#include <crypto/aead.h>
  #include <crypto/authenc.h>

  #include <linux/err.h>

  #include <linux/module.h>
  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/esp.h>

  #include <linux/scatterlist.h>

  #include <linux/kernel.h>

  #include <linux/pfkeyv2.h>

  #include <linux/rtnetlink.h>
  #include <linux/slab.h>

  #include <linux/spinlock.h>

  #include <linux/in6.h>

  #include <net/icmp.h>

  #include <net/protocol.h>

  #include <net/udp.h>

  struct esp_skb_cb {
  	struct xfrm_skb_cb xfrm;
  	void *tmp;
  };
  
  #define ESP_SKB_CB(__skb) ((struct esp_skb_cb *)&((__skb)->cb[0]))

  static u32 esp4_get_mtu(struct xfrm_state *x, int mtu);

  /*
   * Allocate an AEAD request structure with extra space for SG and IV.
   *
   * For alignment considerations the IV is placed at the front, followed
   * by the request and finally the SG list.
   *
   * TODO: Use spare space in skb for this where possible.
   */

  static void *esp_alloc_tmp(struct crypto_aead *aead, int nfrags, int seqhilen)

  {
  	unsigned int len;

  	len = seqhilen;
  
  	len += crypto_aead_ivsize(aead);

  	if (len) {
  		len += crypto_aead_alignmask(aead) &
  		       ~(crypto_tfm_ctx_alignment() - 1);
  		len = ALIGN(len, crypto_tfm_ctx_alignment());
  	}
  
  	len += sizeof(struct aead_givcrypt_request) + crypto_aead_reqsize(aead);
  	len = ALIGN(len, __alignof__(struct scatterlist));
  
  	len += sizeof(struct scatterlist) * nfrags;
  
  	return kmalloc(len, GFP_ATOMIC);
  }

  static inline __be32 *esp_tmp_seqhi(void *tmp)
  {
  	return PTR_ALIGN((__be32 *)tmp, __alignof__(__be32));
  }
  static inline u8 *esp_tmp_iv(struct crypto_aead *aead, void *tmp, int seqhilen)

  {
  	return crypto_aead_ivsize(aead) ?

  	       PTR_ALIGN((u8 *)tmp + seqhilen,
  			 crypto_aead_alignmask(aead) + 1) : tmp + seqhilen;

  }
  
  static inline struct aead_givcrypt_request *esp_tmp_givreq(
  	struct crypto_aead *aead, u8 *iv)
  {
  	struct aead_givcrypt_request *req;
  
  	req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
  				crypto_tfm_ctx_alignment());
  	aead_givcrypt_set_tfm(req, aead);
  	return req;
  }
  
  static inline struct aead_request *esp_tmp_req(struct crypto_aead *aead, u8 *iv)
  {
  	struct aead_request *req;
  
  	req = (void *)PTR_ALIGN(iv + crypto_aead_ivsize(aead),
  				crypto_tfm_ctx_alignment());
  	aead_request_set_tfm(req, aead);
  	return req;
  }
  
  static inline struct scatterlist *esp_req_sg(struct crypto_aead *aead,
  					     struct aead_request *req)
  {
  	return (void *)ALIGN((unsigned long)(req + 1) +
  			     crypto_aead_reqsize(aead),
  			     __alignof__(struct scatterlist));
  }
  
  static inline struct scatterlist *esp_givreq_sg(
  	struct crypto_aead *aead, struct aead_givcrypt_request *req)
  {
  	return (void *)ALIGN((unsigned long)(req + 1) +
  			     crypto_aead_reqsize(aead),
  			     __alignof__(struct scatterlist));
  }
  
  static void esp_output_done(struct crypto_async_request *base, int err)
  {
  	struct sk_buff *skb = base->data;
  
  	kfree(ESP_SKB_CB(skb)->tmp);
  	xfrm_output_resume(skb, err);
  }

  static int esp_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	int err;

  	struct ip_esp_hdr *esph;

  	struct crypto_aead *aead;
  	struct aead_givcrypt_request *req;
  	struct scatterlist *sg;
  	struct scatterlist *asg;

  	struct esp_data *esp;
  	struct sk_buff *trailer;

  	void *tmp;
  	u8 *iv;

  	u8 *tail;

  	int blksize;
  	int clen;
  	int alen;

  	int plen;
  	int tfclen;

  	int nfrags;

  	int assoclen;
  	int sglists;
  	int seqhilen;
  	__be32 *seqhi;

