--- /dev/null
+#!/bin/bash -norc
+
+# Magic startup script for a UML instance. As long as unique
+# instances are started, more than one of them can be concurrently
+# in use on a single system. All their network interfaces are
+# bridged together onto the virtual bridge "virbr0" which is
+# supplied by the "libvirt" package.
+#
+# Note that a DHCP server is started for that interface. It's
+# configured in this file:
+# /etc/libvirt/qemu/networks/default.xml
+# Unfortunately what I see there serves all possible DHCP addresses,
+# so stealing them like we do here isn't really kosher. To fix
+# it, that configuration should change to serve a smaller subset
+# of the available address range.
+#
+# Each instance uses its own tun/tap device, created using the
+# "tunctl" command. The assigned tap device will correspond with
+# the guest id (a small integer representing the instance), i.e.,
+# guest id 1 uses tap1, etc. The tap device is attached to the
+# virtual bridge, which will have its own subnet associated with it.
+# The guest side of that interface will have the same subnet as the
+# bridge interface, with the bottom bits representing (normally) 100
+# more than the guest id. So for subnet 192.168.122.0/24, guest
+# id 1 will use ip 192.168.122.101, guest id 2 will use ip
+# 192.168.122.102, and so on. Because these interfaces are bridged,
+# they can all communicate with each other.
+
+# You will want to override this by setting and exporting the
+# "CEPH_TOP" environment variable to be the directory that contains
+# the "ceph-client" source tree.
+CEPH_TOP="${CEPH_TOP:-/home/elder/ceph}"
+
+# You may want to change this too, if you want guest UML instances
+# to have a diffeerent IP address range. The guest IP will be based
+# on this plus GUEST_ID (defined below).
+GUEST_IP_OFFSET="${GUEST_IP_OFFSET:-100}"
+
+#############################
+
+if [ $# -gt 1 ]; then
+ echo "" >&2
+ echo "Usage: $(basename $0) [guest_id]" >&2
+ echo "" >&2
+ echo " guest_id is a small integer (default 1)" >&2
+ echo " (each UML instance needs a distinct guest_id)" >&2
+ echo "" >&2
+ exit 1
+elif [ $# -eq 1 ]; then
+ GUEST_ID="$1"
+else
+ GUEST_ID=1
+fi
+
+# This will be what the guest host calls itself.
+GUEST_HOSTNAME="uml-${GUEST_ID}"
+
+# This is the path to the boot disk image used by UML.
+DISK_IMAGE_A="${CEPH_TOP}/ceph-client/uml.${GUEST_ID}"
+if [ ! -f "${DISK_IMAGE_A}" ]; then
+ echo "root disk image not found (or not a file)" >&2
+ exit 2
+fi
+
+# Hostid 1 uses tun/tap device tap1, hostid 2 uses tap2, etc.
+TAP_ID="${GUEST_ID}"
+# This is the tap device used for this UML instance
+TAP="tap${TAP_ID}"
+
+# This is just used to mount an image temporarily
+TMP_MNT="/tmp/m$$"
+
+# Where to put a config file generated for this tap device
+TAP_IFUPDOWN_CONFIG="/tmp/interface-${TAP}"
+
+# Compute the HOST_IP and BROADCAST address values to use,
+# and assign shell variables with those names to their values.
+# Also compute BITS, which is the network prefix length used.
+# The NETMASK is then computed using that BITS value.
+eval $(
+ip addr show virbr0 | awk '
+/inet/ {
+ split($2, a, "/")
+ printf("HOST_IP=%s\n", a[1]);
+ printf("BROADCAST=%s\n", $4);
+ printf("BITS=%s\n", a[2]);
+ exit(0);
+}')
+
+# Use bc to avoid 32-bit wrap when computing netmask
+eval $(
+echo -n "NETMASK="
+bc <<! | fmt | sed 's/ /./g'
+m = 2 ^ 32 - 2 ^ (32 - ${BITS})
+for (p = 24; p >= 0; p = p - 8)
+ m / (2 ^ p) % 256
+!
+)
+
+# Now use the netmask and the host IP to compute the subnet address
+# and from that the guest IP address to use.
