net/mptcp/ctrl.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /* Multipath TCP
  *
  * Copyright (c) 2019, Tessares SA.
  */

 #ifdef CONFIG_SYSCTL
 #include <linux/sysctl.h>
 #endif

 #include <net/net_namespace.h>
 #include <net/netns/generic.h>

 #include "protocol.h"
 #include "mib.h"

 #define MPTCP_SYSCTL_PATH "net/mptcp"

 static int mptcp_pernet_id;

 #ifdef CONFIG_SYSCTL
 static int mptcp_pm_type_max = __MPTCP_PM_TYPE_MAX;
 #endif

 struct mptcp_pernet {
 #ifdef CONFIG_SYSCTL
 	struct ctl_table_header *ctl_table_hdr;
 #endif

 	unsigned int add_addr_timeout;
 	unsigned int blackhole_timeout;
 	unsigned int close_timeout;
 	unsigned int stale_loss_cnt;
 	atomic_t active_disable_times;
 	unsigned long active_disable_stamp;
 	u8 mptcp_enabled;
 	u8 checksum_enabled;
 	u8 allow_join_initial_addr_port;
 	u8 pm_type;
 	char scheduler[MPTCP_SCHED_NAME_MAX];
 };

 static struct mptcp_pernet *mptcp_get_pernet(const struct net *net)
 {
 	return net_generic(net, mptcp_pernet_id);
 }

 int mptcp_is_enabled(const struct net *net)
 {
 	return mptcp_get_pernet(net)->mptcp_enabled;
 }

 unsigned int mptcp_get_add_addr_timeout(const struct net *net)
 {
 	return mptcp_get_pernet(net)->add_addr_timeout;
 }

 int mptcp_is_checksum_enabled(const struct net *net)
 {
 	return mptcp_get_pernet(net)->checksum_enabled;
 }

 int mptcp_allow_join_id0(const struct net *net)
 {
 	return mptcp_get_pernet(net)->allow_join_initial_addr_port;
 }

 unsigned int mptcp_stale_loss_cnt(const struct net *net)
 {
 	return mptcp_get_pernet(net)->stale_loss_cnt;
 }

 unsigned int mptcp_close_timeout(const struct sock *sk)
 {
 	if (sock_flag(sk, SOCK_DEAD))
 		return TCP_TIMEWAIT_LEN;
 	return mptcp_get_pernet(sock_net(sk))->close_timeout;
 }

 int mptcp_get_pm_type(const struct net *net)
 {
 	return mptcp_get_pernet(net)->pm_type;
 }

 const char *mptcp_get_scheduler(const struct net *net)
 {
 	return mptcp_get_pernet(net)->scheduler;
 }

 static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
 {
 	pernet->mptcp_enabled = 1;
 	pernet->add_addr_timeout = TCP_RTO_MAX;
 	pernet->blackhole_timeout = 3600;
 	atomic_set(&pernet->active_disable_times, 0);
 	pernet->close_timeout = TCP_TIMEWAIT_LEN;
 	pernet->checksum_enabled = 0;
 	pernet->allow_join_initial_addr_port = 1;
 	pernet->stale_loss_cnt = 4;
 	pernet->pm_type = MPTCP_PM_TYPE_KERNEL;
 	strscpy(pernet->scheduler, "default", sizeof(pernet->scheduler));
 }

 #ifdef CONFIG_SYSCTL
 static int mptcp_set_scheduler(const struct net *net, const char *name)
 {
 	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
 	struct mptcp_sched_ops *sched;
 	int ret = 0;

 	rcu_read_lock();
 	sched = mptcp_sched_find(name);
 	if (sched)
 		strscpy(pernet->scheduler, name, MPTCP_SCHED_NAME_MAX);
 	else
 		ret = -ENOENT;
 	rcu_read_unlock();

 	return ret;
 }

 static int proc_scheduler(const struct ctl_table *ctl, int write,
 			  void *buffer, size_t *lenp, loff_t *ppos)
 {
 	const struct net *net = current->nsproxy->net_ns;
 	char val[MPTCP_SCHED_NAME_MAX];
 	struct ctl_table tbl = {
 		.data = val,
 		.maxlen = MPTCP_SCHED_NAME_MAX,
 	};
 	int ret;

 	strscpy(val, mptcp_get_scheduler(net), MPTCP_SCHED_NAME_MAX);

