#!/bin/sh

#   Copyright (c) 2020, Geert Rolf
#
#   Permission is hereby granted, free of charge, to any person obtaining a
#   copy of this software and associated documentation files (the "Software"),
#   to deal in the Software without restriction, including without limitation
#   the rights to use, copy, modify, merge, publish, distribute, sublicense,
#   and/or sell copies of the Software, and to permit persons to whom the
#   Software is furnished to do so, subject to the following conditions:
#
#   The above copyright notice and this permission notice shall be included in
#   all copies or substantial portions of the Software.
#
#   THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
#   IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
#   FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
#   GEERT ROLF BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
#   IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
#   CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#


# uncomment next line if you need more than one tap = run multiple SIMHs... edit the saved params file
#OPSMODE="expert"

PATH="/bin:/sbin:/etc:/usr/sbin:/usr/bin"
export PATH

# check brctl to exist
L=`whereis brctl |
	awk -F: '{ print $2 }' |
	grep brctl |
	wc -l`
if test $L -eq 0
then
	echo 'No brctl program -- please install package bridge-utils'
fi

# check tunctl to exist
LL=`whereis tunctl |
	awk -F: '{ print $2 }' |
	grep tunctl |
	wc -l`
if test $LL -eq 0
then
	echo 'No tunctl program -- please install package uml-utilities'
fi

# quit when either not installed
if test $L -eq 0 -o $LL -eq 0
then
	exit 1
fi

# make list of all interfaces ignoring lo
AVL_IF=`ip link show |
	grep '^[0-9]' |
	awk -F: '{ print $2 }' |
	grep -v 'lo' |
	sed '1,$s/^ //'`

# found br0 in active interfaces?
L=`echo $AVL_IF | grep br0 | wc -l`
if test $L -ne 0
then
	echo "$0: br0 already configured."
	echo "-- if you configured br0 statically don't use this script"
	echo "-- otherwise if you do not want permanent settings"
	echo "-- and want br0 configured differently reboot first"
	exit 1
fi

# let user chose the interface he/she wants to usx
echo "  Available networkinterfaces"
N=0
for I in $AVL_IF
do
	N=`expr $N + 1`
	L=`ip addr show $I |
		grep 'inet' |
		grep -v 'inet6' |
		wc -l`
	if test $L -eq 0
	then
		M="not configured"
	else
		M=`ip addr show $I |
			grep 'inet' |
			grep -v 'inet6' |
			awk '{ print $2 }' `
	fi

	# did we see wlan? alas...
	L=`echo $I | grep wlan | wc -l`
	if test $L -gt 0
	then
		M="$M (wlan not supported)"
		echo "-: $I $M"
		N=`expr $N - 1`
	else
		if test -r SnetSaved.$I
		then
			echo "$N: $I $M (saved params available)"
		else
			echo "$N: $I $M"
		fi
	fi
done
# take wlan out
AVL_IF=`echo $AVL_IF | sed 's/wlan.//'`

if test $N -gt 1
then
	ANSWER=0
	while test $ANSWER -lt 1 -o $ANSWER -gt $N
	do
		echo -n "Which interface do you want to use? "
		read ANSWER
	done
else
	ANSWER=1
fi

N=0
for I in $AVL_IF
do
	N=`expr $N + 1`
	if test $N -eq $ANSWER
	then
		ACT_IF=$I
	fi
done

# see if there are saved params for this interface
if test -r SnetSaved.$ACT_IF
then
	. ./SnetSaved.$ACT_IF
	echo "Saved params loaded from SnetSaved.$ACT_IF" 
fi

echo ""
echo "Interface to use for SIMH......... " $ACT_IF

if test "x$IPNR" = "x"
then
	L=`ip addr show $ACT_IF |
		grep inet |
		grep -v inet6 |
		wc -l`
	if test $L -eq 0
	then
		IPNR="not configured"
	else
		IPNR=`ip addr show dev $ACT_IF |
			grep inet |
			grep -v inet6 |
			awk '{ print $2 }' `
	fi
fi
echo "IPnumber on this interface........ " $IPNR

if test "x$IPBRO" = "x"
then
	IPBRO=`ip addr show dev $ACT_IF |
		grep inet |
		grep -v inet6 |
		sed '1s/^.*brd //' |
		sed '1s/[ 	].*$//'`
fi
echo "IP Broadcast on this interface.... " $IPBRO

if test "x$DEFRT" = "x"
then
	DEFRT=`netstat -rn |
		grep $ACT_IF |
		grep '^0\.' |
		uniq |
		awk '{ print $2 }'` 
fi
if test "x$DEFRT" = "x"
then
	echo "Default Route set to Gateway...... " none
else
	echo "Default Route set to Gateway...... " $DEFRT
fi

if test "x$IPFWD" = "x"
then
	IPFWD=`cat /proc/sys/net/ipv4/ip_forward`
fi
if test $IPFWD -eq 1
then
	echo "IP forwarding is active........... " YES
else
	echo "IP forwarding is active........... " NO
fi

