/*
   * IP Payload Compression Protocol (IPComp) - RFC3173.
   *
   * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   *
   * 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.
   *
   * Todo:
   *   - Tunable compression parameters.
   *   - Compression stats.
   *   - Adaptive compression.
   */

  #include <linux/module.h>
  #include <asm/scatterlist.h>
  #include <asm/semaphore.h>
  #include <linux/crypto.h>
  #include <linux/pfkeyv2.h>
  #include <linux/percpu.h>
  #include <linux/smp.h>
  #include <linux/list.h>
  #include <linux/vmalloc.h>
  #include <linux/rtnetlink.h>

  #include <linux/mutex.h>

  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/icmp.h>
  #include <net/ipcomp.h>

  #include <net/protocol.h>

  
  struct ipcomp_tfms {
  	struct list_head list;

  	struct crypto_comp **tfms;

  	int users;
  };

  static DEFINE_MUTEX(ipcomp_resource_mutex);

  static void **ipcomp_scratches;
  static int ipcomp_scratch_users;
  static LIST_HEAD(ipcomp_tfms_list);
  
  static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
  {

  	struct ipcomp_data *ipcd = x->data;

  	const int plen = skb->len;
  	int dlen = IPCOMP_SCRATCH_SIZE;
  	const u8 *start = skb->data;
  	const int cpu = get_cpu();
  	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
  	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
  	int err = crypto_comp_decompress(tfm, start, plen, scratch, &dlen);

  	if (err)
  		goto out;
  
  	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
  		err = -EINVAL;
  		goto out;
  	}
  
  	err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
  	if (err)
  		goto out;

  	skb->truesize += dlen - plen;
  	__skb_put(skb, dlen - plen);

  	skb_copy_to_linear_data(skb, scratch, dlen);

  out:

  	put_cpu();
  	return err;
  }

  static int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)

  {

  	int err = -ENOMEM;

  	struct iphdr *iph;

  	struct ip_comp_hdr *ipch;

  	if (skb_linearize_cow(skb))

  		goto out;

  
  	skb->ip_summed = CHECKSUM_NONE;

  	/* Remove ipcomp header and decompress original payload */

  	iph = ip_hdr(skb);

  	ipch = (void *)skb->data;
  	iph->protocol = ipch->nexthdr;

  	skb->transport_header = skb->network_header + sizeof(*ipch);

  	__skb_pull(skb, sizeof(*ipch));

  	err = ipcomp_decompress(x, skb);

  out:

  	return err;
  }
  
  static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
  {

  	struct ipcomp_data *ipcd = x->data;

  	const int ihlen = ip_hdrlen(skb);
  	const int plen = skb->len - ihlen;
  	int dlen = IPCOMP_SCRATCH_SIZE;
  	u8 *start = skb->data + ihlen;
  	const int cpu = get_cpu();
  	u8 *scratch = *per_cpu_ptr(ipcomp_scratches, cpu);
  	struct crypto_comp *tfm = *per_cpu_ptr(ipcd->tfms, cpu);
  	int err = crypto_comp_compress(tfm, start, plen, scratch, &dlen);

  	if (err)
  		goto out;
  
  	if ((dlen + sizeof(struct ip_comp_hdr)) >= plen) {
  		err = -EMSGSIZE;
  		goto out;
  	}

  	memcpy(start + sizeof(struct ip_comp_hdr), scratch, dlen);
  	put_cpu();
  
  	pskb_trim(skb, ihlen + dlen + sizeof(struct ip_comp_hdr));
  	return 0;

  
  out:

  	put_cpu();
  	return err;
  }
  
  static int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;

  	struct ip_comp_hdr *ipch;
  	struct ipcomp_data *ipcd = x->data;
  	int hdr_len = 0;

  	struct iphdr *iph = ip_hdr(skb);

  	iph->tot_len = htons(skb->len);
  	hdr_len = iph->ihl * 4;
  	if ((skb->len - hdr_len) < ipcd->threshold) {
  		/* Don't bother compressing */
  		goto out_ok;
  	}

  	if (skb_linearize_cow(skb))

  		goto out_ok;

  	err = ipcomp_compress(x, skb);

  	iph = ip_hdr(skb);

  
  	if (err) {
  		goto out_ok;
  	}
  
  	/* Install ipcomp header, convert into ipcomp datagram. */
  	iph->tot_len = htons(skb->len);
  	ipch = (struct ip_comp_hdr *)((char *)iph + iph->ihl * 4);
  	ipch->nexthdr = iph->protocol;
  	ipch->flags = 0;
  	ipch->cpi = htons((u16 )ntohl(x->id.spi));
  	iph->protocol = IPPROTO_COMP;
  	ip_send_check(iph);
  	return 0;
  
  out_ok:

  	if (x->props.mode == XFRM_MODE_TUNNEL)

  		ip_send_check(iph);
  	return 0;
  }
  
  static void ipcomp4_err(struct sk_buff *skb, u32 info)
  {

  	__be32 spi;

  	struct iphdr *iph = (struct iphdr *)skb->data;
  	struct ip_comp_hdr *ipch = (struct ip_comp_hdr *)(skb->data+(iph->ihl<<2));
  	struct xfrm_state *x;

  	if (icmp_hdr(skb)->type != ICMP_DEST_UNREACH ||
  	    icmp_hdr(skb)->code != ICMP_FRAG_NEEDED)

  		return;

  	spi = htonl(ntohs(ipch->cpi));

