CVSROOT: /cvs
Module name: src
Changes by: [email protected] 2024/02/13 05:53:05
Modified files:
sbin/dhcpleased: engine.c
Log message:
Only generate a new xid at the start of getting a new lease.
"RFC 2131 4.1 Constructing and sending DHCP messages" has this:
| Selecting a new 'xid' for each retransmission is an implementation
| decision. A client may choose to reuse the same 'xid' or select a new
| 'xid' for each retransmitted message.
We used to change xid for each request / response cycle but this ran
into problems with slow dhcp servers where we would change the xid too
frequently and would ignore late coming replies from the server.
Andre S points out that table 5 in "4.4.1 Initialization and
allocation of network address" says for the xid field in "DHCPREQUEST"
messages:
| 'xid' from server DHCPOFFER message
This seems to suggest that we need to use the same xid for the whole
DHCPDISCOVER / DHCPOFFER / DHCPREQUEST / DHCPACK exchange of messages.
Nothing else in the RFC is saying this though.
But since there are DHCP servers out there that depend on this, we
only generate a new xid when entering the INIT, REBOOTING and RENEWING
state.
I do wonder if we should just go with a static value of 0x04, which
was chosen by a fair dice roll, so guaranteed to be random.
Issue reported, initial diff and fix tested by Andre S
deraadt likes this version
OK tb
