1clatd(8) clatd - a CLAT implementation for Linux clatd(8)
2
6 clatd - a CLAT / SIIT-DC Edge Relay implementation for Linux
7
9 clatd implements the CLAT component of the 464XLAT network architecture
10 specified in RFC 6877. It allows an IPv6-only host to have IPv4
11 connectivity that is translated to IPv6 before being routed to an
12 upstream PLAT (which is typically a Stateful NAT64 operated by the ISP)
13 and there translated back to IPv4 before being routed to the IPv4
14 internet. This is especially useful when local applications on the host
15 requires actual IPv4 connectivity or cannot make use of DNS64 (for
16 example because they use legacy AF_INET socket calls, or if they are
17 simply not using DNS64).
18 clatd may also be used to implement an SIIT-DC Edge Relay as described
20 in RFC 7756. In this scenario, the PLAT is in reality a SIIT-DC Border
21 Relay (see RFC 7755) instead of a Stateful NAT64 (see RFC6146). When
22 used as a SIIT-DC Edge Relay, you will probably want to manually
23 configure the settings clat-v4-addr, clat-v6-addr, and plat-prefix to
24 mirror the SIIT-DC Border Relay's configuration.
25 It relies on the software package TAYGA by Nathan Lutchansky for the
27 actual translation of packets between IPv4 and IPv6 (RFC 6145) TAYGA
28 may be downloaded from its home page at <http://www.litech.org/tayga/>.
29
31 clatd [options]
32
34 -q Quiet mode; suppress normal output. This is the same as setting
35 quiet=1. Warnings and errors are still outputted, to silence those
36 too, repeat -q.
37 -d Enable debugging output. This is the same as setting debug=1.
39 Repeat for even more debugging output, which is the equivalent of
40 setting debug=2.
41 -c conf-file
43 Read configuration settings from conf-file. See section
44 CONFIGURATION below for more info.
45 -h, --help
47 Print a brief usage help and exit.
48 key=value
50 Set configuration key to value, overriding any setting found in the
51 configuration file. Refer to the section CONFIGURATION below for
52 more info.
53
55 clatd is meant to be run under a daemonising control process such as
56 systemd, upstart, or similar. It is further meant to be (re)started
57 whenever a network interface goes up/down as this might mean a change
58 in the PLAT availability or which prefixes/addresses needs to be used
59 for the CLAT to work. It may also be run directly from the command
60 line. It will run until killed with SIGINT (^C) or SIGTERM, at which
61 point it will clean up after itself and exit gracefully.
62 See the scripts/ directory in the source distribution for some examples
64 on how to invoke it it.
65
67 The following commands will quickly download and install the latest
68 version of clatd and its dependencies:
69 git clone https://github.com/toreanderson/clatd
71 sudo make -C clatd install installdeps
72 This will install clatd to /usr/sbin, plus install systemd, upstart,
74 and/or NetworkManager scripts if your distribution appears to be using
75 them, and install all the dependencies. Note that TAYGA isn't available
76 in all RPM-based distros (in particular RHEL and its clones). It is
77 however available in EPEL (see <https://fedoraproject.org/wiki/EPEL>).
78
80 clatd is designed to be able to run without any user-supplied
81 configuration in most cases. However, user-specified configuration
82 settings may be added to the configuration file, the path to which may
83 be given on the command line using the -c option, or if it is not, the
84 default location /etc/clatd.conf is used. Configuration settings may
85 also be given directly on the command line when starting clatd, which
86 takes precedence over settings in the configuration file.
87 Settings are of the form key=value. A list of recognised keys and their
89 possible values follow below:
90 quiet=integer (default: 0)
92 Set this to 1 to suppress normal output from clatd. This is the
93 same as providing the command line option -q. Set it to 2 to
94 additionally suppress warnings and errors. Note that this does not
95 suppress debugging output.
96 debug=integer (default: 0)
98 Set this to 1 to get debugging output from clatd, or 2 to get even
99 more of the stuff. These are the equivalent of providing the
100 command line option -d the specified number of times.
101 script-up=string (no default)
103 Specify a custom script to be run when clatd is starting up. The
104 invocation of this script is the last thing that happens before
105 TAYGA starts up, so all the preparations have been completed at
106 that point (i.e., the clat-dev exists and has routing/addressing
107 configured, forwarding has been enabled, and so on).
