Linux – iproute2 interface statistics seem wrong

iproute2linux

For some reason, ip -s link does not show the same numbers as /proc/net/dev, specifically the overrun count.

For a given interface, ip shows no overrun packets:

$ ip -s link show eth-ext1
7: eth-ext1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 00:08:a2:0d:00:74 brd ff:ff:ff:ff:ff:ff
    RX: bytes  packets  errors  dropped overrun mcast   
    1038103044434 1099087192 0       0       0       401298  
    TX: bytes  packets  errors  dropped carrier collsns 
    543051882227 844808055 0       0       0       0

While in proc we see non-zero overrun (which is what I am assuming fifo is referring to):

$ cat /proc/net/dev
Inter-|   Receive                                                |  Transmit
face |bytes    packets errs drop fifo frame compressed multicast|bytes    packets errs drop fifo colls carrier compressed
[...]
eth-ext1: 1038106099296 1099090833    0    0 467554     0          0    401301 543052535442 844810749    0    0    0     0       0          0

I'm inclined to believe that there actually were overrun packets on the interface, so it appears that the output of ip link is not correct. Is there anything I am missing?

Best Answer

fifo and overrun are not the same. Just type ip -s -s a, there would be something like this 

RX: bytes  packets  errors  dropped overrun mcast
53152      864      0       0       0       0
RX errors: length   crc     frame   fifo    missed
           0        0       0       0       0
TX: bytes  packets  errors  dropped carrier collsns
53152      864      0       0       0       0
TX errors: aborted  fifo   window heartbeat transns
           0        0       0       0       0

overrun — the total number of receiver overruns resulting in dropped packets. As a rule, if the interface is overrun, it means serious problems in the kernel or that your machine is too slow for this interface.

fifo (file input file output) errors

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