snmp_diagnostics

ROS diagnostics created from SNMP agent data

Nodes

snmp_diagnostics

ROS node that reads various data over SNMP and turns them into ROS diagnostics messages.

Parameters

• ~agent_address (str, default ‘127.0.0.1’): Address of the SNMP agent.
• ~agent_port (int, default 161): UDP port of the SNMP agent.
• ~community (str, default ‘public’): SNMP community.
• ~snmp_v2 (bool, default True): Whether to use SNMPv2c or SNMPv1.
• ~udpv6 (bool, default False): Whether to use UDPv6 transport or UDPv4.
• ~rate (float, default 1.0): The rate at which the SNMP agent is polled.
• ~plugins (dict): Plugin-specific configuration. Keys are config_key attributes of the plugins (e.g. if_mib). Values are dictionaries described further for each plugin.

Known MIB Processing Plugins

So far, there is only a single plugin, but more are planned to be added (e.g. host resources).

if_mib

This plugin reads IF-MIB (1.3.6.1.2.1.2 and 1.3.6.1.2.1.31) and extracts information about network ports and their status.

Parameters

• num_ports (int, optional): If specified, the diagnostics will check that exactly this number of ports is reported.
• ports (dict port_name => port_params): Specification of the expected ports. port_name is a string identifying the port (e.g. eth0), mangled either from ifAlias, ifName or ifDescr (see below). port_params is a dict with following keys:
  • connected (bool, optional): Check that the connection state of this port is as specified.
  • speed (int or tuple (int, int), optional): The expected speed of the port in Mbps. If a tuple is specified, it denotes a (min, max) range.
  • mtu (int or tuple (int, int), optional): The expected MTU of the port in B. If a tuple is specified, it denotes a (min, max) range.
  • dummy (whatever): If you only need to specify a port to be present, but do not require any particular properties or state, just specify a dummy parameter so that the port’s key is present in the ports dictionary.

The port_name is mangled so that it is a valid ROS graph resource name - i.e. matching regex ^[a-zA-Z][a-zA-Z0-9_]*$. To perform this mangling, iconv //TRANSLIT feature is used to find the “closest” ASCII character to all non-ASCII ones, and then all non-alphanumeric characters are replaced by underscores (e.g. spaces), and multiple underscores are coalesced into a single one. If the resulting name is not a valid graph resource name (e.g. it starts with number), the next name “source” is tried - in the order ifAlias, ifName, ifDescr.

Writing a new plugin

To create a new plugin processing different MIBs, just write a normal Python ROS package that exports a Python package containing your plugin. The plugin has to inherit from class snmp_diagnostics.SnmpDiagPlugin and implement its abstract methods.

Add the following lines to your package’s package.xml:

<exec_depend>snmp_diagnostics</exec_depend>
<export>
    <snmp_diagnostics class="my_package.module.Class" config_key="my_plugin" />
</export>

Make sure my_package.module.Class is the fully qualified name of your plugin class. config_key if the name under which you will configure the plugin on ROS parameter server, i.e. it will get its configuration from ~/plugins/<config_key>.

Easy configuration of local machine to provide SNMP info about itself

This is a simplified version of the process described at https://askubuntu.com/a/223734/153828 .

• Install system packages snmp, snmpd, snmp-mibs-downloader .
• Run echo "view systemonly included .1.3.6.1.2.1.2" | sudo tee -a /etc/snmp/snmpd.conf for each MIB you want to enable. Just substitute the exact MIB number.
• sudo sed -i 's/^mibs :$/# mibs :/' /etc/snmp/snmp.conf
• sudo systemctl enable snmpd && sudo systemctl start snmpd
• Then you should be able to walk your local machine: snmpwalk -v 2c -c public 127.0.0.1 . If not, try restarting the snmpd daemon.