[svn] New option --dns-cache.

TODO

@@ -15,10 +15,6 @@ represent user-visible changes.
   mirror remote FTP permissions by default.  There should be a new
   option add an option that enables this back on.
 
-* Implement a `--disable-dns-cache' option that disables DNS caching.
-  It is trivial to implement; simply avoid calling cache_host_lookup
-  at the end of lookup_host.
-
 * Honor `Content-Disposition: XXX; filename="FILE"' when creating the
   file name.
 

doc/ChangeLog

@@ -1,3 +1,7 @@
+2003-09-10  Hrvoje Niksic  <hniksic@xemacs.org>
+
+	* wget.texi (Download Options): Documented new option --dns-cache.
+
 2002-04-24  Hrvoje Niksic  <hniksic@arsdigita.com>
 
 	* wget.texi (Robot Exclusion): Explain how to turn off the robot

doc/wget.texi

@@ -16,8 +16,8 @@
 
 @c This should really be generated automatically, possibly by including
 @c an auto-generated file.
-@set VERSION 1.8.1+cvs
+@set VERSION 1.9-cvs
-@set UPDATED December 2001
+@set UPDATED September 2003
 
 @dircategory Net Utilities
 @dircategory World Wide Web
@@ -777,6 +777,29 @@ Thus you may safely type @samp{wget -Q2m -i sites}---download will be
 aborted when the quota is exceeded.
 
 Setting quota to 0 or to @samp{inf} unlimits the download quota.
+
+@cindex DNS cache
+@cindex caching of DNS lookups
+@itemx --dns-cache=off
+Turn off caching of DNS lookups.  Normally, Wget remembers the addresses
+it looked up from DNS so it doesn't have to repeatedly contact the DNS
+server for the same (typically small) set of addresses it retrieves
+from.  This cache exists in memory only; a new Wget run will contact DNS
+again.
+
+However, in some cases it is not desirable to cache host names, even for
+the duration of a short-running application like Wget.  For example,
+some HTTP servers are hosted on machines with dynamically allocated IP
+addresses that change from time to time.  Their DNS entries are updated
+along with each change.  When Wget's download from such a host gets
+interrupted by IP address change, Wget retries the download, but (due to
+DNS caching) it contacts the old address.  With the DNS cache turned
+off, Wget will repeat the DNS lookup for every connect and will thus get
+the correct dynamic address every time---at the cost of additional DNS
+lookups where they're probably not needed.
+
+If you don't understand the above description, you probably won't need
+this option.
 @end table
 
 @node Directory Options, HTTP Options, Download Options, Invoking
@@ -2046,6 +2069,10 @@ Top of directory tree---the same as @samp{-P}.
 Turning dirstruct on or off---the same as @samp{-x} or @samp{-nd},
 respectively.
 
+@item dns_cache = on/off
+Turn DNS caching on/off.  Since DNS caching is on by default, this
+option is normally used to turn it off.  Same as @samp{--dns-cache}.
+
 @item domains = @var{string}
 Same as @samp{-D} (@pxref{Spanning Hosts}).
 

src/ChangeLog

@@ -1,3 +1,9 @@
+2003-09-10  Hrvoje Niksic  <hniksic@xemacs.org>
+
+	* init.c: New command dns_cache.
+
+	* main.c (main): New option --dns-cache[=off].
+
 2003-09-09  Hrvoje Niksic  <hniksic@xemacs.org>
 
 	* config.h.in: Initialize HAVE_GETADDRINFO and ENABLE_IPV6.

src/host.c

@@ -691,6 +691,7 @@ lookup_host (const char *host, int silent)
     logprintf (LOG_VERBOSE, _("done.\n"));
 
   /* Cache the lookup information. */
+  if (opt.dns_cache)
     cache_host_lookup (host, al);
 
   return al;

src/init.c

@@ -131,6 +131,7 @@ static struct {
   { "deleteafter",	&opt.delete_after,	cmd_boolean },
   { "dirprefix",	&opt.dir_prefix,	cmd_directory },
   { "dirstruct",	NULL,			cmd_spec_dirstruct },
+  { "dnscache",		&opt.dns_cache,		cmd_boolean },
   { "domains",		&opt.domains,		cmd_vector },
   { "dotbytes",		&opt.dot_bytes,		cmd_bytes },
   { "dotsinline",	&opt.dots_in_line,	cmd_number },
@@ -278,6 +279,8 @@ defaults (void)
   opt.dot_bytes = 1024;
   opt.dot_spacing = 10;
   opt.dots_in_line = 50;
+
+  opt.dns_cache = 1;
 }
 
 /* Return the user's home directory (strdup-ed), or NULL if none is

src/main.c

@@ -178,6 +178,7 @@ Download:\n\
   -Q,  --quota=NUMBER           set retrieval quota to NUMBER.\n\
        --bind-address=ADDRESS   bind to ADDRESS (hostname or IP) on local host.\n\
        --limit-rate=RATE        limit download rate to RATE.\n\
+       --dns-cache=off          disable caching DNS lookups.\n\
 \n"), stdout);
   fputs (_("\
 Directories:\n\
@@ -314,6 +315,7 @@ main (int argc, char *const *argv)
     { "cookies", required_argument, NULL, 160 },
     { "cut-dirs", required_argument, NULL, 145 },
     { "directory-prefix", required_argument, NULL, 'P' },
+    { "dns-cache", required_argument, NULL, 175 },
     { "domains", required_argument, NULL, 'D' },
     { "dot-style", required_argument, NULL, 134 },
     { "execute", required_argument, NULL, 'e' },
@@ -605,6 +607,9 @@ GNU General Public License for more details.\n"));
 	case 168:
 	  setval ("postfile", optarg);
 	  break;
+	case 175:
+	  setval ("dnscache", optarg);
+	  break;
 	case 'A':
 	  setval ("accept", optarg);
 	  break;

src/options.h

@@ -70,6 +70,7 @@ struct options
 
   char **domains;		/* See host.c */
   char **exclude_domains;
+  int dns_cache;		/* whether we cache DNS lookups. */
 
   char **follow_tags;           /* List of HTML tags to recursively follow. */
   char **ignore_tags;           /* List of HTML tags to ignore if recursing. */