Store the DNS cache in a coucal hashtable

The resolver cache was a hand-rolled singly-linked list with a dummy head
node: O(n) lookup, O(n^2) build, and each record carried its own next
pointer plus an inline copy of the hostname key. Swap it for coucal, the
hashtable already used for the backing cache and the ready slots, keyed by
hostname with the address record as the value.

coucal owns the records (freed through a value handler on coucal_delete)
and dups the key itself, so t_dnscache sheds both its next link and its
inline iadr string and becomes a pure address record. The state field
keeps the same pointer width (t_dnscache* -> coucal), so the installed
htsopt.h layout and the ABI are unchanged.

Behaviour is identical: same -1/0/>0 lookup contract, same negative
caching, same resolve-once semantics, all under the existing
opt->state.lock (coucal is not internally serialized against the FTP/web
threads). The DNS self-test exercises the full contract black-box and
passes unchanged.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

configure.ac

@@ -1,6 +1,6 @@
 AC_PREREQ([2.71])
 
-AC_INIT([httrack], [3.49.8], [roche+packaging@httrack.com], [httrack], [http://www.httrack.com/])
+AC_INIT([httrack], [3.49.9], [roche+packaging@httrack.com], [httrack], [http://www.httrack.com/])
 AC_COPYRIGHT([
 HTTrack Website Copier, Offline Browser for Windows and Unix
 Copyright (C) 1998-2015 Xavier Roche and other contributors
@@ -29,9 +29,10 @@ AC_CONFIG_SRCDIR(src/httrack.c)
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_HEADERS(config.h)
 AM_INIT_AUTOMAKE([subdir-objects])
-# 4:0:0: htsblk gained the contenttype_given field, an incompatible ABI break,
-# so bump current and reset revision/age.
-VERSION_INFO="4:0:0"
+# 3:1:0: 3.49.9 changed code but not the exported interface vs 3.49.8 (same 164
+# symbols, no struct-layout change), so bump revision only. (3:0:0 was the htsblk
+# mime-buffer widening, an ABI break that moved the soname .so.2 -> .so.3.)
+VERSION_INFO="3:1:0"
 AM_MAINTAINER_MODE
 AC_USE_SYSTEM_EXTENSIONS
 
@@ -214,9 +215,12 @@ AC_SUBST(OPENSSL_LIBS)
 fi
 
 ### Support IPv6
+V6_SUPPORT=no
 AC_CHECK_LIB(c, getaddrinfo, [V6_FLAG="-DINET6"
+V6_SUPPORT=yes
 AC_DEFINE(HTS_INET6, 1, [Check for IPv6])], AC_MSG_WARN([*** IPv6 not found IPv6 compatibility disabled]))
 AC_SUBST(V6_FLAG)
+AC_SUBST(V6_SUPPORT)
 
 ### Check for LFS
 AC_CHECK_LIB(c, fopen64, [LFS_FLAG="-D_FILE_OFFSET_BITS=64 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE"

debian/changelog

@@ -1,12 +1,13 @@
-httrack (3.49.8-3) unstable; urgency=medium
+httrack (3.49.9-1) unstable; urgency=medium
 
-  * Rename libhttrack3 to libhttrack4 to follow the SONAME bump to
-    libhttrack.so.4: htsblk gained a contenttype_given field, an
-    incompatible ABI change (VERSION_INFO 3 -> 4). The .files wildcard
-    now tracks .so.4* so the runtime libraries land in the right
-    package. New binary package, via NEW.
+  * New upstream release: Content-Type and file-type detection fixes (trust a
+    declared Content-Type over a binary URL extension, honor --assume under the
+    delayed type check, keep a known extension against a bogus or empty
+    Content-Type, and avoid an uninitialised read on an empty Content-Type), and
+    restored C++ source-compatibility of the installed headers so reverse
+    dependencies (httraqt) build again.
 
- -- Xavier Roche <xavier@debian.org>  Sat, 20 Jun 2026 19:46:16 +0200
+ -- Xavier Roche <xavier@debian.org>  Sun, 21 Jun 2026 17:59:38 +0200
 
 httrack (3.49.8-2) unstable; urgency=medium
 

debian/control

@@ -58,13 +58,13 @@ Description: webhttrack common files
  This package is the common files of webhttrack, website copier and
  mirroring utility
 
-Package: libhttrack4
+Package: libhttrack3
 Architecture: any
 Multi-Arch: same
 Section: libs
 Depends: ${misc:Depends}, ${shlibs:Depends}
-Replaces: libhttrack3, httrack (<< 3.49.8-3~)
-Breaks: libhttrack3, httrack (<< 3.49.8-3~)
+Replaces: libhttrack2, httrack (<< 3.49.8-2~)
+Breaks: libhttrack2, httrack (<< 3.49.8-2~)
 Description: Httrack website copier library
  This package is the library part of httrack, website copier and mirroring
  utility

debian/copyright

@@ -1,21 +1,109 @@
-This package was debianized by Xavier Roche <roche@httrack.com> on
-Fri, 27 Sep 2002 16:42:26 +0200
+Format: https://www.debian.org/doc/packaging-manuals/copyright-format/1.0/
+Upstream-Name: httrack
+Upstream-Contact: Xavier Roche <roche@httrack.com>
+Source: https://www.httrack.com/
 
-The current Debian maintainer is Xavier Roche <xavier@debian.org>
+Files: *
+Copyright: 1998-2026 Xavier Roche and other contributors
+License: GPL-3+
+Comment:
+ The engine includes contributions from Yann Philippot (src/htsjava.c,
+ src/htsjava.h). htsbasenet.h links against the system OpenSSL library
+ (originally by Eric Young); no OpenSSL/SSLeay code is bundled here.
 
-Upstream author: Xavier Roche <roche@httrack.com>
+Files: src/minizip/*
+Copyright: 1998-2010 Gilles Vollant
+           2007-2008 Even Rouault
+           2009-2010 Mathias Svensson
+           1990-2000 Info-ZIP
+License: Zlib
+Comment:
+ The decryption code in src/minizip/crypt.h and src/minizip/unzip.c derives
+ from the Info-ZIP distribution, distributed under the same terms.
 
-Copyright: 1998-2014 Xavier Roche and other contributors
+Files: src/md5.c
+Copyright: 1993 Colin Plumb
+License: public-domain-md5
+ This code implements the MD5 message-digest algorithm, due to Ron Rivest.
+ It was written by Colin Plumb in 1993, no copyright is claimed. This code
+ is in the public domain; do with it what you wish.
 
-This program is free software: you can redistribute it and/or modify
-it under the terms of the GNU General Public License as published by
-the Free Software Foundation, either version 3 of the License, or
-(at your option) any later version.
+Files: src/coucal/*
+Copyright: 2013-2014 Xavier Roche
+License: BSD-3-clause
 
-On Debian systems, the complete text of the GNU General Public
-License version 3 can be found in /usr/share/common-licenses/GPL-3 file.
+Files: src/coucal/murmurhash3.h*
+Copyright: Austin Appleby
+License: public-domain-murmurhash3
+ MurmurHash3 was written by Austin Appleby, and is placed in the public
+ domain. The author hereby disclaims copyright to this source code.
 
-This program is distributed in the hope that it will be useful,
-but WITHOUT ANY WARRANTY; without even the implied warranty of
-MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
-GNU General Public License for more details.
+Files: html/server/div/com.httrack.WebHTTrack.metainfo.xml
+Copyright: 1998-2026 Xavier Roche and other contributors
+License: FSFAP
+ Copying and distribution of this file, with or without modification, are
+ permitted in any medium without royalty provided the copyright notice and
+ this notice are preserved. This file is offered as-is, without any warranty.
+
+Files: debian/*
+Copyright: 2002-2026 Xavier Roche <xavier@debian.org>
+License: GPL-3+
+
+License: GPL-3+
+ This program is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+ .
+ This program is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ GNU General Public License for more details.
+ .
+ You should have received a copy of the GNU General Public License
+ along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ .
+ On Debian systems, the complete text of the GNU General Public License
+ version 3 can be found in /usr/share/common-licenses/GPL-3.
+
+License: Zlib
+ This software is provided 'as-is', without any express or implied warranty.
+ In no event will the authors be held liable for any damages arising from the
+ use of this software.
+ .
+ Permission is granted to anyone to use this software for any purpose,
+ including commercial applications, and to alter it and redistribute it
+ freely, subject to the following restrictions:
+ .
+ 1. The origin of this software must not be misrepresented; you must not claim
+    that you wrote the original software. If you use this software in a product,
+    an acknowledgment in the product documentation would be appreciated but is
+    not required.
+ 2. Altered source versions must be plainly marked as such, and must not be
+    misrepresented as being the original software.
+ 3. This notice may not be removed or altered from any source distribution.
+
+License: BSD-3-clause
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+ .
+ 1. Redistributions of source code must retain the above copyright notice,
+    this list of conditions and the following disclaimer.
+ 2. Redistributions in binary form must reproduce the above copyright notice,
+    this list of conditions and the following disclaimer in the documentation
+    and/or other materials provided with the distribution.
+ 3. Neither the name of the copyright holder nor the names of its contributors
+    may be used to endorse or promote products derived from this software
+    without specific prior written permission.
+ .
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
+ LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ POSSIBILITY OF SUCH DAMAGE.

