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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Expunge vm not release in-memory dhcp record in vpc redundant virtual route correctly","articleBody":"### Environment\ncloudstack 4.19.1.2\n### Problem\nIn-memory record never released before next reboot of virtual router, finally run out of ip address, new vm can not get ip from dhcp.\n### Reproduce\n```\n1. Create vpc with redundant router and vm\n2. After vm success boot up, expunge it.\n3. Check `/var/lib/misc/dnsmasq.leases`, the vm record still there.\n```\n### Research\n1. 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 in virtual router vm\n2. 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\n\n```\n// dnsmasq v2.85 src\\rfc2131.c:1046\n    case DHCPRELEASE:\n      if (!(context = narrow_context(context, mess-\u003eciaddr, tagif_netid)) ||\n\t  !(opt = option_find(mess, sz, OPTION_SERVER_IDENTIFIER, INADDRSZ)) ||\n\t  option_addr(opt).s_addr != server_id(context, override, fallback).s_addr) \u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\n\treturn 0;\n\n```\n3. The address will not match because `dhcp_release` is requesting the primary address, and dnsmasq is listening the secondary address.\n```\n// /etc/dnsmasq.d/cloud.conf\ndhcp-hostsfile=/etc/dhcphosts.txt\nlisten-address=127.0.0.1,172.29.101.1           \u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\u003c\ndhcp-range=set:interface-eth3-1,172.29.101.1,static\ndhcp-option=tag:interface-eth3-1,15,cs2cloud.internal\ndhcp-option=tag:interface-eth3-1,6,172.29.101.1,10.1.2.146\ndhcp-option=tag:interface-eth3-1,3,172.29.101.1\ndhcp-option=eth3,26,1450\ndhcp-option=tag:interface-eth3-1,1,255.255.255.0\n```\n```\n// tcpdump view of packet emit by dhcp_release\n08:23:24.200332 lo    In  IP (tos 0x0, ttl 64, id 61594, offset 0, flags [DF], proto UDP (17), length 576)\n    172.29.101.245.57053 \u003e 172.29.101.245.67: [bad udp cksum 0x2663 -\u003e 0xd1aa!] BOOTP/DHCP, Request from 02:02:00:d4:00:51, length 548, Flags [none] (0x0000)\n          Client-IP 172.29.101.49\n          Client-Ethernet-Address 02:02:00:d4:00:51\n          Vendor-rfc1048 Extensions\n            Magic Cookie 0x63825363\n            DHCP-Message (53), length 1: Release\n            Server-ID (54), length 4: 172.29.101.245\n            END (255), length 0\n            PAD (0), length 0, occurs 298\n```\n```\n// ip addr show\n5: eth3: \u003cBROADCAST,MULTICAST,UP,LOWER_UP\u003e mtu 1450 qdisc pfifo_fast state UP group default qlen 1000\n    link/ether 02:02:00:d4:00:32 brd ff:ff:ff:ff:ff:ff\n    altname enp0s10\n    altname ens10\n    inet 172.29.101.245/24 brd 172.29.101.255 scope global eth3\n       valid_lft forever preferred_lft forever\n    inet 172.29.101.1/24 brd 172.29.101.255 scope global secondary eth3\n       valid_lft forever preferred_lft forever\n```\n\n### Workaround\nAdd both primary and secondary address to `cloud.conf` make it works.\n```\ndhcp-hostsfile=/etc/dhcphosts.txt\nlisten-address=127.0.0.1,172.29.101.1,172.29.101.245\n```\nOr patch `/opt/cloud/bin/cs/CsDhcp.py` in virtual router\n```\n            if self.cl.is_redundant():\n                listen_address.append(gateway)\n                listen_address.append(ip)                            # \u003c\u003c\u003c\u003c\u003c add this\n            else:\n                listen_address.append(ip)\n```","author":{"url":"https://github.com/hulucc","@type":"Person","name":"hulucc"},"datePublished":"2025-01-14T08:45:02.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/10182/cloudstack/issues/10182"}