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17 .Dd February 17, 2020
18 .Dt IPNAT 7I
19 .Os
20 .Sh NAME
21 .Nm ipnat
22 .Nd IP Filter/NAT module interface
23 .Sh DESCRIPTION
24 The
25 .Sy ipnat
26 device provides interaction with the NAT features of the illumos IP Filter.
27 .Sh APPLICATION PROGRAMMING INTERFACE
28 The NAT features programming model is a component of the illumos IP Filter and
29 is accessed via the NAT device file
30 .Pa /dev/ipnat .
31 Opening the device for
32 reading or writing determines which ioctl calls can be successfully made.
33 .Sh IOCTLS
34 The caller must construct a
35 .Vt ipfobj
36 structure when issuing a
37 .Sy SIOCGNATL
38 or
39 SIOCSTPUT
40 ioctl.
41 The
42 .Vt ipfobj
43 structure is then passed
44 to the ioctl call and is filled out with
45 .Fa ipfo_type
46 set to
47 .Dv IPFOBJ_ Ns value .
48 .Dv IPFOBJ_ Ns value
49 provides a matching name for the structure, while
50 .Fa ipfo_size
51 is set to the total size of the structure being passed and
52 .Fa ipfo_ptr
53 is set to the structure address.
54 The
55 .Fa ipfo_rev
56 structure should be set to the current value of
57 .Dv IPFILTER_VERSION ,
58 while
59 .Fa ipfo_offset
60 and
61 .Fa ipfo_xxxpad
62 should be set to 0.
63 .Bd -literal -offset 2n
64 /*
65 * Structure used with SIOCGNATL/SIOCSTPUT.
66 */
67
68 /*
69 * Object structure description. For passing through in ioctls.
70 */
71 typedef struct ipfobj {
72 u_32_t ipfo_rev; /* IPFilter version (IPFILTER_VERSION) */
73 u_32_t ipfo_size; /* size of object at ipfo_ptr */
74 void *ipfo_ptr; /* pointer to object */
75 int ipfo_type; /* type of object being pointed to */
76 int ipfo_offset; /* bytes from ipfo_ptr where to start */
77 u_char ipfo_xxxpad[32]; /* reserved for future use */
78 } ipfobj_t;
79
80 #define IPFILTER_VERSION 4010901 /* IPFilter version */
81 #define IPFOBJ_NATSAVE 8 /* struct nat_save */
82 #define IPFOBJ_NATLOOKUP 9 /* struct natlookup */
83 .Ed
84 .Pp
85 The following
86 .Xr ioctl 2
87 calls may be used to manipulate the ipnat sub-system inside of ipf.
88 Note that the ipnat driver only accept calls from applications
89 using the same data model as the kernel.
90 In other words, 64-bit kernels can only accept calls from 64-bit applications.
91 Calls from 32-bit applications fail
92 with
93 .Er EINVAL .
94 .Bl -tag -width SIOCSTLCK
95 .It Dv SIOCSTLCK
96 Set or clear the NAT lock to prevent table updates attributable to packet
97 flow-through.
98 .It Dv SIOCGNATL
99 Search the NAT table for the rdr entry that matches the fields in the natlookup
100 structure.
101 The caller must populate the structure with the address/port
102 information of the accepted TCP connection
103 .Pq Fa nl_inip , Fa nl_inport
104 and the
105 address/port information of the peer
106 .Pq Fa nl_outip , Fa nl_outport .
107 The
108 .Fa nl_flags
109 field must have the
110 .Dv IPN_TCP
111 option set.
112 All other fields must be set to 0.
113 If the call succeeds,
114 .Fa nl_realip
115 and
116 .Fa nl_realport
117 are set to the real destination address and port, respectively.
118 The
119 .Fa nl_inport
120 and
121 .Fa nl_outport
122 fields must be in host byte order.
