1 Starting with version 2.3.10, pppd includes support for `plugins' -
2 pieces of code which can be loaded into pppd at runtime and which can
3 affect its behaviour in various ways. The idea of plugins is to
4 provide a way for people to customize the behaviour of pppd without
5 having to either apply local patches to each version or get their
6 patches accepted into the standard distribution.
8 A plugin is a standard shared library object, typically with a name
9 ending in .so. They are loaded using the standard dlopen() library
10 call, so plugins are only supported on systems which support shared
11 libraries and the dlopen call. At present pppd is compiled with
12 plugin support only under Linux and Solaris.
14 Plugins are loaded into pppd using the `plugin' option, which takes
15 one argument, the name of a shared object file. The plugin option is
16 a privileged option. If the name given does not contain a slash, pppd
17 will look in the /usr/lib/pppd/<version> directory for the file, where
18 <version> is the version number of pppd, for example, 2.4.2. I
19 suggest that you either give the full path name of the shared object
20 file or just the base name; if you don't, it may be possible for
21 unscrupulous users to substitute another shared object file for the
22 one you mean to load, e.g. by setting the LD_LIBRARY_PATH variable.
24 Plugins are usually written in C and compiled and linked to a shared
25 object file in the appropriate manner for your platform. Using gcc
26 under Linux, a plugin called `xyz' could be compiled and linked with
27 the following commands:
30 gcc -shared -o xyz.so xyz.o
32 There are some example plugins in the pppd/plugins directory in the
33 ppp distribution. Currently there is one example, minconn.c, which
34 implements a `minconnect' option, which specifies a minimum connect
35 time before the idle timeout applies.
37 Plugins can access global variables within pppd, so it is useful for
38 them to #include "pppd.h" from the pppd source directory.
40 Every plugin must contain a global procedure called `plugin_init'.
41 This procedure will get called (with no arguments) immediately after
42 the plugin is loaded. Every plugin should also contain a variable
43 called pppd_version declared as follows:
45 char pppd_version[] = VERSION;
47 If this declaration is included, pppd will not load the module if its
48 version number differs from that compiled into the plugin binary.
50 Plugins can affect the behaviour of pppd in at least four ways:
52 1. They can add extra options which pppd will then recognize. This is
53 done by calling the add_options() procedure with a pointer to an
54 array of option_t structures. The last entry in the array must
55 have its name field set to NULL.
57 2. Pppd contains `hook' variables which are procedure pointers. If a
58 given hook is not NULL, pppd will call the procedure it points to
59 at the appropriate point in its processing. The plugin can set any
60 of these hooks to point to its own procedures. See below for a
61 description of the hooks which are currently implemented.
63 3. Plugin code can call any global procedures and access any global
66 4. Plugins can register procedures to be called when particular events
67 occur, using the `notifier' mechanism in pppd. The differences
68 between hooks and notifiers are that a hook will only call one
69 function, whereas a notifier can call an arbitrary number, and that
70 a hook usually returns some value to pppd, whereas a notifier
71 function returns nothing.
73 Here is a list of the currently implemented hooks in pppd.
76 int (*idle_time_hook)(struct ppp_idle *idlep);
78 The idle_time_hook is called when the link first comes up (i.e. when
79 the first network protocol comes up) and at intervals thereafter. On
80 the first call, the idlep parameter is NULL, and the return value is
81 the number of seconds before pppd should check the link activity, or 0
82 if there is to be no idle timeout.
84 On subsequent calls, idlep points to a structure giving the number of
85 seconds since the last packets were sent and received. If the return
86 value is > 0, pppd will wait that many seconds before checking again.
87 If it is <= 0, that indicates that the link should be terminated due
91 int (*holdoff_hook)(void);
93 The holdoff_hook is called when an attempt to bring up the link fails,
94 or the link is terminated, and the persist or demand option was used.
95 It returns the number of seconds that pppd should wait before trying
96 to reestablish the link (0 means immediately).