  	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,

  			      spi, IPPROTO_COMP, AF_INET);

  	if (!x)
  		return;

  	NETDEBUG(KERN_DEBUG "pmtu discovery on SA IPCOMP/%08x/%u.%u.%u.%u
  ",
  		 spi, NIPQUAD(iph->daddr));

  	xfrm_state_put(x);
  }

  /* We always hold one tunnel user reference to indicate a tunnel */

  static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
  {
  	struct xfrm_state *t;

  	u8 mode = XFRM_MODE_TUNNEL;

  	t = xfrm_state_alloc();
  	if (t == NULL)
  		goto out;
  
  	t->id.proto = IPPROTO_IPIP;
  	t->id.spi = x->props.saddr.a4;
  	t->id.daddr.a4 = x->id.daddr.a4;
  	memcpy(&t->sel, &x->sel, sizeof(t->sel));
  	t->props.family = AF_INET;

  	if (x->props.mode == XFRM_MODE_BEET)
  		mode = x->props.mode;
  	t->props.mode = mode;

  	t->props.saddr.a4 = x->props.saddr.a4;
  	t->props.flags = x->props.flags;

  
  	if (xfrm_init_state(t))

  		goto error;

  	atomic_set(&t->tunnel_users, 1);
  out:
  	return t;
  
  error:
  	t->km.state = XFRM_STATE_DEAD;
  	xfrm_state_put(t);
  	t = NULL;
  	goto out;
  }
  
  /*

   * Must be protected by xfrm_cfg_mutex.  State and tunnel user references are

   * always incremented on success.
   */
  static int ipcomp_tunnel_attach(struct xfrm_state *x)
  {
  	int err = 0;
  	struct xfrm_state *t;
  
  	t = xfrm_state_lookup((xfrm_address_t *)&x->id.daddr.a4,

  			      x->props.saddr.a4, IPPROTO_IPIP, AF_INET);

  	if (!t) {
  		t = ipcomp_tunnel_create(x);
  		if (!t) {
  			err = -EINVAL;
  			goto out;
  		}
  		xfrm_state_insert(t);
  		xfrm_state_hold(t);
  	}
  	x->tunnel = t;
  	atomic_inc(&t->tunnel_users);
  out:
  	return err;
  }
  
  static void ipcomp_free_scratches(void)
  {
  	int i;
  	void **scratches;
  
  	if (--ipcomp_scratch_users)
  		return;
  
  	scratches = ipcomp_scratches;
  	if (!scratches)
  		return;

  	for_each_possible_cpu(i)
  		vfree(*per_cpu_ptr(scratches, i));

  
  	free_percpu(scratches);
  }
  
  static void **ipcomp_alloc_scratches(void)
  {
  	int i;
  	void **scratches;
  
  	if (ipcomp_scratch_users++)
  		return ipcomp_scratches;
  
  	scratches = alloc_percpu(void *);
  	if (!scratches)
  		return NULL;
  
  	ipcomp_scratches = scratches;

  	for_each_possible_cpu(i) {

  		void *scratch = vmalloc(IPCOMP_SCRATCH_SIZE);
  		if (!scratch)
  			return NULL;
  		*per_cpu_ptr(scratches, i) = scratch;
  	}
  
  	return scratches;
  }

  static void ipcomp_free_tfms(struct crypto_comp **tfms)

  {
  	struct ipcomp_tfms *pos;
  	int cpu;
  
  	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
  		if (pos->tfms == tfms)
  			break;
  	}
  
  	BUG_TRAP(pos);
  
  	if (--pos->users)
  		return;
  
  	list_del(&pos->list);
  	kfree(pos);
  
  	if (!tfms)
  		return;

  	for_each_possible_cpu(cpu) {

  		struct crypto_comp *tfm = *per_cpu_ptr(tfms, cpu);
  		crypto_free_comp(tfm);

  	}
  	free_percpu(tfms);
  }

  static struct crypto_comp **ipcomp_alloc_tfms(const char *alg_name)

  {
  	struct ipcomp_tfms *pos;

  	struct crypto_comp **tfms;

  	int cpu;
  
