[IPSEC]: Add initial IPCOMP support.

net/ipv4/Kconfig

@@ -362,5 +362,13 @@ config INET_ESP
 
 	  If unsure, say Y.
 
+config INET_IPCOMP
+	tristate "IP: IPComp transformation"
+	---help---
+	  Support for IP Paylod Compression (RFC3173), typically needed
+	  for IPsec.
+	  
+	  If unsure, say Y.
+
 source "net/ipv4/netfilter/Kconfig"
 

net/ipv4/Makefile

@@ -18,6 +18,7 @@ obj-$(CONFIG_NET_IPGRE) += ip_gre.o
 obj-$(CONFIG_SYN_COOKIES) += syncookies.o
 obj-$(CONFIG_INET_AH) += ah.o
 obj-$(CONFIG_INET_ESP) += esp.o
+obj-$(CONFIG_INET_IPCOMP) += ipcomp.o
 obj-$(CONFIG_IP_PNP) += ipconfig.o
 obj-$(CONFIG_NETFILTER)	+= netfilter/
 

net/ipv4/ipcomp.c

+/*
+ * IP Payload Compression Protocol (IPComp) - RFC3713.
+ *
+ * Copyright (c) 2003 James Morris <jmorris@intercode.com.au>
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option) 
+ * any later version.
+ *
+ * Todo:
+ *   - Tunable compression parameters.
+ *   - Compression stats.
+ *   - Adaptive compression.
+ */
+#include <linux/config.h>
+#include <linux/module.h>
+#include <asm/scatterlist.h>
+#include <linux/crypto.h>
+#include <linux/pfkeyv2.h>
+#include <net/ip.h>
+#include <net/xfrm.h>
+#include <net/icmp.h>
+#include <net/esp.h>
+
+#define IPCOMP_SCRATCH_SIZE	65400
+
+struct ipcomp_hdr {
+	u8 nexthdr;
+	u8 flags;
+	u16 cpi;
+};
+
+struct ipcomp_data {
+	u16 threshold;
+	u8 *scratch;
+	struct crypto_tfm *tfm;
+};
+
+static int ipcomp_decompress(struct xfrm_state *x, struct sk_buff *skb)
+{
+	int err, plen, dlen;
+	struct iphdr *iph;
+	struct ipcomp_data *ipcd = x->data;
+	u8 *start, *scratch = ipcd->scratch;
+	
+	plen = skb->len;
+	dlen = IPCOMP_SCRATCH_SIZE;
+	start = skb->data;
+
+	err = crypto_comp_decompress(ipcd->tfm, start, plen, scratch, &dlen);
+	if (err)
+		goto out;
+
+	if (dlen < (plen + sizeof(struct ipcomp_hdr))) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = pskb_expand_head(skb, 0, dlen - plen, GFP_ATOMIC);
+	if (err)
+		goto out;
+		
+	skb_put(skb, dlen - plen);
+	memcpy(skb->data, scratch, dlen);
+	iph = skb->nh.iph;
+	iph->tot_len = htons(dlen + iph->ihl * 4);
+out:	
+	return err;
+}
+
+static int ipcomp_input(struct xfrm_state *x,
+                        struct xfrm_decap_state *decap, struct sk_buff *skb)
+{
+	u8 nexthdr;
+	int err = 0;
+	struct iphdr *iph;
+	union {
+		struct iphdr	iph;
+		char 		buf[60];
+	} tmp_iph;
+
+
+	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
+	    skb_linearize(skb, GFP_ATOMIC) != 0) {
+	    	err = -ENOMEM;
+	    	goto out;
+	}
+
+	skb->ip_summed = CHECKSUM_NONE;
+
+	/* Remove ipcomp header and decompress original payload */	
+	iph = skb->nh.iph;
+	memcpy(&tmp_iph, iph, iph->ihl * 4);
+	nexthdr = *(u8 *)skb->data;
+	skb_pull(skb, sizeof(struct ipcomp_hdr));
+	memcpy(skb->nh.raw, &tmp_iph, tmp_iph.iph.ihl * 4);
+	iph->tot_len = htons(ntohs(iph->tot_len) - sizeof(struct ipcomp_hdr));
+	iph->protocol = nexthdr;
+	skb->h.raw = skb->data;
+	err = ipcomp_decompress(x, skb);
+
+out:	
+	return err;
+}
+
+static int ipcomp_compress(struct xfrm_state *x, struct sk_buff *skb)
+{
+	int err, plen, dlen, ihlen;
+	struct iphdr *iph = skb->nh.iph;
+	struct ipcomp_data *ipcd = x->data;
+	u8 *start, *scratch = ipcd->scratch;
+	
+	ihlen = iph->ihl * 4;
+	plen = skb->len - ihlen;
+	dlen = IPCOMP_SCRATCH_SIZE;
+	start = skb->data + ihlen;
+
