Introduce an alternative mechanism for wifi drivers to communicate

the channel on which a frame was received.

ieee80211_inputm() was expecting that ic->ic_bss->ni_chan would correspond
to the channel which is currently being scanned. This dates back to older
devices which are manually tuned to the next channel by the driver during
SCAN->SCAN state transitions.

However, this approach is very awkward for drivers which scan across a
whole range of channels in firmware. Such drivers had an ugly workaround
in place which tweaked ni_chan for each received frame.

Introduce a channel number field in the Rx info struct which drivers
can use to indicate the channel on which a frame was received.
If this field is set, net80211 will use it instead of using the current
channel of ic_bss. Use this new mechanism in all affected drivers.

Tested by jmc@, sthen@, and myself on iwm(4) and iwx(4).
Changes to iwn(4) and bwfm(4) are the same mechanical changes to get rid
of the ni_chan tweak, and are therefore expected to work.

ok sthen@ dlg@

1 files changed, 2 insertions, 21 deletions

diff --git a/sys/dev/pci/if_iwn.c b/sys/dev/pci/if_iwn.c
index dd629227807..e940010efa0 100644
--- a/sys/dev/pci/if_iwn.c
+++ b/sys/dev/pci/if_iwn.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_iwn.c,v 1.256 2022/03/11 18:00:45 mpi Exp $	*/
+/*	$OpenBSD: if_iwn.c,v 1.257 2022/03/20 12:01:58 stsp Exp $	*/
 
 /*-
  * Copyright (c) 2007-2010 Damien Bergamini <damien.bergamini@free.fr>
@@ -2004,8 +2004,6 @@ iwn_rx_done(struct iwn_softc *sc, struct iwn_rx_desc *desc,
 	struct ieee80211_frame *wh;
 	struct ieee80211_rxinfo rxi;
 	struct ieee80211_node *ni;
-	struct ieee80211_channel *bss_chan = NULL;
-	uint8_t saved_bssid[IEEE80211_ADDR_LEN] = { 0 };
 	struct mbuf *m, *m1;
 	struct iwn_rx_stat *stat;
 	caddr_t head;
@@ -2174,17 +2172,6 @@ iwn_rx_done(struct iwn_softc *sc, struct iwn_rx_desc *desc,
 	if (chan > IEEE80211_CHAN_MAX)
 		chan = IEEE80211_CHAN_MAX;
 
-	/* Fix current channel. */
-	if (ni == ic->ic_bss) {
-		/*
-		 * We may switch ic_bss's channel during scans.
-		 * Record the current channel so we can restore it later.
-		 */
-		bss_chan = ni->ni_chan;
-		IEEE80211_ADDR_COPY(&saved_bssid, ni->ni_macaddr);
-	}
-	ni->ni_chan = &ic->ic_channels[chan];
-
 #if NBPFILTER > 0
 	if (sc->sc_drvbpf != NULL) {
 		struct iwn_rx_radiotap_header *tap = &sc->sc_rxtap;
@@ -2232,15 +2219,9 @@ iwn_rx_done(struct iwn_softc *sc, struct iwn_rx_desc *desc,
 	/* Send the frame to the 802.11 layer. */
 	rxi.rxi_rssi = rssi;
 	rxi.rxi_tstamp = 0;	/* unused */
+	rxi.rxi_chan = chan;
 	ieee80211_inputm(ifp, m, ni, &rxi, ml);
 
-	/*
-	 * ieee80211_inputm() might have changed our BSS.
-	 * Restore ic_bss's channel if we are still in the same BSS.
-	 */
-	if (ni == ic->ic_bss && IEEE80211_ADDR_EQ(saved_bssid, ni->ni_macaddr))
-		ni->ni_chan = bss_chan;
-
 	/* Node is no longer needed. */
 	ieee80211_release_node(ic, ni);
 }