Refactor and enhance firecracker script

This patch:
- refactors firecracker.py to better handle error scenarios
- adds ability to use external networking bridge through -b parameter (see scripts/setup-external-bridge.sh)
- adds ability to specify custom location of kernel and image files

Signed-off-by: Waldemar Kozaczuk <[email protected]>

Author: wkozaczuk

scripts/firecracker.py

@@ -103,17 +103,29 @@ def print_time(msg):
         print("%s: %s" % (now.isoformat(), msg))
 
 
-def setup_tap_interface(tap_interface_name, tap_ip):
+def setup_tap_interface(tap_interface_name, tap_ip, bridge_name):
     # Setup tun tap interface if does not exist
-    tuntap_interfaces = subprocess.check_output(["ip", 'tuntap'])
+    # sudo ip link delete fc_tap0 - this deletes the tap device
+    tuntap_interfaces = subprocess.check_output(['ip', 'tuntap'])
     if tuntap_interfaces.find(tap_interface_name) < 0:
-        print("The tap interface %s not found!. Needs to set it up" % tap_interface_name)
+        print("The tap interface %s not found -> needs to set it up!" % tap_interface_name)
+        # Check if the bridge exists if user specified it
+        if bridge_name:
+            bridges = subprocess.check_output(['brctl', 'show'])
+            if bridges.find(bridge_name) < 0:
+                print("The bridge %s does not exist per brctl. Please create one!" % bridge_name)
+                exit(-1)
+
         subprocess.call(['sudo', 'ip', 'tuntap', 'add', 'dev', tap_interface_name, 'mode', 'tap'])
-        subprocess.call(['sudo', 'sysctl', '-w', 'net.ipv4.conf.%s.proxy_arp=1' % tap_interface_name])
-        subprocess.call(['sudo', 'sysctl', '-w', 'net.ipv6.conf.%s.disable_ipv6=1' % tap_interface_name])
-        subprocess.call(['sudo', 'ip', 'addr', 'add', '%s/30' % tap_ip, 'dev', tap_interface_name])
+        subprocess.call(['sudo', 'sysctl', '-q', '-w', 'net.ipv4.conf.%s.proxy_arp=1' % tap_interface_name])
+        subprocess.call(['sudo', 'sysctl', '-q', '-w', 'net.ipv6.conf.%s.disable_ipv6=1' % tap_interface_name])
         subprocess.call(['sudo', 'ip', 'link', 'set', 'dev', tap_interface_name, 'up'])
 
+        if bridge_name:
+            subprocess.call(['sudo', 'brctl', 'addif', bridge_name, tap_interface_name])
+        else:
+            subprocess.call(['sudo', 'ip', 'addr', 'add', '%s/30' % tap_ip, 'dev', tap_interface_name])
+
 
 def find_firecracker(dirname):
     firecracker_path = os.path.join(dirname, '../.firecracker/firecracker')
@@ -148,9 +160,9 @@ def find_firecracker(dirname):
     return firecracker_path
 
 
-def disk_path(dirname):
-    qcow_disk_path = os.path.join(dirname, '../build/release/usr.img')
-    raw_disk_path = os.path.join(dirname, '../build/release/usr.raw')
+def disk_path(qcow_disk_path):
+    dot_pos = qcow_disk_path.rfind('.')
+    raw_disk_path = qcow_disk_path[0:dot_pos] + '.raw'
 
     # Firecracker is not able to use disk image files in QCOW format
     # so we have to convert usr.img to raw format if the raw disk is missing
@@ -196,13 +208,30 @@ def main(options):
     firecracker = start_firecracker(firecracker_path, socket_path)
 
     # Prepare arguments we are going to pass when creating VM instance
-    kernel_path = os.path.join(dirname, '../build/release/loader-stripped.elf')
-    raw_disk_path = disk_path(dirname)
+    kernel_path = options.kernel
+    if not kernel_path:
+       kernel_path = os.path.join(dirname, '../build/release/loader-stripped.elf')
+
+    qemu_disk_path = options.image
+    if not qemu_disk_path:
+       qemu_disk_path = os.path.join(dirname, '../build/release/usr.img')
+    raw_disk_path = disk_path(qemu_disk_path)
 
     cmdline = options.execute
     if not cmdline:
         with open(os.path.join(dirname, '../build/release/cmdline'), 'r') as f:
             cmdline = f.read()
+    cmdline = "--nopci %s" % cmdline
+
+    if options.networking:
+        tap_ip = '172.16.0.1'
+        setup_tap_interface('fc_tap0', tap_ip, options.bridge)
+        if not options.bridge:
+            client_ip = '172.16.0.2'
+            cmdline = '--ip=eth0,%s,255.255.255.252 --defaultgw=%s %s' % (client_ip, tap_ip, cmdline)
+
+    if options.verbose:
+        cmdline = '--verbose ' + cmdline
 
     # Create API client and make API calls
     client = ApiClient(socket_path.replace("/", "%2F"))
@@ -223,15 +252,8 @@ def main(options):
         client.add_disk(raw_disk_path)
         print_time("Added disk")
 
-        cmdline = "--nopci %s" % cmdline
         if options.networking:
-            tap_ip = '172.16.0.1'
-            setup_tap_interface('fc_tap0', tap_ip)
             client.add_network_interface('eth0', 'fc_tap0')
-            client_ip = '172.16.0.2'
-            cmdline = '--ip=eth0,%s,255.255.255.252 --defaultgw=%s %s' % (client_ip, tap_ip, cmdline)
-        if options.verbose:
-            cmdline = '--verbose ' + cmdline
 
         client.create_instance(kernel_path, cmdline)
         print_time("Created OSv VM with cmdline: %s" % cmdline)
@@ -263,8 +285,14 @@ def main(options):
                         help="specify memory: ex. 1G, 2G, ...")
     parser.add_argument("-e", "--execute", action="store", default=None, metavar="CMD",
                         help="overwrite command line")
+    parser.add_argument("-i", "--image", action="store", default=None, metavar="CMD",
+                        help="path to disk image file. defaults to ../build/release/usr.img")
+    parser.add_argument("-k", "--kernel", action="store", default=None, metavar="CMD",
+                        help="path to kernel loader file. defaults to ../build/release/loader-stripped.elf")
     parser.add_argument("-n", "--networking", action="store_true",
                         help="needs root to setup tap networking first time")
+    parser.add_argument("-b", "--bridge", action="store", default=None,
+                        help="bridge name for tap networking")
     parser.add_argument("-V", "--verbose", action="store_true",
                         help="pass --verbose to OSv, to display more debugging information on the console")