  	/* skb is pure payload to encrypt */

  
  	err = -ENOMEM;

  	esp = x->data;

  	aead = esp->aead;
  	alen = crypto_aead_authsize(aead);

  	tfclen = 0;
  	if (x->tfcpad) {
  		struct xfrm_dst *dst = (struct xfrm_dst *)skb_dst(skb);
  		u32 padto;
  
  		padto = min(x->tfcpad, esp4_get_mtu(x, dst->child_mtu_cached));
  		if (skb->len < padto)
  			tfclen = padto - skb->len;
  	}

  	blksize = ALIGN(crypto_aead_blocksize(aead), 4);

  	clen = ALIGN(skb->len + 2 + tfclen, blksize);

  	if (esp->padlen)
  		clen = ALIGN(clen, esp->padlen);

  	plen = clen - skb->len - tfclen;

  	err = skb_cow_data(skb, tfclen + plen + alen, &trailer);
  	if (err < 0)

  		goto error;
  	nfrags = err;

  	assoclen = sizeof(*esph);
  	sglists = 1;
  	seqhilen = 0;
  
  	if (x->props.flags & XFRM_STATE_ESN) {
  		sglists += 2;
  		seqhilen += sizeof(__be32);
  		assoclen += seqhilen;
  	}
  
  	tmp = esp_alloc_tmp(aead, nfrags + sglists, seqhilen);

  	if (!tmp)

  		goto error;

  	seqhi = esp_tmp_seqhi(tmp);
  	iv = esp_tmp_iv(aead, tmp, seqhilen);

  	req = esp_tmp_givreq(aead, iv);
  	asg = esp_givreq_sg(aead, req);

  	sg = asg + sglists;

  	/* Fill padding... */

  	tail = skb_tail_pointer(trailer);

  	if (tfclen) {
  		memset(tail, 0, tfclen);
  		tail += tfclen;
  	}

  	do {
  		int i;

  		for (i = 0; i < plen - 2; i++)

  			tail[i] = i + 1;

  	} while (0);

  	tail[plen - 2] = plen - 2;
  	tail[plen - 1] = *skb_mac_header(skb);

  	pskb_put(skb, trailer, clen - skb->len + alen);

  	skb_push(skb, -skb_network_offset(skb));

  	esph = ip_esp_hdr(skb);

  	*skb_mac_header(skb) = IPPROTO_ESP;

  
  	/* this is non-NULL only with UDP Encapsulation */
  	if (x->encap) {
  		struct xfrm_encap_tmpl *encap = x->encap;
  		struct udphdr *uh;

  		__be32 *udpdata32;

  		__be16 sport, dport;

  		int encap_type;
  
  		spin_lock_bh(&x->lock);
  		sport = encap->encap_sport;
  		dport = encap->encap_dport;
  		encap_type = encap->encap_type;
  		spin_unlock_bh(&x->lock);

  
  		uh = (struct udphdr *)esph;

  		uh->source = sport;
  		uh->dest = dport;
  		uh->len = htons(skb->len - skb_transport_offset(skb));

  		uh->check = 0;

  		switch (encap_type) {

  		default:
  		case UDP_ENCAP_ESPINUDP:
  			esph = (struct ip_esp_hdr *)(uh + 1);
  			break;
  		case UDP_ENCAP_ESPINUDP_NON_IKE:

  			udpdata32 = (__be32 *)(uh + 1);

  			udpdata32[0] = udpdata32[1] = 0;
  			esph = (struct ip_esp_hdr *)(udpdata32 + 2);
  			break;
  		}

