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
46import sys
47import socket
48import struct
49import collections
50import ConfigParser
51
52FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
53
54# Protocol constants
55NBD_CMD_READ = 0
56NBD_CMD_WRITE = 1
57NBD_CMD_DISC = 2
58NBD_REQUEST_MAGIC = 0x25609513
59NBD_SIMPLE_REPLY_MAGIC = 0x67446698
60NBD_PASSWD = 0x4e42444d41474943
61NBD_OPTS_MAGIC = 0x49484156454F5054
62NBD_CLIENT_MAGIC = 0x0000420281861253
63NBD_OPT_EXPORT_NAME = 1 << 0
64
65# Protocol structs
66neg_classic_struct = struct.Struct('>QQQI124x')
67neg1_struct = struct.Struct('>QQH')
68export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
69export_struct = struct.Struct('>IQII')
70neg2_struct = struct.Struct('>QH124x')
71request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
72request_struct = struct.Struct('>IIQQI')
73reply_struct = struct.Struct('>IIQ')
74
75def err(msg):
76    sys.stderr.write(msg + '\n')
77    sys.exit(1)
78
79def 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 ''.join(chunks)
89
90class 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
104class 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                    sys.exit(0)
115                if rule.when != -1:
116                    return rule.when
117        return bufsize
118
119    def send(self, buf, event):
120        bufsize = self.check(event, 'write', bufsize=len(buf))
121        self.sock.sendall(buf[:bufsize])
122        self.check(event, 'write')
123
124    def recv(self, bufsize, event):
125        bufsize = self.check(event, 'read', bufsize=bufsize)
126        data = recvall(self.sock, bufsize)
127        self.check(event, 'read')
128        return data
129
130    def close(self):
131        self.sock.close()
132
133def negotiate_classic(conn):
134    buf = neg_classic_struct.pack(NBD_PASSWD, NBD_CLIENT_MAGIC,
135                                  FAKE_DISK_SIZE, 0)
136    conn.send(buf, event='neg-classic')
137
138def negotiate_export(conn):
139    # Send negotiation part 1
140    buf = neg1_struct.pack(NBD_PASSWD, NBD_OPTS_MAGIC, 0)
141    conn.send(buf, event='neg1')
142
143    # Receive export option
144    buf = conn.recv(export_struct.size, event='export')
145    export = export_tuple._make(export_struct.unpack(buf))
146    assert export.magic == NBD_OPTS_MAGIC
147    assert export.opt == NBD_OPT_EXPORT_NAME
148    name = conn.recv(export.len, event='export-name')
149
150    # Send negotiation part 2
151    buf = neg2_struct.pack(FAKE_DISK_SIZE, 0)
152    conn.send(buf, event='neg2')
153
154def negotiate(conn, use_export):
155    '''Negotiate export with client'''
156    if use_export:
157        negotiate_export(conn)
158    else:
159        negotiate_classic(conn)
160
161def read_request(conn):
162    '''Parse NBD request from client'''
163    buf = conn.recv(request_struct.size, event='request')
164    req = request_tuple._make(request_struct.unpack(buf))
165    assert req.magic == NBD_REQUEST_MAGIC
166    return req
167
168def write_reply(conn, error, handle):
169    buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
170    conn.send(buf, event='reply')
171
172def handle_connection(conn, use_export):
173    negotiate(conn, use_export)
174    while True:
175        req = read_request(conn)
176        if req.type == NBD_CMD_READ:
177            write_reply(conn, 0, req.handle)
178            conn.send('\0' * req.len, event='data')
179        elif req.type == NBD_CMD_WRITE:
180            _ = conn.recv(req.len, event='data')
181            write_reply(conn, 0, req.handle)
182        elif req.type == NBD_CMD_DISC:
183            break
184        else:
185            print 'unrecognized command type %#02x' % req.type
186            break
187    conn.close()
188
189def run_server(sock, rules, use_export):
190    while True:
191        conn, _ = sock.accept()
192        handle_connection(FaultInjectionSocket(conn, rules), use_export)
193
194def parse_inject_error(name, options):
195    if 'event' not in options:
196        err('missing \"event\" option in %s' % name)
197    event = options['event']
198    if event not in ('neg-classic', 'neg1', 'export', 'neg2', 'request', 'reply', 'data'):
199        err('invalid \"event\" option value \"%s\" in %s' % (event, name))
200    io = options.get('io', 'readwrite')
201    if io not in ('read', 'write', 'readwrite'):
202        err('invalid \"io\" option value \"%s\" in %s' % (io, name))
203    when = options.get('when', 'before')
204    try:
205        when = int(when)
206    except ValueError:
207        if when == 'before':
208            when = 0
209        elif when == 'after':
210            when = -1
211        else:
212            err('invalid \"when\" option value \"%s\" in %s' % (when, name))
213    return Rule(name, event, io, when)
214
215def parse_config(config):
216    rules = []
217    for name in config.sections():
218        if name.startswith('inject-error'):
219            options = dict(config.items(name))
220            rules.append(parse_inject_error(name, options))
221        else:
222            err('invalid config section name: %s' % name)
223    return rules
224
225def load_rules(filename):
226    config = ConfigParser.RawConfigParser()
227    with open(filename, 'rt') as f:
228        config.readfp(f, filename)
229    return parse_config(config)
230
231def open_socket(path):
232    '''Open a TCP or UNIX domain listen socket'''
233    if ':' in path:
234        host, port = path.split(':', 1)
235        sock = socket.socket()
236        sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
237        sock.bind((host, int(port)))
238
239        # If given port was 0 the final port number is now available
240        path = '%s:%d' % sock.getsockname()
241    else:
242        sock = socket.socket(socket.AF_UNIX)
243        sock.bind(path)
244    sock.listen(0)
245    print 'Listening on %s' % path
246    sys.stdout.flush() # another process may be waiting, show message now
247    return sock
248
249def usage(args):
250    sys.stderr.write('usage: %s [--classic-negotiation] <tcp-port>|<unix-path> <config-file>\n' % args[0])
251    sys.stderr.write('Run an fault injector NBD server with rules defined in a config file.\n')
252    sys.exit(1)
253
254def main(args):
255    if len(args) != 3 and len(args) != 4:
256        usage(args)
257    use_export = True
258    if args[1] == '--classic-negotiation':
259        use_export = False
260    elif len(args) == 4:
261        usage(args)
262    sock = open_socket(args[1 if use_export else 2])
263    rules = load_rules(args[2 if use_export else 3])
264    run_server(sock, rules, use_export)
265    return 0
266
267if __name__ == '__main__':
268    sys.exit(main(sys.argv))
269