271 lines
8.4 KiB
Python
Executable File
271 lines
8.4 KiB
Python
Executable File
#!/usr/bin/env python3
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# NBD server - fault injection utility
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#
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# Configuration file syntax:
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# [inject-error "disconnect-neg1"]
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# event=neg1
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# io=readwrite
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# when=before
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#
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# Note that Python's ConfigParser squashes together all sections with the same
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# name, so give each [inject-error] a unique name.
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#
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# inject-error options:
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# event - name of the trigger event
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# "neg1" - first part of negotiation struct
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# "export" - export struct
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# "neg2" - second part of negotiation struct
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# "request" - NBD request struct
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# "reply" - NBD reply struct
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# "data" - request/reply data
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# io - I/O direction that triggers this rule:
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# "read", "write", or "readwrite"
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# default: readwrite
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# when - after how many bytes to inject the fault
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# -1 - inject error after I/O
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# 0 - inject error before I/O
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# integer - inject error after integer bytes
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# "before" - alias for 0
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# "after" - alias for -1
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# default: before
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#
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# Currently the only error injection action is to terminate the server process.
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# This resets the TCP connection and thus forces the client to handle
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# unexpected connection termination.
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#
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# Other error injection actions could be added in the future.
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#
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# Copyright Red Hat, Inc. 2014
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#
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# Authors:
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# Stefan Hajnoczi <stefanha@redhat.com>
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#
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# This work is licensed under the terms of the GNU GPL, version 2 or later.
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# See the COPYING file in the top-level directory.
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import sys
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import socket
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import struct
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import collections
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import configparser
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FAKE_DISK_SIZE = 8 * 1024 * 1024 * 1024 # 8 GB
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# Protocol constants
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NBD_CMD_READ = 0
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NBD_CMD_WRITE = 1
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NBD_CMD_DISC = 2
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NBD_REQUEST_MAGIC = 0x25609513
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NBD_SIMPLE_REPLY_MAGIC = 0x67446698
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NBD_PASSWD = 0x4e42444d41474943
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NBD_OPTS_MAGIC = 0x49484156454F5054
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NBD_CLIENT_MAGIC = 0x0000420281861253
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NBD_OPT_EXPORT_NAME = 1 << 0
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# Protocol structs
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neg_classic_struct = struct.Struct('>QQQI124x')
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neg1_struct = struct.Struct('>QQH')
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export_tuple = collections.namedtuple('Export', 'reserved magic opt len')
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export_struct = struct.Struct('>IQII')
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neg2_struct = struct.Struct('>QH124x')
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request_tuple = collections.namedtuple('Request', 'magic type handle from_ len')
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request_struct = struct.Struct('>IIQQI')
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reply_struct = struct.Struct('>IIQ')
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def err(msg):
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sys.stderr.write(msg + '\n')
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sys.exit(1)
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def recvall(sock, bufsize):
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received = 0
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chunks = []
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while received < bufsize:
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chunk = sock.recv(bufsize - received)
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if len(chunk) == 0:
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raise Exception('unexpected disconnect')
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chunks.append(chunk)
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received += len(chunk)
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return b''.join(chunks)
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class Rule(object):
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def __init__(self, name, event, io, when):
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self.name = name
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self.event = event
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self.io = io
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self.when = when
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def match(self, event, io):
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if event != self.event:
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return False
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if io != self.io and self.io != 'readwrite':
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return False
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return True
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class FaultInjectionSocket(object):
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def __init__(self, sock, rules):
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self.sock = sock
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self.rules = rules
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def check(self, event, io, bufsize=None):
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for rule in self.rules:
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if rule.match(event, io):
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if rule.when == 0 or bufsize is None:
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print('Closing connection on rule match %s' % rule.name)
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self.sock.close()
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sys.stdout.flush()
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sys.exit(0)
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if rule.when != -1:
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return rule.when
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return bufsize
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def send(self, buf, event):
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bufsize = self.check(event, 'write', bufsize=len(buf))
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self.sock.sendall(buf[:bufsize])
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self.check(event, 'write')
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def recv(self, bufsize, event):
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bufsize = self.check(event, 'read', bufsize=bufsize)
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data = recvall(self.sock, bufsize)
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self.check(event, 'read')
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return data
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def close(self):
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self.sock.close()
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def negotiate_classic(conn):
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buf = neg_classic_struct.pack(NBD_PASSWD, NBD_CLIENT_MAGIC,
