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

   1 #!/usr/bin/env python3
   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 import sys
  47 import socket
  48 import struct
  49 import collections
  50 import configparser
  51
  52 FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
  53
  54 # Protocol constants
  55 NBD_CMD_READ = 0
  56 NBD_CMD_WRITE = 1
  57 NBD_CMD_DISC = 2
  58 NBD_REQUEST_MAGIC = 0x25609513
  59 NBD_SIMPLE_REPLY_MAGIC = 0x67446698
  60 NBD_PASSWD = 0x4e42444d41474943
  61 NBD_OPTS_MAGIC = 0x49484156454F5054
  62 NBD_CLIENT_MAGIC = 0x0000420281861253
  63 NBD_OPT_EXPORT_NAME = 1 << 0
  64
  65 # Protocol structs
  66 neg_classic_struct = struct.Struct('>QQQI124x')
  67 neg1_struct = struct.Struct('>QQH')
  68 export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
  69 export_struct = struct.Struct('>IQII')
  70 neg2_struct = struct.Struct('>QH124x')
  71 request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
  72 request_struct = struct.Struct('>IIQQI')
  73 reply_struct = struct.Struct('>IIQ')
  74
  75 def err(msg):
  76     sys.stderr.write(msg + '\n')
  77     sys.exit(1)
  78
  79 def recvall(sock, bufsize):
  80     received = 0
  81     chunks = []
  82     while received < bufsize:
  83         chunk = sock.recv(bufsize - received)
  84         if len(chunk) == 0:
  85             raise Exception('unexpected disconnect')
  86         chunks.append(chunk)
  87         received += len(chunk)
  88     return b''.join(chunks)
  89
  90 class Rule(object):
  91     def __init__(self, name, event, io, when):
  92         self.name = name
  93         self.event = event
  94         self.io = io
  95         self.when = when
  96
  97     def match(self, event, io):
  98         if event != self.event:
  99             return False
 100         if io != self.io and self.io != 'readwrite':
 101             return False
 102         return True
 103
 104 class FaultInjectionSocket(object):
 105     def __init__(self, sock, rules):
 106         self.sock = sock
 107         self.rules = rules
 108
 109     def check(self, event, io, bufsize=None):
 110         for rule in self.rules:
 111             if rule.match(event, io):
 112                 if rule.when == 0 or bufsize is None:
 113                     print('Closing connection on rule match %s' % rule.name)
 114                     self.sock.close()
 115                     sys.stdout.flush()
 116                     sys.exit(0)
 117                 if rule.when != -1:
 118                     return rule.when
 119         return bufsize
 120
 121     def send(self, buf, event):
 122         bufsize = self.check(event, 'write', bufsize=len(buf))
 123         self.sock.sendall(buf[:bufsize])
 124         self.check(event, 'write')
 125
 126     def recv(self, bufsize, event):
 127         bufsize = self.check(event, 'read', bufsize=bufsize)
 128         data = recvall(self.sock, bufsize)
 129         self.check(event, 'read')
 130         return data
 131
 132     def close(self):
 133         self.sock.close()
 134
 135 def negotiate_classic(conn):
 136     buf = neg_classic_struct.pack(NBD_PASSWD, NBD_CLIENT_MAGIC,
 137                                   FAKE_DISK_SIZE, 0)
 138     conn.send(buf, event='neg-classic')
 139
 140 def negotiate_export(conn):
 141     # Send negotiation part 1
 142     buf = neg1_struct.pack(NBD_PASSWD, NBD_OPTS_MAGIC, 0)
 143     conn.send(buf, event='neg1')
 144
 145     # Receive export option
 146     buf = conn.recv(export_struct.size, event='export')
 147     export = export_tuple._make(export_struct.unpack(buf))
 148     assert export.magic == NBD_OPTS_MAGIC
 149     assert export.opt == NBD_OPT_EXPORT_NAME
 150     name = conn.recv(export.len, event='export-name')
 151
 152     # Send negotiation part 2
 153     buf = neg2_struct.pack(FAKE_DISK_SIZE, 0)
 154     conn.send(buf, event='neg2')
 155
 156 def negotiate(conn, use_export):
 157     '''Negotiate export with client'''
 158     if use_export:
 159         negotiate_export(conn)
 160     else:
 161         negotiate_classic(conn)
 162
 163 def read_request(conn):