+eval $(
+awk '
+function from_quad(addr, a, val, i) {
+ if (split(addr, a, ".") != 4)
+ exit(1); # address not in dotted quad format
+ val = 0;
+ for (i = 1; i <= 4; i++)
+ val = val * 256 + a[i];
+ return val;
+}
+function to_quad(val, addr, i) {
+ addr = "";
+ for (i = 1; i <= 4; i++) {
+ addr = sprintf("%u%s%s", val % 256, i > 1 ? "." : "", addr);
+ val = int(val / 256);
+ }
+ if ((val + 0) != 0)
+ exit(1); # value provided exceeded 32 bits
+ return addr;
+}
+BEGIN {
+ host_ip = from_quad("'${HOST_IP}'");
+ netmask = from_quad("'${NETMASK}'");
+ guest_net_ip = '${GUEST_IP_OFFSET}' + '${GUEST_ID}';
+ if (and(netmask, guest_net_ip))
+ exit(1); # address too big for subnet
+ subnet = and(host_ip, netmask);
+ guest_ip = or(subnet, guest_net_ip);
+ if (guest_ip == host_ip)
+ exit(1); # computed guest ip matches host ip
+
+ printf("SUBNET=%s\n", to_quad(subnet));
+ printf("GUEST_IP=%s\n", to_quad(guest_ip));
+}
+' < /dev/null
+)
+
+############## OK, we now know all our network parameters...
+
+# There is a series of things that need to be done as superuser,
+# so group them all into one big (and sort of nested!) sudo request.
+sudo -s <<EnD_Of_sUdO
+# Mount the boot disk for the UML and set up some configuration
+# files there.
+mkdir -p "${TMP_MNT}"
+mount -o loop "${DISK_IMAGE_A}" "${TMP_MNT}"
+
+# Arrange for loopback and eth0 to load automatically,
+# and for eth0 to have our desired network parameters.
+cat > "${TMP_MNT}/etc/network/interfaces" <<!
+# Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
+# /usr/share/doc/ifupdown/examples for more information.
+auto lo
+iface lo inet loopback
+auto eth0
+# iface eth0 inet dhcp
+iface eth0 inet static
+ address ${GUEST_IP}
+ netmask ${NETMASK}
+ broadcast ${BROADCAST}
+ gateway ${HOST_IP}
+!
+
+# Have the guest start with an appropriate host name.
+# Also record an entry for it in its own hosts file.
+echo "${GUEST_HOSTNAME}" > "${TMP_MNT}/etc/hostname"
+echo "${GUEST_IP} ${GUEST_HOSTNAME}" >> "${TMP_MNT}/etc/hosts"
+
+# The host will serve as the name server also
+cat > "${TMP_MNT}/etc/resolv.conf" <<!
+nameserver ${HOST_IP}
+!
+
+# OK, done tweaking the boot image.
+sync
+umount "${DISK_IMAGE_A}"
+rmdir "${TMP_MNT}"
+
+# Set up a config file for "ifup" and "ifdown" (on the host) to use.
+# All the backslashes below are needed because we're sitting inside
+# a double here-document...
+cat > "${TAP_IFUPDOWN_CONFIG}" <<!
+iface ${TAP} inet manual
+ up brctl addif virbr0 "\\\${IFACE}"
+ up ip link set dev "\\\${IFACE}" up
+ pre-down brctl delif virbr0 "\\\${IFACE}"
+ pre-down ip link del dev "\\\${IFACE}"
+ tunctl_user $(whoami)
+!
+
+# OK, bring up the tap device using our config file
+ifup -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}"
+
+EnD_Of_sUdO
+
+# Finally ready to launch the UML instance.
+./linux \
+ umid="${GUEST_HOSTNAME}" \
+ ubda="${DISK_IMAGE_A}" \
+ eth0="tuntap,${TAP}" \
+ mem=1024M
+
+# When we're done, clean up. Bring down the tap interface and
+# delete the config file.
+#
+# Note that if the above "./linux" crashes, you'll need to run the
+# following commands manually in order to clean up state.
+sudo ifdown -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}"
+sudo rm -f "${TAP_IFUPDOWN_CONFIG}"
+
+exit 0
Code Review / stor4nfv.git / blobdiff