ceph/src/script/run_uml.sh

   1 #!/bin/bash -norc
   2
   3 # Magic startup script for a UML instance.  As long as unique
   4 # instances are started, more than one of them can be concurrently
   5 # in use on a single system.  All their network interfaces are
   6 # bridged together onto the virtual bridge "virbr0" which is
   7 # supplied by the "libvirt" package.
   8 #
   9 # Note that a DHCP server is started for that interface.  It's
  10 # configured in this file:
  11 #       /etc/libvirt/qemu/networks/default.xml
  12 # Unfortunately what I see there serves all possible DHCP addresses,
  13 # so stealing them like we do here isn't really kosher.  To fix
  14 # it, that configuration should change to serve a smaller subset
  15 # of the available address range.
  16 #
  17 # Each instance uses its own tun/tap device, created using the
  18 # "tunctl" command.  The assigned tap device will correspond with
  19 # the guest id (a small integer representing the instance), i.e.,
  20 # guest id 1 uses tap1, etc.  The tap device is attached to the
  21 # virtual bridge, which will have its own subnet associated with it.
  22 # The guest side of that interface will have the same subnet as the
  23 # bridge interface, with the bottom bits representing (normally) 100
  24 # more than the guest id.  So for subnet 192.168.122.0/24, guest
  25 # id 1 will use ip 192.168.122.101, guest id 2 will use ip
  26 # 192.168.122.102, and so on.  Because these interfaces are bridged,
  27 # they can all communicate with each other.
  28
  29 # You will want to override this by setting and exporting the
  30 # "CEPH_TOP" environment variable to be the directory that contains
  31 # the "ceph-client" source tree.
  32 CEPH_TOP="${CEPH_TOP:-/home/elder/ceph}"
  33
  34 # You may want to change this too, if you want guest UML instances
  35 # to have a diffeerent IP address range.  The guest IP will be based
  36 # on this plus GUEST_ID (defined below).
  37 GUEST_IP_OFFSET="${GUEST_IP_OFFSET:-100}"
  38
  39 #############################
  40
  41 if [ $# -gt 1 ]; then
  42         echo "" >&2
  43         echo "Usage: $(basename $0) [guest_id]" >&2
  44         echo "" >&2
  45         echo "    guest_id is a small integer (default 1)" >&2
  46         echo "    (each UML instance needs a distinct guest_id)" >&2
  47         echo "" >&2
  48         exit 1
  49 elif [ $# -eq 1 ]; then
  50         GUEST_ID="$1"
  51 else
  52         GUEST_ID=1
  53 fi
  54
  55 # This will be what the guest host calls itself.
  56 GUEST_HOSTNAME="uml-${GUEST_ID}"
  57
  58 # This is the path to the boot disk image used by UML.
  59 DISK_IMAGE_A="${CEPH_TOP}/ceph-client/uml.${GUEST_ID}"
  60 if [ ! -f "${DISK_IMAGE_A}" ]; then
  61         echo "root disk image not found (or not a file)" >&2
  62         exit 2
  63 fi
  64
  65 # Hostid 1 uses tun/tap device tap1, hostid 2 uses tap2, etc.
  66 TAP_ID="${GUEST_ID}"
  67 # This is the tap device used for this UML instance
  68 TAP="tap${TAP_ID}"
  69
  70 # This is just used to mount an image temporarily
  71 TMP_MNT="/tmp/m$$"
  72
  73 # Where to put a config file generated for this tap device
  74 TAP_IFUPDOWN_CONFIG="/tmp/interface-${TAP}"
  75
  76 # Compute the HOST_IP and BROADCAST address values to use,
  77 # and assign shell variables with those names to their values.
  78 # Also compute BITS, which is the network prefix length used.
  79 # The NETMASK is then computed using that BITS value.
  80 eval $(
  81 ip addr show virbr0 | awk '
  82 /inet/ {
  83         split($2, a, "/")
  84         printf("HOST_IP=%s\n", a[1]);
  85         printf("BROADCAST=%s\n", $4);
  86         printf("BITS=%s\n", a[2]);
  87         exit(0);
  88 }')
  89
  90 # Use bc to avoid 32-bit wrap when computing netmask
  91 eval $(
  92 echo -n "NETMASK="
  93 bc <<! | fmt | sed 's/ /./g'
  94 m = 2 ^ 32 - 2 ^ (32 - ${BITS})
  95 for (p = 24; p >= 0; p = p - 8)
  96     m / (2 ^ p) % 256
  97 !
  98 )
  99
 100 # Now use the netmask and the host IP to compute the subnet address
 101 # and from that the guest IP address to use.
