get_community now supported

Netdisco/Changes

@@ -5,6 +5,7 @@
   * Add IP Phones discovered through LLDP/CDP report
   * Add device/node/vlan/port specific search from Navbar
   * [#3] [#47] Device Neighbor Map can have max depth and VLAN filter
+  * [#31] get_community now supported
 
   [ENHANCEMENTS]
 

Netdisco/lib/App/Netdisco/Manual/Configuration.pod

@@ -344,6 +344,30 @@ this you usually configure a common context prefix, with Netdisco's default
 being "C<vlan->" (i.e. C<vlan-1>, C<vlan-2>, etc). Add the C<context_prefix>
 key to a stanza to override this.
 
+=head3 C<get_community>
+
+Value: String. Default none.
+
+An external program to run to get the community string for a given device.
+This is useful if, for example, you have you devices already configured in
+another NMS and you want to use that information instead of configuring
+C<snmp_auth>.
+
+The strings "C<%IP%>" and "C<%HOST%>" are replaced by the IP address and the
+hostname (or IP address if no hostname is known) of the system being
+contacted. For example:
+
+ get_community: '/path/to/my/program %IP%'
+
+The command must return output in the following form:
+
+ community=<comma-separated list of readonly-communities>
+ setCommunity=<comma-separated list of write-communities>
+
+If the community string is not known for the given system, the command should
+return no output and the community strings configured in C<snmp_auth>,
+C<community>, and C<community_rw> will be used instead.
+
 =head3 C<bulkwalk_off>
 
 Value: Boolean. Default C<false>.
@@ -805,10 +829,6 @@ C<expire_nodes_archive>
 
 =item *
 
-C<get_community>
-
-=item *
-
 C<macsuck_timeout>
 
 =item *

Netdisco/lib/App/Netdisco/Util/SNMP.pm

@@ -241,11 +241,11 @@ sub _build_communities {
   my $snmp_comm_rw = eval { $device->community->snmp_comm_rw };
   my @communities = ();
 
-  # first try last-known-good
+  # try last-known-good read
   push @communities, {read => 1, community => $device->snmp_comm}
     if defined $device->snmp_comm and $mode eq 'read';
 
-  # first try last-known-good
+  # try last-known-good write
   push @communities, {write => 1, community => $snmp_comm_rw}
     if $snmp_comm_rw and $mode eq 'write';
 
@@ -299,9 +299,51 @@ sub _build_communities {
       }} @{setting('community_rw') || []};
   }
 
+  # but first of all, use external command if configured
+  unshift @communities, _get_external_community($device, $mode)
+    if setting('get_community') and length setting('get_community');
+
   return @communities;
 }
 
+sub _get_external_community {
+  my ($device, $mode) = @_;
+  my $cmd = setting('get_community');
+  my $ip = $device->ip;
+  my $host = $device->dns || $ip;
+
+  if (defined $cmd and length $cmd) {
+      # replace variables
+      $cmd =~ s/\%HOST\%/$host/egi;
+      $cmd =~ s/\%IP\%/$ip/egi;
+
+      my $result = `$cmd`;
+      return () unless defined $result and length $result;
+
+      my @lines = split (m/\n/, $result);
+      foreach my $line (@lines) {
+          if ($line =~ m/^community\s*=\s*(.*)\s*$/i) {
+              if (length $1 and $mode eq 'read') {
+                  return map {{
+                    read => 1,
+                    community => $_,
+                  }} split(m/\s*,\s*/,$1);
+              }
+          }
+          elsif ($line =~ m/^setCommunity\s*=\s*(.*)\s*$/i) {
+              if (length $1 and $mode eq 'write') {
+                  return map {{
+                    write => 1,
+                    community => $_,
+                  }} split(m/\s*,\s*/,$1);
+              }
+          }
+      }
+  }
+
+  return ();
+}
+
 =head2 snmp_comm_reindex( $snmp, $device, $vlan )
 
 Takes an established L<SNMP::Info> instance and makes a fresh connection using