/net/ipv4/netfilter/nf_conntrack_proto_icmp.c

  1/* (C) 1999-2001 Paul `Rusty' Russell
  2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
  3 *
  4 * This program is free software; you can redistribute it and/or modify
  5 * it under the terms of the GNU General Public License version 2 as
  6 * published by the Free Software Foundation.
  7 */
  8
  9#include <linux/types.h>
 10#include <linux/timer.h>
 11#include <linux/netfilter.h>
 12#include <linux/in.h>
 13#include <linux/icmp.h>
 14#include <linux/seq_file.h>
 15#include <net/ip.h>
 16#include <net/checksum.h>
 17#include <linux/netfilter_ipv4.h>
 18#include <net/netfilter/nf_conntrack_tuple.h>
 19#include <net/netfilter/nf_conntrack_l4proto.h>
 20#include <net/netfilter/nf_conntrack_core.h>
 21#include <net/netfilter/nf_conntrack_zones.h>
 22#include <net/netfilter/nf_log.h>
 23
 24static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
 25
 26static bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 27			      struct nf_conntrack_tuple *tuple)
 28{
 29	const struct icmphdr *hp;
 30	struct icmphdr _hdr;
 31
 32	hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
 33	if (hp == NULL)
 34		return false;
 35
 36	tuple->dst.u.icmp.type = hp->type;
 37	tuple->src.u.icmp.id = hp->un.echo.id;
 38	tuple->dst.u.icmp.code = hp->code;
 39
 40	return true;
 41}
 42
 43/* Add 1; spaces filled with 0. */
 44static const u_int8_t invmap[] = {
 45	[ICMP_ECHO] = ICMP_ECHOREPLY + 1,
 46	[ICMP_ECHOREPLY] = ICMP_ECHO + 1,
 47	[ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
 48	[ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
 49	[ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
 50	[ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
 51	[ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
 52	[ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
 53};
 54
 55static bool icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
 56			      const struct nf_conntrack_tuple *orig)
 57{
 58	if (orig->dst.u.icmp.type >= sizeof(invmap) ||
 59	    !invmap[orig->dst.u.icmp.type])
 60		return false;
 61
 62	tuple->src.u.icmp.id = orig->src.u.icmp.id;
 63	tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
 64	tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
 65	return true;
 66}
 67
 68/* Print out the per-protocol part of the tuple. */
 69static int icmp_print_tuple(struct seq_file *s,
 70			    const struct nf_conntrack_tuple *tuple)
 71{
 72	return seq_printf(s, "type=%u code=%u id=%u ",
 73			  tuple->dst.u.icmp.type,
 74			  tuple->dst.u.icmp.code,
 75			  ntohs(tuple->src.u.icmp.id));
 76}
 77
 78/* Returns verdict for packet, or -1 for invalid. */
 79static int icmp_packet(struct nf_conn *ct,
 80		       const struct sk_buff *skb,
 81		       unsigned int dataoff,
 82		       enum ip_conntrack_info ctinfo,
 83		       u_int8_t pf,
 84		       unsigned int hooknum)
 85{
 86	/* Do not immediately delete the connection after the first
 87	   successful reply to avoid excessive conntrackd traffic
 88	   and also to handle correctly ICMP echo reply duplicates. */
 89	nf_ct_refresh_acct(ct, ctinfo, skb, nf_ct_icmp_timeout);
 90
 91	return NF_ACCEPT;
 92}
 93
 94/* Called when a new connection for this protocol found. */
 95static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
 96		     unsigned int dataoff)
 97{
 98	static const u_int8_t valid_new[] = {
 99		[ICMP_ECHO] = 1,
100		[ICMP_TIMESTAMP] = 1,
101		[ICMP_INFO_REQUEST] = 1,
102		[ICMP_ADDRESS] = 1
103	};
104
105	if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
106	    !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
107		/* Can't create a new ICMP `conn' with this. */
108		pr_debug("icmp: can't create new conn with type %u\n",
109			 ct->tuplehash[0].tuple.dst.u.icmp.type);
110		nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
111		return false;
112	}
113	return true;
114}
115
116/* Returns conntrack if it dealt with ICMP, and filled in skb fields */
117static int
118icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
119		 enum ip_conntrack_info *ctinfo,
120		 unsigned int hooknum)
121{
122	struct nf_conntrack_tuple innertuple, origtuple;
123	const struct nf_conntrack_l4proto *innerproto;
124	const struct nf_conntrack_tuple_hash *h;
125	u16 zone = tmpl ? nf_ct_zone(tmpl) : NF_CT_DEFAULT_ZONE;
126
127	NF_CT_ASSERT(skb->nfct == NULL);
128
129	/* Are they talking about one of our connections? */
130	if (!nf_ct_get_tuplepr(skb,
131			       skb_network_offset(skb) + ip_hdrlen(skb)
132						       + sizeof(struct icmphdr),
133			       PF_INET, &origtuple)) {
134		pr_debug("icmp_error_message: failed to get tuple\n");
135		return -NF_ACCEPT;
136	}
137
138	/* rcu_read_lock()ed by nf_hook_slow */
139	innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
140
141	/* Ordinarily, we'd expect the inverted tupleproto, but it's
142	   been preserved inside the ICMP. */
143	if (!nf_ct_invert_tuple(&innertuple, &origtuple,
144				&nf_conntrack_l3proto_ipv4, innerproto)) {
145		pr_debug("icmp_error_message: no match\n");
146		return -NF_ACCEPT;
147	}
148
149	*ctinfo = IP_CT_RELATED;
150
151	h = nf_conntrack_find_get(net, zone, &innertuple);
152	if (!h) {
153		pr_debug("icmp_error_message: no match\n");
154		return -NF_ACCEPT;
155	}
156
157	if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
158		*ctinfo += IP_CT_IS_REPLY;
159
160	/* Update skb to refer to this connection */
161	skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
162	skb->nfctinfo = *ctinfo;
163	return -NF_ACCEPT;
164}
165
166/* Small and modified version of icmp_rcv */
167static int
168icmp_error(struct net *net, struct nf_conn *tmpl,
169	   struct sk_buff *skb, unsigned int dataoff,
170	   enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
171{
172	const struct icmphdr *icmph;
173	struct icmphdr _ih;
174
175	/* Not enough header? */
176	icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
177	if (icmph == NULL) {
178		if (LOG_INVALID(net, IPPROTO_ICMP))
179			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
180				      "nf_ct_icmp: short packet ");
181		return -NF_ACCEPT;
182	}
183
184	/* See ip_conntrack_proto_tcp.c */
185	if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
186	    nf_ip_checksum(skb, hooknum, dataoff, 0)) {
187		if (LOG_INVALID(net, IPPROTO_ICMP))
188			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
189				      "nf_ct_icmp: bad HW ICMP checksum ");
190		return -NF_ACCEPT;
191	}
192
193	/*
194	 *	18 is the highest 'known' ICMP type. Anything else is a mystery
195	 *
196	 *	RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
197	 *		  discarded.