108 The script is run by the system shell, so you can do everything you
110 could in an interactive shell: run multiple commands by separating
111 them by semi-colon or double ampersands, use standard if/else
112 statements, use variable substitutions, redirect output to files,
113 set up command pipelines, and so on. However it must all be on one
114 line, so if you want to do complex things or use some other
115 programming language it's probably better to put the script itself
116 in a separate executable file and just make script-up invoke that
117 file instead.
118 If the script returns a nonzero exit status, this is considered a
120 fatal error, and clatd will abort. This can be prevented by
121 appending || true at the end of the script.
122 All of clatd's configuration settings are available as standard
124 variables in the script's environment (hyphens are replaced with
125 underscores).
126 Logging or debug messages from the script may simply be sent to
128 stdout, where it will be picked up by the init system along with
129 clatd's own output. The script may of course consult the $quiet and
130 $debug environment variables in order to determine how much output
131 is appropriate.
132 The script should not be enclosed in quotes in the configuration
134 file (even though it contains whitespace). For example:
135 script-up=echo `date -Ins`: clatd started on $clat_dev | tee -a
137 ~/clatd.log
138 If on the other hand you want to supply a script-up containing
140 whitespace directly clatd's command line, quoting is required in
141 order to prevent the shell from splitting it up and into multiple
142 command line arguments. For example:
143 clatd 'script-up=ip route add 192.0.2.0/24 dev $clat_dev || true'
145 script-down=string (no default)
147 This works exactly the same as script-up, only that this script is
148 run right after TAYGA has exited, before the clean-up process of
149 restoring any settings that were changed.
150 An unsuccessful exit code from script-down will cause clatd to exit
152 unsuccessfully too. Beyond that an unsuccessful exit won't change
153 anything, because script-down is invoked at a point in time where
154 the only thing left for clatd to do is to clean up after itself and
155 exit anyway.
156 clat-dev=string (default: clat)
158 The name of the network device used by the CLAT. There should be no
159 reason to change the default, unless you plan on running multiple
160 instances of clatd simultaneously.
161 clat-v4-addr=ipv4-address (default: 192.0.0.1)
163 The IPv4 address that will be assigned to the CLAT device. Local
164 applications will bind to this address when communicating with
165 external IPv4 destinations. In a standard 464XLAT environment with
166 a stateful NAT64 serving as the PLAT, there should be no need to
167 change the default.
168 When using clatd as an SIIT-DC Edge Relay (RFC 7756), you will want
170 to set this to the IPv4 Service Address configured in the SIIT-DC
171 Border Relay. This way, local applications can correctly identify
172 which public address they'll be using on the IPv4 internet, and
173 will be able to provide fully functional references to it in
174 application-level payload, and so on.
175 The default address is one from RFC 7335.
177 clat-v6-addr=ipv6-address (default: auto-generated)
179 The IPv6 address of the CLAT. Traffic to/from the clat-v4-addr will
180 be translated into this address. When using clatd as an SIIT-DC
181 Edge Relay, you will want to set this to the same IPv6 address in
182 the Explicit Address Mapping configured in the SIIT-DC Border
183 Relay.
184 By default, clatd will attempt to figure out which network device
186 will be used for traffic towards the PLAT, see if there is any
187 SLAAC-based globally scoped addresses on it (i.e., a /64 with
188 '0xfffe' in the middle of the Interface ID), and will if so
189 substitute that '0xfffe' value with '0xc1a7' ("clat") to generate a
190 CLAT IPv6 address.
191 If only a non-SLAAC global address is found on the PLAT-facing
193 device, clatd will substitute its Interface ID with a random
194 integer and use the result as the CLAT IPv6 address. It will only
195 do so if the prefix length is /120 or smaller, as otherwise the
196 risk of IID collisions is considered to be too high. Note that on
197 most Perl platforms, the rand() function is limited to 48 bits,
198 which means that for longer IIDs, the least significant bits will
199 be all 0.
200 If multiple addresses are found in either category, the one that
202 shares the longest common prefix with the PLAT prefix will be
203 preferred when deriving the CLAT IPv6 address according to the
204 algorithm described above.
205 dns64-servers=srv1,[srv2,..] (default: use system resolver)
207 Comma-separated list of DNS64 servers to use when discovering the
208 PLAT prefix using the method described in RFC 7050. By default, the
209 system resolver is used, but it might be useful to override this in
210 case your ISP doesn't provide you with a DNS64-enabled name server,
211 and you want to test clatd using any of the public DNS64/NAT64
212 instances on the internet. The first PLAT prefix encountered will
213 be used.
