/*
   * IP Payload Compression Protocol (IPComp) - RFC3173.
   *
   * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
   * Copyright (c) 2003-2008 Herbert Xu <herbert@gondor.apana.org.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/crypto.h>
  #include <linux/err.h>
  #include <linux/list.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/percpu.h>
  #include <linux/slab.h>
  #include <linux/smp.h>
  #include <linux/vmalloc.h>
  #include <net/ip.h>
  #include <net/ipcomp.h>
  #include <net/xfrm.h>
  
  struct ipcomp_tfms {
  	struct list_head list;
  	struct crypto_comp * __percpu *tfms;
  	int users;
  };
  
  static DEFINE_MUTEX(ipcomp_resource_mutex);
  static void * __percpu *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);
  	int len;
  
  	if (err)
  		goto out;
  
  	if (dlen < (plen + sizeof(struct ip_comp_hdr))) {
  		err = -EINVAL;
  		goto out;
  	}
  
  	len = dlen - plen;
  	if (len > skb_tailroom(skb))
  		len = skb_tailroom(skb);
  
  	__skb_put(skb, len);
  
  	len += plen;
  	skb_copy_to_linear_data(skb, scratch, len);
  
  	while ((scratch += len, dlen -= len) > 0) {
  		skb_frag_t *frag;
  		struct page *page;
  
  		err = -EMSGSIZE;
  		if (WARN_ON(skb_shinfo(skb)->nr_frags >= MAX_SKB_FRAGS))
  			goto out;
  
  		frag = skb_shinfo(skb)->frags + skb_shinfo(skb)->nr_frags;
  		page = alloc_page(GFP_ATOMIC);
  
  		err = -ENOMEM;
  		if (!page)
  			goto out;
  
  		__skb_frag_set_page(frag, page);
  
  		len = PAGE_SIZE;
  		if (dlen < len)
  			len = dlen;
  
  		frag->page_offset = 0;
  		skb_frag_size_set(frag, len);
  		memcpy(skb_frag_address(frag), scratch, len);
  
  		skb->truesize += len;
  		skb->data_len += len;
  		skb->len += len;
  
  		skb_shinfo(skb)->nr_frags++;
  	}
  
  	err = 0;
  
  out:
  	put_cpu();
  	return err;
  }
  
  int ipcomp_input(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int nexthdr;
  	int err = -ENOMEM;
  	struct ip_comp_hdr *ipch;
  
  	if (skb_linearize_cow(skb))
  		goto out;
  
  	skb->ip_summed = CHECKSUM_NONE;
  
  	/* Remove ipcomp header and decompress original payload */
  	ipch = (void *)skb->data;
  	nexthdr = ipch->nexthdr;
  
  	skb->transport_header = skb->network_header + sizeof(*ipch);
  	__skb_pull(skb, sizeof(*ipch));
  	err = ipcomp_decompress(x, skb);
  	if (err)
  		goto out;
  
  	err = nexthdr;
  
  out:
  	return err;
  }
  EXPORT_SYMBOL_GPL(ipcomp_input);
  
  static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ipcomp_data *ipcd = x->data;
  	const int plen = skb->len;
  	int dlen = IPCOMP_SCRATCH_SIZE;
  	u8 *start = skb->data;
  	struct crypto_comp *tfm;
  	u8 *scratch;
  	int err;
  
  	local_bh_disable();
  	scratch = *this_cpu_ptr(ipcomp_scratches);
  	tfm = *this_cpu_ptr(ipcd->tfms);
  	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);
  	local_bh_enable();
  
  	pskb_trim(skb, dlen + sizeof(struct ip_comp_hdr));
  	return 0;
  
  out:
  	local_bh_enable();
  	return err;
  }
  
  int ipcomp_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;
  	struct ip_comp_hdr *ipch;
  	struct ipcomp_data *ipcd = x->data;
  
  	if (skb->len < ipcd->threshold) {
  		/* Don't bother compressing */
  		goto out_ok;
  	}
  
  	if (skb_linearize_cow(skb))
  		goto out_ok;
  
  	err = ipcomp_compress(x, skb);
  
  	if (err) {
  		goto out_ok;
  	}
  
  	/* Install ipcomp header, convert into ipcomp datagram. */
  	ipch = ip_comp_hdr(skb);
  	ipch->nexthdr = *skb_mac_header(skb);
  	ipch->flags = 0;
  	ipch->cpi = htons((u16 )ntohl(x->id.spi));
  	*skb_mac_header(skb) = IPPROTO_COMP;
  out_ok:
  	skb_push(skb, -skb_network_offset(skb));
  	return 0;
  }
  EXPORT_SYMBOL_GPL(ipcomp_output);
  
  static void ipcomp_free_scratches(void)
  {
  	int i;
  	void * __percpu *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 * __percpu *ipcomp_alloc_scratches(void)
  {
  	void * __percpu *scratches;
  	int i;
  
  	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;
  
  		scratch = vmalloc_node(IPCOMP_SCRATCH_SIZE, cpu_to_node(i));
  		if (!scratch)
  			return NULL;
  		*per_cpu_ptr(scratches, i) = scratch;
  	}
  
  	return scratches;
  }
  
  static void ipcomp_free_tfms(struct crypto_comp * __percpu *tfms)
  {
  	struct ipcomp_tfms *pos;
  	int cpu;
  
  	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
  		if (pos->tfms == tfms)
  			break;
  	}
  
  	WARN_ON(!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 * __percpu *ipcomp_alloc_tfms(const char *alg_name)
  {
  	struct ipcomp_tfms *pos;
  	struct crypto_comp * __percpu *tfms;
  	int cpu;
  
  
  	list_for_each_entry(pos, &ipcomp_tfms_list, list) {
  		struct crypto_comp *tfm;
  
  		/* This can be any valid CPU ID so we don't need locking. */
  		tfm = __this_cpu_read(*pos->tfms);
  
  		if (!strcmp(crypto_comp_name(tfm), alg_name)) {
  			pos->users++;
  			return pos->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 (IS_ERR(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();
  }
  
  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);
  }
  EXPORT_SYMBOL_GPL(ipcomp_destroy);
  
  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;
  
  	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);
  
  	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:
  	ipcomp_free_data(ipcd);
  	mutex_unlock(&ipcomp_resource_mutex);
  	kfree(ipcd);
  	goto out;
  }
  EXPORT_SYMBOL_GPL(ipcomp_init_state);
  
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3173");
  MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");