/*
   * File: af_phonet.c
   *
   * Phonet protocols family
   *
   * Copyright (C) 2008 Nokia Corporation.
   *
   * Authors: Sakari Ailus <sakari.ailus@nokia.com>
   *          Rémi Denis-Courmont
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License
   * version 2 as published by the Free Software Foundation.
   *
   * This program is distributed in the hope that it will be useful, but
   * WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * General Public License for more details.
   *
   * You should have received a copy of the GNU General Public License
   * along with this program; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
   * 02110-1301 USA
   */
  
  #include <linux/kernel.h>
  #include <linux/module.h>
  #include <linux/slab.h>
  #include <asm/unaligned.h>
  #include <net/sock.h>
  
  #include <linux/if_phonet.h>
  #include <linux/phonet.h>
  #include <net/phonet/phonet.h>
  #include <net/phonet/pn_dev.h>
  
  /* Transport protocol registration */
  static struct phonet_protocol *proto_tab[PHONET_NPROTO] __read_mostly;
  
  static struct phonet_protocol *phonet_proto_get(unsigned int protocol)
  {
  	struct phonet_protocol *pp;
  
  	if (protocol >= PHONET_NPROTO)
  		return NULL;
  
  	rcu_read_lock();
  	pp = rcu_dereference(proto_tab[protocol]);
  	if (pp && !try_module_get(pp->prot->owner))
  		pp = NULL;
  	rcu_read_unlock();
  
  	return pp;
  }
  
  static inline void phonet_proto_put(struct phonet_protocol *pp)
  {
  	module_put(pp->prot->owner);
  }
  
  /* protocol family functions */
  
  static int pn_socket_create(struct net *net, struct socket *sock, int protocol,
  			    int kern)
  {
  	struct sock *sk;
  	struct pn_sock *pn;
  	struct phonet_protocol *pnp;
  	int err;
  
  	if (!capable(CAP_SYS_ADMIN))
  		return -EPERM;
  
  	if (protocol == 0) {
  		/* Default protocol selection */
  		switch (sock->type) {
  		case SOCK_DGRAM:
  			protocol = PN_PROTO_PHONET;
  			break;
  		case SOCK_SEQPACKET:
  			protocol = PN_PROTO_PIPE;
  			break;
  		default:
  			return -EPROTONOSUPPORT;
  		}
  	}
  
  	pnp = phonet_proto_get(protocol);
  	if (pnp == NULL &&
  	    request_module("net-pf-%d-proto-%d", PF_PHONET, protocol) == 0)
  		pnp = phonet_proto_get(protocol);
  
  	if (pnp == NULL)
  		return -EPROTONOSUPPORT;
  	if (sock->type != pnp->sock_type) {
  		err = -EPROTONOSUPPORT;
  		goto out;
  	}
  
  	sk = sk_alloc(net, PF_PHONET, GFP_KERNEL, pnp->prot);
  	if (sk == NULL) {
  		err = -ENOMEM;
  		goto out;
  	}
  
  	sock_init_data(sock, sk);
  	sock->state = SS_UNCONNECTED;
  	sock->ops = pnp->ops;
  	sk->sk_backlog_rcv = sk->sk_prot->backlog_rcv;
  	sk->sk_protocol = protocol;
  	pn = pn_sk(sk);
  	pn->sobject = 0;
  	pn->dobject = 0;
  	pn->resource = 0;
  	sk->sk_prot->init(sk);
  	err = 0;
  
  out:
  	phonet_proto_put(pnp);
  	return err;
  }
  
  static const struct net_proto_family phonet_proto_family = {
  	.family = PF_PHONET,
  	.create = pn_socket_create,
  	.owner = THIS_MODULE,
  };
  
  /* Phonet device header operations */
  static int pn_header_create(struct sk_buff *skb, struct net_device *dev,
  				unsigned short type, const void *daddr,
  				const void *saddr, unsigned int len)
  {
  	u8 *media = skb_push(skb, 1);
  
  	if (type != ETH_P_PHONET)
  		return -1;
  
  	if (!saddr)
  		saddr = dev->dev_addr;
  	*media = *(const u8 *)saddr;
  	return 1;
  }
  
  static int pn_header_parse(const struct sk_buff *skb, unsigned char *haddr)
  {
  	const u8 *media = skb_mac_header(skb);
  	*haddr = *media;
  	return 1;
  }
  
  struct header_ops phonet_header_ops = {
  	.create = pn_header_create,
  	.parse = pn_header_parse,
  };
  EXPORT_SYMBOL(phonet_header_ops);
  
