ip6_flowlabel.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	ip6_flowlabel.c		IPv6 flowlabel manager.
 *
 *	Authors:	Alexey Kuznetsov, <[email protected]>
 */

#include <linux/capability.h>
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/in6.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/pid_namespace.h>
#include <linux/jump_label_ratelimit.h>

#include <net/net_namespace.h>
#include <net/sock.h>

#include <net/ipv6.h>
#include <net/rawv6.h>
#include <net/transp_v6.h>

#include <linux/uaccess.h>

#define FL_MIN_LINGER	6	/* Minimal linger. It is set to 6sec specified
				   in old IPv6 RFC. Well, it was reasonable value.
				 */
#define FL_MAX_LINGER	150	/* Maximal linger timeout */

/* FL hash table */

#define FL_MAX_PER_SOCK	32
#define FL_MAX_SIZE	4096
#define FL_HASH_MASK	255
#define FL_HASH(l)	(ntohl(l)&FL_HASH_MASK)

static atomic_t fl_size = ATOMIC_INIT(0);
static struct ip6_flowlabel __rcu *fl_ht[FL_HASH_MASK+1];

static void ip6_fl_gc(struct timer_list *unused);
static DEFINE_TIMER(ip6_fl_gc_timer, ip6_fl_gc);

/* FL hash table lock: it protects only of GC */

static DEFINE_SPINLOCK(ip6_fl_lock);

/* Big socket sock */

static DEFINE_SPINLOCK(ip6_sk_fl_lock);

DEFINE_STATIC_KEY_DEFERRED_FALSE(ipv6_flowlabel_exclusive, HZ);
EXPORT_SYMBOL(ipv6_flowlabel_exclusive);

#define for_each_fl_rcu(hash, fl)				\
	for (fl = rcu_dereference(fl_ht[(hash)]);		\
	     fl != NULL;					\
	     fl = rcu_dereference(fl->next))
#define for_each_fl_continue_rcu(fl)				\
	for (fl = rcu_dereference(fl->next);			\
	     fl != NULL;					\
	     fl = rcu_dereference(fl->next))

#define for_each_sk_fl_rcu(sk, sfl)				\
	for (sfl = rcu_dereference(inet_sk(sk)->ipv6_fl_list);	\
	     sfl != NULL;					\
	     sfl = rcu_dereference(sfl->next))

static inline struct ip6_flowlabel *__fl_lookup(struct net *net, __be32 label)
{
	struct ip6_flowlabel *fl;

	for_each_fl_rcu(FL_HASH(label), fl) {
		if (fl->label == label && net_eq(fl->fl_net, net))
			return fl;
	}
	return NULL;
}

static struct ip6_flowlabel *fl_lookup(struct net *net, __be32 label)
{
	struct ip6_flowlabel *fl;

	rcu_read_lock();
	fl = __fl_lookup(net, label);
	if (fl && !atomic_inc_not_zero(&fl->users))
		fl = NULL;
	rcu_read_unlock();
	return fl;
}

static bool fl_shared_exclusive(struct ip6_flowlabel *fl)
{
	return fl->share == IPV6_FL_S_EXCL ||
	       fl->share == IPV6_FL_S_PROCESS ||
	       fl->share == IPV6_FL_S_USER;
}

static void fl_free_rcu(struct rcu_head *head)
{
	struct ip6_flowlabel *fl = container_of(head, struct ip6_flowlabel, rcu);

	if (fl->share == IPV6_FL_S_PROCESS)
		put_pid(fl->owner.pid);
	kfree(fl->opt);
	kfree(fl);
}


static void fl_free(struct ip6_flowlabel *fl)
{
	if (!fl)
		return;

	if (fl_shared_exclusive(fl) || fl->opt)
		static_branch_slow_dec_deferred(&ipv6_flowlabel_exclusive);

	call_rcu(&fl->rcu, fl_free_rcu);
}

static void fl_release(struct ip6_flowlabel *fl)
{
	spin_lock_bh(&ip6_fl_lock);

