On Mon, Apr 18, 2016 at 1:22 PM, Bjørn Mork <[email protected]> wrote: > Hans Dedecker <[email protected]> writes: > > On Sun, Apr 17, 2016 at 2:07 PM, Hauke Mehrtens <[email protected]> > wrote: > > > >> https://www.ietf.org/rfc/rfc2131.txt says in section 3.2 part 4.: > >> Note that in this case, where the client retains its network > >> address locally, the client will not normally relinquish its > >> lease during a graceful shutdown. Only in the case where the > >> client explicitly needs to relinquish its lease, e.g., the client > >> is about to be moved to a different subnet, will the client send > >> a DHCPRELEASE message. > >> > > It's a bit ambiguous to interprete (like so many statements in rfc2131 > :) ) > > as we don't keep the IP address locally when the udhcpc client is > shutdown. > > I don't read it as ambigious at all. > > RFC2131 clearly states that the client need not send DHCPRELEASE on > shutdown. The exact wording is (twice - both in section 3.1 and 3.2): > > The client may choose to relinquish its lease on a network address > by sending a DHCPRELEASE message to the server. > > The "may choose" is hard to interprete in any other way than being > entirely optional. There is nothing ambigious about that. > > So the question boils down to whether automatically sending DHCPRELEASE > is an advantage or not. I guess this might depend on your use case, but > IMHO it is definitely not. Why would anyone want their address to > change every time they reboot the system? They don't. > As you mention this depends on the use case and has to be seen in a more broader network scope; devices in networks which snoop DHCP messages can hold mac/IP address state info. If the IP address is not being used anymore by a gateway on a wan interface they want to be informed about this by a release message so the mac/IP address state can be removed.
> > I understand that there might be situations where you do want to send > DHCPRELEASE. But that is more suitable for an explicit command. It is > not something you want to do automatically without having precise > instructions to do so from the user. > > Please do not add this bug to the DHCP client. Thanks. > Making it configurable via UCI and keeping the default behavior will not introduce a bug Hans > > > > Bjørn >
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