drivers/net/ppp/pptp.c - kernel/msm-4.9 - Gitiles

 /*
  *  Point-to-Point Tunneling Protocol for Linux
  *
  *	Authors: Dmitry Kozlov <xeb@mail.ru>
  *
  *	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.
  *
  */

 #include <linux/string.h>
 #include <linux/module.h>
 #include <linux/kernel.h>
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/netdevice.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
 #include <linux/vmalloc.h>
 #include <linux/init.h>
 #include <linux/ppp_channel.h>
 #include <linux/ppp_defs.h>
 #include <linux/if_pppox.h>
 #include <linux/if_ppp.h>
 #include <linux/notifier.h>
 #include <linux/file.h>
 #include <linux/in.h>
 #include <linux/ip.h>
 #include <linux/netfilter.h>
 #include <linux/netfilter_ipv4.h>
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>

 #include <net/sock.h>
 #include <net/protocol.h>
 #include <net/ip.h>
 #include <net/icmp.h>
 #include <net/route.h>
 #include <net/gre.h>

 #include <linux/uaccess.h>

 #define PPTP_DRIVER_VERSION "0.8.5"

 #define MAX_CALLID 65535

 static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1);
 static struct pppox_sock **callid_sock;

 static DEFINE_SPINLOCK(chan_lock);

 static struct proto pptp_sk_proto __read_mostly;
 static const struct ppp_channel_ops pptp_chan_ops;
 static const struct proto_ops pptp_ops;

 #define PPP_LCP_ECHOREQ 0x09
 #define PPP_LCP_ECHOREP 0x0A
 #define SC_RCV_BITS	(SC_RCV_B7_1|SC_RCV_B7_0|SC_RCV_ODDP|SC_RCV_EVNP)

 #define MISSING_WINDOW 20
 #define WRAPPED(curseq, lastseq)\
 	((((curseq) & 0xffffff00) == 0) &&\
 	(((lastseq) & 0xffffff00) == 0xffffff00))

 #define PPTP_GRE_PROTO  0x880B
 #define PPTP_GRE_VER    0x1

 #define PPTP_GRE_FLAG_C	0x80
 #define PPTP_GRE_FLAG_R	0x40
 #define PPTP_GRE_FLAG_K	0x20
 #define PPTP_GRE_FLAG_S	0x10
 #define PPTP_GRE_FLAG_A	0x80

 #define PPTP_GRE_IS_C(f) ((f)&PPTP_GRE_FLAG_C)
 #define PPTP_GRE_IS_R(f) ((f)&PPTP_GRE_FLAG_R)
 #define PPTP_GRE_IS_K(f) ((f)&PPTP_GRE_FLAG_K)
 #define PPTP_GRE_IS_S(f) ((f)&PPTP_GRE_FLAG_S)
 #define PPTP_GRE_IS_A(f) ((f)&PPTP_GRE_FLAG_A)

 #define PPTP_HEADER_OVERHEAD (2+sizeof(struct pptp_gre_header))
 struct pptp_gre_header {
 	u8  flags;
 	u8  ver;
 	u16 protocol;
 	u16 payload_len;
 	u16 call_id;
 	u32 seq;
 	u32 ack;
 } __packed;

 static struct pppox_sock *lookup_chan(u16 call_id, __be32 s_addr)
 {
 	struct pppox_sock *sock;
 	struct pptp_opt *opt;

 	rcu_read_lock();
 	sock = rcu_dereference(callid_sock[call_id]);
 	if (sock) {
 		opt = &sock->proto.pptp;
 		if (opt->dst_addr.sin_addr.s_addr != s_addr)
 			sock = NULL;
 		else
 			sock_hold(sk_pppox(sock));
 	}
 	rcu_read_unlock();

 	return sock;
 }

 static int lookup_chan_dst(u16 call_id, __be32 d_addr)
 {
 	struct pppox_sock *sock;
 	struct pptp_opt *opt;
 	int i;

 	rcu_read_lock();
 	for (i = find_next_bit(callid_bitmap, MAX_CALLID, 1); i < MAX_CALLID;
 	     i = find_next_bit(callid_bitmap, MAX_CALLID, i + 1)) {
 		sock = rcu_dereference(callid_sock[i]);
 		if (!sock)
 			continue;
 		opt = &sock->proto.pptp;
 		if (opt->dst_addr.call_id == call_id &&
 			  opt->dst_addr.sin_addr.s_addr == d_addr)
 			break;
 	}
 	rcu_read_unlock();

 	return i < MAX_CALLID;
 }

 static int add_chan(struct pppox_sock *sock)
 {
 	static int call_id;

 	spin_lock(&chan_lock);
 	if (!sock->proto.pptp.src_addr.call_id)	{
 		call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, call_id + 1);
 		if (call_id == MAX_CALLID) {
 			call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, 1);
 			if (call_id == MAX_CALLID)
 				goto out_err;
 		}
 		sock->proto.pptp.src_addr.call_id = call_id;
 	} else if (test_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap))
 		goto out_err;

 	set_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap);
 	rcu_assign_pointer(callid_sock[sock->proto.pptp.src_addr.call_id], sock);
 	spin_unlock(&chan_lock);

 	return 0;

 out_err:
 	spin_unlock(&chan_lock);
 	return -1;
 }

 static void del_chan(struct pppox_sock *sock)
 {
 	spin_lock(&chan_lock);
 	clear_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap);
 	RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL);
 	spin_unlock(&chan_lock);
 	synchronize_rcu();
 }

 static int pptp_xmit(struct ppp_channel *chan, struct sk_buff *skb)
 {
 	struct sock *sk = (struct sock *) chan->private;
 	struct pppox_sock *po = pppox_sk(sk);
 	struct pptp_opt *opt = &po->proto.pptp;
 	struct pptp_gre_header *hdr;
 	unsigned int header_len = sizeof(*hdr);
 	struct flowi4 fl4;
 	int islcp;
 	int len;
 	unsigned char *data;
 	__u32 seq_recv;


 	struct rtable *rt;
 	struct net_device *tdev;
 	struct iphdr  *iph;
 	int    max_headroom;

 	if (sk_pppox(po)->sk_state & PPPOX_DEAD)
 		goto tx_error;

 	rt = ip_route_output_ports(&init_net, &fl4, NULL,
 				   opt->dst_addr.sin_addr.s_addr,
 				   opt->src_addr.sin_addr.s_addr,
 				   0, 0, IPPROTO_GRE,
 				   RT_TOS(0), 0);
 	if (IS_ERR(rt))
 		goto tx_error;

 	tdev = rt->dst.dev;