  		*skb_mac_header(skb) = IPPROTO_UDP;
  	}

  
  	esph->spi = x->id.spi;

  	esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);

  	sg_init_table(sg, nfrags);
  	skb_to_sgvec(skb, sg,
  		     esph->enc_data + crypto_aead_ivsize(aead) - skb->data,
  		     clen + alen);

  
  	if ((x->props.flags & XFRM_STATE_ESN)) {
  		sg_init_table(asg, 3);
  		sg_set_buf(asg, &esph->spi, sizeof(__be32));
  		*seqhi = htonl(XFRM_SKB_CB(skb)->seq.output.hi);
  		sg_set_buf(asg + 1, seqhi, seqhilen);
  		sg_set_buf(asg + 2, &esph->seq_no, sizeof(__be32));
  	} else
  		sg_init_one(asg, esph, sizeof(*esph));

  
  	aead_givcrypt_set_callback(req, 0, esp_output_done, skb);
  	aead_givcrypt_set_crypt(req, sg, sg, clen, iv);

  	aead_givcrypt_set_assoc(req, asg, assoclen);

  	aead_givcrypt_set_giv(req, esph->enc_data,

  			      XFRM_SKB_CB(skb)->seq.output.low);

  
  	ESP_SKB_CB(skb)->tmp = tmp;
  	err = crypto_aead_givencrypt(req);
  	if (err == -EINPROGRESS)
  		goto error;

  	if (err == -EBUSY)
  		err = NET_XMIT_DROP;

  	kfree(tmp);

  error:
  	return err;
  }

  static int esp_input_done2(struct sk_buff *skb, int err)

  {

  	const struct iphdr *iph;

  	struct xfrm_state *x = xfrm_input_state(skb);

  	struct esp_data *esp = x->data;

  	struct crypto_aead *aead = esp->aead;
  	int alen = crypto_aead_authsize(aead);
  	int hlen = sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead);
  	int elen = skb->len - hlen;

  	int ihl;

  	u8 nexthdr[2];

  	int padlen;

  	kfree(ESP_SKB_CB(skb)->tmp);

  	if (unlikely(err))

  		goto out;

  	if (skb_copy_bits(skb, skb->len-alen-2, nexthdr, 2))
  		BUG();

  	err = -EINVAL;

  	padlen = nexthdr[0];

  	if (padlen + 2 + alen >= elen)

  		goto out;

  	/* ... check padding bits here. Silly. :-) */

  	iph = ip_hdr(skb);

  	ihl = iph->ihl * 4;

  	if (x->encap) {
  		struct xfrm_encap_tmpl *encap = x->encap;

  		struct udphdr *uh = (void *)(skb_network_header(skb) + ihl);

  
  		/*
  		 * 1) if the NAT-T peer's IP or port changed then
  		 *    advertize the change to the keying daemon.
  		 *    This is an inbound SA, so just compare
  		 *    SRC ports.
  		 */
  		if (iph->saddr != x->props.saddr.a4 ||
  		    uh->source != encap->encap_sport) {
  			xfrm_address_t ipaddr;
  
  			ipaddr.a4 = iph->saddr;
  			km_new_mapping(x, &ipaddr, uh->source);

  			/* XXX: perhaps add an extra
  			 * policy check here, to see
  			 * if we should allow or
  			 * reject a packet from a
  			 * different source
  			 * address/port.
  			 */

  		}

  		/*
  		 * 2) ignore UDP/TCP checksums in case
  		 *    of NAT-T in Transport Mode, or
  		 *    perform other post-processing fixes
  		 *    as per draft-ietf-ipsec-udp-encaps-06,
  		 *    section 3.1.2
  		 */

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

  			skb->ip_summed = CHECKSUM_UNNECESSARY;

  	}

  	pskb_trim(skb, skb->len - alen - padlen - 2);

  	__skb_pull(skb, hlen);

  	skb_set_transport_header(skb, -ihl);

  	err = nexthdr[1];
  
