AgentX Tutorial using Net-SNMP

Since no good tutorials are available I put together what I learnt. My approach was step by step learning and that is what I describe here. Explorer should clone this code and checkout step by step. Or an advanced explorer could skip some steps. Your choice. To help understand what is going on, I checkin the code more often so explorer could compare what was auto-generated and what was modification to make things work.

Notes

I used net-snmp 5.7.3 for this tutorial on Ubuntu 16.10.
All code is in flat directory structure in start. Only during the last stage I will move things around to src and include directories to make it cleaner.
We need a MIB first. I created a sample mib AGENTX-TUTORIAL-MIB under experimental branch (.1.3.6.1.3) so my MIB branch is .1.3.6.1.3.9999.
I also created CMakeLists.txt for anyone wanting to use cmake for compiling.

How to use this tutorial?

There are multiple parts in this tutorial. As I described my approach of building it step by step, I strongly recommend to clone the code and start checking out the codes using tags that I have created. Here are the high level commands.

Clone the repository.

git clone https://github.com/jainvishal/agentx-tutorial

Simple MIB with two Read-Only Scalars.
1. Autogenerated code.
```
git checkout step1_scalars_autogenerated
```
2. Modified code with implementation.
```
git checkout step1_scalars_implement
```
Simple MIB with a table using MIB-FOR-Dummies
1. Autogenerated code.
```
git checkout step2_tables_autogenerated
```
2. Modified code with implementation.
```
git checkout step2_tables_implement
```

Simple MIB with Traps

Autogenerated code.
```
git checkout step3_traps_autogenerated
```
Modified code with implementation.
```
git checkout step3_traps_implement
```

Final Cleaned up code
```
git checkout master
```

Step 1 - Simple MIB with two Read-Only Scalars

MIB

In step 1 I implement only two read-only scalars (one integer and one string) since they are easiest to follow. MIB structure is as below.

vishalj@dreams:~/workspace/agentx-tutorial⟫ snmptranslate -Tp -IR agentxTutorial
+--agentxTutorial(9999)
   |
   +--myScalars(1)
   |  |
   |  +-- -R-- String    myROString(1)
   |  |        Textual Convention: DisplayString
   |  |        Size: 0..255
   |  +-- -R-- Integer32 myROInteger(2)
   |           Range: 0..2147483647
   |
   +--myConformenceGroups(99)
      |
      +--myScalarGroup(1)

I used smilint to ensure that mib structure is correct. You can verify it as below and it should not give any errors.

vishalj@dreams:~/workspace/agentx-tutorial⟫ smilint -l 4 -s ./AGENTX-TUTORIAL-MIB

Compiling the MIB / Generating Code

Using mib2c we can compile this MIB into 'C' code. Following three steps show how to create 'C' code, makefile and subagent code respectively.

mib2c -c mib2c.scalar.conf agentxTutorial
mib2c -c mfd-makefile.m2m agentxTutorial
mib2c -c subagent.m2c agentxTutorial

Here is shell output.

vishalj@dreams:~/workspace/agentx-tutorial⟫ mib2c -c mib2c.scalar.conf agentxTutorial
writing to agentxTutorial.h
writing to agentxTutorial.c
running indent on agentxTutorial.c
running indent on agentxTutorial.h
vishalj@dreams:~/workspace/agentx-tutorial⟫ mib2c -c mfd-makefile.m2m agentxTutorial
writing to agentxTutorial_Makefile
vishalj@dreams:~/workspace/agentx-tutorial⟫ mib2c -c subagent.m2c agentxTutorial                                                                                                              
writing to agentxTutorial_subagent.c
running indent on agentxTutorial_subagent.c
vishalj@dreams:~/workspace/agentx-tutorial⟫

Checkin! (git tag: step1_scalars_autogenerated)

I checkin the code now so explorer can see what was generated by mib2c. Nothing would compile anything yet.

Modify the code to make it work

Lets introduce two variables that we are going to monitor and name them as myROStringVar and myROIntVar to match our MIB. I added them in subagent source file agentxTutorial_subagent.c.
Then I added an alarm handler which will update their values every 5 seconds. myRWString will hold the unixtime when myROIntVar changed.
Finally in agentxTutorial.c I updated the placeholders to copy the values from application variables into MIB variables.

