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[wifi] capture: fix channel setting 

At least on NetBSD with the ath driver, it is impossible to change the
channel when the interface is in monitor mode (actually it is possible,
but when the interface is turned up again the channel is set back to its
prior value).
Therefore, to set the interface in monitor mode on a given channel, we
must:
- shut down,
- switch to managed mode (media autoselect) with the wanted channel,
- turn up,
- shut down again,
- switch to monitor mode,
- turn up again.

I implemented the same behaviour for Linux, maybe it's useless but it
can't hurt.
This commit is contained in:
Matteo Cypriani 2011-08-07 21:30:14 +02:00
parent 81611af216
commit 9a5853d48a
1 changed files with 40 additions and 32 deletions
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72
wifi/capture.sh
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@ -75,25 +75,36 @@ check_dependencies()
fi fi
} }
# Turns on the capture interface # Switches the capture interface to monitor mode, on the channel in
iface_up() # argument
iface_set_channel()
{ {
echo -n "Turning up interface $IFACE... " iface_down
ifconfig $IFACE up && echo "OK." \
|| error "Cannot turn the interface up!"
}
# Shuts down the capture interface echo -n "Setting interface $IFACE on channel $1... "
iface_down() case $OS in
{ Linux)
echo -n "Shuting down interface $IFACE... " iwconfig $IFACE mode managed channel $1
ifconfig $IFACE down && echo "OK." \ ;;
|| error "Cannot shut down the interface!" NetBSD)
ifconfig $IFACE media autoselect chan $1
;;
*)
error "Your OS is not supported."
;;
esac \
&& echo "OK." \
|| error "Cannot set the channel!"
iface_up
iface_monitor
} }
# Switches the capture interface to monitor mode # Switches the capture interface to monitor mode
iface_monitor() iface_monitor()
{ {
iface_down
echo -n "Switching interface $IFACE to monitor mode... " echo -n "Switching interface $IFACE to monitor mode... "
case $OS in case $OS in
Linux) Linux)
@ -108,25 +119,24 @@ iface_monitor()
esac \ esac \
&& echo "OK." \ && echo "OK." \
|| error "Cannot switch the interface to monitor mode!" || error "Cannot switch the interface to monitor mode!"
iface_up
} }
# Switches the capture interface on the channel in argument # Shuts down the capture interface
iface_set_channel() iface_down()
{ {
echo -n "Setting interface $IFACE on channel $1... " echo -n "Shuting down interface $IFACE... "
case $OS in ifconfig $IFACE down && echo "OK." \
Linux) || error "Cannot shut down the interface!"
iwconfig $IFACE channel $1 }
;;
NetBSD) # Turns on the capture interface
ifconfig $IFACE chan $1 iface_up()
;; {
*) echo -n "Turning up interface $IFACE... "
error "Your OS is not supported." ifconfig $IFACE up && echo "OK." \
;; || error "Cannot turn the interface up!"
esac \
&& echo "OK." \
|| error "Cannot set the channel!"
} }
# Invokes tcpdump and returns the number of packets captured # Invokes tcpdump and returns the number of packets captured
@ -210,13 +220,10 @@ FILE="$DESTDIR/$FILE"
check_dependencies check_dependencies
iface_down
iface_monitor
iface_up
echo "Trying to capture $NB_PKT packets..." echo "Trying to capture $NB_PKT packets..."
CAPTURED=0 CAPTURED=0
while [ $CAPTURED -eq 0 -a $CHANNEL -le 14 ] ; do while [ $CAPTURED -eq 0 -a $CHANNEL -le 14 ] ; do
echo
iface_set_channel $CHANNEL iface_set_channel $CHANNEL
wait_tcpdump $TIMEOUT & wait_tcpdump $TIMEOUT &
invoke_tcpdump invoke_tcpdump
@ -226,6 +233,7 @@ while [ $CAPTURED -eq 0 -a $CHANNEL -le 14 ] ; do
CHANNEL=`expr $CHANNEL + 1` CHANNEL=`expr $CHANNEL + 1`
done done
echo
[ $CAPTURED -gt 0 ] \ [ $CAPTURED -gt 0 ] \
&& echo "Capture file \"$FILE\" created with $CAPTURED packets." \ && echo "Capture file \"$FILE\" created with $CAPTURED packets." \
|| error "Failed to capture any packet!" || error "Failed to capture any packet!"