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Date:      Sat, 20 Aug 2005 20:11:16 +0900
From:      Hajimu UMEMOTO <ume@FreeBSD.org>
To:        arch@FreeBSD.org
Subject:   [CFR] reflect resolv.conf update to running application
Message-ID:  <ygefyt4yiaz.wl%ume@mahoroba.org>

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Hi,

Our resolver reads resolv.conf once, and never re-read it.  Recent
OpenBSD changed to re-read resolv.conf when it is updated.  I believe
it is useful specially for mobile environment.  So, I made a patch for
our resolver.  Please review it.

Index: lib/libc/net/getaddrinfo.c
diff -u -p lib/libc/net/getaddrinfo.c.orig lib/libc/net/getaddrinfo.c
--- lib/libc/net/getaddrinfo.c.orig	Sat May 21 22:46:37 2005
+++ lib/libc/net/getaddrinfo.c	Sat May 21 23:20:27 2005
@@ -2443,7 +2443,7 @@ res_searchN(name, target)
 	int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 	char abuf[MAXDNAME];
 
-	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
+	if (_res_init() == -1) {
 		h_errno = NETDB_INTERNAL;
 		return (-1);
 	}
Index: lib/libc/net/gethostbydns.c
diff -u -p lib/libc/net/gethostbydns.c.orig lib/libc/net/gethostbydns.c
--- lib/libc/net/gethostbydns.c.orig	Sat May 21 22:46:37 2005
+++ lib/libc/net/gethostbydns.c	Sat May 21 23:20:27 2005
@@ -538,10 +538,6 @@ _dns_gethostbyaddr(void *rval, void *cb_
 	he = va_arg(ap, struct hostent *);
 	hed = va_arg(ap, struct hostent_data *);
 
-	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
-		h_errno = NETDB_INTERNAL;
-		return NS_UNAVAIL;
-	}
 	switch (af) {
 	case AF_INET:
 		(void) sprintf(qbuf, "%u.%u.%u.%u.in-addr.arpa",
Index: lib/libc/net/gethostnamadr.c
diff -u -p lib/libc/net/gethostnamadr.c.orig lib/libc/net/gethostnamadr.c
--- lib/libc/net/gethostnamadr.c.orig	Sat May 21 22:46:37 2005
+++ lib/libc/net/gethostnamadr.c	Sat May 21 23:20:27 2005
@@ -44,6 +44,7 @@ __FBSDID("$FreeBSD: src/lib/libc/net/get
 #include <resolv.h>			/* XXX hack for _res */
 #include "un-namespace.h"
 #include "netdb_private.h"
+#include "res_config.h"
 
 extern int _ht_gethostbyname(void *, void *, va_list);
 extern int _dns_gethostbyname(void *, void *, va_list);
@@ -264,7 +265,7 @@ gethostbyaddr_r(const char *addr, int le
 		{ 0 }
 	};
 
-	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
+	if (_res_init() == -1) {
 		h_errno = NETDB_INTERNAL;
 		return -1;
 	}
Index: lib/libc/net/getnetbydns.c
diff -u -p lib/libc/net/getnetbydns.c.orig lib/libc/net/getnetbydns.c
--- lib/libc/net/getnetbydns.c.orig	Sat May 21 22:46:37 2005
+++ lib/libc/net/getnetbydns.c	Sat May 21 23:20:27 2005
@@ -304,6 +304,10 @@ _dns_getnetbyaddr(void *rval, void *cb_d
 		    netbr[1], netbr[0]);
 		break;
 	}
+	if (_res_init() == -1) {
+		h_errno = NETDB_INTERNAL;
+		return NS_UNAVAIL;
+	}
 	if ((buf = malloc(sizeof(*buf))) == NULL) {
 		h_errno = NETDB_INTERNAL;
 		return NS_NOTFOUND;
Index: lib/libc/net/name6.c
diff -u -p lib/libc/net/name6.c.orig lib/libc/net/name6.c
--- lib/libc/net/name6.c.orig	Sat May 21 22:46:38 2005
+++ lib/libc/net/name6.c	Sat May 21 23:20:27 2005
@@ -121,6 +121,7 @@ __FBSDID("$FreeBSD: src/lib/libc/net/nam
 #include <unistd.h>
 #include "un-namespace.h"
 #include "netdb_private.h"
+#include "res_config.h"
 
 #ifndef _PATH_HOSTS
 #define	_PATH_HOSTS	"/etc/hosts"
@@ -1810,11 +1811,9 @@ _dns_ghbyaddr(void *rval, void *cb_data,
 		return NS_NOTFOUND;
 	}
 