Compile the code

use make -f agentxTutorial_makefile or use cmake as follows.

vishalj@dreams:~/workspace/agentx-tutorial⟫ mkdir build
vishalj@dreams:~/workspace/agentx-tutorial⟫ cd build/
vishalj@dreams:~/workspace/agentx-tutorial/build⟫ cmake ../
-- The C compiler identification is GNU 6.2.0
-- The CXX compiler identification is GNU 6.2.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/vishalj/workspace/agentx-tutorial/build
vishalj@dreams:~/workspace/agentx-tutorial/build⟫  make
[ 33%] Building C object CMakeFiles/agentx-tutorial.dir/agentxTutorial.c.o
[ 66%] Building C object CMakeFiles/agentx-tutorial.dir/agentxTutorial_subagent.c.o
[100%] Linking C executable agentx-tutorial
[100%] Built target agentx-tutorial
vishalj@dreams:~/workspace/agentx-tutorial/build⟫

Run the code

On one terminal run it as below. Press CTRL C to kill.

vishalj@dreams:~/workspace/agentx-tutorial/build⟫ ./agentx-tutorial -f
NET-SNMP version 5.7.3 AgentX subagent connected

On other terminal run following snmpwalk commands with some wait in between so you can see the values changing.

vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447214
.1.3.6.1.3.9999.1.2.0 = INTEGER: 1
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447214
.1.3.6.1.3.9999.1.2.0 = INTEGER: 1
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447219
.1.3.6.1.3.9999.1.2.0 = INTEGER: 2
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447219
.1.3.6.1.3.9999.1.2.0 = INTEGER: 2
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447224
.1.3.6.1.3.9999.1.2.0 = INTEGER: 3
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk -On localhost agentxTutorial
.1.3.6.1.3.9999.1.1.0 = STRING: last changed = 1484447254
.1.3.6.1.3.9999.1.2.0 = INTEGER: 9
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫ snmpwalk localhost agentxTutorial
AGENTX-TUTORIAL-MIB::myROString.0 = STRING: last changed = 1484447289
AGENTX-TUTORIAL-MIB::myROInteger.0 = INTEGER: 16
vishalj@dreams:~/workspace/agentx-tutorial/cmake-build-debug⟫

Checkin! (git tag: step1_scalars_implement)

I checkin the code. Thats it for step 1.

Step 2 - Simple Table using MIB FOR DUMMIES

Add table to our MIB

I created myTestTable as a simple table with two columns. So the new MIB structure looks like as below.

vishalj@dreams:~/workspace/agentx-tutorial⟫ snmptranslate -Tp -IR agentxTutorial
+--agentxTutorial(9999)
   |
   +--myScalars(1)
   |  |
   |  +-- -R-- String    myROString(1)
   |  |        Textual Convention: DisplayString
   |  |        Size: 0..255
   |  +-- -R-- Integer32 myROInteger(2)
   |           Range: 0..2147483647
   |
   +--myTables(2)
   |  |
   |  +--myTestTable(1)
   |     |
   |     +--myTestTableEntry(1)
   |        |  Index: myROStringCol1
   |        |
   |        +-- -R-- String    myROStringCol1(1)
   |        |        Textual Convention: DisplayString
   |        |        Size: 0..255
   |        +-- -R-- Integer32 myROIntCol2(2)
   |                 Range: 0..2147483647
   |
   +--myConformenceGroups(99)
      |
      +--myScalarGroup(1)
      +--myTableGroup(2)
vishalj@dreams:~/workspace/agentx-tutorial⟫

Generate code using MIB for Dummies configuration

Now to autogenerate the code using mib2c. I used MIB for dummies which is quite simple to implement.

vishalj@dreams:~/workspace/agentx-tutorial⟫ mib2c -c mib2c.mfd.conf myTestTable
Defaults for myTestTable...
writing to -
There are no defaults for myTestTable. Would you like to

  1) Accept hard-coded defaults
  2) Set defaults now [DEFAULT]

