[Bug 16174] New: udhcpc: DHCP Release is not sent if ARP resolution is needed

[bugzilla at busybox.net]

https://bugs.busybox.net/show_bug.cgi?id=16174

            Bug ID: 16174
           Summary: udhcpc: DHCP Release is not sent if ARP resolution is
                    needed
           Product: Busybox
           Version: 1.36.x
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: minor
          Priority: P5
         Component: Networking
          Assignee: unassigned at busybox.net
          Reporter: jocrismachado at gmail.com
                CC: busybox-cvs at busybox.net
  Target Milestone: ---

Environment:

    BusyBox v1.36.1 (2024-06-10 15:30:53 UTC) multi-call binary
    Docker container "Alpine Linux edge" 3.21.0_alpha20240807
    macvlan interface on a non-default namespace
    linux kernel 5.14.0-362.18.1.el9_3.0.1.x86_64

Problem
Upon receiving USR2 signal, if ARP resolution is required for the next-hop
towards DHCP Server, then DHCP Release is not generated.

I see ARP request-reply right after USR2 signal, therefore I suspect it's
attempting to send the release message but is removing the IP address too
quickly from the interface, and by the time ARP resolution completes there is
no IP address available to source the DHCP Release packet.

---------------------
/ # kill -USR2 24426
/ # udhcpc: unicasting a release of 10.112.240.141 to 10.223.255.118
udhcpc: sending release
udhcpc: entering released state

#tcpdump output
11:12:17.052045 ARP, Request who-has 10.112.192.1 tell 10.112.240.141, length
28
11:12:17.081806 ARP, Reply 10.112.192.1 is-at 00:00:5e:00:01:7e, length 46

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