/*
   * IPV6 GSO/GRO offload support
   * Linux INET implementation
   *
   * Copyright (C) 2016 secunet Security Networks AG
   * Author: Steffen Klassert <steffen.klassert@secunet.com>
   *
   * This program is free software; you can redistribute it and/or modify it
   * under the terms and conditions of the GNU General Public License,
   * version 2, as published by the Free Software Foundation.
   *
   * ESP GRO support
   */
  
  #include <linux/skbuff.h>
  #include <linux/init.h>
  #include <net/protocol.h>
  #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/slab.h>
  #include <linux/spinlock.h>
  #include <net/ip6_route.h>
  #include <net/ipv6.h>
  #include <linux/icmpv6.h>

  static __u16 esp6_nexthdr_esp_offset(struct ipv6hdr *ipv6_hdr, int nhlen)
  {
  	int off = sizeof(struct ipv6hdr);
  	struct ipv6_opt_hdr *exthdr;
  
  	if (likely(ipv6_hdr->nexthdr == NEXTHDR_ESP))
  		return offsetof(struct ipv6hdr, nexthdr);
  
  	while (off < nhlen) {
  		exthdr = (void *)ipv6_hdr + off;
  		if (exthdr->nexthdr == NEXTHDR_ESP)
  			return off;
  
  		off += ipv6_optlen(exthdr);
  	}
  
  	return 0;
  }

  static struct sk_buff **esp6_gro_receive(struct sk_buff **head,
  					 struct sk_buff *skb)
  {
  	int offset = skb_gro_offset(skb);
  	struct xfrm_offload *xo;
  	struct xfrm_state *x;
  	__be32 seq;
  	__be32 spi;

  	int nhoff;

  	int err;

  	if (!pskb_pull(skb, offset))
  		return NULL;

  
  	if ((err = xfrm_parse_spi(skb, IPPROTO_ESP, &spi, &seq)) != 0)
  		goto out;

  	xo = xfrm_offload(skb);
  	if (!xo || !(xo->flags & CRYPTO_DONE)) {
  		err = secpath_set(skb);
  		if (err)
  			goto out;

  		if (skb->sp->len == XFRM_MAX_DEPTH)
  			goto out;

  		x = xfrm_state_lookup(dev_net(skb->dev), skb->mark,
  				      (xfrm_address_t *)&ipv6_hdr(skb)->daddr,
  				      spi, IPPROTO_ESP, AF_INET6);
  		if (!x)
  			goto out;

  		skb->sp->xvec[skb->sp->len++] = x;
  		skb->sp->olen++;

  		xo = xfrm_offload(skb);
  		if (!xo) {
  			xfrm_state_put(x);
  			goto out;
  		}

  	}

  	xo->flags |= XFRM_GRO;

  	nhoff = esp6_nexthdr_esp_offset(ipv6_hdr(skb), offset);
  	if (!nhoff)
  		goto out;
  
  	IP6CB(skb)->nhoff = nhoff;

  	XFRM_TUNNEL_SKB_CB(skb)->tunnel.ip6 = NULL;
  	XFRM_SPI_SKB_CB(skb)->family = AF_INET6;
  	XFRM_SPI_SKB_CB(skb)->daddroff = offsetof(struct ipv6hdr, daddr);
  	XFRM_SPI_SKB_CB(skb)->seq = seq;
  
  	/* We don't need to handle errors from xfrm_input, it does all
  	 * the error handling and frees the resources on error. */
  	xfrm_input(skb, IPPROTO_ESP, spi, -2);
  
  	return ERR_PTR(-EINPROGRESS);
  out:
  	skb_push(skb, offset);
  	NAPI_GRO_CB(skb)->same_flow = 0;
  	NAPI_GRO_CB(skb)->flush = 1;
  
  	return NULL;
  }

  static void esp6_gso_encap(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ip_esp_hdr *esph;
  	struct ipv6hdr *iph = ipv6_hdr(skb);
  	struct xfrm_offload *xo = xfrm_offload(skb);
  	int proto = iph->nexthdr;
  
  	skb_push(skb, -skb_network_offset(skb));
  	esph = ip_esp_hdr(skb);
  	*skb_mac_header(skb) = IPPROTO_ESP;
  
  	esph->spi = x->id.spi;
  	esph->seq_no = htonl(XFRM_SKB_CB(skb)->seq.output.low);
  
  	xo->proto = proto;
  }
  
  static struct sk_buff *esp6_gso_segment(struct sk_buff *skb,
  				        netdev_features_t features)
  {
  	__u32 seq;
  	int err = 0;
  	struct sk_buff *skb2;
  	struct xfrm_state *x;
  	struct ip_esp_hdr *esph;
  	struct crypto_aead *aead;
  	struct sk_buff *segs = ERR_PTR(-EINVAL);
  	netdev_features_t esp_features = features;
  	struct xfrm_offload *xo = xfrm_offload(skb);

  	if (!xo)

  		goto out;

  
  	if (!(skb_shinfo(skb)->gso_type & SKB_GSO_ESP))
  		goto out;

  
  	seq = xo->seq.low;
  
  	x = skb->sp->xvec[skb->sp->len - 1];
  	aead = x->data;
  	esph = ip_esp_hdr(skb);
  
  	if (esph->spi != x->id.spi)
  		goto out;
  
  	if (!pskb_may_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead)))
  		goto out;
  
  	__skb_pull(skb, sizeof(*esph) + crypto_aead_ivsize(aead));
  
  	skb->encap_hdr_csum = 1;
  
  	if (!(features & NETIF_F_HW_ESP))
  		esp_features = features & ~(NETIF_F_SG | NETIF_F_CSUM_MASK);
  
  	segs = x->outer_mode->gso_segment(x, skb, esp_features);
  	if (IS_ERR_OR_NULL(segs))
  		goto out;
  