debian/libhttrack3.files

@@ -0,0 +1,3 @@
+usr/lib/*/libhttrack.so.3*
+usr/lib/*/libhtsjava.so.3*
+usr/share/httrack/templates

debian/libhttrack3.lintian-overrides

@@ -1,3 +1,3 @@
 # The shared libraries ship without a versioned symbols control file (ABI is
 # tracked via the SONAME plus a >= upstream-version dependency, see debian/rules).
-libhttrack4: no-symbols-control-file usr/lib/*
+libhttrack3: no-symbols-control-file usr/lib/*

debian/libhttrack4.files

@@ -1,3 +0,0 @@
-usr/lib/*/libhttrack.so.4*
-usr/lib/*/libhtsjava.so.4*
-usr/share/httrack/templates

debian/rules

@@ -135,7 +135,7 @@ binary-arch: build install
 	dh_makeshlibs -a -X/usr/lib/$(DEB_HOST_MULTIARCH)/httrack/libtest --version-info
 	dh_installdeb -a
 	# we depend on the current version (ABI may change)
-	dh_shlibdeps -a -ldebian/libhttrack4/usr/lib/$(DEB_HOST_MULTIARCH)
+	dh_shlibdeps -a -ldebian/libhttrack3/usr/lib/$(DEB_HOST_MULTIARCH)
 	dh_gencontrol -a
 	dh_md5sums -a
 	dh_builddeb -a

history.txt

@@ -4,6 +4,12 @@ HTTrack Website Copier release history:
 
 This file lists all changes and fixes that have been made for HTTrack
 
+3.49-9
++ Fixed: file-type detection from the Content-Type header: trust a declared type over a binary URL extension, honor --assume under the delayed type check, and keep a known extension against a bogus or empty Content-Type (#267, #29, #56)
++ Fixed: an uninitialized-buffer read when the Content-Type is empty (#411)
++ Fixed: restored C++ source-compatibility of the installed headers so reverse dependencies (httraqt) build again (#413)
++ Changed: multiple internal build, packaging and test-harness improvements
+
 3.49-8
 + New: tunnel HTTPS downloads through the configured HTTP proxy via CONNECT (#85)
 + New: parse every candidate URL in <img> and <source> srcset lists (#326)

src/Makefile.am

@@ -56,7 +56,7 @@ whttrackrundir = $(bindir)
 whttrackrun_SCRIPTS = webhttrack
 
 libhttrack_la_SOURCES =  htscore.c htsparse.c htsback.c htscache.c \
-	htscache_selftest.c \
+	htscache_selftest.c htsdns_selftest.c \
 	htscatchurl.c htsfilters.c htsftp.c htshash.c coucal/coucal.c \
 	htshelp.c htslib.c htscoremain.c \
 	htsname.c htsrobots.c htstools.c htswizard.c \
@@ -66,7 +66,7 @@ libhttrack_la_SOURCES =  htscore.c htsparse.c htsback.c htscache.c \
 	md5.c \
 	minizip/ioapi.c minizip/mztools.c minizip/unzip.c minizip/zip.c \
 	hts-indextmpl.h htsalias.h htsback.h htsbase.h htssafe.h \
-	htsbasenet.h htsbauth.h htscache.h htscache_selftest.h htscatchurl.h  \
+	htsbasenet.h htsbauth.h htscache.h htscache_selftest.h htsdns_selftest.h htscatchurl.h  \
 	htsconfig.h htscore.h htsparse.h htscoremain.h htsdefines.h  \
 	htsfilters.h htsftp.h htsglobal.h htshash.h coucal/coucal.h \
 	htshelp.h htsindex.h htslib.h htsmd5.h \

src/htsback.c

@@ -73,6 +73,8 @@ struct_back *back_new(httrackp *opt, int back_max) {
 
   sback->count = back_max;
   sback->lnk = (lien_back *) calloct((back_max + 1), sizeof(lien_back));
+  sback->connect_fallback = (hts_connect_fallback *) calloct(
+      (back_max + 1), sizeof(hts_connect_fallback));
   sback->ready = coucal_new(0);
   hts_set_hash_handler(sback->ready, opt);
   coucal_set_name(sback->ready, "back_new");
@@ -83,6 +85,7 @@ struct_back *back_new(httrackp *opt, int back_max) {
     sback->lnk[i].r.location = sback->lnk[i].location_buffer;
     sback->lnk[i].status = STATUS_FREE;
     sback->lnk[i].r.soc = INVALID_SOCKET;
+    sback->connect_fallback[i].addr_count = -1; // not yet probed
   }
   return sback;
 }
@@ -93,6 +96,7 @@ void back_free(struct_back ** sback) {
       freet((*sback)->lnk);
       (*sback)->lnk = NULL;
     }
+    freet((*sback)->connect_fallback);
     if ((*sback)->ready != NULL) {
       coucal_delete(&(*sback)->ready);
       (*sback)->ready_size_bytes = 0;
@@ -102,6 +106,72 @@ void back_free(struct_back ** sback) {
   }
 }
 
+/* Per-candidate connect deadline cap (seconds): a connecting slot with another
+   address to try waits at most this long before falling back, instead of the
+   full (default 120s) slot timeout. Caps the dead-IPv6 stall while staying well
+   above a normal handshake. The last candidate still gets the full timeout. */
+#define HTS_CONNECT_FALLBACK_TIMEOUT 10
+
+int back_connect_fallback_due(int addr_index, int addr_count, int elapsed,
+                              int timeout) {
+  int deadline;
+
+  if (addr_index + 1 >= addr_count) // last (or only) candidate: no fallback
+    return 0;
+  if (timeout <= 0) // no timeout management: never force it
+    return 0;
+  deadline = (timeout < HTS_CONNECT_FALLBACK_TIMEOUT)
+                 ? timeout
+                 : HTS_CONNECT_FALLBACK_TIMEOUT;
+  return elapsed >= deadline;
+}
+
+/* Pending-connect result for a non-blocking socket reported ready by select():
+   0 = connected, >0 = the connect errno (refused, unreachable, ...), -1 if the
+   probe itself failed. A failed connect is reported writable too, so this is
+   how success is told from failure without blocking. */
+static int connect_socket_error(T_SOC soc) {
+  int soerr = 0;
+  socklen_t len = (socklen_t) sizeof(soerr);
+
+  if (getsockopt(soc, SOL_SOCKET, SO_ERROR, (char *) &soerr, &len) != 0)
+    return -1;
+  return soerr;
+}
+
+/* Retry a stuck/failed connecting slot against its next resolved address.
+   Closes the current socket and starts a non-blocking connect to the next
+   candidate, leaving the slot in STATUS_CONNECTING. Returns 1 if a new connect
+   was started, 0 if no fallback address remains (caller fails the slot). */
+static int back_connect_next(httrackp *opt, struct_back *sback, int i) {
+  hts_connect_fallback *const cf = &sback->connect_fallback[i];
+  lien_back *const back = sback->lnk;
+  const int next = cf->addr_index + 1;
+  T_SOC soc;
+
+  if (next >= cf->addr_count)
+    return 0;
+
+  if (back[i].r.soc != INVALID_SOCKET) {
+    deletehttp(&back[i].r);
+    back[i].r.soc = INVALID_SOCKET;
+  }
+  soc = newhttp_addr(opt, back[i].url_adr, &back[i].r, -1, 0, next, NULL);
+  if (soc == INVALID_SOCKET)
+    return 0;
+
+  back[i].r.soc = soc;
+  cf->addr_index = next;
+  cf->connect_start = time_local();
+  if (back[i].timeout > 0)
+    back[i].timeout_refresh = cf->connect_start;
+  back[i].status = STATUS_CONNECTING;
+  hts_log_print(opt, LOG_DEBUG,
+                "connect failed, trying next address (%d/%d) for %s", next + 1,
+                cf->addr_count, back[i].url_adr);
+  return 1;
+}
+
 void back_delete_all(httrackp * opt, cache_back * cache, struct_back * sback) {
   if (sback != NULL) {
     int i;
@@ -1911,8 +1981,11 @@ int back_add(struct_back * sback, httrackp * opt, cache_back * cache, const char
       // ouvrir liaison, envoyer requète
       // ne pas traiter ou recevoir l'en tête immédiatement
       hts_init_htsblk(&back[p].r);
-      //memset(&(back[p].r), 0, sizeof(htsblk)); 
+      // memset(&(back[p].r), 0, sizeof(htsblk));
       back[p].r.location = back[p].location_buffer;
+      // fresh connect: address list not yet probed, start at the first
+      sback->connect_fallback[p].addr_index = 0;
+      sback->connect_fallback[p].addr_count = -1;
       // recopier proxy
       if ((back[p].r.req.proxy.active = opt->proxy.active)) {
         if (StringBuff(opt->proxy.bindhost) != NULL)
@@ -2369,21 +2442,25 @@ void back_wait(struct_back * sback, httrackp * opt, cache_back * cache,
       // en cas de gestion du connect préemptif
 #if HTS_XCONN
       if (back[i].status == STATUS_CONNECTING) {        // connexion
-        do_wait = 1;
+        // a connecting slot always carries a live socket; guard anyway so a
+        // stray INVALID_SOCKET can never reach FD_SET (mirrors the recv branch)
+        if (back[i].r.soc != INVALID_SOCKET) {
+          do_wait = 1;
 
