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Linux/net/ipv4/netfilter/nf_conntrack_proto_icmp.c

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  1 /* (C) 1999-2001 Paul `Rusty' Russell
  2  * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
  3  * (C) 2006-2010 Patrick McHardy <kaber@trash.net>
  4  *
  5  * This program is free software; you can redistribute it and/or modify
  6  * it under the terms of the GNU General Public License version 2 as
  7  * published by the Free Software Foundation.
  8  */
  9 
 10 #include <linux/types.h>
 11 #include <linux/timer.h>
 12 #include <linux/netfilter.h>
 13 #include <linux/in.h>
 14 #include <linux/icmp.h>
 15 #include <linux/seq_file.h>
 16 #include <net/ip.h>
 17 #include <net/checksum.h>
 18 #include <linux/netfilter_ipv4.h>
 19 #include <net/netfilter/nf_conntrack_tuple.h>
 20 #include <net/netfilter/nf_conntrack_l4proto.h>
 21 #include <net/netfilter/nf_conntrack_core.h>
 22 #include <net/netfilter/nf_conntrack_zones.h>
 23 #include <net/netfilter/nf_log.h>
 24 
 25 static unsigned int nf_ct_icmp_timeout __read_mostly = 30*HZ;
 26 
 27 static inline struct nf_icmp_net *icmp_pernet(struct net *net)
 28 {
 29         return &net->ct.nf_ct_proto.icmp;
 30 }
 31 
 32 static bool icmp_pkt_to_tuple(const struct sk_buff *skb, unsigned int dataoff,
 33                               struct net *net, struct nf_conntrack_tuple *tuple)
 34 {
 35         const struct icmphdr *hp;
 36         struct icmphdr _hdr;
 37 
 38         hp = skb_header_pointer(skb, dataoff, sizeof(_hdr), &_hdr);
 39         if (hp == NULL)
 40                 return false;
 41 
 42         tuple->dst.u.icmp.type = hp->type;
 43         tuple->src.u.icmp.id = hp->un.echo.id;
 44         tuple->dst.u.icmp.code = hp->code;
 45 
 46         return true;
 47 }
 48 
 49 /* Add 1; spaces filled with 0. */
 50 static const u_int8_t invmap[] = {
 51         [ICMP_ECHO] = ICMP_ECHOREPLY + 1,
 52         [ICMP_ECHOREPLY] = ICMP_ECHO + 1,
 53         [ICMP_TIMESTAMP] = ICMP_TIMESTAMPREPLY + 1,
 54         [ICMP_TIMESTAMPREPLY] = ICMP_TIMESTAMP + 1,
 55         [ICMP_INFO_REQUEST] = ICMP_INFO_REPLY + 1,
 56         [ICMP_INFO_REPLY] = ICMP_INFO_REQUEST + 1,
 57         [ICMP_ADDRESS] = ICMP_ADDRESSREPLY + 1,
 58         [ICMP_ADDRESSREPLY] = ICMP_ADDRESS + 1
 59 };
 60 
 61 static bool icmp_invert_tuple(struct nf_conntrack_tuple *tuple,
 62                               const struct nf_conntrack_tuple *orig)
 63 {
 64         if (orig->dst.u.icmp.type >= sizeof(invmap) ||
 65             !invmap[orig->dst.u.icmp.type])
 66                 return false;
 67 
 68         tuple->src.u.icmp.id = orig->src.u.icmp.id;
 69         tuple->dst.u.icmp.type = invmap[orig->dst.u.icmp.type] - 1;
 70         tuple->dst.u.icmp.code = orig->dst.u.icmp.code;
 71         return true;
 72 }
 73 
 74 /* Print out the per-protocol part of the tuple. */
 75 static void icmp_print_tuple(struct seq_file *s,
 76                             const struct nf_conntrack_tuple *tuple)
 77 {
 78         seq_printf(s, "type=%u code=%u id=%u ",
 79                    tuple->dst.u.icmp.type,
 80                    tuple->dst.u.icmp.code,
 81                    ntohs(tuple->src.u.icmp.id));
 82 }
 83 
 84 static unsigned int *icmp_get_timeouts(struct net *net)
 85 {
 86         return &icmp_pernet(net)->timeout;
 87 }
 88 
 89 /* Returns verdict for packet, or -1 for invalid. */
 90 static int icmp_packet(struct nf_conn *ct,
 91                        const struct sk_buff *skb,
 92                        unsigned int dataoff,
 93                        enum ip_conntrack_info ctinfo,
 94                        u_int8_t pf,
 95                        unsigned int hooknum,
 96                        unsigned int *timeout)
 97 {
 98         /* Do not immediately delete the connection after the first
 99            successful reply to avoid excessive conntrackd traffic
100            and also to handle correctly ICMP echo reply duplicates. */
101         nf_ct_refresh_acct(ct, ctinfo, skb, *timeout);
102 
103         return NF_ACCEPT;
104 }
105 
106 /* Called when a new connection for this protocol found. */
107 static bool icmp_new(struct nf_conn *ct, const struct sk_buff *skb,
108                      unsigned int dataoff, unsigned int *timeouts)
109 {
110         static const u_int8_t valid_new[] = {
