netfilter: nf_conntrack_ipv6: improve fragmentation handling

[mirror_ubuntu-bionic-kernel.git] / net / ipv6 / netfilter / nf_conntrack_l3proto_ipv6.c

/*
 * Copyright (C)2004 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 as
 * published by the Free Software Foundation.
 *
 * Author:
 *	Yasuyuki Kozakai @USAGI <yasuyuki.kozakai@toshiba.co.jp>
 */

#include <linux/types.h>
#include <linux/ipv6.h>
#include <linux/in6.h>
#include <linux/netfilter.h>
#include <linux/module.h>
#include <linux/skbuff.h>
#include <linux/icmp.h>
#include <net/ipv6.h>
#include <net/inet_frag.h>

#include <linux/netfilter_bridge.h>
#include <linux/netfilter_ipv6.h>
#include <net/netfilter/nf_conntrack.h>
#include <net/netfilter/nf_conntrack_helper.h>
#include <net/netfilter/nf_conntrack_l4proto.h>
#include <net/netfilter/nf_conntrack_l3proto.h>
#include <net/netfilter/nf_conntrack_core.h>
#include <net/netfilter/nf_conntrack_zones.h>
#include <net/netfilter/ipv6/nf_conntrack_ipv6.h>
#include <net/netfilter/ipv6/nf_defrag_ipv6.h>
#include <net/netfilter/nf_log.h>

static bool ipv6_pkt_to_tuple(const struct sk_buff *skb, unsigned int nhoff,
			      struct nf_conntrack_tuple *tuple)
{
	const u_int32_t *ap;
	u_int32_t _addrs[8];

	ap = skb_header_pointer(skb, nhoff + offsetof(struct ipv6hdr, saddr),
				sizeof(_addrs), _addrs);
	if (ap == NULL)
		return false;

	memcpy(tuple->src.u3.ip6, ap, sizeof(tuple->src.u3.ip6));
	memcpy(tuple->dst.u3.ip6, ap + 4, sizeof(tuple->dst.u3.ip6));

	return true;
}

static bool ipv6_invert_tuple(struct nf_conntrack_tuple *tuple,
			      const struct nf_conntrack_tuple *orig)
{
	memcpy(tuple->src.u3.ip6, orig->dst.u3.ip6, sizeof(tuple->src.u3.ip6));
	memcpy(tuple->dst.u3.ip6, orig->src.u3.ip6, sizeof(tuple->dst.u3.ip6));

	return true;
}

static int ipv6_print_tuple(struct seq_file *s,
			    const struct nf_conntrack_tuple *tuple)
{
	return seq_printf(s, "src=%pI6 dst=%pI6 ",
			  tuple->src.u3.ip6, tuple->dst.u3.ip6);
}

/*
 * Based on ipv6_skip_exthdr() in net/ipv6/exthdr.c
 *
 * This function parses (probably truncated) exthdr set "hdr"
 * of length "len". "nexthdrp" initially points to some place,
 * where type of the first header can be found.
 *
 * It skips all well-known exthdrs, and returns pointer to the start
 * of unparsable area i.e. the first header with unknown type.
 * if success, *nexthdr is updated by type/protocol of this header.
 *
 * NOTES: - it may return pointer pointing beyond end of packet,
 *          if the last recognized header is truncated in the middle.
 *        - if packet is truncated, so that all parsed headers are skipped,
 *          it returns -1.
 *        - if packet is fragmented, return pointer of the fragment header.
 *        - ESP is unparsable for now and considered like
 *          normal payload protocol.
 *        - Note also special handling of AUTH header. Thanks to IPsec wizards.
 */

static int nf_ct_ipv6_skip_exthdr(const struct sk_buff *skb, int start,
				  u8 *nexthdrp, int len)
{
	u8 nexthdr = *nexthdrp;

	while (ipv6_ext_hdr(nexthdr)) {
		struct ipv6_opt_hdr hdr;
		int hdrlen;

		if (len < (int)sizeof(struct ipv6_opt_hdr))
			return -1;
		if (nexthdr == NEXTHDR_NONE)
			break;
		if (nexthdr == NEXTHDR_FRAGMENT)
			break;
		if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
			BUG();
		if (nexthdr == NEXTHDR_AUTH)
			hdrlen = (hdr.hdrlen+2)<<2;
		else
			hdrlen = ipv6_optlen(&hdr);

