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
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 b''.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                    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
135def 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
140def 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
156def negotiate(conn, use_export):
157    '''Negotiate export with client'''
158    if use_export:
159        negotiate_export(conn)
160    else:
161        negotiate_classic(conn)
162
163def 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
170def write_reply(conn, error, handle):
171    buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
172    conn.send(buf, event='reply')
173
174def 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
191def run_server(sock, rules, use_export):
192    while True:
193        conn, _ = sock.accept()
194        handle_connection(FaultInjectionSocket(conn, rules), use_export)
195
196def 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
217def 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
227def 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
233def 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
251def 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
256def 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
269if __name__ == '__main__':
270    sys.exit(main(sys.argv))
271