Select your choice : 1
writing to defaults/table-myTestTable.m2d
Starting MFD code generation...
writing to myTestTable.h
| +-> Processing table myTestTable
writing to defaults/node-myROIntCol2.m2d
writing to defaults/node-myROStringCol1.m2d
writing to myTestTable.c
writing to myTestTable_data_get.h
writing to myTestTable_data_get.c
| |   +-> Processing nonindex myROIntCol2
writing to myTestTable_data_set.h
writing to myTestTable_data_set.c
writing to myTestTable_oids.h
writing to myTestTable_enums.h
writing to myTestTable_interface.h
writing to myTestTable_interface.c
writing to myTestTable_data_access.h
writing to myTestTable_data_access.c
writing to myTestTable-README-FIRST.txt
writing to myTestTable-README-myTestTable.txt
running indent on myTestTable_interface.c
running indent on myTestTable.h
running indent on myTestTable_data_access.c
running indent on myTestTable_data_get.c
running indent on myTestTable_oids.h
running indent on myTestTable_enums.h
running indent on myTestTable.c
running indent on myTestTable_interface.h
running indent on myTestTable_data_set.c
running indent on myTestTable_data_access.h
running indent on myTestTable_data_set.h
running indent on myTestTable_data_get.h
vishalj@dreams:~/workspace/agentx-tutorial⟫

In case only table was to be implemented, makefile and subagent code could also be generated by following same steps as described in step 1.

Checkin! (git tag: step2_tables_autogenerated)

I checkin the code now so it can be seen what was generated by mib2c. This new code will not compile yet because we did not add it to makefile yet. And there are many TODOs which need to be resolved in order to load the data.

Modify the code to make it work (at this point diff the files to find updated code)

We need to define our datastore first. I am using /var/tmp/dummy.conf which is supposed to contain two column data. First column will be a string and second an integer, e.g. five 5. Using this external data store will allow us to update it on the fly and see the changes reflect in snmpwalk or other similar commands.

three 3
four 4
two 2
one 1
zero 0

Now we add code to myTestTable_data_access.c.
1. Update myTestTable_init_data to define what columns we are implementing. This allows us to have a table with lots of columns defined in the MIB but only implement a handful. This is helpful in implementing a bigger table step by step.
2. Modify myTestTable_container_load and implement the code to read our external datastore (/var/tmp/dummy.conf) and load the values in internal datastore/container that is provided by Net-SNMP. We first create the index followed by copying the second column. This function will be called each time cache expires which is set to 60 seconds by default. myTestTable_data_access.h includes a macro MYTESTTABLE_CACHE_TIMEOUT which can be tuned for lower or higher values. Value of 0 or less will cause loading of external datastore at each SNMP GET which could be initiated using snmpwalk or snmpget or snmpbulkwalk etc. So be cognizent of the fact that too short interval would cause extra burden of reading a file and may not be advisable based on application's use.
3. Update CMakeLists.txt or agentxTutorial_Makefile whichever you are using to include all the new myTable* files.
Finally update agentxTutorial_subagent.c to initialize our Test Table myTestTable.

Compile the code

Use make -f agentxTutorial_makefile or use cmake as follows.

vishalj@dreams:~/workspace/agentx-tutorial/build⟫ cmake ../
-- The C compiler identification is GNU 6.2.0
-- The CXX compiler identification is GNU 6.2.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/c++
-- Check for working CXX compiler: /usr/bin/c++ -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
-- Generating done
-- Build files have been written to: /home/vishalj/workspace/agentx-tutorial/build
vishalj@dreams:~/workspace/agentx-tutorial/build⟫ make
Scanning dependencies of target agentx-tutorial
[ 12%] Building C object CMakeFiles/agentx-tutorial.dir/myTestTable.c.o
[ 25%] Building C object CMakeFiles/agentx-tutorial.dir/myTestTable_data_access.c.o
[ 37%] Building C object CMakeFiles/agentx-tutorial.dir/myTestTable_data_get.c.o
[ 50%] Building C object CMakeFiles/agentx-tutorial.dir/myTestTable_data_set.c.o
[ 62%] Building C object CMakeFiles/agentx-tutorial.dir/myTestTable_interface.c.o
[ 75%] Building C object CMakeFiles/agentx-tutorial.dir/agentxTutorial.c.o
[ 87%] Building C object CMakeFiles/agentx-tutorial.dir/agentxTutorial_subagent.c.o
[100%] Linking C executable agentx-tutorial
[100%] Built target agentx-tutorial
vishalj@dreams:~/workspace/agentx-tutorial/build⟫

