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Ethernet CRC errors statistics in Linux

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Kushal Koolwal

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Oct 19, 2009, 3:40:02 AM10/19/09
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I have a system (x86_64) running Debian Lenny on a standard Gigabit Ethernet LAN. I have been doing some researching on how to measure Ethernet CRC errors (Physical layer), if there are any, on my Debian system's ethernet card . It is clear that the ethereal (now wireshark) cannot measure it [1]. Some people have suggested to use the following commands to get the CRC count:

# cat /proc/net/dev
Inter-|   Receive                                                |  Transmit
 face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
    lo: 1230934    5159    0    0    0     0          0         0  1230934    5159    0    0    0     0       0          0
  eth0:14527038631 174773921    0    0    0     0          0         0 53768205408 150237839    0    0    0     0       0          0

and

#ifconfig eth0
eth0      Link encap:Ethernet  HWaddr 00:1f:d0:35:74:b5 
          inet addr:192.168.0.1  Bcast:192.168.0.255  Mask:255.255.255.0
          inet6 addr: fe80::21f:d0ff:fe35:74b5/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:174700827 errors:0 dropped:0 overruns:0 frame:0
          TX packets:150164953 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:14522357501 (13.5 GiB)  TX bytes:53726785504 (50.0 GiB)
          Interrupt:254 Base address:0xe000

As per [2], they say that "Copper cabling should not experience more than one bit error per 10^6 bits." But as you can see even after tx and rx data in GBs, I still don't have any CRC errors??? May be it might be the case that there are actually no CRC errors so far but it is hard for me to believe. So my two questions are:

a) Does the above two command really give you the hardware CRC count? Or does the Linux driver/OS masks it somehow?

b) Does anyone know any other method in Linux to measure the Ethernet CRC count?

I am wondering how much CRC errors people on this list are getting using the above two commands.

Any light on this subject is highly appreciated.

# ethtool -i eth0
driver: forcedeth
version: 0.61
firmware-version:
bus-info: 0000:00:07.0

[1] http://www.fpgarelated.com/usenet/fpga/show/31620-1.php

[2] http://www.mail-archive.com/ci...@groupstudy.com/msg93750.html

Kushal Koolwal

I do blog at http://blogs.koolwal.net/
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Kevin Ross

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Oct 19, 2009, 4:20:02 PM10/19/09
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It could be that the driver you are using doesn't report those statistics. It's also possible you haven't had any errors in that
time. In my statistics below, the send/receive byte counts have overflowed the 32-bit limit many times, so don't believe them. I
probably download 2-10 gigabytes per day, and the uptime is 33 days.

# cat /proc/net/dev
Inter-| Receive | Transmit
face |bytes packets errs drop fifo frame compressed multicast|bytes packets errs drop fifo colls carrier compressed

lo:2756594713 12545043 0 0 0 0 0 0 2756594713 12545043 0 0 0 0 0 0
eth-int:1840176101 158165784 0 2398 2398 2398 0 30001 1404160007 285315773 0 0 0 0 5 0
eth-ext:372772043 272335957 41 0 762 41 0 0 2455504315 268065658 0 0 0 0 0 0

# ifconfig
eth-ext Link encap:Ethernet HWaddr 00:50:da:12:3e:5f
inet addr:x.x.x.x Bcast:x.x.x.x Mask:255.255.255.0
inet6 addr: fe80::250:daff:fe12:3e5f/64 Scope:Link


UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:272336213 errors:41 dropped:0 overruns:762 frame:41
TX packets:268065969 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:372864777 (355.5 MiB) TX bytes:2455710933 (2.2 GiB)
Interrupt:18 Base address:0x2c00

eth-int Link encap:Ethernet HWaddr 00:24:8c:3d:7d:ba
inet addr:192.168.11.1 Bcast:192.168.11.255 Mask:255.255.255.0
inet6 addr: fe80::224:8cff:fe3d:7dba/64 Scope:Link


UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:158165784 errors:0 dropped:2398 overruns:2398 frame:2398
TX packets:285315773 errors:0 dropped:0 overruns:0 carrier:5
collisions:0 txqueuelen:1000
RX bytes:1840176101 (1.7 GiB) TX bytes:1404160007 (1.3 GiB)
Interrupt:29

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:16436 Metric:1
RX packets:12545043 errors:0 dropped:0 overruns:0 frame:0
TX packets:12545043 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:2756594713 (2.5 GiB) TX bytes:2756594713 (2.5 GiB)

# ethtool -i eth-ext
driver: 3c59x
version:
firmware-version:
bus-info: 0000:05:02.0

# ethtool -i eth-int
driver: ATL1E
version: 1.0.0.7-NAPI
firmware-version: L1e
bus-info: 0000:01:00.0

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Kevin Ross

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Oct 19, 2009, 5:00:01 PM10/19/09
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> From: Kevin Ross [mailto:ke...@familyross.net]
> Sent: Monday, October 19, 2009 1:14 PM

>
> It could be that the driver you are using doesn't report those
> statistics. It's also possible you haven't had any errors in that
> time.

I just checked on another computer, which uses the forcedeth driver (same as
you), and I have all zeros for those stats, too. Uptime on that computer is
16 days, with traffic aplenty (HTPC streaming HD movies over NFS from
server, approx. 4 to 8 GB each).

I'm inclined to believe it's an issue with the forcedeth driver.

Kushal Koolwal

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Oct 19, 2009, 5:30:02 PM10/19/09
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Kevin,

Thanks for providing all the information from your end. I did read somewhere that many times kernel driver will not report back at CRC errors found in the Physical layer even though there is a counter for that.

Also, in our previous email, where you posted your stats, I noticed that you didn't have any errors on the interface that is internal (eth-int). Is the box with forcedeth driver statistics also internal?

I did check another box with e1000 driver and I don't see anything in error, frame, drop, etc.

Looks like I will have to do some more research here.

Kushal Koolwal

I do blog at http://blogs.koolwal.net/


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