Re: what's the purpose of MAXHOSTNAMELEN?

From: Jeff Garzik
Date: Tue Dec 29 2009 - 15:21:07 EST


On 12/29/2009 02:56 PM, Samuel Thibault wrote:
Jeff Garzik, le Tue 29 Dec 2009 14:40:05 -0500, a écrit :
On 12/29/2009 02:19 PM, Robert P. J. Day wrote:
arch/s390/include/asm/param.h:#define MAXHOSTNAMELEN 64 /* max
length of hostname */

so lots of people define it but no one uses it. it *is* exported to
user space in /usr/include/asm/param.h, but i still have no idea what
it's for in user space. obsolete?

According to RFC 1034, "Each node has a label, which is zero to 63
octets in length"

That's for Internet networks. Other kinds of networks could implement
more. It could make sense to restrict ourself to Internet standards,
but we don't :)

Er huh? That was a description of the origin of the limit.

And as a point of fact, we do restrict ourself to that:

#define __NEW_UTS_LEN 64

struct new_utsname {
char sysname[__NEW_UTS_LEN + 1];
char nodename[__NEW_UTS_LEN + 1];



What is it used for in userspace, and why is it export from the kernel?

Gethostname, typically, but also all kinds of functions that provide a
hostname. It's also quite often completely badly used, for instance for
getnameinfo()...

You have Debian's list on
http://unstable.buildd.net/buildd/hurd-i386_Failed.html

No one cares about Hurd.

Jeff




--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/