affect its behaviour in various ways. The idea of plugins is to
provide a way for people to customize the behaviour of pppd without
having to either apply local patches to each version or get their
-patches accepted into the standard distribution. My aim is that
-plugins will be able to be used with successive versions of pppd
-without needing to recompile the plugins.
+patches accepted into the standard distribution.
A plugin is a standard shared library object, typically with a name
ending in .so. They are loaded using the standard dlopen() library
Plugins are loaded into pppd using the `plugin' option, which takes
one argument, the name of a shared object file. The plugin option is
-a privileged option. I suggest that you give the full path name of
-the shared object file; if you don't, it may be possible for
+a privileged option. If the name given does not contain a slash, pppd
+will look in the /usr/lib/pppd/<version> directory for the file, where
+<version> is the version number of pppd, for example, 2.4.2. I
+suggest that you either give the full path name of the shared object
+file or just the base name; if you don't, it may be possible for
unscrupulous users to substitute another shared object file for the
one you mean to load, e.g. by setting the LD_LIBRARY_PATH variable.
Every plugin must contain a global procedure called `plugin_init'.
This procedure will get called (with no arguments) immediately after
-the plugin is loaded.
+the plugin is loaded. Every plugin should also contain a variable
+called pppd_version declared as follows:
-Plugins can affect the behaviour of pppd in at least three ways:
+char pppd_version[] = VERSION;
+
+If this declaration is included, pppd will not load the module if its
+version number differs from that compiled into the plugin binary.
+
+Plugins can affect the behaviour of pppd in at least four ways:
1. They can add extra options which pppd will then recognize. This is
done by calling the add_options() procedure with a pointer to an
3. Plugin code can call any global procedures and access any global
variables in pppd.
+4. Plugins can register procedures to be called when particular events
+ occur, using the `notifier' mechanism in pppd. The differences
+ between hooks and notifiers are that a hook will only call one
+ function, whereas a notifier can call an arbitrary number, and that
+ a hook usually returns some value to pppd, whereas a notifier
+ function returns nothing.
+
Here is a list of the currently implemented hooks in pppd.
int (*pap_check_hook)(void);
int (*pap_passwd_hook)(char *user, char *passwd);
-int (*pap_auth_hook)(char *user, int userlen,
- char *passwd, int passlen,
- char **msgp, int *msglenp,
+int (*pap_auth_hook)(char *user, char *passwd, char **msgp,
struct wordlist **paddrs,
struct wordlist **popts);
+void (*pap_logout_hook)(void);
These hooks are designed to allow a plugin to replace the normal PAP
password processing in pppd with something different (e.g. contacting
set *popts to a wordlist containing any extra options for this user
which pppd should apply at this point.
+The pap_logout_hook is called when the link is terminated, instead of
+pppd's internal `plogout' function. It can be used for accounting
+purposes. This hook is deprecated and will be replaced by a notifier.
+
+
+int (*chap_check_hook)(void);
+int (*chap_passwd_hook)(char *user, char *passwd);
+int (*chap_verify_hook)(char *name, char *ourname, int id,
+ struct chap_digest_type *digest,
+ unsigned char *challenge, unsigned char *response,
+ char *message, int message_space)
+
+These hooks are designed to allow a plugin to replace the normal CHAP
+password processing in pppd with something different (e.g. contacting
+an external server).
+
+The chap_check_hook is called to check whether there is any possibility
+that the peer could authenticate itself to us. If it returns 1, pppd
+will ask the peer to authenticate itself. If it returns 0, pppd will
+not ask the peer to authenticate itself (but if authentication is
+required, pppd may exit, or terminate the link before network protocol
+negotiation). If it returns -1, pppd will look in the chap-secrets
+file as it would normally.
+
+The chap_passwd_hook is called to determine what password
+pppd should use in authenticating itself to the peer with CHAP. The
+user string will already be initialized, by the `user' option, the
+`name' option, or from the hostname, but can be changed if necessary.
+This hook is called only if pppd is a client, not if it is a server.
+
+MAXSECRETLEN bytes of space are available at *passwd. If this hook
+returns 0, pppd will use the value *passwd; if it returns -1, pppd
+will fail to authenticate.