 	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(*iph) + sizeof(*hdr) + 2;

 	if (skb_headroom(skb) < max_headroom || skb_cloned(skb) || skb_shared(skb)) {
 		struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
 		if (!new_skb) {
 			ip_rt_put(rt);
 			goto tx_error;
 		}
 		if (skb->sk)
 			skb_set_owner_w(new_skb, skb->sk);
 		kfree_skb(skb);
 		skb = new_skb;
 	}

 	data = skb->data;
 	islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7;

 	/* compress protocol field */
 	if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp)
 		skb_pull(skb, 1);

 	/* Put in the address/control bytes if necessary */
 	if ((opt->ppp_flags & SC_COMP_AC) == 0 || islcp) {
 		data = skb_push(skb, 2);
 		data[0] = PPP_ALLSTATIONS;
 		data[1] = PPP_UI;
 	}

 	len = skb->len;

 	seq_recv = opt->seq_recv;

 	if (opt->ack_sent == seq_recv)
 		header_len -= sizeof(hdr->ack);

 	/* Push down and install GRE header */
 	skb_push(skb, header_len);
 	hdr = (struct pptp_gre_header *)(skb->data);

 	hdr->flags       = PPTP_GRE_FLAG_K;
 	hdr->ver         = PPTP_GRE_VER;
 	hdr->protocol    = htons(PPTP_GRE_PROTO);
 	hdr->call_id     = htons(opt->dst_addr.call_id);

 	hdr->flags      |= PPTP_GRE_FLAG_S;
 	hdr->seq         = htonl(++opt->seq_sent);
 	if (opt->ack_sent != seq_recv)	{
 		/* send ack with this message */
 		hdr->ver |= PPTP_GRE_FLAG_A;
 		hdr->ack  = htonl(seq_recv);
 		opt->ack_sent = seq_recv;
 	}
 	hdr->payload_len = htons(len);

 	/*	Push down and install the IP header. */

 	skb_reset_transport_header(skb);
 	skb_push(skb, sizeof(*iph));
 	skb_reset_network_header(skb);
 	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
 	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE | IPSKB_XFRM_TRANSFORMED | IPSKB_REROUTED);

 	iph =	ip_hdr(skb);
 	iph->version =	4;
 	iph->ihl =	sizeof(struct iphdr) >> 2;
 	if (ip_dont_fragment(sk, &rt->dst))
 		iph->frag_off	=	htons(IP_DF);
 	else
 		iph->frag_off	=	0;
 	iph->protocol = IPPROTO_GRE;
 	iph->tos      = 0;
 	iph->daddr    = fl4.daddr;
 	iph->saddr    = fl4.saddr;
 	iph->ttl      = ip4_dst_hoplimit(&rt->dst);
 	iph->tot_len  = htons(skb->len);

 	skb_dst_drop(skb);
 	skb_dst_set(skb, &rt->dst);

 	nf_reset(skb);

 	skb->ip_summed = CHECKSUM_NONE;
 	ip_select_ident(iph, &rt->dst, NULL);
 	ip_send_check(iph);

 	ip_local_out(skb);
 	return 1;

 tx_error:
 	kfree_skb(skb);
 	return 1;
 }

 static int pptp_rcv_core(struct sock *sk, struct sk_buff *skb)
 {
 	struct pppox_sock *po = pppox_sk(sk);
 	struct pptp_opt *opt = &po->proto.pptp;
 	int headersize, payload_len, seq;
 	__u8 *payload;
 	struct pptp_gre_header *header;

 	if (!(sk->sk_state & PPPOX_CONNECTED)) {
 		if (sock_queue_rcv_skb(sk, skb))
 			goto drop;
 		return NET_RX_SUCCESS;
 	}

 	header = (struct pptp_gre_header *)(skb->data);
 	headersize  = sizeof(*header);

 	/* test if acknowledgement present */
 	if (PPTP_GRE_IS_A(header->ver)) {
 		__u32 ack;

 		if (!pskb_may_pull(skb, headersize))
 			goto drop;
 		header = (struct pptp_gre_header *)(skb->data);

 		/* ack in different place if S = 0 */
 		ack = PPTP_GRE_IS_S(header->flags) ? header->ack : header->seq;

 		ack = ntohl(ack);

 		if (ack > opt->ack_recv)
 			opt->ack_recv = ack;
 		/* also handle sequence number wrap-around  */
 		if (WRAPPED(ack, opt->ack_recv))
 			opt->ack_recv = ack;
 	} else {
 		headersize -= sizeof(header->ack);
 	}
 	/* test if payload present */
 	if (!PPTP_GRE_IS_S(header->flags))
 		goto drop;

 	payload_len = ntohs(header->payload_len);
 	seq         = ntohl(header->seq);

