resolver: preserve binary compatibility; reduce header pollution

In r289315, I added new fields to res_state.  This broke binary
backward compatibility.  It also broke some ports (and possibly
other code) by requiring the definition of time_t and struct timespec.

Fix these problems by moving the new fields into __res_state_ext.

Suggested by:	ume
Reviewed by:	ume
MFC after:	3 days
Sponsored by:	Dell Inc.
Differential Revision:	https://reviews.freebsd.org/D4472

include/resolv.h

@@ -57,7 +57,6 @@
 #include <sys/types.h>
 #include <sys/cdefs.h>
 #include <sys/socket.h>
-#include <sys/timespec.h>
 #include <stdio.h>
 #include <arpa/nameser.h>
 
@@ -177,8 +176,7 @@ struct __res_state {
 	int	res_h_errno;		/*%< last one set for this context */
 	int	_vcsock;		/*%< PRIVATE: for res_send VC i/o */
 	u_int	_flags;			/*%< PRIVATE: see below */
-	u_short	reload_period;		/*%< seconds between stat(resolv.conf)*/
-	u_short	_pad;			/*%< make _u 64 bit aligned */
+	u_int	_pad;			/*%< make _u 64 bit aligned */
 	union {
 		/* On an 32-bit arch this means 512b total. */
 		char	pad[72 - 4*sizeof (int) - 3*sizeof (void *)];
@@ -190,8 +188,6 @@ struct __res_state {
 		} _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;

lib/libc/resolv/res_init.c

@@ -228,7 +228,6 @@ __res_vinit(res_state statp, int preinit) {
 	statp->pfcode = 0;
 	statp->_vcsock = -1;
 	statp->_flags = 0;
-	statp->reload_period = 2;
 	statp->qhook = NULL;
 	statp->rhook = NULL;
 	statp->_u._ext.nscount = 0;
@@ -238,6 +237,7 @@ __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.
@@ -326,17 +326,13 @@ __res_vinit(res_state statp, int preinit) {
 	    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;
+	    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;
+		    }
 		}
-	    } else {
-		statp->conf_mtim.tv_sec = 0;
-		statp->conf_mtim.tv_nsec = 0;
-		statp->conf_stat = 0;
 	    }
 
 	    /* read the config file */
@@ -599,9 +595,7 @@ 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)
@@ -686,8 +680,10 @@ res_setoptions(res_state statp, const char *options, const char *source)
 			statp->options |= RES_NOCHECKNAME;
 		} else if (!strncmp(cp, "reload-period:",
 				    sizeof("reload-period:") - 1)) {
-			statp->reload_period = (u_short)
-				atoi(cp + 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)) {

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

lib/libc/resolv/res_state.c

@@ -37,6 +37,8 @@
 #include "reentrant.h"
 #include "un-namespace.h"
 
+#include "res_private.h"
+
 #undef _res
 
 struct __res_state _res;
@@ -66,20 +68,26 @@ res_check_reload(res_state statp)
 {
 	struct timespec now;
 	struct stat sb;
+	struct __res_state_ext *ext;
 
-	if ((statp->options & RES_INIT) == 0 || statp->reload_period == 0) {
+	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 - statp->conf_stat) < statp->reload_period) {
+	    (now.tv_sec - ext->conf_stat) < ext->reload_period) {
 		return (statp);
 	}
 
-	statp->conf_stat = now.tv_sec;
+	ext->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)) {
+	    (sb.st_mtim.tv_sec  != ext->conf_mtim.tv_sec ||
+	     sb.st_mtim.tv_nsec != ext->conf_mtim.tv_nsec)) {
 		statp->options &= ~RES_INIT;
 	}