add API for plug-ins to write to openvpn log

Some plugins want to add messages to the openvpn log file. The
plugin_log() and plugin_vlog() APIs provide ways for them to do so.

OPENVPN_PLUGINv3_STRUCTVER is not incremented as the v3 plugin API
is new in 2.3 and this is merged during alpha phase.

Signed-off-by: Heiko Hund <heiko.hund@sophos.com>
Acked-by: David Sommerseth <davids@redhat.com>
Message-Id: 1343920822-29161-1-git-send-email-heiko.hund@sophos.com
URL: http://article.gmane.org/gmane.network.openvpn.devel/6946
Signed-off-by: David Sommerseth <dazo@users.sourceforge.net>

2 files changed, 121 insertions, 2 deletions

diff --git a/include/openvpn-plugin.h b/include/openvpn-plugin.h
index 1c80eec..0879f49 100644
--- a/include/openvpn-plugin.h
+++ b/include/openvpn-plugin.h
@@ -43,6 +43,8 @@ typedef X509 openvpn_x509_cert_t;
 #endif
 #endif
 
+#include <stdarg.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -145,7 +147,7 @@ typedef void *openvpn_plugin_handle_t;
 /*
  * For Windows (needs to be modified for MSVC)
  */
-#if defined(__MINGW32_VERSION) && !defined(OPENVPN_PLUGIN_H)
+#if defined(WIN32) && !defined(OPENVPN_PLUGIN_H)
 # define OPENVPN_EXPORT __declspec(dllexport)
 #else
 # define OPENVPN_EXPORT
@@ -205,6 +207,59 @@ struct openvpn_plugin_string_list
 #define OPENVPN_PLUGINv3_STRUCTVER 1
 
 /**
+ * Definitions needed for the plug-in callback functions.
+ */
+typedef enum
+{
+  PLOG_ERR    = (1 << 0),  /* Error condition message */
+  PLOG_WARN   = (1 << 1),  /* General warning message */
+  PLOG_NOTE   = (1 << 2),  /* Informational message */
+  PLOG_DEBUG  = (1 << 3),  /* Debug message, displayed if verb >= 7 */
+
+  PLOG_ERRNO  = (1 << 8),  /* Add error description to message */
+  PLOG_NOMUTE = (1 << 9),  /* Mute setting does not apply for message */
+
+} openvpn_plugin_log_flags_t;
+
+
+#ifdef __GNUC__
+#if __USE_MINGW_ANSI_STDIO
+#  define _ovpn_chk_fmt(a, b) __attribute__ ((format(gnu_printf, (a), (b))))
+#else
+#  define _ovpn_chk_fmt(a, b) __attribute__ ((format(__printf__, (a), (b))))
+#endif
+#else
+#  define _ovpn_chk_fmt(a, b)
+#endif
+
+typedef void (*plugin_log_t) (openvpn_plugin_log_flags_t flags,
+                              const char *plugin_name,
+                              const char *format, ...) _ovpn_chk_fmt(3, 4);
+
+typedef void (*plugin_vlog_t) (openvpn_plugin_log_flags_t flags,
+                               const char *plugin_name,
+                               const char *format,
+                               va_list arglist) _ovpn_chk_fmt(3, 0);
+
+#undef _ovpn_chk_fmt
+
+/**
+ * Used by the openvpn_plugin_open_v3() function to pass callback
+ * function pointers to the plug-in.
+ *
+ * plugin_log
+ * plugin_vlog : Use these functions to add information to the OpenVPN log file.
+ *               Messages will only be displayed if the plugin_name parameter
+ *               is set. PLOG_DEBUG messages will only be displayed with plug-in
+ *               debug log verbosity (at the time of writing that's verb >= 7).
+ */
+struct openvpn_plugin_callbacks
+{
+  plugin_log_t    plugin_log;
+  plugin_vlog_t   plugin_vlog;
+};
+
+/**
  * Arguments used to transport variables to the plug-in.
  * The struct openvpn_plugin_args_open_in is only used
  * by the openvpn_plugin_open_v3() function.
@@ -221,12 +276,16 @@ struct openvpn_plugin_string_list
  *        variables in "name=value" format.  Note that for security reasons,
  *        these variables are not actually written to the "official"
  *        environmental variable store of the process.
+ *
+ * callbacks : a pointer to the plug-in callback function struct.
+ *
  */
 struct openvpn_plugin_args_open_in
 {
   const int type_mask;
   const char ** const argv;
   const char ** const envp;
+  struct openvpn_plugin_callbacks *callbacks;
 };
 
 
diff --git a/src/openvpn/plugin.c b/src/openvpn/plugin.c
index 7ce2f5e..d785dae 100644
--- a/src/openvpn/plugin.c
+++ b/src/openvpn/plugin.c
@@ -287,6 +287,65 @@ plugin_init_item (struct plugin *p, const struct plugin_option *o)
 }
 
 static void
+plugin_vlog (openvpn_plugin_log_flags_t flags, const char *name, const char *format, va_list arglist)
+{
+  unsigned int msg_flags;
+
+  if (!format)
+    return;
+
+  if (!name || name[0] == '\0')
+    {
+      msg (D_PLUGIN_DEBUG, "PLUGIN: suppressed log message from plugin with unknown name");
+      return;
+    }
+
+  if (flags & PLOG_ERR)
+    msg_flags = M_INFO | M_NONFATAL;
+  else if (flags & PLOG_WARN)
+    msg_flags = M_INFO | M_WARN;
+  else if (flags & PLOG_NOTE)
+    msg_flags = M_INFO;
+  else if (flags & PLOG_DEBUG)
+    msg_flags = D_PLUGIN_DEBUG;
+
+  if (flags & PLOG_ERRNO)
+    msg_flags |= M_ERRNO;
+  if (flags & PLOG_NOMUTE)
+    msg_flags |= M_NOMUTE;
+
+  if (MSG_TEST (msg_flags))
+    {
+      struct gc_arena gc;
+      char* msg_fmt;
+
+      /* Never add instance prefix; not thread safe */
+      msg_flags |= M_NOIPREFIX;
+
+      gc_init (&gc);
+      msg_fmt = gc_malloc (ERR_BUF_SIZE, false, &gc);
+      openvpn_snprintf (msg_fmt, ERR_BUF_SIZE, "PLUGIN %s: %s", name, format);
+      x_msg_va (msg_flags, msg_fmt, arglist);
+
+      gc_free (&gc);
+    }
+}
+
+static void
+plugin_log (openvpn_plugin_log_flags_t flags, const char *name, const char *format, ...)
+{
+  va_list arglist;
+  va_start (arglist, format);
+  plugin_vlog (flags, name, format, arglist);
+  va_end (arglist);
+}
+
+static struct openvpn_plugin_callbacks callbacks = {
+  plugin_log,
+  plugin_vlog
+};
+
+static void
 plugin_open_item (struct plugin *p,
 		  const struct plugin_option *o,
 		  struct openvpn_plugin_string_list **retlist,
@@ -312,7 +371,8 @@ plugin_open_item (struct plugin *p,
       if (p->open3) {
         struct openvpn_plugin_args_open_in args = { p->plugin_type_mask,
                                                     (const char ** const) o->argv,
-                                                    (const char ** const) envp };
+                                                    (const char ** const) envp,
+                                                    &callbacks };
         struct openvpn_plugin_args_open_return retargs;
 
         CLEAR(retargs);