Set up for a backchannel Ethernet interface to be used in testing

src/scripts/mod_for_test_scripts/100setupTestingInterface

+#!/bin/bash
+
+# Copyright (c) 2009 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+echo "Configuring for eth1 backchannel"
+
+# Prevent connman from taking control of the backchannel network device.
+ORIG_CONF=${ROOT_FS_DIR}/etc/init/connman.conf
+TEMP_CONF=${ORIG_CONF}.tmp
+sed 's/connmand -W/connmand -I eth1 -W/' ${ORIG_CONF} > ${TEMP_CONF}
+mv -f ${TEMP_CONF} ${ORIG_CONF}
+
+# Arrange to run dhclient on the backchannel device but without
+# installing the default route, and stashing said route away for later
+# installation as a host route.
+cat > ${ROOT_FS_DIR}/etc/udev/rules.d/50-backchannel-eth1.rules <<EOF
+KERNEL=="eth*", SUBSYSTEMS=="usb", ACTION=="add", RUN+="/sbin/backchannel-setup %k"
+KERNEL=="eth1", SUBSYSTEMS=="usb", ACTION=="remove", RUN+="kill \$(cat /var/run/dhclient-%k.pid)"
+EOF
+
+cat > ${ROOT_FS_DIR}/sbin/backchannel-setup <<EOF
+#!/bin/sh
+
+if [ -f /var/run/dhclient-eth1.pid ]; then
+    # Something else is already going on - perhaps a second
+    # USB Ethernet device has been inserted. Let's not mess with it.
+    exit
+fi
+
+if [ "\$1" != "eth1" ]; then
+    initctl stop connman
+    # \$1 is the current name of the backchannel device. Swap it with eth1.
+    if ifconfig eth1 > /dev/null 2>&1; then
+        orig_eth1_mac=\$(ifconfig eth1 | awk '/HWaddr/ {print \$5}')
+        ifconfig eth1 down # must be down for nameif to work
+        nameif eth_tmp \${orig_eth1_mac}
+    fi
+    bdev_mac=\$(ifconfig \$1 | awk '/HWaddr/ {print \$5}')
+    ifconfig \$1 down # must be down for nameif to work
+    nameif eth1 \${bdev_mac}
+    if [ -n "\${orig_eth1_mac}" ]; then
+        nameif \$1 \${orig_eth1_mac}
+    fi
+    initctl start connman
+fi
+
+# Bring up the backchannel interface
+dhclient -q -pf /var/run/dhclient-eth1.pid \\
+            -lf /var/run/dhclient-eth1.leases \\
+            -cf /etc/dhclient-backchannel.conf \\
+            -sf /sbin/dhclient-backchannel-script \\
+         eth1
+EOF
+
+chmod +x ${ROOT_FS_DIR}/sbin/backchannel-setup
+
+cat > ${ROOT_FS_DIR}/etc/dhclient-backchannel.conf <<EOF
+request subnet-mask, broadcast-address, routers;
+EOF
+
+cat > ${ROOT_FS_DIR}/sbin/dhclient-backchannel-script <<EOF
+#!/bin/sh
+
+if [ -n "\$new_broadcast_address" ]; then
+    new_broadcast_arg="broadcast \$new_broadcast_address"
+fi
+if [ -n "\$new_subnet_mask" ]; then
+    new_subnet_arg="netmask \$new_subnet_mask"
+fi
+
+
+case "\$reason" in
+    MEDIUM|ARPCHECK|ARPSEND)
+        # Do nothing
+        ;;
+    PREINIT)
+        # The DHCP client is requesting that an interface be
+        # configured as required in order to send packets prior to
+        # receiving an actual address. - dhclient-script(8)
+
+        ifconfig \$interface inet 0 up
+
+        # We need to give the kernel some time to get the interface up.
+        sleep 1
+        ;;
+
+    BOUND|RENEW|REBIND|REBOOT|TIMEOUT)
+        if [ -n "\$old_ip_address" -a \
+             "\$old_ip_address" != "\$new_ip_address" ]; then
+            # IP address changed. Bringing down the interface will delete all routes,
+            # and clear the ARP cache.
+            ifconfig \$interface inet 0
+
+        fi
+
+        if [ -z "\$old_ip_address" -o "\$old_ip_address" != "\$new_ip_address" -o \
+            "\$reason" = "BOUND" -o "\$reason" = "REBOOT" ]; then
+
+            ifconfig \$interface inet \$new_ip_address \$new_subnet_arg \
+                \$new_broadcast_arg \$mtu_arg
+
+            # Since this script is for the backchannel testing interface,
+            # we don't set the default route from here, but we do stash
+            # it for possible later use in setting up a host route.
+            cp /dev/null /var/run/dhclient-\${interface}.routers
+            for router in \$new_routers; do
+                echo \$router >> /var/run/dhclient-\${interface}.routers
+            done
+        fi
+        ;;
+
+    EXPIRE|FAIL|RELEASE|STOP)
+        if [ -n "\$old_ip_address" ]; then
+            # Shut down interface, which will delete routes and clear arp cache.
+            ifconfig \$interface inet 0
+        fi
+        ;;
+esac
+EOF
+
+chmod +x ${ROOT_FS_DIR}/sbin/dhclient-backchannel-script