view mercurial/httpclient/socketutil.py @ 17774:0496d4f73cf4

obsolete: cheap detection of nullid as successors

Nullid as successors create multiple issues:

- Nullid revnum is -1, confusing algorithm that use revnum unless you add
  special handling in all of them.
- Nullid confuses "divergent" changeset detection and resolution. As you can't
  add any successors to Nullid without being in even more troubles

Fortunately, there is no good reason to use nullid as a successor. The only
sensible meaning of "succeed by nullid" is "dropped" and this meaning is already
covered by obsolescence marker with empty successors set.

However, letting some nullid successors to slip in may cause terrible damage in
such algorithm difficult to debug. So I prefer to perform and clear detection of
of such pathological changeset. We could be much smarter by cleaning up nullid
successors on the fly but it would be much for expensive. As core Mercurial does
not create any such changeset, I think it is fine to just abort when suspicious
situation is detected.

Earlier experimental version created such changesets, so there are some out
there.  The evolve extension added the necessary logic to clean up its mess.

# Copyright 2010, Google Inc.
# All rights reserved.
#
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions are
# met:
#
#     * Redistributions of source code must retain the above copyright
# notice, this list of conditions and the following disclaimer.
#     * Redistributions in binary form must reproduce the above
# copyright notice, this list of conditions and the following disclaimer
# in the documentation and/or other materials provided with the
# distribution.
#     * Neither the name of Google Inc. nor the names of its
# contributors may be used to endorse or promote products derived from
# this software without specific prior written permission.

# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
# "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
# LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
# A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
# OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
# DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
# THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
# (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
# OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
"""Abstraction to simplify socket use for Python < 2.6

This will attempt to use the ssl module and the new
socket.create_connection method, but fall back to the old
methods if those are unavailable.
"""
import logging
import socket

logger = logging.getLogger(__name__)

try:
    import ssl
    ssl.wrap_socket  # make demandimporters load the module
    have_ssl = True
except ImportError:
    import httplib
    import urllib2
    have_ssl = getattr(urllib2, 'HTTPSHandler', False)
    ssl = False


try:
    create_connection = socket.create_connection
except AttributeError:
    def create_connection(address):
        host, port = address
        msg = "getaddrinfo returns an empty list"
        sock = None
        for res in socket.getaddrinfo(host, port, 0,
                                      socket.SOCK_STREAM):
            af, socktype, proto, _canonname, sa = res
            try:
                sock = socket.socket(af, socktype, proto)
                logger.info("connect: (%s, %s)", host, port)
                sock.connect(sa)
            except socket.error, msg:
                logger.info('connect fail: %s %s', host, port)
                if sock:
                    sock.close()
                sock = None
                continue
            break
        if not sock:
            raise socket.error, msg
        return sock

if ssl:
    wrap_socket = ssl.wrap_socket
    CERT_NONE = ssl.CERT_NONE
    CERT_OPTIONAL = ssl.CERT_OPTIONAL
    CERT_REQUIRED = ssl.CERT_REQUIRED
else:
    class FakeSocket(httplib.FakeSocket):
        """Socket wrapper that supports SSL.
        """
        # backport the behavior from Python 2.6, which is to busy wait
        # on the socket instead of anything nice. Sigh.
        # See http://bugs.python.org/issue3890 for more info.
        def recv(self, buflen=1024, flags=0):
            """ssl-aware wrapper around socket.recv
            """
            if flags != 0:
                raise ValueError(
                    "non-zero flags not allowed in calls to recv() on %s" %
                    self.__class__)
            while True:
                try:
                    return self._ssl.read(buflen)
                except socket.sslerror, x:
                    if x.args[0] == socket.SSL_ERROR_WANT_READ:
                        continue
                    else:
                        raise x

    _PROTOCOL_SSLv23 = 2

    CERT_NONE = 0
    CERT_OPTIONAL = 1
    CERT_REQUIRED = 2

    def wrap_socket(sock, keyfile=None, certfile=None,
                server_side=False, cert_reqs=CERT_NONE,
                ssl_version=_PROTOCOL_SSLv23, ca_certs=None,
                do_handshake_on_connect=True,
                suppress_ragged_eofs=True):
        if cert_reqs != CERT_NONE and ca_certs:
            raise CertificateValidationUnsupported(
                'SSL certificate validation requires the ssl module'
                '(included in Python 2.6 and later.)')
        sslob = socket.ssl(sock)
        # borrow httplib's workaround for no ssl.wrap_socket
        sock = FakeSocket(sock, sslob)
        return sock


class CertificateValidationUnsupported(Exception):
    """Exception raised when cert validation is requested but unavailable."""
# no-check-code