[PATCH net-next 2/4] tuntap: Accept tuntap maximum number of queues as sysctl

@@ -71,6 +71,7 @@
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <linux/seq_file.h>
+#include <linux/sysctl.h>
 #include <linux/uio.h>
 
 #include <asm/uaccess.h>

@@ -117,10 +118,16 @@ struct tap_filter {
  * the netdevice to be fit in one page. So we can make sure the success of
  * memory allocation. TODO: increase the limit. */
 #define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES
+#define MIN_TAP_QUEUES 1
 #define MAX_TAP_FLOWS  4096
 
 #define TUN_FLOW_EXPIRE (3 * HZ)
 
+static struct ctl_table_header *tun_sysctl_header;
+static int tun_queues = MAX_TAP_QUEUES;
+static int min_queues = MIN_TAP_QUEUES;
+static int max_queues = MAX_TAP_QUEUES;
+
 /* A tun_file connects an open character device to a tuntap netdevice. It
  * also contains all socket related structures (except sock_fprog and tap_filter)
  * to serve as one transmit queue for tuntap device. The sock_fprog and

@@ -197,6 +204,19 @@ struct tun_struct {
 	u32 flow_count;
 };
 
+static struct ctl_table tun_ctl_table[] = {
+	{
+		.procname       = "tun_max_queues",
+		.data           = &tun_queues,
+		.maxlen         = sizeof(int),
+		.mode           = 0644,
+		.proc_handler   = proc_dointvec_minmax,
+		.extra1         = &min_queues,
+		.extra2         = &max_queues
+	},
+	{  }
+};
+
 static inline u32 tun_hashfn(u32 rxhash)
 {
 	return rxhash & 0x3ff;

@@ -547,7 +567,7 @@ static int tun_attach(struct tun_struct *tun, struct file *file, bool skip_filte
 
 	err = -E2BIG;
 	if (!tfile->detached &&
-	    tun->numqueues + tun->numdisabled == MAX_TAP_QUEUES)
+	    tun->numqueues + tun->numdisabled == tun_queues)
 		goto out;
 
 	err = 0;

@@ -1624,7 +1644,7 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
 		char *name;
 		unsigned long flags = 0;
 		int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?
-			     MAX_TAP_QUEUES : 1;
+			     tun_queues : 1;
 
 		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
 			return -EPERM;

@@ -2335,6 +2355,13 @@ static int __init tun_init(void)
 	pr_info("%s, %s\n", DRV_DESCRIPTION, DRV_VERSION);
 	pr_info("%s\n", DRV_COPYRIGHT);
 
+	tun_sysctl_header = register_net_sysctl(&init_net, "net/tuntap",
+						tun_ctl_table);
+
+	if (!tun_sysctl_header)
+		pr_err("Can't register tun_ctl_table. Tun device queue"
+		       "setting to default value : %d queues.\n", tun_queues);
+
 	ret = rtnl_link_register(&tun_link_ops);
 	if (ret) {
 		pr_err("Can't register link_ops\n");

@@ -2357,6 +2384,8 @@ static void tun_cleanup(void)
 {
 	misc_deregister(&tun_miscdev);
 	rtnl_link_unregister(&tun_link_ops);
+	if (tun_sysctl_header)
+		unregister_net_sysctl_table(tun_sysctl_header);
 }
 
 /* Get an underlying socket object from tun file.  Returns error unless file is