 	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
 	if (write && ret == 0)
 		ret = mptcp_set_scheduler(net, val);

 	return ret;
 }

 static int proc_available_schedulers(const struct ctl_table *ctl,
 				     int write, void *buffer,
 				     size_t *lenp, loff_t *ppos)
 {
 	struct ctl_table tbl = { .maxlen = MPTCP_SCHED_BUF_MAX, };
 	int ret;

 	tbl.data = kmalloc(tbl.maxlen, GFP_USER);
 	if (!tbl.data)
 		return -ENOMEM;

 	mptcp_get_available_schedulers(tbl.data, MPTCP_SCHED_BUF_MAX);
 	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
 	kfree(tbl.data);

 	return ret;
 }

 static int proc_blackhole_detect_timeout(const struct ctl_table *table,
 					 int write, void *buffer, size_t *lenp,
 					 loff_t *ppos)
 {
 	struct mptcp_pernet *pernet = mptcp_get_pernet(current->nsproxy->net_ns);
 	int ret;

 	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
 	if (write && ret == 0)
 		atomic_set(&pernet->active_disable_times, 0);

 	return ret;
 }

 static struct ctl_table mptcp_sysctl_table[] = {
 	{
 		.procname = "enabled",
 		.maxlen = sizeof(u8),
 		.mode = 0644,
 		/* users with CAP_NET_ADMIN or root (not and) can change this
 		 * value, same as other sysctl or the 'net' tree.
 		 */
 		.proc_handler = proc_dou8vec_minmax,
 		.extra1       = SYSCTL_ZERO,
 		.extra2       = SYSCTL_ONE
 	},
 	{
 		.procname = "add_addr_timeout",
 		.maxlen = sizeof(unsigned int),
 		.mode = 0644,
 		.proc_handler = proc_dointvec_jiffies,
 	},
 	{
 		.procname = "checksum_enabled",
 		.maxlen = sizeof(u8),
 		.mode = 0644,
 		.proc_handler = proc_dou8vec_minmax,
 		.extra1       = SYSCTL_ZERO,
 		.extra2       = SYSCTL_ONE
 	},
 	{
 		.procname = "allow_join_initial_addr_port",
 		.maxlen = sizeof(u8),
 		.mode = 0644,
 		.proc_handler = proc_dou8vec_minmax,
 		.extra1       = SYSCTL_ZERO,
 		.extra2       = SYSCTL_ONE
 	},
 	{
 		.procname = "stale_loss_cnt",
 		.maxlen = sizeof(unsigned int),
 		.mode = 0644,
 		.proc_handler = proc_douintvec_minmax,
 	},
 	{
 		.procname = "pm_type",
 		.maxlen = sizeof(u8),
 		.mode = 0644,
 		.proc_handler = proc_dou8vec_minmax,
 		.extra1       = SYSCTL_ZERO,
 		.extra2       = &mptcp_pm_type_max
 	},
 	{
 		.procname = "scheduler",
 		.maxlen	= MPTCP_SCHED_NAME_MAX,
 		.mode = 0644,
 		.proc_handler = proc_scheduler,
 	},
 	{
 		.procname = "available_schedulers",
 		.maxlen	= MPTCP_SCHED_BUF_MAX,
 		.mode = 0644,
 		.proc_handler = proc_available_schedulers,
 	},
 	{
 		.procname = "close_timeout",
 		.maxlen = sizeof(unsigned int),
 		.mode = 0644,
 		.proc_handler = proc_dointvec_jiffies,
 	},
 	{
 		.procname = "blackhole_timeout",
 		.maxlen = sizeof(unsigned int),
 		.mode = 0644,
 		.proc_handler = proc_blackhole_detect_timeout,
 		.extra1 = SYSCTL_ZERO,
 	},
 };

 static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 {
 	struct ctl_table_header *hdr;
 	struct ctl_table *table;

 	table = mptcp_sysctl_table;
 	if (!net_eq(net, &init_net)) {
 		table = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);
 		if (!table)
 			goto err_alloc;
 	}