	fl->lastuse = jiffies;
	if (atomic_dec_and_test(&fl->users)) {
		unsigned long ttd = fl->lastuse + fl->linger;
		if (time_after(ttd, fl->expires))
			fl->expires = ttd;
		ttd = fl->expires;
		if (fl->opt && fl->share == IPV6_FL_S_EXCL) {
			struct ipv6_txoptions *opt = fl->opt;
			fl->opt = NULL;
			kfree(opt);
		}
		if (!timer_pending(&ip6_fl_gc_timer) ||
		    time_after(ip6_fl_gc_timer.expires, ttd))
			mod_timer(&ip6_fl_gc_timer, ttd);
	}
	spin_unlock_bh(&ip6_fl_lock);
}

static void ip6_fl_gc(struct timer_list *unused)
{
	int i;
	unsigned long now = jiffies;
	unsigned long sched = 0;

	spin_lock(&ip6_fl_lock);

	for (i = 0; i <= FL_HASH_MASK; i++) {
		struct ip6_flowlabel *fl;
		struct ip6_flowlabel __rcu **flp;

		flp = &fl_ht[i];
		while ((fl = rcu_dereference_protected(*flp,
						       lockdep_is_held(&ip6_fl_lock))) != NULL) {
			if (atomic_read(&fl->users) == 0) {
				unsigned long ttd = fl->lastuse + fl->linger;
				if (time_after(ttd, fl->expires))
					fl->expires = ttd;
				ttd = fl->expires;
				if (time_after_eq(now, ttd)) {
					*flp = fl->next;
					fl_free(fl);
					atomic_dec(&fl_size);
					continue;
				}
				if (!sched || time_before(ttd, sched))
					sched = ttd;
			}
			flp = &fl->next;
		}
	}
	if (!sched && atomic_read(&fl_size))
		sched = now + FL_MAX_LINGER;
	if (sched) {
		mod_timer(&ip6_fl_gc_timer, sched);
	}
	spin_unlock(&ip6_fl_lock);
}

static void __net_exit ip6_fl_purge(struct net *net)
{
	int i;

	spin_lock_bh(&ip6_fl_lock);
	for (i = 0; i <= FL_HASH_MASK; i++) {
		struct ip6_flowlabel *fl;
		struct ip6_flowlabel __rcu **flp;

		flp = &fl_ht[i];
		while ((fl = rcu_dereference_protected(*flp,
						       lockdep_is_held(&ip6_fl_lock))) != NULL) {
			if (net_eq(fl->fl_net, net) &&
			    atomic_read(&fl->users) == 0) {
				*flp = fl->next;
				fl_free(fl);
				atomic_dec(&fl_size);
				continue;
			}
			flp = &fl->next;
		}
	}
	spin_unlock_bh(&ip6_fl_lock);
}

static struct ip6_flowlabel *fl_intern(struct net *net,
				       struct ip6_flowlabel *fl, __be32 label)
{
	struct ip6_flowlabel *lfl;

	fl->label = label & IPV6_FLOWLABEL_MASK;

	rcu_read_lock();
	spin_lock_bh(&ip6_fl_lock);
	if (label == 0) {
		for (;;) {
			fl->label = htonl(get_random_u32())&IPV6_FLOWLABEL_MASK;
			if (fl->label) {
				lfl = __fl_lookup(net, fl->label);
				if (!lfl)
					break;
			}
		}
	} else {
		/*
		 * we dropper the ip6_fl_lock, so this entry could reappear
		 * and we need to recheck with it.
		 *
		 * OTOH no need to search the active socket first, like it is
		 * done in ipv6_flowlabel_opt - sock is locked, so new entry
		 * with the same label can only appear on another sock
		 */
		lfl = __fl_lookup(net, fl->label);
		if (lfl) {
			atomic_inc(&lfl->users);
			spin_unlock_bh(&ip6_fl_lock);
			rcu_read_unlock();
			return lfl;
		}
	}

	fl->lastuse = jiffies;
	fl->next = fl_ht[FL_HASH(fl->label)];
	rcu_assign_pointer(fl_ht[FL_HASH(fl->label)], fl);
	atomic_inc(&fl_size);
	spin_unlock_bh(&ip6_fl_lock);
	rcu_read_unlock();
	return NULL;
}



