ProFTPD Developer's Guide: Command Tables

ProFTPD Version 1.2

Command Tables
The cmdtable is a structure which lists all FTP command handlers for the module. Each entry in this table contains a special command type field which determines type of handler, be it PRE_CMD, CMD, POST_CMD, or LOG_CMD (see the command handlers documentation for more details on these types).

Definition

• command type
• command name, or the actual NULL-terminated ASCII text sent by a client, in uppercase, for this command. The include/ftp.h header file has macros which define all known RFC FTP protocol commands. This name can also be the special macro C_ANY, which receives all commands.
• command group, which is the access control group, referenced by <Limit> directives, to which this command belongs. This group can be either G_DIRS for commands related to directory listing, G_READ for commands related to reading files, G_WRITE for commands related to writing files, or the special G_NONE for those commands against which a <Limit READ|WRITE|DIRS> will not be applied.
• function pointer to the handler function for this command. This function must have the prototype MODRET func(cmd_rec *cmd).
• Boolean value: TRUE if the command cannot be used before authentication, via the USER/PASS commands, has occurred, FALSE otherwise.
• Boolean value: TRUE if the command can be sent during a file transfer, FALSE otherwise. Note: as of ProFTPD version 1.1.5, this field is obsolete, and is no longer used.

Example
This command table is in the example mod_sample module:

cmdtable sample_commands[] = {
  { PRE_CMD,  C_ANY,  G_NONE, pre_cmd,        FALSE, FALSE },
  { LOG_CMD,  C_ANY,  G_NONE, log_cmd,        FALSE, FALSE },
  { POST_CMD, C_RETR, G_NONE, post_cmd_retr,  FALSE, FALSE },
  { POST_CMD, C_STOR, G_NONE, post_cmd_stor,  FALSE, FALSE },
  { POST_CMD, C_APPE, G_NONE, post_cmd_stor,  FALSE, FALSE },
  { POST_CMD, C_LIST, G_NONE, post_cmd_list,  FALSE, FALSE },
  { POST_CMD, C_NLST, G_NONE, post_cmd_nlst,  FALSE, FALSE },
  { CMD,      "XFOO", G_DIRS, cmd_xfoo,       TRUE,  FALSE },
  { 0, NULL }
};

The one entry in the example table that defines a CMD demonstrates how to declare a command handler function for a custom FTP command, XFOO in this case. Most FTP clients allow the user to send arbitrary "commands" to the FTP server; this ability combined with custom FTP commands handlers such as this XFOO allow the programmer to create arbitrary, albeit not widely implemented, FTP commands.

The trailing { 0, NULL } field is the terminating field in the table, and should always be used.