[XFRM]: BEET mode

This patch introduces the BEET mode (Bound End-to-End Tunnel) with as
specified by the ietf draft at the following link:

http://www.ietf.org/internet-drafts/draft-nikander-esp-beet-mode-06.txt

The patch provides only single family support (i.e. inner family =
outer family).

Signed-off-by: Diego Beltrami <diego.beltrami@gmail.com>
Signed-off-by: Miika Komu     <miika@iki.fi>
Signed-off-by: Herbert Xu     <herbert@gondor.apana.org.au>
Signed-off-by: Abhinav Pathak <abhinav.pathak@hiit.fi>
Signed-off-by: Jeff Ahrenholz <ahrenholz@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 139 insertions, 0 deletions

diff --git a/net/ipv4/xfrm4_mode_beet.c b/net/ipv4/xfrm4_mode_beet.c
new file mode 100644
index 0000000..89cf59e
--- /dev/null
+++ b/net/ipv4/xfrm4_mode_beet.c
@@ -0,0 +1,139 @@
+/*
+ * xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
+ *
+ * Copyright (c) 2006 Diego Beltrami <diego.beltrami@gmail.com>
+ *                    Miika Komu     <miika@iki.fi>
+ *                    Herbert Xu     <herbert@gondor.apana.org.au>
+ *                    Abhinav Pathak <abhinav.pathak@hiit.fi>
+ *                    Jeff Ahrenholz <ahrenholz@gmail.com>
+ */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/skbuff.h>
+#include <linux/stringify.h>
+#include <net/dst.h>
+#include <net/ip.h>
+#include <net/xfrm.h>
+
+/* Add encapsulation header.
+ *
+ * The top IP header will be constructed per draft-nikander-esp-beet-mode-06.txt.
+ * The following fields in it shall be filled in by x->type->output:
+ *      tot_len
+ *      check
+ *
+ * On exit, skb->h will be set to the start of the payload to be processed
+ * by x->type->output and skb->nh will be set to the top IP header.
+ */
+static int xfrm4_beet_output(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct iphdr *iph, *top_iph = NULL;
+	int hdrlen, optlen;
+
+	iph = skb->nh.iph;
+	skb->h.ipiph = iph;
+
+	hdrlen = 0;
+	optlen = iph->ihl * 4 - sizeof(*iph);
+	if (unlikely(optlen))
+		hdrlen += IPV4_BEET_PHMAXLEN - (optlen & 4);
+
+	skb->nh.raw = skb_push(skb, x->props.header_len + hdrlen);
+	top_iph = skb->nh.iph;
+	hdrlen = iph->ihl * 4 - optlen;
+	skb->h.raw += hdrlen;
+
+	memmove(top_iph, iph, hdrlen);
+	if (unlikely(optlen)) {
+		struct ip_beet_phdr *ph;
+
+		BUG_ON(optlen < 0);
+
+		ph = (struct ip_beet_phdr *)skb->h.raw;
+		ph->padlen = 4 - (optlen & 4);
+		ph->hdrlen = (optlen + ph->padlen + sizeof(*ph)) / 8;
+		ph->nexthdr = top_iph->protocol;
+
+		top_iph->protocol = IPPROTO_BEETPH;
+		top_iph->ihl = sizeof(struct iphdr) / 4;
+	}
+
+	top_iph->saddr = x->props.saddr.a4;
+	top_iph->daddr = x->id.daddr.a4;
+
+	return 0;
+}
+
+static int xfrm4_beet_input(struct xfrm_state *x, struct sk_buff *skb)
+{
+	struct iphdr *iph = skb->nh.iph;
+	int phlen = 0;
+	int optlen = 0;
+	__u8 ph_nexthdr = 0, protocol = 0;
+	int err = -EINVAL;
+
+	protocol = iph->protocol;
+
+	if (unlikely(iph->protocol == IPPROTO_BEETPH)) {
+		struct ip_beet_phdr *ph = (struct ip_beet_phdr*)(iph + 1);
+
+		if (!pskb_may_pull(skb, sizeof(*ph)))
+			goto out;
+
+		phlen = ph->hdrlen * 8;
+		optlen = phlen - ph->padlen - sizeof(*ph);
+		if (optlen < 0 || optlen & 3 || optlen > 250)
+			goto out;
+
+		if (!pskb_may_pull(skb, phlen))
+			goto out;
+
+		ph_nexthdr = ph->nexthdr;
+	}
+
+	skb_push(skb, sizeof(*iph) - phlen + optlen);
+	memmove(skb->data, skb->nh.raw, sizeof(*iph));
+	skb->nh.raw = skb->data;
+
+	iph = skb->nh.iph;
+	iph->ihl = (sizeof(*iph) + optlen) / 4;
+	iph->tot_len = htons(skb->len);
+	iph->daddr = x->sel.daddr.a4;
+	iph->saddr = x->sel.saddr.a4;
+	if (ph_nexthdr)
+		iph->protocol = ph_nexthdr;
+	else
+		iph->protocol = protocol;
+	iph->check = 0;
+	iph->check = ip_fast_csum(skb->nh.raw, iph->ihl);
+	err = 0;
+out:
+	return err;
+}
+
+static struct xfrm_mode xfrm4_beet_mode = {
+	.input = xfrm4_beet_input,
+	.output = xfrm4_beet_output,
+	.owner = THIS_MODULE,
+	.encap = XFRM_MODE_BEET,
+};
+
+static int __init xfrm4_beet_init(void)
+{
+	return xfrm_register_mode(&xfrm4_beet_mode, AF_INET);
+}
+
+static void __exit xfrm4_beet_exit(void)
+{
+	int err;
+
+	err = xfrm_unregister_mode(&xfrm4_beet_mode, AF_INET);
+	BUG_ON(err);
+}
+
+module_init(xfrm4_beet_init);
+module_exit(xfrm4_beet_exit);
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_XFRM_MODE(AF_INET, XFRM_MODE_BEET);