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+<?xml version="1.0" encoding="utf-8" ?>
+<!DOCTYPE erlref SYSTEM "erlref.dtd">
+
+<erlref>
+ <header>
+ <copyright>
+ <year>2006</year><year>2018</year>
+ <holder>Ericsson AB. All Rights Reserved.</holder>
+ </copyright>
+ <legalnotice>
+ Licensed under the Apache License, Version 2.0 (the "License");
+ you may not use this file except in compliance with the License.
+ You may obtain a copy of the License at
+
+ http://www.apache.org/licenses/LICENSE-2.0
+
+ Unless required by applicable law or agreed to in writing, software
+ distributed under the License is distributed on an "AS IS" BASIS,
+ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ See the License for the specific language governing permissions and
+ limitations under the License.
+
+ </legalnotice>
+
+ <title>tftp</title>
+ <prepared></prepared>
+ <docno></docno>
+ <date></date>
+ <rev></rev>
+ </header>
+ <module>tftp</module>
+ <modulesummary>Trivial FTP.</modulesummary>
+ <description>
+ <p>Interface module for the <c>tftp</c> application.</p>
+ </description>
+
+ <section>
+ <marker id="options"></marker>
+ <title>DATA TYPES</title>
+ <p><c>ServiceConfig = Options</c></p>
+ <p><c>Options = [option()]</c></p>
+ <p>Most of the options are common for both the client and the server
+ side, but some of them differs a little.
+ The available <c>option()</c>s are as follows:</p>
+ <taglist>
+ <tag><c>{debug, Level}</c></tag>
+ <item>
+ <p><c>Level = none | error | warning | brief | normal | verbose | all</c></p>
+ <p>Controls the level of debug printouts.
+ Default is <c>none</c>.</p>
+ </item>
+ <tag><c>{host, Host}</c></tag>
+ <item>
+ <p><c>Host = hostname()</c>, see
+ <seealso marker="kernel:inet">inet(3)</seealso>.</p>
+ <p>The name or IP address of the host where the TFTP daemon
+ resides. This option is only used by the client.</p>
+ </item>
+ <tag><c>{port, Port}</c></tag>
+ <item>
+ <p><c>Port = int()</c></p>
+ <p>The TFTP port where the daemon listens. Defaults is
+ the standardized number 69. On the server side, it can
+ sometimes make sense to set it to 0, meaning that
+ the daemon just picks a free port (which one is
+ returned by function <c>info/1</c>).</p>
+ <p>If a socket is connected already, option
+ <c>{udp, [{fd, integer()}]}</c> can be used to pass the
+ open file descriptor to <c>gen_udp</c>. This can be automated
+ by using a command-line argument stating the
+ prebound file descriptor number. For example, if the
+ port is 69 and file descriptor 22 is opened by
+ <c>setuid_socket_wrap</c>, the command-line argument
+ "-tftpd_69 22" triggers the prebound file
+ descriptor 22 to be used instead of opening port 69.
+ The UDP option <c>{udp, [{fd, 22}]}</c> is automatically added.
+ See <c>init:get_argument/</c> about command-line arguments and
+ <c>gen_udp:open/2</c> about UDP options.</p>
+ </item>
+ <tag><c>{port_policy, Policy}</c></tag>
+ <item>
+ <p><c>Policy = random | Port | {range, MinPort, MaxPort}</c></p>
+ <p><c>Port = MinPort = MaxPort = int()</c></p>
+ <p>Policy for the selection of the temporary port that is used
+ by the server/client during the file transfer. Default is
+ <c>random</c>, which is the standardized policy. With this
+ policy a randomized free port is used. A single port or a range
+ of ports can be useful if the protocol passes through a
+ firewall.</p>
+ </item>
+ <tag><c>{udp, Options}</c></tag>
+ <item>
+ <p><c>Options = [Opt]</c>, see
+ <seealso marker="kernel:gen_udp#open/1">gen_udp:open/2</seealso>.</p>
+ </item>
+ <tag><c>{use_tsize, Bool}</c></tag>
+ <item>
+ <p><c>Bool = bool()</c></p>
+ <p>Flag for automated use of option <c>tsize</c>. With
+ this set to <c>true</c>, the <c>write_file/3</c> client
+ determines the filesize and sends it to the server as
+ the standardized <c>tsize</c> option. A <c>read_file/3</c>
+ client acquires only a filesize from the server by sending
+ a zero <c>tsize</c>.</p>
+ </item>
+ <tag><c>{max_tsize, MaxTsize}</c></tag>
+ <item>
+ <p><c>MaxTsize = int() | infinity</c></p>
+ <p>Threshold for the maximal filesize in bytes. The transfer
+ is aborted if the limit is exceeded.
