dnsmasq: Add full dhcp-host support for IPv4 and IPv6

[Monviech]

Fixes: #8487

Directive:
https://thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html

--dhcp-host=[<hwaddr>][,id:<client_id>|*][,set:<tag>][,tag:<tag>][,<ipaddr>][,<hostname>][,<lease_time>][,ignore]

This should almost fully satisfy the requirements of the man page regarding this directive.

Test dataset:

    <hosts uuid="9e5eb2a8-0ab2-4ed9-af5b-0c2787ddbfab">
      <host>hostabc</host>
      <domain>example.com</domain>
      <ip>172.16.1.200,fd12:3456:789a:1::2</ip>
      <client_id>*</client_id>
      <hwaddr>aa:aa:aa:aa:aa:aa,bb:bb:bb:bb:bb:bb</hwaddr>
      <lease_time/>
      <ignore>1</ignore>
      <set_tag/>
      <descr/>
      <comments/>
      <aliases>abc1.example.com,abc2.example.com</aliases>
    </hosts>
    <hosts uuid="883bd818-2885-443d-a699-90fb55fe3466">
      <host>hostd</host>
      <domain>example.com</domain>
      <ip>172.16.1.199,fd12:3456:789a:1::1</ip>
      <client_id>12121-3243242-222</client_id>
      <hwaddr/>
      <lease_time>4040</lease_time>
      <ignore>0</ignore>
      <set_tag>09e84129-c07b-4133-8251-f17c4d00f675</set_tag>
      <descr/>
      <comments/>
      <aliases>abc1.example.com,abc2.example.com</aliases>
    </hosts>
    <hosts uuid="af0c1d49-cc38-4468-9af4-61c31933dc79">
      <host>hostggg</host>
      <domain>example.com</domain>
      <ip>192.168.4.5</ip>
      <client_id/>
      <hwaddr/>
      <lease_time/>
      <ignore>0</ignore>
      <set_tag/>
      <descr/>
      <comments/>
      <aliases/>
    </hosts>
    <hosts uuid="04b21c12-6a51-4e45-b219-54b8052c9a17">
      <host>hostfff</host>
      <domain>example.com</domain>
      <ip>192.168.4.6</ip>
      <client_id/>
      <hwaddr>fe:fe:fe:fe:fe:fe</hwaddr>
      <lease_time/>
      <ignore>0</ignore>
      <set_tag/>
      <descr/>
      <comments/>
      <aliases/>
    </hosts>

Result:

/usr/local/etc/dnsmasq.conf

dhcp-host=id:*,aa:aa:aa:aa:aa:aa,bb:bb:bb:bb:bb:bb,172.16.1.200,[fd12:3456:789a:1::2],hostabc,86400,ignore
dhcp-host=id:12121-3243242-222,set:09e84129c07b41338251f17c4d00f675,172.16.1.199,[fd12:3456:789a:1::1],hostd,4040
dhcp-host=fe:fe:fe:fe:fe:fe,192.168.4.6,hostfff,86400

/var/etc/dnsmasq-hosts

172.16.1.200	hostabc.example.com hostabc
172.16.1.200	abc1.example.com
172.16.1.200	abc2.example.com
fd12:3456:789a:1::2	hostabc.example.com hostabc
fd12:3456:789a:1::2	abc1.example.com
fd12:3456:789a:1::2	abc2.example.com
172.16.1.199	hostd.example.com hostd
172.16.1.199	abc1.example.com
172.16.1.199	abc2.example.com
fd12:3456:789a:1::1	hostd.example.com hostd
fd12:3456:789a:1::1	abc1.example.com
fd12:3456:789a:1::1	abc2.example.com
192.168.4.5	hostggg.example.com hostggg
192.168.4.6	hostfff.example.com hostfff

[gspannu]

Fixes: #8487

Directive: https://thekelleys.org.uk/dnsmasq/docs/dnsmasq-man.html

This should almost fully satisfy the requirements of the man page regarding this directive.

First of all, thanks a ton for implementing this so quickly.

Quick question:
Can we safely assume that the implemented dhcp-host option for constructor style IPv6 will work as defined in the manpage?

---

_From the manpage.._

A single --dhcp-host may contain an IPv4 address or one or more IPv6 addresses, or both. IPv6 addresses must be bracketed by square brackets thus: --dhcp-host=laptop,[1234::56] IPv6 addresses may contain only the host-identifier part: --dhcp-host=laptop,[::56] in which case they act as wildcards in constructed DHCP ranges, with the appropriate network part inserted. For IPv6, an address may include a prefix length: --dhcp-host=laptop,[1234:50/126] which (in this case) specifies four addresses, 1234::50 to 1234::53. This (an the ability to specify multiple addresses) is useful when a host presents either a consistent name or hardware-ID, but varying DUIDs, since it allows dnsmasq to honour the static address allocation but assign a different adddress for each DUID.

[Monviech]

@gspannu As ::56 is a valid IPv6 address it can be input just fine. Just no prefix allowed right now, gotta input multiple addresses if you want multiple in the pool.

[fichtner]

Strictly speaking it’s a reserved/deprecated IPv6 range that doesn’t exist in the real world😉 https://www.iana.org/assignments/ipv6-address-space/ipv6-address-space.xhtml

[Monviech]

All dhcp-host entries must have only unique IP addresses. Otherwise dnsmasq has a hard error that prevents it to start.

I will add a draft for an additional validation that triggers when:

• An entry has either a client_id or hwaddr set, thus creating a dhcp-host
• The IP addresses of all of these entries are compared
• The validation triggers if the whole dhcp-host dataset is not unique IP wise.

dns overrides do not have to be unique, so the validation specifically targets only dhcp-host

[AdSchellevis]

@Monviech I've added 9a0f3c5, if you're ok with it, you can merge it.

[Monviech]

@AdSchellevis Just tested it and everything still works. So in it goes. Thank you for your help :)