 	table[0].data = &pernet->mptcp_enabled;
 	table[1].data = &pernet->add_addr_timeout;
 	table[2].data = &pernet->checksum_enabled;
 	table[3].data = &pernet->allow_join_initial_addr_port;
 	table[4].data = &pernet->stale_loss_cnt;
 	table[5].data = &pernet->pm_type;
 	table[6].data = &pernet->scheduler;
 	/* table[7] is for available_schedulers which is read-only info */
 	table[8].data = &pernet->close_timeout;
 	table[9].data = &pernet->blackhole_timeout;

 	hdr = register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
 				     ARRAY_SIZE(mptcp_sysctl_table));
 	if (!hdr)
 		goto err_reg;

 	pernet->ctl_table_hdr = hdr;

 	return 0;

 err_reg:
 	if (!net_eq(net, &init_net))
 		kfree(table);
 err_alloc:
 	return -ENOMEM;
 }

 static void mptcp_pernet_del_table(struct mptcp_pernet *pernet)
 {
 	const struct ctl_table *table = pernet->ctl_table_hdr->ctl_table_arg;

 	unregister_net_sysctl_table(pernet->ctl_table_hdr);

 	kfree(table);
 }

 #else

 static int mptcp_pernet_new_table(struct net *net, struct mptcp_pernet *pernet)
 {
 	return 0;
 }

 static void mptcp_pernet_del_table(struct mptcp_pernet *pernet) {}

 #endif /* CONFIG_SYSCTL */

 /* The following code block is to deal with middle box issues with MPTCP,
  * similar to what is done with TFO.
  * The proposed solution is to disable active MPTCP globally when SYN+MPC are
  * dropped, while SYN without MPC aren't. In this case, active side MPTCP is
  * disabled globally for 1hr at first. Then if it happens again, it is disabled
  * for 2h, then 4h, 8h, ...
  * The timeout is reset back to 1hr when a successful active MPTCP connection is
  * fully established.
  */

 /* Disable active MPTCP and record current jiffies and active_disable_times */
 void mptcp_active_disable(struct sock *sk)
 {
 	struct net *net = sock_net(sk);
 	struct mptcp_pernet *pernet;

 	pernet = mptcp_get_pernet(net);

 	if (!READ_ONCE(pernet->blackhole_timeout))
 		return;

 	/* Paired with READ_ONCE() in mptcp_active_should_disable() */
 	WRITE_ONCE(pernet->active_disable_stamp, jiffies);

 	/* Paired with smp_rmb() in mptcp_active_should_disable().
 	 * We want pernet->active_disable_stamp to be updated first.
 	 */
 	smp_mb__before_atomic();
 	atomic_inc(&pernet->active_disable_times);

 	MPTCP_INC_STATS(net, MPTCP_MIB_BLACKHOLE);
 }

 /* Calculate timeout for MPTCP active disable
  * Return true if we are still in the active MPTCP disable period
  * Return false if timeout already expired and we should use active MPTCP
  */
 bool mptcp_active_should_disable(struct sock *ssk)
 {
 	struct net *net = sock_net(ssk);
 	unsigned int blackhole_timeout;
 	struct mptcp_pernet *pernet;
 	unsigned long timeout;
 	int disable_times;
 	int multiplier;

 	pernet = mptcp_get_pernet(net);
 	blackhole_timeout = READ_ONCE(pernet->blackhole_timeout);

 	if (!blackhole_timeout)
 		return false;

 	disable_times = atomic_read(&pernet->active_disable_times);
 	if (!disable_times)
 		return false;

 	/* Paired with smp_mb__before_atomic() in mptcp_active_disable() */
 	smp_rmb();

 	/* Limit timeout to max: 2^6 * initial timeout */
 	multiplier = 1 << min(disable_times - 1, 6);

 	/* Paired with the WRITE_ONCE() in mptcp_active_disable(). */
 	timeout = READ_ONCE(pernet->active_disable_stamp) +
 		  multiplier * blackhole_timeout * HZ;

 	return time_before(jiffies, timeout);
 }

 /* Enable active MPTCP and reset active_disable_times if needed */
 void mptcp_active_enable(struct sock *sk)
 {
 	struct mptcp_pernet *pernet = mptcp_get_pernet(sock_net(sk));

 	if (atomic_read(&pernet->active_disable_times)) {
 		struct dst_entry *dst = sk_dst_get(sk);

 		if (dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK))
 			atomic_set(&pernet->active_disable_times, 0);
 	}
 }

