hulucc opened a new issue, #10182:
URL: https://github.com/apache/cloudstack/issues/10182
### Environment
cloudstack 4.19.1.2
### Reproduce
```
1. create vpc and vm
2. expunge vm
3. check `/var/lib/misc/dnsmasq.leases`, the vm record still there.
```
### Research
1. When expunging vm, cloudstack will call shell command like `dhcp_release
eth3 172.29.101.250 02:02:00:d4:00:4f` try to release in-memory dhcp record in
dnsmasq
2. the `dhcp_release` command will actually do nothing, because dnsmasq will
check the server address in config is matching the request address. check the
dnsmasq source code below
```
// dnsmasq v2.85 src\rfc2131.c:1046
case DHCPRELEASE:
if (!(context = narrow_context(context, mess->ciaddr, tagif_netid)) ||
!(opt = option_find(mess, sz, OPTION_SERVER_IDENTIFIER, INADDRSZ)) ||
option_addr(opt).s_addr != server_id(context, override,
fallback).s_addr) <<<<<<<<<<
return 0;
```
3. The address will not match because `dhcp_release` is requesting the
primary address, and dnsmasq is listening the secondary address.
```
// /etc/dnsmasq.d/cloud.conf
dhcp-hostsfile=/etc/dhcphosts.txt
listen-address=127.0.0.1,172.29.101.1 <<<<<<<<<<<<<<<
dhcp-range=set:interface-eth3-1,172.29.101.1,static
dhcp-option=tag:interface-eth3-1,15,cs2cloud.internal
dhcp-option=tag:interface-eth3-1,6,172.29.101.1,10.1.2.146
dhcp-option=tag:interface-eth3-1,3,172.29.101.1
dhcp-option=eth3,26,1450
dhcp-option=tag:interface-eth3-1,1,255.255.255.0
```
```
// tcpdump view of packet emit by dhcp_release
08:23:24.200332 lo In IP (tos 0x0, ttl 64, id 61594, offset 0, flags
[DF], proto UDP (17), length 576)
172.29.101.245.57053 > 172.29.101.245.67: [bad udp cksum 0x2663 ->
0xd1aa!] BOOTP/DHCP, Request from 02:02:00:d4:00:51, length 548, Flags [none]
(0x0000)
Client-IP 172.29.101.49
Client-Ethernet-Address 02:02:00:d4:00:51
Vendor-rfc1048 Extensions
Magic Cookie 0x63825363
DHCP-Message (53), length 1: Release
Server-ID (54), length 4: 172.29.101.245
END (255), length 0
PAD (0), length 0, occurs 298
```
```
// ip addr show
5: eth3: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 qdisc pfifo_fast state
UP group default qlen 1000
link/ether 02:02:00:d4:00:32 brd ff:ff:ff:ff:ff:ff
altname enp0s10
altname ens10
inet 172.29.101.245/24 brd 172.29.101.255 scope global eth3
valid_lft forever preferred_lft forever
inet 172.29.101.1/24 brd 172.29.101.255 scope global secondary eth3
valid_lft forever preferred_lft forever
```
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