[Bug 1662814] Re: dhclient doesn't honor metric setting in network interfaces on ubuntu 16.04

[Launchpad Bug Tracker]

Status changed to 'Confirmed' because the bug affects multiple users.

** Changed in: isc-dhcp (Ubuntu)
       Status: New => Confirmed

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Title:
  dhclient doesn't honor metric setting in network interfaces on ubuntu
  16.04

Status in isc-dhcp package in Ubuntu:
  Confirmed

Bug description:
  $ cat /etc/lsb-release 
  DISTRIB_ID=Ubuntu
  DISTRIB_RELEASE=16.04
  DISTRIB_CODENAME=xenial
  DISTRIB_DESCRIPTION="Ubuntu 16.04.1 LTS"

  $ dpkg-query -l isc-dhcp-client
  Desired=Unknown/Install/Remove/Purge/Hold
  | Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
  |/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
  ||/ Name                                                             Version                               Architecture                          Description
  +++-================================================================-=====================================-=====================================-======================================================================================================================================
  ii  isc-dhcp-client                                                  4.3.3-5ubuntu12.6                     amd64                                 DHCP client for automatically obtaining an IP address

  # configure metric in network interface
  $ cat /etc/network/interfaces.d/ens4.cfg 
  auto ens4
  iface ens4 inet dhcp
    metric 1000

  # dhclient set IF_METRIC=1000 environment variable for ens4
  $ ps xau|egrep -i 'dhclient'
  root     27906  0.0  0.0  16120   864 ?        Ss   08:35   0:00 /sbin/dhclient -1 -v -pf /run/dhclient.ens3.pid -lf /var/lib/dhcp/dhclient.ens3.leases -I -df /var/lib/dhcp/dhclient6.ens3.leases ens3
  root     28392  0.0  0.0  16120   868 ?        Ss   08:59   0:00 /sbin/dhclient -1 -v -pf /run/dhclient.ens4.pid -lf /var/lib/dhcp/dhclient.ens4.leases -I -df /var/lib/dhcp/dhclient6.ens4.leases ens4 -e IF_METRIC=1000

  $ route -nee
  Kernel IP routing table
  Destination     Gateway         Genmask         Flags Metric Ref    Use Iface    MSS   Window irtt
  0.0.0.0         xxx.xxx.xxx.xxx 0.0.0.0         UG    0      0        0 ens3     0     0      0
  xxx.xxx.xxx.xxx 0.0.0.0         255.255.255.192 U     0      0        0 ens3     0     0      0
  172.16.0.0      192.168.12.1    255.240.0.0     UG    0      0        0 ens4     0     0      0
  192.168.0.0     192.168.12.1    255.255.0.0     UG    0      0        0 ens4     0     0      0
  192.168.12.0    0.0.0.0         255.255.255.0   U     0      0        0 ens4     0     0      0

  After ifdown ens4, ifup ens4, dhclient doens't configure metric for
  ens4 routes.

  below patch fix this issue.

  --- /etc/dhcp/dhclient-exit-hooks.d/rfc3442-classless-routes    2017-02-08 08:59:16.407956495 +0000
  +++ ./rfc3442-classless-routes  2017-02-08 08:58:58.328337696 +0000
  @@ -71,7 +71,7 @@
   
                                  # set route (ip detects host routes automatically)
                                  ip -4 route add "${net_address}/${net_length}" \
  -                                       ${via_arg} dev "${interface}" >/dev/null 2>&1
  +                                       ${via_arg} dev "${interface}" ${IF_METRIC:+metric $IF_METRIC} >/dev/null 2>&1
                          done
                  fi
          fi

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