-	if ((_res.options & RES_INIT) == 0) {
-		if (res_init() < 0) {
-			*errp = h_errno;
-			return NS_UNAVAIL;
-		}
+	if (_res_init() < 0) {
+		*errp = h_errno;
+		return NS_UNAVAIL;
 	}
 	memset(&hbuf, 0, sizeof(hbuf));
 	hbuf.h_name = NULL;
Index: lib/libc/net/res_config.h
diff -u lib/libc/net/res_config.h.orig lib/libc/net/res_config.h
--- lib/libc/net/res_config.h.orig	Sat Mar 23 08:41:54 2002
+++ lib/libc/net/res_config.h	Sat May 21 23:20:27 2005
@@ -8,3 +8,5 @@
 #define MULTI_PTRS_ARE_ALIASES 1 /* fold multiple PTR records into aliases */
 #define	CHECK_SRVR_ADDR 1 /* confirm that the server requested sent the reply */
 #define BIND_UPDATE 1	/* update support */
+
+int _res_init(void);
Index: lib/libc/net/res_init.c
diff -u -p lib/libc/net/res_init.c.orig lib/libc/net/res_init.c
--- lib/libc/net/res_init.c.orig	Thu Feb 26 06:03:45 2004
+++ lib/libc/net/res_init.c	Sat May 21 23:20:27 2005
@@ -78,11 +78,13 @@ __FBSDID("$FreeBSD: src/lib/libc/net/res
 #include <sys/types.h>
 #include <sys/param.h>
 #include <sys/socket.h>
+#include <sys/stat.h>
 #include <sys/time.h>
 #include <netinet/in.h>
 #include <arpa/inet.h>
 #include <arpa/nameser.h>
 #include <ctype.h>
+#include <errno.h>
 #include <limits.h>
 #include <resolv.h>
 #include <stdio.h>
@@ -100,6 +102,7 @@ __FBSDID("$FreeBSD: src/lib/libc/net/res
 #undef h_errno
 extern int h_errno;
 
+static void res_readconf(void);
 static void res_setoptions(char *, char *);
 
 #ifdef RESOLVSORT
@@ -112,6 +115,18 @@ static u_int32_t net_mask(struct in_addr
 # define isascii(c) (!(c & 0200))
 #endif
 
+#define	timespecclear(tvp)	((tvp)->tv_sec = (tvp)->tv_nsec = 0)
+#define	timespeccmp(tvp, uvp, cmp)					\
+	(((tvp)->tv_sec == (uvp)->tv_sec) ?				\
+	    ((tvp)->tv_nsec cmp (uvp)->tv_nsec) :			\
+	    ((tvp)->tv_sec cmp (uvp)->tv_sec))
+
+struct __res_conf_private {
+	struct timespec mtimespec;
+};
+
+static struct __res_conf_private *___res_conf_private(void);
+
 /*
  * Check structure for failed per-thread allocations.
  */
@@ -119,6 +134,7 @@ static struct res_per_thread {
 	struct __res_state res_state;
 	struct __res_state_ext res_state_ext;
 	struct __res_send_private res_send_private;
+	struct __res_conf_private res_conf_private;
 	int h_errno;
 } _res_per_thread_bogus = { .res_send_private = { .s = -1 } }; /* socket */
 
@@ -146,21 +162,8 @@ static struct res_per_thread {
 int
 res_init()
 {
-	FILE *fp;
 	struct __res_send_private *rsp;
-	char *cp, **pp;
-	int n;
-	char buf[MAXDNAME];
-	int nserv = 0;    /* number of nameserver records read from file */
-	int haveenv = 0;
-	int havesearch = 0;
-#ifdef RESOLVSORT
-	int nsort = 0;
-	char *net;
-#endif
-#ifndef RFC1535
-	int dots;
-#endif
+	char *cp;
 
 	/*
 	 * If allocation of memory for this thread's resolver has failed,
@@ -208,6 +211,37 @@ res_init()
 	if (!_res.id)
 		_res.id = res_randomid();
 
+	_res.pfcode = 0;
+	res_readconf();
+
+	if (issetugid())
+		_res.options |= RES_NOALIASES;
+	else if ((cp = getenv("RES_OPTIONS")) != NULL)
+		res_setoptions(cp, "env");
+	_res.options |= RES_INIT;
+	return (0);
+}
+
+static void
+res_readconf()
+{
+	struct __res_conf_private *rcp;
+	FILE *fp;
+	char *cp, **pp;
+	int n;
+	char buf[MAXDNAME];
+	int nserv = 0;    /* number of nameserver records read from file */
+	int haveenv = 0;
+	int havesearch = 0;
+#ifdef RESOLVSORT
+	int nsort = 0;
+	char *net;
+#endif
+#ifndef RFC1535
+	int dots;
+#endif
+	struct stat sb;
+
 #ifdef USELOOPBACK
 	_res.nsaddr.sin_addr = inet_makeaddr(IN_LOOPBACKNET, 1);
 #else
@@ -220,7 +254,6 @@ res_init()
 		memcpy(&_res_ext.nsaddr, &_res.nsaddr, _res.nsaddr.sin_len);
 	_res.nscount = 1;
 	_res.ndots = 1;
-	_res.pfcode = 0;
 
 	/* Allow user to override the local domain definition */
 	if (issetugid() == 0 && (cp = getenv("LOCALDOMAIN")) != NULL) {
@@ -262,7 +295,10 @@ res_init()
 	(line[sizeof(name) - 1] == ' ' || \
 	 line[sizeof(name) - 1] == '\t'))
 