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FAKE_DISK_SIZE, 0)
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conn.send(buf, event='neg-classic')
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def negotiate_export(conn):
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# Send negotiation part 1
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buf = neg1_struct.pack(NBD_PASSWD, NBD_OPTS_MAGIC, 0)
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conn.send(buf, event='neg1')
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# Receive export option
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buf = conn.recv(export_struct.size, event='export')
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export = export_tuple._make(export_struct.unpack(buf))
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assert export.magic == NBD_OPTS_MAGIC
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assert export.opt == NBD_OPT_EXPORT_NAME
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name = conn.recv(export.len, event='export-name')
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# Send negotiation part 2
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buf = neg2_struct.pack(FAKE_DISK_SIZE, 0)
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conn.send(buf, event='neg2')
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def negotiate(conn, use_export):
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'''Negotiate export with client'''
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if use_export:
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negotiate_export(conn)
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else:
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negotiate_classic(conn)
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def read_request(conn):
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'''Parse NBD request from client'''
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buf = conn.recv(request_struct.size, event='request')
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req = request_tuple._make(request_struct.unpack(buf))
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assert req.magic == NBD_REQUEST_MAGIC
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return req
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def write_reply(conn, error, handle):
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buf = reply_struct.pack(NBD_SIMPLE_REPLY_MAGIC, error, handle)
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conn.send(buf, event='reply')
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def handle_connection(conn, use_export):
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negotiate(conn, use_export)
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while True:
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req = read_request(conn)
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if req.type == NBD_CMD_READ:
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write_reply(conn, 0, req.handle)
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conn.send(b'\0' * req.len, event='data')
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elif req.type == NBD_CMD_WRITE:
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_ = conn.recv(req.len, event='data')
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write_reply(conn, 0, req.handle)
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elif req.type == NBD_CMD_DISC:
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break
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else:
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print('unrecognized command type %#02x' % req.type)
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break
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conn.close()
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def run_server(sock, rules, use_export):
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while True:
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conn, _ = sock.accept()
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handle_connection(FaultInjectionSocket(conn, rules), use_export)
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def parse_inject_error(name, options):
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if 'event' not in options:
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err('missing \"event\" option in %s' % name)
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event = options['event']
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if event not in ('neg-classic', 'neg1', 'export', 'neg2', 'request', 'reply', 'data'):
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err('invalid \"event\" option value \"%s\" in %s' % (event, name))
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io = options.get('io', 'readwrite')
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if io not in ('read', 'write', 'readwrite'):
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err('invalid \"io\" option value \"%s\" in %s' % (io, name))
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when = options.get('when', 'before')
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try:
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when = int(when)
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except ValueError:
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if when == 'before':
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when = 0
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elif when == 'after':
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when = -1
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else:
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err('invalid \"when\" option value \"%s\" in %s' % (when, name))
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return Rule(name, event, io, when)
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def parse_config(config):
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rules = []
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for name in config.sections():
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if name.startswith('inject-error'):
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options = dict(config.items(name))
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rules.append(parse_inject_error(name, options))
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else:
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err('invalid config section name: %s' % name)
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return rules
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def load_rules(filename):
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config = configparser.RawConfigParser()
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with open(filename, 'rt') as f:
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config.read_file(f, filename)
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return parse_config(config)
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def open_socket(path):
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'''Open a TCP or UNIX domain listen socket'''
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if ':' in path:
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host, port = path.split(':', 1)
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sock = socket.socket()
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sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
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sock.bind((host, int(port)))
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# If given port was 0 the final port number is now available
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path = '%s:%d' % sock.getsockname()
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else:
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sock = socket.socket(socket.AF_UNIX)
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sock.bind(path)
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sock.listen(0)
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print('Listening on %s' % path)
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sys.stdout.flush() # another process may be waiting, show message now
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return sock
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def usage(args):
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sys.stderr.write('usage: %s [--classic-negotiation] <tcp-port>|<unix-path> <config-file>\n' % args[0])
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sys.stderr.write('Run an fault injector NBD server with rules defined in a config file.\n')
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sys.exit(1)
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def main(args):
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if len(args) != 3 and len(args) != 4:
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usage(args)
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use_export = True
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if args[1] == '--classic-negotiation':
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use_export = False
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elif len(args) == 4:
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usage(args)
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sock = open_socket(args[1 if use_export else 2])
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rules = load_rules(args[2 if use_export else 3])
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run_server(sock, rules, use_export)
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return 0
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if __name__ == '__main__':
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sys.exit(main(sys.argv))
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