From 84adefa331c4159d432d22840663c38f155cd4c1 Mon Sep 17 00:00:00 2001 From: Erlang/OTP Date: Fri, 20 Nov 2009 14:54:40 +0000 Subject: The R13B03 release. --- erts/doc/src/inet_cfg.xml | 397 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 397 insertions(+) create mode 100644 erts/doc/src/inet_cfg.xml (limited to 'erts/doc/src/inet_cfg.xml') diff --git a/erts/doc/src/inet_cfg.xml b/erts/doc/src/inet_cfg.xml new file mode 100644 index 0000000000..18cf65759a --- /dev/null +++ b/erts/doc/src/inet_cfg.xml @@ -0,0 +1,397 @@ + + + + +
+ + 20042009 + Ericsson AB. All Rights Reserved. + + + The contents of this file are subject to the Erlang Public License, + Version 1.1, (the "License"); you may not use this file except in + compliance with the License. You should have received a copy of the + Erlang Public License along with this software. If not, it can be + retrieved online at http://www.erlang.org/. + + Software distributed under the License is distributed on an "AS IS" + basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See + the License for the specific language governing rights and limitations + under the License. + + + + Inet configuration + Peter Andersson + + 2004-03-02 + PA1 + inet_cfg.xml +
+ +
+ Introduction +

This chapter tells you how the Erlang runtime system is configured + for IP communication. It also explains how you may configure it + for your own particular needs by means of a configuration file. + The information here is mainly intended for users with special + configuration needs or problems. There should normally be no need + for specific settings for Erlang to function properly on a correctly + IP configured platform.

+

When Erlang starts up it will read the kernel variable + which, if defined, should specify the location and + name of a user configuration file. Example:

+

+

Note that the usage of a file, which was + supported in earlier Erlang versions, is now obsolete.

+

A second way to specify the configuration file is to set the + environment variable to the full name of the file. Example (bash):

+

+

Note that the kernel variable overrides this environment variable.

+

If no user configuration file is specified and Erlang is started + in non-distributed or short name distributed mode, Erlang will use + default configuration settings and a native lookup method that should + work correctly under most circumstances. Erlang + will not read any information from system inet configuration files + (like /etc/host.conf, /etc/nsswitch.conf, etc) in these modes, + except for /etc/resolv.conf and /etc/hosts that is read and monitored + for changes on Unix platforms for the internal DNS client + inet_res.

+

If Erlang is started in long name distributed mode, it needs to + get the domain name from somewhere and will read system inet + configuration files for this information. Any hosts and resolver + information found then is also recorded, but not + used as long as Erlang is configured for native lookups. (The + information becomes useful if the lookup method is changed to + or , see below).

+

Native lookup (system calls) is always the default resolver method. This + is true for all platforms except VxWorks and OSE Delta where + or is used (in that order of priority).

+

On Windows platforms, Erlang will search the system registry rather than + look for configuration files when started in long name distributed mode.

+
+ +
+ Configuration Data +

Erlang records the following data in a local database if found in system + inet configuration files (or system registry):

+ + Host names and addresses + Domain name + Nameservers + Search domains + Lookup method + +

This data may also be specified explicitly in the user + configuration file. The configuration file should contain lines + of configuration parameters (each terminated with a full + stop). Some parameters add data to the configuration (e.g. host + and nameserver), others overwrite any previous settings + (e.g. domain and lookup). The user configuration file is always + examined last in the configuration process, making it possible + for the user to override any default values or previously made + settings. Call to view the state of the + inet configuration database.

+

These are the valid configuration parameters:

+

+ + + +

+

+

+

+

Specify a system file that Erlang should read configuration + data from. tells the parser how the file should be + interpreted: (Unix resolv.conf), + (FreeBSD host.conf), (BSDOS host.conf), + (Linux host.conf), + (Unix nsswitch.conf) or (Unix hosts). should + specify the name of the file with full path.

+

+ + + +

+

+

+

Specify a system file that Erlang should read resolver + configuration from for the internal DNS client + inet_res, + and monitor for changes, even if it does not exist. + The path must be absolute.

+

This may override the configuration parameters + and + depending on the contents + of the specified file. They may also change any time in the future + reflecting the file contents.

+

If the file is specified as an empty string "", + no file is read nor monitored in the future. This emulates + the old behaviour of not configuring the DNS client when + the node is started in short name distributed mode.

+

If this parameter is not specified it defaults to + unless the environment variable + is set which defines + the directory for this file to some maybe other than + .