  	/* RFC4303: Drop dummy packets without any error */
  	if (err == IPPROTO_NONE)
  		err = -EINVAL;
  
  out:
  	return err;
  }
  
  static void esp_input_done(struct crypto_async_request *base, int err)
  {
  	struct sk_buff *skb = base->data;
  
  	xfrm_input_resume(skb, esp_input_done2(skb, err));
  }
  
  /*
   * Note: detecting truncated vs. non-truncated authentication data is very
   * expensive, so we only support truncated data, which is the recommended
   * and common case.
   */
  static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ip_esp_hdr *esph;
  	struct esp_data *esp = x->data;
  	struct crypto_aead *aead = esp->aead;
  	struct aead_request *req;
  	struct sk_buff *trailer;
  	int elen = skb->len - sizeof(*esph) - crypto_aead_ivsize(aead);
  	int nfrags;

  	int assoclen;
  	int sglists;
  	int seqhilen;
  	__be32 *seqhi;

  	void *tmp;
  	u8 *iv;
  	struct scatterlist *sg;
  	struct scatterlist *asg;
  	int err = -EINVAL;

  	if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))

  		goto out;
  
  	if (elen <= 0)
  		goto out;
  
  	if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
  		goto out;
  	nfrags = err;

  	assoclen = sizeof(*esph);
  	sglists = 1;
  	seqhilen = 0;
  
  	if (x->props.flags & XFRM_STATE_ESN) {
  		sglists += 2;
  		seqhilen += sizeof(__be32);
  		assoclen += seqhilen;
  	}

  	err = -ENOMEM;

  	tmp = esp_alloc_tmp(aead, nfrags + sglists, seqhilen);

  	if (!tmp)
  		goto out;
  
  	ESP_SKB_CB(skb)->tmp = tmp;

  	seqhi = esp_tmp_seqhi(tmp);
  	iv = esp_tmp_iv(aead, tmp, seqhilen);

  	req = esp_tmp_req(aead, iv);
  	asg = esp_req_sg(aead, req);

  	sg = asg + sglists;

  
  	skb->ip_summed = CHECKSUM_NONE;
  
  	esph = (struct ip_esp_hdr *)skb->data;
  
  	/* Get ivec. This can be wrong, check against another impls. */
  	iv = esph->enc_data;
  
  	sg_init_table(sg, nfrags);
  	skb_to_sgvec(skb, sg, sizeof(*esph) + crypto_aead_ivsize(aead), elen);

  
  	if ((x->props.flags & XFRM_STATE_ESN)) {
  		sg_init_table(asg, 3);
  		sg_set_buf(asg, &esph->spi, sizeof(__be32));
  		*seqhi = XFRM_SKB_CB(skb)->seq.input.hi;
  		sg_set_buf(asg + 1, seqhi, seqhilen);
  		sg_set_buf(asg + 2, &esph->seq_no, sizeof(__be32));
  	} else
  		sg_init_one(asg, esph, sizeof(*esph));

  
  	aead_request_set_callback(req, 0, esp_input_done, skb);
  	aead_request_set_crypt(req, sg, sg, elen, iv);

  	aead_request_set_assoc(req, asg, assoclen);

  
  	err = crypto_aead_decrypt(req);
  	if (err == -EINPROGRESS)
  		goto out;
  
  	err = esp_input_done2(skb, err);

  
  out:

  	return err;

  }

  static u32 esp4_get_mtu(struct xfrm_state *x, int mtu)

  {
  	struct esp_data *esp = x->data;

  	u32 blksize = ALIGN(crypto_aead_blocksize(esp->aead), 4);
  	u32 align = max_t(u32, blksize, esp->padlen);

  	u32 rem;

  	mtu -= x->props.header_len + crypto_aead_authsize(esp->aead);

  	rem = mtu & (align - 1);
  	mtu &= ~(align - 1);

  
  	switch (x->props.mode) {
  	case XFRM_MODE_TUNNEL:

  		break;
  	default:
  	case XFRM_MODE_TRANSPORT:
  		/* The worst case */

  		mtu -= blksize - 4;
  		mtu += min_t(u32, blksize - 4, rem);

  		break;
  	case XFRM_MODE_BEET:

  		/* The worst case. */

  		mtu += min_t(u32, IPV4_BEET_PHMAXLEN, rem);

  		break;

  	}

  	return mtu - 2;

