vyos-netlinkd: T8047: add proof-of-concept for a netlink listener daemon #4872

c-po · 2025-11-26T21:43:27Z

Change summary

Implementing a daemon that listens for netlink messages in Python was discussed for many years. This is a proof-of-concept implementation how we can listen for netlink messages and process them in Python.

NOTE Python 3.10 minimum is required due to the use of case statements which mimics C-style switch/case instructions.

Add example

set interfaces ethernet eth1 vif 21
commit

vyos-configd[4690]: Received message: {"type": "node", "last": true, "data": "VYOS_TAGNODE_VALUE=eth1/usr/libexec/vyos/conf_mode/interfaces_ethernet.py"}
vyos-netlinkd[5955]: RTM_NEWLINK -> eth1, state=UP, mac=00:50:56:b3:38:c5
vyos-netlinkd[5955]: RTM_NEWLINK -> eth1.21, state=DOWN, mac=00:50:56:b3:38:c5

Remove example

delete interfaces ethernet eth1 vif
commit

vyos-configd[4690]: Received message: {"type": "node", "last": true, "data": "VYOS_TAGNODE_VALUE=eth1/usr/libexec/vyos/conf_mode/interfaces_ethernet.py"}
vyos-netlinkd[6803]: Received event RTM_DELADDR - unhandled!
vyos-netlinkd[6803]: RTM_NEWLINK -> eth1, state=UP, mac=00:50:56:b3:38:c5
vyos-netlinkd[6803]: RTM_NEWLINK -> eth1.21, state=DOWN, mac=00:50:56:b3:38:c5

Message parsing of course needs to be improved for real-world use!

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Code style update (formatting, renaming)
Refactoring (no functional changes)
Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
Other (please describe):

Related Task(s)

https://vyos.dev/T8047

Related PR(s)

T7965: reapply the QoS policy when the interface reconnect #4837

Checklist:

I have read the CONTRIBUTING document
I have linked this PR to one or more Phabricator Task(s)
I have run the components SMOKETESTS if applicable
My commit headlines contain a valid Task id
My change requires a change to the documentation
I have updated the documentation accordingly

github-actions · 2025-11-26T21:43:41Z

👍
No issues in PR Title / Commit Title

Implementing a daemon that listens for netlink messages in Python was discussed for many years. This is a proof-of-concept implementation how we can listen for netlink messages and process them in Python. Python 3.10 minimum is required due to the use of case statements which mimics C-style switch/case instructions. Add example: set interfaces ethernet eth1 vif 21 commit vyos-configd[4690]: Received message: {"type": "node", "last": true, "data": "VYOS_TAGNODE_VALUE=eth1/usr/libexec/vyos/conf_mode/interfaces_ethernet.py"} vyos-netlinkd[5955]: RTM_NEWLINK -> eth1, state=UP, mac=00:50:56:b3:38:c5 vyos-netlinkd[5955]: RTM_NEWLINK -> eth1.21, state=DOWN, mac=00:50:56:b3:38:c5 Remove example: delete interfaces ethernet eth1 vif commit vyos-configd[4690]: Received message: {"type": "node", "last": true, "data": "VYOS_TAGNODE_VALUE=eth1/usr/libexec/vyos/conf_mode/interfaces_ethernet.py"} vyos-netlinkd[6803]: Received event RTM_DELADDR - unhandled! vyos-netlinkd[6803]: RTM_NEWLINK -> eth1, state=UP, mac=00:50:56:b3:38:c5 vyos-netlinkd[6803]: RTM_NEWLINK -> eth1.21, state=DOWN, mac=00:50:56:b3:38:c5 Message parsing of course needs to be improved for real-world use!

github-actions · 2025-11-27T08:29:16Z

CI integration ❌ failed!

Details

CI logs

CLI Smoketests (no interfaces) ❌ failed
CLI Smoketests VPP 👍 passed
CLI Smoketests (interfaces only) 👍 passed
Config tests 👍 passed
Config tests VPP 👍 passed
RAID1 tests 👍 passed
TPM tests 👍 passed

sever-sever · 2025-11-28T12:34:53Z

src/services/vyos-netlinkd

+                        syslog.syslog(syslog.LOG_INFO,
+                                      f'RTM_NEWLINK -> {iface}, state={operstate}, mac={mac}')


Will PPPoE interfaces also log?
For example, for BRAS. There could be thousands of interfaces.