-        // noter socket write
-        FD_SET(back[i].r.soc, &fds_c);
+          // noter socket write
+          FD_SET(back[i].r.soc, &fds_c);
 
-        // noter socket erreur
-        FD_SET(back[i].r.soc, &fds_e);
+          // noter socket erreur
+          FD_SET(back[i].r.soc, &fds_e);
 
-        // calculer max
-        if (max_c) {
-          max_c = 0;
-          nfds = back[i].r.soc;
-        } else if (back[i].r.soc > nfds) {
-          // ID socket la plus élevée
-          nfds = back[i].r.soc;
+          // calculer max
+          if (max_c) {
+            max_c = 0;
+            nfds = back[i].r.soc;
+          } else if (back[i].r.soc > nfds) {
+            // ID socket la plus élevée
+            nfds = back[i].r.soc;
+          }
         }
 
       } else
@@ -2517,8 +2594,20 @@ void back_wait(struct_back * sback, httrackp * opt, cache_back * cache,
       }
       // ---- FLAG WRITE MIS A UN?: POUR LE CONNECT
       if (back[i].status == STATUS_CONNECTING) {        // attendre connect
+        hts_connect_fallback *const cf = &sback->connect_fallback[i];
         int dispo = 0;
 
+        // probe the resolved address list once per fresh connect (cache hit:
+        // the host was resolved when this connect was opened)
+        if (cf->addr_count < 0 && back[i].r.soc != INVALID_SOCKET &&
+            !back[i].r.is_file) {
+          SOCaddr scratch[HTS_MAXADDRNUM];
+
+          cf->addr_count = hts_dns_resolve_all(opt, back[i].url_adr, scratch,
+                                               HTS_MAXADDRNUM, NULL);
+          cf->connect_start = time_local();
+        }
+
         // vérifier l'existance de timeout-check
         if (!gestion_timeout)
           if (back[i].timeout > 0)
@@ -2526,7 +2615,20 @@ void back_wait(struct_back * sback, httrackp * opt, cache_back * cache,
 
         // connecté?
         dispo = FD_ISSET(back[i].r.soc, &fds_c);
-        if (dispo) {            // ok connected!!
+        if (dispo) { // socket ready: connect() finished (ok or failed)
+          // a refused/failed connect is reported writable too; probe SO_ERROR
+          // and, on failure, fall back to the next address (or fail the slot)
+          if (connect_socket_error(back[i].r.soc) != 0) {
+            if (!back_connect_next(opt, sback, i)) {
+              deletehttp(&back[i].r);
+              back[i].r.soc = INVALID_SOCKET;
+              back[i].r.statuscode = STATUSCODE_CONNERROR;
+              strcpybuff(back[i].r.msg, "Connect Error");
+              back[i].status = STATUS_READY;
+              back_set_finished(sback, i);
+            }
+            continue; // reconnected (stay connecting) or failed
+          }
           busy_state = 1;
 
 #if HTS_USEOPENSSL
@@ -3884,6 +3986,29 @@ void back_wait(struct_back * sback, httrackp * opt, cache_back * cache,
 
         if (back[i].status > 0) {       // réception/connexion/..
           if (back[i].timeout > 0) {
+            // a stuck connect with a fallback address: retry the next one well
+            // before the full timeout (dead IPv6 on a dual-stack host, ...)
+            if (back[i].status == STATUS_CONNECTING) {
+              const hts_connect_fallback *const cf =
+                  &sback->connect_fallback[i];
+
+              if (back_connect_fallback_due(cf->addr_index, cf->addr_count,
+                                            (int) (act - cf->connect_start),
+                                            back[i].timeout)) {
+                if (back_connect_next(opt, sback, i)) {
+                  continue; // reconnected to the next candidate
+                }
+                // fallback was due but no socket could be opened
+                // (back_connect_next closed the dead one): stop now rather than
+                // spin on an invalid fd
+                back[i].r.soc = INVALID_SOCKET;
+                back[i].r.statuscode = STATUSCODE_CONNERROR;
+                strcpybuff(back[i].r.msg, "Connect Error");
+                back[i].status = STATUS_READY;
+                back_set_finished(sback, i);
+                continue;
+              }
+            }
             //printf("time check %d\n",((int) (act-back[i].timeout_refresh))-back[i].timeout);
             if (((int) (act - back[i].timeout_refresh)) >= back[i].timeout) {
               hts_log_print(opt, LOG_DEBUG, "connection timed out for %s%s", back[i].url_adr,

src/htscore.c

@@ -3703,9 +3703,9 @@ HTSEXT_API int copy_htsopt(const httrackp * from, httrackp * to) {
   if (from->maxsoc > 0)
     to->maxsoc = from->maxsoc;
 
-  /* hts_boolean/enum fields are unsigned (GCC), so a bare `> -1` unset-guard
-     is always false; cast to int to keep the -1 "unset" sentinel test. */
-  if ((int) from->nearlink > -1)
+  /* hts_tristate fields use HTS_DEFAULT (-1) for "unspecified": copy_htsopt
+     skips them so the target keeps its value. */
+  if (from->nearlink > -1)
     to->nearlink = from->nearlink;
 
   if (from->timeout > -1)
@@ -3732,10 +3732,10 @@ HTSEXT_API int copy_htsopt(const httrackp * from, httrackp * to) {
   if (from->hostcontrol > -1)
     to->hostcontrol = from->hostcontrol;
 
-  if ((int) from->errpage > -1)
+  if (from->errpage > -1)
     to->errpage = from->errpage;
 
-  if ((int) from->parseall > -1)
+  if (from->parseall > -1)
     to->parseall = from->parseall;
 
   // test all: bit 8 de travel

src/htscore.h

@@ -152,6 +152,15 @@ struct lien_adrfilsave {
   char save[HTS_URLMAXSIZE * 2]; /**< local save path (with directory) */
 };
 
+/** Per-slot connect-fallback bookkeeping (parallel to struct_back.lnk).
+    Tracks which resolved address the slot is currently connecting to so a
+    stuck connect can be retried against the next one. */
+typedef struct hts_connect_fallback {
+  int addr_index;       /**< candidate being connected (0-based) */
+  int addr_count;       /**< resolved addresses; -1 = not yet probed */
+  TStamp connect_start; /**< when the current candidate's connect began */
+} hts_connect_fallback;
+
 /** The download-slot ring: the set of concurrent transfers in flight.
     Allocated/owned by the engine; consumers (status callbacks, the loop)
     read it but do not resize or free it. */
@@ -168,6 +177,7 @@ struct struct_back {
   int count;              /**< number of usable slots (back_max) */
   coucal ready;           /**< index of slots whose transfer completed */
   LLint ready_size_bytes; /**< total bytes buffered in completed slots */
+  hts_connect_fallback *connect_fallback; /**< per-slot, count+1 entries */
 };
 
 typedef struct cache_back_zip_entry cache_back_zip_entry;
@@ -372,6 +382,13 @@ void check_rate(TStamp stat_timestart, int maxrate);
 /* Backing (download-slot) scheduler. Operate on the back[] ring (struct_back).
    Not thread-safe; call from the single crawl loop. */
 
+/* True if a connecting slot should give up on the current address and try the
+   next one: a fallback address remains (addr_index+1 < addr_count) and the
+   candidate has been connecting for at least its deadline, min(timeout, an
+   internal cap). elapsed/timeout in seconds. Exposed for the -#D self-test. */
+int back_connect_fallback_due(int addr_index, int addr_count, int elapsed,
+                              int timeout);
+
 /* How many new sockets may be opened now, honoring maxsoc and the maxconn rate
    limit (>=0). _strict ignores reserved-slot headroom; the plain form leaves
    room for naming tests and stops at 0 when the stack is nearly full. */

src/htscoremain.c

@@ -47,6 +47,7 @@ Please visit our Website: http://www.httrack.com
 #include "htscharset.h"
 #include "htsencoding.h"
 #include "htscache_selftest.h"
+#include "htsdns_selftest.h"
 #include "htsmd5.h"
 
 #include <ctype.h>
@@ -2460,6 +2461,13 @@ static int hts_main_internal(int argc, char **argv, httrackp * opt) {
                   return 1;
                 }
                 break;
+              case 'D': { // DNS resolver/cache self-test (mock getaddrinfo)
+                const int err = dns_selftests(opt);
+
+                printf("dns-selftest: %s\n", err ? "FAIL" : "OK");
+                htsmain_free();
+                return err;
+              } break;
               case 'C':        // list cache files : httrack -#C '*spid*.gif' will attempt to find the matching file
                 {
                   int hasFilter = 0;
@@ -2579,7 +2587,7 @@ static int hts_main_internal(int argc, char **argv, httrackp * opt) {
                                         (r.size >= 0) ? r.size : (-r.size));
                                 if (r.contenttype >= 0) {
                                   fprintf(stdout, "Content-Type: %s\r\n",
-                                          r.contenttype);
+                                          hts_effective_mime(r.contenttype));
                                 }
                                 if (r.cdispo[0]) {
                                   fprintf(stdout, "Content-Disposition: %s\r\n",
@@ -3166,6 +3174,16 @@ static int hts_main_internal(int argc, char **argv, httrackp * opt) {
                 if (to->parseall != HTS_FALSE)
                   err = 1;
 