123 If
124 .Dv IPN_FINDFORWARD
125 is set in
126 .Fa nl_flags ,
127 a check is made to see if it is
128 possible to create an outgoing NAT session by checking if a packet coming from
129 .Pq Fa nl_realip , Fa nl_realport
130 and destined for
131 .Pq Fa nl_outip , Fa nl_outport
132 can be translated.
133 If translation is possible, the flag remains set, otherwise it is
134 cleared in the structure returned to the caller.
135 .Bd -literal -offset indent
136 /*
137 * Structure used with SIOCGNATL.
138 */
139 typedef struct natlookup {
140 i6addr_t nl_inipaddr;
141 i6addr_t nl_outipaddr;
142 i6addr_t nl_realipaddr;
143 int nl_v;
144 int nl_flags;
145 u_short nl_inport;
146 u_short nl_outport;
147 u_short nl_realport;
148 } natlookup_t
149
150 #define nl_inip nl_inipaddr.in4
151 #define nl_outip nl_outipaddr.in4
152 #define nl_realip nl_realipaddr.in4
153 #define nl_inip6 nl_inipaddr.in6
154 #define nl_outip6 nl_outipaddr.in6
155 #define nl_realip6 nl_realipaddr.in6
156
157 /*
158 * Accepted values for nl_flags
159 */
160 #define IPN_TCP 0x00001
161 #define IPN_FINDFORWARD 0x400000
162 .Ed
163 .It Dv SIOCSTPUT
164 Move a NAT mapping structure from user space into the kernel.
165 This ioctl is used by
166 .Xr ipfs 1M
167 to restore NAT sessions saved in
168 .Pa /var/db/ipf/ipnat.ipf .
169 The
170 .Vt nat_save
171 structure must have its
172 .Fa ipn_nat
173 and
174 .Fa ipn_ipnat
175 structures filled out correctly.
176 Fields not assigned a value must be initialised to 0.
177 All pointer fields are adjusted, as appropriate, once the
178 structure is passed into the kernel and none are preserved.
179 .Pp
180 To create a translation, the following fields must be set:
181 .\" Force item bodies to next line using 2n width
182 .Bl -tag -width 2n
183 .It "Interface name"
184 The interface name on which the host is to be exited must be
185 set in
186 .Fa nat_ifnames[0] .
187 .It "Local IP address and port number"
188 The connection's local IP address and port
189 number are stored in network byte order using
190 .Fa nat_inip Ns / Ns Fa nat_inport .
191 .It "Destination address/port"
192 The destination address/port are stored in
193 .Fa nat_oip Ns / Ns Fa nat_oport .
194 .It "Target address/port"
195 The translation's target address/port is stored in
196 .Fa nat_outip Ns / Ns Fa nat_outport .
197 .El
198 .Pp
199 The caller must also precalculate the checksum adjustments necessary to
200 complete the translation and store those values in
201 .Fa nat_sumd
202 (delta required for TCP header) and
203 .Fa nat_ipsumd
204 (delta required for IP header).
205 .Bd -literal -offset indent
206 /*
207 * Structures used with SIOCSTPUT.
