Hello,
I have found a bug in resolv.c in conjunction with the function res_init:
res_init sets __ res_sync to res_sync_func and then calls __res_vinit.
-> __res_vinit calls __ open_nameservers.
In __open_nameservers __nameserver and __nameservers are set by the
contents of resolv.conf. So far so good.
-> __open_nameserver calls res_sync_func
In res_sync_func__nameservers is set to rp->nscount, what is 0.
Backin _res_vinit rp->nscount is set to __nameservers then, what is 0. So the
cat bites its own tail.
Attached is a simple patch, that fixes the problemby setting __res_sync after
calling __res_vinit.
Before this patch with busybox "nslookup www.google.de" ->
nslookup: can not resolve '(null)': Name or service not known
Name: www.google.de
Address 1: 2a00: 1450:4016:800 :: 101f muc03s01-in-x1f.1e100.net
Address 2: 173.194.35.151 muc03s01-in-f23.1e100.net
Address 3: 173.194.35.159 muc03s01-in-f31.1e100.net
Address 4: 173.194.35.152 muc03s01-in-f24.1e100.net
After the patch "nslookup www.google.de" ->
nslookup www.google.de
Server: 8.8.8.8
Address 1: 8.8.8.8 google-public-dns-a.google.com
Name: www.google.de
Address 1: 2a00: 1450:4016:803 :: 1018 muc03s08-in-x18.1e100.net
Address 2: 173.194.44.56 muc03s08-in-f24.1e100.net
Address 3: 173.194.44.55 muc03s08-in-f23.1e100.net
Address 4: 173.194.44.63 muc03s08-in-f31.1e100.net
This patch ist tested with buildroot-02.13.
Regards, Markus
-- Unsere Aussagen koennen Irrtuemer und Missverstaendnisse enthalten.
Bitte pruefen Sie die Aussagen fuer Ihren Fall, bevor Sie Entscheidungen
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Wiesemann & Theis GmbH, Porschestr. 12, D-42279 Wuppertal
Geschaeftsfuehrer: Dipl.-Ing. Ruediger Theis
Registergericht: Amtsgericht Wuppertal, HRB 6377
Tel. +49-202/2680-0, Fax +49-202/2680-265, http://www.wut.deAutor: Markus Königshaus <[email protected]>
--- uClibc-0.9.33.2.org/libc/inet/resolv.c 2012-05-15 09:20:09.000000000 +0200
+++ uClibc-0.9.33.2/libc/inet/resolv.c 2013-03-28 11:52:55.000000000 +0100
@@ -3653,12 +3653,18 @@
*/
if (!_res.id)
_res.id = res_randomid();
- __res_sync = res_sync_func;
+ __res_sync = NULL;
__UCLIBC_MUTEX_UNLOCK(__resolv_lock);
__res_vinit(&_res, 1);
+ __UCLIBC_MUTEX_LOCK(__resolv_lock);
+
+ __res_sync = res_sync_func;
+
+ __UCLIBC_MUTEX_UNLOCK(__resolv_lock);
+
return 0;
}
libc_hidden_def(res_init)
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