# nr of taps the user wants or 1 for default
if test "x${NrTaps}" = "x"
then
	NrTaps=1
fi
echo "Number of taps to create.......... " $NrTaps


# the user who needs access to the tap
if test "x$SimhUser" = "x"
then
	if test "x${SUDO_USER}" != "x"
	then
		SimhUser=${SUDO_USER}
	else
		SimhUser=${USER}
	fi
fi
echo "User who runs SIMH on the taps.... " $SimhUser

# only save params when in expert OPSMODE
if test "X$OPSMODE" = "Xexpert"
then
	if test ! -r SnetSaved.$ACT_IF
	then
		cat - > SnetSaved.$ACT_IF <<EOF
#
# expert users: edit your params and rerun the SetupNet script
#

# ipnr including mask
IPNR=$IPNR
# do we forward between interfaces 0=no 1=yes
IPFWD=$IPFWD
# default gateway
DEFRT=$DEFRT
# nr of SIMH emulators you want in parallel that use network
NrTaps=$NrTaps
# username of the user running the SIMH emulators
SimhUser=$SimhUser
EOF

		L=`ls -l SnetSaved.$ACT_IF | grep root | wc -l`
		if test $L -eq 1
		then
			chown $SimhUser SnetSaved.$ACT_IF
		fi
	fi
fi


JOBFILE="/tmp/SNjob.$$"
TMPFILE="/tmp/SNtmp.$$"

cat - > $JOBFILE <<\EOF
#!/bin/sh

# This script should be run under root permission

PATH="/bin:/sbin:/etc:/usr/sbin:/usr/bin"
export PATH
EOF

cat - > $TMPFILE <<\EOF
echo ${CMD}
${CMD}
if test $? -ne 0
then
	echo '*** FAIL:' ${CMD}
	exit 1
fi

EOF

echo "CMD=\"ip link set ${ACT_IF} down\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

echo "CMD=\"brctl addbr br0\"" >> $JOBFILE
## echo "CMD=\"ip tuntap add mode tun name br0\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

N=0
while test $N -lt $NrTaps
do
	echo "CMD=\"tunctl -t tap${N} -u ${SimhUser}\"" >> $JOBFILE
	## echo "CMD=\"ip tuntap add mode tap name tap${N} user ${SimhUser} dev br0\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE

	N=`expr $N + 1`
done

echo "CMD=\"brctl addif br0 ${ACT_IF}\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

echo "CMD=\"brctl setfd br0 0\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

if ! test "$IPNR" = "not configured"
then
	echo "CMD=\"ip addr del ${IPNR} dev ${ACT_IF}\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE
fi

echo "CMD=\"ip link set ${ACT_IF} up\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

if ! test "$IPNR" = "not configured"
then
	echo "CMD=\"ip addr add ${IPNR} dev br0\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE
fi

echo "CMD=\"ip link set br0 up\"" >> $JOBFILE
cat $TMPFILE >> $JOBFILE

if test ! "x$DEFRT" = "x"
then
	## echo "CMD=\"ip route del default via ${DEFRT} dev ${ACT_IF}\"" >> $JOBFILE
	## cat $TMPFILE >> $JOBFILE

	echo "CMD=\"ip route add default via ${DEFRT} dev br0\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE
fi

ipfwd=`cat /proc/sys/net/ipv4/ip_forward`
if test $IPFWD -ne $ipfwd
then
	echo "CMD=\"echo ${IPFWD} > /proc/sys/net/ipv4/ip_forward\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE
fi

N=0
while test $N -lt $NrTaps
do
	echo "CMD=\"brctl addif br0 tap${N}\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE

	echo "CMD=\"ip link set tap${N} up\"" >> $JOBFILE
	cat $TMPFILE >> $JOBFILE

	N=`expr $N + 1`
done

cat - >> $JOBFILE <<EOF
echo ""
echo 'Network reconfigured for use by SIMH simulators'
echo "Bridge br0 with access tap0 wired into interface ${ACT_IF}"
echo 'Configure tap:tap0 for your 1st SIMH host'
echo ""
echo 'Use unique IPnrs on your SIMH hosts within the'
echo 'same network and set a default route if needed'

rm -f $JOBFILE
EOF

if test "X$OPSMODE" = "Xexpert"
then
	echo ""
	echo "-- To change the params above edit SnetSaved.$ACT_IF"
	echo "-- and rerun this script before executing the job"
fi

L=`ls -l $JOBFILE | grep root | wc -l`
if test $L -gt 0
then
	echo "Executing $JOBFILE ..."
	echo -n "Proceed...?  (y)/n "
	read ANSWER
	if test "x$ANSWER" = "xn"
	then
		echo "-- To execute: bash $JOBFILE"
		exit 0
	fi
	bash ${JOBFILE}
else
	echo ""
	echo "-- Executing $JOBFILE requires root permission"
	echo "-- Either use sudo or su to execute: bash $JOBFILE"
fi

rm -f $TMPFILE