From 3649dd09743e47700d36ecd25bffcd77dbb3cc3f Mon Sep 17 00:00:00 2001 From: Robert Navarro Date: Sun, 31 May 2026 13:34:09 -0700 Subject: vyos-netlinkd: T8950: track per-interface operstate to suppress UP-to-UP DHCP restarts _handle_dhcp_events() restarts dhclient/dhcp6c on every RTM_NEWLINK that carries operstate=UP, regardless of whether the interface was already UP. Normal kernel events that re-notify UP without a preceding DOWN (e.g. post-migration gratuitous-ARP, promiscuous-mode toggles) trigger unnecessary DHCP restarts. Each restart also creates a feedback loop: dhclient-script runs "ip link set dev up" during PREINIT, which emits another RTM_NEWLINK(UP), which triggers another restart. One seed event becomes 10+ restarts in 15 seconds. Add a module-level dict tracking the last observed operstate per interface. Only proceed with the DHCP restart when the transition is DOWN-to-UP or when no previous state is recorded (first boot / service restart). UP-to-UP re-notifications are suppressed with a LOG_DEBUG message. Validated on a production VyOS 2026.05.26-1327-rolling router: a controlled KVM live migration after the patch produced zero DHCP restarts (all UP-to-UP events suppressed), with no impact on normal DOWN-to-UP DHCP recovery. --- src/services/vyos-netlinkd | 17 ++++++++++++++++- 1 file changed, 16 insertions(+), 1 deletion(-) (limited to 'src') diff --git a/src/services/vyos-netlinkd b/src/services/vyos-netlinkd index 2b158e05d..0e7da7a59 100755 --- a/src/services/vyos-netlinkd +++ b/src/services/vyos-netlinkd @@ -40,6 +40,10 @@ running = True # compile regex once during startup for fast match IFACE_RE = re.compile(r"^(?:eth|br|bond|wlan)") +# Per-interface previous operstate, used to suppress DHCP restarts on +# UP-to-UP re-notifications (e.g. post-migration gratuitous-ARP events). +_iface_prev_operstate: dict[str, str] = {} + def match_iface(ifname: str) -> bool: """ Helper function returning true if interface name is a match for further processing (e.g. restart of DHCP(v6) client) @@ -60,6 +64,14 @@ def _handle_dhcp_events(operstate: Optional[str], ifname: str) -> None: if operstate not in ['UP', 'DOWN']: return None + prev = _iface_prev_operstate.get(ifname) + _iface_prev_operstate[ifname] = operstate + + if operstate == 'UP' and prev == 'UP': + syslog.syslog(syslog.LOG_DEBUG, + f'Suppressing DHCP restart for {ifname}: already UP') + return None + if operstate == 'DOWN': # Interface moved state to down if is_systemd_service_active(systemdV4_service): @@ -168,7 +180,10 @@ def main(): # Deletion of a network link which has been previously added to the kernel case 'RTM_DELLINK': - pass + attrs = dict(message.get('attrs', [])) + ifname = attrs.get('IFLA_IFNAME', None) + if ifname: + _iface_prev_operstate.pop(ifname, None) case _: pass -- cgit v1.2.3