+ Default is <c>infinity</c>.</p>
+ </item>
+ <tag><c>{max_conn, MaxConn}</c></tag>
+ <item>
+ <p><c>MaxConn = int() | infinity</c></p>
+ <p>Threshold for the maximal number of active connections.
+ The daemon rejects the setup of new connections if
+ the limit is exceeded. Default is <c>infinity</c>.</p>
+ </item>
+ <tag><c>{TftpKey, TftpVal}</c></tag>
+ <item>
+ <p><c>TftpKey = string()</c> <br></br>
+<c>TftpVal = string()</c></p>
+ <p>Name and value of a TFTP option.</p>
+ </item>
+ <tag><c>{reject, Feature}</c></tag>
+ <item>
+ <p><c>Feature = Mode | TftpKey</c> <br></br>
+<c>&nbsp;Mode = read | write</c> <br></br>
+<c>&nbsp;TftpKey = string()</c></p>
+ <p>Controls which features to reject. This is
+ mostly useful for the server as it can restrict the use
+ of certain TFTP options or read/write access.</p>
+ </item>
+ <tag><c>{callback, {RegExp, Module, State}}</c></tag>
+ <item>
+ <p><c>RegExp = string()</c> <br></br>
+<c>Module = atom()</c> <br></br>
+<c>State = term()</c></p>
+ <p>Registration of a callback module. When a file is to be
+ transferred, its local filename is matched to the regular
+ expressions of the registered callbacks. The first matching
+ callback is used during the transfer. See
+ <seealso marker="#read_file/3">read_file/3</seealso> and
+ <seealso marker="#write_file/3">write_file/3</seealso>.
+ </p>
+ <p>The callback module must implement the <c>tftp</c> behavior, see
+ <seealso marker="#tftp_callback">CALLBACK FUNCTIONS</seealso>.</p>
+ </item>
+
+ <tag><c>{logger, Module}</c></tag>
+ <item>
+ <p><c>Module = module()()</c></p>
+
+ <p>Callback module for customized logging of errors, warnings, and
+ info messages. The callback module must implement the
+ <c>tftp_logger</c> behavior, see
+ <seealso marker="#tftp_logger">LOGGER FUNCTIONS</seealso>.
+ The default module is <c>tftp_logger</c>.</p>
+ </item>
+
+ <tag><c>{max_retries, MaxRetries}</c></tag>
+ <item>
+ <p><c>MaxRetries = int()</c></p>
+
+ <p>Threshold for the maximal number of retries. By default
+ the server/client tries to resend a message up to
+ five times when the time-out expires.</p>
+ </item>
+ </taglist>
+ </section>
+
+ <funcs>
+ <func>
+ <name>change_config(daemons, Options) -> [{Pid, Result}]</name>
+ <fsummary>Changes configuration for all daemons.
+ </fsummary>
+ <type>
+ <v>Options = [option()]</v>
+ <v>Pid = pid()</v>
+ <v>Result = ok | {error, Reason}</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Changes configuration for all TFTP daemon processes. </p>
+ </desc>
+ </func>
+
+ <func>
+ <name>change_config(servers, Options) -> [{Pid, Result}]</name>
+ <fsummary>Changes configuration for all servers.
