From: Sven Eckelmann <sven@narfation.org>
To: b.a.t.m.a.n@lists.open-mesh.org
Cc: "Leonardo Mörlein" <me@irrelefant.net>,
"Antonio Quartulli" <a@unstable.cc>
Subject: Re: [B.A.T.M.A.N.] [RFC PATCH] batman-adv: mitigate issue when empty vlan is received
Date: Tue, 08 May 2018 10:45:51 +0200 [thread overview]
Message-ID: <2006071.d5ofkIttSZ@bentobox> (raw)
In-Reply-To: <7337501.sxbCbvYRv0@bentobox>
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n Montag, 7. Mai 2018 12:23:57 CEST Sven Eckelmann wrote:
> This would sound to me like the vlan should just be
> created instead of adding this workaround. But maybe you should discuss the
> details here with Antonio because at the end it is just about the different
> ways of handling "!vlan" case from your patch.
Just had a look at the cleanup code for vlans and it seems like each vlan
in vlan_list must contain at least one entry (according to
vlan->tt.num_entries) and otherwise batadv_tt_global_size_mod will drop it.
So it isn't as easy as just adding a simple vlan for each received vlan
entry via TT response.
So your patch (or a variant of it) will most likely be the way to go for
receivers.
Now to your commit message:
On Sonntag, 6. Mai 2018 21:55:59 CEST Leonardo Mörlein wrote:
> batman-adv: mitigate issue when empty vlan is received
Something more specific would be nice. Maybe somebody else has a better
idea but what about:
batman-adv: Mitigate TT loop when receiving empty VLAN
> This patch is not a fix for the issue itself, but a fix for the
> other nodes, which are also influenced by the issue.
I personally don't like to read "this patch" in commit messages. This part
should maybe be reformulated and put at the end (before the Fixes line).
Something like:
While the problem is caused by the sender, the receiver can mitigate the
problem by ignoring (potentially) empty VLANs during the CRC check.
[...]
> - This behaviour is a bug! Batman-adv nodes must not send TT
> announcements for empty vlans.
Where is this defined as incorrect message? But yes, the current
implementation cannot handle it.
> - The receiving batman-adv can not handle incoming TT announcements
> with empty vlans. (The crc check routine batadv_tt_global_check_crc()
> fails.)
This is to vague as discussed earlier. Maybe something more like:
- The receiving batman-adv can not handle incoming TT announcements with
empty vlans. No new struct batadv_orig_node_vlan entry will be added
to batadv_orig_node->vlan_list. This will cause the crc check routine
batadv_tt_global_check_crc() to fail because it cannot find the local
representation of this empty vlan.
[...]
> - This causes a lot of unneeded TT traffic. In Freifunk Hannover we
> decreased the amount of from ~20kpp/s to ~4kpp/s on our supernodes.
> We have ~800 nodes, which are connected via vpn to one of six
> supernodes. Those supernodes are connected with each other in a fully
> connected mesh.
This part doesn't seem to fit in the list and might just be a new paragraph
at the end to summarize the impact of the problem.
A "Fixes: " line is missing here. Please check whether this sounds about
right:
Fixes: 7ea7b4a14275 ("batman-adv: make the TT CRC logic VLAN specific")
Kind regards,
Sven
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next prev parent reply other threads:[~2018-05-08 8:45 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-05-06 19:55 [B.A.T.M.A.N.] [RFC PATCH] batman-adv: mitigate issue when empty vlan is received Leonardo Mörlein
2018-05-07 6:32 ` Sven Eckelmann
2018-05-07 8:06 ` me
2018-05-07 10:23 ` Sven Eckelmann
2018-05-08 8:45 ` Sven Eckelmann [this message]
2018-05-09 14:08 ` Marek Lindner
2018-05-09 16:06 ` [B.A.T.M.A.N.] [RFC] batman-adv: prevent TT request storms by not sending inconsistent TT TLVLs Marek Lindner
2018-05-09 17:21 ` Sven Eckelmann
2018-05-09 18:20 ` Sven Eckelmann
2018-05-09 20:38 ` Sven Eckelmann
2018-05-09 21:34 ` lemoer
2018-05-10 9:12 ` Antonio Quartulli
2018-05-10 10:28 ` Marek Lindner
2018-05-10 14:41 ` [B.A.T.M.A.N.] [RFC v2] " Marek Lindner
2018-05-10 15:50 ` Sven Eckelmann
2018-05-11 15:58 ` Marek Lindner
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