  	/* This can be any valid CPU ID so we don't need locking. */

  	cpu = raw_smp_processor_id();

  
  	list_for_each_entry(pos, &ipcomp_tfms_list, list) {

  		struct crypto_comp *tfm;

  
  		tfms = pos->tfms;
  		tfm = *per_cpu_ptr(tfms, cpu);

  		if (!strcmp(crypto_comp_name(tfm), alg_name)) {

  			pos->users++;
  			return tfms;
  		}
  	}
  
  	pos = kmalloc(sizeof(*pos), GFP_KERNEL);
  	if (!pos)
  		return NULL;
  
  	pos->users = 1;
  	INIT_LIST_HEAD(&pos->list);
  	list_add(&pos->list, &ipcomp_tfms_list);

  	pos->tfms = tfms = alloc_percpu(struct crypto_comp *);

  	if (!tfms)
  		goto error;

  	for_each_possible_cpu(cpu) {

  		struct crypto_comp *tfm = crypto_alloc_comp(alg_name, 0,
  							    CRYPTO_ALG_ASYNC);

  		if (!tfm)
  			goto error;
  		*per_cpu_ptr(tfms, cpu) = tfm;
  	}
  
  	return tfms;
  
  error:
  	ipcomp_free_tfms(tfms);
  	return NULL;
  }
  
  static void ipcomp_free_data(struct ipcomp_data *ipcd)
  {
  	if (ipcd->tfms)
  		ipcomp_free_tfms(ipcd->tfms);
  	ipcomp_free_scratches();
  }
  
  static void ipcomp_destroy(struct xfrm_state *x)
  {
  	struct ipcomp_data *ipcd = x->data;
  	if (!ipcd)
  		return;
  	xfrm_state_delete_tunnel(x);

  	mutex_lock(&ipcomp_resource_mutex);

  	ipcomp_free_data(ipcd);

  	mutex_unlock(&ipcomp_resource_mutex);

  	kfree(ipcd);
  }

  static int ipcomp_init_state(struct xfrm_state *x)

  {
  	int err;
  	struct ipcomp_data *ipcd;
  	struct xfrm_algo_desc *calg_desc;
  
  	err = -EINVAL;
  	if (!x->calg)
  		goto out;
  
  	if (x->encap)
  		goto out;
  
  	err = -ENOMEM;

  	ipcd = kzalloc(sizeof(*ipcd), GFP_KERNEL);

  	if (!ipcd)
  		goto out;

  	x->props.header_len = 0;

  	if (x->props.mode == XFRM_MODE_TUNNEL)

  		x->props.header_len += sizeof(struct iphdr);

  	mutex_lock(&ipcomp_resource_mutex);

  	if (!ipcomp_alloc_scratches())
  		goto error;
  
  	ipcd->tfms = ipcomp_alloc_tfms(x->calg->alg_name);
  	if (!ipcd->tfms)
  		goto error;

  	mutex_unlock(&ipcomp_resource_mutex);

  	if (x->props.mode == XFRM_MODE_TUNNEL) {

  		err = ipcomp_tunnel_attach(x);
  		if (err)
  			goto error_tunnel;
  	}
  
  	calg_desc = xfrm_calg_get_byname(x->calg->alg_name, 0);
  	BUG_ON(!calg_desc);
  	ipcd->threshold = calg_desc->uinfo.comp.threshold;
  	x->data = ipcd;
  	err = 0;
  out:
  	return err;
  
  error_tunnel:

  	mutex_lock(&ipcomp_resource_mutex);

  error:
  	ipcomp_free_data(ipcd);

  	mutex_unlock(&ipcomp_resource_mutex);

  	kfree(ipcd);
  	goto out;
  }
  
  static struct xfrm_type ipcomp_type = {
  	.description	= "IPCOMP4",
  	.owner		= THIS_MODULE,
  	.proto	     	= IPPROTO_COMP,
  	.init_state	= ipcomp_init_state,
  	.destructor	= ipcomp_destroy,
  	.input		= ipcomp_input,
  	.output		= ipcomp_output
  };
  
  static struct net_protocol ipcomp4_protocol = {
  	.handler	=	xfrm4_rcv,
  	.err_handler	=	ipcomp4_err,
  	.no_policy	=	1,
  };
  
  static int __init ipcomp4_init(void)
  {
  	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
  		printk(KERN_INFO "ipcomp init: can't add xfrm type
  ");
  		return -EAGAIN;
  	}
  	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
  		printk(KERN_INFO "ipcomp init: can't add protocol
  ");
  		xfrm_unregister_type(&ipcomp_type, AF_INET);
  		return -EAGAIN;
  	}
  	return 0;
  }
  
  static void __exit ipcomp4_fini(void)
  {
  	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
  		printk(KERN_INFO "ip ipcomp close: can't remove protocol
  ");
  	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
  		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type
  ");
  }
  
  module_init(ipcomp4_init);
  module_exit(ipcomp4_fini);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
  MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");

  MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_COMP);