214 cmd-ip=path (default: assume in $PATH)
216 Path to the ip binary from the iproute2 package available at
217 <https://www.kernel.org/pub/linux/utils/net/iproute2>. Required.
218 cmd-ip6tables=path (default: assume in $PATH)
220 Path to the ip6tables binary from the netfilter package available
221 at <http://netfilter.org>. Only required for adding ip6tables rules
222 (see the ip6tables-enable configuration setting).
223 cmd-tayga=path (default: assume in $PATH)
225 Path to the tayga binary from the TAYGA package available at
226 <http://www.litech.org/tayga>. Required.
227 forwarding-enable=bool (default: yes)
229 Controls whether or not clatd should enable IPv6 forwarding if
230 necessary. IPv6 forwarding is necessary for clatd to work
231 correctly. It will also ensure that the accept_ra sysctl is to '2'
232 for all devices have it set to '1', in order to prevent any
233 connectivity loss as a result of enabling forwarding.
234 All sysctls that are modified will be restored to their original
236 values when clatd is shutting down.
237 ip6tables-enable=bool (default: see below)
239 Controls whether or not clatd should insert ip6tables rules that
240 permit the forwarding of IPv6 traffic between the CLAT and PLAT
241 devices. Such forwarding must be permitted for clatd to work
242 correctly. Any rules added will be removed when clatd is shutting
243 down.
244 The default is yes if the ip6tables_filter kernel module is loaded,
246 no if it is not.
247 plat-dev (default: auto-detect)
249 Which network device is facing the PLAT (NAT64). By default, this
250 is auto-detected by performing a route table lookup towards the
251 PLAT prefix. This setting is used when setting up generating the
252 CLAT IPv6 address, and when setting up ip6tables rules and Proxy-ND
253 entries.
254 plat-prefix (default: auto-detect)
256 The IPv6 translation prefix into which the PLAT maps the IPv4
257 internet. See RFC 6052 for a closer description. By default, this
258 is auto-detected from DNS64 answers using the method in RFC 7050.
259 proxynd-enable (default: yes)
261 Controls whether or not clatd should add a Proxy-ND entry for the
262 CLAT IPv6 address on the network device facing the PLAT. This is
263 probably necessary on Ethernet networks (otherwise the upstream
264 IPv6 router won't know where to send packets to the CLAT's IPv6
265 address), but likely not necessary on point-to-point links like PPP
266 or 3GPP mobile broadband, as in those cases IPv6 ND isn't used.
267 However it doesn't hurt to add Proxy-ND entries in that case,
268 either.
269 Any entries added wil be removed when clatd is shutting down.
271 tayga-conffile (default: use a temporary file)
273 Where to write the TAYGA configuration file. By default, a
274 temporary file will be created (and also deleted when clatd is
275 shutting down), but you may also specify an explicit configuration
276 file here, which will not be deleted on shutdown.
277 tayga-v4-addr (default: 192.0.0.2)
279 The IPv4 address assigned to the TAYGA process. This is used for
280 emitting ICMPv4 errors back to the host (i.e., it will show up as
281 the first hop when tracerouting to IPv4 destinations), and you may
282 also ping it to verify that the TAYGA process is still alive and
283 well.
284 The default address is one from RFC 7335.
286 v4-conncheck-enable=bool (default: yes)
288 Whether or not to check if the system has IPv4 connectivity before
289 starting the CLAT. If it does, then clatd will simply exit without
290 doing anything. This is meant so that you can always enable clatd
291 to the system startup scripts or network-up event scripts (such as
292 NetworkManager's dispatcher scripts), but not have clatd
293 interfering with native IPv4 connectivity when this is present.
294 If you want to always start the CLAT whenever possible, even though
296 the system has IPv4 connectivity, disable this setting. You may
297 instead use the v4-defaultroute-enable and v4-defaultroute-metric
298 settings to prevent clatd from interfering with native IPv4
299 connectivity.
300 Note that enabling v4-defaultroute-replace will override
302 v4-conncheck-enable and unconditionally disable IPv4 connectivity
303 checking.
304 v4-conncheck-delay=seconds (default: 10)
306 When performing an IPv4 connectivity check, wait this number of
307 seconds before actually doing anything. This is to avoid a race
308 condition where for example IPv6 SLAAC finshes and triggers a
309 network-up event script to start clatd, while IPv4 DHCPv4 is still
310 running in the background. This is at least a likely scenario when
311 using NetworkManager, as it will start the dispatcher scripts as
312 soon as either IPv4 or IPv6 has completed, and IPv6 SLAAC is
313 typically faster than IPv4 DHCPv4.
