1/*
  2 * xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
  3 *
  4 * Copyright (c) 2006 Diego Beltrami <diego.beltrami@gmail.com>
  5 *                    Miika Komu     <miika@iki.fi>
  6 *                    Herbert Xu     <herbert@gondor.apana.org.au>
  7 *                    Abhinav Pathak <abhinav.pathak@hiit.fi>
  8 *                    Jeff Ahrenholz <ahrenholz@gmail.com>
  9 */
 10
 11#include <linux/init.h>
 12#include <linux/kernel.h>
 13#include <linux/module.h>
 14#include <linux/skbuff.h>
 15#include <linux/stringify.h>
 16#include <net/dst.h>
 17#include <net/ip.h>
 18#include <net/xfrm.h>
 19
 20static void xfrm4_beet_make_header(struct sk_buff *skb)
 21{
 22	struct iphdr *iph = ip_hdr(skb);
 23
 24	iph->ihl = 5;
 25	iph->version = 4;
 26
 27	iph->protocol = XFRM_MODE_SKB_CB(skb)->protocol;
 28	iph->tos = XFRM_MODE_SKB_CB(skb)->tos;
 29
 30	iph->id = XFRM_MODE_SKB_CB(skb)->id;
 31	iph->frag_off = XFRM_MODE_SKB_CB(skb)->frag_off;
 32	iph->ttl = XFRM_MODE_SKB_CB(skb)->ttl;
 33}
 34
 35/* Add encapsulation header.
 36 *
 37 * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
 38 */
 39static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
 40{
 41	struct ip_beet_phdr *ph;
 42	struct iphdr *top_iph;
 43	int hdrlen, optlen;
 44
 45	hdrlen = 0;
 46	optlen = XFRM_MODE_SKB_CB(skb)->optlen;
 47	if (unlikely(optlen))
 48		hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
 49
 50	skb_set_network_header(skb, -x->props.header_len -
 51				    hdrlen + (XFRM_MODE_SKB_CB(skb)->ihl - sizeof(*top_iph)));
 52	if (x->sel.family != AF_INET6)
 53		skb->network_header += IPV4_BEET_PHMAXLEN;
 54	skb->mac_header = skb->network_header +
 55			  offsetof(struct iphdr, protocol);
 56	skb->transport_header = skb->network_header + sizeof(*top_iph);
 57
 58	xfrm4_beet_make_header(skb);
 59
 60	ph = (struct ip_beet_phdr *)
 61		__skb_pull(skb, XFRM_MODE_SKB_CB(skb)->ihl - hdrlen);
 62
 63	top_iph = ip_hdr(skb);
 64
 65	if (unlikely(optlen)) {
 66		BUG_ON(optlen < 0);
 67
 68		ph->padlen = 4 - (optlen & 4);
 69		ph->hdrlen = optlen / 8;
 70		ph->nexthdr = top_iph->protocol;
 71		if (ph->padlen)
 72			memset(ph + 1, IPOPT_NOP, ph->padlen);
 73
 74		top_iph->protocol = IPPROTO_BEETPH;
 75		top_iph->ihl = sizeof(struct iphdr) / 4;
 76	}
 77
 78	top_iph->saddr = x->props.saddr.a4;
 79	top_iph->daddr = x->id.daddr.a4;
 80
 81	return 0;
 82}
 83
 84static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
 85{
 86	struct iphdr *iph;
 87	int optlen = 0;
 88	int err = -EINVAL;
 89
 90	if (unlikely(XFRM_MODE_SKB_CB(skb)->protocol == IPPROTO_BEETPH)) {
 91		struct ip_beet_phdr *ph;
 92		int phlen;
 93
 94		if (!pskb_may_pull(skb, sizeof(*ph)))
 95			goto out;
 96
 97		ph = (struct ip_beet_phdr *)skb->data;
 98
 99		phlen = sizeof(*ph) + ph->padlen;
100		optlen = ph->hdrlen * 8 + (IPV4_BEET_PHMAXLEN - phlen);
101		if (optlen < 0 || optlen & 3 || optlen > 250)
102			goto out;
103
104		XFRM_MODE_SKB_CB(skb)->protocol = ph->nexthdr;
105
106		if (!pskb_may_pull(skb, phlen))
107			goto out;
108		__skb_pull(skb, phlen);
109	}
110
111	skb_push(skb, sizeof(*iph));
112	skb_reset_network_header(skb);
113	skb_mac_header_rebuild(skb);
114
115	xfrm4_beet_make_header(skb);
116
117	iph = ip_hdr(skb);
118
119	iph->ihl += optlen / 4;
120	iph->tot_len = htons(skb->len);
121	iph->daddr = x->sel.daddr.a4;
122	iph->saddr = x->sel.saddr.a4;
123	iph->check = 0;
124	iph->check = ip_fast_csum(skb_network_header(skb), iph->ihl);
125	err = 0;
126out:
127	return err;
128}
129
130static struct xfrm_mode xfrm4_beet_mode = {
131	.input2 = xfrm4_beet_input,
132	.input = xfrm_prepare_input,
133	.output2 = xfrm4_beet_output,
134	.output = xfrm4_prepare_output,
135	.owner = THIS_MODULE,
136	.encap = XFRM_MODE_BEET,
137	.flags = XFRM_MODE_FLAG_TUNNEL,
138};
139
140static int __init xfrm4_beet_init(void)
141{
142	return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
143}
144
145static void __exit xfrm4_beet_exit(void)
146{
147	int err;
148
149	err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
150	BUG_ON(err);
151}
152
153module_init(xfrm4_beet_init);
154module_exit(xfrm4_beet_exit);
155MODULE_LICENSE("GPL");
156MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);