Ethernet connection not working after installing Ubuntu 14.04 LTS

EDIT: PROBLEM IS BACK.. I cant figure out a permanent and reliable way around the bug (have managed the bug to go away 2 times) my files keep duplicating themselves with a ~ after their name, so if I modify rc.local, a file named rc.local~ pops out of nowhere, I dont understand what this does.

Also I dont have a /etc/init/module-init-tools.conf file, Im modifying the script in kmod.conf...

Help is appreciated.

EDIT: Problem solved thanks to https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1003297

I installed Ubuntu 14.04 LTS alongside Windows 7, my ethernet connection works without problem in Windows but it doesn’t work in Ubuntu. I think the problem is related to drivers and doesn’t allow me to aquire/assign an ip adress. Thank you for trying to help, Ill describe the problem ahead.

My wifi connection does work without problems. When I desable my wifi: my network manager tries to connect using the wired connection 1 and it always returns "Disconnected - you are now offline", and then it tries to connect again and the cycle repeats (Disconnected - yo are now offline).

Diagnosis info:

~$ lspci | grep Ethernet

00:07.0 Bridge: NVIDIA Corporation MCP61 Ethernet (rev a2)

~$ ifconfig

eth0
Link encap:Ethernet HWaddr bc:5f:f4:6f:26:c0
inet6 addr: fe80::be5f:f4ff:fe6f:26c0/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:12 dropped:0 overruns:11 frame:1 TX packets:140 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:27262 (27.2 KB)

lo
Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:1679 errors:0 dropped:0 overruns:0 frame:0 TX packets:1679 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:147779 (147.7 KB) TX bytes:147779 (147.7 KB)

About my ethernet controller: I dont understand much but here is the info I got:

~$ sudo lshw -class bridge

*-bridge description: Ethernet interface product: MCP61 Ethernet vendor: NVIDIA Corporation physical id: 7 bus info: pci@0000:00:07.0 logical name: eth0 version: a2 serial: bc:5f:f4:6f:26:c0 size: 100000000 capacity: 100000000 width: 32 bits clock: 66MHz capabilities: bridge pm msi ht bus_master cap_list ethernet physical mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation configuration: autonegotiation=on broadcast=yes driver=forcedeth driverversion=0.64 duplex=full latency=0 link=yes maxlatency=20 mingnt=1 multicast=yes port=MII speed=100Mbit/s resources: irq:44 memory:eeefd000-eeefdfff ioport:d080(size=8)

Finally I managed to get a script that diagnoses your connections, here is the output when my wifi is off and Im trying to connect trough my ethernet:

WARN: This system does not have a default route

INFO: Host localhost answers to ICMP pings

INFO: Loopback interface is working properly

INFO: The lo interface is up

INFO: The lo interface has IP address 127.0.0.1/8 ::1/128 assigned

INFO: The lo interface has tx and rx packets.

INFO: The eth0 interface is up INFO: The eth0 interface has IP address fe80::be5f:f4ff:fe6f:26c0/64 assigned ERR: The eth0 interface has not tx or rx any packets. Link down?

WARN: The eth0 interface has rx errors.

WARN: The wlan0 interface is down

ERR: The system does not have any nameserver configured

WARN: System does not seem to reach Internet host www.debian.org through ICMP WARN: Cannot access web server at Internet host www.debian.org

Thanks for reading and if you can help me out it will be greatly appreciated.

EDIT: $sudo lshw -class network

  *-network DISABLED      
   description: Wireless interface
   physical id: 1
   bus info: usb@1:4
   logical name: wlan0
   serial: 00:e0:4c:c0:c4:2c
   capabilities: ethernet physical wireless
   configuration: broadcast=yes driver=rtl8192cu driverversion=3.16.0-34-generic firmware=N/A link=no multicast=yes wireless=IEEE 802.11bgn

lsb_release -a

No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 14.04.2 LTS
Release:    14.04
Codename:   trusty

Note: I'm posting this workaround as an answer due to the number of times this has been reported as a bug only to expire shortly thereafter and resurface again.

Test

1. Enter Ubuntu recovery mode: a. Power on system and press Shift during boot up for GRUB menu.

   b. Choose "Advanced options for Ubuntu" > Ubuntu, [kernel version] (recovery mode)

2. Choose "root" and key in below commands:

   rmmod forcedeth
   modprobe forcedeth msi=0 msix=0
   exit
   

3. Choose "resume" to resume normal boot

Now the network should be OK till next boot with AM3+ CPU.

If the workaround works on your system, please modify below file to automatically run the script when boot up:

Bug Workaround Solution:

1. Add the line exec rmmod forcedeth at next line of "script" (above grep?) in the file /etc/init/module-init-tools.conf or /etc/init/kmod.conf)

2. Add the line modprobe forcedeth msi=0 msix=0 to /etc/rc.local

3. Restart the system to verify

Sources: Primarily Achkap post #16 http://ubuntuforums.org/showthread.php?t=2020571&page=2

https://bugs.launchpad.net/ubuntu/+s...x/+bug/1003297

https://bugs.launchpad.net/ubuntu/+bug/1264509

https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1281930

Clue from Julian Uribe in comments.