Run the code

Create/update /var/tmp/dummy.conf with following content.

three 3
four 4
two 2
one 1
zero 0

On one terminal run the compiled code as below. Press CTRL C to kill when done.

vishalj@dreams:~/workspace/agentx-tutorial/build⟫ ./agentx-tutorial -f
NET-SNMP version 5.7.3 AgentX subagent connected

On other terminal run following snmpwalk or snmptable commands.

vishalj@dreams:~/workspace/agentx-tutorial⟫ snmpwalk localhost myTestTable
AGENTX-TUTORIAL-MIB::myROStringCol1."one" = STRING: one
AGENTX-TUTORIAL-MIB::myROStringCol1."two" = STRING: two
AGENTX-TUTORIAL-MIB::myROStringCol1."four" = STRING: four
AGENTX-TUTORIAL-MIB::myROStringCol1."zero" = STRING: zero
AGENTX-TUTORIAL-MIB::myROStringCol1."three" = STRING: three
AGENTX-TUTORIAL-MIB::myROIntCol2."one" = INTEGER: 1
AGENTX-TUTORIAL-MIB::myROIntCol2."two" = INTEGER: 2
AGENTX-TUTORIAL-MIB::myROIntCol2."four" = INTEGER: 4
AGENTX-TUTORIAL-MIB::myROIntCol2."zero" = INTEGER: 0
AGENTX-TUTORIAL-MIB::myROIntCol2."three" = INTEGER: 3
vishalj@dreams:~/workspace/agentx-tutorial⟫ snmptable localhost myTestTable
SNMP table: AGENTX-TUTORIAL-MIB::myTestTable

 myROStringCol1 myROIntCol2
            one           1
            two           2
           four           4
           zero           0
          three           3
vishalj@dreams:~/workspace/agentx-tutorial⟫

Now update /var/tmp/dummy.conf with some new content or remove old content. Wait for about a minute and run snmpwalk again to see the updates.

vishalj@dreams:~/workspace/agentx-tutorial⟫ snmpwalk localhost myTestTable
AGENTX-TUTORIAL-MIB::myROStringCol1."one" = STRING: one
AGENTX-TUTORIAL-MIB::myROStringCol1."four" = STRING: four
AGENTX-TUTORIAL-MIB::myROStringCol1."zero" = STRING: zero
AGENTX-TUTORIAL-MIB::myROStringCol1."three" = STRING: three
AGENTX-TUTORIAL-MIB::myROStringCol1."fiftysix" = STRING: fiftysix
AGENTX-TUTORIAL-MIB::myROStringCol1."twentytwo" = STRING: twentytwo
AGENTX-TUTORIAL-MIB::myROIntCol2."one" = INTEGER: 1
AGENTX-TUTORIAL-MIB::myROIntCol2."four" = INTEGER: 4
AGENTX-TUTORIAL-MIB::myROIntCol2."zero" = INTEGER: 0
AGENTX-TUTORIAL-MIB::myROIntCol2."three" = INTEGER: 3
AGENTX-TUTORIAL-MIB::myROIntCol2."fiftysix" = INTEGER: 56
AGENTX-TUTORIAL-MIB::myROIntCol2."twentytwo" = INTEGER: 22
vishalj@dreams:~/workspace/agentx-tutorial⟫ snmptable localhost myTestTable
SNMP table: AGENTX-TUTORIAL-MIB::myTestTable

 myROStringCol1 myROIntCol2
            one           1
           four           4
           zero           0
          three           3
       fiftysix          56
      twentytwo          22
vishalj@dreams:~/workspace/agentx-tutorial⟫

Checkin! (git tag: step2_tables_implement)

I checkin the code. Thats it for step 2.

