Re: follow-up: discrepancy with POSIX
Ulrich Drepper [EMAIL PROTECTED] writes:
fd = socket(AT_INET6, ...)
connect(fd, ...some IPv6 address...)
struct sockaddr_in6 sin6 = { .sin6_family = AF_INET6 };
connect(fd, sin6, sizeof (sin6));
The standard way to undo connect is to use AF_UNSPEC. Code to handle
that for dgram sockets is there. It's the same code for v4 and v6.
-Andi
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Re: follow-up: discrepancy with POSIX
From: Ulrich Drepper [EMAIL PROTECTED] Date: Wed, 19 Sep 2007 08:21:47 -0700 If you think the POSIX spec is wrong (and can point to other implementations doing the same as Linux) let me know and I'll work on getting the spec changed. The whole AF_UNSPEC thing I'm almost certain comes from BSD, which has behaved that way for centuries. Someone needs to cull through Steven's Volume 2 to verify this, I'm too busy at the moment to do so myself. - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, 19 Sep 2007 09:15:10 -0700 (PDT) David Miller [EMAIL PROTECTED] wrote: From: Ulrich Drepper [EMAIL PROTECTED] Date: Wed, 19 Sep 2007 08:21:47 -0700 If you think the POSIX spec is wrong (and can point to other implementations doing the same as Linux) let me know and I'll work on getting the spec changed. The whole AF_UNSPEC thing I'm almost certain comes from BSD, which has behaved that way for centuries. We got it from the 1003.4g draft socket specification if I remember rightly. Its entirely plausible that got it from 4BSE. Alan - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: The standard way to undo connect is to use AF_UNSPEC. Code to handle that for dgram sockets is there. It's the same code for v4 and v6. I quoted the standard and it does not say anything about AF_UNSPEC. So you cannot simply make such broad statements. I also don't say that this behavior should be removed. It's certainly useful, very much so in fact. But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. I looked through Stevens TCP Illustrated Vol 2 and it seems not to mention resetting the address at all. The POSIX spec certainly got this text from .1g. I cannot test it on other systems. If somebody has access to some certified systems (and maybe others), write a bit of code which creates a DGRAM socket, connect to one address, call connect with a null address, then connect to another address (which likely has to use a different interface since otherwise the connect will just succeed, it seems). - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG8VMF2ijCOnn/RHQRAr9NAJwLxyql0kQnMGJNaPZlRGsuB6rGEACgog88 WIWAFhuBWsjps7PdbcoumUQ= =oLxP -END PGP SIGNATURE- - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
From: Ulrich Drepper [EMAIL PROTECTED] Date: Wed, 19 Sep 2007 09:49:09 -0700 But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. It just occured to me that AF_UNSPEC might be used simply because all zeros might be a valid real bindable address for some address family. And using AF_UNSPEC avoids that problem entirely. - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, Sep 19, 2007 at 09:49:09AM -0700, Ulrich Drepper wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: The standard way to undo connect is to use AF_UNSPEC. Code to handle that for dgram sockets is there. It's the same code for v4 and v6. I quoted the standard and it does not say anything about AF_UNSPEC. So you cannot simply make such broad statements. Ok standard was perhaps a poor choice of words. AF_UNSPEC used to be introduced long ago by Alan based on some early POSIX draft iirc. Also incidentially it's a null address: include/linux/socket.h:#define AF_UNSPEC0 But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. memset(sockaddr, 0, sizeof(sockaddr)) should give you AF_UNSPEC -Andi - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Ulrich Drepper wrote: Yes, but for IPv4/6 it's not an issue. Some implementations might handle all-zeros and the spec _currently_ calls for it. In this case an alignment would be good. Searching the web shows up this: http://developer.apple.com/documentation/Darwin/Reference/ManPages/man2/connect.2.html Datagram sockets may dissolve the association by connecting to an invalid address, such as a null address or an address with the address family set to AF_UNSPEC (the error EAFNOSUPPORT will be harmlessly returned). I.e., at least Apple implements both variants. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG8Vvu2ijCOnn/RHQRAsSfAJkBELtiNyul8wMOjVv1x7LfvDWw/ACfR0D0 cm+k1wfhCsT4GjbF3uac+eY= =nksN -END PGP SIGNATURE- - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, Sep 19, 2007 at 10:46:54AM -0700, Ulrich Drepper wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. memset(sockaddr, 0, sizeof(sockaddr)) should give you AF_UNSPEC But the spec calls for quotenull address for the protocol/quote. That means the family for the null address is the same as the family of the socket. Spec doesn't match traditional behaviour then. IPv4 0.0.0.0 is traditionally an synonym for old style all broadcast (255.255.255.255) on UDP/RAW and it's certainly possible to connect() to that. -Andi - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. memset(sockaddr, 0, sizeof(sockaddr)) should give you AF_UNSPEC But the spec calls for quotenull address for the protocol/quote. That means the family for the null address is the same as the family of the socket. