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[WIP] Ensure VM IP is removed from VR DHCP records in dnsmasq.leases after expunge VM #13194

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[WIP] Ensure VM IP is removed from VR DHCP records in dnsmasq.leases after expunge VM #13194

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71 changes: 70 additions & 1 deletion systemvm/debian/opt/cloud/bin/cs/CsDhcp.py
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,10 @@
from netaddr import *
from random import randint
import json
import fcntl
import shutil
import tempfile
import signal
from .CsGuestNetwork import CsGuestNetwork
from cs.CsDatabag import CsDataBag
from cs.CsFile import CsFile
Expand Down Expand Up @@ -139,7 +143,8 @@ def configure_server(self):
# Listen Address
if self.cl.is_redundant():
listen_address.append(gateway)
listen_address.append(ip)
else:
listen_address.append(ip)
# Add localized "data-server" records in /etc/hosts for VPC routers
if self.config.is_vpc() or self.config.is_router():
self.add_host(gateway, "%s data-server" % CsHelper.get_hostname())
Expand All @@ -165,15 +170,79 @@ def delete_leases(self):
mac = lease[1]
ip = lease[2]
if mac not in macs_dhcphosts:
logging.info("Releasing DHCP lease for IP: %s, mac: %s", ip, mac)
cmd = "dhcp_release $(ip route get %s | grep eth | head -1 | awk '{print $3}') %s %s" % (ip, ip, mac)
logging.info(cmd)
CsHelper.execute(cmd)
if self.ensure_lease_removed(ip):
logging.info("Lease for %s still existed after dhcp_release; removed manually", ip)
removed = removed + 1
self.del_host(ip)
logging.info("Deleted %s entries from dnsmasq.leases file" % str(removed))
except Exception as e:
logging.error("Caught error while trying to delete entries from dnsmasq.leases file: %s" % e)

def lease_exists(self, ip):
if not os.path.exists(LEASES):
return False

with open(LEASES, "r") as fp:
for line in fp:
fields = line.split()
if len(fields) >= 3 and fields[2] == ip:
return True

return False

def remove_lease(self, ip):
if not os.path.exists(LEASES):
return False

removed = False

with open(LEASES, "r+") as fp:
fcntl.flock(fp.fileno(), fcntl.LOCK_EX)
lines = fp.readlines()

fd, tmp_path = tempfile.mkstemp(
prefix="dnsmasq.leases.",
dir=os.path.dirname(LEASES)
)

try:
with os.fdopen(fd, "w") as tmp:
for line in lines:
fields = line.split()

if len(fields) >= 3 and fields[2] == ip:
removed = True
continue

tmp.write(line)

if removed:
shutil.move(tmp_path, LEASES)

# reload dnsmasq
try:
with open("/var/run/dnsmasq.pid") as pidf:
os.kill(int(pidf.read().strip()), signal.SIGHUP)
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@weizhouapache weizhouapache May 20, 2026

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can use CsHelper.service("dnsmasq", "reload") ?

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@sureshanaparti sureshanaparti May 20, 2026

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ok, will check

except Exception:
pass

os.system("ip neigh flush all")
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@weizhouapache weizhouapache May 20, 2026

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what's the purpose of this ?

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@sureshanaparti sureshanaparti May 20, 2026 •
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@weizhouapache is it good to have this, to cleanup cache entries? will remove it if not necessary.

else:
os.remove(tmp_path)
finally:
fcntl.flock(fp.fileno(), fcntl.LOCK_UN)

return removed

def ensure_lease_removed(self, ip):
if self.lease_exists(ip):
return self.remove_lease(ip)
return False

def preseed(self):
self.add_host("127.0.0.1", "localhost")
self.add_host("127.0.1.1", "%s" % CsHelper.get_hostname())
Expand Down
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