111                 [ICMP_ECHO] = 1,
112                 [ICMP_TIMESTAMP] = 1,
113                 [ICMP_INFO_REQUEST] = 1,
114                 [ICMP_ADDRESS] = 1
115         };
116 
117         if (ct->tuplehash[0].tuple.dst.u.icmp.type >= sizeof(valid_new) ||
118             !valid_new[ct->tuplehash[0].tuple.dst.u.icmp.type]) {
119                 /* Can't create a new ICMP `conn' with this. */
120                 pr_debug("icmp: can't create new conn with type %u\n",
121                          ct->tuplehash[0].tuple.dst.u.icmp.type);
122                 nf_ct_dump_tuple_ip(&ct->tuplehash[0].tuple);
123                 return false;
124         }
125         return true;
126 }
127 
128 /* Returns conntrack if it dealt with ICMP, and filled in skb fields */
129 static int
130 icmp_error_message(struct net *net, struct nf_conn *tmpl, struct sk_buff *skb,
131                  enum ip_conntrack_info *ctinfo,
132                  unsigned int hooknum)
133 {
134         struct nf_conntrack_tuple innertuple, origtuple;
135         const struct nf_conntrack_l4proto *innerproto;
136         const struct nf_conntrack_tuple_hash *h;
137         const struct nf_conntrack_zone *zone;
138         struct nf_conntrack_zone tmp;
139 
140         NF_CT_ASSERT(skb->nfct == NULL);
141         zone = nf_ct_zone_tmpl(tmpl, skb, &tmp);
142 
143         /* Are they talking about one of our connections? */
144         if (!nf_ct_get_tuplepr(skb,
145                                skb_network_offset(skb) + ip_hdrlen(skb)
146                                                        + sizeof(struct icmphdr),
147                                PF_INET, net, &origtuple)) {
148                 pr_debug("icmp_error_message: failed to get tuple\n");
149                 return -NF_ACCEPT;
150         }
151 
152         /* rcu_read_lock()ed by nf_hook_slow */
153         innerproto = __nf_ct_l4proto_find(PF_INET, origtuple.dst.protonum);
154 
155         /* Ordinarily, we'd expect the inverted tupleproto, but it's
156            been preserved inside the ICMP. */
157         if (!nf_ct_invert_tuple(&innertuple, &origtuple,
158                                 &nf_conntrack_l3proto_ipv4, innerproto)) {
159                 pr_debug("icmp_error_message: no match\n");
160                 return -NF_ACCEPT;
161         }
162 
163         *ctinfo = IP_CT_RELATED;
164 
165         h = nf_conntrack_find_get(net, zone, &innertuple);
166         if (!h) {
167                 pr_debug("icmp_error_message: no match\n");
168                 return -NF_ACCEPT;
169         }
170 
171         if (NF_CT_DIRECTION(h) == IP_CT_DIR_REPLY)
172                 *ctinfo += IP_CT_IS_REPLY;
173 
174         /* Update skb to refer to this connection */
175         skb->nfct = &nf_ct_tuplehash_to_ctrack(h)->ct_general;
176         skb->nfctinfo = *ctinfo;
177         return NF_ACCEPT;
178 }
179 
180 /* Small and modified version of icmp_rcv */
181 static int
182 icmp_error(struct net *net, struct nf_conn *tmpl,
183            struct sk_buff *skb, unsigned int dataoff,
184            enum ip_conntrack_info *ctinfo, u_int8_t pf, unsigned int hooknum)
185 {
186         const struct icmphdr *icmph;
187         struct icmphdr _ih;
188 
189         /* Not enough header? */
190         icmph = skb_header_pointer(skb, ip_hdrlen(skb), sizeof(_ih), &_ih);
191         if (icmph == NULL) {
192                 if (LOG_INVALID(net, IPPROTO_ICMP))
193                         nf_log_packet(net, PF_INET, 0, skb, NULL, NULL,
194                                       NULL, "nf_ct_icmp: short packet ");
195                 return -NF_ACCEPT;
196         }
197 
198         /* See ip_conntrack_proto_tcp.c */
199         if (net->ct.sysctl_checksum && hooknum == NF_INET_PRE_ROUTING &&
200             nf_ip_checksum(skb, hooknum, dataoff, 0)) {
201                 if (LOG_INVALID(net, IPPROTO_ICMP))
202                         nf_log_packet(net, PF_INET, 0, skb, NULL, NULL, NULL,
203                                       "nf_ct_icmp: bad HW ICMP checksum ");
204                 return -NF_ACCEPT;
205         }
206 
207         /*
208          *      18 is the highest 'known' ICMP type. Anything else is a mystery
209          *
210          *      RFC 1122: 3.2.2  Unknown ICMP messages types MUST be silently
211          *                discarded.
