		break;
 	case IP_TTL:
 		if (optlen < 1)