+
+The chap_verify_hook is called to determine whether the peer's
+response to our CHAP challenge is valid -- it should return 1 if valid
+or 0 if not. The parameters are:
+
+* name points to a null-terminated string containing the username
+ supplied by the peer, or the remote name specified with the
+ "remotename" option.
+* ourname points to a null-terminated string containing the name of
+ the local machine (the hostname, or the name specified with the
+ "name" option).
+* id is the value of the id field from the challenge.
+* digest points to a chap_digest_type struct, which contains an
+ identifier for the type of digest in use plus function pointers for
+ functions for dealing with digests of that type.
+* challenge points to the challenge as a counted string (length byte
+ followed by the actual challenge bytes).
+* response points to the response as a counted string.
+* message points to an area of message_space bytes in which to store
+ any message that should be returned to the peer.
+
+
+int (*null_auth_hook)(struct wordlist **paddrs,
+ struct wordlist **popts);
+
+This hook allows a plugin to determine what the policy should be if
+the peer refuses to authenticate when it is requested to. If the
+return value is 0, the link will be terminated; if it is 1, the
+connection is allowed to proceed, and in this case *paddrs and *popts
+can be set as for pap_auth_hook, to specify what IP addresses are
+permitted and any extra options to be applied. If the return value is
+-1, pppd will look in the pap-secrets file as usual.
+
+
+void (*ip_choose_hook)(u_int32_t *addrp);
+
+This hook is called at the beginning of IPCP negotiation. It gives a
+plugin the opportunity to set the IP address for the peer; the address
+should be stored in *addrp. If nothing is stored in *addrp, pppd will
+determine the peer's address in the usual manner.
+
+
+int (*allowed_address_hook)(u_int32_t addr)
+
+This hook is called to see if a peer is allowed to use the specified
+address. If the hook returns 1, the address is accepted. If it returns
+0, the address is rejected. If it returns -1, the address is verified
+in the normal away against the appropriate options and secrets files.
+
+
+void (*snoop_recv_hook)(unsigned char *p, int len)
+void (*snoop_send_hook)(unsigned char *p, int len)
+
+These hooks are called whenever pppd receives or sends a packet. The
+packet is in p; its length is len. This allows plugins to "snoop in"
+on the pppd conversation. The hooks may prove useful in implmenting
+L2TP.
+
+
+void (*multilink_join_hook)();
+
+This is called whenever a new link completes LCP negotiation and joins
+the bundle, if we are doing multilink.
+
+
+A plugin registers itself with a notifier by declaring a procedure of
+the form:
+
+void my_notify_proc(void *opaque, int arg);
+
+and then registering the procedure with the appropriate notifier with
+a call of the form
+
+ add_notifier(&interesting_notifier, my_notify_proc, opaque);
+
+The `opaque' parameter in the add_notifier call will be passed to
+my_notify_proc every time it is called. The `arg' parameter to
+my_notify_proc depends on the notifier.
+
+A notify procedure can be removed from the list for a notifier with a
+call of the form
+
+ remove_notifier(&interesting_notifier, my_notify_proc, opaque);
+
+Here is a list of the currently-implemented notifiers in pppd.
+
+* pidchange. This notifier is called in the parent when pppd has
+ forked and the child is continuing pppd's processing, i.e. when pppd
+ detaches from its controlling terminal. The argument is the pid of
+ the child.
+
+* phasechange. This is called when pppd moves from one phase of
+ operation to another. The argument is the new phase number.
+
+* exitnotify. This is called just before pppd exits. The argument is
+ the status with which pppd will exit (i.e. the argument to exit()).
+
+* sigreceived. This is called when a signal is received, from within
+ the signal handler. The argument is the signal number.
+
+* ip_up_notifier. This is called when IPCP has come up.
+
+* ip_down_notifier. This is called when IPCP goes down.
+
+* auth_up_notifier. This is called when the peer has successfully
+ authenticated itself.
+
+* link_down_notifier. This is called when the link goes down.
+
+
-## $Id: PLUGINS,v 1.2 1999/09/17 06:02:45 paulus Exp $ ##
+## $Id: PLUGINS,v 1.8 2008/06/15 07:02:18 paulus Exp $ ##
projects / ppp.git / blobdiff