212          */
213         if (icmph->type > NR_ICMP_TYPES) {
214                 if (LOG_INVALID(net, IPPROTO_ICMP))
215                         nf_log_packet(net, PF_INET, 0, skb, NULL, NULL, NULL,
216                                       "nf_ct_icmp: invalid ICMP type ");
217                 return -NF_ACCEPT;
218         }
219 
220         /* Need to track icmp error message? */
221         if (icmph->type != ICMP_DEST_UNREACH &&
222             icmph->type != ICMP_SOURCE_QUENCH &&
223             icmph->type != ICMP_TIME_EXCEEDED &&
224             icmph->type != ICMP_PARAMETERPROB &&
225             icmph->type != ICMP_REDIRECT)
226                 return NF_ACCEPT;
227 
228         return icmp_error_message(net, tmpl, skb, ctinfo, hooknum);
229 }
230 
231 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
232 
233 #include <linux/netfilter/nfnetlink.h>
234 #include <linux/netfilter/nfnetlink_conntrack.h>
235 
236 static int icmp_tuple_to_nlattr(struct sk_buff *skb,
237                                 const struct nf_conntrack_tuple *t)
238 {
239         if (nla_put_be16(skb, CTA_PROTO_ICMP_ID, t->src.u.icmp.id) ||
240             nla_put_u8(skb, CTA_PROTO_ICMP_TYPE, t->dst.u.icmp.type) ||
241             nla_put_u8(skb, CTA_PROTO_ICMP_CODE, t->dst.u.icmp.code))
242                 goto nla_put_failure;
243         return 0;
244 
245 nla_put_failure:
246         return -1;
247 }
248 
249 static const struct nla_policy icmp_nla_policy[CTA_PROTO_MAX+1] = {
250         [CTA_PROTO_ICMP_TYPE]   = { .type = NLA_U8 },
251         [CTA_PROTO_ICMP_CODE]   = { .type = NLA_U8 },
252         [CTA_PROTO_ICMP_ID]     = { .type = NLA_U16 },
253 };
254 
255 static int icmp_nlattr_to_tuple(struct nlattr *tb[],
256                                 struct nf_conntrack_tuple *tuple)
257 {
258         if (!tb[CTA_PROTO_ICMP_TYPE] ||
259             !tb[CTA_PROTO_ICMP_CODE] ||
260             !tb[CTA_PROTO_ICMP_ID])
261                 return -EINVAL;
262 
263         tuple->dst.u.icmp.type = nla_get_u8(tb[CTA_PROTO_ICMP_TYPE]);
264         tuple->dst.u.icmp.code = nla_get_u8(tb[CTA_PROTO_ICMP_CODE]);
265         tuple->src.u.icmp.id = nla_get_be16(tb[CTA_PROTO_ICMP_ID]);
266 
267         if (tuple->dst.u.icmp.type >= sizeof(invmap) ||
268             !invmap[tuple->dst.u.icmp.type])
269                 return -EINVAL;
270 
271         return 0;
272 }
273 
274 static int icmp_nlattr_tuple_size(void)
275 {
276         return nla_policy_len(icmp_nla_policy, CTA_PROTO_MAX + 1);
277 }
278 #endif
279 
280 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
281 
282 #include <linux/netfilter/nfnetlink.h>
283 #include <linux/netfilter/nfnetlink_cttimeout.h>
284 
285 static int icmp_timeout_nlattr_to_obj(struct nlattr *tb[],
286                                       struct net *net, void *data)
287 {
288         unsigned int *timeout = data;
289         struct nf_icmp_net *in = icmp_pernet(net);
290 
291         if (tb[CTA_TIMEOUT_ICMP_TIMEOUT]) {
292                 *timeout =
293                         ntohl(nla_get_be32(tb[CTA_TIMEOUT_ICMP_TIMEOUT])) * HZ;
294         } else {
295                 /* Set default ICMP timeout. */
296                 *timeout = in->timeout;
297         }
298         return 0;
299 }
300 
301 static int
302 icmp_timeout_obj_to_nlattr(struct sk_buff *skb, const void *data)
303 {
304         const unsigned int *timeout = data;
305 
306         if (nla_put_be32(skb, CTA_TIMEOUT_ICMP_TIMEOUT, htonl(*timeout / HZ)))
307                 goto nla_put_failure;
308         return 0;
309 
310 nla_put_failure:
311         return -ENOSPC;
312 }
313 
314 static const struct nla_policy
315 icmp_timeout_nla_policy[CTA_TIMEOUT_ICMP_MAX+1] = {
316         [CTA_TIMEOUT_ICMP_TIMEOUT]      = { .type = NLA_U32 },
317 };
318 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
319 
320 #ifdef CONFIG_SYSCTL
321 static struct ctl_table icmp_sysctl_table[] = {
322         {
323                 .procname       = "nf_conntrack_icmp_timeout",
324                 .maxlen         = sizeof(unsigned int),