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG8WCO2ijCOnn/RHQRAgtsAJ9qTFVj5QQbVG/hUflxo/6uPOfl4QCdHSX8 wi2GX7B0pht8VDaswYLqdpM= =sMSg -END PGP SIGNATURE- - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: Spec doesn't match traditional behaviour then. Well, determining whether that's the case is part of this exercise. IPv4 0.0.0.0 is traditionally an synonym for old style all broadcast (255.255.255.255) on UDP/RAW and it's certainly possible to connect() to that. Where do you get this from? And where is this implemented? I don't doubt it but I have to convince people to change the standard and possibly introduce incompatibility. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG8WQY2ijCOnn/RHQRAlsBAJ9qZRZXNN2VEy136MFIT1daHfju5ACdGiIW k0I5e2BGRjvjbJrrAwtehqo= =fX+i -END PGP SIGNATURE- - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, 19 Sep 2007 10:46:54 -0700 Ulrich Drepper [EMAIL PROTECTED] wrote: -BEGIN PGP SIGNED MESSAGE- Hash: SHA1 Andi Kleen wrote: But the spec calls for a null address to be used and that's in my understanding something different from using AF_UNSPEC. memset(sockaddr, 0, sizeof(sockaddr)) should give you AF_UNSPEC But the spec calls for quotenull address for the protocol/quote. That means the family for the null address is the same as the family of the socket. Which is a valid address in some protocols. If I remember rightly then appletalk net 0 node 0 port 0 is valid although I'd want to look in the book to check that - ditto AF_ECONET although I doubt anyone cares too much 8) Alan - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, Sep 19, 2007 at 11:02:00AM -0700, Ulrich Drepper wrote: on UDP/RAW and it's certainly possible to connect() to that. Where do you get this from? And where is this implemented? I don't Sorry it's actually loopback, not broadcast as implemented in Linux. In Linux it's implemented in ip_route_output_slow(). Essentially converted to 127.0.0.1 I think it's traditional BSD behaviour but couldn't find it on a quick look in FreeBSD source (but haven't looked very intensively) Admittedly port 0 is somewhat dodgy for UDP too, but at least in RAW context it might be valid. -Andi - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
Andi Kleen wrote: On Wed, Sep 19, 2007 at 11:02:00AM -0700, Ulrich Drepper wrote: on UDP/RAW and it's certainly possible to connect() to that. Where do you get this from? And where is this implemented? I don't Sorry it's actually loopback, not broadcast as implemented in Linux. In Linux it's implemented in ip_route_output_slow(). Essentially converted to 127.0.0.1 I think it's traditional BSD behaviour but couldn't find it on a quick look in FreeBSD source (but haven't looked very intensively) One has to set their way-back machine pretty far back to find the *BSD bits which used 0.0.0.0 as the all nets, all subnets (to mis-use a term) broadcast IPv4 address when sending. Perhaps as far back as the time before HP-UX 7 or SunOS4. The bit errors in my dimm memory get pretty dense that far back... It has hung-on in various places (stacks) as an accepted broadcast IP in the receive path, but not the send path for quite possibly decades now. rick jones - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
It has hung-on in various places (stacks) as an accepted broadcast IP in the receive path, but not the send path for quite possibly decades now. Well it is valid in Linux for sending. And who knows who relies on it. -Andi - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
-BEGIN PGP SIGNED MESSAGE- Hash: SHA1 David Miller wrote: It just occured to me that AF_UNSPEC might be used simply because all zeros might be a valid real bindable address for some address family. And using AF_UNSPEC avoids that problem entirely. Yes, but for IPv4/6 it's not an issue. Some implementations might handle all-zeros and the spec _currently_ calls for it. In this case an alignment would be good. I guess I'll just go ahead and file a problem report with the spec. Maybe the Unix vendors will test their implementations in provide feedback. - -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖ -BEGIN PGP SIGNATURE- Version: GnuPG v1.4.7 (GNU/Linux) iD8DBQFG8Vam2ijCOnn/RHQRAlw2AJwPCkD/GdX5YWCjsidhNXkGT71SiQCeLUDX XimSWS2NMI9T8QxnnV3FDQ4= =8XbG -END PGP SIGNATURE- - To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: follow-up: discrepancy with POSIX
On Wed, 19 Sep 2007 11:38:57 PDT, Rick Jones said: One has to set their way-back machine pretty far back to find the *BSD bits which used 0.0.0.0 as the all nets, all subnets (to mis-use a term) broadcast IPv4 address when sending. Perhaps as far back as the time before HP-UX 7 or SunOS4. The bit errors in my dimm memory get pretty dense that far back... That would be BSD4.2 - BSD4.3 went to all-ones, and it *was* quite the little mess if you had both flavors of boxes on the same subnet at the same time, it would packet-storm *quite* easily. pgpj11lqgjnak.pgp Description: PGP signature