  /*
   * Prepends an ISI header and sends a datagram.
   */
  static int pn_send(struct sk_buff *skb, struct net_device *dev,
  			u16 dst, u16 src, u8 res, u8 irq)
  {
  	struct phonethdr *ph;
  	int err;
  
  	if (skb->len + 2 > 0xffff /* Phonet length field limit */ ||
  	    skb->len + sizeof(struct phonethdr) > dev->mtu) {
  		err = -EMSGSIZE;
  		goto drop;
  	}
  
  	/* Broadcast sending is not implemented */
  	if (pn_addr(dst) == PNADDR_BROADCAST) {
  		err = -EOPNOTSUPP;
  		goto drop;
  	}
  
  	skb_reset_transport_header(skb);
  	WARN_ON(skb_headroom(skb) & 1); /* HW assumes word alignment */
  	skb_push(skb, sizeof(struct phonethdr));
  	skb_reset_network_header(skb);
  	ph = pn_hdr(skb);
  	ph->pn_rdev = pn_dev(dst);
  	ph->pn_sdev = pn_dev(src);
  	ph->pn_res = res;
  	ph->pn_length = __cpu_to_be16(skb->len + 2 - sizeof(*ph));
  	ph->pn_robj = pn_obj(dst);
  	ph->pn_sobj = pn_obj(src);
  
  	skb->protocol = htons(ETH_P_PHONET);
  	skb->priority = 0;
  	skb->dev = dev;
  
  	if (skb->pkt_type == PACKET_LOOPBACK) {
  		skb_reset_mac_header(skb);
  		skb_orphan(skb);
  		err = (irq ? netif_rx(skb) : netif_rx_ni(skb)) ? -ENOBUFS : 0;
  	} else {
  		err = dev_hard_header(skb, dev, ntohs(skb->protocol),
  					NULL, NULL, skb->len);
  		if (err < 0) {
  			err = -EHOSTUNREACH;
  			goto drop;
  		}
  		err = dev_queue_xmit(skb);
  		if (unlikely(err > 0))
  			err = net_xmit_errno(err);
  	}
  
  	return err;
  drop:
  	kfree_skb(skb);
  	return err;
  }
  
  static int pn_raw_send(const void *data, int len, struct net_device *dev,
  			u16 dst, u16 src, u8 res)
  {
  	struct sk_buff *skb = alloc_skb(MAX_PHONET_HEADER + len, GFP_ATOMIC);
  	if (skb == NULL)
  		return -ENOMEM;
  
  	if (phonet_address_lookup(dev_net(dev), pn_addr(dst)) == 0)
  		skb->pkt_type = PACKET_LOOPBACK;
  
  	skb_reserve(skb, MAX_PHONET_HEADER);
  	__skb_put(skb, len);
  	skb_copy_to_linear_data(skb, data, len);
  	return pn_send(skb, dev, dst, src, res, 1);
  }
  
  /*
   * Create a Phonet header for the skb and send it out. Returns
   * non-zero error code if failed. The skb is freed then.
   */
  int pn_skb_send(struct sock *sk, struct sk_buff *skb,
  		const struct sockaddr_pn *target)
  {
  	struct net *net = sock_net(sk);
  	struct net_device *dev;
  	struct pn_sock *pn = pn_sk(sk);
  	int err;
  	u16 src, dst;
  	u8 daddr, saddr, res;
  
  	src = pn->sobject;
  	if (target != NULL) {
  		dst = pn_sockaddr_get_object(target);
  		res = pn_sockaddr_get_resource(target);
  	} else {
  		dst = pn->dobject;
  		res = pn->resource;
  	}
  	daddr = pn_addr(dst);
  
  	err = -EHOSTUNREACH;
  	if (sk->sk_bound_dev_if)
  		dev = dev_get_by_index(net, sk->sk_bound_dev_if);
  	else if (phonet_address_lookup(net, daddr) == 0) {
  		dev = phonet_device_get(net);
  		skb->pkt_type = PACKET_LOOPBACK;
  	} else if (dst == 0) {
  		/* Resource routing (small race until phonet_rcv()) */
  		struct sock *sk = pn_find_sock_by_res(net, res);
  		if (sk)	{
  			sock_put(sk);
  			dev = phonet_device_get(net);
  			skb->pkt_type = PACKET_LOOPBACK;
  		} else
  			dev = phonet_route_output(net, daddr);
  	} else
  		dev = phonet_route_output(net, daddr);
  
  	if (!dev || !(dev->flags & IFF_UP))
  		goto drop;
  
  	saddr = phonet_address_get(dev, daddr);
  	if (saddr == PN_NO_ADDR)
  		goto drop;
  
  	if (!pn_addr(src))
  		src = pn_object(saddr, pn_obj(src));
  
  	err = pn_send(skb, dev, dst, src, res, 0);
  	dev_put(dev);
  	return err;
  
  drop:
  	kfree_skb(skb);
  	if (dev)
  		dev_put(dev);
  	return err;
  }
  EXPORT_SYMBOL(pn_skb_send);
  
