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ipv6 addrconf: remove addrconf_sysctl_hop_limit()

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This is an effective no-op in terms of user observable behaviour.

By preventing the overwrite of non-null extra1/extra2 fields
in addrconf_sysctl() we can enable the use of proc_dointvec_minmax().

This allows us to eliminate the constant min/max (1..255) trampoline
function that is addrconf_sysctl_hop_limit().

This is nice because it simplifies the code, and allows future
sysctls with constant min/max limits to also not require trampolines.

We still can't eliminate the trampoline for mtu because it isn't
actually a constant (it depends on other tunables of the device)
and thus requires at-write-time logic to enforce range.

Signed-off-by: Maciej Żenczykowski <maze@google.com>
Acked-by: Erik Kline <ek@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Maciej Żenczykowski 2016-09-29 00:33:43 -07:00 committed by David S. Miller
parent d4ef9f7212
commit cb9e684e89
1 changed files with 14 additions and 17 deletions
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31
net/ipv6/addrconf.c
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@ -5496,20 +5496,6 @@ int addrconf_sysctl_forward(struct ctl_table *ctl, int write,
return ret;
}
static
int addrconf_sysctl_hop_limit(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
{
struct ctl_table lctl;
int min_hl = 1, max_hl = 255;
lctl = *ctl;
lctl.extra1 = &min_hl;
lctl.extra2 = &max_hl;
return proc_dointvec_minmax(&lctl, write, buffer, lenp, ppos);
}
static
int addrconf_sysctl_mtu(struct ctl_table *ctl, int write,
void __user *buffer, size_t *lenp, loff_t *ppos)
@ -5743,6 +5729,9 @@ int addrconf_sysctl_ignore_routes_with_linkdown(struct ctl_table *ctl,
return ret;
}
static const int one = 1;
static const int two_five_five = 255;
static const struct ctl_table addrconf_sysctl[] = {
{
.procname = "forwarding",
@ -5756,7 +5745,9 @@ static const struct ctl_table addrconf_sysctl[] = {
.data = &ipv6_devconf.hop_limit,
.maxlen = sizeof(int),
.mode = 0644,
.proc_handler = addrconf_sysctl_hop_limit,
.proc_handler = proc_dointvec_minmax,
.extra1 = (void *)&one,
.extra2 = (void *)&two_five_five,
},
{
.procname = "mtu",
@ -6081,8 +6072,14 @@ static int __addrconf_sysctl_register(struct net *net, char *dev_name,
for (i = 0; table[i].data; i++) {
table[i].data += (char *)p - (char *)&ipv6_devconf;
table[i].extra1 = idev; /* embedded; no ref */
table[i].extra2 = net;
/* If one of these is already set, then it is not safe to
* overwrite either of them: this makes proc_dointvec_minmax
* usable.
*/
if (!table[i].extra1 && !table[i].extra2) {
table[i].extra1 = idev; /* embedded; no ref */
table[i].extra2 = net;
}
}
snprintf(path, sizeof(path), "net/ipv6/conf/%s", dev_name);