/* Socket flowlabel lists */

struct ip6_flowlabel *__fl6_sock_lookup(struct sock *sk, __be32 label)
{
	struct ipv6_fl_socklist *sfl;

	label &= IPV6_FLOWLABEL_MASK;

	rcu_read_lock();
	for_each_sk_fl_rcu(sk, sfl) {
		struct ip6_flowlabel *fl = sfl->fl;

		if (fl->label == label && atomic_inc_not_zero(&fl->users)) {
			fl->lastuse = jiffies;
			rcu_read_unlock();
			return fl;
		}
	}
	rcu_read_unlock();
	return NULL;
}
EXPORT_SYMBOL_GPL(__fl6_sock_lookup);

void fl6_free_socklist(struct sock *sk)
{
	struct inet_sock *inet = inet_sk(sk);
	struct ipv6_fl_socklist *sfl;

	if (!rcu_access_pointer(inet->ipv6_fl_list))
		return;

	spin_lock_bh(&ip6_sk_fl_lock);
	while ((sfl = rcu_dereference_protected(inet->ipv6_fl_list,
						lockdep_is_held(&ip6_sk_fl_lock))) != NULL) {
		inet->ipv6_fl_list = sfl->next;
		spin_unlock_bh(&ip6_sk_fl_lock);

		fl_release(sfl->fl);
		kfree_rcu(sfl, rcu);

		spin_lock_bh(&ip6_sk_fl_lock);
	}
	spin_unlock_bh(&ip6_sk_fl_lock);
}

/* Service routines */


/*
   It is the only difficult place. flowlabel enforces equal headers
   before and including routing header, however user may supply options
   following rthdr.
 */

struct ipv6_txoptions *fl6_merge_options(struct ipv6_txoptions *opt_space,
					 struct ip6_flowlabel *fl,
					 struct ipv6_txoptions *fopt)
{
	struct ipv6_txoptions *fl_opt = fl->opt;

	if (!fopt || fopt->opt_flen == 0)
		return fl_opt;

	if (fl_opt) {
		opt_space->hopopt = fl_opt->hopopt;
		opt_space->dst0opt = fl_opt->dst0opt;
		opt_space->srcrt = fl_opt->srcrt;
		opt_space->opt_nflen = fl_opt->opt_nflen;
	} else {
		if (fopt->opt_nflen == 0)
			return fopt;
		opt_space->hopopt = NULL;
		opt_space->dst0opt = NULL;
		opt_space->srcrt = NULL;
		opt_space->opt_nflen = 0;
	}
	opt_space->dst1opt = fopt->dst1opt;
	opt_space->opt_flen = fopt->opt_flen;
	opt_space->tot_len = fopt->tot_len;
	return opt_space;
}
EXPORT_SYMBOL_GPL(fl6_merge_options);

static unsigned long check_linger(unsigned long ttl)
{
	if (ttl < FL_MIN_LINGER)
		return FL_MIN_LINGER*HZ;
	if (ttl > FL_MAX_LINGER && !capable(CAP_NET_ADMIN))
		return 0;
	return ttl*HZ;
}

static int fl6_renew(struct ip6_flowlabel *fl, unsigned long linger, unsigned long expires)
{
	linger = check_linger(linger);
	if (!linger)
		return -EPERM;
	expires = check_linger(expires);
	if (!expires)
		return -EPERM;

	spin_lock_bh(&ip6_fl_lock);
	fl->lastuse = jiffies;
	if (time_before(fl->linger, linger))
		fl->linger = linger;
	if (time_before(expires, fl->linger))
		expires = fl->linger;
	if (time_before(fl->expires, fl->lastuse + expires))
		fl->expires = fl->lastuse + expires;
	spin_unlock_bh(&ip6_fl_lock);

	return 0;
}

static struct ip6_flowlabel *
fl_create(struct net *net, struct sock *sk, struct in6_flowlabel_req *freq,
	  sockptr_t optval, int optlen, int *err_p)
{
	struct ip6_flowlabel *fl = NULL;
	int olen;
	int addr_type;
	int err;

	olen = optlen - CMSG_ALIGN(sizeof(*freq));
	err = -EINVAL;
	if (olen > 64 * 1024)
		goto done;

	err = -ENOMEM;
	fl = kzalloc(sizeof(*fl), GFP_KERNEL);
	if (!fl)
		goto done;

	if (olen > 0) {
		struct msghdr msg;
		struct flowi6 flowi6;
		struct ipcm6_cookie ipc6;