 /* Check the number of retransmissions, and fallback to TCP if needed */
 void mptcp_active_detect_blackhole(struct sock *ssk, bool expired)
 {
 	struct mptcp_subflow_context *subflow;
 	u32 timeouts;

 	if (!sk_is_mptcp(ssk))
 		return;

 	timeouts = inet_csk(ssk)->icsk_retransmits;
 	subflow = mptcp_subflow_ctx(ssk);

 	if (subflow->request_mptcp && ssk->sk_state == TCP_SYN_SENT) {
 		if (timeouts == 2 || (timeouts < 2 && expired)) {
 			MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEACTIVEDROP);
 			subflow->mpc_drop = 1;
 			mptcp_subflow_early_fallback(mptcp_sk(subflow->conn), subflow);
 		} else {
 			subflow->mpc_drop = 0;
 		}
 	}
 }

 static int __net_init mptcp_net_init(struct net *net)
 {
 	struct mptcp_pernet *pernet = mptcp_get_pernet(net);

 	mptcp_pernet_set_defaults(pernet);

 	return mptcp_pernet_new_table(net, pernet);
 }

 /* Note: the callback will only be called per extra netns */
 static void __net_exit mptcp_net_exit(struct net *net)
 {
 	struct mptcp_pernet *pernet = mptcp_get_pernet(net);

 	mptcp_pernet_del_table(pernet);
 }

 static struct pernet_operations mptcp_pernet_ops = {
 	.init = mptcp_net_init,
 	.exit = mptcp_net_exit,
 	.id = &mptcp_pernet_id,
 	.size = sizeof(struct mptcp_pernet),
 };

 void __init mptcp_init(void)
 {
 	mptcp_join_cookie_init();
 	mptcp_proto_init();

 	if (register_pernet_subsys(&mptcp_pernet_ops) < 0)
 		panic("Failed to register MPTCP pernet subsystem.\n");
 }

 #if IS_ENABLED(CONFIG_MPTCP_IPV6)
 int __init mptcpv6_init(void)
 {
 	int err;

 	err = mptcp_proto_v6_init();

 	return err;
 }
 #endif
	// SPDX-License-Identifier: GPL-2.0
	/* Multipath TCP
	*
	* Copyright (c) 2019, Tessares SA.
	*/

	#ifdef CONFIG_SYSCTL
	#include <linux/sysctl.h>
	#endif

	#include <net/net_namespace.h>
	#include <net/netns/generic.h>

	#include "protocol.h"
	#include "mib.h"

	#define MPTCP_SYSCTL_PATH "net/mptcp"

	static int mptcp_pernet_id;

	#ifdef CONFIG_SYSCTL
	static int mptcp_pm_type_max = __MPTCP_PM_TYPE_MAX;
	#endif

	struct mptcp_pernet {
	#ifdef CONFIG_SYSCTL
	struct ctl_table_header *ctl_table_hdr;
	#endif

	unsigned int add_addr_timeout;
	unsigned int blackhole_timeout;
	unsigned int close_timeout;
	unsigned int stale_loss_cnt;
	atomic_t active_disable_times;
	unsigned long active_disable_stamp;
	u8 mptcp_enabled;
	u8 checksum_enabled;
	u8 allow_join_initial_addr_port;
	u8 pm_type;
	char scheduler[MPTCP_SCHED_NAME_MAX];
	};

	static struct mptcp_pernet mptcp_get_pernet(const struct net net)
	{
	return net_generic(net, mptcp_pernet_id);
	}

	int mptcp_is_enabled(const struct net *net)
	{
	return mptcp_get_pernet(net)->mptcp_enabled;
	}

	unsigned int mptcp_get_add_addr_timeout(const struct net *net)
	{
	return mptcp_get_pernet(net)->add_addr_timeout;
	}

	int mptcp_is_checksum_enabled(const struct net *net)
	{
	return mptcp_get_pernet(net)->checksum_enabled;
	}

	int mptcp_allow_join_id0(const struct net *net)
	{
	return mptcp_get_pernet(net)->allow_join_initial_addr_port;
	}

	unsigned int mptcp_stale_loss_cnt(const struct net *net)
	{
	return mptcp_get_pernet(net)->stale_loss_cnt;
	}