  	__skb_pull(skb, skb->data - skb_mac_header(skb));
  
  	skb2 = segs;
  	do {
  		struct sk_buff *nskb = skb2->next;
  
  		xo = xfrm_offload(skb2);
  		xo->flags |= XFRM_GSO_SEGMENT;
  		xo->seq.low = seq;
  		xo->seq.hi = xfrm_replay_seqhi(x, seq);
  
  		if(!(features & NETIF_F_HW_ESP))
  			xo->flags |= CRYPTO_FALLBACK;
  
  		x->outer_mode->xmit(x, skb2);
  
  		err = x->type_offload->xmit(x, skb2, esp_features);
  		if (err) {
  			kfree_skb_list(segs);
  			return ERR_PTR(err);
  		}
  
  		if (!skb_is_gso(skb2))
  			seq++;
  		else
  			seq += skb_shinfo(skb2)->gso_segs;
  
  		skb_push(skb2, skb2->mac_len);
  		skb2 = nskb;
  	} while (skb2);
  
  out:
  	return segs;
  }

  static int esp6_input_tail(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct crypto_aead *aead = x->data;

  	struct xfrm_offload *xo = xfrm_offload(skb);

  
  	if (!pskb_may_pull(skb, sizeof(struct ip_esp_hdr) + crypto_aead_ivsize(aead)))
  		return -EINVAL;

  	if (!(xo->flags & CRYPTO_DONE))
  		skb->ip_summed = CHECKSUM_NONE;

  
  	return esp6_input_done2(skb, 0);
  }
  
  static int esp6_xmit(struct xfrm_state *x, struct sk_buff *skb,  netdev_features_t features)
  {
  	int err;
  	int alen;
  	int blksize;
  	struct xfrm_offload *xo;
  	struct ip_esp_hdr *esph;
  	struct crypto_aead *aead;
  	struct esp_info esp;
  	bool hw_offload = true;
  
  	esp.inplace = true;
  
  	xo = xfrm_offload(skb);
  
  	if (!xo)
  		return -EINVAL;

  	if (!(features & NETIF_F_HW_ESP) || !x->xso.offload_handle ||
  	    (x->xso.dev != skb->dev)) {

  		xo->flags |= CRYPTO_FALLBACK;

  		hw_offload = false;

  	}
  
  	esp.proto = xo->proto;
  
  	/* skb is pure payload to encrypt */
  
  	aead = x->data;
  	alen = crypto_aead_authsize(aead);
  
  	esp.tfclen = 0;
  	/* XXX: Add support for tfc padding here. */
  
  	blksize = ALIGN(crypto_aead_blocksize(aead), 4);
  	esp.clen = ALIGN(skb->len + 2 + esp.tfclen, blksize);
  	esp.plen = esp.clen - skb->len - esp.tfclen;
  	esp.tailen = esp.tfclen + esp.plen + alen;
  
  	if (!hw_offload || (hw_offload && !skb_is_gso(skb))) {
  		esp.nfrags = esp6_output_head(x, skb, &esp);
  		if (esp.nfrags < 0)
  			return esp.nfrags;
  	}
  
  	esph = ip_esp_hdr(skb);
  	esph->spi = x->id.spi;
  
  	skb_push(skb, -skb_network_offset(skb));
  
  	if (xo->flags & XFRM_GSO_SEGMENT) {
  		esph->seq_no = htonl(xo->seq.low);
  	} else {
  		int len;
  
  		len = skb->len - sizeof(struct ipv6hdr);
  		if (len > IPV6_MAXPLEN)
  			len = 0;
  
  		ipv6_hdr(skb)->payload_len = htons(len);
  	}

  	if (hw_offload)

  		return 0;
  
  	esp.seqno = cpu_to_be64(xo->seq.low + ((u64)xo->seq.hi << 32));
  
  	err = esp6_output_tail(x, skb, &esp);

  	if (err)

  		return err;
  
  	secpath_reset(skb);
  
  	return 0;
  }

  static const struct net_offload esp6_offload = {
  	.callbacks = {
  		.gro_receive = esp6_gro_receive,

  		.gso_segment = esp6_gso_segment,

  	},
  };

  static const struct xfrm_type_offload esp6_type_offload = {
  	.description	= "ESP6 OFFLOAD",
  	.owner		= THIS_MODULE,
  	.proto	     	= IPPROTO_ESP,
  	.input_tail	= esp6_input_tail,
  	.xmit		= esp6_xmit,

  	.encap		= esp6_gso_encap,

  };

  static int __init esp6_offload_init(void)
  {

  	if (xfrm_register_type_offload(&esp6_type_offload, AF_INET6) < 0) {
  		pr_info("%s: can't add xfrm type offload
  ", __func__);
  		return -EAGAIN;
  	}

  	return inet6_add_offload(&esp6_offload, IPPROTO_ESP);
  }
  
  static void __exit esp6_offload_exit(void)
  {

  	if (xfrm_unregister_type_offload(&esp6_type_offload, AF_INET6) < 0)
  		pr_info("%s: can't remove xfrm type offload
  ", __func__);

  	inet6_del_offload(&esp6_offload, IPPROTO_ESP);
  }
  
  module_init(esp6_offload_init);
  module_exit(esp6_offload_exit);
  MODULE_LICENSE("GPL");
  MODULE_AUTHOR("Steffen Klassert <steffen.klassert@secunet.com>");

  MODULE_ALIAS_XFRM_OFFLOAD_TYPE(AF_INET6, XFRM_PROTO_ESP);