[Bug 1882317] [NEW] Dual Stack DHCP clobber each other when using /run/dhcp-server/ for pid files

[Joshua Stark]

Public bug reported:

When installing dual stack IPv4 and IPv6 DHCP I found that DHCPv4 and
DHCPv6 clobber each others /run/dhcp-server path when you stop or
restart one of the daemons

I found that the config in the systemd unit has the /run path set to the
same location for both DHCPv4 and DHCPv6

In /lib/systemd/system/isc-dhcp-server.service the offending line that conflicts is:
  exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES'

In /lib/systemd/system/isc-dhcp-server6.service the offending line that conflicts is:
  exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'

This means if you stop/restart DHCPv4 or DHCPv6, then it cleans up the
path /run/dhcp-server and removed the pid file for the alternate
process.

I have found a possible fix is to give DHCPv6 it's own /run path, thus I
suggest:

1) update DHCPv6 to use /run/dhcp-server6/

Update /lib/systemd/system/isc-dhcp-server6.service to use /run/dhcp-server6/
ie.
  exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server6/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'

Now we need to give dhcp access to this path in Apparmor:

2) Update /etc/apparmor.d/usr.sbin.dhcpd and add an additional line

38d39
  /var/lib/dhcp/dhcpd{,6}.leases* lrw,
  /var/log/ r,
  /var/log/** rw,
  /{,var/}run/{,dhcp-server/}dhcpd{,6}.pid rw,
+  /{,var/}run/{,dhcp-server6/}dhcpd{,6}.pid rw,

Found in package version:
  4.4.1-2ubuntu5

** Affects: isc-dhcp (Ubuntu)
     Importance: Undecided
         Status: New

** Description changed:

  When installing dual stack IPv4 and IPv6 DHCP I found that DHCPv4 and
  DHCPv6 clobber each others /run/dhcp-server path when you stop or
  restart one of the daemons
  
  I found that the config in the systemd unit has the /run path set to the
  same location for both DHCPv4 and DHCPv6
  
- 
  In /lib/systemd/system/isc-dhcp-server.service the offending line that conflicts is:
-   exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES'
- 
+   exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES'
  
  In /lib/systemd/system/isc-dhcp-server6.service the offending line that conflicts is:
-   exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'
+   exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'
  
- 
- This means if you stop/restart DHCPv4 or DHCPv6, then it cleans up the path /run/dhcp-server and removed the pid file for the alternate process.
+ This means if you stop/restart DHCPv4 or DHCPv6, then it cleans up the
+ path /run/dhcp-server and removed the pid file for the alternate
+ process.
  
  I have found a possible fix is to give DHCPv6 it's own /run path, thus I
  suggest:
  
  1) update DHCPv6 to use /run/dhcp-server6/
  
  Update /lib/systemd/system/isc-dhcp-server6.service to use /run/dhcp-server6/
  ie.
-   exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server6/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'
+   exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server6/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'
  
  Now we need to give dhcp access to this path in Apparmor:
  
  2) Update /etc/apparmor.d/usr.sbin.dhcpd and add an additional line
  
  38d39
-   /var/lib/dhcp/dhcpd{,6}.leases* lrw,
-   /var/log/ r,
-   /var/log/** rw,
-   /{,var/}run/{,dhcp-server/}dhcpd{,6}.pid rw,
+   /var/lib/dhcp/dhcpd{,6}.leases* lrw,
+   /var/log/ r,
+   /var/log/** rw,
+   /{,var/}run/{,dhcp-server/}dhcpd{,6}.pid rw,
  +  /{,var/}run/{,dhcp-server6/}dhcpd{,6}.pid rw,
+ 
+ Found in package version:
+   4.4.1-2ubuntu5

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https://bugs.launchpad.net/bugs/1882317

Title:
  Dual Stack DHCP clobber each other when using /run/dhcp-server/ for
  pid files

Status in isc-dhcp package in Ubuntu:
  New

Bug description:
  When installing dual stack IPv4 and IPv6 DHCP I found that DHCPv4 and
  DHCPv6 clobber each others /run/dhcp-server path when you stop or
  restart one of the daemons

  I found that the config in the systemd unit has the /run path set to
  the same location for both DHCPv4 and DHCPv6

  In /lib/systemd/system/isc-dhcp-server.service the offending line that conflicts is:
    exec dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf $CONFIG_FILE $INTERFACES'

  In /lib/systemd/system/isc-dhcp-server6.service the offending line that conflicts is:
    exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'

  This means if you stop/restart DHCPv4 or DHCPv6, then it cleans up the
  path /run/dhcp-server and removed the pid file for the alternate
  process.

  I have found a possible fix is to give DHCPv6 it's own /run path, thus
  I suggest:

  1) update DHCPv6 to use /run/dhcp-server6/

  Update /lib/systemd/system/isc-dhcp-server6.service to use /run/dhcp-server6/
  ie.
    exec dhcpd -user dhcpd -group dhcpd -f -6 -pf /run/dhcp-server6/dhcpd6.pid -cf $CONFIG_FILE $INTERFACES'

  Now we need to give dhcp access to this path in Apparmor:

  2) Update /etc/apparmor.d/usr.sbin.dhcpd and add an additional line

  38d39
    /var/lib/dhcp/dhcpd{,6}.leases* lrw,
    /var/log/ r,
    /var/log/** rw,
    /{,var/}run/{,dhcp-server/}dhcpd{,6}.pid rw,
  +  /{,var/}run/{,dhcp-server6/}dhcpd{,6}.pid rw,

  Found in package version:
    4.4.1-2ubuntu5

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