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