		err = -ENOMEM;
		fl->opt = kmalloc(sizeof(*fl->opt) + olen, GFP_KERNEL);
		if (!fl->opt)
			goto done;

		memset(fl->opt, 0, sizeof(*fl->opt));
		fl->opt->tot_len = sizeof(*fl->opt) + olen;
		err = -EFAULT;
		if (copy_from_sockptr_offset(fl->opt + 1, optval,
				CMSG_ALIGN(sizeof(*freq)), olen))
			goto done;

		msg.msg_controllen = olen;
		msg.msg_control = (void *)(fl->opt+1);
		memset(&flowi6, 0, sizeof(flowi6));

		ipc6.opt = fl->opt;
		err = ip6_datagram_send_ctl(net, sk, &msg, &flowi6, &ipc6);
		if (err)
			goto done;
		err = -EINVAL;
		if (fl->opt->opt_flen)
			goto done;
		if (fl->opt->opt_nflen == 0) {
			kfree(fl->opt);
			fl->opt = NULL;
		}
	}

	fl->fl_net = net;
	fl->expires = jiffies;
	err = fl6_renew(fl, freq->flr_linger, freq->flr_expires);
	if (err)
		goto done;
	fl->share = freq->flr_share;
	addr_type = ipv6_addr_type(&freq->flr_dst);
	if ((addr_type & IPV6_ADDR_MAPPED) ||
	    addr_type == IPV6_ADDR_ANY) {
		err = -EINVAL;
		goto done;
	}
	fl->dst = freq->flr_dst;
	atomic_set(&fl->users, 1);
	switch (fl->share) {
	case IPV6_FL_S_EXCL:
	case IPV6_FL_S_ANY:
		break;
	case IPV6_FL_S_PROCESS:
		fl->owner.pid = get_task_pid(current, PIDTYPE_PID);
		break;
	case IPV6_FL_S_USER:
		fl->owner.uid = current_euid();
		break;
	default:
		err = -EINVAL;
		goto done;
	}
	if (fl_shared_exclusive(fl) || fl->opt) {
		WRITE_ONCE(sock_net(sk)->ipv6.flowlabel_has_excl, 1);
		static_branch_deferred_inc(&ipv6_flowlabel_exclusive);
	}
	return fl;

done:
	if (fl) {
		kfree(fl->opt);
		kfree(fl);
	}
	*err_p = err;
	return NULL;
}

static int mem_check(struct sock *sk)
{
	int room = FL_MAX_SIZE - atomic_read(&fl_size);
	struct ipv6_fl_socklist *sfl;
	int count = 0;

	if (room > FL_MAX_SIZE - FL_MAX_PER_SOCK)
		return 0;

	rcu_read_lock();
	for_each_sk_fl_rcu(sk, sfl)
		count++;
	rcu_read_unlock();

	if (room <= 0 ||
	    ((count >= FL_MAX_PER_SOCK ||
	      (count > 0 && room < FL_MAX_SIZE/2) || room < FL_MAX_SIZE/4) &&
	     !capable(CAP_NET_ADMIN)))
		return -ENOBUFS;

	return 0;
}

static inline void fl_link(struct sock *sk, struct ipv6_fl_socklist *sfl,
			   struct ip6_flowlabel *fl)
{
	struct inet_sock *inet = inet_sk(sk);

	spin_lock_bh(&ip6_sk_fl_lock);
	sfl->fl = fl;
	sfl->next = inet->ipv6_fl_list;
	rcu_assign_pointer(inet->ipv6_fl_list, sfl);
	spin_unlock_bh(&ip6_sk_fl_lock);
}

int ipv6_flowlabel_opt_get(struct sock *sk, struct in6_flowlabel_req *freq,
			   int flags)
{
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct ipv6_fl_socklist *sfl;

	if (flags & IPV6_FL_F_REMOTE) {
		freq->flr_label = np->rcv_flowinfo & IPV6_FLOWLABEL_MASK;
		return 0;
	}

	if (inet6_test_bit(REPFLOW, sk)) {
		freq->flr_label = np->flow_label;
		return 0;
	}

	rcu_read_lock();