 	/* check for incomplete packet (length smaller than expected) */
 	if (!pskb_may_pull(skb, headersize + payload_len))
 		goto drop;

 	payload = skb->data + headersize;
 	/* check for expected sequence number */
 	if (seq < opt->seq_recv + 1 || WRAPPED(opt->seq_recv, seq)) {
 		if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) &&
 				(PPP_PROTOCOL(payload) == PPP_LCP) &&
 				((payload[4] == PPP_LCP_ECHOREQ) || (payload[4] == PPP_LCP_ECHOREP)))
 			goto allow_packet;
 	} else {
 		opt->seq_recv = seq;
 allow_packet:
 		skb_pull(skb, headersize);

 		if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) {
 			/* chop off address/control */
 			if (skb->len < 3)
 				goto drop;
 			skb_pull(skb, 2);
 		}

 		if ((*skb->data) & 1) {
 			/* protocol is compressed */
 			skb_push(skb, 1)[0] = 0;
 		}

 		skb->ip_summed = CHECKSUM_NONE;
 		skb_set_network_header(skb, skb->head-skb->data);
 		ppp_input(&po->chan, skb);

 		return NET_RX_SUCCESS;
 	}
 drop:
 	kfree_skb(skb);
 	return NET_RX_DROP;
 }

 static int pptp_rcv(struct sk_buff *skb)
 {
 	struct pppox_sock *po;
 	struct pptp_gre_header *header;
 	struct iphdr *iph;

 	if (skb->pkt_type != PACKET_HOST)
 		goto drop;

 	if (!pskb_may_pull(skb, 12))
 		goto drop;

 	iph = ip_hdr(skb);

 	header = (struct pptp_gre_header *)skb->data;

 	if (ntohs(header->protocol) != PPTP_GRE_PROTO || /* PPTP-GRE protocol for PPTP */
 		PPTP_GRE_IS_C(header->flags) ||                /* flag C should be clear */
 		PPTP_GRE_IS_R(header->flags) ||                /* flag R should be clear */
 		!PPTP_GRE_IS_K(header->flags) ||               /* flag K should be set */
 		(header->flags&0xF) != 0)                      /* routing and recursion ctrl = 0 */
 		/* if invalid, discard this packet */
 		goto drop;

 	po = lookup_chan(htons(header->call_id), iph->saddr);
 	if (po) {
 		skb_dst_drop(skb);
 		nf_reset(skb);
 		return sk_receive_skb(sk_pppox(po), skb, 0);
 	}
 drop:
 	kfree_skb(skb);
 	return NET_RX_DROP;
 }

 static int pptp_bind(struct socket *sock, struct sockaddr *uservaddr,
 	int sockaddr_len)
 {
 	struct sock *sk = sock->sk;
 	struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
 	struct pppox_sock *po = pppox_sk(sk);
 	struct pptp_opt *opt = &po->proto.pptp;
 	int error = 0;

 	lock_sock(sk);

 	opt->src_addr = sp->sa_addr.pptp;
 	if (add_chan(po))
 		error = -EBUSY;

 	release_sock(sk);
 	return error;
 }

 static int pptp_connect(struct socket *sock, struct sockaddr *uservaddr,
 	int sockaddr_len, int flags)
 {
 	struct sock *sk = sock->sk;
 	struct sockaddr_pppox *sp = (struct sockaddr_pppox *) uservaddr;
 	struct pppox_sock *po = pppox_sk(sk);
 	struct pptp_opt *opt = &po->proto.pptp;
 	struct rtable *rt;
 	struct flowi4 fl4;
 	int error = 0;

 	if (sp->sa_protocol != PX_PROTO_PPTP)
 		return -EINVAL;

 	if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr))
 		return -EALREADY;

 	lock_sock(sk);
 	/* Check for already bound sockets */
 	if (sk->sk_state & PPPOX_CONNECTED) {
 		error = -EBUSY;
 		goto end;
 	}

 	/* Check for already disconnected sockets, on attempts to disconnect */
 	if (sk->sk_state & PPPOX_DEAD) {
 		error = -EALREADY;
 		goto end;
 	}

 	if (!opt->src_addr.sin_addr.s_addr || !sp->sa_addr.pptp.sin_addr.s_addr) {
 		error = -EINVAL;
 		goto end;
 	}

 	po->chan.private = sk;
 	po->chan.ops = &pptp_chan_ops;

 	rt = ip_route_output_ports(&init_net, &fl4, sk,
 				   opt->dst_addr.sin_addr.s_addr,
 				   opt->src_addr.sin_addr.s_addr,
 				   0, 0,
 				   IPPROTO_GRE, RT_CONN_FLAGS(sk), 0);
 	if (IS_ERR(rt)) {
 		error = -EHOSTUNREACH;
 		goto end;
 	}
 	sk_setup_caps(sk, &rt->dst);

 	po->chan.mtu = dst_mtu(&rt->dst);
 	if (!po->chan.mtu)
 		po->chan.mtu = PPP_MTU;
 	ip_rt_put(rt);
 	po->chan.mtu -= PPTP_HEADER_OVERHEAD;

 	po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header);
 	error = ppp_register_channel(&po->chan);
 	if (error) {
 		pr_err("PPTP: failed to register PPP channel (%d)\n", error);
 		goto end;
 	}

 	opt->dst_addr = sp->sa_addr.pptp;
 	sk->sk_state = PPPOX_CONNECTED;

  end:
 	release_sock(sk);
 	return error;
 }

 static int pptp_getname(struct socket *sock, struct sockaddr *uaddr,
 	int *usockaddr_len, int peer)
 {
 	int len = sizeof(struct sockaddr_pppox);
 	struct sockaddr_pppox sp;

 	sp.sa_family	  = AF_PPPOX;
 	sp.sa_protocol  = PX_PROTO_PPTP;
 	sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr;

 	memcpy(uaddr, &sp, len);

