Re: [PATCH] mac80211: mesh: only warn if mesh peering is established

[Markus Theil <markus.theil@tu-ilmenau.de>]

On 12/14/19 11:13 AM, Markus Theil wrote:
> On 12/13/19 10:13 AM, Johannes Berg wrote:
>> On Tue, 2019-12-03 at 19:06 +0100, Markus Theil wrote:
>>> The following warning is triggered every time an unestablished mesh peer
>>> gets dumped. This patch checks, if a peer link is established, when dum-
>>> ping the airtime link metric.
>>>
>>> [ 9563.022567] WARNING: CPU: 0 PID: 6287 at net/mac80211/mesh_hwmp.c:345
>>>                airtime_link_metric_get+0xa2/0xb0 [mac80211]
>>> [ 9563.022697] Hardware name: PC Engines apu2/apu2, BIOS v4.10.0.3
>>> [ 9563.022756] RIP: 0010:airtime_link_metric_get+0xa2/0xb0 [mac80211]
>>> [ 9563.022838] Call Trace:
>>> [ 9563.022897]  sta_set_sinfo+0x936/0xa10 [mac80211]
>>> [ 9563.022964]  ieee80211_dump_station+0x6d/0x90 [mac80211]
>>> [ 9563.023062]  nl80211_dump_station+0x154/0x2a0 [cfg80211]
>>> [ 9563.023120]  netlink_dump+0x17b/0x370
>>> [ 9563.023130]  netlink_recvmsg+0x2a4/0x480
>>> [ 9563.023140]  ____sys_recvmsg+0xa6/0x160
>>> [ 9563.023154]  ___sys_recvmsg+0x93/0xe0
>>> [ 9563.023169]  __sys_recvmsg+0x7e/0xd0
>>> [ 9563.023210]  do_syscall_64+0x4e/0x140
>>> [ 9563.023217]  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>> OK, I can see how this happens.
>>
>> However,
>>
>>> +	if (sta->mesh->plink_state != NL80211_PLINK_ESTAB)
>>> +		return MAX_METRIC;
>>> +
>> I'm not really sure this is the right way to fix it?
>>
>> I'm sure you observed this only when the link isn't established yet, but
>> it seems to me that even when a link is established it could still
>> happen?
>>
>> Or are the frames that are necessary for link establishment enough to
>> always set the metric?
>>
>> johannes
> The current mac80211 code initializes this moving average when setting
> the peer link to established in sta_apply_mesh_params.
>
> case NL80211_PLINK_ESTAB:
>             ...
>             ewma_mesh_tx_rate_avg_init(&sta->mesh->tx_rate_avg);
>             /* init at low value */
>             ewma_mesh_tx_rate_avg_add(&sta->mesh->tx_rate_avg, 10);
>             break;
>
> This ewma_mesh_tx_rate_avg_add is the only reference that I found in the
> code. It seems, that this avg is only initialized and never updated
> during the plink lifetime.
I've overlooked that ieee80211s_update_metric updates the rate avg.