3acf1760b7
When dhclient first starts, if an old IP address exists in the dhclient.leases file, dhclient(8) sends early DHCPREQUEST message(s) in an attempt to re-obtain the old IP address again. These messages contain the old IP as a requested-IP-address option in the message body (correct) but also use the old IP address as the packet's source IP (incorrect). RFC2131 sec 4.1 states: DHCP messages broadcast by a client prior to that client obtaining its IP address must have the source address field in the IP header set to 0. The use of the old IP as the packet's source address is incorrect if (a) the computer is now on a different network or (b) it is on the same network, but the old IP has been reallocated to another host. Fix dhclient to use 0.0.0.0 as the source IP in this circumstance without removing any existing functionality. Any previously-used old IP is still requested in the body of an early DHCPREQUEST message. PR: 199378 Submitted by: J.R. Oldroyd <fbsd@opal.com> Reported by: J.R. Oldroyd <fbsd@opal.com> Reviewed by: cem, asomers, vangyzen MFC after: 1 week Sponsored by: Dell EMC Differential Revision: https://reviews.freebsd.org/D14527
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