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Pim van Pelt
2021-09-12 16:31:13 +00:00
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README.md
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This is an SNMP agent that implements the [Agentx](https://datatracker.ietf.org/doc/html/rfc2257)
protocol. It connects to VPP's `statseg` (statistics memory segment) by MMAPing
it, so the user running the agent must have read access to `/run/vpp/stats.sock`.
It then connects to SNMP's `agentx` socket, which can be either a TCP socket
(by default localhost:705), or a unix domain socket (by default /var/agentx/master)
the latter being readable only by root. It's preferable to run as unprivileged user
It also connects to VPP's API endpoint, so the user running the agent must
have read/write access to `/run/vpp/api.sock`. Both of these are typically accomplished
by running the agent as group `vpp`.
The agent incorporates [pyagentx](https://github.com/hosthvo/pyagentx) with a few
changes, and is released with the BSD 2-clause license.
The agent connects to SNMP's `agentx` socket, which can be either a TCP socket
(by default `localhost:705`), or a unix domain socket (by default `/var/agentx/master`)
the latter being readable only by root. It's preferable to run as unprivileged user,
so a TCP socket is preferred (and the default).
## Running
The agent incorporates a refactored/modified [pyagentx](https://github.com/hosthvo/pyagentx).
The upstream pyagentx code uses a threadpool and message queue, but it was not very stable.
Often, due to lack of proper locking, updaters would overwrite parts of the MIB and as a
result, any reads that were ongoing would abruptly be truncated. I refactored the code to
be single-threaded, greatly simplifying the design (and eliminating the need for locking).
First, configure the snmpd to accept agentx connections by adding the following
to `snmpd.conf`:
```
master agentx
agentXSocket tcp:localhost:705,unix:/var/agentx-dataplane/master
```
and restart snmpd to pick up the changes. Simply run `./vpp-snmp-agent.py` and it
will connect to the snmpd on localhost:705, and expose the IFMib by periodically
polling VPP. Observe the console output.
To respect the original authors, this code is released with the same BSD 2-clause license.
## Building
@ -45,14 +42,34 @@ optional arguments:
sudo cp dist/vpp-snmp-agent /usr/sbin/
```
## SNMPd config
First, configure the snmpd to accept agentx connections by adding (at least) the following
to `snmpd.conf`:
```
master agentx
agentXSocket tcp:localhost:705,unix:/var/agentx-dataplane/master
```
and restart snmpd to pick up the changes. Simply run `./vpp-snmp-agent.py` and it
will connect to the snmpd on localhost:705, and expose the IFMib by periodically
polling VPP. Observe the console output.
## Running in production
Meant to be run on Ubuntu, copy `vpp-snmp-agent.service`, enable and start:
Meant to be run on Ubuntu, copy `*.service`, disable the main snmpd, enable
the one that runs in the dataplane network namespace and start it all up:
```
sudo cp netns-dataplane.service /usr/lib/systemd/system/
sudo cp snmpd-dataplane.service /usr/lib/systemd/system/
sudo cp vpp-snmp-agent.service /usr/lib/systemd/system/
sudo systemctl daemon-reload
sudo systemctl stop snmpd
sudo systemctl disable snmpd
sudo systemctl enable netns-dataplane
sudo systemctl start netns-dataplane
sudo systemctl enable snmpd-dataplane
sudo systemctl start snmpd-dataplane
sudo systemctl enable vpp-snmp-agent

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netns-dataplane.service Normal file
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[Unit]
Description=Dataplane network namespace
After=systemd-sysctl.service network-pre.target
Before=network.target network-online.target
[Service]
Type=oneshot
RemainAfterExit=yes
# PrivateNetwork will create network namespace which can be
# used in JoinsNamespaceOf=.
PrivateNetwork=yes
# To set `ip netns` name for this namespace, we create a second namespace
# with required name, unmount it, and then bind our PrivateNetwork
# namespace to it. After this we can use our PrivateNetwork as a named
# namespace in `ip netns` commands.
ExecStartPre=-/usr/bin/echo "Creating dataplane network namespace"
ExecStart=-/usr/sbin/ip netns delete dataplane
ExecStart=-/usr/bin/mkdir -p /etc/netns/dataplane
ExecStart=-/usr/bin/touch /etc/netns/dataplane/resolv.conf
ExecStart=-/usr/sbin/ip netns add dataplane
ExecStart=-/usr/bin/umount /var/run/netns/dataplane
ExecStart=-/usr/bin/mount --bind /proc/self/ns/net /var/run/netns/dataplane
# Apply default sysctl for dataplane namespace
ExecStart=-/usr/sbin/ip netns exec dataplane /usr/lib/systemd/systemd-sysctl
ExecStop=-/usr/sbin/ip netns delete dataplane
[Install]
WantedBy=multi-user.target
WantedBy=network-online.target