Return-path: Received: from packetmixer.de ([79.140.42.25]:49165 "EHLO mail.mail.packetmixer.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932352AbcJXOxj (ORCPT ); Mon, 24 Oct 2016 10:53:39 -0400 From: Simon Wunderlich To: Johannes Berg Cc: Antonio Quartulli , linux-wireless@vger.kernel.org Subject: Re: [PATCH v2 2/2] mac80211: passively scan DFS channels if requested Date: Mon, 24 Oct 2016 16:53:30 +0200 Message-ID: <3164753.QVH0CDzpbV@prime> (sfid-20161024_165343_975880_DDEF709D) In-Reply-To: <1477319916.4085.29.camel@sipsolutions.net> References: <1447464560-28104-1-git-send-email-antonio@meshcoding.com> <4116422.yZP7iyh9mq@prime> <1477319916.4085.29.camel@sipsolutions.net> MIME-Version: 1.0 Content-Type: multipart/signed; boundary="nextPart1924920.4O7cC1z8Cr"; micalg="pgp-sha512"; protocol="application/pgp-signature" Sender: linux-wireless-owner@vger.kernel.org List-ID: --nextPart1924920.4O7cC1z8Cr Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" On Monday, October 24, 2016 4:38:36 PM CEST Johannes Berg wrote: > On Mon, 2016-10-24 at 16:36 +0200, Simon Wunderlich wrote: > > On Monday, October 24, 2016 4:16:02 PM CEST Johannes Berg wrote: > > > On Mon, 2016-10-24 at 15:42 +0200, Simon Wunderlich wrote: > > > > Otherwise, it would be pretty much impossible to perform CSAs to > > > > another DFS channel. > > > > > > I was told that to do that you'd need another NIC that's pre- > > > CAC'ing another channel. > > > > Here is the portion from ETSI 301 893 v1.8.1 [1] (the most recent one > > to my knowledege), section 4.7.1.4 which describes operation from > > > > master devices (Access Points): > > [...] > > Yeah I'm pretty sure there are differences in ETSI vs. FCC. Perhaps the > information I was told about was for FCC. But perhaps it's all just > completely wrong :) I think I've found the right specification [1] for FCC. They doesn't state so explicitly that it is allowed, but I don't see any remark that this behaviour is forbidden, either. The important section is 5.1.1 Master devices in 905462 D02 UNII DFS Compliance Procedures New Rules v02, which is pretty similar to ETSI. They say: a) The Master Device will use DFS in order to detect Radar Waveforms with received signal strength above the DFS Detection Threshold in the 5250 - 5350 MHz and 5470 - 5725 MHz bands. DFS is not required in the 5150 - 5250 MHz or 5725 - 5825 MHz bands. b) Before initiating a network on a Channel, the Master Device will perform a Channel Availability Check for a specified time duration (Channel Availability Check Time) to ensure that there is no radar system operating on the Channel, using DFS described under subsection a) above. c) The Master Device initiates a U-NII network by transmitting control signals that will enable other U-NII devices to Associate with the Master Device. d) During normal operation, the Master Device will monitor the Channel (In-Service Monitoring) to ensure that there is no radar system operating on the Channel, using DFS described under a). e) If the Master Device has detected a Radar Waveform during In-Service Monitoring as described under d), the Operating Channel of the U- NII network is no longer an Available Channel. The Master Device will instruct all associated Client Device(s) to stop transmitting on this Channel within the Channel Move Time. The transmissions during the Channel Move Time will be limited to the Channel Closing Transmission Time. Again, no explicit "on installation" here, but there is also nothing saying that we can not check/operate on other channels in the meantime. (NOTE: going off-channel while operating is a different topic). Cheers, Simon [1] https://apps.fcc.gov/oetcf/kdb/forms/FTSSearchResultPage.cfm? switch=P&id=27155 --nextPart1924920.4O7cC1z8Cr Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part. Content-Transfer-Encoding: 7Bit -----BEGIN PGP SIGNATURE----- iQIcBAABCgAGBQJYDiBqAAoJEKEr45hCkp6hgAcQALWZ1E9Ro5Ms1vKgBobFqwWh GyfJsyT5diGhinV89r8n6x9EwmndnQQZSrk9w9EuIFJclAi6cKW1v9G8BbohMmni 041TZdqqZ2FK5+AZVnT6JhHyHawfmAVeuAMD+PVzjCwz4ug16gSvq9Vgr2s8uxiF DaIxgMQqW2yJw5PBhySHW920lnIU3s8ySPlNz5gjxMVbQyKMvQYkAWR3KP2bhIS4 lrBVvXyUPHdeFQERFbH1qq/C1vR4zxM4HQeMn11ASJW70E4bQKOlMpPbcPceLwWM qbcQT7O0Id5skS7Zgtf6buKpc+yKtRUxcuxTL6KDc/2IAWEhvQKpyYKcaablqzMh sMr8s236HifyXXyTQ9pJifVpL3Vox/SHn0MMB1XB/2uFEeajDEMFyNDywE0Cqz/s prAu/s0w6ZU3FJ917tc8sOpwS2884TzanwkPOee5szQHMXQvznkSlJgD9X8VwS+t fV1CYBEGYfg/LlscAbqjq9QHynbEB/SDc6HCJAaLXEhr7rCnfHN2J483cSxX7iba KPKHp5XBJ5t4+jHdSDesLaZBeZC4DkmuYIHMyXVNjjYirNqnlie58+nEdDojqXpc KkQwKkAcZ1uideh1gtB6qat96CuvTQeXbozlg4DFVVJfEzBuI+BesDZQ1R2jFxNL kD9iSbvR/R/JIr3mewCU =jib6 -----END PGP SIGNATURE----- --nextPart1924920.4O7cC1z8Cr--