** Description changed:

  [impact]
  
  a systemd with a 64-character hostname (the maximum hostname length for
  Linux) will cause a dhcp server to reject its dhcp lease due to passing
  the invalid hostname in the dhcp lease request.
  
  [test case]
  
  $ cat /etc/systemd/network/10-ens3.network
  [Match]
  Name=ens3
  
  [Network]
  DHCP=yes
  
- 
  set hostname to 64-char name, e.g.:
  
  $ sudo hostnamectl set-hostname
  a123456789b123456789c123456789d123456789e123456789f123456789g123
  
  restart networkd:
  
  $ sudo systemctl restart systemd-networkd
  
  check logs:
  
  root@a123456789b123456789c123456789d123456789e123456789f123456789g123:~# 
journalctl -b -u systemd-networkd --no-pager | grep 'DHCP error'
  May 06 19:01:30 
a123456789b123456789c123456789d123456789e123456789f123456789g123 
systemd-networkd[737]: ens3: DHCP error: Client failed: Invalid argument
  
+ [regression potential]
+ 
+ Any regression would likely result in failure configuring/processing
+ dhcpv4 server response, or rejection from the dhcpv4 server.
+ 
  [scope]
  
  this is fixed by commit 9740eae694e93b06658ff3b3045b22b591561e7c which
  is included in Bionic and later.  This is needed only for Xenial.
  
  [other info]
  
  this is a follow on to bug 1862232, which corrected sd-dhcp-client.c to
  continue networkd dhcp even if the hostname is invalid, however the
  older code in Xenial doesn't correctly detect the invalid hostname, so
  this additional patch is needed.

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https://bugs.launchpad.net/bugs/1877176

Title:
  64-char hostname causes dhcp server to reject lease

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