Step 3 - Implementing a simple Trap

MIB

Now we add a trap definition (myROIntHit) to our MIB. MIB structure is as below. In step 1 I introduced myROInteger which is being incremented every 5 seconds in AlrmHandler. I will now introduce a logic that anytime myROInteger modulo 5 is equal to 1, a trap is generated. e.g. when myROInteger equals 6, 11, 16, 21 and so on.

vishalj@dreams:~/workspace/agentx-tutorial⟫ snmptranslate -Tp -IR agentxTutorial
+--agentxTutorial(9999)
   |
   +--myNotifications(0)
   |  |
   |  +--myNotificationObjects(0)
   |  |  |
   |  |  +-- ---N Integer32 myTrapTime(1)
   |  |  +-- ---N String    myTrapData(2)
   |  |           Textual Convention: DisplayString
   |  |           Size: 0..255
   |  |
   |  +--myROIntHit(1)
   |
   +--myScalars(1)
   |  |
   |  +-- -R-- String    myROString(1)
   |  |        Textual Convention: DisplayString
   |  |        Size: 0..255
   |  +-- -R-- Integer32 myROInteger(2)
   |           Range: 0..2147483647
   |
   +--myTables(2)
   |  |
   |  +--myTestTable(1)
   |     |
   |     +--myTestTableEntry(1)
   |        |  Index: myROStringCol1
   |        |
   |        +-- -R-- String    myROStringCol1(1)
   |        |        Textual Convention: DisplayString
   |        |        Size: 0..255
   |        +-- -R-- Integer32 myROIntCol2(2)
   |                 Range: 0..2147483647
   |
   +--myConformenceGroups(99)
      |
      +--myScalarGroup(1)
      +--myTableGroup(2)
      +--myTrapObjectGroup(3)
      +--myTrapsGroup(4)
vishalj@dreams:~/workspace/agentx-tutorial⟫

Compiling the MIB / Generating Code

Now to autogenerate the code using mib2c. I am using -f flag to tell mib2c where to store the generated code otherwise it will end up overwriting agentxTutorial.[ch] files which we have already updated with out code.

vishalj@dreams:~/workspace/agentx-tutorial⟫ mib2c -c mib2c.notify.conf -f agentxTutorial_traps agentxTutorial
writing to agentxTutorial_traps.h
writing to agentxTutorial_traps.c
running indent on agentxTutorial_traps.h
running indent on agentxTutorial_traps.c
vishalj@dreams:~/workspace/agentx-tutorial⟫

Checkin! (git tag: step3_traps_autogenerated)

I checkin the code now so explorer can see what was generated by mib2c. Nothing would compile anything yet.

Modify the code to make it work (at this point diff the files to find updated code)

So we will update agentxTutorial_traps.h to fill in the trap data. That is quite easy.
Next we update agentxTutorial_subagent.c to add logic to send trap when an interesting event happens. I define a simple event which gets triggered when modulus 5 of myROIntegerVar (value being incremented every 5 seconds) equals 1. So an event goes out at the start, then at value 6, value 11 and so on.

Setup snmpd and snmptrapd to print traps

Configure snmpd (/etc/snmp/snmpd.conf) and ensure that it has a section for sending traps to localhost and restart

trap2sink    localhost public

Now setup snmptrapd to log the traps by ensuring following configuration exists in /etc/snmp/snmptrapd.conf

authCommunity log public

Run snmptrapd on a terminal as snmptrapd -f -Le. (-f means do not fork so it remains attached to the terminal; -Le means log messages on standard error).
Now run our updated agentxTutorial on a terminal as agentxTutorial -f (Again -f means do not fork). Following is what we will see as snmptrapd output. Use CTRL C to exit.

