[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 <[email protected]>
Signed-off-by: Miika Komu     <[email protected]>
Signed-off-by: Herbert Xu     <[email protected]>
Signed-off-by: Abhinav Pathak <[email protected]>
Signed-off-by: Jeff Ahrenholz <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

include/linux/in.h

@@ -40,6 +40,7 @@ enum {
 
   IPPROTO_ESP = 50,            /* Encapsulation Security Payload protocol */
   IPPROTO_AH = 51,             /* Authentication Header protocol       */
+  IPPROTO_BEETPH = 94,	       /* IP option pseudo header for BEET */
   IPPROTO_PIM    = 103,		/* Protocol Independent Multicast	*/
 
   IPPROTO_COMP   = 108,                /* Compression Header protocol */

include/linux/ip.h

@@ -80,6 +80,8 @@
 #define	IPOPT_TS_TSANDADDR	1		/* timestamps and addresses */
 #define	IPOPT_TS_PRESPEC	3		/* specified modules only */
 
+#define IPV4_BEET_PHMAXLEN 8
+
 struct iphdr {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	__u8	ihl:4,
@@ -123,4 +125,11 @@ struct ip_comp_hdr {
 	__be16 cpi;
 };
 
+struct ip_beet_phdr {
+	__u8 nexthdr;
+	__u8 hdrlen;
+	__u8 padlen;
+	__u8 reserved;
+};
+
 #endif	/* _LINUX_IP_H */

include/linux/ipsec.h

@@ -12,7 +12,8 @@
 enum {
 	IPSEC_MODE_ANY		= 0,	/* We do not support this for SA */
 	IPSEC_MODE_TRANSPORT	= 1,
-	IPSEC_MODE_TUNNEL	= 2
+	IPSEC_MODE_TUNNEL	= 2,
+	IPSEC_MODE_BEET         = 3
 };
 
 enum {

include/linux/xfrm.h

@@ -129,7 +129,8 @@ enum
 #define XFRM_MODE_TUNNEL 1
 #define XFRM_MODE_ROUTEOPTIMIZATION 2
 #define XFRM_MODE_IN_TRIGGER 3
-#define XFRM_MODE_MAX 4
+#define XFRM_MODE_BEET 4
+#define XFRM_MODE_MAX 5
 
 /* Netlink configuration messages.  */
 enum {

net/ipv4/Kconfig

@@ -434,6 +434,15 @@ config INET_XFRM_MODE_TUNNEL
 
 	  If unsure, say Y.
 
+config INET_XFRM_MODE_BEET
+	tristate "IP: IPsec BEET mode"
+	default y
+	select XFRM
+	---help---
+	  Support for IPsec BEET mode.
+
+	  If unsure, say Y.
+
 config INET_DIAG
 	tristate "INET: socket monitoring interface"
 	default y

net/ipv4/Makefile

@@ -23,6 +23,7 @@ obj-$(CONFIG_INET_AH) += ah4.o
 obj-$(CONFIG_INET_ESP) += esp4.o
 obj-$(CONFIG_INET_IPCOMP) += ipcomp.o
 obj-$(CONFIG_INET_XFRM_TUNNEL) += xfrm4_tunnel.o
+obj-$(CONFIG_INET_XFRM_MODE_BEET) += xfrm4_mode_beet.o
 obj-$(CONFIG_INET_TUNNEL) += tunnel4.o
 obj-$(CONFIG_INET_XFRM_MODE_TRANSPORT) += xfrm4_mode_transport.o
 obj-$(CONFIG_INET_XFRM_MODE_TUNNEL) += xfrm4_mode_tunnel.o

net/ipv4/esp4.c

@@ -253,7 +253,8 @@ static int esp_input(struct xfrm_state *x, struct sk_buff *skb)
 		 *    as per draft-ietf-ipsec-udp-encaps-06,
 		 *    section 3.1.2
 		 */
-		if (x->props.mode == XFRM_MODE_TRANSPORT)
+		if (x->props.mode == XFRM_MODE_TRANSPORT ||
+		    x->props.mode == XFRM_MODE_BEET)
 			skb->ip_summed = CHECKSUM_UNNECESSARY;
 	}
 