325                 .mode           = 0644,
326                 .proc_handler   = proc_dointvec_jiffies,
327         },
328         { }
329 };
330 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
331 static struct ctl_table icmp_compat_sysctl_table[] = {
332         {
333                 .procname       = "ip_conntrack_icmp_timeout",
334                 .maxlen         = sizeof(unsigned int),
335                 .mode           = 0644,
336                 .proc_handler   = proc_dointvec_jiffies,
337         },
338         { }
339 };
340 #endif /* CONFIG_NF_CONNTRACK_PROC_COMPAT */
341 #endif /* CONFIG_SYSCTL */
342 
343 static int icmp_kmemdup_sysctl_table(struct nf_proto_net *pn,
344                                      struct nf_icmp_net *in)
345 {
346 #ifdef CONFIG_SYSCTL
347         pn->ctl_table = kmemdup(icmp_sysctl_table,
348                                 sizeof(icmp_sysctl_table),
349                                 GFP_KERNEL);
350         if (!pn->ctl_table)
351                 return -ENOMEM;
352 
353         pn->ctl_table[0].data = &in->timeout;
354 #endif
355         return 0;
356 }
357 
358 static int icmp_kmemdup_compat_sysctl_table(struct nf_proto_net *pn,
359                                             struct nf_icmp_net *in)
360 {
361 #ifdef CONFIG_SYSCTL
362 #ifdef CONFIG_NF_CONNTRACK_PROC_COMPAT
363         pn->ctl_compat_table = kmemdup(icmp_compat_sysctl_table,
364                                        sizeof(icmp_compat_sysctl_table),
365                                        GFP_KERNEL);
366         if (!pn->ctl_compat_table)
367                 return -ENOMEM;
368 
369         pn->ctl_compat_table[0].data = &in->timeout;
370 #endif
371 #endif
372         return 0;
373 }
374 
375 static int icmp_init_net(struct net *net, u_int16_t proto)
376 {
377         int ret;
378         struct nf_icmp_net *in = icmp_pernet(net);
379         struct nf_proto_net *pn = &in->pn;
380 
381         in->timeout = nf_ct_icmp_timeout;
382 
383         ret = icmp_kmemdup_compat_sysctl_table(pn, in);
384         if (ret < 0)
385                 return ret;
386 
387         ret = icmp_kmemdup_sysctl_table(pn, in);
388         if (ret < 0)
389                 nf_ct_kfree_compat_sysctl_table(pn);
390 
391         return ret;
392 }
393 
394 static struct nf_proto_net *icmp_get_net_proto(struct net *net)
395 {
396         return &net->ct.nf_ct_proto.icmp.pn;
397 }
398 
399 struct nf_conntrack_l4proto nf_conntrack_l4proto_icmp __read_mostly =
400 {
401         .l3proto                = PF_INET,
402         .l4proto                = IPPROTO_ICMP,
403         .name                   = "icmp",
404         .pkt_to_tuple           = icmp_pkt_to_tuple,
405         .invert_tuple           = icmp_invert_tuple,
406         .print_tuple            = icmp_print_tuple,
407         .packet                 = icmp_packet,
408         .get_timeouts           = icmp_get_timeouts,
409         .new                    = icmp_new,
410         .error                  = icmp_error,
411         .destroy                = NULL,
412         .me                     = NULL,
413 #if IS_ENABLED(CONFIG_NF_CT_NETLINK)
414         .tuple_to_nlattr        = icmp_tuple_to_nlattr,
415         .nlattr_tuple_size      = icmp_nlattr_tuple_size,
416         .nlattr_to_tuple        = icmp_nlattr_to_tuple,
417         .nla_policy             = icmp_nla_policy,
418 #endif
419 #if IS_ENABLED(CONFIG_NF_CT_NETLINK_TIMEOUT)
420         .ctnl_timeout           = {
421                 .nlattr_to_obj  = icmp_timeout_nlattr_to_obj,
422                 .obj_to_nlattr  = icmp_timeout_obj_to_nlattr,
423                 .nlattr_max     = CTA_TIMEOUT_ICMP_MAX,
424                 .obj_size       = sizeof(unsigned int),
425                 .nla_policy     = icmp_timeout_nla_policy,
426         },
427 #endif /* CONFIG_NF_CT_NETLINK_TIMEOUT */
428         .init_net               = icmp_init_net,
429         .get_net_proto          = icmp_get_net_proto,
430 };
431 

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