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
46from __future__ import print_function
47import sys
48import socket
49import struct
50import collections
51import ConfigParser
52
53FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
54
55# Protocol constants
56NBD_CMD_READ = 0
57NBD_CMD_WRITE = 1
58NBD_CMD_DISC = 2
59NBD_REQUEST_MAGIC = 0x25609513
60NBD_SIMPLE_REPLY_MAGIC = 0x67446698
61NBD_PASSWD = 0x4e42444d41474943
62NBD_OPTS_MAGIC = 0x49484156454F5054
63NBD_CLIENT_MAGIC = 0x0000420281861253
64NBD_OPT_EXPORT_NAME = 1 << 0
65
66# Protocol structs
67neg_classic_struct = struct.Struct('>QQQI124x')
68neg1_struct = struct.Struct('>QQH')
69export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
70export_struct = struct.Struct('>IQII')
71neg2_struct = struct.Struct('>QH124x')
72request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
73request_struct = struct.Struct('>IIQQI')
74reply_struct = struct.Struct('>IIQ')
75
76def err(msg):
77    sys.stderr.write(msg + '\n')
78    sys.exit(1)
79
80def 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
91class 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
105class 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
134def 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
139def 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
155def negotiate(conn, use_export):
156    '''Negotiate export with client'''
157    if use_export:
158        negotiate_export(conn)
159    else:
160        negotiate_classic(conn)
161
162def 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
169def write_reply(conn, error, handle):
170    buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
171    conn.send(buf, event='reply')
172
173def 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
190def run_server(sock, rules, use_export):
191    while True:
192        conn, _ = sock.accept()
193        handle_connection(FaultInjectionSocket(conn, rules), use_export)
194
195def 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
216def 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
226def 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
232def 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
250def 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
255def 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
268if __name__ == '__main__':
269    sys.exit(main(sys.argv))
270