+	err = crypto_comp_compress(ipcd->tfm, start, plen, scratch, &dlen);
+	if (err)
+		goto out;
+
+	if ((dlen + sizeof(struct ipcomp_hdr)) >= plen) {
+		err = -EMSGSIZE;
+		goto out;
+	}
+	
+	memcpy(start, scratch, dlen);
+	pskb_trim(skb, ihlen + dlen);
+	
+out:	
+	return err;
+}
+
+static void ipcomp_tunnel_encap(struct xfrm_state *x,
+                                struct sk_buff *skb, int compress)
+{
+	struct dst_entry *dst = skb->dst;
+	struct iphdr *iph, *top_iph;
+
+	iph = skb->nh.iph;
+	top_iph = (struct iphdr *)skb_push(skb, sizeof(struct iphdr));
+	top_iph->ihl = 5;
+	top_iph->version = 4;
+	top_iph->tos = iph->tos;
+	top_iph->tot_len = htons(skb->len);
+	if (!(iph->frag_off&htons(IP_DF)))
+		__ip_select_ident(top_iph, dst, 0);
+	top_iph->ttl = iph->ttl;
+	top_iph->protocol = compress ? IPPROTO_COMP : IPPROTO_IPIP;
+	top_iph->check = 0;
+	top_iph->saddr = x->props.saddr.a4;
+	top_iph->daddr = x->id.daddr.a4;
+	top_iph->frag_off = iph->frag_off&~htons(IP_MF|IP_OFFSET);
+	memset(&(IPCB(skb)->opt), 0, sizeof(struct ip_options));
+	skb->nh.raw = skb->data;
+}
+
+static int ipcomp_output(struct sk_buff *skb)
+{
+	int err;
+	struct dst_entry *dst = skb->dst;
+	struct xfrm_state *x = dst->xfrm;
+	struct iphdr *iph, *top_iph;
+	struct ipcomp_hdr *ipch;
+	struct ipcomp_data *ipcd = x->data;
+	union {
+		struct iphdr	iph;
+		char 		buf[60];
+	} tmp_iph;
+
+	if (skb->ip_summed == CHECKSUM_HW && skb_checksum_help(skb) == NULL) {
+		err = -EINVAL;
+		goto error_nolock;
+	}
+
+	spin_lock_bh(&x->lock);
+	
+	if ((err = xfrm_state_check_expire(x)) != 0)
+		goto error;
+	if ((err = xfrm_state_check_space(x, skb)) != 0)
+		goto error;
+
+	/* Don't bother compressing */
+	if (skb->len < ipcd->threshold) {
+		if (x->props.mode) {
+			ipcomp_tunnel_encap(x, skb, 0);
+			iph = skb->nh.iph;
+			ip_send_check(iph);
+		}
+		goto out_ok;
+	}
+
+	if (x->props.mode) 
+		ipcomp_tunnel_encap(x, skb, 1);
+
+	if ((skb_is_nonlinear(skb) || skb_cloned(skb)) &&
+	    skb_linearize(skb, GFP_ATOMIC) != 0) {
+	    	err = -ENOMEM;
+	    	goto error;
+	}
+	
+	err = ipcomp_compress(x, skb);
+	if (err) {
+		if (err == -EMSGSIZE)
+			goto out_ok;
+		goto error;
+	}
+
+	/* Install ipcomp header, convert into ipcomp datagram. */
+	iph = skb->nh.iph;
+	memcpy(&tmp_iph, iph, iph->ihl * 4);
+	top_iph = (struct iphdr *)skb_push(skb, sizeof(struct ipcomp_hdr));
+	memcpy(top_iph, &tmp_iph, iph->ihl * 4);
+	iph = top_iph;
+	iph->tot_len = htons(skb->len);
+	iph->protocol = IPPROTO_COMP;
+	iph->check = 0;
+	ipch = (struct ipcomp_hdr *)((char *)iph + iph->ihl * 4);
+	ipch->nexthdr = x->props.mode ? IPPROTO_IPIP : tmp_iph.iph.protocol;
+	ipch->flags = 0;
+	ipch->cpi = htons((u16 )ntohl(x->id.spi));
+	ip_send_check(iph);
+	skb->nh.raw = skb->data;
+
+out_ok:
+	x->curlft.bytes += skb->len;
+	x->curlft.packets++;
+	spin_unlock_bh(&x->lock);
+	
+	if ((skb->dst = dst_pop(dst)) == NULL) {
+		err = -EHOSTUNREACH;
+		goto error_nolock;
+	}
+	err = NET_XMIT_BYPASS;
+
+out_exit:
+	return err;
+error:
+	spin_unlock_bh(&x->lock);
+error_nolock:
+	kfree_skb(skb);
+	goto out_exit;
+}
+
+static void ipcomp4_err(struct sk_buff *skb, u32 info)
+{
+	u32 spi;
+	struct iphdr *iph = (struct iphdr *)skb->data;
+	struct ipcomp_hdr *ipch = (struct ipcomp_hdr *)(skb->data+(iph->ihl<<2));
+	struct xfrm_state *x;
+
+	if (skb->h.icmph->type != ICMP_DEST_UNREACH ||
+	    skb->h.icmph->code != ICMP_FRAG_NEEDED)