  /* Do not send an error message in response to an error message */
  static inline int can_respond(struct sk_buff *skb)
  {
  	const struct phonethdr *ph;
  	const struct phonetmsg *pm;
  	u8 submsg_id;
  
  	if (!pskb_may_pull(skb, 3))
  		return 0;
  
  	ph = pn_hdr(skb);
  	if (ph->pn_res == PN_PREFIX && !pskb_may_pull(skb, 5))
  		return 0;
  	if (ph->pn_res == PN_COMMGR) /* indications */
  		return 0;
  
  	ph = pn_hdr(skb); /* re-acquires the pointer */
  	pm = pn_msg(skb);
  	if (pm->pn_msg_id != PN_COMMON_MESSAGE)
  		return 1;
  	submsg_id = (ph->pn_res == PN_PREFIX)
  		? pm->pn_e_submsg_id : pm->pn_submsg_id;
  	if (submsg_id != PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP &&
  		pm->pn_e_submsg_id != PN_COMM_SERVICE_NOT_IDENTIFIED_RESP)
  		return 1;
  	return 0;
  }
  
  static int send_obj_unreachable(struct sk_buff *rskb)
  {
  	const struct phonethdr *oph = pn_hdr(rskb);
  	const struct phonetmsg *opm = pn_msg(rskb);
  	struct phonetmsg resp;
  
  	memset(&resp, 0, sizeof(resp));
  	resp.pn_trans_id = opm->pn_trans_id;
  	resp.pn_msg_id = PN_COMMON_MESSAGE;
  	if (oph->pn_res == PN_PREFIX) {
  		resp.pn_e_res_id = opm->pn_e_res_id;
  		resp.pn_e_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
  		resp.pn_e_orig_msg_id = opm->pn_msg_id;
  		resp.pn_e_status = 0;
  	} else {
  		resp.pn_submsg_id = PN_COMM_ISA_ENTITY_NOT_REACHABLE_RESP;
  		resp.pn_orig_msg_id = opm->pn_msg_id;
  		resp.pn_status = 0;
  	}
  	return pn_raw_send(&resp, sizeof(resp), rskb->dev,
  				pn_object(oph->pn_sdev, oph->pn_sobj),
  				pn_object(oph->pn_rdev, oph->pn_robj),
  				oph->pn_res);
  }
  
  static int send_reset_indications(struct sk_buff *rskb)
  {
  	struct phonethdr *oph = pn_hdr(rskb);
  	static const u8 data[4] = {
  		0x00 /* trans ID */, 0x10 /* subscribe msg */,
  		0x00 /* subscription count */, 0x00 /* dummy */
  	};
  
  	return pn_raw_send(data, sizeof(data), rskb->dev,
  				pn_object(oph->pn_sdev, 0x00),
  				pn_object(oph->pn_rdev, oph->pn_robj),
  				PN_COMMGR);
  }
  
  
  /* packet type functions */
  
  /*
   * Stuff received packets to associated sockets.
   * On error, returns non-zero and releases the skb.
   */
  static int phonet_rcv(struct sk_buff *skb, struct net_device *dev,
  			struct packet_type *pkttype,
  			struct net_device *orig_dev)
  {
  	struct net *net = dev_net(dev);
  	struct phonethdr *ph;
  	struct sockaddr_pn sa;
  	u16 len;
  
  	/* check we have at least a full Phonet header */
  	if (!pskb_pull(skb, sizeof(struct phonethdr)))
  		goto out;
  
  	/* check that the advertised length is correct */
  	ph = pn_hdr(skb);
  	len = get_unaligned_be16(&ph->pn_length);
  	if (len < 2)
  		goto out;
  	len -= 2;
  	if ((len > skb->len) || pskb_trim(skb, len))
  		goto out;
  	skb_reset_transport_header(skb);
  
  	pn_skb_get_dst_sockaddr(skb, &sa);
  
  	/* check if this is broadcasted */
  	if (pn_sockaddr_get_addr(&sa) == PNADDR_BROADCAST) {
  		pn_deliver_sock_broadcast(net, skb);
  		goto out;
  	}
  
  	/* resource routing */
  	if (pn_sockaddr_get_object(&sa) == 0) {
  		struct sock *sk = pn_find_sock_by_res(net, sa.spn_resource);
  		if (sk)
  			return sk_receive_skb(sk, skb, 0);
  	}
  