+	rcp = ___res_conf_private();
 	if ((fp = fopen(_PATH_RESCONF, "r")) != NULL) {
+	    if (fstat(fileno(fp), &sb) == 0)
+		rcp->mtimespec = sb.st_mtimespec;
 	    /* read the config file */
 	    while (fgets(buf, sizeof(buf), fp) != NULL) {
 		/* skip comments */
@@ -396,11 +432,11 @@ res_init()
 				if (inet_aton(net, &a)) {
 				    _res.sort_list[nsort].mask = a.s_addr;
 				} else {
-				    _res.sort_list[nsort].mask = 
+				    _res.sort_list[nsort].mask =
 					net_mask(_res.sort_list[nsort].addr);
 				}
 			    } else {
-				_res.sort_list[nsort].mask = 
+				_res.sort_list[nsort].mask =
 				    net_mask(_res.sort_list[nsort].addr);
 			    }
 			    _res_ext.sort_list[nsort].af = AF_INET;
@@ -465,13 +501,14 @@ res_init()
 		    continue;
 		}
 	    }
-	    if (nserv > 1) 
+	    if (nserv > 1)
 		_res.nscount = nserv;
 #ifdef RESOLVSORT
 	    _res.nsort = nsort;
 #endif
 	    (void) fclose(fp);
-	}
+	} else
+	    timespecclear(&rcp->mtimespec);
 	if (_res.defdname[0] == 0 &&
 	    gethostname(buf, sizeof(_res.defdname) - 1) == 0 &&
 	    (cp = strchr(buf, '.')) != NULL)
@@ -507,12 +544,27 @@ res_init()
 #endif
 #endif /* !RFC1535 */
 	}
+}
 
-	if (issetugid())
-		_res.options |= RES_NOALIASES;
-	else if ((cp = getenv("RES_OPTIONS")) != NULL)
-		res_setoptions(cp, "env");
-	_res.options |= RES_INIT;
+int
+_res_init(void)
+{
+	struct __res_conf_private *rcp;
+	struct stat sb;
+
+	if ((_res.options & RES_INIT) == 0)
+		return (res_init());
+
+	if (stat(_PATH_RESCONF, &sb) == -1) {
+		/*
+		 * Lost the file, in chroot?
+		 * Don' trash settings
+		 */
+		return (0);
+	}
+	rcp = ___res_conf_private();
+	if (timespeccmp(&sb.st_mtimespec, &rcp->mtimespec, !=))
+		res_readconf();
 	return (0);
 }
 
@@ -629,6 +681,7 @@ struct __res_state _res;
 #endif
 struct __res_state_ext _res_ext;
 static struct __res_send_private _res_send_private = { .s = -1 }; /* socket */
+static struct __res_conf_private _res_conf_private;
 
 static thread_key_t res_key;
 static once_t res_init_once = ONCE_INITIALIZER;
@@ -697,6 +750,14 @@ ___res_send_private(void)
 	if (thr_main() != 0)
 		return (&_res_send_private);
 	return (&allocate_res()->res_send_private);
+}
+
+struct __res_conf_private *
+___res_conf_private(void)
+{
+	if (thr_main() != 0)
+		return (&_res_conf_private);
+	return (&allocate_res()->res_conf_private);
 }
 
 int *
Index: lib/libc/net/res_query.c
diff -u -p lib/libc/net/res_query.c.orig lib/libc/net/res_query.c
--- lib/libc/net/res_query.c.orig	Sat May 21 22:46:39 2005
+++ lib/libc/net/res_query.c	Sat May 21 23:20:27 2005
@@ -200,7 +200,7 @@ res_search(name, class, type, answer, an
 	int trailing_dot, ret, saved_herrno;
 	int got_nodata = 0, got_servfail = 0, tried_as_is = 0;
 
-	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
+	if (_res_init() == -1) {
 		h_errno = NETDB_INTERNAL;
 		return (-1);
 	}
Index: lib/libc/net/res_update.c
diff -u -p lib/libc/net/res_update.c.orig lib/libc/net/res_update.c
--- lib/libc/net/res_update.c.orig	Mon Sep 16 01:51:09 2002
+++ lib/libc/net/res_update.c	Sat May 21 23:20:27 2005
@@ -36,6 +36,8 @@ __FBSDID("$FreeBSD: src/lib/libc/net/res
 #include <stdlib.h>
 #include <string.h>
 
+#include "res_config.h"
+
 /*
  * Separate a linked list of records into groups so that all records
  * in a group will belong to a single zone on the nameserver.
@@ -84,7 +86,7 @@ res_update(ns_updrec *rrecp_in) {
 	u_int16_t dlen, class, qclass, type, qtype;
 	u_int32_t ttl;
 
-	if ((_res.options & RES_INIT) == 0 && res_init() == -1) {
+	if (_res_init() == -1) {
 		h_errno = NETDB_INTERNAL;
 		return (-1);
 	}


Sincerely,

--
Hajimu UMEMOTO @ Internet Mutual Aid Society Yokohama, Japan
ume@mahoroba.org  ume@{,jp.}FreeBSD.org
http://www.imasy.org/~ume/



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