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[Bug 906421] Re: [precise][regression] Shared to others -network disconnects immediately after connection established, then loop connect/disconnect

 

Yup,, IPv6 breaks ad-hoc for some reason. Marking Triaged and assigning,
this should at least be further fixed in gnome-control-center UI.

** Changed in: network-manager (Ubuntu)
       Status: New => Triaged

** Changed in: network-manager (Ubuntu)
   Importance: Undecided => High

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https://bugs.launchpad.net/bugs/906421

Title:
  [precise][regression] Shared to others -network disconnects
  immediately after connection established, then loop connect/disconnect

Status in “network-manager” package in Ubuntu:
  Triaged

Bug description:
  I have a computer attached to a 3G modem, and the eth0 device of that
  computer acts as a gateway for the local LAN, so that everybody can
  connect to the Internet via that computer. This was set up on Oneiric
  using Network Manager -> Wired connection -> IPv4 settings -> Shared
  to other computers. Everything worked flawlessly.

  Now I just installed Precise from scratch on the same computer and
  after setting up the wired connection as shared to others it fails to
  work properly. So there is regression from Oneiric to Precise.

  The interface gets set up correctly, and for a very short while others
  on the network can browse the Internet via the shared connection.
  However the network-manager of the sharing computer disconnects for an
  unknown reason after a short while.

  Then it starts looping, constantly connecting and two seconds later
  disconnecting, then connecting again etc.

  As the looping is ongoing, "nmcli con" shows output like this:

  otto@htpc:~$ nmcli con
  ** WARNING **: Error in getting active connection 'Vpn' property: (19) Method "Get" with signature "ss" on interface "org.freedesktop.DBus.Properties" doesn't exist
  ** WARNING **: _nm_object_array_demarshal: couldn't create object for /org/freedesktop/NetworkManager/ActiveConnection/70
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.00
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.12
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.24
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.24
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.28
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.28
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49
  otto@htpc:~$ nmcli con
  ** WARNING **: Error in getting active connection 'Vpn' property: (19) Method "Get" with signature "ss" on interface "org.freedesktop.DBus.Properties" doesn't exist
  ** WARNING **: _nm_object_array_demarshal: couldn't create object for /org/freedesktop/NetworkManager/ActiveConnection/78
  NAME                      UUID                                   TYPE              TIMESTAMP-REAL
  Shared wired connection   5cd2bb57-87d3-4946-9676-67ff51f52277   802-3-ethernet    la 17. joulukuuta 2011 21.17.32
  Dna Default               a767c3d1-66dc-4d8e-9c9b-482a1995e3c2   gsm               la 17. joulukuuta 2011 21.16.49

  As you can see, the 3G modem connection is stabil but the wired shared
  to other computer keeps resetting itself. I don't know if the DBus
  error has anything to do with this, maybe somebody can tell?

