Clixon SNMP frontend update

Integrated netsnmp agent and clixon event handling, made a workaround of fdset:s
used in the netsnmp API with sockets used in Clixon
Added a hardcoded MIB OID handler as subagent
Added libnetsnmpagent to autotools dependency check
New OE_SNMP error code

apps/snmp/snmp_main.c

@@ -30,7 +30,6 @@
   the terms of any one of the Apache License version 2 or the GPL.
 
   ***** END LICENSE BLOCK *****
-
  */
 
 #ifdef HAVE_CONFIG_H
@@ -45,7 +44,10 @@
 #include <sys/types.h>
 #include <signal.h>
 
+/* net-snmp */
 #include <net-snmp/net-snmp-config.h>
+#include <net-snmp/net-snmp-includes.h>
+#include <net-snmp/agent/net-snmp-agent-includes.h>
 
 /* cligen */
 #include <cligen/cligen.h>
@@ -56,18 +58,181 @@
 /* Command line options to be passed to getopt(3) */
 #define SNMP_OPTS "hD:f:l:o:"
 
-/*! XXX netsnmp API goes here
+#if 1 // XXX hardcoded MIB object from https://github.com/net-snmp/subagent-example/blob/master/example-demon.c
+/* cp NET-SNMP-TUTORIAL-MIB.txt ~/.snmp/mibs/
+ * sudo /usr/local/sbin/snmpd -Lo -C --rwcommunity=public --master=agentx -f
+ * sudo example_demon
+ * snmpget -v 2c -c public localhost NET-SNMP-TUTORIAL-MIB::nstAgentSubagentObject.0
+ */
+/*! 
+ * our initialization routine, automatically called by the agent 
+ * (to get called, the function name must match init_FILENAME()) 
+ * the variable we want to tie an OID to.  The agent will handle all
+ * * GET and SET requests to this variable changing it's value as needed.
+ */
+static long      nstAgentSubagentObject = 2;
+
+static void
+init_nstAgentSubagentObject(clicon_handle h)
+{
+    static oid      nstAgentSubagentObject_oid[] =
+        { 1, 3, 6, 1, 4, 1, 8072, 2, 4, 1, 1, 2, 0 };
+
+    clicon_debug(1, "%s", __FUNCTION__);
+    /*
+     * a debugging statement.  Run the agent with -DnstAgentSubagentObject to see
+     * the output of this debugging statement. 
+     */
+    DEBUGMSGTL(("nstAgentSubagentObject",
+                "Initializing the nstAgentSubagentObject module\n"));
+
+    /*
+     * the line below registers our variables defined above as
+     * accessible and makes it writable.  A read only version of any
+     * of these registration would merely call
+     * register_read_only_long_instance() instead.  The functions
+     * called below should be consistent with your MIB, however.
+     * 
+     * If we wanted a callback when the value was retrieved or set
+     * (even though the details of doing this are handled for you),
+     * you could change the NULL pointer below to a valid handler
+     * function. 
+     */
+    DEBUGMSGTL(("nstAgentSubagentObject",
+                "Initalizing nstAgentSubagentObject scalar integer.  Default value = %ld\n",
+                nstAgentSubagentObject));
+
+    netsnmp_register_long_instance("nstAgentSubagentObject",
+                                  nstAgentSubagentObject_oid,
+                                  OID_LENGTH(nstAgentSubagentObject_oid),
+                                  &nstAgentSubagentObject, NULL);
+
+    DEBUGMSGTL(("nstAgentSubagentObject",
+                "Done initalizing nstAgentSubagentObject module\n"));
+}
+#endif // XXX Hardcoded
+
+/*! Signal terminates process
+ * Just set exit flag for proper exit in event loop
+ */
+static void
+clixon_snmp_sig_term(int arg)
+{
+    clicon_log(LOG_NOTICE, "%s: %s: pid: %u Signal %d", 
+	       __PROGRAM__, __FUNCTION__, getpid(), arg);
+    /* This should ensure no more accepts or incoming packets are processed because next time eventloop
+     * is entered, it will terminate.
+     * However there may be a case of sockets closing rather abruptly for clients
+     */
+    clixon_exit_set(1); 
+}
+
+/*! Callback for single socket 
+ * This is a workaround for netsnmps API usiing fdset:s, instead an fdset is created before calling
+ * the snmp api
+ * @param[in]  s   Read socket
+ * @param[in]  arg Clixon handle
  */
 static int
-snmp_input_cb(int   s, 
+clixon_snmp_input_cb(int   s, 
-	      void *arg)
+		     void *arg)
 {
-    int retval = -1;
+    int    retval = -1;
+    fd_set readfds;
+    //    clicon_handle h = (clicon_handle)arg;
+
+    clicon_debug(1, "%s", __FUNCTION__);
+    FD_ZERO(&readfds);
+    FD_SET(s, &readfds);
+    snmp_read(&readfds);
     retval = 0;
     // done:
     return retval;
 }
 
