On Tue, Oct 13, 2009 at 06:11:48AM -0700, Cuero Bugot wrote:
>Hi all,
>
>We actually found the problem with gethostbyname on uClibc.
>When we change the network interface, the /etc/resolv.conf is also and
>apparently the uClibc resolve code is not reloading the nameserver
>configuration files.
>To fixe it we did a very simple patch (attached) (against version uClibc
>0.9.29).
We moved to git. See http://git.uclibc.org/uClibc
>
>The idea is that if a ns lookup fails then the nameserver file is reloaded. I
>believe that the overhead of reloading the nameservers in case of ns lookup
>failure is really small.
I'm not sure i understand what you say? Your scenario sounds (to me,
correct me if i'm wrong) like:
If resolv.conf changes then reload resolv.conf ¹)
>The patch is a few line long in libc/inet/resolv.c file.
>
>I have seen that in head version of resolv.c has been refactored a little
>(which is a good thing), but this prb has not been taken care of. Instead
>there is a new thing (which I believe is actually not very usefull): the
>nameserver file is reloaded every 256 seconds.
That's not too helpful either, yes. ¹)
>
>The reload on failure patch could be applied on head version.
As mentioned above, svn isn't used anymore.
>
>Is anybody interested ? How can we go further ?
Not terribly interrested (the resolver could need a complete rewrite
against the SUSv4 requirements), but..
Denys, apparently you added that rereading, got a better idea than
the +60b below?
¹) attached
diff --git a/libc/inet/resolv.c b/libc/inet/resolv.c
index 6611466..552d8b5 100644
--- a/libc/inet/resolv.c
+++ b/libc/inet/resolv.c
@@ -312,6 +312,7 @@ Domain name in a message can be represented as either:
#include <arpa/nameser.h>
#include <sys/utsname.h>
#include <sys/un.h>
+#include <sys/stat.h>
#include <bits/uClibc_mutex.h>
/* poll() is not supported in kernel <= 2.0, therefore if __NR_poll is
@@ -948,19 +949,18 @@ static char *skip_and_NUL_space(char *p)
/* Must be called under __resolv_lock. */
void attribute_hidden __open_nameservers(void)
{
- static uint8_t last_time;
-
char szBuffer[MAXLEN_searchdomain];
FILE *fp;
int i;
sockaddr46_t sa;
+ static time_t resolv_conf_mtime;
if (!__res_sync) {
- /* Provide for periodic reread of /etc/resolv.conf */
- /* cur_time "ticks" every 256 seconds */
- uint8_t cur_time = ((unsigned)time(NULL)) >> 8;
- if (last_time != cur_time) {
- last_time = cur_time;
+ /* Reread /etc/resolv.conf if it was modified. */
+ struct stat sb;
+ stat("/etc/resolv.conf", &sb);
+ if ((difftime(resolv_conf_mtime, sb.st_mtime)) < 0) {
+ resolv_conf_mtime = sb.st_mtime;
__close_nameservers(); /* force config reread */
}
}
@@ -969,6 +969,7 @@ void attribute_hidden __open_nameservers(void)
goto sync;
fp = fopen("/etc/resolv.conf", "r");
+#ifdef FALLBACK_TO_CONFIG_RESOLVCONF
if (!fp) {
/* If we do not have a pre-populated /etc/resolv.conf then
try to use the one from /etc/config which exists on numerous
@@ -976,6 +977,7 @@ void attribute_hidden __open_nameservers(void)
may be the only /etc dir that was mounted rw. */
fp = fopen("/etc/config/resolv.conf", "r");
}
+#endif
if (fp) {
while (fgets(szBuffer, sizeof(szBuffer), fp) != NULL) {
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