root@dreams:~# snmptrapd -f -Le
NET-SNMP version 5.7.3 AgentX subagent connected
NET-SNMP version 5.7.3
2017-01-27 20:37:50 localhost [UDP: [127.0.0.1]:42445->[127.0.0.1]:162]:
iso.3.6.1.2.1.1.3.0 = Timeticks: (453) 0:00:04.53       iso.3.6.1.6.3.1.1.4.1.0 = OID: iso.3.6.1.3.9999.0.1     iso.3.6.1.3.9999.0.0.2.0 = STRING: "This is a test string"      iso.3.6.1.3.9999.0.0.1.0 = INTEGER: 1485567470  iso.3.6.1.3.9999.1.2.0 = INTEGER: 1
2017-01-27 20:38:15 localhost [UDP: [127.0.0.1]:42445->[127.0.0.1]:162]:
iso.3.6.1.2.1.1.3.0 = Timeticks: (2952) 0:00:29.52      iso.3.6.1.6.3.1.1.4.1.0 = OID: iso.3.6.1.3.9999.0.1     iso.3.6.1.3.9999.0.0.2.0 = STRING: "This is a test string"      iso.3.6.1.3.9999.0.0.1.0 = INTEGER: 1485567495  iso.3.6.1.3.9999.1.2.0 = INTEGER: 6
2017-01-27 20:38:40 localhost [UDP: [127.0.0.1]:42445->[127.0.0.1]:162]:
iso.3.6.1.2.1.1.3.0 = Timeticks: (5452) 0:00:54.52      iso.3.6.1.6.3.1.1.4.1.0 = OID: iso.3.6.1.3.9999.0.1     iso.3.6.1.3.9999.0.0.2.0 = STRING: "This is a test string"      iso.3.6.1.3.9999.0.0.1.0 = INTEGER: 1485567520  iso.3.6.1.3.9999.1.2.0 = INTEGER: 11
2017-01-27 20:39:05 localhost [UDP: [127.0.0.1]:42445->[127.0.0.1]:162]:
iso.3.6.1.2.1.1.3.0 = Timeticks: (7953) 0:01:19.53      iso.3.6.1.6.3.1.1.4.1.0 = OID: iso.3.6.1.3.9999.0.1     iso.3.6.1.3.9999.0.0.2.0 = STRING: "This is a test string"      iso.3.6.1.3.9999.0.0.1.0 = INTEGER: 1485567545  iso.3.6.1.3.9999.1.2.0 = INTEGER: 16
2017-01-27 20:40:35 NET-SNMP version 5.7.3 Stopped.
Stopping snmptrapd
root@dreams:~#

Checkin! (git tag: step3_traps_implement)

I checkin the code. Thats it for step 3.

Cleanup

So far I left all the code in root directory. Lets separate it out so that it is much more clear. Following is our new directory structure.

.
├── agentxTutorial_Makefile
├── AGENTX-TUTORIAL-MIB
├── CMakeLists.txt
├── include
│   ├── agentxTutorial.h
│   ├── agentxTutorial_traps.h
│   └── myTestTable
│       ├── myTestTable_data_access.h
│       ├── myTestTable_data_get.h
│       ├── myTestTable_data_set.h
│       ├── myTestTable_enums.h
│       ├── myTestTable.h
│       ├── myTestTable_interface.h
│       └── myTestTable_oids.h
├── README.md
└── src
    ├── agentxTutorial.c
    ├── agentxTutorial_subagent.c
    ├── agentxTutorial_traps.c
    ├── CMakeLists.txt
    └── myTestTable
        ├── myTestTable.c
        ├── myTestTable_data_access.c
        ├── myTestTable_data_get.c
        ├── myTestTable_data_set.c
        ├── myTestTable_interface.c
        ├── myTestTable-README-FIRST.txt
        └── myTestTable-README-myTestTable.txt

We have to update our CMakeLists.txt (or Makefile) file accordingly. I prefer CMakeLists.txt over the usual Makefile because cmake would put all temporary files in a different directory. That helps me keep my codebsae clean and tidy.

Conclusion

So here is how we implemented a basic MIB with some scalars, a table and a trap using AgentX library provided by Net-SNMP. When I have more time I will provide an implementation of a real application in C++.

svaio/agentx-tutorial

AgentX Tutorial using Net-SNMP

Notes

How to use this tutorial?

Step 1 - Simple MIB with two Read-Only Scalars

MIB

Compiling the MIB / Generating Code

Checkin! (git tag: step1_scalars_autogenerated)

Modify the code to make it work

Compile the code

Run the code

Checkin! (git tag: step1_scalars_implement)

Step 2 - Simple Table using MIB FOR DUMMIES

Add table to our MIB

Generate code using MIB for Dummies configuration

Checkin! (git tag: step2_tables_autogenerated)

Modify the code to make it work (at this point diff the files to find updated code)

Compile the code

Run the code

Checkin! (git tag: step2_tables_implement)

Step 3 - Implementing a simple Trap

MIB

Compiling the MIB / Generating Code

Checkin! (git tag: step3_traps_autogenerated)

Modify the code to make it work (at this point diff the files to find updated code)

Setup snmpd and snmptrapd to print traps

Checkin! (git tag: step3_traps_implement)

Cleanup

Conclusion