  	/* check if we are the destination */
  	if (phonet_address_lookup(net, pn_sockaddr_get_addr(&sa)) == 0) {
  		/* Phonet packet input */
  		struct sock *sk = pn_find_sock_by_sa(net, &sa);
  
  		if (sk)
  			return sk_receive_skb(sk, skb, 0);
  
  		if (can_respond(skb)) {
  			send_obj_unreachable(skb);
  			send_reset_indications(skb);
  		}
  	} else if (unlikely(skb->pkt_type == PACKET_LOOPBACK))
  		goto out; /* Race between address deletion and loopback */
  	else {
  		/* Phonet packet routing */
  		struct net_device *out_dev;
  
  		out_dev = phonet_route_output(net, pn_sockaddr_get_addr(&sa));
  		if (!out_dev) {
  			LIMIT_NETDEBUG(KERN_WARNING"No Phonet route to %02X
  ",
  					pn_sockaddr_get_addr(&sa));
  			goto out;
  		}
  
  		__skb_push(skb, sizeof(struct phonethdr));
  		skb->dev = out_dev;
  		if (out_dev == dev) {
  			LIMIT_NETDEBUG(KERN_ERR"Phonet loop to %02X on %s
  ",
  					pn_sockaddr_get_addr(&sa), dev->name);
  			goto out_dev;
  		}
  		/* Some drivers (e.g. TUN) do not allocate HW header space */
  		if (skb_cow_head(skb, out_dev->hard_header_len))
  			goto out_dev;
  
  		if (dev_hard_header(skb, out_dev, ETH_P_PHONET, NULL, NULL,
  					skb->len) < 0)
  			goto out_dev;
  		dev_queue_xmit(skb);
  		dev_put(out_dev);
  		return NET_RX_SUCCESS;
  out_dev:
  		dev_put(out_dev);
  	}
  
  out:
  	kfree_skb(skb);
  	return NET_RX_DROP;
  }
  
  static struct packet_type phonet_packet_type __read_mostly = {
  	.type = cpu_to_be16(ETH_P_PHONET),
  	.func = phonet_rcv,
  };
  
  static DEFINE_MUTEX(proto_tab_lock);
  
  int __init_or_module phonet_proto_register(unsigned int protocol,
  						struct phonet_protocol *pp)
  {
  	int err = 0;
  
  	if (protocol >= PHONET_NPROTO)
  		return -EINVAL;
  
  	err = proto_register(pp->prot, 1);
  	if (err)
  		return err;
  
  	mutex_lock(&proto_tab_lock);
  	if (proto_tab[protocol])
  		err = -EBUSY;
  	else
  		rcu_assign_pointer(proto_tab[protocol], pp);
  	mutex_unlock(&proto_tab_lock);
  
  	return err;
  }
  EXPORT_SYMBOL(phonet_proto_register);
  
  void phonet_proto_unregister(unsigned int protocol, struct phonet_protocol *pp)
  {
  	mutex_lock(&proto_tab_lock);
  	BUG_ON(proto_tab[protocol] != pp);
  	RCU_INIT_POINTER(proto_tab[protocol], NULL);
  	mutex_unlock(&proto_tab_lock);
  	synchronize_rcu();
  	proto_unregister(pp->prot);
  }
  EXPORT_SYMBOL(phonet_proto_unregister);
  
  /* Module registration */
  static int __init phonet_init(void)
  {
  	int err;
  
  	err = phonet_device_init();
  	if (err)
  		return err;
  
  	pn_sock_init();
  	err = sock_register(&phonet_proto_family);
  	if (err) {
  		printk(KERN_ALERT
  			"phonet protocol family initialization failed
  ");
  		goto err_sock;
  	}
  
  	dev_add_pack(&phonet_packet_type);
  	phonet_sysctl_init();
  
  	err = isi_register();
  	if (err)
  		goto err;
  	return 0;
  
  err:
  	phonet_sysctl_exit();
  	sock_unregister(PF_PHONET);
  	dev_remove_pack(&phonet_packet_type);
  err_sock:
  	phonet_device_exit();
  	return err;
  }
  
  static void __exit phonet_exit(void)
  {
  	isi_unregister();
  	phonet_sysctl_exit();
  	sock_unregister(PF_PHONET);
  	dev_remove_pack(&phonet_packet_type);
  	phonet_device_exit();
  }
  
  module_init(phonet_init);
  module_exit(phonet_exit);
  MODULE_DESCRIPTION("Phonet protocol stack for Linux");
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_NETPROTO(PF_PHONET);