3 files changed, 62 insertions, 4 deletions

diff --git a/lib/libc/resolv/res_init.c b/lib/libc/resolv/res_init.c
index f636baa..41e9f5a 100644
--- a/lib/libc/resolv/res_init.c
+++ b/lib/libc/resolv/res_init.c
@@ -78,6 +78,7 @@ __FBSDID("$FreeBSD$");
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/time.h>
 
 #include <netinet/in.h>
@@ -238,6 +239,7 @@ __res_vinit(res_state statp, int preinit) {
 		statp->_u._ext.ext->nsaddrs[0].sin = statp->nsaddr;
 		strcpy(statp->_u._ext.ext->nsuffix, "ip6.arpa");
 		strcpy(statp->_u._ext.ext->nsuffix2, "ip6.int");
+		statp->_u._ext.ext->reload_period = 2;
 	} else {
 		/*
 		 * Historically res_init() rarely, if at all, failed.
@@ -323,6 +325,18 @@ __res_vinit(res_state statp, int preinit) {
 
 	nserv = 0;
 	if ((fp = fopen(_PATH_RESCONF, "re")) != NULL) {
+	    struct stat sb;
+	    struct timespec now;
+
+	    if (statp->_u._ext.ext != NULL) {
+		if (_fstat(fileno(fp), &sb) == 0) {
+		    statp->_u._ext.ext->conf_mtim = sb.st_mtim;
+		    if (clock_gettime(CLOCK_MONOTONIC_FAST, &now) == 0) {
+			statp->_u._ext.ext->conf_stat = now.tv_sec;
+		    }
+		}
+	    }
+
 	    /* read the config file */
 	    while (fgets(buf, sizeof(buf), fp) != NULL) {
 		/* skip comments */
@@ -583,9 +597,7 @@ res_setoptions(res_state statp, const char *options, const char *source)
 {
 	const char *cp = options;
 	int i;
-#ifndef _LIBC
 	struct __res_state_ext *ext = statp->_u._ext.ext;
-#endif
 
 #ifdef DEBUG
 	if (statp->options & RES_DEBUG)
@@ -668,6 +680,12 @@ res_setoptions(res_state statp, const char *options, const char *source)
 		} else if (!strncmp(cp, "no-check-names",
 				    sizeof("no-check-names") - 1)) {
 			statp->options |= RES_NOCHECKNAME;
+		} else if (!strncmp(cp, "reload-period:",
+				    sizeof("reload-period:") - 1)) {
+			if (ext != NULL) {
+				ext->reload_period = (u_short)
+				    atoi(cp + sizeof("reload-period:") - 1);
+			}
 		}
 #ifdef RES_USE_EDNS0
 		else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
diff --git a/lib/libc/resolv/res_private.h b/lib/libc/resolv/res_private.h
index 4e98157..a986e95 100644
--- a/lib/libc/resolv/res_private.h
+++ b/lib/libc/resolv/res_private.h
@@ -1,3 +1,5 @@
+/* $FreeBSD$ */
+
 #ifndef res_private_h
 #define res_private_h
 
@@ -12,6 +14,9 @@ struct __res_state_ext {
 	} sort_list[MAXRESOLVSORT];
 	char nsuffix[64];
 	char nsuffix2[64];
+	struct timespec	conf_mtim;	/* mod time of loaded resolv.conf */
+	time_t		conf_stat;	/* time of last stat(resolv.conf) */
+	u_short	reload_period;		/* seconds between stat(resolv.conf) */
 };
 
 extern int
diff --git a/lib/libc/resolv/res_state.c b/lib/libc/resolv/res_state.c
index 59c9430..6d31d92 100644
--- a/lib/libc/resolv/res_state.c
+++ b/lib/libc/resolv/res_state.c
@@ -26,6 +26,8 @@
  */
 
 #include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
 #include <netinet/in.h>
 #include <arpa/nameser.h>
 #include <resolv.h>
@@ -35,6 +37,8 @@
 #include "reentrant.h"
 #include "un-namespace.h"
 
+#include "res_private.h"
+
 #undef _res
 
 struct __res_state _res;
@@ -59,13 +63,44 @@ res_keycreate(void)
 	res_thr_keycreated = thr_keycreate(&res_key, free_res) == 0;
 }
 
+static res_state
+res_check_reload(res_state statp)
+{
+	struct timespec now;
+	struct stat sb;
+	struct __res_state_ext *ext;
+
+	if ((statp->options & RES_INIT) == 0) {
+		return (statp);
+	}
+
+	ext = statp->_u._ext.ext;
+	if (ext == NULL || ext->reload_period == 0) {
+		return (statp);
+	}
+
+	if (clock_gettime(CLOCK_MONOTONIC_FAST, &now) != 0 ||
+	    (now.tv_sec - ext->conf_stat) < ext->reload_period) {
+		return (statp);
+	}
+
+	ext->conf_stat = now.tv_sec;
+	if (stat(_PATH_RESCONF, &sb) == 0 &&
+	    (sb.st_mtim.tv_sec  != ext->conf_mtim.tv_sec ||
+	     sb.st_mtim.tv_nsec != ext->conf_mtim.tv_nsec)) {
+		statp->options &= ~RES_INIT;
+	}
+
+	return (statp);
+}
+
 res_state
 __res_state(void)
 {
 	res_state statp;
 
 	if (thr_main() != 0)
-		return (&_res);
+		return res_check_reload(&_res);
 
 	if (thr_once(&res_init_once, res_keycreate) != 0 ||
 	    !res_thr_keycreated)
@@ -73,7 +108,7 @@ __res_state(void)
 
 	statp = thr_getspecific(res_key);
 	if (statp != NULL)
-		return (statp);
+		return res_check_reload(statp);
 	statp = calloc(1, sizeof(*statp));
 	if (statp == NULL)
 		return (&_res);