xen/tools/python/scripts/verify-stream-v2

#!/usr/bin/env python
# -*- coding: utf-8 -*-

""" Verify a v2 format migration stream """

import sys
import struct
import os, os.path
import syslog
import traceback

from xen.migration.verify import StreamError, RecordError
from xen.migration.libxc import VerifyLibxc
from xen.migration.libxl import VerifyLibxl

fin = None             # Input file/fd
log_to_syslog = False  # Boolean - Log to syslog instead of stdout/err?
verbose = False        # Boolean - Summarise stream contents
quiet = False          # Boolean - Suppress error printing

def info(msg):
    """Info message, routed to appropriate destination"""
    if not quiet and verbose:
        if log_to_syslog:
            for line in msg.split("\n"):
                syslog.syslog(syslog.LOG_INFO, line)
        else:
            print msg

def err(msg):
    """Error message, routed to appropriate destination"""
    if not quiet:
        if log_to_syslog:
            for line in msg.split("\n"):
                syslog.syslog(syslog.LOG_ERR, line)
        print >> sys.stderr, msg

def stream_read(_ = None):
    """Read from input"""
    return fin.read(_)

def rdexact(nr_bytes):
    """Read exactly nr_bytes from fin"""
    _ = stream_read(nr_bytes)
    if len(_) != nr_bytes:
        raise IOError("Stream truncated")
    return _

def unpack_exact(fmt):
    """Unpack a format from fin"""
    sz = struct.calcsize(fmt)
    return struct.unpack(fmt, rdexact(sz))


def skip_xl_header():
    """Skip over an xl header in the stream"""

    hdr = rdexact(32)
    if hdr != "Xen saved domain, xl format\n \0 \r":
        raise StreamError("No xl header")

    _, mflags, _, optlen = unpack_exact("=IIII")
    _ = rdexact(optlen)

    info("Processed xl header")

    if mflags & 2: # XL_MANDATORY_FLAG_STREAMv2
        return "libxl"
    else:
        return "libxc"

def read_stream(fmt):
    """ Read an entire stream """

    try:
        if fmt == "xl":
            fmt = skip_xl_header()

        if fmt == "libxc":
            VerifyLibxc(info, stream_read).verify()
        else:
            VerifyLibxl(info, stream_read).verify()

    except (IOError, StreamError, RecordError):
        err("Stream Error:")
        err(traceback.format_exc())
        return 1

    except StandardError:
        err("Script Error:")
        err(traceback.format_exc())
        err("Please fix me")
        return 2

    return 0

def open_file_or_fd(val, mode, buffering):
    """
    If 'val' looks like a decimal integer, open it as an fd.  If not, try to
    open it as a regular file.
    """

    fd = -1
    try:
        # Does it look like an integer?
        try:
            fd = int(val, 10)
        except ValueError:
            pass

        # Try to open it...
        if fd != -1:
            return os.fdopen(fd, mode, buffering)
        else:
            return open(val, mode, buffering)

    except StandardError, e:
        if fd != -1:
            err("Unable to open fd %d: %s: %s" %
                (fd, e.__class__.__name__, e))
        else:
            err("Unable to open file '%s': %s: %s" %
                (val, e.__class__.__name__, e))

    raise SystemExit(2)

def main():
    """ main """
    from optparse import OptionParser
    global fin, quiet, verbose

    # Change stdout to be line-buffered.
    sys.stdout = os.fdopen(sys.stdout.fileno(), 'w', 1)

    parser = OptionParser(usage = "%prog [options]",
                          description =
                          "Verify a stream according to the v2 spec")

    # Optional options
    parser.add_option("-i", "--in", dest = "fin", metavar = "<FD or FILE>",
                      default = "0",
                      help = "Stream to verify (defaults to stdin)")
    parser.add_option("-v", "--verbose", action = "store_true", default = False,
                      help = "Summarise stream contents")
    parser.add_option("-q", "--quiet", action = "store_true", default = False,
                      help = "Suppress all logging/errors")
    parser.add_option("-f", "--format", dest = "format",
                      metavar = "<libxc|libxl|xl>", default = "libxc",
                      choices = ["libxc", "libxl", "xl"],
                      help = "Format of the incoming stream (defaults to libxc)")
    parser.add_option("--syslog", action = "store_true", default = False,
                      help = "Log to syslog instead of stdout")

    opts, _ = parser.parse_args()

    if opts.syslog:
        global log_to_syslog

        syslog.openlog("verify-stream-v2", syslog.LOG_PID)
        log_to_syslog = True

    verbose = opts.verbose
    quiet = opts.quiet
    fin = open_file_or_fd(opts.fin, "rb", 0)

    return read_stream(opts.format)

if __name__ == "__main__":
    try:
        sys.exit(main())
    except SystemExit, e:
        sys.exit(e.code)
    except KeyboardInterrupt:
        sys.exit(2)