 	*usockaddr_len = len;

 	return 0;
 }

 static int pptp_release(struct socket *sock)
 {
 	struct sock *sk = sock->sk;
 	struct pppox_sock *po;
 	struct pptp_opt *opt;
 	int error = 0;

 	if (!sk)
 		return 0;

 	lock_sock(sk);

 	if (sock_flag(sk, SOCK_DEAD)) {
 		release_sock(sk);
 		return -EBADF;
 	}

 	po = pppox_sk(sk);
 	opt = &po->proto.pptp;
 	del_chan(po);

 	pppox_unbind_sock(sk);
 	sk->sk_state = PPPOX_DEAD;

 	sock_orphan(sk);
 	sock->sk = NULL;

 	release_sock(sk);
 	sock_put(sk);

 	return error;
 }

 static void pptp_sock_destruct(struct sock *sk)
 {
 	if (!(sk->sk_state & PPPOX_DEAD)) {
 		del_chan(pppox_sk(sk));
 		pppox_unbind_sock(sk);
 	}
 	skb_queue_purge(&sk->sk_receive_queue);
 }

 static int pptp_create(struct net *net, struct socket *sock)
 {
 	int error = -ENOMEM;
 	struct sock *sk;
 	struct pppox_sock *po;
 	struct pptp_opt *opt;

 	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto);
 	if (!sk)
 		goto out;

 	sock_init_data(sock, sk);

 	sock->state = SS_UNCONNECTED;
 	sock->ops   = &pptp_ops;

 	sk->sk_backlog_rcv = pptp_rcv_core;
 	sk->sk_state       = PPPOX_NONE;
 	sk->sk_type        = SOCK_STREAM;
 	sk->sk_family      = PF_PPPOX;
 	sk->sk_protocol    = PX_PROTO_PPTP;
 	sk->sk_destruct    = pptp_sock_destruct;

 	po = pppox_sk(sk);
 	opt = &po->proto.pptp;

 	opt->seq_sent = 0; opt->seq_recv = 0xffffffff;
 	opt->ack_recv = 0; opt->ack_sent = 0xffffffff;

 	error = 0;
 out:
 	return error;
 }

 static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
 	unsigned long arg)
 {
 	struct sock *sk = (struct sock *) chan->private;
 	struct pppox_sock *po = pppox_sk(sk);
 	struct pptp_opt *opt = &po->proto.pptp;
 	void __user *argp = (void __user *)arg;
 	int __user *p = argp;
 	int err, val;

 	err = -EFAULT;
 	switch (cmd) {
 	case PPPIOCGFLAGS:
 		val = opt->ppp_flags;
 		if (put_user(val, p))
 			break;
 		err = 0;
 		break;
 	case PPPIOCSFLAGS:
 		if (get_user(val, p))
 			break;
 		opt->ppp_flags = val & ~SC_RCV_BITS;
 		err = 0;
 		break;
 	default:
 		err = -ENOTTY;
 	}

 	return err;
 }

 static const struct ppp_channel_ops pptp_chan_ops = {
 	.start_xmit = pptp_xmit,
 	.ioctl      = pptp_ppp_ioctl,
 };

 static struct proto pptp_sk_proto __read_mostly = {
 	.name     = "PPTP",
 	.owner    = THIS_MODULE,
 	.obj_size = sizeof(struct pppox_sock),
 };

 static const struct proto_ops pptp_ops = {
 	.family     = AF_PPPOX,
 	.owner      = THIS_MODULE,
 	.release    = pptp_release,
 	.bind       = pptp_bind,
 	.connect    = pptp_connect,
 	.socketpair = sock_no_socketpair,
 	.accept     = sock_no_accept,
 	.getname    = pptp_getname,
 	.poll       = sock_no_poll,
 	.listen     = sock_no_listen,
 	.shutdown   = sock_no_shutdown,
 	.setsockopt = sock_no_setsockopt,
 	.getsockopt = sock_no_getsockopt,
 	.sendmsg    = sock_no_sendmsg,
 	.recvmsg    = sock_no_recvmsg,
 	.mmap       = sock_no_mmap,
 	.ioctl      = pppox_ioctl,
 };

 static const struct pppox_proto pppox_pptp_proto = {
 	.create = pptp_create,
 	.owner  = THIS_MODULE,
 };

 static const struct gre_protocol gre_pptp_protocol = {
 	.handler = pptp_rcv,
 };

 static int __init pptp_init_module(void)
 {
 	int err = 0;
 	pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n");

 	callid_sock = vzalloc((MAX_CALLID + 1) * sizeof(void *));
 	if (!callid_sock) {
 		pr_err("PPTP: cann't allocate memory\n");
 		return -ENOMEM;
 	}

 	err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
 	if (err) {
 		pr_err("PPTP: can't add gre protocol\n");
 		goto out_mem_free;
 	}

 	err = proto_register(&pptp_sk_proto, 0);
 	if (err) {
 		pr_err("PPTP: can't register sk_proto\n");
 		goto out_gre_del_protocol;
 	}

 	err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto);
 	if (err) {
 		pr_err("PPTP: can't register pppox_proto\n");
 		goto out_unregister_sk_proto;
 	}

 	return 0;

 out_unregister_sk_proto:
 	proto_unregister(&pptp_sk_proto);
 out_gre_del_protocol:
 	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
 out_mem_free:
 	vfree(callid_sock);

 	return err;
 }

 static void __exit pptp_exit_module(void)
 {
 	unregister_pppox_proto(PX_PROTO_PPTP);
 	proto_unregister(&pptp_sk_proto);
 	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
 	vfree(callid_sock);
 }

 module_init(pptp_init_module);
 module_exit(pptp_exit_module);

 MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");
 MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
 MODULE_LICENSE("GPL");
	/*
	* Point-to-Point Tunneling Protocol for Linux
	*
	* Authors: Dmitry Kozlov <xeb@mail.ru>
	*
	* 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.
	*
	*/