+/*! Get which sockets are used from SNMP API, the register single sockets into clixon event system
+ *
+ * This is a workaround for netsnmps API usiing fdset:s, instead an fdset is created before calling
+ * the snmp api
+ * if you use select(), see snmp_select_info() in snmp_api(3) 
+ * snmp_select_info(int *numfds, fd_set *fdset, struct timeval *timeout, int *block)
+ * @see clixon_snmp_input_cb
+ */
+static int
+clixon_snmp_fdset_register(clicon_handle h)
+{
+    int             retval = -1;
+    int             numfds = 0;
+    fd_set          readfds;
+    struct timeval  timeout = { LONG_MAX, 0 };
+    int             block = 0;
+    int             nr;
+    int             i;
+
+    FD_ZERO(&readfds);
+    if ((nr = snmp_sess_select_info(NULL, &numfds, &readfds, &timeout, &block)) < 0){
+	clicon_err(OE_SNMP, errno, "snmp_select_error");
+	goto done;
+    }
+    for (i=0; i<numfds; i++){
+	if (FD_ISSET(i, &readfds)){
+	    if (clixon_event_reg_fd(i, clixon_snmp_input_cb, h, "snmp socket") < 0)
+		goto done;
+	}
+    }
+    retval = 0;
+ done:
+    return retval;
+}
+
+/*! Init netsnmp agent connection
+ * @param[in]  h      Clixon handle
+ * @param[in]  logdst Log destination, see clixon_log.h
+ * @see snmp_terminate
+ */
+static int
+clixon_snmp_init(clicon_handle h,
+		 int           logdst)
+{
+    int retval = -1;
+
+    clicon_debug(1, "%s", __FUNCTION__);
+    if (logdst == CLICON_LOG_SYSLOG)
+	snmp_enable_calllog();
+    else
+	snmp_enable_stderrlog();
+    /* make a agentx client. */
+    netsnmp_ds_set_boolean(NETSNMP_DS_APPLICATION_ID, NETSNMP_DS_AGENT_ROLE, 1);    
+
+    /* initialize the agent library */
+    init_agent(__PROGRAM__);
+  
+    /* XXX Hardcoded, replace this with generic MIB */
+    init_nstAgentSubagentObject(h);
+
+    /* example-demon will be used to read example-demon.conf files. */
+    init_snmp(__PROGRAM__);
+
+    if (set_signal(SIGTERM, clixon_snmp_sig_term, NULL) < 0){
+	clicon_err(OE_DAEMON, errno, "Setting signal");
+	goto done;
+    }
+    if (set_signal(SIGINT, clixon_snmp_sig_term, NULL) < 0){
+	clicon_err(OE_DAEMON, errno, "Setting signal");
+	goto done;
+    }
+    if (set_signal(SIGPIPE, SIG_IGN, NULL) < 0){
+	clicon_err(OE_UNIX, errno, "Setting DIGPIPE signal");
+	goto done;
+    }
+    /* Workaround for netsnmps API use of fdset:s instead of sockets */
+    if (clixon_snmp_fdset_register(h) < 0)
+	goto done;
+    retval = 0;
+ done:
+    return retval;
+}
+
 
 /*! Clean and close all state of netconf process (but dont exit). 
  * Cannot use h after this 
@@ -80,6 +245,7 @@ snmp_terminate(clicon_handle h)
     cvec       *nsctx;
     cxobj      *x;
     