@@ -271,17 +272,28 @@ static u32 esp4_get_max_size(struct xfrm_state *x, int mtu)
 {
 	struct esp_data *esp = x->data;
 	u32 blksize = ALIGN(crypto_blkcipher_blocksize(esp->conf.tfm), 4);
-
-	if (x->props.mode == XFRM_MODE_TUNNEL) {
-		mtu = ALIGN(mtu + 2, blksize);
-	} else {
-		/* The worst case. */
+	int enclen = 0;
+
+	switch (x->props.mode) {
+	case XFRM_MODE_TUNNEL:
+		mtu = ALIGN(mtu +2, blksize);
+		break;
+	default:
+	case XFRM_MODE_TRANSPORT:
+		/* The worst case */
 		mtu = ALIGN(mtu + 2, 4) + blksize - 4;
+		break;
+	case XFRM_MODE_BEET:
+ 		/* The worst case. */
+		enclen = IPV4_BEET_PHMAXLEN;
+		mtu = ALIGN(mtu + enclen + 2, blksize);
+		break;
 	}
+
 	if (esp->conf.padlen)
 		mtu = ALIGN(mtu, esp->conf.padlen);
 
-	return mtu + x->props.header_len + esp->auth.icv_trunc_len;
+	return mtu + x->props.header_len + esp->auth.icv_trunc_len - enclen;
 }
 
 static void esp4_err(struct sk_buff *skb, u32 info)

net/ipv4/ipcomp.c

@@ -206,6 +206,7 @@ static void ipcomp4_err(struct sk_buff *skb, u32 info)
 static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 {
 	struct xfrm_state *t;
+	u8 mode = XFRM_MODE_TUNNEL;
 
 	t = xfrm_state_alloc();
 	if (t == NULL)
@@ -216,7 +217,9 @@ static struct xfrm_state *ipcomp_tunnel_create(struct xfrm_state *x)
 	t->id.daddr.a4 = x->id.daddr.a4;
 	memcpy(&t->sel, &x->sel, sizeof(t->sel));
 	t->props.family = AF_INET;
-	t->props.mode = XFRM_MODE_TUNNEL;
+	if (x->props.mode == XFRM_MODE_BEET)
+		mode = x->props.mode;
+	t->props.mode = mode;
 	t->props.saddr.a4 = x->props.saddr.a4;
 	t->props.flags = x->props.flags;
 

net/ipv4/xfrm4_mode_beet.c

@@ -0,0 +1,139 @@
+/*
+ * xfrm4_mode_beet.c - BEET mode encapsulation for IPv4.
+ *
+ * Copyright (c) 2006 Diego Beltrami <[email protected]>
+ *                    Miika Komu     <[email protected]>
+ *                    Herbert Xu     <[email protected]>
+ *                    Abhinav Pathak <[email protected]>
+ *                    Jeff Ahrenholz <[email protected]>
+ */
+
+#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);

net/ipv6/Kconfig

@@ -136,6 +136,16 @@ config INET6_XFRM_MODE_TUNNEL
 
 	  If unsure, say Y.
 
+config INET6_XFRM_MODE_BEET
+	tristate "IPv6: IPsec BEET mode"
+	depends on IPV6
+	default IPV6
+	select XFRM
+	---help---
+	  Support for IPsec BEET mode.
+
+	  If unsure, say Y.
+
 config INET6_XFRM_MODE_ROUTEOPTIMIZATION
 	tristate "IPv6: MIPv6 route optimization mode (EXPERIMENTAL)"
 	depends on IPV6 && EXPERIMENTAL

net/ipv6/Makefile

@@ -26,6 +26,7 @@ obj-$(CONFIG_INET6_TUNNEL) += tunnel6.o
 obj-$(CONFIG_INET6_XFRM_MODE_TRANSPORT) += xfrm6_mode_transport.o
 obj-$(CONFIG_INET6_XFRM_MODE_TUNNEL) += xfrm6_mode_tunnel.o
 obj-$(CONFIG_INET6_XFRM_MODE_ROUTEOPTIMIZATION) += xfrm6_mode_ro.o
+obj-$(CONFIG_INET6_XFRM_MODE_BEET) += xfrm6_mode_beet.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
 
 obj-$(CONFIG_IPV6_TUNNEL) += ip6_tunnel.o

net/ipv6/ipcomp6.c

@@ -199,6 +199,7 @@ static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
 {
 	struct xfrm_state *t = NULL;
+	u8 mode = XFRM_MODE_TUNNEL;
 
 	t = xfrm_state_alloc();
 	if (!t)
@@ -212,7 +213,9 @@ static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
 	memcpy(t->id.daddr.a6, x->id.daddr.a6, sizeof(struct in6_addr));
 	memcpy(&t->sel, &x->sel, sizeof(t->sel));
 	t->props.family = AF_INET6;
-	t->props.mode = XFRM_MODE_TUNNEL;
+	if (x->props.mode == XFRM_MODE_BEET)
+		mode = x->props.mode;
+	t->props.mode = mode;
 	memcpy(t->props.saddr.a6, x->props.saddr.a6, sizeof(struct in6_addr));
 
 	if (xfrm_init_state(t))