Copilot

Pull request overview

This PR introduces a proof-of-concept netlink listener daemon (vyos-netlinkd) that monitors and logs network interface changes via netlink messages in Python, leveraging Python 3.10+ match/case statements.

Adds a new systemd service unit for the netlink daemon
Implements basic netlink event handling for RTM_NEWLINK and RTM_DELLINK messages
Provides a foundation for future netlink-based monitoring capabilities

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
src/systemd/vyos-netlinkd.service	Defines systemd service configuration for the netlink daemon with early startup ordering
src/services/vyos-netlinkd	Implements the main daemon logic with netlink message processing and signal handling

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Copilot · 2025-11-28T12:35:51Z

src/services/vyos-netlinkd

+    ipr = IPRoute()
+    ipr.bind()
+    fd = ipr.fileno()
+
+    global running
+    while running:
+        try:
+            # Wait for up to 1 second for a netlink message
+            rlist, _, _ = select.select([fd], [], [], 1.0)
+            if not rlist:
+                # timeout - retry
+                continue
+
+            # Receive and process any messages
+            for message in ipr.get():
+                event_type = message['event']
+                match event_type:
+                    case 'RTM_NEWLINK':
+                        attrs = dict(message.get('attrs', []))
+                        iface = attrs.get('IFLA_IFNAME', '<unknown>')
+                        operstate = attrs.get('IFLA_OPERSTATE', '<unknown>')
+                        mac = attrs.get('IFLA_ADDRESS', '<unknown>')
+                        syslog.syslog(syslog.LOG_INFO,
+                                      f'RTM_NEWLINK -> {iface}, state={operstate}, mac={mac}')
+
+                    case 'RTM_DELLINK':
+                        attrs = dict(message.get('attrs', []))
+                        iface = attrs.get('IFLA_IFNAME', '<unknown>')
+                        syslog.syslog(syslog.LOG_INFO, f'RTM_DELLINK -> {iface}')
+
+                    case _:
+                        syslog.syslog(syslog.LOG_INFO, f'Received event {event_type} - unhandled!')
+
+        except NetlinkError as e:
+            syslog.syslog(syslog.LOG_ERR, f'Netlink error: {e}')
+        except KeyboardInterrupt:
+            break
+        except Exception as e:
+            syslog.syslog(syslog.LOG_ERR, f'Unhandled exception: {e}')
+
+    ipr.close()
+    syslog.syslog(syslog.LOG_INFO, 'Netlink listener daemon stopped.')
+    exit(0)


The IPRoute socket is closed outside the main loop, but if an exception occurs during initialization (lines 37-39) or within the loop before setting running=False, the socket may not be properly closed. Consider using a try-finally block or context manager to ensure cleanup happens reliably.

Suggested change

ipr = IPRoute()

ipr.bind()

fd = ipr.fileno()

global running

while running:

try:

# Wait for up to 1 second for a netlink message

rlist, _, _ = select.select([fd], [], [], 1.0)

if not rlist:

# timeout - retry

continue

# Receive and process any messages

for message in ipr.get():

event_type = message['event']

match event_type:

case 'RTM_NEWLINK':

attrs = dict(message.get('attrs', []))

iface = attrs.get('IFLA_IFNAME', '<unknown>')

operstate = attrs.get('IFLA_OPERSTATE', '<unknown>')

mac = attrs.get('IFLA_ADDRESS', '<unknown>')

syslog.syslog(syslog.LOG_INFO,

f'RTM_NEWLINK -> {iface}, state={operstate}, mac={mac}')

case 'RTM_DELLINK':

attrs = dict(message.get('attrs', []))

iface = attrs.get('IFLA_IFNAME', '<unknown>')

syslog.syslog(syslog.LOG_INFO, f'RTM_DELLINK -> {iface}')

case _:

syslog.syslog(syslog.LOG_INFO, f'Received event {event_type} - unhandled!')

