Date: Wed, 9 Oct 2013 20:27:55 -0400 From: Patrick Kelsey <kelsey@ieee.org> To: freebsd-net@freebsd.org Subject: [ieee80211] [patch] BPF taps not working for ieee80211 interfaces in monitor mode Message-ID: <CAD44qMVeT_FJP26NSt5uXRdqzyWvZvYNOMpybnAG5u9YunqVQw@mail.gmail.com>
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[-- Attachment #1 --]
Hi,
A bug was introduced in r254082 that results in BPF taps never being
enabled for ieee80211 interfaces that are in monitor mode.
Before r254082, bpf_track() in sys/net80211/ieee80211_freebsd.c was
identifying ieee80211 interfaces by checking to see if the value of
the ifp->if_start pointer was equal to ieee80211_start. r254082 was a
move away from using if_start to using if_transmit in the ieee80211
stack, and bpf_track() was correspondingly updated to check the value
of ifp->if_transmit against ieee80211_vap_transmit. The problem is
that ifp->if_transmit is set to null_transmit by
ieee80211_vap_attach() in sys/net80211/ieee80211.c for interfaces that
are in monitor mode (code that has been in place since r195846).
One fix that resolves the issue is to use what is likely to be a more
stable signature in the check in bpf_track().
A patch against r256155 is attached.
-Patrick
[-- Attachment #2 --]
Index: sys/net80211/ieee80211_freebsd.c
===================================================================
--- sys/net80211/ieee80211_freebsd.c (revision 256155)
+++ sys/net80211/ieee80211_freebsd.c (working copy)
@@ -808,9 +808,9 @@
static void
bpf_track(void *arg, struct ifnet *ifp, int dlt, int attach)
{
- /* NB: identify vap's by if_start */
+ /* NB: identify vap's by if_init */
if (dlt == DLT_IEEE802_11_RADIO &&
- ifp->if_transmit == ieee80211_vap_transmit) {
+ ifp->if_init == ieee80211_init) {
struct ieee80211vap *vap = ifp->if_softc;
/*
* Track bpf radiotap listener state. We mark the vap
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