  Syslog shows output like this:
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) starting connection 'Shared wired connection'
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> (eth0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> (eth0): device state change: prepare -> config (reason 'none') [40 50 0]
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> (eth0): device state change: config -> ip-config (reason 'none') [50 70 0]
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) scheduled...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Beginning IP6 addrconf.
  Dec 18 19:36:10 htpc avahi-daemon[774]: Withdrawing address record for fe80::5604:a6ff:fe7f:31f4 on eth0.
  Dec 18 19:36:10 htpc avahi-daemon[774]: Leaving mDNS multicast group on interface eth0.IPv6 with address fe80::5604:a6ff:fe7f:31f4.
  Dec 18 19:36:10 htpc avahi-daemon[774]: Interface eth0.IPv6 no longer relevant for mDNS.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) started...
  Dec 18 19:36:10 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) started...
  Dec 18 19:36:10 htpc avahi-daemon[774]: Joining mDNS multicast group on interface eth0.IPv4 with address 10.42.43.1.
  Dec 18 19:36:10 htpc avahi-daemon[774]: New relevant interface eth0.IPv4 for mDNS.
  Dec 18 19:36:10 htpc avahi-daemon[774]: Registering new address record for 10.42.43.1 on eth0.IPv4.
  Dec 18 19:36:11 htpc kernel: [ 5890.285465] ip_tables: (C) 2000-2006 Netfilter Core Team
  Dec 18 19:36:11 htpc kernel: [ 5890.295553] nf_conntrack version 0.5.0 (16384 buckets, 65536 max)
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --insert POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Starting dnsmasq...
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> (eth0): device state change: ip-config -> activated (reason 'none') [70 100 0]
  Dec 18 19:36:11 htpc dnsmasq[1931]: started, version 2.59 cachesize 150
  Dec 18 19:36:11 htpc dnsmasq[1931]: compile time options: IPv6 GNU-getopt DBus i18n DHCP TFTP conntrack IDN
  Dec 18 19:36:11 htpc dnsmasq-dhcp[1931]: DHCP, IP range 10.42.43.10 -- 10.42.43.100, lease time 1h
  Dec 18 19:36:11 htpc dnsmasq[1931]: no servers found in /etc/resolv.conf, will retry
  Dec 18 19:36:11 htpc dnsmasq[1931]: cleared cache
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Activation (eth0) successful, device activated.
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) complete.
  Dec 18 19:36:11 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) complete.
  Dec 18 19:36:11 htpc dbus[761]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
  Dec 18 19:36:11 htpc dbus[761]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
  Dec 18 19:36:11 htpc avahi-daemon[774]: Joining mDNS multicast group on interface eth0.IPv6 with address fe80::5604:a6ff:fe7f:31f4.
  Dec 18 19:36:11 htpc avahi-daemon[774]: New relevant interface eth0.IPv6 for mDNS.
  Dec 18 19:36:11 htpc avahi-daemon[774]: Registering new address record for fe80::5604:a6ff:fe7f:31f4 on eth0.*.
  Dec 18 19:36:11 htpc ntpdate[1951]: Can't find host ntp.ubuntu.com: Name or service not known (-2)
  Dec 18 19:36:11 htpc ntpdate[1951]: no servers can be used, exiting
  Dec 18 19:36:20 htpc kernel: [ 5899.729375] eth0: no IPv6 routers present
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> (eth0): IP6 addrconf timed out or failed.
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP6 Configure Timeout) scheduled...
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP6 Configure Timeout) started...
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) started...
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --insert POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --insert POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Starting dnsmasq...
  Dec 18 19:36:30 htpc dnsmasq[1999]: started, version 2.59 cachesize 150
  Dec 18 19:36:30 htpc dnsmasq[1999]: compile time options: IPv6 GNU-getopt DBus i18n DHCP TFTP conntrack IDN
  Dec 18 19:36:30 htpc dnsmasq-dhcp[1999]: DHCP, IP range 10.42.43.10 -- 10.42.43.100, lease time 1h
  Dec 18 19:36:30 htpc dnsmasq[1999]: no servers found in /etc/resolv.conf, will retry
  Dec 18 19:36:30 htpc dnsmasq[1999]: cleared cache
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) complete.
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP6 Configure Timeout) complete.
  Dec 18 19:36:30 htpc NetworkManager[771]: <warn> dnsmasq died with signal 9
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> (eth0): device state change: activated -> failed (reason 'sharing-start-failed') [100 120 18]
  Dec 18 19:36:30 htpc NetworkManager[771]: <warn> Activation (eth0) failed.
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> (eth0): device state change: failed -> disconnected (reason 'none') [120 30 0]
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> (eth0): deactivating device (reason 'none') [0]
  Dec 18 19:36:30 htpc avahi-daemon[774]: Withdrawing address record for 10.42.43.1 on eth0.
  Dec 18 19:36:30 htpc dbus[761]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
  Dec 18 19:36:30 htpc avahi-daemon[774]: Leaving mDNS multicast group on interface eth0.IPv4 with address 10.42.43.1.
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --delete POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:36:30 htpc avahi-daemon[774]: Interface eth0.IPv4 no longer relevant for mDNS.
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc dbus[761]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --delete POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:36:30 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:37:11 htpc dnsmasq-dhcp[1999]: DHCP packet received on eth0 which has no address
