[Bug 1154599] Re: dns lookup failure raises socket.error not socket.gaierror

[Barry Warsaw]

The problem is that getaddrinfo() returns different error codes on
Ubuntu.

On Wheezy, getaddrinfo() returns -2 with errno set to 2 (ENOENT).  On
Raring, getaddrinfo() returns -11 (EAI_SYSTEM) with errno also set to 2
(ENOENT).  Python has this bit of code to set the error type based on
the return value of getaddrinfo() -- see Modules/socketmodule.c:

static PyObject *
set_gaierror(int error)
{
    PyObject *v;

#ifdef EAI_SYSTEM
    /* EAI_SYSTEM is not available on Windows XP. */
    if (error == EAI_SYSTEM)
        return set_error();
#endif

#ifdef HAVE_GAI_STRERROR
    v = Py_BuildValue("(is)", error, gai_strerror(error));
#else
    v = Py_BuildValue("(is)", error, "getaddrinfo failed");
#endif
    if (v != NULL) {
        PyErr_SetObject(socket_gaierror, v);
        Py_DECREF(v);
    }

    return NULL;
}

So now it should be obvious why a different error type is getting raised
in Python (i.e. socket.error vs socket.gaierror).  This is likely a
change in glibc's getaddrinfo() and nothing to do with Python.

Wheezy has libc6 2.13-38, Raring has libc6 2.17-0ubuntu4

** Bug watch added: Sourceware.org Bugzilla #15272
   http://sourceware.org/bugzilla/show_bug.cgi?id=15272

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https://bugs.launchpad.net/bugs/1154599

Title:
  dns lookup failure raises socket.error not socket.gaierror

Status in Python:
  New
Status in “python2.7” package in Ubuntu:
  New

Bug description:
  $ cat lookup.py
  #!/usr/bin/python
  import sys, socket
  names = ["slashdot.org", "foooooooooowhizzzzzzzz.com"]
  if len(sys.argv) > 1:
     names = sys.argv[1:]
  for iname in names:
      try:
          result = socket.getaddrinfo(iname, None, 0, 0, socket.SOCK_STREAM,
                                      socket.AI_CANONNAME)
          for (fam, stype, proto, cname, sockaddr) in result:
              sys.stdout.write("cname=%s, sockaddr=%s\n" % (cname, sockaddr))
      except socket.gaierror as error:
          sys.stderr.write("%s failed lookup" % iname)

  $ python2.7 lookup.py
  cname=slashdot.org, sockaddr=('216.34.181.45', 0)
  Traceback (most recent call last):
    File "/tmp/x.py", line 10, in <module>
      socket.AI_CANONNAME)
  socket.error: [Errno 2] No such file or directory

  shell returned 1

  $ dpkg -S /usr/bin/python2.7
  python2.7-minimal: /usr/bin/python2.7
  $ dpkg-query --show python2.7-minimal
  python2.7-minimal	2.7.3-16ubuntu1

  This is a behavioral change from quantal (2.7.3-5ubuntu4).

  ProblemType: Bug
  DistroRelease: Ubuntu 13.04
  Package: python 2.7.3-10ubuntu5
  ProcVersionSignature: Ubuntu 3.5.0-21.32-generic 3.5.7.1
  Uname: Linux 3.5.0-21-generic x86_64
  ApportVersion: 2.9.1-0ubuntu1
  Architecture: amd64
  Date: Wed Mar 13 09:52:55 2013
  EcryptfsInUse: Yes
  InstallationDate: Installed on 2011-10-19 (511 days ago)
  InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
  MarkForUpload: True
  ProcEnviron:
   TERM=xterm
   PATH=(custom, no user)
   XDG_RUNTIME_DIR=<set>
   LANG=en_US.UTF-8
   SHELL=/bin/bash
  SourcePackage: python-defaults
  UpgradeStatus: Upgraded to raring on 2013-01-07 (64 days ago)

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