	for_each_sk_fl_rcu(sk, sfl) {
		if (sfl->fl->label == (np->flow_label & IPV6_FLOWLABEL_MASK)) {
			spin_lock_bh(&ip6_fl_lock);
			freq->flr_label = sfl->fl->label;
			freq->flr_dst = sfl->fl->dst;
			freq->flr_share = sfl->fl->share;
			freq->flr_expires = (sfl->fl->expires - jiffies) / HZ;
			freq->flr_linger = sfl->fl->linger / HZ;

			spin_unlock_bh(&ip6_fl_lock);
			rcu_read_unlock();
			return 0;
		}
	}
	rcu_read_unlock();

	return -ENOENT;
}

#define socklist_dereference(__sflp) \
	rcu_dereference_protected(__sflp, lockdep_is_held(&ip6_sk_fl_lock))

static int ipv6_flowlabel_put(struct sock *sk, struct in6_flowlabel_req *freq)
{
	struct ipv6_pinfo *np = inet6_sk(sk);
	struct ipv6_fl_socklist __rcu **sflp;
	struct ipv6_fl_socklist *sfl;

	if (freq->flr_flags & IPV6_FL_F_REFLECT) {
		if (sk->sk_protocol != IPPROTO_TCP)
			return -ENOPROTOOPT;
		if (!inet6_test_bit(REPFLOW, sk))
			return -ESRCH;
		np->flow_label = 0;
		inet6_clear_bit(REPFLOW, sk);
		return 0;
	}

	spin_lock_bh(&ip6_sk_fl_lock);
	for (sflp = &inet_sk(sk)->ipv6_fl_list;
	     (sfl = socklist_dereference(*sflp)) != NULL;
	     sflp = &sfl->next) {
		if (sfl->fl->label == freq->flr_label)
			goto found;
	}
	spin_unlock_bh(&ip6_sk_fl_lock);
	return -ESRCH;
found:
	if (freq->flr_label == (np->flow_label & IPV6_FLOWLABEL_MASK))
		np->flow_label &= ~IPV6_FLOWLABEL_MASK;
	*sflp = sfl->next;
	spin_unlock_bh(&ip6_sk_fl_lock);
	fl_release(sfl->fl);
	kfree_rcu(sfl, rcu);
	return 0;
}

static int ipv6_flowlabel_renew(struct sock *sk, struct in6_flowlabel_req *freq)
{
	struct net *net = sock_net(sk);
	struct ipv6_fl_socklist *sfl;
	int err;

	rcu_read_lock();
	for_each_sk_fl_rcu(sk, sfl) {
		if (sfl->fl->label == freq->flr_label) {
			err = fl6_renew(sfl->fl, freq->flr_linger,
					freq->flr_expires);
			rcu_read_unlock();
			return err;
		}
	}
	rcu_read_unlock();

	if (freq->flr_share == IPV6_FL_S_NONE &&
	    ns_capable(net->user_ns, CAP_NET_ADMIN)) {
		struct ip6_flowlabel *fl = fl_lookup(net, freq->flr_label);

		if (fl) {
			err = fl6_renew(fl, freq->flr_linger,
					freq->flr_expires);
			fl_release(fl);
			return err;
		}
	}
	return -ESRCH;
}

static int ipv6_flowlabel_get(struct sock *sk, struct in6_flowlabel_req *freq,
		sockptr_t optval, int optlen)
{
	struct ipv6_fl_socklist *sfl, *sfl1 = NULL;
	struct ip6_flowlabel *fl, *fl1 = NULL;
	struct net *net = sock_net(sk);
	int err;

	if (freq->flr_flags & IPV6_FL_F_REFLECT) {
		if (net->ipv6.sysctl.flowlabel_consistency) {
			net_info_ratelimited("Can not set IPV6_FL_F_REFLECT if flowlabel_consistency sysctl is enable\n");
			return -EPERM;
		}

		if (sk->sk_protocol != IPPROTO_TCP)
			return -ENOPROTOOPT;
		inet6_set_bit(REPFLOW, sk);
		return 0;
	}

	if (freq->flr_label & ~IPV6_FLOWLABEL_MASK)
		return -EINVAL;
	if (net->ipv6.sysctl.flowlabel_state_ranges &&
	    (freq->flr_label & IPV6_FLOWLABEL_STATELESS_FLAG))
		return -ERANGE;

	fl = fl_create(net, sk, freq, optval, optlen, &err);
	if (!fl)
		return err;

