id	summary	reporter	owner	description	type	status	milestone	component	version	severity	resolution	keywords	cc
8503	Cannot connect to localhost without global connectivity	Edward@…	chris_kohlhoff	"On Windows, if there are no network cards installed or they are all disabled, attempts to resolve localhost fail. The problem is that by default, the default value for the basic_resolver_query constructor's resolve_flags parameter is address_configured, which is AI_ADDRCONFIG on Windows. However, as implemented AI_ADDRCONFIG is actually detrimental, particularly for resolution of loopback and link-local addresses.

The rationale from the Google Chrome source code explains this. Here is the relevant snippet from !SystemHostResolverCall in [http://src.chromium.org/viewvc/chrome/trunk/src/net/dns/host_resolver_proc.cc host_resolver_proc.cc]:

{{{
#if defined(OS_WIN)
  // DO NOT USE AI_ADDRCONFIG ON WINDOWS.
  //
  // The following comment in <winsock2.h> is the best documentation I found
  // on AI_ADDRCONFIG for Windows:
  //   Flags used in ""hints"" argument to getaddrinfo()
  //       - AI_ADDRCONFIG is supported starting with Vista
  //       - default is AI_ADDRCONFIG ON whether the flag is set or not
  //         because the performance penalty in not having ADDRCONFIG in
  //         the multi-protocol stack environment is severe;
  //         this defaulting may be disabled by specifying the AI_ALL flag,
  //         in that case AI_ADDRCONFIG must be EXPLICITLY specified to
  //         enable ADDRCONFIG behavior
  //
  // Not only is AI_ADDRCONFIG unnecessary, but it can be harmful.  If the
  // computer is not connected to a network, AI_ADDRCONFIG causes getaddrinfo
  // to fail with WSANO_DATA (11004) for ""localhost"", probably because of the
  // following note on AI_ADDRCONFIG in the MSDN getaddrinfo page:
  //   The IPv4 or IPv6 loopback address is not considered a valid global
  //   address.
  // See http://crbug.com/5234.
  //
  // OpenBSD does not support it, either.
  hints.ai_flags = 0;
#else
  hints.ai_flags = AI_ADDRCONFIG;
#endif
}}}

The developers of [http://xcb.freedesktop.org/ XCB] arrived at a similar conclusion. See their discussion on [http://thread.gmane.org/gmane.comp.freedesktop.xcb/6973 Bug: Can’t connect to localhost without global connectivity].

Code using ASIO can work around this problem, but doing so would require platform-specific code and intricate knowledge of poorly documented platform-specific behavior."	Bugs	closed	To Be Determined	asio	Boost 1.53.0	Problem	invalid	localhost AI_ADDRCONFIG