		nexthdr = hdr.nexthdr;
		len -= hdrlen;
		start += hdrlen;
	}

	*nexthdrp = nexthdr;
	return start;
}

static int ipv6_get_l4proto(const struct sk_buff *skb, unsigned int nhoff,
			    unsigned int *dataoff, u_int8_t *protonum)
{
	unsigned int extoff = nhoff + sizeof(struct ipv6hdr);
	unsigned char pnum;
	int protoff;

	if (skb_copy_bits(skb, nhoff + offsetof(struct ipv6hdr, nexthdr),
			  &pnum, sizeof(pnum)) != 0) {
		pr_debug("ip6_conntrack_core: can't get nexthdr\n");
		return -NF_ACCEPT;
	}
	protoff = nf_ct_ipv6_skip_exthdr(skb, extoff, &pnum, skb->len - extoff);
	/*
	 * (protoff == skb->len) mean that the packet doesn't have no data
	 * except of IPv6 & ext headers. but it's tracked anyway. - YK
	 */
	if ((protoff < 0) || (protoff > skb->len)) {
		pr_debug("ip6_conntrack_core: can't find proto in pkt\n");
		return -NF_ACCEPT;
	}

	*dataoff = protoff;
	*protonum = pnum;
	return NF_ACCEPT;
}

static unsigned int ipv6_helper(unsigned int hooknum,
				struct sk_buff *skb,
				const struct net_device *in,
				const struct net_device *out,
				int (*okfn)(struct sk_buff *))
{
	struct nf_conn *ct;
	const struct nf_conn_help *help;
	const struct nf_conntrack_helper *helper;
	enum ip_conntrack_info ctinfo;
	unsigned int ret;
	__be16 frag_off;
	int protoff;
	u8 nexthdr;

	/* This is where we call the helper: as the packet goes out. */
	ct = nf_ct_get(skb, &ctinfo);
	if (!ct || ctinfo == IP_CT_RELATED_REPLY)
		return NF_ACCEPT;

	help = nfct_help(ct);
	if (!help)
		return NF_ACCEPT;
	/* rcu_read_lock()ed by nf_hook_slow */
	helper = rcu_dereference(help->helper);
	if (!helper)
		return NF_ACCEPT;

	nexthdr = ipv6_hdr(skb)->nexthdr;
	protoff = ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &nexthdr,
				   &frag_off);
	if (protoff < 0 || (frag_off & htons(~0x7)) != 0) {
		pr_debug("proto header not found\n");
		return NF_ACCEPT;
	}

	ret = helper->help(skb, protoff, ct, ctinfo);
	if (ret != NF_ACCEPT && (ret & NF_VERDICT_MASK) != NF_QUEUE) {
		nf_log_packet(NFPROTO_IPV6, hooknum, skb, in, out, NULL,
			      "nf_ct_%s: dropping packet", helper->name);
	}
	return ret;
}

static unsigned int ipv6_confirm(unsigned int hooknum,
				 struct sk_buff *skb,
				 const struct net_device *in,
				 const struct net_device *out,
				 int (*okfn)(struct sk_buff *))
{
	/* We've seen it coming out the other side: confirm it */
	return nf_conntrack_confirm(skb);
}

static unsigned int __ipv6_conntrack_in(struct net *net,
					unsigned int hooknum,
					struct sk_buff *skb,
					const struct net_device *in,
					const struct net_device *out,
					int (*okfn)(struct sk_buff *))
{
	struct sk_buff *reasm = skb->nfct_reasm;
	const struct nf_conn_help *help;
	struct nf_conn *ct;
	enum ip_conntrack_info ctinfo;

	/* This packet is fragmented and has reassembled packet. */
	if (reasm) {
		/* Reassembled packet isn't parsed yet ? */
		if (!reasm->nfct) {
			unsigned int ret;

			ret = nf_conntrack_in(net, PF_INET6, hooknum, reasm);
			if (ret != NF_ACCEPT)
				return ret;
		}