314 Set it to 0 to perform the check immediately.
316 v4-defaultroute-enable=bool (default: yes)
318 Whether or not to add an IPv4 default route pointing to the CLAT.
319 In a typical 464XLAT environment, you want this. However when using
320 clatd in an environment where native IPv4 connectivity is also
321 present, you might want to disable this and instead control
322 manually which IPv4 destinations is reached through the CLAT and
323 which are not.
324 v4-defaultroute-replace=bool (default: no)
326 Instructs clatd to remove any pre-existing IPv4 default routes,
327 replacing it with one pointing to the CLAT (assuming
328 v4-defaultroute-enable is yes). The replacement is temporary, any
329 pre-existing routes that were removed will be restored when clatd
330 is shutting down.
331 Note that nothing prevents software like a connection manager or a
333 DHCPv4 client daemon from re-adding any replaced routes while clatd
334 is running.
335 If you enable v4-defaultroute-replace while at the same time
337 disabling v4-defaultroute-enable, clatd will remove any pre-
338 existing IPv4 default routes but not add any of its own.
339 Setting v4-defaultroute-replace to yes will disable the IPv4
341 connectivity check.
342 v4-defaultroute-metric=integer (default: 2048)
344 The metric of the IPv4 default route pointing to the CLAT. The
345 default is chosen because it is higher than that of a native IPv4
346 default route added by NetworkManager, which makes it so that the
347 native IPv4 connectivity is preferred if present.
348 v4-defaultroute-mtu=integer (default: 1260)
350 The MTU of the default route pointing to the CLAT. The default is
351 the default IPv6 MTU used by TAYGA (1280, which in turn comes from
352 RFC 6145) minus 20 to compensate for the difference in header size
353 between IPv4 and IPv6. This prevents outbound packets from having
354 to be fragmented by TAYGA, and also makes local applications
355 advertise a TCP MSS to their remote peers that prevent them from
356 sending packets beck to us that would require fragmentation.
357 If you know that the IPv6 Path MTU between the host and the PLAT is
359 larger than 1280, you may increase this, but then you should also
360 recompile TAYGA with a larger ipv6_offlink_mtu setting in
361 conffile.c.
362 v4-defaultroute-advmss=integer (default: v4-defaultroute-mtu - 40)
364 The "advmss" value assigned to the the default route potining to
365 the CLAT. This controls the advertised TCP MSS value for TCP
366 connections made through the CLAT.
367 You should normally not need to set this. By default the value is
369 calculated by taking the value of v4-defaultroute-mtu and
370 substracting 40 (20 bytes for the IPv4 header + 20 bytes for the
371 TCP header). If v4-defaultroute-mtu is unset or 0, there is no
372 default.
373
375 clatd will not be able to acquire an IPv6 address for the CLAT if SLAAC
376 isn't used. RFC 6877 suggests DHCPv6 IA_PD should be attempted in this
377 case, but this isn't currently implemented.
378 clatd will not attempt to perform Duplicate Address Detection for the
380 IPv6 address it generates. This is a violation of RFC 6877.
381 clatd will not attempt to perform a connectivity check to a discovered
383 PLAT prefix before setting up the CLAT, as RFC 7050 suggest it should.
384
386 If you are experiencing any bugs or have any feature requests, head
387 over to <https://github.com/toreanderson/clatd/issues> and submit a new
388 issue (if someone else hasn't already done so). Please make sure to
389 include logs with full debugging output (using -d -d on the command
390 line or debug=2 in the configuration file) when reporting a bug.
391
393 Copyright (c) 2014-2019 Tore Anderson <tore@fud.no>
394 Permission is hereby granted, free of charge, to any person obtaining a
396 copy of this software and associated documentation files (the
397 "Software"), to deal in the Software without restriction, including
398 without limitation the rights to use, copy, modify, merge, publish,
399 distribute, sublicense, and/or sell copies of the Software, and to
400 permit persons to whom the Software is furnished to do so, subject to
401 the following conditions:
402 The above copyright notice and this permission notice shall be included
404 in all copies or substantial portions of the Software.
405 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
407 OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
408 MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
409 IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
410 CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
411 TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
412 SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
413
415 ip(8), ip6tables(8), tayga(8), tayga.conf(5)
416 RFC 6052, RFC 6145, RFC 6146, RFC 6877, RFC 7050, RFC 7335 RFC 7755,
418 RFC 7756, RFC 7757
419perl v5.36.0 2022-07-20 clatd(8)