Re: [PATCH] Provide family and protocol to make getaddrinfo happy

[Lutz Jaenicke <ljaenicke@innominate.com>]

On Wed, May 25, 2011 at 02:31:05PM +0200, Jan Engelhardt wrote:
> On Wednesday 2011-05-25 14:16, Lutz Jaenicke wrote:
> 
> >getaddrinfo() will fail for numeric port numbers if neither
> >the socket type (stream/datagram) nor the protocol is
> >provided.
> >Since matches on ports only make sense if the protocol is known
> >we "just" have to derive the protocol number from the information
> >already collected.
> 
> Not quite; ports are also possible with -m ipvs and -m conntrack, which 
> do not require -p tcp/udp.
>
> 
> If someone speicifies a numeric port to getaddrinfo, I just want the 
> thing encoded in struct sockaddr_XX.sXX_port - it does not need to know 
> the particular L4 proto, or the service's text-based name to do that - 
> which is most likely why glibc allows it.

Manual pages may not be the ultimate reference about the reasoning
on why something is implemented which way. Nevertheless let's see:

       Given node and service, which identify an Internet host and a  service,
       getaddrinfo()  returns  one  or more addrinfo structures, each of which
       contains an Internet address that can be specified in a call to bind(2)
       or  connect(2).

Taking this information "as is" actually means that using getaddrinfo()
the way it is done is at least stretching the functionality...

As I wrote in my introduction for the patch (which has not yet made it to the
mailing list), other C libraries behave like uClibc:
* http://gitorious.org/0xdroid/bionic/blobs/9ab75d4cc803e91b7f1b656ffbe2ad32c52a86f9/libc/netbsd/net/getaddrinfo.c                                                
  -> look for "ANDROID-SPECIFIC CHANGE TO MATCH GLIBC" :-)
* http://www.freebsd.org/cgi/query-pr.cgi?pr=51827
* Especially I like
  http://www.openbsd.org/cgi-bin/cvsweb/~checkout~/src/lib/libc/net/getaddrinfo.c?rev=1.72;content-type=text%2Fplain
  which in the text says 
	/*
	 * check for special cases.  (1) numeric servname is disallowed if
	 * socktype/protocol are left unspecified. (2) servname is disallowed
	 * for raw and other inet{,6} sockets.
	 */
  (and I took this as a reference until now) but later in get_portmatch():
  	case SOCK_DGRAM:
	case SOCK_STREAM:
	case ANY:
		allownumeric = 1;

> I would like to have an opinion on that from µclibc preferably..

Seems uClibc is outdated wrt adjusting the behavior with other C libraries...

Best regards,
	Lutz
-- 
Dr.-Ing. Lutz Jänicke
CTO
Innominate Security Technologies AG  /protecting industrial networks/
tel: +49.30.921028-200
fax: +49.30.921028-020
Rudower Chaussee 13
D-12489 Berlin, Germany
www.innominate.com

Register Court: AG Charlottenburg, HR B 81603
Management Board: Dirk Seewald
Chairman of the Supervisory Board: Volker Bibelhausen
--
To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html