On Saturday 02 June 2018 16:25:51 Pali Rohár wrote: > On Saturday 02 June 2018 15:48:58 Pali Rohár wrote: > > On Tuesday 23 May 2017 09:39:11 Pali Rohár wrote: > > > On Monday 22 May 2017 23:11:02 Simon Kelley wrote: > > > > On 12/05/17 16:32, Pali Rohár wrote: > > > > > On Friday 12 May 2017 17:15:20 Simon Kelley wrote: > > > > >> There are so many layers of quotes here that I've completely lost > > > > >> track of what we were trying to achieve, and how to achieve it. My > > > > >> memory is that we'd failed to come up with any consensus on either > > > > >> of those. > > > > > > > > > > Goal 1: > > > > > > > > > > Ability to assign one IPv4 address to two different MAC addresses. > > > > > Currently it is possible by misusing concept of "more mac addresses" > > > > > (where IPv4 address can be "steal" by later DHCP client). > > > > > > > > > > Goal 2: > > > > > > > > > > Achieve Goal 1 also for DHCPv6. > > > > > > > > > >> Using MAC addresses with DHCPv6 AT ALL is quite difficult - it's not > > > > >> a concept that the RFCs deal with. > > > > > > > > > > I read DHCPv6 RFC and it does not refuse assigning IPv6 address based > > > > > on > > > > > link layer MAC address. Anyway, this is already supported by dnsmasq. > > > > > > > > > > But what I want to achieve has ability to assign one IPv6 address to > > > > > more MAC addresses at same time. This DHCPv6 RFC does not allow, but > > > > > in > > > > > some situations it is useful and I think such options could be > > > > > provided > > > > > by DHCPv6 server with explicit warning in documentation. > > > > > > > > > >> Doing the sleight-of-hand trick > > > > >> that works with DHCPv4 doesn't seem feasible to me for DHCPv6. > > > > > > > > > > Do you completely disagree with fact that dnsmasq could support this > > > > > scenario for assigning one IP address to more network cards > > > > > (identified > > > > > by MAC address)? Or you just do not like my current implementation? > > > > > > > > The whole point of DHCP is to avoid an IP address being used by more > > > > than one network card. The current two-MAC addresses for one IP facility > > > > in DHCPv4 doesn't contradict this. It's specified to be used only when > > > > there's a guarantee that both MAC address are never simultaneously in > > > > use. > > > > > > I know. But as I wrote, lot of people misuse this feature to assign one > > > IPv4 address to more network cards. As there is use case for such state > > > and dnsmasq can do it. > > > > > > So instead of misusing that feature I'm asking how to implement it > > > properly. > > > > Hi Simon! > > > > Do you have any opinion about this? Or do you fully disagree and such > > feature should not be in dnsmasq? > > > > > > Cheers, > > > > > > > > Simon. > > > > > > > > > > > > > > > > > > In previous email I wrote that Goal 2 can be achieved by storing > > > > > tuple > > > > > DUID, IAID, MAC address and IPv6 address into DHCPv6 leases file. > > > > > > > > > > > > In IPv6 it is a more complicated, e.g. when network administrator wants > > to assign one IPv6 address for specific computer. > > > > Imagine that you have one computer with more OS (dua-boot) and each OS > > has its own DUID and IAID (MAC address is stable). > > > > Problem: dnsmasq assign IPv6 address to that computer when OS1 is > > running. Computer is then rebooted to OS2 which has different DUID and > > IAID. Therefore dnsmasq assigns a new (different) IPv6, because old one > > is still "used" in server lease file. > > > > To "solve" this problem it is either needed to extend dnsmasq to allow > > assigning one IPv6 address to more DUIDs/IAIDs. > > > > Or to assign IPv6 addresses based on MAC address and then dnsmasq leases > > file needs to be extended to included also MAC address for IPv6 > > addresses. > > Currently in lease file for DHCPv6 records there is line: > > expire_time iaid ipv6_addr hostname duid > > and for DHCPv4 is: > > expire_time mac ipv4_addr hostname clid > > To have similar format DHCPv6 records as DHCPv4 could be changed and > extended for mac address to: > > expire_time mac ipv6_addr hostname duid iaid > > Or to have iaid on same position, to: > > expire_time iaid ipv6_addr hostname duid mac > > And then allow assigning IPv6 address for IAID and correctly from lease > file for IPv6 address takes value relevant for configuration. E.g. when > IPv6 address is assigned based on MAC address, took mac. When is > assigned for DUID, then duid. And when iaid, then IAID. > > So when configured this would allow "stealing" IPv6 address when there > is one computer which uses two different DHPv6 clients with different > DUIDs or IAIDs. (E.g. dual-boot Linux-Windows setup). > > > Also this extended information in lease file could allow to implement > that assigning one IPv6 address to more MAC addresses properly as in > lease file would be all relevant information about dhcp client.
Hi Simon! Have you looked at above proposal for extending lease file for IPv6 addresses? -- Pali Rohár pali.ro...@gmail.com
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