		/* Conntrack helpers need the entire reassembled packet in the
		 * POST_ROUTING hook.
		 */
		ct = nf_ct_get(reasm, &ctinfo);
		if (ct != NULL && !nf_ct_is_untracked(ct)) {
			help = nfct_help(ct);
			if (help && help->helper) {
				nf_conntrack_get_reasm(skb);
				NF_HOOK_THRESH(NFPROTO_IPV6, hooknum, reasm,
					       (struct net_device *)in,
					       (struct net_device *)out,
					       okfn, NF_IP6_PRI_CONNTRACK + 1);
				return NF_DROP_ERR(-ECANCELED);
			}
		}

		nf_conntrack_get(reasm->nfct);
		skb->nfct = reasm->nfct;
		skb->nfctinfo = reasm->nfctinfo;
		return NF_ACCEPT;
	}

	return nf_conntrack_in(net, PF_INET6, hooknum, skb);
}

static unsigned int ipv6_conntrack_in(unsigned int hooknum,
				      struct sk_buff *skb,
				      const struct net_device *in,
				      const struct net_device *out,
				      int (*okfn)(struct sk_buff *))
{
	return __ipv6_conntrack_in(dev_net(in), hooknum, skb, in, out, okfn);
}

static unsigned int ipv6_conntrack_local(unsigned int hooknum,
					 struct sk_buff *skb,
					 const struct net_device *in,
					 const struct net_device *out,
					 int (*okfn)(struct sk_buff *))
{
	/* root is playing with raw sockets. */
	if (skb->len < sizeof(struct ipv6hdr)) {
		net_notice_ratelimited("ipv6_conntrack_local: packet too short\n");
		return NF_ACCEPT;
	}
	return __ipv6_conntrack_in(dev_net(out), hooknum, skb, in, out, okfn);
}

static struct nf_hook_ops ipv6_conntrack_ops[] __read_mostly = {
	{
		.hook		= ipv6_conntrack_in,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_PRE_ROUTING,
		.priority	= NF_IP6_PRI_CONNTRACK,
	},
	{
		.hook		= ipv6_conntrack_local,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_LOCAL_OUT,
		.priority	= NF_IP6_PRI_CONNTRACK,
	},
	{
		.hook		= ipv6_helper,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_POST_ROUTING,
		.priority	= NF_IP6_PRI_CONNTRACK_HELPER,
	},
	{
		.hook		= ipv6_confirm,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_POST_ROUTING,
		.priority	= NF_IP6_PRI_LAST,
	},
	{
		.hook		= ipv6_helper,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_LOCAL_IN,
		.priority	= NF_IP6_PRI_CONNTRACK_HELPER,
	},
	{
		.hook		= ipv6_confirm,
		.owner		= THIS_MODULE,
		.pf		= NFPROTO_IPV6,
		.hooknum	= NF_INET_LOCAL_IN,
		.priority	= NF_IP6_PRI_LAST-1,
	},
};

#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)

#include <linux/netfilter/nfnetlink.h>
#include <linux/netfilter/nfnetlink_conntrack.h>

static int ipv6_tuple_to_nlattr(struct sk_buff *skb,
				const struct nf_conntrack_tuple *tuple)
{
	if (nla_put(skb, CTA_IP_V6_SRC, sizeof(u_int32_t) * 4,
		    &tuple->src.u3.ip6) ||
	    nla_put(skb, CTA_IP_V6_DST, sizeof(u_int32_t) * 4,
		    &tuple->dst.u3.ip6))
		goto nla_put_failure;
	return 0;

nla_put_failure:
	return -1;
}

static const struct nla_policy ipv6_nla_policy[CTA_IP_MAX+1] = {
	[CTA_IP_V6_SRC]	= { .len = sizeof(u_int32_t)*4 },
	[CTA_IP_V6_DST]	= { .len = sizeof(u_int32_t)*4 },
};

static int ipv6_nlattr_to_tuple(struct nlattr *tb[],
				struct nf_conntrack_tuple *t)
{
	if (!tb[CTA_IP_V6_SRC] || !tb[CTA_IP_V6_DST])
		return -EINVAL;

	memcpy(&t->src.u3.ip6, nla_data(tb[CTA_IP_V6_SRC]),
	       sizeof(u_int32_t) * 4);
	memcpy(&t->dst.u3.ip6, nla_data(tb[CTA_IP_V6_DST]),
	       sizeof(u_int32_t) * 4);

