netdev - Re: Strange behavior of command ip

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Message-ID: <0ffca24d-4a7d-449e-8f48-c091af91c96d@intel.com>
Date: Thu, 15 Aug 2024 16:37:37 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Freek de Kruijf <f.de.kruijf@...il.com>, <netdev@...r.kernel.org>
Subject: Re: Strange behavior of command ip



On 8/15/2024 3:16 PM, Freek de Kruijf wrote:
> I have the following bash script:
> 
> #!/bin/bash
> getipv6() {
> nmcli con modify "Wired connection 1" ipv6.addr-gen-mode eui64
> nmcli con down "Wired connection 1"
> nmcli con up "Wired connection 1"
> /usr/bin/ip -6 a
> }
> getipv6
> 
> When I run the script the output is:
> 
> Connection 'Wired connection 1' successfully deactivated (D-Bus active path: /
> org/freedesktop/NetworkManager/ActiveConnection/23)
> Connection successfully activated (D-Bus active path: /org/freedesktop/
> NetworkManager/ActiveConnection/24)
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
>     inet6 ::1/128 scope host noprefixroute 
>        valid_lft forever preferred_lft forever
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
>     inet6 fe80::dea6:32ff:fe55:12be/64 scope link tentative noprefixroute 
>        valid_lft forever preferred_lft forever
> 
> When I run the command "/usr/bin/ip -6 a" the output is:
> 
> 1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000
>     inet6 ::1/128 scope host noprefixroute 
>        valid_lft forever preferred_lft forever
> 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000
>     inet6 2001:4c3c:702:b700:dea6:32ff:fe55:12be/64 scope global dynamic 
> noprefixroute 
>        valid_lft 4126sec preferred_lft 3466sec
>     inet6 fe80::dea6:32ff:fe55:12be/64 scope link noprefixroute 
>        valid_lft forever preferred_lft forever
> 
> Now the global IPv6 of eth0 is shown.
> 

Most probably nmcli takes time to actually configure the interface and
assign an ipv6 address. I do not know if nmcli waits for this to complete.

You could see if adding a delay between the nmcli and ip invocation in
the script?

According to nmcli the default wait time for nmcli con up is 90 seconds.
However, it is unclear to me what "up" means, and it is quite possible
that it does not include the assignment of the ipv6 address.

Thanks,
Jake