[Patch] gethostbyname2 again

["Pierre A. Humblet" <pierre at phumblet dot no-ip dot org>]

Corinna,

OK, here we go again.

This version calls res_query and all the work is done in net.cc.
As discussed before that means a lot of work is wasted when using the 
Windows resolver.
   That will be improved later.
There is no progress on the issue of resolving local names (NetBIOS 
over TCP) for now,
    so it's not a perfect replacement for the native gethostbyname yet.

Misc nits and notes:
- Including resolv.h in net.cc causes havoc because it pulls in 
cygwin/in.h which conflicts
  with winsock2.h.   I worked around that by 
defining   _CYGWIN_IN_H  before including resolv.h
- Because of the above, asm/byteorder.h doesn't get pulled in either, 
and I couldn't use
  some ntoh macros (see memcpy4to6).
- I could have included asm/byteorder separately but that causes 
conflicts with the local ntoh
  definitions in net.cc.
- Because arpa/nameser.h is now pulled in,  IN6ADDRSZ etc are now 
defined, but in a way different
  from done in the snippet of code cut & pasted from bind. I didn't 
want to change that piece (in
  case you want to keep in intact for some reason) and I ended up 
undefining  IN6ADDRSZ etc .
-  There is a new helper function dn_length1 which logically belongs 
in minires.c, although it shouldn't
   be exported by the dll.  However if I place it in minires.c, then 
the linker doesn't find it.
   Fixing that probably involves some Makefile magic.
- I structured the code with a helper function gethostby_helper. That 
will make it very easy to support
   a gethostbyaddress some day, if needed.
- The helper function avoids using dup_ent (there is enough copying 
already). I created a new
   realloc_ent function, and call it from both dup_ent and the 
helper. That caused minor
   changes in the 4 versions of dup_ent, and I don't know exactly 
what format to use in the ChangeLog
- This  is much more complex than the first way of doing things. Needs testing!
- The patch is long, see the attachment. There is also a test program attached.

Pierre

2009-03-02  Pierre Humblet <Pierre.Humblet@ieee.org>

	* net.cc: define _CYGWIN_IN_H and include resolv.h.
	(realloc_ent): New function.
	(dup_ent): Remove dst argument and call realloc_ent.
	(memcpy4to6): New function.
	(dn_length1): New function.
	(gethostby_helper): New function.
	(gethostbyname2): New function.
	* cygwin.din: Export gethostbyname2.
	* libc/minires.c (get_options): Look for "inet6" and apply bounds
	to "retry" and "retrans".
	(res_ninit): Set the default options at the beginning.
	(dn_expand): Fix "off by one".

Attachment: gethostbyname2_b.diff
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Attachment: try_gethostbyname.c
Description: Binary data