+

+ + + +

+

+

+

Specify a system file that Erlang should read resolver + configuration from for the internal hosts file resolver + and monitor for changes, even if it does not exist. + The path must be absolute.

+

These host entries are searched after all added with + {file, hosts, File} above or + {host, IP, Aliases} below when the lookup option + file is used.

+

If the file is specified as an empty string "", + no file is read nor monitored in the future. This emulates + the old behaviour of not configuring the DNS client when + the node is started in short name distributed mode.

+

If this parameter is not specified it defaults to + unless the environment variable + is set which defines + the directory for this file to some maybe other than + .

+

+ + + +

+

+

+

Specify a system registry that Erlang should read configuration + data from. Currently, is the only valid option.

+

+ + + +

+

+

+

+

Add host entry to the hosts table.

+

+ + + +

+

+

+

Set domain name.

+

+ + + +

+

+

+

+

Add address (and port, if other than default) of primary + nameserver to use for + inet_res.

+

+ + + +

+

+

+

+

Add address (and port, if other than default) of secondary + nameserver for + inet_res.

+

+ + + +

+

+

+

Add search domains for + inet_res.

+

+ + + +

+

+

+

Specify lookup methods and in which order to try them. + The valid methods are: (use system calls), + (use host data retrieved from + system configuration files and/or + the user configuration file) or + (use the Erlang DNS client + inet_res + for nameserver queries).

+

+ + + +

+

+

+

Set size of resolver cache. Default is 100 DNS records.

+

+ + + +

+

+

+

Set how often (in millisec) + the resolver cache for + inet_res. + is refreshed (i.e. expired DNS records are deleted). + Default is 1 h.

+

+ + + +

+

+

+

Set the time to wait until retry (in millisec) for DNS queries + made by + inet_res. + Default is 2 sec.

+

+ + + +

+

+

+

Set the number of DNS queries + inet_res + will try before giving up. + Default is 3.

+

+ + + +

+

+

+

Tells the DNS client + inet_res + to look up IPv6 addresses. Default is false.

+

+ + + +

+

+

+

Tells the DNS client + inet_res + to use TCP (Virtual Circuit) instead of UDP. Default is false.

+

+ + + +

+

+

+

Sets the EDNS version that + inet_res + will use. The only allowed is zero. Default is false + which means to not use EDNS.

+

+ + + +

+

+

+

Sets the allowed UDP payload size + inet_res + will advertise in EDNS queries. Also sets the limit + when the DNS query will be deemed too large for UDP + forcing a TCP query instead, which is not entirely + correct since the advertised UDP payload size of the + individual nameserver is what should be used, + but this simple strategy will do until a more intelligent + (probing, caching) algorithm need be implemented. + The default is 1280 which stems from the + standard Ethernet MTU size.

+

+ + + +

+

+

+

Tell Erlang to use other primitive UDP module than inet_udp.

+

+ + + +

+

+

+

Tell Erlang to use other primitive TCP module than inet_tcp.

+

+ + + +

+

Clear the hosts table.

+

+ + + +

+

Clear the list of recorded nameservers (primary and secondary).

+

+ + + +

+

Clear the list of search domains.

+

+ + +
+ +
+ User Configuration Example +

Here follows a user configuration example.

+

Assume a user does not want Erlang to use the native lookup method, + but wants Erlang to read all information necessary from start and use + that for resolving names and addresses. In case lookup fails, Erlang + should request the data from a nameserver (using the Erlang + DNS client, set to use EDNS allowing larger responses). + The resolver configuration will be updated when + its configuration file changes, furthermore, DNS records + should never be cached. The user configuration file + (in this example named , stored + in directory ) could then look like this + (Unix):

+ 
+      %% -- ERLANG INET CONFIGURATION FILE --
+      %% read the hosts file
+      {file, hosts, "/etc/hosts"}.
+      %% add a particular host
+      {host, {134,138,177,105}, ["finwe"]}.
+      %% do not monitor the hosts file
+      {hosts_file, ""}.
+      %% read and monitor nameserver config from here
+      {resolv_conf, "/usr/local/etc/resolv.conf"}.
+      %% enable EDNS
+      {edns,0}.
+      %% disable caching
+      {cache_size, 0}.
+      %% specify lookup method
+      {lookup, [file, dns]}.
+

And Erlang could, for example, be started like this:

+

+
+ + -- cgit v1.2.3