This is another take on a recurring problem. There is a facility to work
around it by allowing multiple addresses to be specified in dhcp-host.
That works for the specific case of chain-netbooting, where the host's
DUID changes at each stage of the boot. I appreciate that may not be the
problem you are solving.
This patch works by confusing a dhcp-host declaration with a DHCPv6
lease. They are not the same thing. For instance it's possible to have
more than on dhcp-host bound to the same DUID or MAC address or
hostname, but on different subnets. I think it may be better to not use
dhcp-host at all, but to just work with dhcp leases. Even DHCPv6 leases
store the MAC address if it's known, so the RFC3315-violating behaviour
could be:
if (a lease exists for the MAC address, but with different (DUID,IAID))
then delete the lease and free the associated address.
There's a slight problem that MAC addresses do not get written to the
persistent lease file for DHCPv6 leases, but that could be solved in a
backwards compatible way fairly easily.
TL;DR I'm in favour of fixing this problem, but the current approach
seems wrong; I can't convince myself that there won't be undesireable
consequences.
Cheers,
Simon.
On 21/03/2022 07:55, renmingshuai via Dnsmasq-discuss wrote:
In some cases, such as system reinstallation, the duid of the client has
changed when the client renews the lease. dnamsq will assign a new lease
back to the client if the new lease is available. However, if the old
lease of the client is not released or the client cannot actively
release the old lease for some reasons, the client cannot obtain for a
new lease until the old lease expires when dnsmasq has no free lease.
Although both duid and MAC addresses are used to identify clients, can
dnsmasq consider providing the new switch --bind-mac-with-ipv6 for users
to choose to forcibly remove clients marked with DUID or not. When
dnsmasq starts with --bind-mac-with-ipv6, it will assign the lease whose
mac address is same with the client's to the client , even if that lease
has a different duid than the client's.
See attachment for patch.
cheers,
mingshuai
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