+    shutdown_agent();
     clicon_rpc_close_session(h);
     if ((yspec = clicon_dbspec_yang(h)) != NULL)
 	ys_free(yspec);
@@ -97,21 +263,6 @@ snmp_terminate(clicon_handle h)
     return 0;
 }
 
-/*! Setup signal handlers
- */
-static int
-snmp_signal_init (clicon_handle h)
-{
-    int retval = -1;
-    
-    if (set_signal(SIGPIPE, SIG_IGN, NULL) < 0){
-	clicon_err(OE_UNIX, errno, "Setting DIGPIPE signal");
-	goto done;
-    }
-    retval = 0;
- done:
-    return retval;
-}
 
 /*! Usage help routine
  * @param[in]  h      Clixon handle
@@ -194,6 +345,7 @@ main(int    argc,
      */
     clicon_log_init(__PROGRAM__, dbg?LOG_DEBUG:LOG_INFO, logdst); 
     clicon_debug_init(dbg, NULL); 
+
     yang_init(h);
     
     /* Find, read and parse configfile */
@@ -246,13 +398,11 @@ main(int    argc,
     if (netconf_module_features(h) < 0)
 	goto done;
 
-    /* Setup signal handlers, int particular PIPE that occurs if backend closes / restarts */
-    if (snmp_signal_init(h) < 0)
-	goto done;
-    
     /* In case ietf-yang-metadata is loaded by application, handle annotation extension */
-    if (0 && yang_metadata_init(h) < 0)
+#if 0
+    if (yang_metadata_init(h) < 0)
 	goto done;    
+#endif
     /* Create top-level yang spec and store as option */
     if ((yspec = yspec_new()) == NULL)
 	goto done;
@@ -292,13 +442,13 @@ main(int    argc,
     if (clicon_nsctx_global_set(h, nsctx_global) < 0)
 	goto done;
 
+#if 0
     /* Call start function is all plugins before we go interactive */
     if (clixon_plugin_start_all(h) < 0)
 	goto done;
-#if 1
-    /* XXX get session id from backend hello */
-    clicon_session_id_set(h, getpid()); 
 #endif
+    /* Get session id from backend hello */
+    clicon_session_id_set(h, getpid()); 
 
     /* Send hello request to backend to get session-id back
      * This is done once at the beginning of the session and then this is
@@ -309,12 +459,10 @@ main(int    argc,
 	goto done;
     clicon_session_id_set(h, id);
     
-    /* XXX Here should register an net-snmp interface socket
+    /* Init snmp as subagent */
-     * But it registers stdin which is wrong
+    if (clixon_snmp_init(h, logdst) < 0)
-     */
-    if (clixon_event_reg_fd(0, snmp_input_cb, h, "snmp socket") < 0)
 	goto done;
-
+    
     if (dbg)
 	clicon_option_dump(h, dbg);
     if (clixon_event_loop(h) < 0)

configure

@@ -5324,10 +5324,10 @@ $as_echo "checking netsnmp is enabled: $enable_netsnmp" >&6; }
 