	sfl1 = kmalloc(sizeof(*sfl1), GFP_KERNEL);

	if (freq->flr_label) {
		err = -EEXIST;
		rcu_read_lock();
		for_each_sk_fl_rcu(sk, sfl) {
			if (sfl->fl->label == freq->flr_label) {
				if (freq->flr_flags & IPV6_FL_F_EXCL) {
					rcu_read_unlock();
					goto done;
				}
				fl1 = sfl->fl;
				if (!atomic_inc_not_zero(&fl1->users))
					fl1 = NULL;
				break;
			}
		}
		rcu_read_unlock();

		if (!fl1)
			fl1 = fl_lookup(net, freq->flr_label);
		if (fl1) {
recheck:
			err = -EEXIST;
			if (freq->flr_flags&IPV6_FL_F_EXCL)
				goto release;
			err = -EPERM;
			if (fl1->share == IPV6_FL_S_EXCL ||
			    fl1->share != fl->share ||
			    ((fl1->share == IPV6_FL_S_PROCESS) &&
			     (fl1->owner.pid != fl->owner.pid)) ||
			    ((fl1->share == IPV6_FL_S_USER) &&
			     !uid_eq(fl1->owner.uid, fl->owner.uid)))
				goto release;

			err = -ENOMEM;
			if (!sfl1)
				goto release;
			if (fl->linger > fl1->linger)
				fl1->linger = fl->linger;
			if ((long)(fl->expires - fl1->expires) > 0)
				fl1->expires = fl->expires;
			fl_link(sk, sfl1, fl1);
			fl_free(fl);
			return 0;

release:
			fl_release(fl1);
			goto done;
		}
	}
	err = -ENOENT;
	if (!(freq->flr_flags & IPV6_FL_F_CREATE))
		goto done;

	err = -ENOMEM;
	if (!sfl1)
		goto done;

	err = mem_check(sk);
	if (err != 0)
		goto done;

	fl1 = fl_intern(net, fl, freq->flr_label);
	if (fl1)
		goto recheck;

	if (!freq->flr_label) {
		size_t offset = offsetof(struct in6_flowlabel_req, flr_label);

		if (copy_to_sockptr_offset(optval, offset, &fl->label,
				sizeof(fl->label))) {
			/* Intentionally ignore fault. */
		}
	}

	fl_link(sk, sfl1, fl);
	return 0;
done:
	fl_free(fl);
	kfree(sfl1);
	return err;
}

int ipv6_flowlabel_opt(struct sock *sk, sockptr_t optval, int optlen)
{
	struct in6_flowlabel_req freq;

	if (optlen < sizeof(freq))
		return -EINVAL;
	if (copy_from_sockptr(&freq, optval, sizeof(freq)))
		return -EFAULT;

	switch (freq.flr_action) {
	case IPV6_FL_A_PUT:
		return ipv6_flowlabel_put(sk, &freq);
	case IPV6_FL_A_RENEW:
		return ipv6_flowlabel_renew(sk, &freq);
	case IPV6_FL_A_GET:
		return ipv6_flowlabel_get(sk, &freq, optval, optlen);
	default:
		return -EINVAL;
	}
}

#ifdef CONFIG_PROC_FS

struct ip6fl_iter_state {
	struct seq_net_private p;
	struct pid_namespace *pid_ns;
	int bucket;
};

#define ip6fl_seq_private(seq)	((struct ip6fl_iter_state *)(seq)->private)

static struct ip6_flowlabel *ip6fl_get_first(struct seq_file *seq)
{
	struct ip6_flowlabel *fl = NULL;
	struct ip6fl_iter_state *state = ip6fl_seq_private(seq);
	struct net *net = seq_file_net(seq);

	for (state->bucket = 0; state->bucket <= FL_HASH_MASK; ++state->bucket) {
		for_each_fl_rcu(state->bucket, fl) {
			if (net_eq(fl->fl_net, net))
				goto out;
		}
	}
	fl = NULL;
out:
	return fl;
}

static struct ip6_flowlabel *ip6fl_get_next(struct seq_file *seq, struct ip6_flowlabel *fl)
{
	struct ip6fl_iter_state *state = ip6fl_seq_private(seq);
	struct net *net = seq_file_net(seq);