  }
  
  static void esp4_err(struct sk_buff *skb, u32 info)
  {

  	struct net *net = dev_net(skb->dev);

  	const struct iphdr *iph = (const struct iphdr *)skb->data;

  	struct ip_esp_hdr *esph = (struct ip_esp_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;

  	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  			      esph->spi, IPPROTO_ESP, AF_INET);

  	if (!x)
  		return;

  	NETDEBUG(KERN_DEBUG "pmtu discovery on SA ESP/%08x/%08x
  ",
  		 ntohl(esph->spi), ntohl(iph->daddr));

  	xfrm_state_put(x);
  }
  
  static void esp_destroy(struct xfrm_state *x)
  {
  	struct esp_data *esp = x->data;
  
  	if (!esp)
  		return;

  	crypto_free_aead(esp->aead);

  	kfree(esp);
  }

  static int esp_init_aead(struct xfrm_state *x)

  {

  	struct esp_data *esp = x->data;
  	struct crypto_aead *aead;
  	int err;
  
  	aead = crypto_alloc_aead(x->aead->alg_name, 0, 0);
  	err = PTR_ERR(aead);
  	if (IS_ERR(aead))
  		goto error;
  
  	esp->aead = aead;
  
  	err = crypto_aead_setkey(aead, x->aead->alg_key,
  				 (x->aead->alg_key_len + 7) / 8);
  	if (err)
  		goto error;
  
  	err = crypto_aead_setauthsize(aead, x->aead->alg_icv_len / 8);
  	if (err)
  		goto error;
  
  error:
  	return err;
  }
  
  static int esp_init_authenc(struct xfrm_state *x)
  {
  	struct esp_data *esp = x->data;

  	struct crypto_aead *aead;
  	struct crypto_authenc_key_param *param;
  	struct rtattr *rta;
  	char *key;
  	char *p;
  	char authenc_name[CRYPTO_MAX_ALG_NAME];

  	unsigned int keylen;
  	int err;

  	err = -EINVAL;

  	if (x->ealg == NULL)

  		goto error;

  	err = -ENAMETOOLONG;

  
  	if ((x->props.flags & XFRM_STATE_ESN)) {
  		if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
  			     "authencesn(%s,%s)",
  			     x->aalg ? x->aalg->alg_name : "digest_null",
  			     x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
  			goto error;
  	} else {
  		if (snprintf(authenc_name, CRYPTO_MAX_ALG_NAME,
  			     "authenc(%s,%s)",
  			     x->aalg ? x->aalg->alg_name : "digest_null",
  			     x->ealg->alg_name) >= CRYPTO_MAX_ALG_NAME)
  			goto error;
  	}

  
  	aead = crypto_alloc_aead(authenc_name, 0, 0);
  	err = PTR_ERR(aead);
  	if (IS_ERR(aead))
  		goto error;
  
  	esp->aead = aead;
  
  	keylen = (x->aalg ? (x->aalg->alg_key_len + 7) / 8 : 0) +
  		 (x->ealg->alg_key_len + 7) / 8 + RTA_SPACE(sizeof(*param));
  	err = -ENOMEM;
  	key = kmalloc(keylen, GFP_KERNEL);
  	if (!key)
  		goto error;
  
  	p = key;
  	rta = (void *)p;
  	rta->rta_type = CRYPTO_AUTHENC_KEYA_PARAM;
  	rta->rta_len = RTA_LENGTH(sizeof(*param));
  	param = RTA_DATA(rta);
  	p += RTA_SPACE(sizeof(*param));

  	if (x->aalg) {
  		struct xfrm_algo_desc *aalg_desc;

  		memcpy(p, x->aalg->alg_key, (x->aalg->alg_key_len + 7) / 8);
  		p += (x->aalg->alg_key_len + 7) / 8;

  
  		aalg_desc = xfrm_aalg_get_byname(x->aalg->alg_name, 0);
  		BUG_ON(!aalg_desc);

  		err = -EINVAL;

  		if (aalg_desc->uinfo.auth.icv_fullbits/8 !=

  		    crypto_aead_authsize(aead)) {

  			NETDEBUG(KERN_INFO "ESP: %s digestsize %u != %hu
  ",
  				 x->aalg->alg_name,

  				 crypto_aead_authsize(aead),

  				 aalg_desc->uinfo.auth.icv_fullbits/8);

  			goto free_key;

