netdev - Re: [PATCH net v2] ipv6 addrconf: fix bug where deleting a mngtmpaddr can create a new temporary address

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Date: Mon, 24 Jul 2023 12:26:05 -0600
From: David Ahern <dsahern@...nel.org>
To: Maciej Żenczykowski <maze@...gle.com>,
 Maciej Żenczykowski <zenczykowski@...il.com>
Cc: Linux Network Development Mailing List <netdev@...r.kernel.org>,
 Jakub Kicinski <kuba@...nel.org>, Thomas Haller <thaller@...hat.com>,
 Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
 "David S. Miller" <davem@...emloft.net>, Jiri Pirko <jiri@...nulli.us>,
 Xiao Ma <xiaom@...gle.com>
Subject: Re: [PATCH net v2] ipv6 addrconf: fix bug where deleting a mngtmpaddr
 can create a new temporary address

On 7/20/23 10:00 AM, Maciej Żenczykowski wrote:
> currently on 6.4 net/main:
> 
>   # ip link add dummy1 type dummy
>   # echo 1 > /proc/sys/net/ipv6/conf/dummy1/use_tempaddr
>   # ip link set dummy1 up
>   # ip -6 addr add 2000::1/64 mngtmpaddr dev dummy1
>   # ip -6 addr show dev dummy1
> 
>   11: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>       inet6 2000::44f3:581c:8ca:3983/64 scope global temporary dynamic
>          valid_lft 604800sec preferred_lft 86172sec
>       inet6 2000::1/64 scope global mngtmpaddr
>          valid_lft forever preferred_lft forever
>       inet6 fe80::e8a8:a6ff:fed5:56d4/64 scope link
>          valid_lft forever preferred_lft forever
> 
>   # ip -6 addr del 2000::44f3:581c:8ca:3983/64 dev dummy1
> 
>   (can wait a few seconds if you want to, the above delete isn't [directly] the problem)
> 
>   # ip -6 addr show dev dummy1
> 
>   11: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>       inet6 2000::1/64 scope global mngtmpaddr
>          valid_lft forever preferred_lft forever
>       inet6 fe80::e8a8:a6ff:fed5:56d4/64 scope link
>          valid_lft forever preferred_lft forever
> 
>   # ip -6 addr del 2000::1/64 mngtmpaddr dev dummy1
>   # ip -6 addr show dev dummy1
> 
>   11: dummy1: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue state UNKNOWN group default qlen 1000
>       inet6 2000::81c9:56b7:f51a:b98f/64 scope global temporary dynamic
>          valid_lft 604797sec preferred_lft 86169sec
>       inet6 fe80::e8a8:a6ff:fed5:56d4/64 scope link
>          valid_lft forever preferred_lft forever
> 
> This patch prevents this new 'global temporary dynamic' address from being
> created by the deletion of the related (same subnet prefix) 'mngtmpaddr'
> (which is triggered by there already being no temporary addresses).
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Jiri Pirko <jiri@...nulli.us>
> Fixes: 53bd67491537 ("ipv6 addrconf: introduce IFA_F_MANAGETEMPADDR to tell kernel to manage temporary addresses")
> Reported-by: Xiao Ma <xiaom@...gle.com>
> Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
> ---
>  net/ipv6/addrconf.c | 14 ++++++++++----
>  1 file changed, 10 insertions(+), 4 deletions(-)
> 

Reviewed-by: David Ahern <dsahern@...nel.org>