Comment 21 for bug 1872118

As my systems are pinned not to accept isc-dhcp-server upgrades, as I run the 18.04 version as it works. I extracted the dhcpd file from your packages and dropped it in place.
It ran for about 5 hours with thousands of requests.
Then it crashed with

Aug 4 13:13:29 gw2-focal sh[63448]: ../../../../lib/isc/unix/socket.c:3361: INSIST(!sock->pending_send) failed, back trace
Aug 4 13:13:29 gw2-focal sh[63448]: #0 0x7f0ed6a02a4a in ??
Aug 4 13:13:29 gw2-focal sh[63448]: #1 0x7f0ed6a02980 in ??
Aug 4 13:13:29 gw2-focal sh[63448]: #2 0x7f0ed6a3e7e1 in ??
Aug 4 13:13:29 gw2-focal sh[63448]: #3 0x7f0ed67e5609 in ??
Aug 4 13:13:29 gw2-focal sh[63448]: #4 0x7f0ed6921103 in ??

In the syslog

The start of the crash (up to the base64 dump) is

ProblemType: Crash
Architecture: amd64
Date: Tue Aug 4 13:13:30 2020
DistroRelease: Ubuntu 20.04
ExecutablePath: /usr/sbin/dhcpd
ExecutableTimestamp: 1596530249
ProcCmdline: dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf
ProcEnviron: Error: [Errno 13] Permission denied: 'environ'
ProcMaps: Error: [Errno 13] Permission denied: 'maps'
ProcStatus:
 Name: dhcpd
 Umask: 0022
 State: D (disk sleep)
 Tgid: 63448
 Ngid: 0
 Pid: 63448
 PPid: 1
 TracerPid: 0
 Uid: 113 113 113 113
 Gid: 118 118 118 118
 FDSize: 128
 Groups:
 NStgid: 63448
 NSpid: 63448
 NSpgid: 63448
 NSsid: 63448
 VmPeak: 235996 kB
 VmSize: 170540 kB
 VmLck: 0 kB
 VmPin: 0 kB
 VmHWM: 12468 kB
 VmRSS: 12468 kB
 RssAnon: 6216 kB
 RssFile: 6252 kB
 RssShmem: 0 kB
 VmData: 30872 kB
 VmStk: 132 kB
 VmExe: 592 kB
 VmLib: 5424 kB
 VmPTE: 88 kB
 VmSwap: 0 kB
 HugetlbPages: 0 kB
 CoreDumping: 1
 THP_enabled: 1
 Threads: 4
 SigQ: 0/31897
 SigPnd: 0000000000000000
 ShdPnd: 0000000000000000
 SigBlk: 0000000000000000
 SigIgn: 0000000000001000
 SigCgt: 0000000180000000
 CapInh: 0000000000000000
 CapPrm: 0000000000000000
 CapEff: 0000000000000000
 CapBnd: 0000003fffffffff
 CapAmb: 0000000000000000
 NoNewPrivs: 0
 Seccomp: 0
 Speculation_Store_Bypass: thread vulnerable
 Cpus_allowed: f
 Cpus_allowed_list: 0-3
 Mems_allowed: 00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,0000
0000,00000000,00000000,00000001
 Mems_allowed_list: 0
 voluntary_ctxt_switches: 40
 nonvoluntary_ctxt_switches: 19
Signal: 6
Uname: Linux 5.4.0-42-generic x86_64
UserGroups: N/A