netdev - Re: [PATCH net] ipv6: Fix address dump when IPv6 is disabled on an interface

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Date: Thu, 21 Mar 2024 18:47:47 +0100
From: Eric Dumazet <edumazet@...gle.com>
To: Ido Schimmel <idosch@...dia.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, kuba@...nel.org, 
	pabeni@...hat.com, dsahern@...nel.org, gal@...dia.com
Subject: Re: [PATCH net] ipv6: Fix address dump when IPv6 is disabled on an interface

On Thu, Mar 21, 2024 at 6:31 PM Ido Schimmel <idosch@...dia.com> wrote:
>
> Cited commit started returning an error when user space requests to dump
> the interface's IPv6 addresses and IPv6 is disabled on the interface.
> Restore the previous behavior and do not return an error.
>
> Before cited commit:
>
>  # ip address show dev dummy1
>  2: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>      link/ether 1a:52:02:5a:c2:6e brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::1852:2ff:fe5a:c26e/64 scope link proto kernel_ll
>         valid_lft forever preferred_lft forever
>  # ip link set dev dummy1 mtu 1000
>  # ip address show dev dummy1
>  2: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1000 qdisc noqueue state UNKNOWN group default qlen 1000
>      link/ether 1a:52:02:5a:c2:6e brd ff:ff:ff:ff:ff:ff
>
> After cited commit:
>
>  # ip address show dev dummy1
>  2: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>      link/ether 1e:9b:94:00:ac:e8 brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::1c9b:94ff:fe00:ace8/64 scope link proto kernel_ll
>         valid_lft forever preferred_lft forever
>  # ip link set dev dummy1 mtu 1000
>  # ip address show dev dummy1
>  RTNETLINK answers: No such device
>  Dump terminated
>
> With this patch:
>
>  # ip address show dev dummy1
>  2: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>      link/ether 42:35:fc:53:66:cf brd ff:ff:ff:ff:ff:ff
>      inet6 fe80::4035:fcff:fe53:66cf/64 scope link proto kernel_ll
>         valid_lft forever preferred_lft forever
>  # ip link set dev dummy1 mtu 1000
>  # ip address show dev dummy1
>  2: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1000 qdisc noqueue state UNKNOWN group default qlen 1000
>      link/ether 42:35:fc:53:66:cf brd ff:ff:ff:ff:ff:ff
>
> Fixes: 9cc4cc329d30 ("ipv6: use xa_array iterator to implement inet6_dump_addr()")
> Reported-by: Gal Pressman <gal@...dia.com>
> Closes: https://lore.kernel.org/netdev/7e261328-42eb-411d-b1b4-ad884eeaae4d@linux.dev/
> Tested-by: Gal Pressman <gal@...dia.com>
> Signed-off-by: Ido Schimmel <idosch@...dia.com>
> ---
> A similar change was done for IPv4 in commit cdb2f80f1c10 ("inet: use
> xa_array iterator to implement inet_dump_ifaddr()"), but I'm not aware
> of a way to disable IPv4 other than unregistering the interface, so I
> don't see a reason to change the IPv4 code.
> ---

Thanks for the fix.

Reviewed-by: Eric Dumazet <edumazet@...gle.com>