 102 eval $(
 103 awk '
 104 function from_quad(addr,  a, val, i) {
 105         if (split(addr, a, ".") != 4)
 106                 exit(1);        # address not in dotted quad format
 107         val = 0;
 108         for (i = 1; i <= 4; i++)
 109                 val = val * 256 + a[i];
 110         return val;
 111 }
 112 function to_quad(val,  addr, i) {
 113         addr = "";
 114         for (i = 1; i <= 4; i++) {
 115                 addr = sprintf("%u%s%s", val % 256, i > 1 ? "." : "", addr);
 116                 val = int(val / 256);
 117         }
 118         if ((val + 0) != 0)
 119                 exit(1);        # value provided exceeded 32 bits
 120         return addr;
 121 }
 122 BEGIN {
 123         host_ip = from_quad("'${HOST_IP}'");
 124         netmask = from_quad("'${NETMASK}'");
 125         guest_net_ip = '${GUEST_IP_OFFSET}' + '${GUEST_ID}';
 126         if (and(netmask, guest_net_ip))
 127                 exit(1);        # address too big for subnet
 128         subnet = and(host_ip, netmask);
 129         guest_ip = or(subnet, guest_net_ip);
 130         if (guest_ip == host_ip)
 131                 exit(1);        # computed guest ip matches host ip
 132
 133         printf("SUBNET=%s\n", to_quad(subnet));
 134         printf("GUEST_IP=%s\n", to_quad(guest_ip));
 135 }
 136 ' < /dev/null
 137 )
 138
 139 ############## OK, we now know all our network parameters...
 140
 141 # There is a series of things that need to be done as superuser,
 142 # so group them all into one big (and sort of nested!) sudo request.
 143 sudo -s <<EnD_Of_sUdO
 144 # Mount the boot disk for the UML and set up some configuration
 145 # files there.
 146 mkdir -p "${TMP_MNT}"
 147 mount -o loop "${DISK_IMAGE_A}" "${TMP_MNT}"
 148
 149 # Arrange for loopback and eth0 to load automatically,
 150 # and for eth0 to have our desired network parameters.
 151 cat > "${TMP_MNT}/etc/network/interfaces" <<!
 152 # Used by ifup(8) and ifdown(8). See the interfaces(5) manpage or
 153 # /usr/share/doc/ifupdown/examples for more information.
 154 auto lo
 155 iface lo inet loopback
 156 auto eth0
 157 # iface eth0 inet dhcp
 158 iface eth0 inet static
 159         address ${GUEST_IP}
 160         netmask ${NETMASK}
 161         broadcast ${BROADCAST}
 162         gateway ${HOST_IP}
 163 !
 164
 165 # Have the guest start with an appropriate host name.
 166 # Also record an entry for it in its own hosts file.
 167 echo "${GUEST_HOSTNAME}" > "${TMP_MNT}/etc/hostname"
 168 echo "${GUEST_IP}       ${GUEST_HOSTNAME}" >> "${TMP_MNT}/etc/hosts"
 169
 170 # The host will serve as the name server also
 171 cat > "${TMP_MNT}/etc/resolv.conf" <<!
 172 nameserver ${HOST_IP}
 173 !
 174
 175 # OK, done tweaking the boot image.
 176 sync
 177 umount "${DISK_IMAGE_A}"
 178 rmdir "${TMP_MNT}"
 179
 180 # Set up a config file for "ifup" and "ifdown" (on the host) to use.
 181 # All the backslashes below are needed because we're sitting inside
 182 # a double here-document...
 183 cat > "${TAP_IFUPDOWN_CONFIG}" <<!
 184 iface ${TAP} inet manual
 185         up brctl addif virbr0 "\\\${IFACE}"
 186         up ip link set dev "\\\${IFACE}" up
 187         pre-down brctl delif virbr0 "\\\${IFACE}"
 188         pre-down ip link del dev "\\\${IFACE}"
 189         tunctl_user $(whoami)
 190 !
 191
 192 # OK, bring up the tap device using our config file
 193 ifup -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}"
 194
 195 EnD_Of_sUdO
 196
 197 # Finally ready to launch the UML instance.
 198 ./linux \
 199         umid="${GUEST_HOSTNAME}" \
 200         ubda="${DISK_IMAGE_A}" \
 201         eth0="tuntap,${TAP}" \
 202         mem=1024M
 203
 204 # When we're done, clean up.  Bring down the tap interface and
 205 # delete the config file.
 206 #
 207 # Note that if the above "./linux" crashes, you'll need to run the
 208 # following commands manually in order to clean up state.
 209 sudo ifdown -i "${TAP_IFUPDOWN_CONFIG}" "${TAP}"
 210 sudo rm -f "${TAP_IFUPDOWN_CONFIG}"
 211
 212 exit 0