Re: [PATCH 0/5] net: sysctl: share ipv4/ipv6 sysctl tables

[Lucian Adrian Grijincu]

On Fri, Feb 4, 2011 at 12:49 PM, Alexey Dobriyan <adobriyan@xxxxxxxxx> wrote:
>> Finally share the leaf sysctl tables for ipv4/ipv6:
>>
>> Â[PATCH 4/5] ipv4: share sysctl net/ipv4/conf/DEVNAME/ tables
>> Â[PATCH 5/5] ipv6: share sysctl net/ipv6/conf/DEVNAME/ tables
>
> Meh.
>
> First you remove ->parent, then heroically pass "struct file *"
> to sysctl handlers which duplicates all information already passed
> and brings dcache into picture.
>
> Binary sysctl rewrite confused you into thinking that d_name.name
> is the way, but it isn't.
> For binary sysctl(2) you wouldn't get d_name.name.


Are you really sure?

I ran this code on a machine with and without these patches. It seems
to work fine.

It reads the value from /proc/sys/net/ipv4/conf/default/tag and writes 42 back.

I'm not sure what I have to do to pass the name of a device (e.g.
"eth0") instead of "default" but at least "default" and "all" work and
have valid dentries.


#define _GNU_SOURCE
#include <unistd.h>
#include <sys/syscall.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/sysctl.h>


int main(void)
{
	struct __sysctl_args args;
	int oldtag, newtag;
	size_t oldtaglen, newtaglen;

	int name[] = { CTL_NET, NET_IPV4, NET_IPV4_CONF,
NET_PROTO_CONF_DEFAULT, NET_IPV4_CONF_TAG };

	memset(&args, 0, sizeof(struct __sysctl_args));
	args.name = name;
	args.nlen = sizeof(name)/sizeof(name[0]);

	oldtag = -1;
	oldtaglen = sizeof(oldtag);
	args.oldval = &oldtag;
	args.oldlenp = &oldtaglen;

	newtag = 42;
	newtaglen = sizeof(newtag);
	args.newval = &newtag;
	args.newlen = newtaglen;

	if (syscall(SYS__sysctl, &args) == -1) {
		perror("_sysctl");
		exit(EXIT_FAILURE);
	}
	printf("Old tag was %d, new tag is %d\n", oldtag, newtag);
	exit(EXIT_SUCCESS);
}


-- 
Â.
..: Lucian
--
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/