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