+                /* HTS_DEFAULT (-1) is "unspecified": copy_htsopt must skip it,
+                   leaving the target intact. Only a signed (int-backed) field
+                   can hold -1, so this also guards the type against regressing
+                   to an unsigned hts_boolean. */
+                from->parseall = HTS_DEFAULT;
+                to->parseall = HTS_TRUE;
+                copy_htsopt(from, to);
+                if (to->parseall != HTS_TRUE)
+                  err = 1;
+
                 hts_free_opt(from);
                 hts_free_opt(to);
                 printf("copy-htsopt: %s\n", err ? "FAIL" : "OK");

src/htsdns_selftest.c

@@ -0,0 +1,359 @@
+/* ------------------------------------------------------------ */
+/*
+HTTrack Website Copier, Offline Browser for Windows and Unix
+Copyright (C) 2026 Xavier Roche and other contributors
+
+SPDX-License-Identifier: GPL-3.0-or-later
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Ethical use: we kindly ask that you NOT use this software to harvest email
+addresses or to collect any other private information about people. Doing so
+would dishonor our work and waste the many hours we have spent on it.
+
+Please visit our Website: http://www.httrack.com
+*/
+
+/* ------------------------------------------------------------ */
+/* File: htsdns_selftest.c subroutines:                         */
+/*       in-process self-test for the DNS resolver and cache    */
+/* Author: Xavier Roche                                         */
+/* ------------------------------------------------------------ */
+
+/* Routes the resolver through a scripted getaddrinfo (hts_resolver_backend)
+   instead of the network, so resolution and the DNS cache are testable for a
+   fixed set of scenarios (IPv4/IPv6/dual-stack, errors, family filter,
+   cache reuse) with no live DNS. */
+
+#define HTS_INTERNAL_BYTECODE
+
+#include "htsdns_selftest.h"
+
+#include "htscore.h"
+#include "htslib.h"
+#include "htsnet.h"
+
+#include <stdio.h>
+#include <string.h>
+
+#if HTS_INET6 != 0
+
+/* IPV6_resolver: 0 = v4+v6, 1 = v4 only, 2 = v6 only (htscoremain -@i). */
+extern int IPV6_resolver;
+
+/* One scripted host: either a getaddrinfo error, or an ordered address list. */
+typedef struct mock_addr {
+  int family;             /* AF_INET / AF_INET6 */
+  unsigned char addr[16]; /* 4 (v4) or 16 (v6) meaningful bytes */
+} mock_addr;
+
+typedef struct mock_host {
+  const char *name;
+  int gai_err; /* non-zero: getaddrinfo returns this */
+  int naddr;
+  mock_addr addr[6];
+  int calls; /* times the backend resolved this host */
+} mock_host;
+
+static mock_host mock_hosts[] = {
+    {"v4only.test", 0, 1, {{AF_INET, {1, 2, 3, 4}}}, 0},
+    {"v6only.test", 0, 1, {{AF_INET6, {0x20, 0x01, 0x0d, 0xb8, [15] = 1}}}, 0},
+    /* dual stack, IPv6 first (RFC 6724 order) then IPv4 */
+    {"dual.test",
+     0,
+     2,
+     {{AF_INET6, {0x20, 0x01, 0x0d, 0xb8, [15] = 2}}, {AF_INET, {5, 6, 7, 8}}},
+     0},
+    /* dual stack, IPv4 first: distinguishes "keep the first address" from
+       "prefer a family", so the selection contract is actually pinned. */
+    {"dual4.test",
+     0,
+     2,
+     {{AF_INET, {9, 10, 11, 12}},
+      {AF_INET6, {0x20, 0x01, 0x0d, 0xb8, [15] = 3}}},
+     0},
+    /* more addresses than HTS_MAXADDRNUM: the list must clamp to the cap. */
+    {"many.test",
+     0,
+     6,
+     {{AF_INET, {10, 0, 0, 1}},
+      {AF_INET, {10, 0, 0, 2}},
+      {AF_INET, {10, 0, 0, 3}},
+      {AF_INET, {10, 0, 0, 4}},
+      {AF_INET, {10, 0, 0, 5}},
+      {AF_INET, {10, 0, 0, 6}}},
+     0},
+    {"nodns.test", EAI_NONAME, 0, {{0}}, 0},
+};
+
+static mock_host *mock_find(const char *name) {
+  for (size_t i = 0; i < sizeof(mock_hosts) / sizeof(mock_hosts[0]); i++) {
+    if (strcmp(mock_hosts[i].name, name) == 0)
+      return &mock_hosts[i];
+  }
+  return NULL;
+}
+
+static void mock_reset_calls(void) {
+  for (size_t i = 0; i < sizeof(mock_hosts) / sizeof(mock_hosts[0]); i++)
+    mock_hosts[i].calls = 0;
+}
+
+/* Build one addrinfo node owning its sockaddr (freed by mock_freeaddrinfo). */
+static struct addrinfo *mock_mkai(const mock_addr *a) {
+  struct addrinfo *ai = calloct(1, sizeof(*ai));
+
+  ai->ai_family = a->family;
+  if (a->family == AF_INET) {
+    struct sockaddr_in *sin = calloct(1, sizeof(*sin));
+
+    sin->sin_family = AF_INET;
+    memcpy(&sin->sin_addr, a->addr, 4);
+    ai->ai_addr = (struct sockaddr *) sin;
+    ai->ai_addrlen = sizeof(*sin);
+  } else {
+    struct sockaddr_in6 *sin6 = calloct(1, sizeof(*sin6));
+
+    sin6->sin6_family = AF_INET6;
+    memcpy(&sin6->sin6_addr, a->addr, 16);
+    ai->ai_addr = (struct sockaddr *) sin6;
+    ai->ai_addrlen = sizeof(*sin6);
+  }
+  return ai;
+}
+
+static int mock_getaddrinfo(const char *node, const char *service,
+                            const struct addrinfo *hints,
+                            struct addrinfo **res) {
+  mock_host *const h = mock_find(node);
+  const int want = (hints != NULL) ? hints->ai_family : PF_UNSPEC;
+  struct addrinfo *head = NULL, *tail = NULL;
+
+  (void) service;
+  *res = NULL;
+  if (h == NULL)
+    return EAI_NONAME;
+  h->calls++; /* a real backend hit; a cached host skips this */
+  if (h->gai_err != 0)
+    return h->gai_err;
+  for (int i = 0; i < h->naddr; i++) {
+    if (want != PF_UNSPEC && want != h->addr[i].family)
+      continue; /* honor the requested family (v4/v6 only) */
+    struct addrinfo *const ai = mock_mkai(&h->addr[i]);
+
+    if (head == NULL)
+      head = ai;
+    else
+      tail->ai_next = ai;
+    tail = ai;
+  }
+  if (head == NULL)
+    return EAI_NONAME; /* filtered to empty, as the libc resolver does */
+  *res = head;
+  return 0;
+}
+
+static void mock_freeaddrinfo(struct addrinfo *res) {
+  while (res != NULL) {
+    struct addrinfo *const next = res->ai_next;
+
+    freet(res->ai_addr);
+    freet(res);
+    res = next;
+  }
+}
+
+static const hts_resolver_backend mock_backend = {mock_getaddrinfo,
+                                                  mock_freeaddrinfo};
+
+static int failures = 0;
+
+#define CHECK(cond)                                                            \
+  do {                                                                         \
+    if (!(cond)) {                                                             \
+      failures++;                                                              \
+      fprintf(stderr, "dns-selftest: FAIL at %s:%d: %s\n", __FILE__, __LINE__, \
+              #cond);                                                          \
+    }                                                                          \
+  } while (0)
+
+/* Resolve via the uncached entry point; return the address family, or
+   AF_UNSPEC if the host did not resolve. */
+static int resolve_family_nocache(const char *host) {
+  SOCaddr addr;
+  const char *err = NULL;
+
+  if (hts_dns_resolve_nocache2(host, &addr, &err) == NULL)
+    return AF_UNSPEC;
+  return SOCaddr_sinfamily(addr);
+}
+
+int dns_selftests(httrackp *opt) {
+  failures = 0;
+  hts_dns_set_resolver_backend(&mock_backend);
+
+  /* IPv4-only / IPv6-only hosts map to the right family. */
+  IPV6_resolver = 0;
+  CHECK(resolve_family_nocache("v4only.test") == AF_INET);
+  CHECK(resolve_family_nocache("v6only.test") == AF_INET6);
+
+  /* Dual-stack: the single-address API returns the *first* resolved address.
+     Both orderings pin selection by position, not a family preference. The
+     multi-address API (resolve_all, below) exposes the whole list. */
+  CHECK(resolve_family_nocache("dual.test") == AF_INET6); /* v6 listed first */
+  CHECK(resolve_family_nocache("dual4.test") == AF_INET); /* v4 listed first */
+
+  /* Unknown host does not resolve. */
+  CHECK(resolve_family_nocache("nodns.test") == AF_UNSPEC);
+
+  /* Family filter (-@i4 / -@i6) selects v4 / v6 out of the dual-stack host. */
+  IPV6_resolver = 1;
+  CHECK(resolve_family_nocache("dual.test") == AF_INET);
+  IPV6_resolver = 2;
+  CHECK(resolve_family_nocache("dual.test") == AF_INET6);
+  IPV6_resolver = 0;
+
+  /* Cached driver resolves a host once and reuses the *same* address. */
+  mock_reset_calls();
+  {
+    SOCaddr a1, a2;
+    char ip1[64], ip2[64];
+    const char *err = NULL;
+
+    CHECK(hts_dns_resolve2(opt, "v4only.test", &a1, &err) != NULL);
+    CHECK(hts_dns_resolve2(opt, "v4only.test", &a2, &err) != NULL);
+    CHECK(mock_find("v4only.test")->calls == 1);
+    /* the cache returns the right address, not merely a hit for the key */
+    SOCaddr_inetntoa(ip1, sizeof(ip1), a1);
+    SOCaddr_inetntoa(ip2, sizeof(ip2), a2);
+    CHECK(strcmp(ip1, "1.2.3.4") == 0);
+    CHECK(strcmp(ip1, ip2) == 0);
+  }
+
+  /* A negative result is cached too: a second lookup does not re-resolve. */
+  {
+    SOCaddr a1, a2;
+    const char *err = NULL;
+
+    CHECK(hts_dns_resolve2(opt, "nodns.test", &a1, &err) == NULL);
+    CHECK(hts_dns_resolve2(opt, "nodns.test", &a2, &err) == NULL);
+    CHECK(mock_find("nodns.test")->calls == 1); /* resolved once, then cached */
+  }
+
+  /* Multi-address resolution: count and order are the connect-fallback
+     contract. A dead first address is retried against the next, so both must be
+     exact. */
+  mock_reset_calls();
+  {
+    SOCaddr addrs[HTS_MAXADDRNUM];
+    char ip[64];
+    const char *err = NULL;
+
+    /* dual-stack, in resolver order: [0]=v6, [1]=v4 */
+    CHECK(hts_dns_resolve_all(opt, "dual.test", addrs, HTS_MAXADDRNUM, &err) ==
+          2);
+    CHECK(SOCaddr_sinfamily(addrs[0]) == AF_INET6);
+    CHECK(SOCaddr_sinfamily(addrs[1]) == AF_INET);
+    SOCaddr_inetntoa(ip, sizeof(ip), addrs[1]);
+    CHECK(strcmp(ip, "5.6.7.8") == 0);
+    CHECK(mock_find("dual.test")->calls ==
+          1); /* one backend hit for the list */
+
+    /* single-address host: count 1 */
+    CHECK(hts_dns_resolve_all(opt, "v4only.test", addrs, HTS_MAXADDRNUM,
+                              &err) == 1);
+    SOCaddr_inetntoa(ip, sizeof(ip), addrs[0]);
+    CHECK(strcmp(ip, "1.2.3.4") == 0);
+
+    /* does-not-resolve: count 0 (negative), no addresses */
+    CHECK(hts_dns_resolve_all(opt, "nodns.test", addrs, HTS_MAXADDRNUM, &err) ==
+          0);
+
+    /* more than the cap: the kept list is clamped to HTS_MAXADDRNUM, keeping
+       the FIRST addresses in resolver order (not some other window) */
+    CHECK(hts_dns_resolve_all(opt, "many.test", addrs, HTS_MAXADDRNUM, &err) ==
+          HTS_MAXADDRNUM);
+    SOCaddr_inetntoa(ip, sizeof(ip), addrs[0]);
+    CHECK(strcmp(ip, "10.0.0.1") == 0);
+    SOCaddr_inetntoa(ip, sizeof(ip), addrs[HTS_MAXADDRNUM - 1]);
+    CHECK(strcmp(ip, "10.0.0.4") == 0);
+
+    /* family filter still applies through the list path */
+    IPV6_resolver = 1;
+    CHECK(hts_dns_resolve_all(opt, "dual4.test", addrs, HTS_MAXADDRNUM, &err) ==
+          1);
+    CHECK(SOCaddr_sinfamily(addrs[0]) == AF_INET);
+    IPV6_resolver = 0;
+  }
+
+  /* newhttp_addr() must connect to the addr_index-th address, not always the
+     first: this is what back_connect_next relies on to reach the fallback. */
+  {
+    htsblk r;
+    int count = -1;
+    T_SOC s;
+
+    hts_init_htsblk(&r);
+    s = newhttp_addr(opt, "dual.test", &r, 80, 0, 0, &count);
+    CHECK(count == 2);
+    CHECK(SOCaddr_sinfamily(r.address) == AF_INET6); /* index 0 = v6 */
+    if (s != INVALID_SOCKET)
+      deletesoc(s);
+
+    hts_init_htsblk(&r);
+    count = -1;
+    s = newhttp_addr(opt, "dual.test", &r, 80, 0, 1, &count);
+    CHECK(count == 2);
+    CHECK(SOCaddr_sinfamily(r.address) == AF_INET); /* index 1 = v4 */
+    if (s != INVALID_SOCKET)
+      deletesoc(s);
+
+    /* out-of-range index: no address selected (address stays unset) */
+    hts_init_htsblk(&r);
+    s = newhttp_addr(opt, "dual.test", &r, 80, 0, 2, NULL);
+    CHECK(s == INVALID_SOCKET);
+    if (s != INVALID_SOCKET)
+      deletesoc(s);
+  }
+
+  /* Connect-fallback decision (consumer of the multi-address list): when a
+     stuck connect should abandon the current address for the next one. */
+  {
+    /* no fallback for the last/only candidate, whatever the elapsed time */
+    CHECK(back_connect_fallback_due(0, 1, 9999, 120) == 0);
+    CHECK(back_connect_fallback_due(1, 2, 9999, 120) == 0);
+    CHECK(back_connect_fallback_due(3, 4, 9999, 120) == 0);
+    /* fallback available: wait the per-candidate deadline (cap 10s here) */
+    CHECK(back_connect_fallback_due(0, 2, 9, 120) == 0);
+    CHECK(back_connect_fallback_due(0, 2, 10, 120) == 1);
+    CHECK(back_connect_fallback_due(2, 4, 10, 120) == 1);
+    /* a shorter slot timeout shortens the deadline (min(timeout, cap)) */
+    CHECK(back_connect_fallback_due(0, 2, 4, 5) == 0);
+    CHECK(back_connect_fallback_due(0, 2, 5, 5) == 1);
+    /* no timeout management: never force a fallback */
+    CHECK(back_connect_fallback_due(0, 2, 9999, 0) == 0);
+  }
+
+  hts_dns_set_resolver_backend(NULL);
+  return failures;
+}
+
+#else
+
+int dns_selftests(httrackp *opt) {
+  (void) opt;
+  return 0; /* resolver seam only exists in the IPv6 build */
+}
+
+#endif