  		}

  		err = crypto_aead_setauthsize(

  			aead, x->aalg->alg_trunc_len / 8);

  		if (err)
  			goto free_key;

  	}

  	param->enckeylen = cpu_to_be32((x->ealg->alg_key_len + 7) / 8);
  	memcpy(p, x->ealg->alg_key, (x->ealg->alg_key_len + 7) / 8);
  
  	err = crypto_aead_setkey(aead, key, keylen);
  
  free_key:
  	kfree(key);

  error:
  	return err;
  }
  
  static int esp_init_state(struct xfrm_state *x)
  {
  	struct esp_data *esp;
  	struct crypto_aead *aead;
  	u32 align;
  	int err;
  
  	esp = kzalloc(sizeof(*esp), GFP_KERNEL);
  	if (esp == NULL)
  		return -ENOMEM;
  
  	x->data = esp;
  
  	if (x->aead)
  		err = esp_init_aead(x);
  	else
  		err = esp_init_authenc(x);

  	if (err)

  		goto error;

  	aead = esp->aead;
  
  	esp->padlen = 0;

  	x->props.header_len = sizeof(struct ip_esp_hdr) +
  			      crypto_aead_ivsize(aead);

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

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

  	else if (x->props.mode == XFRM_MODE_BEET && x->sel.family != AF_INET6)

  		x->props.header_len += IPV4_BEET_PHMAXLEN;

  	if (x->encap) {
  		struct xfrm_encap_tmpl *encap = x->encap;
  
  		switch (encap->encap_type) {
  		default:
  			goto error;
  		case UDP_ENCAP_ESPINUDP:
  			x->props.header_len += sizeof(struct udphdr);
  			break;
  		case UDP_ENCAP_ESPINUDP_NON_IKE:
  			x->props.header_len += sizeof(struct udphdr) + 2 * sizeof(u32);
  			break;
  		}
  	}

  
  	align = ALIGN(crypto_aead_blocksize(aead), 4);
  	if (esp->padlen)
  		align = max_t(u32, align, esp->padlen);
  	x->props.trailer_len = align + 1 + crypto_aead_authsize(esp->aead);

  
  error:

  	return err;

  }

  static const struct xfrm_type esp_type =

  {
  	.description	= "ESP4",
  	.owner		= THIS_MODULE,
  	.proto	     	= IPPROTO_ESP,

  	.flags		= XFRM_TYPE_REPLAY_PROT,

  	.init_state	= esp_init_state,
  	.destructor	= esp_destroy,

  	.get_mtu	= esp4_get_mtu,

  	.input		= esp_input,

  	.output		= esp_output
  };

  static const struct net_protocol esp4_protocol = {

  	.handler	=	xfrm4_rcv,
  	.err_handler	=	esp4_err,
  	.no_policy	=	1,

  	.netns_ok	=	1,

  };
  
  static int __init esp4_init(void)
  {

  	if (xfrm_register_type(&esp_type, AF_INET) < 0) {
  		printk(KERN_INFO "ip esp init: can't add xfrm type
  ");
  		return -EAGAIN;
  	}
  	if (inet_add_protocol(&esp4_protocol, IPPROTO_ESP) < 0) {
  		printk(KERN_INFO "ip esp init: can't add protocol
  ");
  		xfrm_unregister_type(&esp_type, AF_INET);
  		return -EAGAIN;
  	}
  	return 0;
  }
  
  static void __exit esp4_fini(void)
  {
  	if (inet_del_protocol(&esp4_protocol, IPPROTO_ESP) < 0)
  		printk(KERN_INFO "ip esp close: can't remove protocol
  ");
  	if (xfrm_unregister_type(&esp_type, AF_INET) < 0)
  		printk(KERN_INFO "ip esp close: can't remove xfrm type
  ");
  }
  
  module_init(esp4_init);
  module_exit(esp4_fini);
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_ESP);