* Sysctl addr_gen_mode does not control tunnel link-local addr
@ 2021-10-20 1:30 Stephen Suryaputra
2021-10-20 12:59 ` Antonio Quartulli
0 siblings, 1 reply; 3+ messages in thread
From: Stephen Suryaputra @ 2021-10-20 1:30 UTC (permalink / raw)
To: netdev; +Cc: a
Hi,
I noticed that tunnels, especially sit before commit e5dd729460ca8
("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL
address"), generates link-local addr regardless of addr_gen_mode
setting. Is this a bug, or is there a specific reason?
In my system, the link-local addr are generated by a userspace process.
So, we set net.ipv6.conf.<dev>.addr_gen_mode to 1 (IN6_ADDR_GEN_MODE_NONE).
The commit e5dd729460ca8 doesn't change the behavior as it is renaming
sit_add_v4_addrs() to add_v4_addrs() as make it generic for GRE/IP6GRE
cases. I'm not sure what the current behavior is for GRE, i.e. whether
addr_gen_mode can control the generation of link-local addr.
If this is a bug or oversight, I think this diff should fix it and I can
put a formal patch.
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index c6a90b7bbb70..da7e83699eef 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3392,6 +3392,8 @@ static void addrconf_sit_config(struct net_device
*dev)
return;
}
+ if (idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_NONE)
+ return;
add_v4_addrs(idev);
if (dev->flags&IFF_POINTOPOINT)
The commit mention about addressing violation of RFC4291 on GRE and the diff
above doesn't cause it to change as the default addr_gen_mode is 0
(IN6_ADDR_GEN_MODE_EUI64).
Thanks,
Stephen.
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: Sysctl addr_gen_mode does not control tunnel link-local addr
2021-10-20 1:30 Sysctl addr_gen_mode does not control tunnel link-local addr Stephen Suryaputra
@ 2021-10-20 12:59 ` Antonio Quartulli
2021-10-20 13:50 ` Stephen Suryaputra
0 siblings, 1 reply; 3+ messages in thread
From: Antonio Quartulli @ 2021-10-20 12:59 UTC (permalink / raw)
To: Stephen Suryaputra, netdev
Hi,
On 20/10/2021 03:30, Stephen Suryaputra wrote:
> Hi,
>
> I noticed that tunnels, especially sit before commit e5dd729460ca8
> ("ip/ip6_gre: use the same logic as SIT interfaces when computing v6LL
> address"), generates link-local addr regardless of addr_gen_mode
> setting. Is this a bug, or is there a specific reason?
>
> In my system, the link-local addr are generated by a userspace process.
> So, we set net.ipv6.conf.<dev>.addr_gen_mode to 1 (IN6_ADDR_GEN_MODE_NONE).
>
> The commit e5dd729460ca8 doesn't change the behavior as it is renaming
> sit_add_v4_addrs() to add_v4_addrs() as make it generic for GRE/IP6GRE
> cases. I'm not sure what the current behavior is for GRE, i.e. whether
> addr_gen_mode can control the generation of link-local addr.
>
> If this is a bug or oversight, I think this diff should fix it and I can
> put a formal patch.
When I implemented this behavior for SIT interfaces I basically ported
what is currently happening for GRE.
Therefore, any change you apply to SIT, should also be reflected in the
GRE code path.
As of now, the SIT/GRE addrgen logic does not consider the mode setting
at all. But I am not sure it'd be easy to support all the values.
For sure, supporting IN6_ADDR_GEN_MODE_NONE is a low hanging fruit and
should be implemented.
>
> diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
> index c6a90b7bbb70..da7e83699eef 100644
> --- a/net/ipv6/addrconf.c
> +++ b/net/ipv6/addrconf.c
> @@ -3392,6 +3392,8 @@ static void addrconf_sit_config(struct net_device
> *dev)
> return;
> }
>
> + if (idev->cnf.addr_gen_mode == IN6_ADDR_GEN_MODE_NONE)
> + return;
Please add an empty line here.
> add_v4_addrs(idev);
>
> if (dev->flags&IFF_POINTOPOINT)
>
> The commit mention about addressing violation of RFC4291 on GRE and the diff
> above doesn't cause it to change as the default addr_gen_mode is 0
> (IN6_ADDR_GEN_MODE_EUI64).
Other than my nitpick above, I'd suggest applying the same change to the
GRE code path, as the behavior should be the same.
Moreover, do you think that addrconf_add_mroute() should not be executed
in this case? Otherwise you could simply add your new code into
add_v4_addrs().
Regards,
--
Antonio Quartulli
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Sysctl addr_gen_mode does not control tunnel link-local addr
2021-10-20 12:59 ` Antonio Quartulli
@ 2021-10-20 13:50 ` Stephen Suryaputra
0 siblings, 0 replies; 3+ messages in thread
From: Stephen Suryaputra @ 2021-10-20 13:50 UTC (permalink / raw)
To: Antonio Quartulli; +Cc: netdev
On Wed, Oct 20, 2021 at 02:59:01PM +0200, Antonio Quartulli wrote:
> For sure, supporting IN6_ADDR_GEN_MODE_NONE is a low hanging fruit and
> should be implemented.
>
Thanks for reaffirming this!
> Other than my nitpick above, I'd suggest applying the same change to the
> GRE code path, as the behavior should be the same.
> Moreover, do you think that addrconf_add_mroute() should not be executed
> in this case? Otherwise you could simply add your new code into
> add_v4_addrs().
Initially I was thinking that why there is a need to call
addrconf_add_mroute() given the link-local addr hasn't been set. On a
second look, yes, the conditional is better be in add_v4_addrs(). It
will take care of GRE as well.
I'll put a formal patch.
Thanks!
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-10-20 13:50 UTC | newest]
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2021-10-20 1:30 Sysctl addr_gen_mode does not control tunnel link-local addr Stephen Suryaputra
2021-10-20 12:59 ` Antonio Quartulli
2021-10-20 13:50 ` Stephen Suryaputra
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