plugin_init.3

NAME

plugin_init() - Template for Dynamic SMTP Plugins

SYNTAX

#include smtp_plugin.h

char *from_plug(char *rip, char *from, char **mesg);

char *rcpt_plug(char *rip, char *from, char *rcpt, char **mesg);

char *data_plug(char *local, char *rip, char *rhost, char *rinfo, char **mesg);

PLUGIN *plugin_init();

typedef struct
{
	int             (*mail_func) (char *, char *, char **);
	int             (*rcpt_func) (char *, char *, char *, char **);
	int             (*data_func) (char *, char *, char *, char *, char **);
} PLUGIN;

DESCRIPTION

PLUGIN structure has three components: mail_func is a pointer to function to be executed in the SMTP MAIL session. rcpt_func is a pointer to function to be executed in the SMTP RCPT session. data_func is a pointer to function to be executed in the SMTP DATA session.

To write a SMTP plugin you have to write the plugin_init() function. Depending on which phase of SMTP (MAIL, RCPT, DATA) you want to call your function, you have to write the from_plug, rcpt_plug, data_plug functions. If you plan to write multiple plugins, define the functions as static. e.g.

 static char *from_plug(char *rip, char *from, char **mesg);

The plugin_init() function can be written as below

PLUGIN         *
plugin_init()
{
	static PLUGIN   plug;
	PLUGIN         *ptr;

	ptr = &plug;
	ptr->mail_func = from_plug;
	ptr->rcpt_func = rcpt_plug;
	ptr->data_func = data_plug;
	return &plug;
}

To compile the plugin you can use gcc(1).

gcc -Wall -O2 -fPIC -fno-strict-aliasing -c smtp_plugin.c
gcc -shared -rdynamic -nostartfiles -fPIC -s -O4 -o smtpd-plugin.so smtp_plugin.o

You need to copy the plugin in /usr/usr/lib/indimail/plugins directory for it to get loaded by qmail-smtpd(8) at runtime.

If you desire to write multiple plugins, you should have your plugins as smtpd-plugin.so, smtpd-plugin0.so, smtpd-plugin1.so and so on. To ensure functions to be executed from all libraries, you should append an index to the mail_func, rcpt_func and data_func functions. eg. Your plugin_init() in smtpd-plugin0.so can be

PLUGIN         *
plugin_init()
{
	static PLUGIN   plug;
	PLUGIN         *ptr;

	ptr = &plug;
	ptr->mail_func = from_plug_0;
	ptr->rcpt_func = rcpt_plug_0;
	ptr->data_func = data_plug_0;
	return &plug;
}

You can test these plugins using the plugest(1) command.

RETURN VALUE

The functions from_plug, rcpt_plug, data_plug must return 0 on success. These functions should return 1 to terminate the sesson with a message. You can set your own message by assigning mesg variable. If you have the below function in smtpd-plugin.so

int
rcpt_plug(char *remoteip, char *from, char *rcpt, char **mesg)
{
	if (!strstr(rcpt, "@yahoo.com"))
	{
		*mesg = "530 We are serious and don't Yahoo (#5.7.1);
		return (1);
	}
	return (0);
}

SEE ALSO

qmail-smtpd(8), dlopen(3) plugtest(1), gcc(1)