	unsigned int mptcp_close_timeout(const struct sock *sk)
	{
	if (sock_flag(sk, SOCK_DEAD))
	return TCP_TIMEWAIT_LEN;
	return mptcp_get_pernet(sock_net(sk))->close_timeout;
	}

	int mptcp_get_pm_type(const struct net *net)
	{
	return mptcp_get_pernet(net)->pm_type;
	}

	const char mptcp_get_scheduler(const struct net net)
	{
	return mptcp_get_pernet(net)->scheduler;
	}

	static void mptcp_pernet_set_defaults(struct mptcp_pernet *pernet)
	{
	pernet->mptcp_enabled = 1;
	pernet->add_addr_timeout = TCP_RTO_MAX;
	pernet->blackhole_timeout = 3600;
	atomic_set(&pernet->active_disable_times, 0);
	pernet->close_timeout = TCP_TIMEWAIT_LEN;
	pernet->checksum_enabled = 0;
	pernet->allow_join_initial_addr_port = 1;
	pernet->stale_loss_cnt = 4;
	pernet->pm_type = MPTCP_PM_TYPE_KERNEL;
	strscpy(pernet->scheduler, "default", sizeof(pernet->scheduler));
	}

	#ifdef CONFIG_SYSCTL
	static int mptcp_set_scheduler(const struct net net, const char name)
	{
	struct mptcp_pernet *pernet = mptcp_get_pernet(net);
	struct mptcp_sched_ops *sched;
	int ret = 0;

	rcu_read_lock();
	sched = mptcp_sched_find(name);
	if (sched)
	strscpy(pernet->scheduler, name, MPTCP_SCHED_NAME_MAX);
	else
	ret = -ENOENT;
	rcu_read_unlock();

	return ret;
	}

	static int proc_scheduler(const struct ctl_table *ctl, int write,
	void buffer, size_t lenp, loff_t *ppos)
	{
	const struct net *net = current->nsproxy->net_ns;
	char val[MPTCP_SCHED_NAME_MAX];
	struct ctl_table tbl = {
	.data = val,
	.maxlen = MPTCP_SCHED_NAME_MAX,
	};
	int ret;

	strscpy(val, mptcp_get_scheduler(net), MPTCP_SCHED_NAME_MAX);

	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
	if (write && ret == 0)
	ret = mptcp_set_scheduler(net, val);

	return ret;
	}

	static int proc_available_schedulers(const struct ctl_table *ctl,
	int write, void *buffer,
	size_t lenp, loff_t ppos)
	{
	struct ctl_table tbl = { .maxlen = MPTCP_SCHED_BUF_MAX, };
	int ret;

	tbl.data = kmalloc(tbl.maxlen, GFP_USER);
	if (!tbl.data)
	return -ENOMEM;

	mptcp_get_available_schedulers(tbl.data, MPTCP_SCHED_BUF_MAX);
	ret = proc_dostring(&tbl, write, buffer, lenp, ppos);
	kfree(tbl.data);

	return ret;
	}

	static int proc_blackhole_detect_timeout(const struct ctl_table *table,
	int write, void buffer, size_t lenp,
	loff_t *ppos)
	{
	struct mptcp_pernet *pernet = mptcp_get_pernet(current->nsproxy->net_ns);
	int ret;

	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
	if (write && ret == 0)
	atomic_set(&pernet->active_disable_times, 0);