208 */
209 typedef struct nat_save {
210 void *ipn_next;
211 struct nat ipn_nat;
212 struct ipnat ipn_ipnat;
213 struct frentry ipn_fr;
214 int ipn_dsize;
215 char ipn_data[4];
216 } nat_save_t;
217
218 typedef struct nat {
219 ipfmutex_t nat_lock;
220 struct nat *nat_next;
221 struct nat **nat_pnext;
222 struct nat *nat_hnext[2];
223 struct nat **nat_phnext[2];
224 struct hostmap *nat_hm;
225 void *nat_data;
226 struct nat **nat_me;
227 struct ipstate *nat_state;
228 struct ap_session *nat_aps;
229 frentry_t *nat_fr;
230 struct ipnat *nat_ptr;
231 void *nat_ifps[2];
232 void *nat_sync;
233 ipftqent_t nat_tqe;
234 u_32_t nat_flags;
235 u_32_t nat_sumd[2];
236 u_32_t nat_ipsumd;
237 u_32_t nat_mssclamp;
238 i6addr_t nat_inip6;
239 i6addr_t nat_outip6;
240 i6addr_t nat_oip6;
241 U_QUAD_T nat_pkts[2];
242 U_QUAD_T nat_bytes[2];
243 union {
244 udpinfo_t nat_unu;
245 tcpinfo_t nat_unt;
246 icmpinfo_t nat_uni;
247 greinfo_t nat_ugre;
248 } nat_un;
249 u_short nat_oport;
250 u_short nat_use;
251 u_char nat_p;
252 int nat_dir;
253 int nat_ref;
254 int nat_hv[2];
255 char nat_ifnames[2][LIFNAMSIZ];
256 int nat_rev;
257 int nat_v;
258 } nat_t;
259
260 #define nat_inip nat_inip6.in4
261 #define nat_outip nat_outip6.in4
262 #define nat_oip nat_oip6.in4
263 #define nat_inport nat_un.nat_unt.ts_sport
264 #define nat_outport nat_un.nat_unt.ts_dport
265 /*
266 * Values for nat_dir
267 */
268 #define NAT_INBOUND 0
269 #define NAT_OUTBOUND 1
270 /*
271 * Definitions for nat_flags
272 */
273 #define NAT_TCP 0x0001 /* IPN_TCP */
274 .Ed
275 .El
276 .Sh EXAMPLES
277 The following example shows how to prepare and use
278 .Fa SIOCSTPUT
279 to insert a NAT session directly into the table.
280 Note that the usual TCP/IP code is omitted is this example.
281 .Pp
282 In the code segment below,
283 .Fa incoming_fd
284 is the TCP connection file descriptor
285 that is accepted as part of the redirect process, while
286 .Fa remote_fd
287 is the outgoing TCP connection to the remote server being translated back to the
288 original IP address/port pair.
289 .Pp
290 Note \(em
291 The following ipnat headers must be included before you can use the code shown
292 in this example:
293 .Bd -literal -offset 2n
294 #include <netinet/in.h>
295 #include <arpa/inet.h>
296 #include <net/if.h>
297 #include <netinet/ipl.h>
298 #include <netinet/ip_compat.h>
299 #include <netinet/ip_fil.h>
300 #include <netinet/ip_nat.h>
301 #include <string.h>
302 #include <fcntl.h>
303 .Ed
304 .Pp
305 Note \(em
306 In the example below, various code fragments have been excluded to enhance
307 clarity.
308 .Bd -literal -offset 2n
309 int
310 translate_connection(int incoming_fd)
311 {
312 struct sockaddr_in usin;
313 struct natlookup nlp;
314 struct nat_save ns;
315 struct ipfobj obj;
316 struct nat *nat;
317 int remote_fd;
318 int nat_fd;
319 int onoff;
320
321 memset(&ns, 0, sizeof(ns));
322 nat = &ns.ipn_nat
323
324 namelen = sizeof(usin);
325 getsockname(remote_fd, (struct sockaddr *)&usin, &namelen);
326
327 namelen = sizeof(sin);
328 getpeername(incoming_fd, (struct sockaddr *) &sin, &namelen);
329
330 namelen = sizeof(sloc);
331 getsockname(incoming_fd, (struct sockaddr *) &sloc, &namelen);
332
333 bzero((char *) &obi, sizeof(obj));
334 obj.ipfo_rev = IPFILTER_VERSION;
335 obj.ipfo_size = sizeof(nlp);
336 obj.ipfo_ptr = &nip;
337 obj.ipfo_type = IPFOBJ_NATLOOKUP;
338
339 /*
340 * Build up the NAT natlookup structure.
