/*
 * L2TP subsystem debugfs
 *
 * Copyright (c) 2010 Katalix Systems Ltd
 *
 *	This program is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU General Public License
 *	as published by the Free Software Foundation; either version
 *	2 of the License, or (at your option) any later version.
 */

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/socket.h>
#include <linux/hash.h>
#include <linux/l2tp.h>
#include <linux/in.h>
#include <linux/etherdevice.h>
#include <linux/spinlock.h>
#include <linux/debugfs.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/icmp.h>
#include <net/udp.h>
#include <net/inet_common.h>
#include <net/inet_hashtables.h>
#include <net/tcp_states.h>
#include <net/protocol.h>
#include <net/xfrm.h>
#include <net/net_namespace.h>
#include <net/netns/generic.h>

#include "l2tp_core.h"

static struct dentry *rootdir;
static struct dentry *tunnels;

struct l2tp_dfs_seq_data {
	struct net *net;
	int tunnel_idx;			/* current tunnel */
	int session_idx;		/* index of session within current tunnel */
	struct l2tp_tunnel *tunnel;
	struct l2tp_session *session;	/* NULL means get next tunnel */
};

static void l2tp_dfs_next_tunnel(struct l2tp_dfs_seq_data *pd)
{
	/* Drop reference taken during previous invocation */
	if (pd->tunnel)
		l2tp_tunnel_dec_refcount(pd->tunnel);

	pd->tunnel = l2tp_tunnel_get_nth(pd->net, pd->tunnel_idx);
	pd->tunnel_idx++;
}

static void l2tp_dfs_next_session(struct l2tp_dfs_seq_data *pd)
{
	/* Drop reference taken during previous invocation */
	if (pd->session)
		l2tp_session_dec_refcount(pd->session);

	pd->session = l2tp_session_get_nth(pd->tunnel, pd->session_idx);
	pd->session_idx++;

	if (pd->session == NULL) {
		pd->session_idx = 0;
		l2tp_dfs_next_tunnel(pd);
	}

}

static void *l2tp_dfs_seq_start(struct seq_file *m, loff_t *offs)
{
	struct l2tp_dfs_seq_data *pd = SEQ_START_TOKEN;
	loff_t pos = *offs;

	if (!pos)
		goto out;

	BUG_ON(m->private == NULL);
	pd = m->private;

	if (pd->tunnel == NULL)
		l2tp_dfs_next_tunnel(pd);
	else
		l2tp_dfs_next_session(pd);

	/* NULL tunnel and session indicates end of list */
	if ((pd->tunnel == NULL) && (pd->session == NULL))
		pd = NULL;

out:
	return pd;
}


static void *l2tp_dfs_seq_next(struct seq_file *m, void *v, loff_t *pos)
{
	(*pos)++;
	return NULL;
}

static void l2tp_dfs_seq_stop(struct seq_file *p, void *v)
{
	struct l2tp_dfs_seq_data *pd = v;

	if (!pd || pd == SEQ_START_TOKEN)
		return;

	/* Drop reference taken by last invocation of l2tp_dfs_next_session()
	 * or l2tp_dfs_next_tunnel().
	 */
	if (pd->session) {
		l2tp_session_dec_refcount(pd->session);
		pd->session = NULL;
	}
	if (pd->tunnel) {
		l2tp_tunnel_dec_refcount(pd->tunnel);
		pd->tunnel = NULL;
	}
}

static void l2tp_dfs_seq_tunnel_show(struct seq_file *m, void *v)
{
	struct l2tp_tunnel *tunnel = v;
	int session_count = 0;
	int hash;
	struct hlist_node *walk;
	struct hlist_node *tmp;

	read_lock_bh(&tunnel->hlist_lock);
	for (hash = 0; hash < L2TP_HASH_SIZE; hash++) {
		hlist_for_each_safe(walk, tmp, &tunnel->session_hlist[hash]) {
			struct l2tp_session *session;

			session = hlist_entry(walk, struct l2tp_session, hlist);
			if (session->session_id == 0)
				continue;

			session_count++;
		}
	}
	read_unlock_bh(&tunnel->hlist_lock);

	seq_printf(m, "\nTUNNEL %u peer %u", tunnel->tunnel_id, tunnel->peer_tunnel_id);
	if (tunnel->sock) {
		struct inet_sock *inet = inet_sk(tunnel->sock);