+ </fsummary>
+ <type>
+ <v>Options = [option()]</v>
+ <v>Pid = pid()</v>
+ <v>Result = ok | {error, Reason}</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Changes configuration for all TFTP server processes.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>change_config(Pid, Options) -> Result</name>
+ <fsummary>Changes configuration for a TFTP daemon, server,
+ or client process.</fsummary>
+ <type>
+ <v>Pid = pid()</v>
+ <v>Options = [option()]</v>
+ <v>Result = ok | {error, Reason}</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Changes configuration for a TFTP daemon, server, or client process.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>info(daemons) -> [{Pid, Options}]</name>
+ <fsummary>Returns information about all daemons.</fsummary>
+ <type>
+ <v>Pid = [pid()()]</v>
+ <v>Options = [option()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Returns information about all TFTP daemon processes.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>info(servers) -> [{Pid, Options}]</name>
+ <fsummary>Returns information about all servers.</fsummary>
+ <type>
+ <v>Pid = [pid()()]</v>
+ <v>Options = [option()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Returns information about all TFTP server processes. </p>
+ </desc>
+ </func>
+
+ <func>
+ <name>info(Pid) -> {ok, Options} | {error, Reason}</name>
+ <fsummary>Returns information about a daemon, server, or client process.</fsummary>
+ <type>
+ <v>Options = [option()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Returns information about a TFTP daemon, server, or client process.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>read_file(RemoteFilename, LocalFilename, Options) -> {ok, LastCallbackState} | {error, Reason}</name>
+ <fsummary>Reads a (virtual) file from a TFTP server.</fsummary>
+ <type>
+ <v>RemoteFilename = string()</v>
+ <v>LocalFilename = binary | string()</v>
+ <v>Options = [option()]</v>
+ <v>LastCallbackState = term()</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Reads a (virtual) file <c>RemoteFilename</c> from a TFTP
+ server.</p>
+ <p>If <c>LocalFilename</c> is the atom <c>binary</c>,
+ <c>tftp_binary</c> is used as callback module. It concatenates
+ all transferred blocks and returns them as one single binary
+ in <c>LastCallbackState</c>.</p>
+ <p>If <c>LocalFilename</c> is a string and there are no
+ registered callback modules, <c>tftp_file</c> is used as
+ callback module. It writes each transferred block to the file
+ named <c>LocalFilename</c> and returns the number of
+ transferred bytes in <c>LastCallbackState</c>.</p>
+ <p>If <c>LocalFilename</c> is a string and there are registered
+ callback modules, <c>LocalFilename</c> is tested against
+ the regexps of these and the callback module corresponding to
+ the first match is used, or an error tuple is returned if no
+ matching regexp is found.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>start(Options) -> {ok, Pid} | {error, Reason}</name>
+ <fsummary>Starts a daemon process.</fsummary>
+ <type>
+ <v>Options = [option()]</v>
+ <v>Pid = pid()</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Starts a daemon process listening for UDP packets on a
+ port. When it receives a request for read or write, it spawns
+ a temporary server process handling the actual transfer
+ of the (virtual) file.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>write_file(RemoteFilename, LocalFilename, Options) -> {ok, LastCallbackState} | {error, Reason}</name>
+ <fsummary>Writes a (virtual) file to a TFTP server.</fsummary>
+ <type>
+ <v>RemoteFilename = string()</v>
+ <v>LocalFilename = binary() | string()</v>
+ <v>Options = [option()]</v>
+ <v>LastCallbackState = term()</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Writes a (virtual) file <c>RemoteFilename</c> to a TFTP
+ server.</p>
+ <p>If <c>LocalFilename</c> is a binary, <c>tftp_binary</c> is
+ used as callback module. The binary is transferred block by
+ block and the number of transferred bytes is returned in
+ <c>LastCallbackState</c>.</p>
+ <p>If <c>LocalFilename</c> is a string and there are no
+ registered callback modules, <c>tftp_file</c> is used as
+ callback module. It reads the file named <c>LocalFilename</c>
+ block by block and returns the number of transferred bytes
+ in <c>LastCallbackState</c>.</p>
+ <p>If <c>LocalFilename</c> is a string and there are registered
+ callback modules, <c>LocalFilename</c> is tested against
+ the regexps of these and the callback module corresponding to
+ the first match is used, or an error tuple is returned if no
+ matching regexp is found.</p>
+ </desc>
+ </func>
+ </funcs>
+
+ <section>
+ <marker id="tftp_callback"></marker>
+ <title>CALLBACK FUNCTIONS</title>
+ <p>A <c>tftp</c> callback module is to be implemented as a
+ <c>tftp</c> behavior and export the functions listed
+ in the following.</p>
+ <p>On the server side, the callback interaction starts with a call to
+ <c>open/5</c> with the registered initial callback state.
+ <c>open/5</c> is expected to open the (virtual) file. Then either
+ function <c>read/1</c> or <c>write/2</c> is invoked
+ repeatedly, once per transferred block. At each function call,
+ the state returned from the previous call is obtained. When
+ the last block is encountered, function <c>read/1</c> or
+ <c>write/2</c> is expected to close the (virtual) file
+ and return its last state. Function <c>abort/3</c> is only
+ used in error situations. Function <c>prepare/5</c> is not used on
+ the server side.</p>
+ <p>On the client side, the callback interaction is the same, but it
+ starts and ends a bit differently. It starts with a call to
+ <c>prepare/5</c> with the same arguments as <c>open/5</c> takes.
