Index: include/resolv.h
===================================================================
--- include/resolv.h
+++ include/resolv.h
@@ -188,6 +188,8 @@
 		} _ext;
 	} _u;
 	u_char	*_rnd;			/*%< PRIVATE: random state */
+	struct timespec conf_mtim;	/*%< mod time of loaded resolv.conf */
+	time_t conf_stat;		/*%< time of last stat(resolv.conf) */
 };
 
 typedef struct __res_state *res_state;
@@ -243,6 +245,7 @@
 #define	RES_KEEPTSIG	0x00010000	/*%< do not strip TSIG records */
 #define	RES_BLAST	0x00020000	/*%< blast all recursive servers */
 #define RES_NSID	0x00040000      /*%< request name server ID */
+#define RES_NO_RELOAD	0x00080000	/*%< no auto reload of resolv.conf */
 #define RES_NOTLDQUERY	0x00100000	/*%< don't unqualified name as a tld */
 #define RES_USE_DNSSEC	0x00200000	/*%< use DNSSEC using OK bit in OPT */
 /* #define RES_DEBUG2	0x00400000 */	/* nslookup internal */
Index: lib/libc/resolv/res_init.c
===================================================================
--- lib/libc/resolv/res_init.c
+++ lib/libc/resolv/res_init.c
@@ -78,6 +78,7 @@
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/time.h>
 
 #include <netinet/in.h>
@@ -321,6 +322,22 @@
 
 	nserv = 0;
 	if ((fp = fopen(_PATH_RESCONF, "re")) != NULL) {
+	    struct stat sb;
+	    struct timespec now;
+
+	    if (_fstat(fileno(fp), &sb) == 0) {
+		statp->conf_mtim = sb.st_mtim;
+		if (clock_gettime(CLOCK_MONOTONIC_FAST, &now) == 0) {
+		    statp->conf_stat = now.tv_sec;
+		} else {
+		    statp->conf_stat = 0;
+		}
+	    } else {
+		statp->conf_mtim.tv_sec = 0;
+		statp->conf_mtim.tv_nsec = 0;
+		statp->conf_stat = 0;
+	    }
+
 	    /* read the config file */
 	    while (fgets(buf, sizeof(buf), fp) != NULL) {
 		/* skip comments */
@@ -666,7 +683,9 @@
 		} else if (!strncmp(cp, "no-check-names",
 				    sizeof("no-check-names") - 1)) {
 			statp->options |= RES_NOCHECKNAME;
-		}
+		} else if (!strncmp(cp, "no-reload", sizeof("no-reload") - 1)) {
+			statp->options |= RES_NO_RELOAD;
+                }
 #ifdef RES_USE_EDNS0
 		else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
 			statp->options |= RES_USE_EDNS0;
Index: lib/libc/resolv/res_state.c
===================================================================
--- lib/libc/resolv/res_state.c
+++ 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>
@@ -37,6 +39,8 @@
 
 #undef _res
 
+#define RELOAD_INTERVAL 10	/* seconds */
+
 struct __res_state _res;
 
 static thread_key_t res_key;
@@ -59,13 +63,35 @@
 	res_thr_keycreated = thr_keycreate(&res_key, free_res) == 0;
 }
 
+static res_state
+res_check_reload(res_state statp)
+{
+	if ((statp->options & (RES_INIT|RES_NO_RELOAD)) == RES_INIT) {
+		struct timespec now;
+
+		if (clock_gettime(CLOCK_MONOTONIC_FAST, &now) != 0 ||
+		    (now.tv_sec - statp->conf_stat) >= RELOAD_INTERVAL) {
+			struct stat sb;
+
+                        statp->conf_stat = now.tv_sec;
+			if (stat(_PATH_RESCONF, &sb) == 0 &&
+			    (sb.st_mtim.tv_sec  != statp->conf_mtim.tv_sec ||
+			     sb.st_mtim.tv_nsec != statp->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 +99,7 @@
 
 	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);
Index: share/man/man5/resolver.5
===================================================================
--- share/man/man5/resolver.5
+++ share/man/man5/resolver.5
@@ -28,7 +28,7 @@
 .\"     @(#)resolver.5	8.1 (Berkeley) 6/5/93
 .\" $FreeBSD$
 .\"
-.Dd December 25, 2013
+.Dd October 9, 2015
 .Dt RESOLVER 5
 .Os
 .Sh NAME
@@ -175,6 +175,14 @@
 and
 .Sy search
 rules with the given name.
+.It Sy no-reload
+Do not automatically reload
+.Pa /etc/resolv.conf
+when the file changes.
+By default, the resolver will notice modifications
+within ten seconds and automatically reload the file.
+Small or heavily loaded systems might use this option to disable
+this behavior.
 .El
 .Pp
 Options may also be specified as a space or tab separated list using the
@@ -191,7 +199,7 @@
 the last instance will override.
 .Pp
 The keyword and value must appear on a single line, and the keyword
-(e.g.\&
+(e.g.,\&
 .Sy nameserver )
 must start the line.
 The value follows the keyword, separated by white space.