#if IS_ENABLED(CONFIG_IPV6)
		if (tunnel->sock->sk_family == AF_INET6) {
			const struct ipv6_pinfo *np = inet6_sk(tunnel->sock);

			seq_printf(m, " from %pI6c to %pI6c\n",
				&np->saddr, &tunnel->sock->sk_v6_daddr);
		} else
#endif
		seq_printf(m, " from %pI4 to %pI4\n",
			   &inet->inet_saddr, &inet->inet_daddr);
		if (tunnel->encap == L2TP_ENCAPTYPE_UDP)
			seq_printf(m, " source port %hu, dest port %hu\n",
				   ntohs(inet->inet_sport), ntohs(inet->inet_dport));
	}
	seq_printf(m, " L2TPv%d, %s\n", tunnel->version,
		   tunnel->encap == L2TP_ENCAPTYPE_UDP ? "UDP" :
		   tunnel->encap == L2TP_ENCAPTYPE_IP ? "IP" :
		   "");
	seq_printf(m, " %d sessions, refcnt %d/%d\n", session_count,
		   tunnel->sock ? refcount_read(&tunnel->sock->sk_refcnt) : 0,
		   refcount_read(&tunnel->ref_count));
	seq_printf(m, " %08x rx %ld/%ld/%ld rx %ld/%ld/%ld\n",
		   tunnel->debug,
		   atomic_long_read(&tunnel->stats.tx_packets),
		   atomic_long_read(&tunnel->stats.tx_bytes),
		   atomic_long_read(&tunnel->stats.tx_errors),
		   atomic_long_read(&tunnel->stats.rx_packets),
		   atomic_long_read(&tunnel->stats.rx_bytes),
		   atomic_long_read(&tunnel->stats.rx_errors));

	if (tunnel->show != NULL)
		tunnel->show(m, tunnel);
}

static void l2tp_dfs_seq_session_show(struct seq_file *m, void *v)
{
	struct l2tp_session *session = v;

	seq_printf(m, "  SESSION %u, peer %u, %s\n", session->session_id,
		   session->peer_session_id,
		   session->pwtype == L2TP_PWTYPE_ETH ? "ETH" :
		   session->pwtype == L2TP_PWTYPE_PPP ? "PPP" :
		   "");
	if (session->send_seq || session->recv_seq)
		seq_printf(m, "   nr %hu, ns %hu\n", session->nr, session->ns);
	seq_printf(m, "   refcnt %d\n", refcount_read(&session->ref_count));
	seq_printf(m, "   config %d/%d/%c/%c/%s/%s %08x %u\n",
		   session->mtu, session->mru,
		   session->recv_seq ? 'R' : '-',
		   session->send_seq ? 'S' : '-',
		   session->data_seq == 1 ? "IPSEQ" :
		   session->data_seq == 2 ? "DATASEQ" : "-",
		   session->lns_mode ? "LNS" : "LAC",
		   session->debug,
		   jiffies_to_msecs(session->reorder_timeout));
	seq_printf(m, "   offset 0 l2specific %hu/%hu\n",
		   session->l2specific_type, l2tp_get_l2specific_len(session));
	if (session->cookie_len) {
		seq_printf(m, "   cookie %02x%02x%02x%02x",
			   session->cookie[0], session->cookie[1],
			   session->cookie[2], session->cookie[3]);
		if (session->cookie_len == 8)
			seq_printf(m, "%02x%02x%02x%02x",
				   session->cookie[4], session->cookie[5],
				   session->cookie[6], session->cookie[7]);
		seq_printf(m, "\n");
	}
	if (session->peer_cookie_len) {
		seq_printf(m, "   peer cookie %02x%02x%02x%02x",
			   session->peer_cookie[0], session->peer_cookie[1],
			   session->peer_cookie[2], session->peer_cookie[3]);
		if (session->peer_cookie_len == 8)
			seq_printf(m, "%02x%02x%02x%02x",
				   session->peer_cookie[4], session->peer_cookie[5],
				   session->peer_cookie[6], session->peer_cookie[7]);
		seq_printf(m, "\n");
	}

	seq_printf(m, "   %hu/%hu tx %ld/%ld/%ld rx %ld/%ld/%ld\n",
		   session->nr, session->ns,
		   atomic_long_read(&session->stats.tx_packets),
		   atomic_long_read(&session->stats.tx_bytes),
		   atomic_long_read(&session->stats.tx_errors),
		   atomic_long_read(&session->stats.rx_packets),
		   atomic_long_read(&session->stats.rx_bytes),
		   atomic_long_read(&session->stats.rx_errors));

	if (session->show != NULL)
		session->show(m, session);
}

static int l2tp_dfs_seq_show(struct seq_file *m, void *v)
{
	struct l2tp_dfs_seq_data *pd = v;

