Date: Wed, 30 Nov 2011 23:07:18 +0100 From: Damien Fleuriot <ml@my.gd> To: freebsd-hackers@freebsd.org Subject: Re: sysctl description spillover and also setting the sysctl ? Message-ID: <4ED6A916.9030409@my.gd> In-Reply-To: <20111130184815.GA70174@DataIX.net> References: <20111125073630.GC7915@DataIX.net> <201111301152.47002.jhb@freebsd.org> <20111130184815.GA70174@DataIX.net>
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On 11/30/11 7:48 PM, Jason Hellenthal wrote:
>
>
> On Wed, Nov 30, 2011 at 11:52:46AM -0500, John Baldwin wrote:
>> On Friday, November 25, 2011 2:36:30 am Jason Hellenthal wrote:
>>>
>>> Found a troubling result of the following and figured someone might want to
>> take a look.
>>>
>>> Pay close attention to the output and behavior.
>>>
>>> sysctl net.inet.udp.blackhole=0
>>> sysctl net.inet.udp.blackhole
>>> sysctl -d net.inet.udp.blackhole=1
>>> sysctl net.inet.udp.blackhole
>>>
>>>
>>> Is this expected ? should it not just display the description instead of
>> adjusting ? as well not display the description like it is adjusting the
>> description too ?
>>
>> Hah, cute. It should probably fail with an error if you do something like
>> that, yes.
>>
>
> Yeah thats what I thought about it to but the more I thought about it, if it just displayed the values changing instead of the description when =N is supplied I think that would be acceptable to. 0 -> 1 in this case. Or possibly sys.oid: 0 -> 1 # <Description> since sysctl.conf(5) also takes comments like that.
>
> Not really thats something at the top of the list for fixes though. Low fruit. Food for thought.
>
Ok so I'm totally not a dev, don't take my findings for granted, but:
(gdb) run
The program being debugged has been started already.
Start it from the beginning? (y or n) y
Starting program: /usr/src/sbin/sysctl/sysctl -d net.inet.udp.blackhole=1
Breakpoint 5, show_var (oid=0x7fffffffe1d0, nlen=4) at
/usr/src/sbin/sysctl/sysctl.c:549
549 {
(gdb) s
562 bzero(buf, BUFSIZ);
(gdb) s
563 bzero(name, BUFSIZ);
(gdb) s
564 qoid[0] = 0;
(gdb) s
565 memcpy(qoid + 2, oid, nlen * sizeof(int));
(gdb) s
567 qoid[1] = 1;
(gdb) s
568 j = sizeof(name);
(gdb) s
569 i = sysctl(qoid, nlen + 2, name, &j, 0, 0);
(gdb) s
570 if (i || !j)
(gdb) s
573 if (Nflag) {
(gdb) s
578 if (eflag)
(gdb) s
581 sep = ": ";
(gdb) s
583 if (dflag) { /* just print description */
(gdb) s
584 qoid[1] = 5;
(gdb) s
585 j = sizeof(buf);
(gdb) s
586 i = sysctl(qoid, nlen + 2, buf, &j, 0, 0);
(gdb) s
587 if (!nflag)
(gdb) s
588 printf("%s%s", name, sep);
(gdb) s
net.inet.udp.blackhole:
589 printf("%s", buf);
(gdb) s
Do not send port unreachables for refused connects
590 return (0);
(gdb) s
719 }
At this point, we have shown the description and should exit.
Instead, we're calling parse() again ?
(gdb) s
parse (string=0x7fffffffee07 "net.inet.udp.blackhole") at
/usr/src/sbin/sysctl/sysctl.c:299
299 if (sysctl(mib, len, 0, 0, newval, newsize) == -1) {
(gdb) s
318 if (!bflag)
(gdb) s
319 printf(" -> ");
(gdb) s
-> 320 i = nflag;
(gdb) s
321 nflag = 1;
(gdb) s
322 j = show_var(mib, len);
(gdb) s
Breakpoint 5, show_var (oid=0x7fffffffe1d0, nlen=4) at
/usr/src/sbin/sysctl/sysctl.c:549
549 {
(gdb) s
562 bzero(buf, BUFSIZ);
(gdb) s
563 bzero(name, BUFSIZ);
(gdb) s
564 qoid[0] = 0;
(gdb) s
565 memcpy(qoid + 2, oid, nlen * sizeof(int));
(gdb) s
567 qoid[1] = 1;
(gdb) s
568 j = sizeof(name);
(gdb) s
569 i = sysctl(qoid, nlen + 2, name, &j, 0, 0);
(gdb) s
570 if (i || !j)
(gdb) s
573 if (Nflag) {
(gdb) s
578 if (eflag)
(gdb) s
581 sep = ": ";
(gdb) s
583 if (dflag) { /* just print description */
(gdb) s
584 qoid[1] = 5;
(gdb) s
585 j = sizeof(buf);
(gdb) s
586 i = sysctl(qoid, nlen + 2, buf, &j, 0, 0);
(gdb) s
587 if (!nflag)
(gdb) s
589 printf("%s", buf);
(gdb) s
Do not send port unreachables for refused connects
590 return (0);
(gdb) s
719 }
(gdb) s
parse (string=0x7fffffffee07 "net.inet.udp.blackhole") at
/usr/src/sbin/sysctl/sysctl.c:323
323 if (!j && !bflag)
(gdb) s
324 putchar('\n');
(gdb) s
__sputc (_c=10, _p=0x80085a810) at stdio.h:457
457 if (--_p->_w >= 0 || (_p->_w >= _p->_lbfsize && (char)_c
!= '\n'))
(gdb) s
460 return (__swbuf(_c, _p));
(gdb) s
461 }
(gdb) s
parse (string=0x7fffffffee07 "net.inet.udp.blackhole") at
/usr/src/sbin/sysctl/sysctl.c:325
325 nflag = i;
(gdb) s
327 }
(gdb) s
main (argc=0, argv=0x7fffffffeb48) at /usr/src/sbin/sysctl/sysctl.c:154
154 while (argc-- > 0)
(gdb) s
156 exit(warncount);
(gdb) s
Program exited normally.
I think that the issue here is that sysctl continues being run after
displaying the description at line 588.
I would assume that upon reaching the closing hyphen at line 719 ,
sysctl would want to stop.
It was asked to show a description, it has, end of the story.
Instead, at line 590, we simply return 0, then continue running.
Perhaps we would want sysctl to exit, instead of returning 0 ?
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