src/htsdns_selftest.h

@@ -0,0 +1,51 @@
+/* ------------------------------------------------------------ */
+/*
+HTTrack Website Copier, Offline Browser for Windows and Unix
+Copyright (C) 2026 Xavier Roche and other contributors
+
+SPDX-License-Identifier: GPL-3.0-or-later
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or
+(at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
+
+Ethical use: we kindly ask that you NOT use this software to harvest email
+addresses or to collect any other private information about people. Doing so
+would dishonor our work and waste the many hours we have spent on it.
+
+Please visit our Website: http://www.httrack.com
+*/
+
+/* ------------------------------------------------------------ */
+/* File: htsdns_selftest.h                                      */
+/* Author: Xavier Roche                                         */
+/* ------------------------------------------------------------ */
+
+#ifndef HTSDNS_SELFTEST_DEFH
+#define HTSDNS_SELFTEST_DEFH
+
+#ifdef HTS_INTERNAL_BYTECODE
+
+#ifndef HTS_DEF_FWSTRUCT_httrackp
+#define HTS_DEF_FWSTRUCT_httrackp
+typedef struct httrackp httrackp;
+#endif
+
+/* Drive the DNS resolver and cache through a scripted (mock) getaddrinfo,
+   asserting address family, single-address selection, negative caching, the
+   IPv4/IPv6 family filter, and that a cached host is resolved only once.
+   Returns the number of failed checks (0 == success). */
+int dns_selftests(httrackp *opt);
+
+#endif
+
+#endif

src/htsglobal.h

@@ -43,8 +43,8 @@ Please visit our Website: http://www.httrack.com
    configure.ac, decoupled from these). VERSION is the display form, VERSIONID
    the dotted numeric form, AFF_VERSION the short form shown in footers,
    LIB_VERSION the data/cache format generation. */
-#define HTTRACK_VERSION "3.49-8"
-#define HTTRACK_VERSIONID "3.49.8"
+#define HTTRACK_VERSION "3.49-9"
+#define HTTRACK_VERSIONID "3.49.9"
 #define HTTRACK_AFF_VERSION "3.x"
 #define HTTRACK_LIB_VERSION "2.0"
 