	/* display header on line 1 */
	if (v == SEQ_START_TOKEN) {
		seq_puts(m, "TUNNEL ID, peer ID from IP to IP\n");
		seq_puts(m, " L2TPv2/L2TPv3, UDP/IP\n");
		seq_puts(m, " sessions session-count, refcnt refcnt/sk->refcnt\n");
		seq_puts(m, " debug tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
		seq_puts(m, "  SESSION ID, peer ID, PWTYPE\n");
		seq_puts(m, "   refcnt cnt\n");
		seq_puts(m, "   offset OFFSET l2specific TYPE/LEN\n");
		seq_puts(m, "   [ cookie ]\n");
		seq_puts(m, "   [ peer cookie ]\n");
		seq_puts(m, "   config mtu/mru/rcvseq/sendseq/dataseq/lns debug reorderto\n");
		seq_puts(m, "   nr/ns tx-pkts/bytes/errs rx-pkts/bytes/errs\n");
		goto out;
	}

	if (!pd->session)
		l2tp_dfs_seq_tunnel_show(m, pd->tunnel);
	else
		l2tp_dfs_seq_session_show(m, pd->session);

out:
	return 0;
}

static const struct seq_operations l2tp_dfs_seq_ops = {
	.start		= l2tp_dfs_seq_start,
	.next		= l2tp_dfs_seq_next,
	.stop		= l2tp_dfs_seq_stop,
	.show		= l2tp_dfs_seq_show,
};

static int l2tp_dfs_seq_open(struct inode *inode, struct file *file)
{
	struct l2tp_dfs_seq_data *pd;
	struct seq_file *seq;
	int rc = -ENOMEM;

	pd = kzalloc(sizeof(*pd), GFP_KERNEL);
	if (pd == NULL)
		goto out;

	/* Derive the network namespace from the pid opening the
	 * file.
	 */
	pd->net = get_net_ns_by_pid(current->pid);
	if (IS_ERR(pd->net)) {
		rc = PTR_ERR(pd->net);
		goto err_free_pd;
	}

	rc = seq_open(file, &l2tp_dfs_seq_ops);
	if (rc)
		goto err_free_net;

	seq = file->private_data;
	seq->private = pd;

out:
	return rc;

err_free_net:
	put_net(pd->net);
err_free_pd:
	kfree(pd);
	goto out;
}

static int l2tp_dfs_seq_release(struct inode *inode, struct file *file)
{
	struct l2tp_dfs_seq_data *pd;
	struct seq_file *seq;

	seq = file->private_data;
	pd = seq->private;
	if (pd->net)
		put_net(pd->net);
	kfree(pd);
	seq_release(inode, file);

	return 0;
}

static const struct file_operations l2tp_dfs_fops = {
	.owner		= THIS_MODULE,
	.open		= l2tp_dfs_seq_open,
	.read		= seq_read,
	.llseek		= seq_lseek,
	.release	= l2tp_dfs_seq_release,
};

static int __init l2tp_debugfs_init(void)
{
	int rc = 0;

	rootdir = debugfs_create_dir("l2tp", NULL);
	if (IS_ERR(rootdir)) {
		rc = PTR_ERR(rootdir);
		rootdir = NULL;
		goto out;
	}

	tunnels = debugfs_create_file("tunnels", 0600, rootdir, NULL, &l2tp_dfs_fops);
	if (tunnels == NULL)
		rc = -EIO;

	pr_info("L2TP debugfs support\n");

out:
	if (rc)
		pr_warn("unable to init\n");

	return rc;
}

static void __exit l2tp_debugfs_exit(void)
{
	debugfs_remove(tunnels);
	debugfs_remove(rootdir);
}

module_init(l2tp_debugfs_init);
module_exit(l2tp_debugfs_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("James Chapman <jchapman@katalix.com>");
MODULE_DESCRIPTION("L2TP debugfs driver");
MODULE_VERSION("1.0");