Why 'ip' command with long 'label' field gives error "RTNETLINK answers: Numerical result out of range" ?

Solution In Progress - Updated -

Environment

  • Red Hat Enterprise Linux 5
  • Red Hat Enterprise Linux 6
  • Red Hat Enterprise Linux 7

Issue

  • ip command when used with label option gives error RTNETLINK answers: Numerical result out of range if the label string is more than 15 characters in length.
[root@test ~]# rpm -qa |grep -i iproute
iproute-2.6.32-31.el6.x86_64

[root@test ~]# ip addr add 10.65.X.X/23 dev eth0:1 label eth0:1:sn0:sn0:sn0
RTNETLINK answers: Numerical result out of range
[root@test ~]# ip addr add 10.65.X.X/23 dev eth0:1 label eth0:1:sn0:sn0:sn
RTNETLINK answers: Numerical result out of range
[root@test ~]# ip addr add 10.65.X.X/23 dev eth0:1 label eth0:1:sn0:sn0:s
RTNETLINK answers: Numerical result out of range
[root@test ~]# ip addr add 10.65.X.X/23 dev eth0:1 label eth0:1:sn0:sn0:
[root@test ~]#
  • Is this limit documented any where ?

Resolution

  • The limit is mentioned in the Networking guide Notes for Administrators
  • Change network interface (or alias) name to use 15 characters. i.e interface name + label < 16 characters. (e.g. eth0:1234567890). As maximum length supported for network interface name is 15 characters.
  • Check RHEL7 man pages,
The maximum interface name length is defined by the kernel headers and is a global limit, affecting all applications. 

Root Cause

  • label is defined in the source as an unsigned 32-bit integer and is as per design.

Diagnostic Steps

  • Try reproducing steps as mentioned in issue.
  • Command gets executed successfully only when label option string has characters less then or equal to 15. man pages (# man ip) doesn't speak about this limitation.

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