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 if sys.version_info.major >= 3:
  52     import configparser
  53 else:
  54     import ConfigParser as configparser
  55
  56 FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
  57
  58 # Protocol constants
  59 NBD_CMD_READ = 0
  60 NBD_CMD_WRITE = 1
  61 NBD_CMD_DISC = 2
  62 NBD_REQUEST_MAGIC = 0x25609513
  63 NBD_SIMPLE_REPLY_MAGIC = 0x67446698
  64 NBD_PASSWD = 0x4e42444d41474943
  65 NBD_OPTS_MAGIC = 0x49484156454F5054
  66 NBD_CLIENT_MAGIC = 0x0000420281861253
  67 NBD_OPT_EXPORT_NAME = 1 << 0
  68
  69 # Protocol structs
  70 neg_classic_struct = struct.Struct('>QQQI124x')
  71 neg1_struct = struct.Struct('>QQH')
  72 export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
  73 export_struct = struct.Struct('>IQII')
  74 neg2_struct = struct.Struct('>QH124x')
  75 request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
  76 request_struct = struct.Struct('>IIQQI')
  77 reply_struct = struct.Struct('>IIQ')
  78
  79 def err(msg):
  80     sys.stderr.write(msg + '\n')
  81     sys.exit(1)
  82
  83 def recvall(sock, bufsize):
  84     received = 0
  85     chunks = []
  86     while received < bufsize:
  87         chunk = sock.recv(bufsize - received)
  88         if len(chunk) == 0:
  89             raise Exception('unexpected disconnect')
  90         chunks.append(chunk)
  91         received += len(chunk)
  92     return b''.join(chunks)
  93
  94 class Rule(object):
  95     def __init__(self, name, event, io, when):
  96         self.name = name
  97         self.event = event
  98         self.io = io
  99         self.when = when
 100
 101     def match(self, event, io):
 102         if event != self.event:
 103             return False
 104         if io != self.io and self.io != 'readwrite':
 105             return False
 106         return True
 107
 108 class FaultInjectionSocket(object):
 109     def __init__(self, sock, rules):
 110         self.sock = sock
 111         self.rules = rules
 112
 113     def check(self, event, io, bufsize=None):
 114         for rule in self.rules:
 115             if rule.match(event, io):
 116                 if rule.when == 0 or bufsize is None:
 117                     print('Closing connection on rule match %s' % rule.name)
 118                     self.sock.flush()
 119                     sys.exit(0)
 120                 if rule.when != -1:
 121                     return rule.when
 122         return bufsize
 123
 124     def send(self, buf, event):
 125         bufsize = self.check(event, 'write', bufsize=len(buf))
 126         self.sock.sendall(buf[:bufsize])
 127         self.check(event, 'write')
 128
 129     def recv(self, bufsize, event):
 130         bufsize = self.check(event, 'read', bufsize=bufsize)
 131         data = recvall(self.sock, bufsize)
 132         self.check(event, 'read')
 133         return data
 134
 135     def close(self):
 136         self.sock.close()
 137
 138 def negotiate_classic(conn):
 139     buf = neg_classic_struct.pack(NBD_PASSWD, NBD_CLIENT_MAGIC,
 140                                   FAKE_DISK_SIZE, 0)
 141     conn.send(buf, event='neg-classic')
 142
 143 def negotiate_export(conn):
 144     # Send negotiation part 1
 145     buf = neg1_struct.pack(NBD_PASSWD, NBD_OPTS_MAGIC, 0)
 146     conn.send(buf, event='neg1')
 147
 148     # Receive export option
 149     buf = conn.recv(export_struct.size, event='export')
 150     export = export_tuple._make(export_struct.unpack(buf))
 151     assert export.magic == NBD_OPTS_MAGIC
 152     assert export.opt == NBD_OPT_EXPORT_NAME
 153     name = conn.recv(export.len, event='export-name')
 154
 155     # Send negotiation part 2
 156     buf = neg2_struct.pack(FAKE_DISK_SIZE, 0)
 157     conn.send(buf, event='neg2')
 158
 159 def negotiate(conn, use_export):
 160     '''Negotiate export with client'''
 161     if use_export:
 162         negotiate_export(conn)
 163     else:
 164         negotiate_classic(conn)
 165
 166 def read_request(conn):
 167     '''Parse NBD request from client'''