	for_each_fl_continue_rcu(fl) {
		if (net_eq(fl->fl_net, net))
			goto out;
	}

try_again:
	if (++state->bucket <= FL_HASH_MASK) {
		for_each_fl_rcu(state->bucket, fl) {
			if (net_eq(fl->fl_net, net))
				goto out;
		}
		goto try_again;
	}
	fl = NULL;

out:
	return fl;
}

static struct ip6_flowlabel *ip6fl_get_idx(struct seq_file *seq, loff_t pos)
{
	struct ip6_flowlabel *fl = ip6fl_get_first(seq);
	if (fl)
		while (pos && (fl = ip6fl_get_next(seq, fl)) != NULL)
			--pos;
	return pos ? NULL : fl;
}

static void *ip6fl_seq_start(struct seq_file *seq, loff_t *pos)
	__acquires(RCU)
{
	struct ip6fl_iter_state *state = ip6fl_seq_private(seq);

	state->pid_ns = proc_pid_ns(file_inode(seq->file)->i_sb);

	rcu_read_lock();
	return *pos ? ip6fl_get_idx(seq, *pos - 1) : SEQ_START_TOKEN;
}

static void *ip6fl_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
	struct ip6_flowlabel *fl;

	if (v == SEQ_START_TOKEN)
		fl = ip6fl_get_first(seq);
	else
		fl = ip6fl_get_next(seq, v);
	++*pos;
	return fl;
}

static void ip6fl_seq_stop(struct seq_file *seq, void *v)
	__releases(RCU)
{
	rcu_read_unlock();
}

static int ip6fl_seq_show(struct seq_file *seq, void *v)
{
	struct ip6fl_iter_state *state = ip6fl_seq_private(seq);
	if (v == SEQ_START_TOKEN) {
		seq_puts(seq, "Label S Owner  Users  Linger Expires  Dst                              Opt\n");
	} else {
		struct ip6_flowlabel *fl = v;
		seq_printf(seq,
			   "%05X %-1d %-6d %-6d %-6ld %-8ld %pi6 %-4d\n",
			   (unsigned int)ntohl(fl->label),
			   fl->share,
			   ((fl->share == IPV6_FL_S_PROCESS) ?
			    pid_nr_ns(fl->owner.pid, state->pid_ns) :
			    ((fl->share == IPV6_FL_S_USER) ?
			     from_kuid_munged(seq_user_ns(seq), fl->owner.uid) :
			     0)),
			   atomic_read(&fl->users),
			   fl->linger/HZ,
			   (long)(fl->expires - jiffies)/HZ,
			   &fl->dst,
			   fl->opt ? fl->opt->opt_nflen : 0);
	}
	return 0;
}

static const struct seq_operations ip6fl_seq_ops = {
	.start	=	ip6fl_seq_start,
	.next	=	ip6fl_seq_next,
	.stop	=	ip6fl_seq_stop,
	.show	=	ip6fl_seq_show,
};

static int __net_init ip6_flowlabel_proc_init(struct net *net)
{
	if (!proc_create_net("ip6_flowlabel", 0444, net->proc_net,
			&ip6fl_seq_ops, sizeof(struct ip6fl_iter_state)))
		return -ENOMEM;
	return 0;
}

static void __net_exit ip6_flowlabel_proc_fini(struct net *net)
{
	remove_proc_entry("ip6_flowlabel", net->proc_net);
}
#else
static inline int ip6_flowlabel_proc_init(struct net *net)
{
	return 0;
}
static inline void ip6_flowlabel_proc_fini(struct net *net)
{
}
#endif

static void __net_exit ip6_flowlabel_net_exit(struct net *net)
{
	ip6_fl_purge(net);
	ip6_flowlabel_proc_fini(net);
}

static struct pernet_operations ip6_flowlabel_net_ops = {
	.init = ip6_flowlabel_proc_init,
	.exit = ip6_flowlabel_net_exit,
};

int ip6_flowlabel_init(void)
{
	return register_pernet_subsys(&ip6_flowlabel_net_ops);
}

void ip6_flowlabel_cleanup(void)
{
	static_key_deferred_flush(&ipv6_flowlabel_exclusive);
	timer_delete(&ip6_fl_gc_timer);
	unregister_pernet_subsys(&ip6_flowlabel_net_ops);
}