+ <c>prepare/5</c> is expected to validate the TFTP options
+ suggested by the user and to return the subset of them that it
+ accepts. Then the options are sent to the server, which performs
+ the same TFTP option negotiation procedure. The options that are
+ accepted by the server are forwarded to function <c>open/5</c>
+ on the client side. On the client side, function <c>open/5</c>
+ must accept all option as-is or reject the transfer. Then
+ the callback interaction follows the same pattern as described
+ for the server side. When the last block is encountered in
+ <c>read/1</c> or <c>write/2</c>, the returned state is forwarded to
+ the user and returned from <c>read_file</c>/3 or
+ <c>write_file/3</c>.</p>
+
+ <p> If a callback (performing the file access
+ in the TFTP server) takes too long time (more than
+ the double TFTP time-out), the server aborts the
+ connection and sends an error reply to the client.
+ This implies that the server releases resources
+ attached to the connection faster than before. The
+ server simply assumes that the client has given
+ up.</p>
+
+ <p>If the TFTP server receives yet another request from
+ the same client (same host and port) while it
+ already has an active connection to the client, it
+ ignores the new request if the request is
+ equal to the first one (same filename and options).
+ This implies that the (new) client will be served
+ by the already ongoing connection on the server
+ side. By not setting up yet another connection, in
+ parallel with the ongoing one, the server
+ consumes less resources.</p>
+
+ <marker id="prepare"></marker>
+ </section>
+
+ <funcs>
+ <func>
+ <name>Module:abort(Code, Text, State) -> ok</name>
+ <fsummary>Aborts the file transfer.</fsummary>
+ <type>
+ <v>Code = undef | enoent | eacces | enospc</v>
+ <v>&nbsp;&nbsp;| badop | eexist | baduser | badopt</v>
+ <v>&nbsp;&nbsp;| int()</v>
+ <v>Text = string()</v>
+ <v>State = term()</v>
+ </type>
+ <desc>
+ <p>Invoked when the file transfer is aborted.</p>
+ <p>The callback function is expected to clean
+ up its used resources after the aborted file
+ transfer, such as closing open file
+ descriptors and so on. The function is not
+ invoked if any of the other callback
+ functions returns an error, as it is
+ expected that they already have cleaned up
+ the necessary resources. However, it is
+ invoked if the functions fail (crash).</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>Module:open(Peer, Access, Filename, Mode, SuggestedOptions, State) -> {ok, AcceptedOptions, NewState} | {error, {Code, Text}}</name>
+ <fsummary>Opens a file for read or write access.</fsummary>
+ <type>
+ <v>Peer = {PeerType, PeerHost, PeerPort}</v>
+ <v>PeerType = inet | inet6</v>
+ <v>PeerHost = ip_address()</v>
+ <v>PeerPort = integer()</v>
+ <v>Access = read | write</v>
+ <v>Filename = string()</v>
+ <v>Mode = string()</v>
+ <v>SuggestedOptions = AcceptedOptions = [{Key, Value}]</v>
+ <v>&nbsp;Key = Value = string()</v>
+ <v>State = InitialState | term()</v>
+ <v>&nbsp;InitialState = [] | [{root_dir, string()}]</v>
+ <v>NewState = term()</v>
+ <v>Code = undef | enoent | eacces | enospc</v>
+ <v>&nbsp;&nbsp;| badop | eexist | baduser | badopt</v>
+ <v>&nbsp;&nbsp;| int()</v>
+ <v>Text = string()</v>
+ </type>
+ <desc>
+ <p>Opens a file for read or write access.</p>
+ <p>On the client side, where the <c>open/5</c> call has been
+ preceded by a call to <c>prepare/5</c>, all options must be
+ accepted or rejected.</p>
+ <p>On the server side, where there is no preceding
+ <c>prepare/5</c> call, no new options can be added, but
+ those present in <c>SuggestedOptions</c> can be
+ omitted or replaced with new values in <c>AcceptedOptions</c>.</p>
+
+ <marker id="read"></marker>
+ </desc>
+ </func>
+
+ <func>
+ <name>Module:prepare(Peer, Access, Filename, Mode, SuggestedOptions, InitialState) -> {ok, AcceptedOptions, NewState} | {error, {Code, Text}}</name>
+ <fsummary>Prepares to open a file on the client side.</fsummary>
+ <type>
+ <v>Peer = {PeerType, PeerHost, PeerPort}</v>
+ <v>PeerType = inet | inet6</v>
+ <v>PeerHost = ip_address()</v>
+ <v>PeerPort = integer()</v>