+		return;
+
+	spi = ntohl(ntohs(ipch->cpi));
+	x = xfrm_state_lookup((xfrm_address_t *)&iph->daddr,
+	                      spi, IPPROTO_COMP, AF_INET);
+	if (!x)
+		return;
+	printk(KERN_DEBUG "pmtu discvovery on SA IPCOMP/%08x/%u.%u.%u.%u\n",
+	       spi, NIPQUAD(iph->daddr));
+	xfrm_state_put(x);
+}
+
+static void ipcomp_free_data(struct ipcomp_data *ipcd)
+{
+	if (ipcd->tfm)
+		crypto_free_tfm(ipcd->tfm);
+	if (ipcd->scratch)
+		kfree(ipcd->scratch);	
+}
+
+static void ipcomp_destroy(struct xfrm_state *x)
+{
+	struct ipcomp_data *ipcd = x->data;
+	ipcomp_free_data(ipcd);
+	kfree(ipcd);
+}
+
+static int ipcomp_init_state(struct xfrm_state *x, void *args)
+{
+	int err = -ENOMEM;
+	struct ipcomp_data *ipcd;
+	struct xfrm_algo_desc *calg_desc;
+
+	ipcd = kmalloc(sizeof(*ipcd), GFP_KERNEL);
+	if (!ipcd)
+		goto error;
+
+	memset(ipcd, 0, sizeof(*ipcd));
+	x->props.header_len = sizeof(struct ipcomp_hdr);
+	if (x->props.mode)
+		x->props.header_len += sizeof(struct iphdr);
+	x->data = ipcd;
+
+	ipcd->scratch = kmalloc(IPCOMP_SCRATCH_SIZE, GFP_KERNEL);
+	if (!ipcd->scratch)
+		goto error;
+	
+	ipcd->tfm = crypto_alloc_tfm(x->calg->alg_name, 0);
+	if (!ipcd->tfm)
+		goto error;
+
+	calg_desc = xfrm_calg_get_byname(x->calg->alg_name);
+	BUG_ON(!calg_desc);
+	ipcd->threshold = calg_desc->uinfo.comp.threshold;
+	err = 0;
+out:
+	return err;
+
+error:
+	if (ipcd) {
+		ipcomp_free_data(ipcd);
+		kfree(ipcd);
+	}
+	goto out;
+}
+
+static struct xfrm_type ipcomp_type =
+{
+	.description	= "IPCOMP4",
+	.proto	     	= IPPROTO_COMP,
+	.init_state	= ipcomp_init_state,
+	.destructor	= ipcomp_destroy,
+	.input		= ipcomp_input,
+	.output		= ipcomp_output
+};
+
+static struct inet_protocol ipcomp4_protocol = {
+	.handler	=	xfrm4_rcv,
+	.err_handler	=	ipcomp4_err,
+	.no_policy	=	1,
+};
+
+static int __init ipcomp4_init(void)
+{
+	SET_MODULE_OWNER(&ipcomp_type);
+	if (xfrm_register_type(&ipcomp_type, AF_INET) < 0) {
+		printk(KERN_INFO "ipcomp init: can't add xfrm type\n");
+		return -EAGAIN;
+	}
+	if (inet_add_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0) {
+		printk(KERN_INFO "ipcomp init: can't add protocol\n");
+		xfrm_unregister_type(&ipcomp_type, AF_INET);
+		return -EAGAIN;
+	}
+	return 0;
+}
+
+static void __exit ipcomp4_fini(void)
+{
+	if (inet_del_protocol(&ipcomp4_protocol, IPPROTO_COMP) < 0)
+		printk(KERN_INFO "ip ipcomp close: can't remove protocol\n");
+	if (xfrm_unregister_type(&ipcomp_type, AF_INET) < 0)
+		printk(KERN_INFO "ip ipcomp close: can't remove xfrm type\n");
+}
+
+module_init(ipcomp4_init);
+module_exit(ipcomp4_fini);
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) - RFC3713");
+MODULE_AUTHOR("James Morris <jmorris@intercode.com.au>");
+

net/ipv4/xfrm4_policy.c

@@ -201,6 +201,13 @@ _decode_session4(struct sk_buff *skb, struct flowi *fl)
 			}
 			break;
 
+		case IPPROTO_COMP:
+			if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
+				u16 *ipcomp_hdr = (u16 *)xprth;
+
+				fl->uli_u.spi = ntohl(ntohs(ipcomp_hdr[1]));
+			}
+			break;
 		default:
 			fl->uli_u.spi = 0;
 			break;

net/ipv6/xfrm6_policy.c

@@ -203,6 +203,7 @@ _decode_session6(struct sk_buff *skb, struct flowi *fl)
 		/* XXX Why are there these headers? */
 		case IPPROTO_AH:
 		case IPPROTO_ESP:
+		case IPPROTO_COMP:
 		default:
 			fl->uli_u.spi = 0;
 			return;