	return ret;
	}

	static struct ctl_table mptcp_sysctl_table[] = {
	{
	.procname = "enabled",
	.maxlen = sizeof(u8),
	.mode = 0644,
	/* users with CAP_NET_ADMIN or root (not and) can change this
	* value, same as other sysctl or the 'net' tree.
	*/
	.proc_handler = proc_dou8vec_minmax,
	.extra1 = SYSCTL_ZERO,
	.extra2 = SYSCTL_ONE
	},
	{
	.procname = "add_addr_timeout",
	.maxlen = sizeof(unsigned int),
	.mode = 0644,
	.proc_handler = proc_dointvec_jiffies,
	},
	{
	.procname = "checksum_enabled",
	.maxlen = sizeof(u8),
	.mode = 0644,
	.proc_handler = proc_dou8vec_minmax,
	.extra1 = SYSCTL_ZERO,
	.extra2 = SYSCTL_ONE
	},
	{
	.procname = "allow_join_initial_addr_port",
	.maxlen = sizeof(u8),
	.mode = 0644,
	.proc_handler = proc_dou8vec_minmax,
	.extra1 = SYSCTL_ZERO,
	.extra2 = SYSCTL_ONE
	},
	{
	.procname = "stale_loss_cnt",
	.maxlen = sizeof(unsigned int),
	.mode = 0644,
	.proc_handler = proc_douintvec_minmax,
	},
	{
	.procname = "pm_type",
	.maxlen = sizeof(u8),
	.mode = 0644,
	.proc_handler = proc_dou8vec_minmax,
	.extra1 = SYSCTL_ZERO,
	.extra2 = &mptcp_pm_type_max
	},
	{
	.procname = "scheduler",
	.maxlen = MPTCP_SCHED_NAME_MAX,
	.mode = 0644,
	.proc_handler = proc_scheduler,
	},
	{
	.procname = "available_schedulers",
	.maxlen = MPTCP_SCHED_BUF_MAX,
	.mode = 0644,
	.proc_handler = proc_available_schedulers,
	},
	{
	.procname = "close_timeout",
	.maxlen = sizeof(unsigned int),
	.mode = 0644,
	.proc_handler = proc_dointvec_jiffies,
	},
	{
	.procname = "blackhole_timeout",
	.maxlen = sizeof(unsigned int),
	.mode = 0644,
	.proc_handler = proc_blackhole_detect_timeout,
	.extra1 = SYSCTL_ZERO,
	},
	};

	static int mptcp_pernet_new_table(struct net net, struct mptcp_pernet pernet)
	{
	struct ctl_table_header *hdr;
	struct ctl_table *table;

	table = mptcp_sysctl_table;
	if (!net_eq(net, &init_net)) {
	table = kmemdup(table, sizeof(mptcp_sysctl_table), GFP_KERNEL);
	if (!table)
	goto err_alloc;
	}

	table[0].data = &pernet->mptcp_enabled;
	table[1].data = &pernet->add_addr_timeout;
	table[2].data = &pernet->checksum_enabled;
	table[3].data = &pernet->allow_join_initial_addr_port;
	table[4].data = &pernet->stale_loss_cnt;
	table[5].data = &pernet->pm_type;
	table[6].data = &pernet->scheduler;
	/* table[7] is for available_schedulers which is read-only info */
	table[8].data = &pernet->close_timeout;
	table[9].data = &pernet->blackhole_timeout;

	hdr = register_net_sysctl_sz(net, MPTCP_SYSCTL_PATH, table,
	ARRAY_SIZE(mptcp_sysctl_table));
	if (!hdr)
	goto err_reg;

	pernet->ctl_table_hdr = hdr;

	return 0;

	err_reg:
	if (!net_eq(net, &init_net))
	kfree(table);
	err_alloc:
	return -ENOMEM;
	}

	static void mptcp_pernet_del_table(struct mptcp_pernet *pernet)
	{
	const struct ctl_table *table = pernet->ctl_table_hdr->ctl_table_arg;

	unregister_net_sysctl_table(pernet->ctl_table_hdr);

	kfree(table);
	}

	#else

	static int mptcp_pernet_new_table(struct net net, struct mptcp_pernet pernet)
	{
	return 0;
	}

	static void mptcp_pernet_del_table(struct mptcp_pernet *pernet) {}

	#endif /* CONFIG_SYSCTL */

	/* The following code block is to deal with middle box issues with MPTCP,
	* similar to what is done with TFO.
	* The proposed solution is to disable active MPTCP globally when SYN+MPC are
	* dropped, while SYN without MPC aren't. In this case, active side MPTCP is
	* disabled globally for 1hr at first. Then if it happens again, it is disabled
	* for 2h, then 4h, 8h, ...
	* The timeout is reset back to 1hr when a successful active MPTCP connection is
	* fully established.
	*/

	/* Disable active MPTCP and record current jiffies and active_disable_times */
	void mptcp_active_disable(struct sock *sk)
	{
	struct net *net = sock_net(sk);
	struct mptcp_pernet *pernet;

	pernet = mptcp_get_pernet(net);

	if (!READ_ONCE(pernet->blackhole_timeout))
	return;

