SNMP_AGENT_API(3)SNMP_AGENT_API(3)NAMEsnmp_agent_api - embedding an agent into a external appli
cation
SYNOPSIS
#include <ucd-snmp/ucd-snmp-config.h>
#include <ucd-snmp/ucd-snmp-includes.h>
#include <ucd-snmp/ucd-snmp-agent-includes.h>
main () {
int agentx_subagent=1; /* change this if you're a master agent */
snmp_enable_stderrlog();
/* if we're an agentx subagent */
if (agentx_subagent) {
/* make us a agentx client. */
ds_set_boolean(DS_APPLICATION_ID, DS_AGENT_ROLE, 1);
}
init_agent("yourappname");
/* initialize your mib code here */
init_my_mib_code();
/* yourappname will be used to read yourappname.conf files. */
init_snmp("yourappname");
/* If we're going to be a snmp master agent */
if (!agentx_subagent)
init_master_agent(161, NULL, NULL); /* open port 161 (UDP:snmp) */
/* you're main loop here... */
while(whatever) {
/* if you use select(), see snmp_api(3) */
/* --- OR --- */
agent_check_and_process(0); /* 0 == don't block */
}
/* at shutdown time */
snmp_shutdown("yourappname");
}
Then:
cc ... -lucdagent -lucdmibs -lsnmp # other libraries may be needed here
DESCRIPTION
Our goal is to create a easy to use interface to the ucd-
snmp package such that you can take code that you have
written that has been designed to be a ucd-snmp mib module
and embed it into an external application where you can
either chose to be a SNMP master agent or an AgentX sub-
agent using the same mib module code. Our suggestion is
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that you use our (or another) SNMP agent as the AgentX
master agent and chose to become an AgentX subagent which
then attaches to the master.
Starting with version 4.1, the ucd-snmp package provides a
pair of libraries that enables easy embedding of an SNMP
or AgentX agent into an external software package. AgentX
is an extensible protocol designed to allow multiple SNMP
sub-agents all run on one machine under a single SNMP mas
ter agent. It is defined in RFC 2741.
You will need to perform a few tasks in order to accom
plish this. First off, you will need to initialize both
the SNMP library and the SNMP agent library. As indicated
above, this is done slightly differently depending on
whether or not you are going to perform as a master agent
or an AgentX sub-agent.
CONFIGURATION
If you intend to operate as an AgentX sub-agent, you will
have to configured the ucd-snmp package as follows:
./configure --with-mib-modules="agentx/subagent"
Additionally, you will need to link against the libucdmibs
library and call subagent_pre_init() as indicated above.
COMPILING
In order to make use of any of the above API, you will
need to clinch against at least two libraries: the
libucdagent library and the libsnmp library. Additionally,
if you plan to make use of any of the code in the agent's
mib modules (like the AgentX subagent support), you will
need to link against the libucdmibs library as well.
FUNCTIONSsnmp_enable_stderrlog()
Logs error output from the SNMP agent to the stan
dard error stream.
ds_set_boolean()
Please see the default_store(3) manual page for
more information about this API.
init_agent(char *name)
Initializes the embedded agent. This should be
called before the init_snmp() call. name is used
to dictate what .conf file to read when init_snmp()
is called later.
init_snmp(char *name)
Initializes the SNMP library. Note that one of the
things this will do will be to read configuration
files in an effort to configure your application.
It will attempt to read the configuration files
named by the name string that you passed in. It
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can be used to configure access control, for
instance. Please see the read_config(3),
snmp_config(5), and snmpd.conf(5) manual pages for
further details on this subject.
init_master_agent(port, NULL, NULL)
Initializes the master agent and opens all its nec
essary ports. port is the port you want to listen
for SNMP requests on.
agent_check_and_process(int block)
This checks for packets arriving on the SNMP port
and processes them if some are found. If block is
non-zero, the function call will block until a
packet arrives or an alarm must be run (see
snmp_alarm(3)). The return value from this function
is a positive integer if packets were processed,
zero if an alarm occurred and -1 if an error
occured.
snmp_shutdown(char *name);
This shuts down the agent, saving any needed per
sistent storage, etc.
SEE ALSOselect(2), snmp_api(3), default_store(3), snmp_alarm(3),
read_config(3), snmp_config(5), snmpd.conf(5)
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