198	 */
199	if (icmph->type > NR_ICMP_TYPES) {
200		if (LOG_INVALID(net, IPPROTO_ICMP))
201			nf_log_packet(PF_INET, 0, skb, NULL, NULL, NULL,
202				      "nf_ct_icmp: invalid ICMP type ");
203		return -NF_ACCEPT;
204	}
205
206	/* Need to track icmp error message? */
207	if (icmph->type != ICMP_DEST_UNREACH &&
208	    icmph->type != ICMP_SOURCE_QUENCH &&
209	    icmph->type != ICMP_TIME_EXCEEDED &&
210	    icmph->type != ICMP_PARAMETERPROB &&
211	    icmph->type != ICMP_REDIRECT)
212		return NF_ACCEPT;
213
214	return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
215}
216
217#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
218
219#include <linux/netfilter/nfnetlink.h>
220#include <linux/netfilter/nfnetlink_conntrack.h>
221
222static int icmp_tuple_to_nlattr(struct sk_buff *skb,
223				const struct nf_conntrack_tuple *t)
224{
225	NLA_PUT_BE16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id);
226	NLA_PUT_U8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type);
227	NLA_PUT_U8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code);
228
229	return 0;
230
231nla_put_failure:
232	return -1;
233}
234
235static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
236	[CTA_PROTO_ICMP_TYPE]	= { .type = NLA_U8 },
237	[CTA_PROTO_ICMP_CODE]	= { .type = NLA_U8 },
238	[CTA_PROTO_ICMP_ID]	= { .type = NLA_U16 },
239};
240
241static int icmp_nlattr_to_tuple(struct nlattr *tb[],
242				struct nf_conntrack_tuple *tuple)
243{
244	if (!tb[CTA_PROTO_ICMP_TYPE] ||
245	    !tb[CTA_PROTO_ICMP_CODE] ||
246	    !tb[CTA_PROTO_ICMP_ID])
247		return -EINVAL;
248
249	tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
250	tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
251	tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
252
253	if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
254	    !invmap[tuple->dst.u.icmp.type])
255		return -EINVAL;
256
257	return 0;
258}
259
260static int icmp_nlattr_tuple_size(void)
261{
262	return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
263}
264#endif
265
266#ifdef CONFIG_SYSCTL
267static struct ctl_table_header *icmp_sysctl_header;
268static struct ctl_table icmp_sysctl_table[] = {
269	{
270		.procname	= "nf_conntrack_icmp_timeout",
271		.data		= &nf_ct_icmp_timeout,
272		.maxlen		= sizeof(unsigned int),
273		.mode		= 0644,
274		.proc_handler	= proc_dointvec_jiffies,
275	},
276	{ }
277};
278#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
279static struct ctl_table icmp_compat_sysctl_table[] = {
280	{
281		.procname	= "ip_conntrack_icmp_timeout",
282		.data		= &nf_ct_icmp_timeout,
283		.maxlen		= sizeof(unsigned int),
284		.mode		= 0644,
285		.proc_handler	= proc_dointvec_jiffies,
286	},
287	{ }
288};
289#endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
290#endif /* CONFIG_SYSCTL */
291
292struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
293{
294	.l3proto		= PF_INET,
295	.l4proto		= IPPROTO_ICMP,
296	.name			= "icmp",
297	.pkt_to_tuple		= icmp_pkt_to_tuple,
298	.invert_tuple		= icmp_invert_tuple,
299	.print_tuple		= icmp_print_tuple,
300	.packet			= icmp_packet,
301	.new			= icmp_new,
302	.error			= icmp_error,
303	.destroy		= NULL,
304	.me			= NULL,
305#if defined(CONFIG_NF_CT_NETLINK) || defined(CONFIG_NF_CT_NETLINK_MODULE)
306	.tuple_to_nlattr	= icmp_tuple_to_nlattr,
307	.nlattr_tuple_size	= icmp_nlattr_tuple_size,
308	.nlattr_to_tuple	= icmp_nlattr_to_tuple,
309	.nla_policy		= icmp_nla_policy,
310#endif
311#ifdef CONFIG_SYSCTL
312	.ctl_table_header	= &icmp_sysctl_header,
313	.ctl_table		= icmp_sysctl_table,
314#ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
315	.ctl_compat_table	= icmp_compat_sysctl_table,
316#endif
317#endif
318};