	/* Paired with READ_ONCE() in mptcp_active_should_disable() */
	WRITE_ONCE(pernet->active_disable_stamp, jiffies);

	/* Paired with smp_rmb() in mptcp_active_should_disable().
	* We want pernet->active_disable_stamp to be updated first.
	*/
	smp_mb__before_atomic();
	atomic_inc(&pernet->active_disable_times);

	MPTCP_INC_STATS(net, MPTCP_MIB_BLACKHOLE);
	}

	/* Calculate timeout for MPTCP active disable
	* Return true if we are still in the active MPTCP disable period
	* Return false if timeout already expired and we should use active MPTCP
	*/
	bool mptcp_active_should_disable(struct sock *ssk)
	{
	struct net *net = sock_net(ssk);
	unsigned int blackhole_timeout;
	struct mptcp_pernet *pernet;
	unsigned long timeout;
	int disable_times;
	int multiplier;

	pernet = mptcp_get_pernet(net);
	blackhole_timeout = READ_ONCE(pernet->blackhole_timeout);

	if (!blackhole_timeout)
	return false;

	disable_times = atomic_read(&pernet->active_disable_times);
	if (!disable_times)
	return false;

	/* Paired with smp_mb__before_atomic() in mptcp_active_disable() */
	smp_rmb();

	/* Limit timeout to max: 2^6 * initial timeout */
	multiplier = 1 << min(disable_times - 1, 6);

	/* Paired with the WRITE_ONCE() in mptcp_active_disable(). */
	timeout = READ_ONCE(pernet->active_disable_stamp) +
	multiplier * blackhole_timeout * HZ;

	return time_before(jiffies, timeout);
	}

	/* Enable active MPTCP and reset active_disable_times if needed */
	void mptcp_active_enable(struct sock *sk)
	{
	struct mptcp_pernet *pernet = mptcp_get_pernet(sock_net(sk));

	if (atomic_read(&pernet->active_disable_times)) {
	struct dst_entry *dst = sk_dst_get(sk);

	if (dst && dst->dev && (dst->dev->flags & IFF_LOOPBACK))
	atomic_set(&pernet->active_disable_times, 0);
	}
	}

	/* Check the number of retransmissions, and fallback to TCP if needed */
	void mptcp_active_detect_blackhole(struct sock *ssk, bool expired)
	{
	struct mptcp_subflow_context *subflow;
	u32 timeouts;

	if (!sk_is_mptcp(ssk))
	return;

	timeouts = inet_csk(ssk)->icsk_retransmits;
	subflow = mptcp_subflow_ctx(ssk);

	if (subflow->request_mptcp && ssk->sk_state == TCP_SYN_SENT) {
	if (timeouts == 2 \|\| (timeouts < 2 && expired)) {
	MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPCAPABLEACTIVEDROP);
	subflow->mpc_drop = 1;
	mptcp_subflow_early_fallback(mptcp_sk(subflow->conn), subflow);
	} else {
	subflow->mpc_drop = 0;
	}
	}
	}

	static int __net_init mptcp_net_init(struct net *net)
	{
	struct mptcp_pernet *pernet = mptcp_get_pernet(net);

	mptcp_pernet_set_defaults(pernet);

	return mptcp_pernet_new_table(net, pernet);
	}

	/* Note: the callback will only be called per extra netns */
	static void __net_exit mptcp_net_exit(struct net *net)
	{
	struct mptcp_pernet *pernet = mptcp_get_pernet(net);

	mptcp_pernet_del_table(pernet);
	}

	static struct pernet_operations mptcp_pernet_ops = {
	.init = mptcp_net_init,
	.exit = mptcp_net_exit,
	.id = &mptcp_pernet_id,
	.size = sizeof(struct mptcp_pernet),
	};

	void __init mptcp_init(void)
	{
	mptcp_join_cookie_init();
	mptcp_proto_init();

	if (register_pernet_subsys(&mptcp_pernet_ops) < 0)
	panic("Failed to register MPTCP pernet subsystem.\n");
	}

	#if IS_ENABLED(CONFIG_MPTCP_IPV6)
	int __init mptcpv6_init(void)
	{
	int err;

	err = mptcp_proto_v6_init();

	return err;
	}
	#endif