99 int (*pap_check_hook)(void);
100 int (*pap_passwd_hook)(char *user, char *passwd);
101 int (*pap_auth_hook)(char *user, int userlen,
102 char *passwd, int passlen,
103 char **msgp, int *msglenp,
104 struct wordlist **paddrs,
105 struct wordlist **popts);
106 void (*pap_logout_hook)(void);
108 These hooks are designed to allow a plugin to replace the normal PAP
109 password processing in pppd with something different (e.g. contacting
112 The pap_check_hook is called to check whether there is any possibility
113 that the peer could authenticate itself to us. If it returns 1, pppd
114 will ask the peer to authenticate itself. If it returns 0, pppd will
115 not ask the peer to authenticate itself (but if authentication is
116 required, pppd may exit, or terminate the link before network protocol
117 negotiation). If it returns -1, pppd will look in the pap-secrets
118 file as it would normally.
120 The pap_passwd_hook is called to determine what username and password
121 pppd should use in authenticating itself to the peer with PAP. The
122 user string will already be initialized, by the `user' option, the
123 `name' option, or from the hostname, but can be changed if necessary.
124 MAXNAMELEN bytes of space are available at *user, and MAXSECRETLEN
125 bytes of space at *passwd. If this hook returns 0, pppd will use the
126 values at *user and *passwd; if it returns -1, pppd will look in the
127 pap-secrets file, or use the value from the +ua or password option, as
130 The pap_auth_hook is called to determine whether the username and
131 password supplied by the peer are valid. user and passwd point to
132 null-terminated strings containing the username and password supplied
133 by the peer, with non-printable characters converted to a printable
134 form. The pap_auth_hook function should set msg to a string to be
135 returned to the peer and return 1 if the username/password was valid
136 and 0 if not. If the hook returns -1, pppd will look in the
137 pap-secrets file as usual.
139 If the username/password was valid, the hook can set *paddrs to point
140 to a wordlist containing the IP address(es) which the peer is
141 permitted to use, formatted as in the pap-secrets file. It can also
142 set *popts to a wordlist containing any extra options for this user
143 which pppd should apply at this point.
145 The pap_logout_hook is called when the link is terminated, instead of
146 pppd's internal `plogout' function. It can be used for accounting
147 purposes. This hook is deprecated and will be replaced by a notifier.
150 int (*null_auth_hook)(struct wordlist **paddrs,
151 struct wordlist **popts);
153 This hook allows a plugin to determine what the policy should be if
154 the peer refuses to authenticate when it is requested to. If the
155 return value is 0, the link will be terminated; if it is 1, the
156 connection is allowed to proceed, and in this case *paddrs and *popts
157 can be set as for pap_auth_hook, to specify what IP addresses are
158 permitted and any extra options to be applied. If the return value is
159 -1, pppd will look in the pap-secrets file as usual.
162 void (*ip_choose_hook)(u_int32_t *addrp);
164 This hook is called at the beginning of IPCP negotiation. It gives a
165 plugin the opportunity to set the IP address for the peer; the address
166 should be stored in *addrp. If nothing is stored in *addrp, pppd will
167 determine the peer's address in the usual manner.
170 A plugin registers itself with a notifier by declaring a procedure of
173 void my_notify_proc(void *opaque, int arg);
175 and then registering the procedure with the appropriate notifier with
178 add_notifier(&interesting_notifier, my_notify_proc, opaque);
180 The `opaque' parameter in the add_notifier call will be passed to
181 my_notify_proc every time it is called. The `arg' parameter to
182 my_notify_proc depends on the notifier.
184 A notify procedure can be removed from the list for a notifier with a
187 remove_notifier(&interesting_notifier, my_notify_proc, opaque);
189 Here is a list of the currently-implemented notifiers in pppd.
191 * pidchange. This notifier is called in the parent when pppd has
192 forked and the child is continuing pppd's processing, i.e. when pppd
193 detaches from its controlling terminal. The argument is the pid of
196 * phasechange. This is called when pppd moves from one phase of
197 operation to another. The argument is the new phase number.
199 * exitnotify. This is called just before pppd exits. The argument is
200 the status with which pppd will exit (i.e. the argument to exit()).
202 * sigreceived. This is called when a signal is received, from within
203 the signal handler. The argument is the signal number.
205 * ip_up_notifier. This is called when IPCP has come up.
207 * ip_down_notifier. This is called when IPCP goes down.
209 * auth_up_notifier. This is called when the peer has successfully
210 authenticated itself.
212 * link_down_notifier. This is called when the link goes down.
216 ## $Id: PLUGINS,v 1.3 2001/05/21 08:34:33 paulus Exp $ ##