tests/qemu-iotests/nbd-fault-injector.py

   1 #!/usr/bin/env python
   2 # NBD server - fault injection utility
   3 #
   4 # Configuration file syntax:
   5 #   [inject-error "disconnect-neg1"]
   6 #   event=neg1
   7 #   io=readwrite
   8 #   when=before
   9 #
  10 # Note that Python's ConfigParser squashes together all sections with the same
  11 # name, so give each [inject-error] a unique name.
  12 #
  13 # inject-error options:
  14 #   event - name of the trigger event
  15 #           "neg1" - first part of negotiation struct
  16 #           "export" - export struct
  17 #           "neg2" - second part of negotiation struct
  18 #           "request" - NBD request struct
  19 #           "reply" - NBD reply struct
  20 #           "data" - request/reply data
  21 #   io    - I/O direction that triggers this rule:
  22 #           "read", "write", or "readwrite"
  23 #           default: readwrite
  24 #   when  - after how many bytes to inject the fault
  25 #           -1 - inject error after I/O
  26 #           0 - inject error before I/O
  27 #           integer - inject error after integer bytes
  28 #           "before" - alias for 0
  29 #           "after" - alias for -1
  30 #           default: before
  31 #
  32 # Currently the only error injection action is to terminate the server process.
  33 # This resets the TCP connection and thus forces the client to handle
  34 # unexpected connection termination.
  35 #
  36 # Other error injection actions could be added in the future.
  37 #
  38 # Copyright Red Hat, Inc. 2014
  39 #
  40 # Authors:
  41 #   Stefan Hajnoczi <stefanha@redhat.com>
  42 #
  43 # This work is licensed under the terms of the GNU GPL, version 2 or later.
  44 # See the COPYING file in the top-level directory.
  45
  46 from __future__ import print_function
  47 import sys
  48 import socket
  49 import struct
  50 import collections
  51 import ConfigParser
  52
  53 FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
  54
  55 # Protocol constants
  56 NBD_CMD_READ = 0
  57 NBD_CMD_WRITE = 1
  58 NBD_CMD_DISC = 2
  59 NBD_REQUEST_MAGIC = 0x25609513
  60 NBD_SIMPLE_REPLY_MAGIC = 0x67446698
  61 NBD_PASSWD = 0x4e42444d41474943
  62 NBD_OPTS_MAGIC = 0x49484156454F5054
  63 NBD_CLIENT_MAGIC = 0x0000420281861253
  64 NBD_OPT_EXPORT_NAME = 1 << 0
  65
  66 # Protocol structs
  67 neg_classic_struct = struct.Struct('>QQQI124x')
  68 neg1_struct = struct.Struct('>QQH')
  69 export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
  70 export_struct = struct.Struct('>IQII')
  71 neg2_struct = struct.Struct('>QH124x')
  72 request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
  73 request_struct = struct.Struct('>IIQQI')
  74 reply_struct = struct.Struct('>IIQ')
  75
  76 def err(msg):
  77     sys.stderr.write(msg + '\n')
  78     sys.exit(1)
  79
  80 def recvall(sock, bufsize):
  81     received = 0
  82     chunks = []
  83     while received < bufsize:
  84         chunk = sock.recv(bufsize - received)
  85         if len(chunk) == 0:
  86             raise Exception('unexpected disconnect')
  87         chunks.append(chunk)
  88         received += len(chunk)
  89     return ''.join(chunks)
  90
  91 class Rule(object):
  92     def __init__(self, name, event, io, when):
  93         self.name = name
  94         self.event = event
  95         self.io = io
  96         self.when = when
  97
  98     def match(self, event, io):
  99         if event != self.event:
 100             return False
 101         if io != self.io and self.io != 'readwrite':
 102             return False
 103         return True
 104
 105 class FaultInjectionSocket(object):
 106     def __init__(self, sock, rules):
 107         self.sock = sock
 108         self.rules = rules
 109
 110     def check(self, event, io, bufsize=None):
 111         for rule in self.rules:
 112             if rule.match(event, io):
 113                 if rule.when == 0 or bufsize is None:
 114                     print('Closing connection on rule match %s' % rule.name)
 115                     sys.exit(0)
 116                 if rule.when != -1:
 117                     return rule.when
 118         return bufsize
 119
 120     def send(self, buf, event):
 121         bufsize = self.check(event, 'write', bufsize=len(buf))
 122         self.sock.sendall(buf[:bufsize])
 123         self.check(event, 'write')
 124
 125     def recv(self, bufsize, event):
 126         bufsize = self.check(event, 'read', bufsize=bufsize)
 127         data = recvall(self.sock, bufsize)
 128         self.check(event, 'read')
 129         return data
 130
 131     def close(self):
 132         self.sock.close()
 133
 134 def negotiate_classic(conn):
 135     buf = neg_classic_struct.pack(NBD_PASSWD, NBD_CLIENT_MAGIC,
 136                                   FAKE_DISK_SIZE, 0)
 137     conn.send(buf, event='neg-classic')
 138
 139 def negotiate_export(conn):
 140     # Send negotiation part 1