 if test "$enable_netsnmp" = "yes"; then
    # All libs are:
-   # libnetsnmp, libnetsnmpmibs, libnetsnmpagent, libnetsnmptrapd, libnetsnmphelpers
+   # libnetsnmp, libnetsnmpagent, libnetsnmpmibs, libnetsnmptrapd, libnetsnmphelpers
-   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for snmp_open in -lnetsnmp" >&5
+   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for init_snmp in -lnetsnmp" >&5
-$as_echo_n "checking for snmp_open in -lnetsnmp... " >&6; }
+$as_echo_n "checking for init_snmp in -lnetsnmp... " >&6; }
-if ${ac_cv_lib_netsnmp_snmp_open+:} false; then :
+if ${ac_cv_lib_netsnmp_init_snmp+:} false; then :
   $as_echo_n "(cached) " >&6
 else
   ac_check_lib_save_LIBS=$LIBS
@@ -5341,33 +5341,78 @@ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 #ifdef __cplusplus
 extern "C"
 #endif
-char snmp_open ();
+char init_snmp ();
 int
 main ()
 {
-return snmp_open ();
+return init_snmp ();
   ;
   return 0;
 }
 _ACEOF
 if ac_fn_c_try_link "$LINENO"; then :
-  ac_cv_lib_netsnmp_snmp_open=yes
+  ac_cv_lib_netsnmp_init_snmp=yes
 else
-  ac_cv_lib_netsnmp_snmp_open=no
+  ac_cv_lib_netsnmp_init_snmp=no
 fi
 rm -f core conftest.err conftest.$ac_objext \
     conftest$ac_exeext conftest.$ac_ext
 LIBS=$ac_check_lib_save_LIBS
 fi
-{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_netsnmp_snmp_open" >&5
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_netsnmp_init_snmp" >&5
-$as_echo "$ac_cv_lib_netsnmp_snmp_open" >&6; }
+$as_echo "$ac_cv_lib_netsnmp_init_snmp" >&6; }
-if test "x$ac_cv_lib_netsnmp_snmp_open" = xyes; then :
+if test "x$ac_cv_lib_netsnmp_init_snmp" = xyes; then :
   cat >>confdefs.h <<_ACEOF
 #define HAVE_LIBNETSNMP 1
 _ACEOF
 
   LIBS="-lnetsnmp $LIBS"
 
+fi
+
+   { $as_echo "$as_me:${as_lineno-$LINENO}: checking for init_agent in -lnetsnmpagent" >&5
+$as_echo_n "checking for init_agent in -lnetsnmpagent... " >&6; }
+if ${ac_cv_lib_netsnmpagent_init_agent+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_check_lib_save_LIBS=$LIBS
+LIBS="-lnetsnmpagent  $LIBS"
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char init_agent ();
+int
+main ()
+{
+return init_agent ();
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_lib_netsnmpagent_init_agent=yes
+else
+  ac_cv_lib_netsnmpagent_init_agent=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext conftest.$ac_ext
+LIBS=$ac_check_lib_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_lib_netsnmpagent_init_agent" >&5
+$as_echo "$ac_cv_lib_netsnmpagent_init_agent" >&6; }
+if test "x$ac_cv_lib_netsnmpagent_init_agent" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_LIBNETSNMPAGENT 1
+_ACEOF
+
+  LIBS="-lnetsnmpagent $LIBS"
+
 fi
 
    for ac_header in net-snmp/net-snmp-config.h

configure.ac

@@ -289,8 +289,9 @@ AC_MSG_RESULT(checking netsnmp is enabled: $enable_netsnmp)
 
 if test "$enable_netsnmp" = "yes"; then
    # All libs are:
-   # libnetsnmp, libnetsnmpmibs, libnetsnmpagent, libnetsnmptrapd, libnetsnmphelpers
+   # libnetsnmp, libnetsnmpagent, libnetsnmpmibs, libnetsnmptrapd, libnetsnmphelpers
-   AC_CHECK_LIB(netsnmp, snmp_open)      
+   AC_CHECK_LIB(netsnmp, init_snmp)
+   AC_CHECK_LIB(netsnmpagent, init_agent)	
    AC_CHECK_HEADERS(net-snmp/net-snmp-config.h,[], AC_MSG_ERROR([snmp is missing]))
 fi 
 

include/clixon_config.h.in

@@ -63,6 +63,9 @@
 /* Define to 1 if you have the `netsnmp' library (-lnetsnmp). */
 #undef HAVE_LIBNETSNMP
 
+/* Define to 1 if you have the `netsnmpagent' library (-lnetsnmpagent). */
+#undef HAVE_LIBNETSNMPAGENT
+
 /* Define to 1 if you have the `nghttp2' library (-lnghttp2). */
 #undef HAVE_LIBNGHTTP2
 

lib/clixon/clixon_err.h

@@ -74,6 +74,7 @@ enum clicon_err{
     OE_RESTCONF, /* RESTCONF errors */
     OE_PLUGIN,   /* plugin loading, etc */
     OE_YANG ,    /* Yang error */
+    OE_SNMP ,    /* Netsnmp error */
     OE_FATAL,    /* Fatal error */
     OE_UNDEF,
     /*-- From here error extensions using clixon_err_cat_reg, XXX register dynamically? --*/