	#include <linux/string.h>
	#include <linux/module.h>
	#include <linux/kernel.h>
	#include <linux/slab.h>
	#include <linux/errno.h>
	#include <linux/netdevice.h>
	#include <linux/net.h>
	#include <linux/skbuff.h>
	#include <linux/vmalloc.h>
	#include <linux/init.h>
	#include <linux/ppp_channel.h>
	#include <linux/ppp_defs.h>
	#include <linux/if_pppox.h>
	#include <linux/if_ppp.h>
	#include <linux/notifier.h>
	#include <linux/file.h>
	#include <linux/in.h>
	#include <linux/ip.h>
	#include <linux/netfilter.h>
	#include <linux/netfilter_ipv4.h>
	#include <linux/rcupdate.h>
	#include <linux/spinlock.h>

	#include <net/sock.h>
	#include <net/protocol.h>
	#include <net/ip.h>
	#include <net/icmp.h>
	#include <net/route.h>
	#include <net/gre.h>

	#include <linux/uaccess.h>

	#define PPTP_DRIVER_VERSION "0.8.5"

	#define MAX_CALLID 65535

	static DECLARE_BITMAP(callid_bitmap, MAX_CALLID + 1);
	static struct pppox_sock **callid_sock;

	static DEFINE_SPINLOCK(chan_lock);

	static struct proto pptp_sk_proto __read_mostly;
	static const struct ppp_channel_ops pptp_chan_ops;
	static const struct proto_ops pptp_ops;

	#define PPP_LCP_ECHOREQ 0x09
	#define PPP_LCP_ECHOREP 0x0A
	#define SC_RCV_BITS (SC_RCV_B7_1\|SC_RCV_B7_0\|SC_RCV_ODDP\|SC_RCV_EVNP)

	#define MISSING_WINDOW 20
	#define WRAPPED(curseq, lastseq)\
	((((curseq) & 0xffffff00) == 0) &&\
	(((lastseq) & 0xffffff00) == 0xffffff00))

	#define PPTP_GRE_PROTO 0x880B
	#define PPTP_GRE_VER 0x1

	#define PPTP_GRE_FLAG_C 0x80
	#define PPTP_GRE_FLAG_R 0x40
	#define PPTP_GRE_FLAG_K 0x20
	#define PPTP_GRE_FLAG_S 0x10
	#define PPTP_GRE_FLAG_A 0x80

	#define PPTP_GRE_IS_C(f) ((f)&PPTP_GRE_FLAG_C)
	#define PPTP_GRE_IS_R(f) ((f)&PPTP_GRE_FLAG_R)
	#define PPTP_GRE_IS_K(f) ((f)&PPTP_GRE_FLAG_K)
	#define PPTP_GRE_IS_S(f) ((f)&PPTP_GRE_FLAG_S)
	#define PPTP_GRE_IS_A(f) ((f)&PPTP_GRE_FLAG_A)

	#define PPTP_HEADER_OVERHEAD (2+sizeof(struct pptp_gre_header))
	struct pptp_gre_header {
	u8 flags;
	u8 ver;
	u16 protocol;
	u16 payload_len;
	u16 call_id;
	u32 seq;
	u32 ack;
	} __packed;

	static struct pppox_sock *lookup_chan(u16 call_id, __be32 s_addr)
	{
	struct pppox_sock *sock;
	struct pptp_opt *opt;

	rcu_read_lock();
	sock = rcu_dereference(callid_sock[call_id]);
	if (sock) {
	opt = &sock->proto.pptp;
	if (opt->dst_addr.sin_addr.s_addr != s_addr)
	sock = NULL;
	else
	sock_hold(sk_pppox(sock));
	}
	rcu_read_unlock();

	return sock;
	}

	static int lookup_chan_dst(u16 call_id, __be32 d_addr)
	{
	struct pppox_sock *sock;
	struct pptp_opt *opt;
	int i;

	rcu_read_lock();
	for (i = find_next_bit(callid_bitmap, MAX_CALLID, 1); i < MAX_CALLID;
	i = find_next_bit(callid_bitmap, MAX_CALLID, i + 1)) {
	sock = rcu_dereference(callid_sock[i]);
	if (!sock)
	continue;
	opt = &sock->proto.pptp;
	if (opt->dst_addr.call_id == call_id &&
	opt->dst_addr.sin_addr.s_addr == d_addr)
	break;
	}
	rcu_read_unlock();

	return i < MAX_CALLID;
	}

	static int add_chan(struct pppox_sock *sock)
	{
	static int call_id;

	spin_lock(&chan_lock);
	if (!sock->proto.pptp.src_addr.call_id) {
	call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, call_id + 1);
	if (call_id == MAX_CALLID) {
	call_id = find_next_zero_bit(callid_bitmap, MAX_CALLID, 1);
	if (call_id == MAX_CALLID)
	goto out_err;
	}
	sock->proto.pptp.src_addr.call_id = call_id;
	} else if (test_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap))
	goto out_err;

	set_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap);
	rcu_assign_pointer(callid_sock[sock->proto.pptp.src_addr.call_id], sock);
	spin_unlock(&chan_lock);

	return 0;

	out_err:
	spin_unlock(&chan_lock);
	return -1;
	}

	static void del_chan(struct pppox_sock *sock)
	{
	spin_lock(&chan_lock);
	clear_bit(sock->proto.pptp.src_addr.call_id, callid_bitmap);
	RCU_INIT_POINTER(callid_sock[sock->proto.pptp.src_addr.call_id], NULL);
	spin_unlock(&chan_lock);
	synchronize_rcu();
	}

	static int pptp_xmit(struct ppp_channel chan, struct sk_buff skb)
	{
	struct sock sk = (struct sock ) chan->private;
	struct pppox_sock *po = pppox_sk(sk);
	struct pptp_opt *opt = &po->proto.pptp;
	struct pptp_gre_header *hdr;
	unsigned int header_len = sizeof(*hdr);
	struct flowi4 fl4;
	int islcp;
	int len;
	unsigned char *data;
	__u32 seq_recv;