except NetlinkError as e:

syslog.syslog(syslog.LOG_ERR, f'Netlink error: {e}')

except KeyboardInterrupt:

break

except Exception as e:

syslog.syslog(syslog.LOG_ERR, f'Unhandled exception: {e}')

ipr.close()

syslog.syslog(syslog.LOG_INFO, 'Netlink listener daemon stopped.')

exit(0)

ipr = None

try:

ipr = IPRoute()

ipr.bind()

fd = ipr.fileno()

global running

while running:

try:

# Wait for up to 1 second for a netlink message

rlist, _, _ = select.select([fd], [], [], 1.0)

if not rlist:

# timeout - retry

continue

# Receive and process any messages

for message in ipr.get():

event_type = message['event']

match event_type:

case 'RTM_NEWLINK':

attrs = dict(message.get('attrs', []))

iface = attrs.get('IFLA_IFNAME', '<unknown>')

operstate = attrs.get('IFLA_OPERSTATE', '<unknown>')

mac = attrs.get('IFLA_ADDRESS', '<unknown>')

syslog.syslog(syslog.LOG_INFO,

f'RTM_NEWLINK -> {iface}, state={operstate}, mac={mac}')

case 'RTM_DELLINK':

attrs = dict(message.get('attrs', []))

iface = attrs.get('IFLA_IFNAME', '<unknown>')

syslog.syslog(syslog.LOG_INFO, f'RTM_DELLINK -> {iface}')

case _:

syslog.syslog(syslog.LOG_INFO, f'Received event {event_type} - unhandled!')

except NetlinkError as e:

syslog.syslog(syslog.LOG_ERR, f'Netlink error: {e}')

except KeyboardInterrupt:

break

except Exception as e:

syslog.syslog(syslog.LOG_ERR, f'Unhandled exception: {e}')

finally:

if ipr is not None:

ipr.close()

syslog.syslog(syslog.LOG_INFO, 'Netlink listener daemon stopped.')

exit(0)

Copilot · 2025-11-28T12:35:52Z

src/services/vyos-netlinkd

+
+    ipr.close()
+    syslog.syslog(syslog.LOG_INFO, 'Netlink listener daemon stopped.')
+    exit(0)


Using exit(0) from the sys module is unnecessary here. The function can simply return, or use sys.exit(0) explicitly if needed. Since exit was imported from sys, this should be sys.exit(0) for clarity, or preferably just return from main().

Copilot · 2025-11-28T12:35:52Z

src/systemd/vyos-netlinkd.service

+
+[Service]
+ExecStart=/usr/bin/python3 -u /usr/libexec/vyos/services/vyos-netlinkd
+Type=idle


Type=idle is typically used for services that should run after all other jobs are dispatched. For a long-running daemon that listens for netlink events, Type=simple (the default) or Type=notify would be more appropriate. Type=idle may cause unnecessary delays in service startup.

Suggested change

Type=idle

Type=simple

c-po requested review from dmbaturin, jestabro, sever-sever and zdc November 26, 2025 21:43

github-actions bot added the current label Nov 26, 2025

github-actions bot assigned c-po Nov 26, 2025

c-po force-pushed the vyos-netlinkd branch from 9158ee1 to 7ad60db Compare November 27, 2025 07:12

sever-sever requested a review from Copilot November 28, 2025 12:33

Copilot started reviewing on behalf of sever-sever November 28, 2025 12:33 View session

sever-sever reviewed Nov 28, 2025

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Copilot finished reviewing on behalf of sever-sever November 28, 2025 12:35

Copilot AI reviewed Nov 28, 2025

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vyos-netlinkd: T8047: add proof-of-concept for a netlink listener daemon #4872

vyos-netlinkd: T8047: add proof-of-concept for a netlink listener daemon #4872

c-po commented Nov 26, 2025 •

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		syslog.syslog(syslog.LOG_INFO,
		f'RTM_NEWLINK -> {iface}, state={operstate}, mac={mac}')

vyos-netlinkd: T8047: add proof-of-concept for a netlink listener daemon #4872

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Change summary

Add example

Remove example

Types of changes

Related Task(s)

Related PR(s)

Checklist:

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