@@ -247,13 +247,23 @@ Please visit our Website: http://www.httrack.com
 #define HTS_NOPARAM "(none)"
 #define HTS_NOPARAM2 "\"(none)\""
 
-/* Boolean flag for option fields and API yes/no returns. An enum (not C bool)
-   so it stays int-sized: option fields keep the httrackp layout/ABI, and a
-   return type stays compatible with the int it replaces. */
+/* Boolean flag for option fields and API yes/no returns. Int-backed, not an
+   enum: an enum makes C++ reject `field = 1` / `f(0)` on the exported fields
+   and params. Int-sized, so the httrackp layout and the ABI are unchanged. */
 #ifndef HTS_DEF_DEFSTRUCT_hts_boolean
 #define HTS_DEF_DEFSTRUCT_hts_boolean
 
-typedef enum hts_boolean { HTS_FALSE = 0, HTS_TRUE = 1 } hts_boolean;
+typedef int hts_boolean;
+#define HTS_FALSE 0
+#define HTS_TRUE 1
+#endif
+
+#ifndef HTS_DEF_DEFSTRUCT_hts_tristate
+#define HTS_DEF_DEFSTRUCT_hts_tristate
+/* Tri-state hts_boolean: HTS_DEFAULT (-1) = "unspecified" (copy_htsopt leaves
+   the target untouched); HTS_FALSE/HTS_TRUE = off/on. */
+typedef int hts_tristate;
+#define HTS_DEFAULT (-1)
 #endif
 
 /* Larger/smaller of two values. Macros: arguments are evaluated twice. */
@@ -398,6 +408,10 @@ typedef int T_SOC;
 /* Buffer size for a printed network address (IPv4 or IPv6, NUL included). */
 #define HTS_MAXADDRLEN 64
 
+/* Max resolved addresses kept per host for connect fallback (dead IPv6 etc.).
+ */
+#define HTS_MAXADDRNUM 4
+
 #ifdef _WIN32
 #else
 #define __cdecl

src/htslib.c

@@ -1396,8 +1396,6 @@ int http_sendhead(httrackp * opt, t_cookie * cookie, int mode,
 void treatfirstline(htsblk * retour, const char *rcvd) {
   const char *a = rcvd;
 
-  retour->contenttype_given = HTS_FALSE; /* set when a Content-Type is seen */
-
   // exemple:
   // HTTP/1.0 200 OK
   if (*a) {
@@ -1425,7 +1423,7 @@ void treatfirstline(htsblk * retour, const char *rcvd) {
           else
             infostatuscode(retour->msg, retour->statuscode);
           // type MIME par défaut2
-          strcpybuff(retour->contenttype, HTS_HYPERTEXT_DEFAULT_MIME);
+          strcpybuff(retour->contenttype, HTS_UNKNOWN_MIME);
         } else {                // pas de code!
           retour->statuscode = STATUSCODE_INVALID;
           strcpybuff(retour->msg, "Unknown response structure");
@@ -1440,7 +1438,7 @@ void treatfirstline(htsblk * retour, const char *rcvd) {
         retour->statuscode = HTTP_OK;
         retour->keep_alive = 0;
         strcpybuff(retour->msg, "Unknown, assuming junky server");
-        strcpybuff(retour->contenttype, HTS_HYPERTEXT_DEFAULT_MIME);
+        strcpybuff(retour->contenttype, HTS_UNKNOWN_MIME);
       } else if (strnotempty(a)) {
         retour->statuscode = STATUSCODE_INVALID;
         strcpybuff(retour->msg, "Unknown (not HTTP/xx) response structure");
@@ -1449,7 +1447,7 @@ void treatfirstline(htsblk * retour, const char *rcvd) {
         retour->statuscode = HTTP_OK;
         retour->keep_alive = 0;
         strcpybuff(retour->msg, "Unknown, assuming junky server");
-        strcpybuff(retour->contenttype, HTS_HYPERTEXT_DEFAULT_MIME);
+        strcpybuff(retour->contenttype, HTS_UNKNOWN_MIME);
       }
     }
   } else {                      // vide!
@@ -1460,7 +1458,7 @@ void treatfirstline(htsblk * retour, const char *rcvd) {
     /* This is dirty .. */
     retour->statuscode = HTTP_OK;
     strcpybuff(retour->msg, "Unknown, assuming junky server");
-    strcpybuff(retour->contenttype, HTS_HYPERTEXT_DEFAULT_MIME);
+    strcpybuff(retour->contenttype, HTS_UNKNOWN_MIME);
   }
 }
 
@@ -1591,16 +1589,14 @@ void treathead(t_cookie * cookie, const char *adr, const char *fil, htsblk * ret
           }
         }
       }
-      // An empty/whitespace Content-Type value yields no token; keep the
-      // default type and the "not given" flag instead of reading uninit tempo.
+      // An empty/whitespace Content-Type value yields no token: keep the
+      // sentinel default rather than reading an uninitialized tempo.
       if (sscanf(rcvd + p, "%s", tempo) == 1) {
         if (strlen(tempo) < sizeof(retour->contenttype) - 2) // pas trop long!!
           strcpybuff(retour->contenttype, tempo);
         else
           strcpybuff(retour->contenttype,
                      "application/octet-stream-unknown"); // erreur
-        retour->contenttype_given =
-            HTS_TRUE; /* server declared a usable type */
       }
     }
   } else if ((p = strfield(rcvd, "Content-Range:")) != 0) {
@@ -2301,14 +2297,27 @@ htsblk http_test(httrackp * opt, const char *adr, const char *fil, char *loc) {
 // peut ouvrir avec des connect() non bloquants: waitconnect=0/1
 T_SOC newhttp(httrackp * opt, const char *_iadr, htsblk * retour, int port,
               int waitconnect) {
+  return newhttp_addr(opt, _iadr, retour, port, waitconnect, 0, NULL);
+}
+
+T_SOC newhttp_addr(httrackp *opt, const char *_iadr, htsblk *retour, int port,
+                   int waitconnect, int addr_index, int *addr_count) {
   T_SOC soc;                    // descipteur de la socket
 
+  if (addr_count != NULL) {
+    *addr_count = 0;
+  }
+
   if (strcmp(_iadr, "file://") != 0) {  /* non fichier */
     SOCaddr server;
+    SOCaddr addrs[HTS_MAXADDRNUM];
+    int naddr;
     const char *error = "unknown error";
 
     // tester un éventuel id:pass et virer id:pass@ si détecté
     const char *const iadr = jump_identification_const(_iadr);
+    const char *resolve_host = iadr;
+    char BIGSTK iadr2[HTS_URLMAXSIZE * 2];
 
     SOCaddr_clear(server);
 
@@ -2330,7 +2339,6 @@ T_SOC newhttp(httrackp * opt, const char *_iadr, htsblk * retour, int port,
 #endif
 
       if (a != NULL) {
-        char BIGSTK iadr2[HTS_URLMAXSIZE * 2];
         int i = -1;
 
         iadr2[0] = '\0';
@@ -2341,18 +2349,19 @@ T_SOC newhttp(httrackp * opt, const char *_iadr, htsblk * retour, int port,
 
         // adresse véritable (sans :xx)
         strncatbuff(iadr2, iadr, (int) (a - iadr));
-
-        // adresse sans le :xx
-        hts_dns_resolve2(opt, iadr2, &server, &error);
-
-      } else {
-
-        // adresse normale (port par défaut par la suite)
-        hts_dns_resolve2(opt, iadr, &server, &error);
+        resolve_host = iadr2;
       }
+    }
 
-    } else {                    // port défini
-      hts_dns_resolve2(opt, iadr, &server, &error);
+    // resolve the full address list and pick the requested candidate; the
+    // scheduler retries the next index when a connect fails (dead IPv6 etc.)
+    naddr =
+        hts_dns_resolve_all(opt, resolve_host, addrs, HTS_MAXADDRNUM, &error);
+    if (addr_count != NULL) {
+      *addr_count = naddr;
+    }
+    if (addr_index >= 0 && addr_index < naddr) {
+      SOCaddr_copy_SOCaddr(server, addrs[addr_index]);
     }
 
     if (!SOCaddr_is_valid(server)) {
@@ -4318,6 +4327,7 @@ int give_mimext(char *s, size_t ssize, const char *st) {
   int ok = 0;
   int j = 0;
 
+  st = hts_effective_mime(st); /* no declared type: derive an html ext */
   s[0] = '\0';
   while((!ok) && (strnotempty(hts_mime[j][1]))) {
     if (strfield2(hts_mime[j][0], st)) {
@@ -4756,144 +4766,299 @@ int hts_read(htsblk * r, char *buff, int size) {
 // -- Gestion cache DNS --
 // 'RX98
 