	struct rtable *rt;
	struct net_device *tdev;
	struct iphdr *iph;
	int max_headroom;

	if (sk_pppox(po)->sk_state & PPPOX_DEAD)
	goto tx_error;

	rt = ip_route_output_ports(&init_net, &fl4, NULL,
	opt->dst_addr.sin_addr.s_addr,
	opt->src_addr.sin_addr.s_addr,
	0, 0, IPPROTO_GRE,
	RT_TOS(0), 0);
	if (IS_ERR(rt))
	goto tx_error;

	tdev = rt->dst.dev;

	max_headroom = LL_RESERVED_SPACE(tdev) + sizeof(iph) + sizeof(hdr) + 2;

	if (skb_headroom(skb) < max_headroom \|\| skb_cloned(skb) \|\| skb_shared(skb)) {
	struct sk_buff *new_skb = skb_realloc_headroom(skb, max_headroom);
	if (!new_skb) {
	ip_rt_put(rt);
	goto tx_error;
	}
	if (skb->sk)
	skb_set_owner_w(new_skb, skb->sk);
	kfree_skb(skb);
	skb = new_skb;
	}

	data = skb->data;
	islcp = ((data[0] << 8) + data[1]) == PPP_LCP && 1 <= data[2] && data[2] <= 7;

	/* compress protocol field */
	if ((opt->ppp_flags & SC_COMP_PROT) && data[0] == 0 && !islcp)
	skb_pull(skb, 1);

	/* Put in the address/control bytes if necessary */
	if ((opt->ppp_flags & SC_COMP_AC) == 0 \|\| islcp) {
	data = skb_push(skb, 2);
	data[0] = PPP_ALLSTATIONS;
	data[1] = PPP_UI;
	}

	len = skb->len;

	seq_recv = opt->seq_recv;

	if (opt->ack_sent == seq_recv)
	header_len -= sizeof(hdr->ack);

	/* Push down and install GRE header */
	skb_push(skb, header_len);
	hdr = (struct pptp_gre_header *)(skb->data);

	hdr->flags = PPTP_GRE_FLAG_K;
	hdr->ver = PPTP_GRE_VER;
	hdr->protocol = htons(PPTP_GRE_PROTO);
	hdr->call_id = htons(opt->dst_addr.call_id);

	hdr->flags \|= PPTP_GRE_FLAG_S;
	hdr->seq = htonl(++opt->seq_sent);
	if (opt->ack_sent != seq_recv) {
	/* send ack with this message */
	hdr->ver \|= PPTP_GRE_FLAG_A;
	hdr->ack = htonl(seq_recv);
	opt->ack_sent = seq_recv;
	}
	hdr->payload_len = htons(len);

	/* Push down and install the IP header. */

	skb_reset_transport_header(skb);
	skb_push(skb, sizeof(*iph));
	skb_reset_network_header(skb);
	memset(&(IPCB(skb)->opt), 0, sizeof(IPCB(skb)->opt));
	IPCB(skb)->flags &= ~(IPSKB_XFRM_TUNNEL_SIZE \| IPSKB_XFRM_TRANSFORMED \| IPSKB_REROUTED);

	iph = ip_hdr(skb);
	iph->version = 4;
	iph->ihl = sizeof(struct iphdr) >> 2;
	if (ip_dont_fragment(sk, &rt->dst))
	iph->frag_off = htons(IP_DF);
	else
	iph->frag_off = 0;
	iph->protocol = IPPROTO_GRE;
	iph->tos = 0;
	iph->daddr = fl4.daddr;
	iph->saddr = fl4.saddr;
	iph->ttl = ip4_dst_hoplimit(&rt->dst);
	iph->tot_len = htons(skb->len);

	skb_dst_drop(skb);
	skb_dst_set(skb, &rt->dst);

	nf_reset(skb);

	skb->ip_summed = CHECKSUM_NONE;
	ip_select_ident(iph, &rt->dst, NULL);
	ip_send_check(iph);

	ip_local_out(skb);
	return 1;

	tx_error:
	kfree_skb(skb);
	return 1;
	}

	static int pptp_rcv_core(struct sock sk, struct sk_buff skb)
	{
	struct pppox_sock *po = pppox_sk(sk);
	struct pptp_opt *opt = &po->proto.pptp;
	int headersize, payload_len, seq;
	__u8 *payload;
	struct pptp_gre_header *header;

	if (!(sk->sk_state & PPPOX_CONNECTED)) {
	if (sock_queue_rcv_skb(sk, skb))
	goto drop;
	return NET_RX_SUCCESS;
	}

	header = (struct pptp_gre_header *)(skb->data);
	headersize = sizeof(*header);

	/* test if acknowledgement present */
	if (PPTP_GRE_IS_A(header->ver)) {
	__u32 ack;

	if (!pskb_may_pull(skb, headersize))
	goto drop;
	header = (struct pptp_gre_header *)(skb->data);

	/* ack in different place if S = 0 */
	ack = PPTP_GRE_IS_S(header->flags) ? header->ack : header->seq;

	ack = ntohl(ack);

	if (ack > opt->ack_recv)
	opt->ack_recv = ack;
	/* also handle sequence number wrap-around */
	if (WRAPPED(ack, opt->ack_recv))
	opt->ack_recv = ack;
	} else {
	headersize -= sizeof(header->ack);
	}
	/* test if payload present */
	if (!PPTP_GRE_IS_S(header->flags))
	goto drop;

	payload_len = ntohs(header->payload_len);
	seq = ntohl(header->seq);

