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SubjectRe: [PATCH 0/5] net: sysctl: share ipv4/ipv6 sysctl tables
On Fri, Feb 4, 2011 at 12:49 PM, Alexey Dobriyan <adobriyan@gmail.com> wrote:
>> Finally share the leaf sysctl tables for ipv4/ipv6:
>>
>>  [PATCH 4/5] ipv4: share sysctl net/ipv4/conf/DEVNAME/ tables
>>  [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);
}


--
 .
..: Lucian
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