  Dec 18 19:37:42  dnsmasq-dhcp[1999]: last message repeated 2 times
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) starting connection 'Shared wired connection'
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> (eth0): device state change: disconnected -> prepare (reason 'none') [30 40 0]
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) scheduled...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) started...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) scheduled...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 1 of 5 (Device Prepare) complete.
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) starting...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> (eth0): device state change: prepare -> config (reason 'none') [40 50 0]
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) successful.
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) scheduled.
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 2 of 5 (Device Configure) complete.
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) started...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> (eth0): device state change: config -> ip-config (reason 'none') [50 70 0]
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) scheduled...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 3 of 5 (IP Configure Start) complete.
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) started...
  Dec 18 19:38:18 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) started...
  Dec 18 19:38:18 htpc avahi-daemon[774]: Joining mDNS multicast group on interface eth0.IPv4 with address 10.42.43.1.
  Dec 18 19:38:18 htpc avahi-daemon[774]: New relevant interface eth0.IPv4 for mDNS.
  Dec 18 19:38:18 htpc avahi-daemon[774]: Registering new address record for 10.42.43.1 on eth0.IPv4.
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --insert FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --insert POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Starting dnsmasq...
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> (eth0): device state change: ip-config -> activated (reason 'none') [70 100 0]
  Dec 18 19:38:19 htpc dnsmasq[2065]: failed to create listening socket for 10.42.43.1: Address already in use
  Dec 18 19:38:19 htpc dnsmasq[2065]: FAILED to start up
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Activation (eth0) successful, device activated.
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Activation (eth0) Stage 5 of 5 (IP Configure Commit) complete.
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Activation (eth0) Stage 4 of 5 (IP4 Configure Get) complete.
  Dec 18 19:38:19 htpc NetworkManager[771]: <warn> dnsmasq exited with error: Network access problem (address in use; permissions; etc) (2)
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> (eth0): device state change: activated -> failed (reason 'sharing-start-failed') [100 120 18]
  Dec 18 19:38:19 htpc NetworkManager[771]: <warn> Activation (eth0) failed.
  Dec 18 19:38:19 htpc dbus[761]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> (eth0): device state change: failed -> disconnected (reason 'none') [120 30 0]
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> (eth0): deactivating device (reason 'none') [0]
  Dec 18 19:38:19 htpc avahi-daemon[774]: Withdrawing address record for 10.42.43.1 on eth0.
  Dec 18 19:38:19 htpc avahi-daemon[774]: Leaving mDNS multicast group on interface eth0.IPv4 with address 10.42.43.1.
  Dec 18 19:38:19 htpc avahi-daemon[774]: Interface eth0.IPv4 no longer relevant for mDNS.
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table nat --delete POSTROUTING --source 10.42.43.0/255.255.255.0 ! --destination 10.42.43.0/255.255.255.0 --jump MASQUERADE
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --destination 10.42.43.0/255.255.255.0 --out-interface eth0 --match state --state ESTABLISHED,RELATED --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --source 10.42.43.0/255.255.255.0 --in-interface eth0 --jump ACCEPT
  Dec 18 19:38:19 htpc dbus[761]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --out-interface eth0 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --out-interface eth0 --jump REJECT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete FORWARD --in-interface eth0 --jump REJECT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 67 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 67 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol udp --destination-port 53 --jump ACCEPT
  Dec 18 19:38:19 htpc NetworkManager[771]: <info> Executing: /sbin/iptables --table filter --delete INPUT --in-interface eth0 --protocol tcp --destination-port 53 --jump ACCEPT
  Dec 18 19:38:19 htpc ntpdate[2092]: Can't find host ntp.ubuntu.com: Name or service not known (-2)
  Dec 18 19:38:19 htpc ntpdate[2092]: no servers can be used, exiting
  Dec 18 19:38:35 htpc dnsmasq-dhcp[1999]: DHCP packet received on eth0 which has no address
  Dec 18 19:39:42  dnsmasq-dhcp[1999]: last message repeated 2 times

  From the log you can see that the connection is initially set up correctly at 19:36:11 and it works for 19 seconds until
   Dec 18 19:36:30 htpc NetworkManager[771]: <info> (eth0): IP6 addrconf timed out or failed.

  After that the network-manager disconnects. and later attempts to
  connect fails.

  I suspected there is some error with IPv6, so I changed for the wired
  connection settings in tab IPv6 to "none" and now the connection
  works. The default was "Automatic" which apparently is buggy.

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References