Merge ~dmzoneill/charm-nrpe:dev/check_mtu into ~nrpe-charmers/charm-nrpe:master

[David O Neill]

MTU checker for neutron-gateway

[Giuseppe Petralia (peppepetra)]

Looks good to me.

review: Approve

[🤖 Canonical IS Merge Bot (canonical-is-mergebot)]

This merge proposal is being monitored by mergebot. Change the status to Approved to merge.

[Xav Paice (xavpaice)]

Example output:

./check_mtu.py --br br-int
br-tun: {'tap1da46df0-92': '1500', 'tap2677f6d5-30': '1500', 'tap2f307b01-8f': '1500', 'tap3ec55528-46': '1500', 'tap419c0544-fb': '1500', 'tap459fbadd-fb': '1500', 'tap490f00ee-2a': '1500', 'tap5f347b80-bc': '1500', 'tap650c3391-0b': '1500', 'tap697a22b3-a9': '8900', 'tap6e473310-2e': '1500', 'tap832fb175-1b': '1500', 'tap88db0ccc-0f': '1500', 'tap8a586526-f3': '1500', 'tap8de5df09-4e': '1500', 'tap9486dc0f-39': '1500', 'tap9aa78180-c4': '1500', 'tapaf94b5dc-0e': '1500', 'tapb3729a8b-c9': '1500', 'tapb91190ec-58': '1500', 'tapc88975d5-c0': '1500', 'tapcb431075-db': '1500', 'tapd60ad8ba-3e': '1500', 'tapdf6a3c1b-d2': '1500', 'tapea6c2a8f-07': '1500', 'tapee3b1760-c7': '1500', 'tapeea0bf18-0d': '1500', 'tapf4d69938-c5': '1500', 'tapfd05a248-11': '8900'}
br-int: {'tap697a22b3-a9': '8900', 'tapfd05a248-11': '8900'}
WARNING: found tenant MTUs greater than bridge MTU

The standards for Nagios plugins dicatate that the plugin should output just one line of info, rather than multiple - otherwise Nagios can't process it.

I don't see any implementation of the plugin here, this just delivers the plugin for something else to make use of it - assuming there's a separate change to the neutron-gateway charm or some such, in order to do that.

review: Needs Fixing

Unmerged commits

0174f7b... by David O Neill on 2020-04-08

MTU checker for neutron-gateway

diff --git a/files/plugins/check_mtu.py b/files/plugins/check_mtu.py
new file mode 100755
index 0000000..5f53efb
--- /dev/null
+++ b/files/plugins/check_mtu.py
@@ -0,0 +1,120 @@
+#!/usr/bin/env python3
+# -*- coding: us-ascii -*-
+
+# Copyright (C) 2017 Canonical
+# All rights reserved
+# Author: David O Neill <[e-mail]>
+
+import argparse
+import subprocess
+
+from nagios_plugin3 import (
+    CriticalError,
+    WarnError,
+    try_check,
+)
+
+
+def get_mtu(device):
+    """Get the MTU of a device."""
+    try:
+        with open("/sys/class/net/" + device + "/mtu") as f:
+            return f.read().strip()
+    except FileNotFoundError:
+        return None
+    except AttributeError:
+        return None
+
+
+def get_taps(bridge):
+    """Return taps array associated with a bridge."""
+    try:
+        process = subprocess.Popen(['ovs-vsctl', 'list-ports', bridge],
+                                   stdout=subprocess.PIPE)
+        return (process.communicate()[0]).decode('utf-8').split('\n')
+    except subprocess.CalledProcessError:
+        raise CriticalError(
+            'CRITICAL: Unable to read bridge information from ovs-vsctl')
+
+
+def check_bridge_mtus(iface_br, iface_remap):
+    """Check that the tap devices associated with bridge have smaller MTUS. """
+    bridge_iface = iface_remap if iface_remap is not False else iface_br
+    ifaces = get_taps(bridge_iface)
+
+    bridge_mtu = get_mtu(iface_br)
+    bad_mtus = {}
+
+    for iface in ifaces:
+        mtu = get_mtu(iface)
+        if mtu is not None:
+            if iface_remap is not False:
+                # gre 24 bytes, vxlan 50 recommended padding
+                if int(mtu) + 50 > int(bridge_mtu):
+                    bad_mtus[iface] = mtu
+            else:
+                if int(mtu) > int(bridge_mtu):
+                    bad_mtus[iface] = mtu
+
+    return bad_mtus
+
+
+def iterate_bridges(bridges):
+    """Iterates the bridges."""
+    results = {}
+    to_check = {
+        'br-tun': 'br-int'
+    }
+
+    if " " in bridges.strip():
+        # mutiple bridges to check
+        for brbinding in bridges.split(" "):
+            to_check[brbinding] = False
+    else:
+        # single bridge
+        to_check[bridges] = False
+
+    for key, value in to_check.items():
+        # format is br-ex:eno2
+        iface_br = key if ":" not in key else key.split(":")[0]
+        results[iface_br] = check_bridge_mtus(iface_br, value)
+
+    nagios_ok = True
+    for bridge in results.keys():
+        if len(results[bridge].keys()) > 0:
+            print(bridge + ": " + str(results[bridge]))
+            nagios_ok = False
+
+    if nagios_ok:
+        print("OK: Tenant MTU configuration is sane")
+    else:
+        msg = 'WARNING: found tenant MTUs greater than bridge MTU'
+        raise WarnError(msg)
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='Check mtu on bridge slaves')
+    parser.add_argument('--br', '-br', help='space separated list of bridges')
+    args = parser.parse_args()
+    return args
+
+
+def main():
+    """
+        GRE padding typically 22 bytes,
+        The recommended padding for vxlan is 50.
+        Assuming 50 for all encapped networks.
+                                      9000
+        1450       1450     1450      1500      1450
+        packet -> br-ex -> br-int -> br-tun -> machine
+    """
+    args = parse_args()
+
+    if args.br is None or args.br.strip() == "":
+        raise CriticalError('WARNING: No bridges provided for MTU check?')
+
+    try_check(iterate_bridges, args.br)
+
+
+if __name__ == '__main__':
+    main()