	return 0;
}

static int ipv6_nlattr_tuple_size(void)
{
	return nla_policy_len(ipv6_nla_policy, CTA_IP_MAX + 1);
}
#endif

struct nf_conntrack_l3proto nf_conntrack_l3proto_ipv6 __read_mostly = {
	.l3proto		= PF_INET6,
	.name			= "ipv6",
	.pkt_to_tuple		= ipv6_pkt_to_tuple,
	.invert_tuple		= ipv6_invert_tuple,
	.print_tuple		= ipv6_print_tuple,
	.get_l4proto		= ipv6_get_l4proto,
#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
	.tuple_to_nlattr	= ipv6_tuple_to_nlattr,
	.nlattr_tuple_size	= ipv6_nlattr_tuple_size,
	.nlattr_to_tuple	= ipv6_nlattr_to_tuple,
	.nla_policy		= ipv6_nla_policy,
#endif
	.me			= THIS_MODULE,
};

MODULE_ALIAS("nf_conntrack-" __stringify(AF_INET6));
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Yasuyuki KOZAKAI @USAGI <yasuyuki.kozakai@toshiba.co.jp>");

static int ipv6_net_init(struct net *net)
{
	int ret = 0;

	ret = nf_conntrack_l4proto_register(net,
					    &nf_conntrack_l4proto_tcp6);
	if (ret < 0) {
		printk(KERN_ERR "nf_conntrack_l4proto_tcp6: protocol register failed\n");
		goto out;
	}
	ret = nf_conntrack_l4proto_register(net,
					    &nf_conntrack_l4proto_udp6);
	if (ret < 0) {
		printk(KERN_ERR "nf_conntrack_l4proto_udp6: protocol register failed\n");
		goto cleanup_tcp6;
	}
	ret = nf_conntrack_l4proto_register(net,
					    &nf_conntrack_l4proto_icmpv6);
	if (ret < 0) {
		printk(KERN_ERR "nf_conntrack_l4proto_icmp6: protocol register failed\n");
		goto cleanup_udp6;
	}
	ret = nf_conntrack_l3proto_register(net,
					    &nf_conntrack_l3proto_ipv6);
	if (ret < 0) {
		printk(KERN_ERR "nf_conntrack_l3proto_ipv6: protocol register failed\n");
		goto cleanup_icmpv6;
	}
	return 0;
 cleanup_icmpv6:
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_icmpv6);
 cleanup_udp6:
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_udp6);
 cleanup_tcp6:
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_tcp6);
 out:
	return ret;
}

static void ipv6_net_exit(struct net *net)
{
	nf_conntrack_l3proto_unregister(net,
					&nf_conntrack_l3proto_ipv6);
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_icmpv6);
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_udp6);
	nf_conntrack_l4proto_unregister(net,
					&nf_conntrack_l4proto_tcp6);
}

static struct pernet_operations ipv6_net_ops = {
	.init = ipv6_net_init,
	.exit = ipv6_net_exit,
};

static int __init nf_conntrack_l3proto_ipv6_init(void)
{
	int ret = 0;

	need_conntrack();
	nf_defrag_ipv6_enable();

	ret = register_pernet_subsys(&ipv6_net_ops);
	if (ret < 0)
		goto cleanup_pernet;
	ret = nf_register_hooks(ipv6_conntrack_ops,
				ARRAY_SIZE(ipv6_conntrack_ops));
	if (ret < 0) {
		pr_err("nf_conntrack_ipv6: can't register pre-routing defrag "
		       "hook.\n");
		goto cleanup_ipv6;
	}
	return ret;

 cleanup_ipv6:
	unregister_pernet_subsys(&ipv6_net_ops);
 cleanup_pernet:
	return ret;
}

static void __exit nf_conntrack_l3proto_ipv6_fini(void)
{
	synchronize_net();
	nf_unregister_hooks(ipv6_conntrack_ops, ARRAY_SIZE(ipv6_conntrack_ops));
	unregister_pernet_subsys(&ipv6_net_ops);
}

module_init(nf_conntrack_l3proto_ipv6_init);
module_exit(nf_conntrack_l3proto_ipv6_fini);