+ <v>Access = read | write</v>
+ <v>Filename = string()</v>
+ <v>Mode = string()</v>
+ <v>SuggestedOptions = AcceptedOptions = [{Key, Value}]</v>
+ <v>&nbsp;Key = Value = string()</v>
+ <v>InitialState = [] | [{root_dir, string()}]</v>
+ <v>NewState = term()</v>
+ <v>Code = undef | enoent | eacces | enospc</v>
+ <v>&nbsp;&nbsp;| badop | eexist | baduser | badopt</v>
+ <v>&nbsp;&nbsp;| int()</v>
+ <v>Text = string()</v>
+ </type>
+ <desc>
+ <p>Prepares to open a file on the client side.</p>
+ <p>No new options can be added, but those present in
+ <c>SuggestedOptions</c> can be omitted or replaced with new
+ values in <c>AcceptedOptions</c>.</p>
+ <p>This is followed by a call to <c>open/4</c> before any
+ read/write access is performed. <c>AcceptedOptions</c> is
+ sent to the server, which replies with the options that it
+ accepts. These are then forwarded to <c>open/4</c> as
+ <c>SuggestedOptions</c>.</p>
+
+ <marker id="open"></marker>
+ </desc>
+ </func>
+
+ <func>
+ <name>Module:read(State) -> {more, Bin, NewState} | {last, Bin, FileSize} | {error, {Code, Text}}</name>
+ <fsummary>Reads a chunk from the file.</fsummary>
+ <type>
+ <v>State = NewState = term()</v>
+ <v>Bin = binary()</v>
+ <v>FileSize = int()</v>
+ <v>Code = undef | enoent | eacces | enospc</v>
+ <v>&nbsp;&nbsp;| badop | eexist | baduser | badopt</v>
+ <v>&nbsp;&nbsp;| int()</v>
+ <v>Text = string()</v>
+ </type>
+ <desc>
+ <p>Reads a chunk from the file.</p>
+ <p>The callback function is expected to close
+ the file when the last file chunk is
+ encountered. When an error is encountered,
+ the callback function is expected to clean
+ up after the aborted file transfer, such as
+ closing open file descriptors, and so on. In both
+ cases there will be no more calls to any of
+ the callback functions.</p>
+
+ <marker id="write"></marker>
+ </desc>
+ </func>
+
+ <func>
+ <name>Module:write(Bin, State) -> {more, NewState} | {last, FileSize} | {error, {Code, Text}}</name>
+ <fsummary>Writes a chunk to the file.</fsummary>
+ <type>
+ <v>Bin = binary()</v>
+ <v>State = NewState = term()</v>
+ <v>FileSize = int()</v>
+ <v>Code = undef | enoent | eacces | enospc</v>
+ <v>&nbsp;&nbsp;| badop | eexist | baduser | badopt</v>
+ <v>&nbsp;&nbsp;| int()</v>
+ <v>Text = string()</v>
+ </type>
+ <desc>
+ <p>Writes a chunk to the file.</p>
+ <p>The callback function is expected to close
+ the file when the last file chunk is
+ encountered. When an error is encountered,
+ the callback function is expected to clean
+ up after the aborted file transfer, such as
+ closing open file descriptors, and so on. In both
+ cases there will be no more calls to any of
+ the callback functions.</p>
+
+ <marker id="abort"></marker>
+ </desc>
+ </func>
+ </funcs>
+
+ <section>
+ <marker id="tftp_logger"></marker>
+ <title>LOGGER FUNCTIONS</title>
+
+ <p>A <c>tftp_logger</c> callback module is to be implemented as a
+ <c>tftp_logger</c> behavior and export the following functions:</p>
+
+ <marker id="error_msg"></marker>
+ </section>
+
+ <funcs>
+ <func>
+ <name>Logger:error_msg(Format, Data) -> ok | exit(Reason)</name>
+ <fsummary>Logs an error message.</fsummary>
+ <type>
+ <v>Format = string()</v>
+ <v>Data = [term()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Logs an error message.
+ See <c>error_logger:error_msg/2</c> for details.</p>
+
+ <marker id="warning_msg"></marker>
+ </desc>
+ </func>
+
+ <func>
+ <name>Logger:info_msg(Format, Data) -> ok | exit(Reason)</name>
+ <fsummary>Logs an info message.</fsummary>
+ <type>
+ <v>Format = string()</v>
+ <v>Data = [term()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Logs an info message.
+ See <c>error_logger:info_msg/2</c> for details.</p>
+ </desc>
+ </func>
+
+ <func>
+ <name>Logger:warning_msg(Format, Data) -> ok | exit(Reason)</name>
+ <fsummary>Logs a warning message.</fsummary>
+ <type>
+ <v>Format = string()</v>
+ <v>Data = [term()]</v>
+ <v>Reason = term()</v>
+ </type>
+ <desc>
+ <p>Logs a warning message.
+ See <c>error_logger:warning_msg/2</c> for details.</p>
+
+ <marker id="info_msg"></marker>
+ </desc>
+ </func>
+ </funcs>
+</erlref>
+
+