Bug#1040379: Bug in dhclient
Ralf Pichocki
Package: isc-dhcp-client
I am experiencing a strange behaviour, and this might be connected to the bug #595190 (isc-dhcp-client: goes into an infinite loop if server only answers on broadcast).
I am trying to debug two DHCP servers (one is on a Windows
Server 2012 R2, and the other one is dnsmasq on Ubuntu 22.04).
To check them both, I am using the option '-s
<address>", but this does not work correctly.
- dhclient sends a DHCPDISCOVER, and as the option suggests, it does not send this as a broadcast, but as a unicast to the server given in the option.
- Neither DHCP server, however, answers this with a DHCPOFFER, but both of them send a DHCPACK.
- So, it seems as if dhclient assumes to have sent a DHCPDISCOVER and thus waits for a DHCPOFFER - whereas the servers seem to interpret the package as a DHCPREQUEST and answer with DHCPACK.
- As this behaviour is identical on both DHCP servers, I dare to assume that this is an error in the package sent by dhclient.
- (Moreover, although I deleted the file /var/lib/dhcp/dhcp.leases, the dhclient somehow seems to remember its former lease address and inserts it into the DHCPDISCOVER package. Is that correct?)
- And worse, if I do not delete the old lease file, dhclient sends a DHCPREQUEST for its former address - which will can be acknowledged if the request is for an address issued from server A, and the request goes to server B... (but this might be by design)
I observe the behavior with dhclient
- sc-dhclient-4.4.3 on Linux Debian 12
- isc-dhclient-4.4.1 on Linux Mint 20.3 Una
- sc-dhclient-4.4.1 on LinuxUbuntu 20.04.5
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