[PATCH] [BZ #20900] Call __res_vinit if _PATH_RESCONF is changed

[H.J. Lu]

The content of _PATH_RESCONF may change over time with DHCP.
__res_maybe_init should check if _PATH_RESCONF is changed.  Otherwise
a long-running process will get wrong DNS results if _PATH_RESCONF is
changed by DHCP.

Any comments?

H.J.
---
	[BZ #20900]
	* resolv/res_libc.c: Include <sys/stat.h>.
	(__res_maybe_init): Call __res_vinit if _PATH_RESCONF has been
	changed since the last time.
---
 resolv/res_libc.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/resolv/res_libc.c b/resolv/res_libc.c
index a4b376f..47b2d42 100644
--- a/resolv/res_libc.c
+++ b/resolv/res_libc.c
@@ -23,6 +23,7 @@
 #include <sys/types.h>
 #include <netinet/in.h>
 #include <arpa/nameser.h>
+#include <sys/stat.h>
 #include <resolv.h>
 #include <libc-lock.h>
 
@@ -97,6 +98,21 @@ __res_maybe_init (res_state resp, int preinit)
 			if (resp->nscount > 0)
 				__res_iclose (resp, true);
 			return __res_vinit (resp, 1);
+		} else {
+			struct stat buf;
+
+			/* Call __res_vinit if _PATH_RESCONF has been
+			   changed since the last time.  */
+			if (stat (_PATH_RESCONF, &buf) == 0) {
+				static struct timespec mtime;
+				if (mtime.tv_sec != buf.st_mtim.tv_sec
+				    || mtime.tv_nsec != buf.st_mtim.tv_nsec) {
+					mtime = buf.st_mtim;
+					if (resp->nscount > 0)
+						__res_iclose (resp, true);
+					return __res_vinit (resp, 1);
+				}
+			}
 		}
 		return 0;
 	} else if (preinit) {
-- 
2.7.4