netdev - Re: [PATCH net-next] gre/sit: Don't generate link-local addr if addr_gen_mode is IN6_ADDR_GEN_MODE

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Message-ID: <20211021132229.GA6483@ICIPI.localdomain>
Date:   Thu, 21 Oct 2021 09:22:29 -0400
From:   Stephen Suryaputra <ssuryaextr@...il.com>
To:     Antonio Quartulli <a@...table.cc>
Cc:     netdev@...r.kernel.org, kuba@...nel.org, davem@...emloft.net
Subject: Re: [PATCH net-next] gre/sit: Don't generate link-local addr if
 addr_gen_mode is IN6_ADDR_GEN_MODE_NONE

On Thu, Oct 21, 2021 at 02:52:44PM +0200, Antonio Quartulli wrote:
> 
> Maybe I am missing something, but why checking the mode only for
> pointtopoint? If mode is NONE shouldn't this routine just abort
> regardless of the interface setup?
> 
If it isn't pointtopoint, the function sets up IPv4-compatible IPv6
address, i.e. non link-local (FE80::). addr_gen_mode NONE (1) is only
controlling the generation of link-local address. Quoting from the
sysctl doc:

addr_gen_mode - INTEGER
	Defines how link-local and autoconf addresses are generated.

	0: generate address based on EUI64 (default)
	1: do no generate a link-local address, use EUI64 for addresses generated
	   from autoconf
	2: generate stable privacy addresses, using the secret from
	   stable_secret (RFC7217)
	3: generate stable privacy addresses, using a random secret if unset

So, I thought the checking should be strictly when the link-local
address is about to be generated.