 141     buf = neg1_struct.pack(NBD_PASSWD, NBD_OPTS_MAGIC, 0)
 142     conn.send(buf, event='neg1')
 143
 144     # Receive export option
 145     buf = conn.recv(export_struct.size, event='export')
 146     export = export_tuple._make(export_struct.unpack(buf))
 147     assert export.magic == NBD_OPTS_MAGIC
 148     assert export.opt == NBD_OPT_EXPORT_NAME
 149     name = conn.recv(export.len, event='export-name')
 150
 151     # Send negotiation part 2
 152     buf = neg2_struct.pack(FAKE_DISK_SIZE, 0)
 153     conn.send(buf, event='neg2')
 154
 155 def negotiate(conn, use_export):
 156     '''Negotiate export with client'''
 157     if use_export:
 158         negotiate_export(conn)
 159     else:
 160         negotiate_classic(conn)
 161
 162 def read_request(conn):
 163     '''Parse NBD request from client'''
 164     buf = conn.recv(request_struct.size, event='request')
 165     req = request_tuple._make(request_struct.unpack(buf))
 166     assert req.magic == NBD_REQUEST_MAGIC
 167     return req
 168
 169 def write_reply(conn, error, handle):
 170     buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
 171     conn.send(buf, event='reply')
 172
 173 def handle_connection(conn, use_export):
 174     negotiate(conn, use_export)
 175     while True:
 176         req = read_request(conn)
 177         if req.type == NBD_CMD_READ:
 178             write_reply(conn, 0, req.handle)
 179             conn.send('\0' * req.len, event='data')
 180         elif req.type == NBD_CMD_WRITE:
 181             _ = conn.recv(req.len, event='data')
 182             write_reply(conn, 0, req.handle)
 183         elif req.type == NBD_CMD_DISC:
 184             break
 185         else:
 186             print('unrecognized command type %#02x' % req.type)
 187             break
 188     conn.close()
 189
 190 def run_server(sock, rules, use_export):
 191     while True:
 192         conn, _ = sock.accept()
 193         handle_connection(FaultInjectionSocket(conn, rules), use_export)
 194
 195 def parse_inject_error(name, options):
 196     if 'event' not in options:
 197         err('missing \"event\" option in %s' % name)
 198     event = options['event']
 199     if event not in ('neg-classic', 'neg1', 'export', 'neg2', 'request', 'reply', 'data'):
 200         err('invalid \"event\" option value \"%s\" in %s' % (event, name))
 201     io = options.get('io', 'readwrite')
 202     if io not in ('read', 'write', 'readwrite'):
 203         err('invalid \"io\" option value \"%s\" in %s' % (io, name))
 204     when = options.get('when', 'before')
 205     try:
 206         when = int(when)
 207     except ValueError:
 208         if when == 'before':
 209             when = 0
 210         elif when == 'after':
 211             when = -1
 212         else:
 213             err('invalid \"when\" option value \"%s\" in %s' % (when, name))
 214     return Rule(name, event, io, when)
 215
 216 def parse_config(config):
 217     rules = []
 218     for name in config.sections():
 219         if name.startswith('inject-error'):
 220             options = dict(config.items(name))
 221             rules.append(parse_inject_error(name, options))
 222         else:
 223             err('invalid config section name: %s' % name)
 224     return rules
 225
 226 def load_rules(filename):
 227     config = ConfigParser.RawConfigParser()
 228     with open(filename, 'rt') as f:
 229         config.readfp(f, filename)
 230     return parse_config(config)
 231
 232 def open_socket(path):
 233     '''Open a TCP or UNIX domain listen socket'''
 234     if ':' in path:
 235         host, port = path.split(':', 1)
 236         sock = socket.socket()
 237         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 238         sock.bind((host, int(port)))
 239
 240         # If given port was 0 the final port number is now available
 241         path = '%s:%d' % sock.getsockname()
 242     else:
 243         sock = socket.socket(socket.AF_UNIX)
 244         sock.bind(path)
 245     sock.listen(0)
 246     print('Listening on %s' % path)
 247     sys.stdout.flush() # another process may be waiting, show message now
 248     return sock
 249
 250 def usage(args):
 251     sys.stderr.write('usage: %s [--classic-negotiation] <tcp-port>|<unix-path> <config-file>\n' % args[0])
 252     sys.stderr.write('Run an fault injector NBD server with rules defined in a config file.\n')
 253     sys.exit(1)
 254
 255 def main(args):
 256     if len(args) != 3 and len(args) != 4:
 257         usage(args)
 258     use_export = True
 259     if args[1] == '--classic-negotiation':
 260         use_export = False
 261     elif len(args) == 4:
 262         usage(args)
 263     sock = open_socket(args[1 if use_export else 2])
 264     rules = load_rules(args[2 if use_export else 3])
 265     run_server(sock, rules, use_export)
 266     return 0
 267
 268 if __name__ == '__main__':
 269     sys.exit(main(sys.argv))