-// 'capsule' contenant uniquement le cache
-t_dnscache *hts_cache(httrackp * opt) {
+// Free a DNS cache record (coucal value handler).
+static void hts_cache_value_free(coucal_opaque arg, coucal_value value) {
+  void *record = value.ptr;
+
+  (void) arg;
+  freet(record);
+}
+
+// opt's DNS cache hashtable, created on first use. Records (t_dnscache*) are
+// owned by the table and freed by hts_cache_value_free on coucal_delete.
+coucal hts_cache(httrackp *opt) {
   assertf(opt != NULL);
   if (opt->state.dns_cache == NULL) {
-    opt->state.dns_cache = (t_dnscache *) malloct(sizeof(t_dnscache));
-    memset(opt->state.dns_cache, 0, sizeof(t_dnscache));
+    coucal cache = coucal_new(0);
+
+    coucal_set_name(cache, "dns_cache");
+    coucal_value_set_value_handler(cache, hts_cache_value_free, NULL);
+    opt->state.dns_cache = cache;
   }
   assertf(opt->state.dns_cache != NULL);
-  /* first entry is NULL */
-  assertf(opt->state.dns_cache->iadr == NULL);
   return opt->state.dns_cache;
 }
 
-// Free DNS cache.
-void hts_cache_free(t_dnscache *const root) {
-  if (root != NULL) {
-    t_dnscache *cache;
-    for(cache = root; cache != NULL; ) {
-      t_dnscache *const next = cache->next;
-      cache->next = NULL;
-      freet(cache);
-      cache = next;
-    }
-  }
-}
+// MUST BE LOCKED (coucal is not internally serialized vs FTP/web threads)
+// Look up iadr in the DNS cache, filling out[0..min(count,max)-1].
+// Returns: -1 not yet tested; 0 negative-cached (not in DNS); >0 address count.
+static int hts_ghbn_all(coucal cache, const char *const iadr,
+                        SOCaddr *const out, const int max) {
+  void *ptr;
 
-// lock le cache dns pour tout opération d'ajout
-// plus prudent quand plusieurs threads peuvent écrire dedans..
-// -1: status? 0: libérer 1:locker
-
-// MUST BE LOCKED
-// routine pour le cache - retour optionnel à donner à chaque fois
-// NULL: nom non encore testé dans le cache
-// si h_length==0 alors le nom n'existe pas dans le dns
-static SOCaddr* hts_ghbn(const t_dnscache *cache, const char *const iadr, SOCaddr *const addr) {
-  assertf(addr != NULL);
+  assertf(out != NULL);
   assertf(iadr != NULL);
   if (*iadr == '\0') {
-    return NULL;
+    return -1;
   }
-  /* first entry is empty */
-  if (cache->iadr == NULL) {
-    cache = cache->next;
-  }
-  for(; cache != NULL; cache = cache->next) {
-    assertf(cache != NULL);
-    assertf(cache->iadr != NULL);
-    assertf(cache->iadr == (const char*) cache + sizeof(t_dnscache));
-    if (strcmp(cache->iadr, iadr) == 0) {       // ok trouvé
-      if (cache->host_length != 0) {     // entrée valide
-        assertf(cache->host_length <= sizeof(cache->host_addr));
-        SOCaddr_copyaddr2(*addr, cache->host_addr, cache->host_length);
-        return addr;
-      } else {                  // erreur dans le dns, déja vérifié
-        SOCaddr_clear(*addr);
-        return addr;
-      }
+  if (coucal_read_pvoid(cache, iadr, &ptr)) { // ok trouvé
+    const t_dnscache *const record = (const t_dnscache *) ptr;
+    int i;
+
+    assertf(record->host_count <= HTS_MAXADDRNUM);
+    for (i = 0; i < record->host_count && i < max; i++) {
+      assertf(record->host_length[i] <= sizeof(record->host_addr[i]));
+      SOCaddr_copyaddr2(out[i], record->host_addr[i], record->host_length[i]);
     }
+    return record->host_count;
   }
-  return NULL;
+  return -1;
 }
 
-static SOCaddr* hts_dns_resolve_nocache2_(const char *const hostname,
-                                          SOCaddr *const addr, 
-                                          const char **error) {
+#if HTS_INET6 != 0
+/* Active resolver backend; defaults to the libc resolver. The self-test
+   reroutes it to script DNS answers in-process (see
+   hts_dns_set_resolver_backend). */
+static const hts_resolver_backend hts_resolver_libc = {getaddrinfo,
+                                                       freeaddrinfo};
+static const hts_resolver_backend *hts_resolver = &hts_resolver_libc;
+
+void hts_dns_set_resolver_backend(const hts_resolver_backend *backend) {
+  hts_resolver = (backend != NULL) ? backend : &hts_resolver_libc;
+}
+
+/* Debug/test hook: HTTRACK_DEBUG_RESOLVE="host:ip[,ip...]" pins the resolution
+   of `host` to the listed addresses (curl --resolve style), so the connect
+   fallback can be exercised deterministically (a dead address first, a live one
+   next). Any other host resolves normally. Below: an addrinfo backend that owns
+   its chain (its own freeaddrinfo), so a synthesized and a delegated result
+   free the same way. */
+
+/* Deep-copy a libc addrinfo chain into our own allocations. */
+static struct addrinfo *resolver_dup_chain(const struct addrinfo *src) {
+  struct addrinfo *head = NULL, *tail = NULL;
+
+  for (; src != NULL; src = src->ai_next) {
+    struct addrinfo *const ai = calloct(1, sizeof(*ai));
+
+    ai->ai_family = src->ai_family;
+    ai->ai_socktype = src->ai_socktype;
+    ai->ai_protocol = src->ai_protocol;
+    ai->ai_addrlen = src->ai_addrlen;
+    ai->ai_addr = malloct(src->ai_addrlen);
+    memcpy(ai->ai_addr, src->ai_addr, src->ai_addrlen);
+    if (head == NULL)
+      head = ai;
+    else
+      tail->ai_next = ai;
+    tail = ai;
+  }
+  return head;
+}
+
+/* Build one addrinfo node from an IPv4/IPv6 literal, or NULL if it does not
+   parse or is filtered out by want_family (AF_INET/AF_INET6/PF_UNSPEC). */
+static struct addrinfo *resolver_make_ai(const char *ip, int want_family) {
+  struct addrinfo *ai;
+
+  if (strchr(ip, ':') != NULL) { // IPv6 literal
+    struct sockaddr_in6 sa6;
+
+    if (want_family != PF_UNSPEC && want_family != AF_INET6)
+      return NULL;
+    memset(&sa6, 0, sizeof(sa6));
+    if (inet_pton(AF_INET6, ip, &sa6.sin6_addr) != 1)
+      return NULL;
+    sa6.sin6_family = AF_INET6;
+    ai = calloct(1, sizeof(*ai));
+    ai->ai_family = AF_INET6;
+    ai->ai_addrlen = sizeof(sa6);
+    ai->ai_addr = malloct(sizeof(sa6));
+    memcpy(ai->ai_addr, &sa6, sizeof(sa6));
+  } else { // IPv4 literal
+    struct sockaddr_in sa;
+
+    if (want_family != PF_UNSPEC && want_family != AF_INET)
+      return NULL;
+    memset(&sa, 0, sizeof(sa));
+    if (inet_pton(AF_INET, ip, &sa.sin_addr) != 1)
+      return NULL;
+    sa.sin_family = AF_INET;
+    ai = calloct(1, sizeof(*ai));
+    ai->ai_family = AF_INET;
+    ai->ai_addrlen = sizeof(sa);
+    ai->ai_addr = malloct(sizeof(sa));
+    memcpy(ai->ai_addr, &sa, sizeof(sa));
+  }
+  return ai;
+}
+
+static void override_freeaddrinfo(struct addrinfo *res) {
+  while (res != NULL) {
+    struct addrinfo *const next = res->ai_next;
+
+    freet(res->ai_addr);
+    freet(res);
+    res = next;
+  }
+}
+
+static int override_getaddrinfo(const char *node, const char *service,
+                                const struct addrinfo *hints,
+                                struct addrinfo **res) {
+  const char *const spec = getenv("HTTRACK_DEBUG_RESOLVE");
+  const int want = (hints != NULL) ? hints->ai_family : PF_UNSPEC;
+  const char *colon;
+
+  *res = NULL;
+  if (spec != NULL && node != NULL && (colon = strchr(spec, ':')) != NULL &&
+      (size_t) (colon - spec) == strlen(node) &&
+      strncmp(spec, node, colon - spec) == 0) {
+    struct addrinfo *head = NULL, *tail = NULL;
+    char buf[256];
+    char *p;
+
+    buf[0] = '\0';
+    strncatbuff(buf, colon + 1, sizeof(buf) - 1);
+    for (p = strtok(buf, ","); p != NULL; p = strtok(NULL, ",")) {
+      struct addrinfo *const ai = resolver_make_ai(p, want);
+
+      if (ai != NULL) {
+        if (head == NULL)
+          head = ai;
+        else
+          tail->ai_next = ai;
+        tail = ai;
+      }
+    }
+    if (head == NULL)
+      return EAI_NONAME;
+    *res = head;
+    return 0;
+  }
+
+  /* not overridden: delegate to libc, copying into our owned format */
   {
-#if HTS_INET6==0
-    /* IPv4 resolver */
-    struct hostent *const hp = gethostbyname(hostname);
+    struct addrinfo *sys = NULL;
+    int gerr = getaddrinfo(node, service, hints, &sys);
 
