From ecca5665e81b1a3e4de113b7a1af76d94d1f61ef Mon Sep 17 00:00:00 2001
From: Patrick Ohly <patrick.ohly@intel.com>
Date: Mon, 3 Nov 2014 17:42:19 +0100
Subject: [PATCH 2/3] runqemu: automatically run DHCP server

Some images are not able to configure their Ethernet based on the
"ip" kernel parameter, for example Tizen. Instead of having to
modify images, it is easier to provide what these images expect
and have a DHCP server running on the host.

At the moment, the modified scripts expect that "dhcp-native" was
built for the host. runqemu-ifup sets capabilities such that the dhcpd
can be run as normal user with just minimal privileges and then
runqemu-internal takes care of bringing the daemon up and taking it
down again. All dhcpd files are stored together with the tap lock file
under /tmp. dhcpd output goes to stdout.

Signed-off-by: Patrick Ohly <patrick.ohly@intel.com>
---
 scripts/runqemu-ifup     | 20 ++++++++++++++++++++
 scripts/runqemu-internal | 43 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 63 insertions(+)

diff --git a/scripts/runqemu-ifup b/scripts/runqemu-ifup
index b5a3db9..0806c40 100755
--- a/scripts/runqemu-ifup
+++ b/scripts/runqemu-ifup
@@ -57,6 +57,14 @@ if [ ! -x "$TUNCTL" ]; then
 	exit 1
 fi
 
+# TODO: make dhcpd optional?
+DHCPD=$NATIVE_SYSROOT_DIR/usr/sbin/dhcpd
+if [ ! -x "$DHCPD" ]; then
+	# TODO (?): integrate into qemu-helper-native
+	echo "Error: Unable to find dhcpd binary in '$NATIVE_SYSROOT_DIR/usr/sbin', please bitbake dhcp-native"
+	exit 1
+fi
+
 TAP=`$TUNCTL -b $GROUP 2>&1`
 STATUS=$?
 if [ $STATUS -ne 0 ]; then
@@ -89,6 +97,15 @@ if [ ! -x "$IPTABLES" ]; then
 	exit 1
 fi
 
+SETCAP=`which setcap 2> /dev/null`
+if [ "x$SETCAP" = "x" ]; then
+	SETCAP=/sbin/setcap
+fi
+if [ ! -x "$SETCAP" ]; then
+	echo "$SETCAP cannot be executed"
+	exit 1
+fi
+
 n=$[ (`echo $TAP | sed 's/tap//'` * 2) + 1 ]
 $IFCONFIG addr add 192.168.7.$n/32 broadcast 192.168.7.255 dev $TAP
 $IFCONFIG link set dev $TAP up
@@ -103,4 +120,7 @@ echo 1 > /proc/sys/net/ipv4/ip_forward
 echo 1 > /proc/sys/net/ipv4/conf/$TAP/proxy_arp
 $IPTABLES -P FORWARD ACCEPT
 
+# allow running dhcpd as normal user
+$SETCAP cap_net_raw,cap_net_bind_service+ep $DHCPD
+
 echo $TAP
diff --git a/scripts/runqemu-internal b/scripts/runqemu-internal
index 38745dd..3a9c0b4 100755
--- a/scripts/runqemu-internal
+++ b/scripts/runqemu-internal
@@ -172,6 +172,13 @@ else
                exit 1
         fi
 
+        DHCPD=$OECORE_NATIVE_SYSROOT/usr/sbin/dhcpd
+        if [ ! -x "$DHCPD" ]; then
+	    # TODO (?): integrate into qemu-helper-native
+            echo "Error: Unable to find dhcpd binary in '$NATIVE_SYSROOT_DIR/usr/sbin', please bitbake dhcp-native"
+            exit 1
+        fi
+
         POSSIBLE=`$IFCONFIG link | grep 'tap' | awk '{print $2}' | sed s/://`
         TAP=""
         LOCKFILE=""
@@ -222,6 +229,10 @@ else
         fi
 
         cleanup() {
+            # Ensure that we don't kill an unrelated process.
+            if [ ! -e "$DHCPPID" ] && [ -s $DHCPPID ] && ps $(cat $DHCPPID) | grep -q dhcpd; then
+                kill $(cat $DHCPPID)
+            fi
             if [ ! -e "$NOSUDO_FLAG" -a "$USE_PRECONF_TAP" = "no" ]; then
                 # Redirect stderr since we could see a LD_PRELOAD warning here if pseudo is loaded
                 # but inactive. This looks scary but is harmless
@@ -249,6 +260,38 @@ else
         n1=$(($n0 * 2 + 1))
         n2=$(($n1 + 1))
 
+        DHCPDIR=$LOCKFILE.dhcp
+        rm -rf $DHCPDIR
+        mkdir $DHCPDIR
+        DHCPCONF=$DHCPDIR/dhcpd.conf
+        DHCPLEASE=$DHCPDIR/dhcpd.leases
+        DHCPPID=$DHCPDIR/dhcpd.pid
+        cat >$DHCPCONF <<EOF
+option domain-name "localdomain";
+authoritative;
+
+# Basically forever...
+default-lease-time 60000;
+max-lease-time 60000;
+
+subnet 192.168.7.0 netmask 255.255.255.0 {
+  range 192.168.7.$n2 192.168.7.$n2;
+  option routers 192.168.7.$n1;
+}
+EOF
+        touch $DHCPLEASE
+        echo $DHCPD -d -cf $DHCPCONF -lf $DHCPLEASE -pf $DHCPPID $TAP
+        # TODO: where should output go?
+        $DHCPD -d -cf $DHCPCONF -lf $DHCPLEASE -pf $DHCPPID $TAP &
+        pid=$!
+        while [ ! -s $DHCPPID ]; do
+            sleep 1
+            if ! ps $pid | grep -q dhcpd; then
+                echo "$DHCPD terminated unexpectedly."
+                return 1
+            fi
+        done
+
         KERNEL_NETWORK_CMD="ip=192.168.7.$n2::192.168.7.$n1:255.255.255.0"
         QEMU_TAP_CMD="-net tap,vlan=0,ifname=$TAP,script=no,downscript=no"
         if [ "$KVM_ACTIVE" = "yes" ]; then
-- 
2.1.1