 168     buf = conn.recv(request_struct.size, event='request')
 169     req = request_tuple._make(request_struct.unpack(buf))
 170     assert req.magic == NBD_REQUEST_MAGIC
 171     return req
 172
 173 def write_reply(conn, error, handle):
 174     buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
 175     conn.send(buf, event='reply')
 176
 177 def handle_connection(conn, use_export):
 178     negotiate(conn, use_export)
 179     while True:
 180         req = read_request(conn)
 181         if req.type == NBD_CMD_READ:
 182             write_reply(conn, 0, req.handle)
 183             conn.send(b'\0' * req.len, event='data')
 184         elif req.type == NBD_CMD_WRITE:
 185             _ = conn.recv(req.len, event='data')
 186             write_reply(conn, 0, req.handle)
 187         elif req.type == NBD_CMD_DISC:
 188             break
 189         else:
 190             print('unrecognized command type %#02x' % req.type)
 191             break
 192     conn.close()
 193
 194 def run_server(sock, rules, use_export):
 195     while True:
 196         conn, _ = sock.accept()
 197         handle_connection(FaultInjectionSocket(conn, rules), use_export)
 198
 199 def parse_inject_error(name, options):
 200     if 'event' not in options:
 201         err('missing \"event\" option in %s' % name)
 202     event = options['event']
 203     if event not in ('neg-classic', 'neg1', 'export', 'neg2', 'request', 'reply', 'data'):
 204         err('invalid \"event\" option value \"%s\" in %s' % (event, name))
 205     io = options.get('io', 'readwrite')
 206     if io not in ('read', 'write', 'readwrite'):
 207         err('invalid \"io\" option value \"%s\" in %s' % (io, name))
 208     when = options.get('when', 'before')
 209     try:
 210         when = int(when)
 211     except ValueError:
 212         if when == 'before':
 213             when = 0
 214         elif when == 'after':
 215             when = -1
 216         else:
 217             err('invalid \"when\" option value \"%s\" in %s' % (when, name))
 218     return Rule(name, event, io, when)
 219
 220 def parse_config(config):
 221     rules = []
 222     for name in config.sections():
 223         if name.startswith('inject-error'):
 224             options = dict(config.items(name))
 225             rules.append(parse_inject_error(name, options))
 226         else:
 227             err('invalid config section name: %s' % name)
 228     return rules
 229
 230 def load_rules(filename):
 231     config = configparser.RawConfigParser()
 232     with open(filename, 'rt') as f:
 233         config.readfp(f, filename)
 234     return parse_config(config)
 235
 236 def open_socket(path):
 237     '''Open a TCP or UNIX domain listen socket'''
 238     if ':' in path:
 239         host, port = path.split(':', 1)
 240         sock = socket.socket()
 241         sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
 242         sock.bind((host, int(port)))
 243
 244         # If given port was 0 the final port number is now available
 245         path = '%s:%d' % sock.getsockname()
 246     else:
 247         sock = socket.socket(socket.AF_UNIX)
 248         sock.bind(path)
 249     sock.listen(0)
 250     print('Listening on %s' % path)
 251     sys.stdout.flush() # another process may be waiting, show message now
 252     return sock
 253
 254 def usage(args):
 255     sys.stderr.write('usage: %s [--classic-negotiation] <tcp-port>|<unix-path> <config-file>\n' % args[0])
 256     sys.stderr.write('Run an fault injector NBD server with rules defined in a config file.\n')
 257     sys.exit(1)
 258
 259 def main(args):
 260     if len(args) != 3 and len(args) != 4:
 261         usage(args)
 262     use_export = True
 263     if args[1] == '--classic-negotiation':
 264         use_export = False
 265     elif len(args) == 4:
 266         usage(args)
 267     sock = open_socket(args[1 if use_export else 2])
 268     rules = load_rules(args[2 if use_export else 3])
 269     run_server(sock, rules, use_export)
 270     return 0
 271
 272 if __name__ == '__main__':
 273     sys.exit(main(sys.argv))