alexandernst alexandernst - 6 months ago 11
Linux Question

Dynamically adding entries to sysctl

Consider this code:

int procmon_state = 0;
static struct ctl_table_header *procmon_table_header;

static ctl_table state_table[] = {
{
.procname = "state", .mode = 0666,
.proc_handler = &proc_dointvec_minmax,
.data = &procmon_state, .maxlen = sizeof(int),
.extra1 = "\x00\x00\x00\x00" /*0*/, .extra2 = "\x01\x00\x00\x00" /*1*/
},
{ 0 }
};

static ctl_table procmon_table[] = {
{
.procname = "procmon", .mode = 0555,
.child = state_table
},
{ 0 }
};

procmon_table_header = register_sysctl_table(procmon_table);


This will create an entry in
/proc/sys
(so I could then just
sysctl procmon.state=1
).

My question is: Once that entry is created, how can I add more entries?

EDIT: More entries inside
procmon
, that is. For example,
procmon.another_state

CL. CL.
Answer

There are no functions for changing sysctl tables in sysctl.h.

You have to list all entries that you might need before calling register_sysctl_table.

If you really need to change the table afterwards, you have to call unregister_sysctl_table before doing your modifications, and then register it again.

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