341 */
342 bzero((char *) &nlp, sizeof(nlp));
343 nlp.nl_outip = sin.sin_addr;
344 nlp.nl_inip = sloc.sin_addr;
345 nlp.nl_flags = IPN_TCP;
346 nlp.nl_outport = ntohs(sin.sin_port);
347 nlp.nl_inport = ntohs(sloc.sin_port);
348
349 /*
350 * Open the NAT device and lookup the mapping pair.
351 */
352 nat_fd = open(IPNAT_NAME, O_RDWR);
353 if (ioctl(nat_fd, SIOCGNATL, &obj) != 0)
354 return -1;
355
356 nat->nat_inip = usin.sin_addr;
357 nat->nat_outip = nlp.nl_outip;
358 nat->nat_oip = nlp.nl_realip;
359
360 sum1 = LONG_SUM(ntohl(usin.sin_addr.s_addr)) +
361 ntohs(usin.sin_port);
362 sum2 = LONG_SUM(ntohl(nat->nat_outip.s_addr)) +
363 ntohs(nlp.nl_outport);
364 CALC_SUMD(sum1, sum2, sumd);
365 nat->nat_sumd[0] = (sumd & 0xffff) + (sumd >> 16);
366 nat->nat_sumd[1] = nat->nat_sumd[0];
367
368 sum1 = LONG_SUM(ntohl(usin.sin_addr.s_addr));
369 sum2 = LONG_SUM(ntohl(nat->nat_outip.s_addr));
370 CALC_SUMD(sum1, sum2, sumd);
371 nat->nat_ipsumd = (sumd & 0xffff) + (sumd >> 16);
372
373 nat->nat_inport = usin.sin_port;
374 nat->nat_outport = nlp.nl_outport;
375 nat->nat_oport = nlp.nl_realport;
376
377 nat->nat_flags = IPN_TCPUDP;
378
379 /*
380 * Prepare the ipfobj structure, accordingly.
381 */
382 bzero((char *)&obi, sizeof(obj));
383 obj.ipfo_rev = IPFILTER_VERSION;
384 obj.ipfo_size = sizeof(*nsp);
385 obj.ipfo_ptr = nsp;
386 obj.ipfo_type = IPFOBJ_NATSAVE;
387
388 onoff = 1;
389 if (ioctl(nat_fd, SIOCSTPUT, &obj) != 0)
390 fprintf(stderr, "Error occurred\en");
391
392 return connect(rem_fd, (struct sockaddr)&usin, sizeof(usin));
393 }
394 .Ed
395 .Sh ERRORS
396 .Bl -tag -width Er
397 .It Er EPERM
398 The device has been opened for reading only.
399 To succeed, the ioctl call must be opened for both reading and writing.
400 The call may be returned if it is
401 privileged and the calling process did not assert
402 .Brq Sy PRIV_SYS_NET_CONFIG
403 in the effective set.
404 .It Er ENOMEM
405 More memory was allocated than the kernel can provide.
406 The call may also be returned if the application inserts a NAT entry that
407 exceeds the hash bucket chain's maximum length.
408 .It Er EFAULT
409 The calling process specified an invalid pointer in the ipfobj structure.
410 .It Er EINVAL
411 The calling process detected a parameter or field set to an unacceptable value.
412 .It Er EEXIST
413 The calling process, via
414 .Dv SIOCSTPUT ,
415 attempted to add a NAT entry that already exists in the NAT table.
416 .It Er ESRCH
417 The calling process called
418 .Dv SIOCSTPUT
419 before setting the
420 .Dv SI_NEWFR
421 flag and providing a pointer in the
422 .Fa nat_fr
423 field that cannot be found in the current rule set.
424 .It Er EACCES
425 The calling process issued a
426 .Dv SIOCSTPUT
427 before issuing a
428 .Dv SIOCSTLCK .
429 .El
430 .Sh INTERFACE STABILITY
431 Committed
432 .Sh SEE ALSO
433 .Xr ipfs 1M ,
434 .Xr ipnat 1M ,
435 .Xr ioctl 2 ,
436 .Xr attributes 5