	/* check for incomplete packet (length smaller than expected) */
	if (!pskb_may_pull(skb, headersize + payload_len))
	goto drop;

	payload = skb->data + headersize;
	/* check for expected sequence number */
	if (seq < opt->seq_recv + 1 \|\| WRAPPED(opt->seq_recv, seq)) {
	if ((payload[0] == PPP_ALLSTATIONS) && (payload[1] == PPP_UI) &&
	(PPP_PROTOCOL(payload) == PPP_LCP) &&
	((payload[4] == PPP_LCP_ECHOREQ) \|\| (payload[4] == PPP_LCP_ECHOREP)))
	goto allow_packet;
	} else {
	opt->seq_recv = seq;
	allow_packet:
	skb_pull(skb, headersize);

	if (payload[0] == PPP_ALLSTATIONS && payload[1] == PPP_UI) {
	/* chop off address/control */
	if (skb->len < 3)
	goto drop;
	skb_pull(skb, 2);
	}

	if ((*skb->data) & 1) {
	/* protocol is compressed */
	skb_push(skb, 1)[0] = 0;
	}

	skb->ip_summed = CHECKSUM_NONE;
	skb_set_network_header(skb, skb->head-skb->data);
	ppp_input(&po->chan, skb);

	return NET_RX_SUCCESS;
	}
	drop:
	kfree_skb(skb);
	return NET_RX_DROP;
	}

	static int pptp_rcv(struct sk_buff *skb)
	{
	struct pppox_sock *po;
	struct pptp_gre_header *header;
	struct iphdr *iph;

	if (skb->pkt_type != PACKET_HOST)
	goto drop;

	if (!pskb_may_pull(skb, 12))
	goto drop;

	iph = ip_hdr(skb);

	header = (struct pptp_gre_header *)skb->data;

	if (ntohs(header->protocol) != PPTP_GRE_PROTO \|\| /* PPTP-GRE protocol for PPTP */
	PPTP_GRE_IS_C(header->flags) \|\| /* flag C should be clear */
	PPTP_GRE_IS_R(header->flags) \|\| /* flag R should be clear */
	!PPTP_GRE_IS_K(header->flags) \|\| /* flag K should be set */
	(header->flags&0xF) != 0) /* routing and recursion ctrl = 0 */
	/* if invalid, discard this packet */
	goto drop;

	po = lookup_chan(htons(header->call_id), iph->saddr);
	if (po) {
	skb_dst_drop(skb);
	nf_reset(skb);
	return sk_receive_skb(sk_pppox(po), skb, 0);
	}
	drop:
	kfree_skb(skb);
	return NET_RX_DROP;
	}

	static int pptp_bind(struct socket sock, struct sockaddr uservaddr,
	int sockaddr_len)
	{
	struct sock *sk = sock->sk;
	struct sockaddr_pppox sp = (struct sockaddr_pppox ) uservaddr;
	struct pppox_sock *po = pppox_sk(sk);
	struct pptp_opt *opt = &po->proto.pptp;
	int error = 0;

	lock_sock(sk);

	opt->src_addr = sp->sa_addr.pptp;
	if (add_chan(po))
	error = -EBUSY;

	release_sock(sk);
	return error;
	}

	static int pptp_connect(struct socket sock, struct sockaddr uservaddr,
	int sockaddr_len, int flags)
	{
	struct sock *sk = sock->sk;
	struct sockaddr_pppox sp = (struct sockaddr_pppox ) uservaddr;
	struct pppox_sock *po = pppox_sk(sk);
	struct pptp_opt *opt = &po->proto.pptp;
	struct rtable *rt;
	struct flowi4 fl4;
	int error = 0;

	if (sp->sa_protocol != PX_PROTO_PPTP)
	return -EINVAL;

	if (lookup_chan_dst(sp->sa_addr.pptp.call_id, sp->sa_addr.pptp.sin_addr.s_addr))
	return -EALREADY;

	lock_sock(sk);
	/* Check for already bound sockets */
	if (sk->sk_state & PPPOX_CONNECTED) {
	error = -EBUSY;
	goto end;
	}

	/* Check for already disconnected sockets, on attempts to disconnect */
	if (sk->sk_state & PPPOX_DEAD) {
	error = -EALREADY;
	goto end;
	}

	if (!opt->src_addr.sin_addr.s_addr \|\| !sp->sa_addr.pptp.sin_addr.s_addr) {
	error = -EINVAL;
	goto end;
	}

	po->chan.private = sk;
	po->chan.ops = &pptp_chan_ops;

	rt = ip_route_output_ports(&init_net, &fl4, sk,
	opt->dst_addr.sin_addr.s_addr,
	opt->src_addr.sin_addr.s_addr,
	0, 0,
	IPPROTO_GRE, RT_CONN_FLAGS(sk), 0);
	if (IS_ERR(rt)) {
	error = -EHOSTUNREACH;
	goto end;
	}
	sk_setup_caps(sk, &rt->dst);

	po->chan.mtu = dst_mtu(&rt->dst);
	if (!po->chan.mtu)
	po->chan.mtu = PPP_MTU;
	ip_rt_put(rt);
	po->chan.mtu -= PPTP_HEADER_OVERHEAD;

	po->chan.hdrlen = 2 + sizeof(struct pptp_gre_header);
	error = ppp_register_channel(&po->chan);
	if (error) {
	pr_err("PPTP: failed to register PPP channel (%d)\n", error);
	goto end;
	}

	opt->dst_addr = sp->sa_addr.pptp;
	sk->sk_state = PPPOX_CONNECTED;

	end:
	release_sock(sk);
	return error;
	}

	static int pptp_getname(struct socket sock, struct sockaddr uaddr,
	int *usockaddr_len, int peer)
	{
	int len = sizeof(struct sockaddr_pppox);
	struct sockaddr_pppox sp;

	sp.sa_family = AF_PPPOX;
	sp.sa_protocol = PX_PROTO_PPTP;
	sp.sa_addr.pptp = pppox_sk(sock->sk)->proto.pptp.src_addr;

	memcpy(uaddr, &sp, len);

