Linux Networking – Troubleshoot Strange Temporary Network Outage

It is hard to give full details, especially not knowing what distribution you are using and how detailed you want the results to be - so I will just list some very basic examples.

If you are looking to get individual stats for each interface, we can break each item down separately (the following assumes root access on a distro like CentOS):

For bandwidth usage - I really like iftop. When you have iftop installed you could run the following command:

iftop -i eth0 -B

The -B option is for Bytes. Once inside iftop I like to press "T" to get a cummulative total.

For error rate you can easily see this in the output of ifconfig in your console. To get a more streamline approach you could run a very crude command like this (assuming something like Centos):

# ifconfig | grep -E "^\w|errors.* " | sed 's/pack.*errors:/Errors:/g' | sed 's/ drop.*//g' | sed 's/HW.*//g'
eth0      Link encap:Ethernet
          RX Errors:0
          TX Errors:0
eth1      Link encap:Ethernet
          RX Errors:3
          TX Errors:1
lo        Link encap:Local Loopback
          RX Errors:0
          TX Errors:0

This will give you the error count for each interface.

For collisions you can still use ifconfig. To get just the collision count, another basic command would be as follows:

# ifconfig | grep -E "^\w|collisions.* " | sed 's/pack.*collisions:/Collisions:/g' | sed 's/ txq.*//g' | sed 's/HW.*//g'
eth0      Link encap:Ethernet
          collisions:0
eth1      Link encap:Ethernet
          collisions:0
lo        Link encap:Local Loopback
          collisions:0

For dropped packets, still using ifconfig, you can run another simple command:

# ifconfig | grep -E "^\w|dropped.* " | sed 's/pack.*dropped:/Dropped:/g' | sed 's/ over.*//g' | sed 's/HW.*//g'
eth0      Link encap:Ethernet
          RX Dropped:0
          TX Dropped:0
eth1      Link encap:Ethernet
          RX Dropped:1
          TX Dropped:0
lo        Link encap:Local Loopback
          RX Dropped:0
          TX Dropped:0

If you are having a lot of bad packets (errors, collisions, or dropped), you could put the previous 3 commands into a bash script and use the watch command to monitor them:

FILE /tmp/netErrors:

#!/bin/sh

ifconfig | grep -E "^\w|errors.* " | sed 's/pack.*errors:/Errors:/g' | sed 's/ drop.*//g' | sed 's/HW.*//g'
echo
ifconfig | grep -E "^\w|collisions.* " | sed 's/pack.*collisions:/Collisions:/g' | sed 's/ txq.*//g' | sed 's/HW.*//g'
echo
ifconfig | grep -E "^\w|dropped.* " | sed 's/pack.*dropped:/Dropped:/g' | sed 's/ over.*//g' | sed 's/HW.*//g'
echo

COMMAND:

watch /tmp/netErrors

For QoS, it really depends on how you are setting it. For Linux, traffic control is common for setting QoS. To see the current QoS with traffic control you can run the following command:

# tc qdisc ls
qdisc pfifo_fast 0: dev eth0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev eth1 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev eth2 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
qdisc pfifo_fast 0: dev tun0 root refcnt 2 bands 3 priomap  1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1

tc - traffic control command qdisc - queuing disciplines ls - list

To get a good break down of traffic control you should check out the following link on traffic control.

According to the git commit history, the particular commit you identified as containing the fix you needed was merged to the mainline kernel in v3.13-rc1:

$ git describe --contains 68273712a19e9107a498a371532b3b3eb6dbb14c
v3.13-rc1~105^2~360

Unfortunately it seems unlikely that the particular patch would get included into older kernels in the stable development branch as that is generally only done to relatively small and critical fixes for security problems or significant regressions discovered in a given 3.x kernel.

That said, it isn't impossible that the fix would get picked up by distribution maintainers, or you could always apply the patch yourself and build your own kernel.

The Ubuntu kernel sources can be obtained by running:

git clone git://kernel.ubuntu.com/ubuntu/ubuntu-<release>.git

As a sidenote, you might want to install the linux-current-generic package instead of linux-generic-lts-raring as the former will on depend the most recently released generic kernel image and headers, up to 14.04 inclusive.