 164     '''Parse NBD request from client'''
 165     buf = conn.recv(request_struct.size, event='request')
 166     req = request_tuple._make(request_struct.unpack(buf))
 167     assert req.magic == NBD_REQUEST_MAGIC
 168     return req
 169
 170 def write_reply(conn, error, handle):
 171     buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
 172     conn.send(buf, event='reply')
 173
 174 def handle_connection(conn, use_export):
 175     negotiate(conn, use_export)
 176     while True:
 177         req = read_request(conn)
 178         if req.type == NBD_CMD_READ:
 179             write_reply(conn, 0, req.handle)
 180             conn.send(b'\0' * req.len, event='data')
 181         elif req.type == NBD_CMD_WRITE:
 182             _ = conn.recv(req.len, event='data')
 183             write_reply(conn, 0, req.handle)
 184         elif req.type == NBD_CMD_DISC:
 185             break
 186         else:
 187             print('unrecognized command type %#02x' % req.type)
 188             break
 189     conn.close()
 190
 191 def run_server(sock, rules, use_export):
 192     while True:
 193         conn, _ = sock.accept()
 194         handle_connection(FaultInjectionSocket(conn, rules), use_export)
 195
 196 def parse_inject_error(name, options):
 197     if 'event' not in options:
 198         err('missing \"event\" option in %s' % name)
 199     event = options['event']
 200     if event not in ('neg-classic', 'neg1', 'export', 'neg2', 'request', 'reply', 'data'):
 201         err('invalid \"event\" option value \"%s\" in %s' % (event, name))
 202     io = options.get('io', 'readwrite')
 203     if io not in ('read', 'write', 'readwrite'):
 204         err('invalid \"io\" option value \"%s\" in %s' % (io, name))
 205     when = options.get('when', 'before')
 206     try:
 207         when = int(when)
 208     except ValueError:
 209         if when == 'before':
 210             when = 0
 211         elif when == 'after':
 212             when = -1
 213         else:
 214             err('invalid \"when\" option value \"%s\" in %s' % (when, name))
 215     return Rule(name, event, io, when)
 216
 217 def parse_config(config):
 218     rules = []
 219     for name in config.sections():
 220         if name.startswith('inject-error'):
 221             options = dict(config.items(name))
 222             rules.append(parse_inject_error(name, options))
 223         else:
 224             err('invalid config section name: %s' % name)
 225     return rules
 226
 227 def load_rules(filename):
 228     config = configparser.RawConfigParser()
 229     with open(filename, 'rt') as f:
 230         config.read_file(f, filename)
 231     return parse_config(config)
 232
 233 def open_socket(path):
 234     '''Open a TCP or UNIX domain listen socket'''
 235     if ':' in path:
 236         host, port = path.split(':', 1)
 237         sock = socket.socket()
 238         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 239         sock.bind((host, int(port)))
 240
 241         # If given port was 0 the final port number is now available
 242         path = '%s:%d' % sock.getsockname()
 243     else:
 244         sock = socket.socket(socket.AF_UNIX)
 245         sock.bind(path)
 246     sock.listen(0)
 247     print('Listening on %s' % path)
 248     sys.stdout.flush() # another process may be waiting, show message now
 249     return sock
 250
 251 def usage(args):
 252     sys.stderr.write('usage: %s [--classic-negotiation] <tcp-port>|<unix-path> <config-file>\n' % args[0])
 253     sys.stderr.write('Run an fault injector NBD server with rules defined in a config file.\n')
 254     sys.exit(1)
 255
 256 def main(args):
 257     if len(args) != 3 and len(args) != 4:
 258         usage(args)
 259     use_export = True
 260     if args[1] == '--classic-negotiation':
 261         use_export = False
 262     elif len(args) == 4:
 263         usage(args)
 264     sock = open_socket(args[1 if use_export else 2])
 265     rules = load_rules(args[2 if use_export else 3])
 266     run_server(sock, rules, use_export)
 267     return 0
 268
 269 if __name__ == '__main__':
 270     sys.exit(main(sys.argv))