	*usockaddr_len = len;

	return 0;
	}

	static int pptp_release(struct socket *sock)
	{
	struct sock *sk = sock->sk;
	struct pppox_sock *po;
	struct pptp_opt *opt;
	int error = 0;

	if (!sk)
	return 0;

	lock_sock(sk);

	if (sock_flag(sk, SOCK_DEAD)) {
	release_sock(sk);
	return -EBADF;
	}

	po = pppox_sk(sk);
	opt = &po->proto.pptp;
	del_chan(po);

	pppox_unbind_sock(sk);
	sk->sk_state = PPPOX_DEAD;

	sock_orphan(sk);
	sock->sk = NULL;

	release_sock(sk);
	sock_put(sk);

	return error;
	}

	static void pptp_sock_destruct(struct sock *sk)
	{
	if (!(sk->sk_state & PPPOX_DEAD)) {
	del_chan(pppox_sk(sk));
	pppox_unbind_sock(sk);
	}
	skb_queue_purge(&sk->sk_receive_queue);
	}

	static int pptp_create(struct net net, struct socket sock)
	{
	int error = -ENOMEM;
	struct sock *sk;
	struct pppox_sock *po;
	struct pptp_opt *opt;

	sk = sk_alloc(net, PF_PPPOX, GFP_KERNEL, &pptp_sk_proto);
	if (!sk)
	goto out;

	sock_init_data(sock, sk);

	sock->state = SS_UNCONNECTED;
	sock->ops = &pptp_ops;

	sk->sk_backlog_rcv = pptp_rcv_core;
	sk->sk_state = PPPOX_NONE;
	sk->sk_type = SOCK_STREAM;
	sk->sk_family = PF_PPPOX;
	sk->sk_protocol = PX_PROTO_PPTP;
	sk->sk_destruct = pptp_sock_destruct;

	po = pppox_sk(sk);
	opt = &po->proto.pptp;

	opt->seq_sent = 0; opt->seq_recv = 0xffffffff;
	opt->ack_recv = 0; opt->ack_sent = 0xffffffff;

	error = 0;
	out:
	return error;
	}

	static int pptp_ppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
	unsigned long arg)
	{
	struct sock sk = (struct sock ) chan->private;
	struct pppox_sock *po = pppox_sk(sk);
	struct pptp_opt *opt = &po->proto.pptp;
	void __user argp = (void __user )arg;
	int __user *p = argp;
	int err, val;

	err = -EFAULT;
	switch (cmd) {
	case PPPIOCGFLAGS:
	val = opt->ppp_flags;
	if (put_user(val, p))
	break;
	err = 0;
	break;
	case PPPIOCSFLAGS:
	if (get_user(val, p))
	break;
	opt->ppp_flags = val & ~SC_RCV_BITS;
	err = 0;
	break;
	default:
	err = -ENOTTY;
	}

	return err;
	}

	static const struct ppp_channel_ops pptp_chan_ops = {
	.start_xmit = pptp_xmit,
	.ioctl = pptp_ppp_ioctl,
	};

	static struct proto pptp_sk_proto __read_mostly = {
	.name = "PPTP",
	.owner = THIS_MODULE,
	.obj_size = sizeof(struct pppox_sock),
	};

	static const struct proto_ops pptp_ops = {
	.family = AF_PPPOX,
	.owner = THIS_MODULE,
	.release = pptp_release,
	.bind = pptp_bind,
	.connect = pptp_connect,
	.socketpair = sock_no_socketpair,
	.accept = sock_no_accept,
	.getname = pptp_getname,
	.poll = sock_no_poll,
	.listen = sock_no_listen,
	.shutdown = sock_no_shutdown,
	.setsockopt = sock_no_setsockopt,
	.getsockopt = sock_no_getsockopt,
	.sendmsg = sock_no_sendmsg,
	.recvmsg = sock_no_recvmsg,
	.mmap = sock_no_mmap,
	.ioctl = pppox_ioctl,
	};

	static const struct pppox_proto pppox_pptp_proto = {
	.create = pptp_create,
	.owner = THIS_MODULE,
	};

	static const struct gre_protocol gre_pptp_protocol = {
	.handler = pptp_rcv,
	};

	static int __init pptp_init_module(void)
	{
	int err = 0;
	pr_info("PPTP driver version " PPTP_DRIVER_VERSION "\n");

	callid_sock = vzalloc((MAX_CALLID + 1) * sizeof(void *));
	if (!callid_sock) {
	pr_err("PPTP: cann't allocate memory\n");
	return -ENOMEM;
	}

	err = gre_add_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
	if (err) {
	pr_err("PPTP: can't add gre protocol\n");
	goto out_mem_free;
	}

	err = proto_register(&pptp_sk_proto, 0);
	if (err) {
	pr_err("PPTP: can't register sk_proto\n");
	goto out_gre_del_protocol;
	}

	err = register_pppox_proto(PX_PROTO_PPTP, &pppox_pptp_proto);
	if (err) {
	pr_err("PPTP: can't register pppox_proto\n");
	goto out_unregister_sk_proto;
	}

	return 0;

	out_unregister_sk_proto:
	proto_unregister(&pptp_sk_proto);
	out_gre_del_protocol:
	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
	out_mem_free:
	vfree(callid_sock);

	return err;
	}

	static void __exit pptp_exit_module(void)
	{
	unregister_pppox_proto(PX_PROTO_PPTP);
	proto_unregister(&pptp_sk_proto);
	gre_del_protocol(&gre_pptp_protocol, GREPROTO_PPTP);
	vfree(callid_sock);
	}

	module_init(pptp_init_module);
	module_exit(pptp_exit_module);

	MODULE_DESCRIPTION("Point-to-Point Tunneling Protocol");
	MODULE_AUTHOR("D. Kozlov (xeb@mail.ru)");
	MODULE_LICENSE("GPL");