netdev - Re: [PATCH net v4] net: ipv6: support reporting otherwise unknown prefix flags in RTM

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Message-ID: <5889e545-ee31-4f0f-bf27-5f9ebd9d24fc@kernel.org>
Date: Thu, 7 Dec 2023 09:18:47 -0700
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>,
 "David S . Miller" <davem@...emloft.net>, Eric Dumazet
 <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>,
 Paolo Abeni <pabeni@...hat.com>, Lorenzo Colitti <lorenzo@...gle.com>
Subject: Re: [PATCH net v4] net: ipv6: support reporting otherwise unknown
 prefix flags in RTM_NEWPREFIX

On 12/6/23 10:36 AM, Maciej Żenczykowski wrote:
> Lorenzo points out that we effectively clear all unknown
> flags from PIO when copying them to userspace in the netlink
> RTM_NEWPREFIX notification.
> 
> We could fix this one at a time as new flags are defined,
> or in one fell swoop - I choose the latter.
> 
> We could either define 6 new reserved flags (reserved1..6) and handle
> them individually (and rename them as new flags are defined), or we
> could simply copy the entire unmodified byte over - I choose the latter.
> 
> This unfortunately requires some anonymous union/struct magic,
> so we add a static assert on the struct size for a little extra safety.
> 
> Cc: David Ahern <dsahern@...nel.org>
> Cc: Lorenzo Colitti <lorenzo@...gle.com>
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Maciej Żenczykowski <maze@...gle.com>
> ---
>  include/net/addrconf.h | 12 ++++++++++--
>  include/net/if_inet6.h |  4 ----
>  net/ipv6/addrconf.c    |  6 +-----
>  3 files changed, 11 insertions(+), 11 deletions(-)
> 

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