-    if (hp != NULL) {
-      SOCaddr_copyaddr2(addr, hp->h_addr_list[0], hp->h_length);
-      return SOCaddr_is_valid(addr) ? &addr : NULL;
-    } else {
-      SOCaddr_clear(*addr);
-    }
-#else
-    /* IPv6 resolver */
-    struct addrinfo *res = NULL;
-    struct addrinfo hints;
-    int gerr;
-
-    SOCaddr_clear(*addr);
-    memset(&hints, 0, sizeof(hints));
-    if (IPV6_resolver == 1)     // V4 only (for bogus V6 entries)
-      hints.ai_family = PF_INET;
-    else if (IPV6_resolver == 2)        // V6 only (for testing V6 only)
-      hints.ai_family = PF_INET6;
-    else                        // V4 + V6
-      hints.ai_family = PF_UNSPEC;
-    hints.ai_socktype = SOCK_STREAM;
-    hints.ai_protocol = IPPROTO_TCP;
-    if ( ( gerr = getaddrinfo(hostname, NULL, &hints, &res) ) == 0) {
-      if (res != NULL) {
-        if (res->ai_addr != NULL && res->ai_addrlen != 0) {
-          SOCaddr_copyaddr2(*addr, res->ai_addr, res->ai_addrlen);
-        }
-      }
-    } else {
-      if (error != NULL) {
-        *error = gai_strerror(gerr);
-      }
-    }
-    if (res) {
-      freeaddrinfo(res);
-    }
-#endif
+    if (gerr != 0)
+      return gerr;
+    *res = resolver_dup_chain(sys);
+    freeaddrinfo(sys);
+    return 0;
   }
-
-  return SOCaddr_is_valid(*addr) ? addr : NULL;
 }
 
-HTSEXT_API SOCaddr* hts_dns_resolve_nocache2(const char *const hostname, 
-                                     SOCaddr *const addr, const char **error) {
-  /* Protection */
-  if (!strnotempty(hostname)) {
-    return NULL;
-  }
+static const hts_resolver_backend hts_resolver_override = {
+    override_getaddrinfo, override_freeaddrinfo};
 
-  /*
-     Strip [] if any : [3ffe:b80:1234:1::1] 
-     The resolver doesn't seem to handle IP6 addresses in brackets
-   */
+/* Install the env override once, unless a backend was already set (self-test).
+ */
+static void hts_resolver_check_env(void) {
+  static int checked = 0;
+
+  if (!checked) {
+    checked = 1;
+    if (hts_resolver == &hts_resolver_libc &&
+        getenv("HTTRACK_DEBUG_RESOLVE") != NULL) {
+      hts_resolver = &hts_resolver_override;
+    }
+  }
+}
+#endif
+
+// Resolve hostname into up to max addresses (resolver/RFC 6724 order), no
+// cache. Returns the count copied into out[0..count-1]; 0 = does not resolve.
+static int hts_dns_resolve_nocache_list_(const char *const hostname,
+                                         SOCaddr *const out, const int max,
+                                         const char **error) {
+  int count = 0;
+
+#if HTS_INET6==0
+  /* IPv4 resolver */
+  struct hostent *const hp = gethostbyname(hostname);
+
+  if (hp != NULL) {
+    char **h;
+
+    for (h = hp->h_addr_list; count < max && h != NULL && *h != NULL; h++) {
+      SOCaddr_clear(out[count]);
+      SOCaddr_copyaddr2(out[count], *h, hp->h_length);
+      if (SOCaddr_is_valid(out[count]))
+        count++;
+    }
+  }
+#else
+  /* IPv6 resolver */
+  struct addrinfo *res = NULL, *cur;
+  struct addrinfo hints;
+  int gerr;
+
+  hts_resolver_check_env();
+  memset(&hints, 0, sizeof(hints));
+  if (IPV6_resolver == 1) // V4 only (for bogus V6 entries)
+    hints.ai_family = PF_INET;
+  else if (IPV6_resolver == 2) // V6 only (for testing V6 only)
+    hints.ai_family = PF_INET6;
+  else // V4 + V6
+    hints.ai_family = PF_UNSPEC;
+  hints.ai_socktype = SOCK_STREAM;
+  hints.ai_protocol = IPPROTO_TCP;
+  if ((gerr = hts_resolver->getaddrinfo(hostname, NULL, &hints, &res)) == 0) {
+    for (cur = res; cur != NULL && count < max; cur = cur->ai_next) {
+      if (cur->ai_addr != NULL && cur->ai_addrlen != 0) {
+        SOCaddr_clear(out[count]);
+        SOCaddr_copyaddr2(out[count], cur->ai_addr, cur->ai_addrlen);
+        if (SOCaddr_is_valid(out[count]))
+          count++;
+      }
+    }
+  } else if (error != NULL) {
+    *error = gai_strerror(gerr);
+  }
+  if (res) {
+    hts_resolver->freeaddrinfo(res);
+  }
+#endif
+
+  return count;
+}
+
+// Strip [] around a literal IPv6 ([3ffe:b80:1234:1::1]) the resolver won't
+// take, then resolve into a list. Returns the count.
+static int hts_dns_resolve_nocache_list(const char *const hostname,
+                                        SOCaddr *const out, const int max,
+                                        const char **error) {
+  if (!strnotempty(hostname) || max <= 0) {
+    return 0;
+  }
   if ((hostname[0] == '[') && (hostname[strlen(hostname) - 1] == ']')) {
-    SOCaddr *ret;
     size_t size = strlen(hostname);
     char *copy = malloct(size + 1);
+    int count;
+
     assertf(copy != NULL);
     copy[0] = '\0';
     strncat(copy, hostname + 1, size - 2);
-    ret =  hts_dns_resolve_nocache2_(copy, addr, error);
+    count = hts_dns_resolve_nocache_list_(copy, out, max, error);
     freet(copy);
-    return ret;
+    return count;
   } else {
-    return hts_dns_resolve_nocache2_(hostname, addr, error);
+    return hts_dns_resolve_nocache_list_(hostname, out, max, error);
   }
 }
 
+HTSEXT_API SOCaddr *hts_dns_resolve_nocache2(const char *const hostname,
+                                             SOCaddr *const addr,
+                                             const char **error) {
+  SOCaddr_clear(*addr);
+  if (hts_dns_resolve_nocache_list(hostname, addr, 1, error) > 0) {
+    return SOCaddr_is_valid(*addr) ? addr : NULL;
+  }
+  return NULL;
+}
+
 HTSEXT_API SOCaddr* hts_dns_resolve_nocache(const char *const hostname, SOCaddr *const addr) {
   return hts_dns_resolve_nocache2(hostname, addr, NULL);
 }
@@ -4904,16 +5069,18 @@ HTSEXT_API int check_hostname_dns(const char *const hostname) {
 }
 
 // Needs locking
-// cache dns interne à HTS // ** FREE A FAIRE sur la chaine
-static SOCaddr* hts_dns_resolve_(httrackp * opt, const char *_iadr,
-                                 SOCaddr *const addr, const char **error) {
+// Internal DNS cache. Fill out[0..count-1] with up to max addresses for _iadr,
+// resolving (and caching the full list) on a miss. Returns the count.
+static int hts_dns_resolve_list_(httrackp *opt, const char *_iadr,
+                                 SOCaddr *const out, const int max,
+                                 const char **error) {
   char BIGSTK iadr[HTS_URLMAXSIZE * 2];
-  t_dnscache *cache = hts_cache(opt);  // adresse du cache
-  SOCaddr *sa;
+  coucal cache = hts_cache(opt); // le cache dns
+  int count;
 
   assertf(opt != NULL);
   assertf(_iadr != NULL);
-  assertf(addr != NULL);
+  assertf(out != NULL);
 
   strcpybuff(iadr, jump_identification_const(_iadr));
   // couper éventuel :
@@ -4925,55 +5092,67 @@ static SOCaddr* hts_dns_resolve_(httrackp * opt, const char *_iadr,
   }
 
   /* get IP from the dns cache */
-  sa = hts_ghbn(cache, iadr, addr);
-  if (sa != NULL) {
-    return SOCaddr_is_valid(*sa) ? sa : NULL;
-  } else {                      // non présent dans le cache dns, tester
-    const size_t iadr_len = strlen(iadr) + 1;
-
-    // find queue
-    for(; cache->next != NULL; cache = cache->next) ;
+  count = hts_ghbn_all(cache, iadr, out, max);
+  if (count >= 0) { // cache hit (0 == negative-cached)
+    return count;
+  } else { // non présent dans le cache dns, tester
+    SOCaddr resolved[HTS_MAXADDRNUM];
+    t_dnscache *record;
+    int i;
 
 #if DEBUGDNS
     printf("resolving (not cached) %s\n", iadr);
 #endif
 
-    sa = hts_dns_resolve_nocache2(iadr, addr, error);     // calculer IP host
+    count = hts_dns_resolve_nocache_list(iadr, resolved, HTS_MAXADDRNUM, error);
 
 #if HTS_WIDE_DEBUG
     DEBUG_W("gethostbyname done\n");
 #endif
 
-    /* attempt to store new entry */
-    cache->next = malloct(sizeof(t_dnscache) + iadr_len);
-    if (cache->next != NULL) {
-      t_dnscache *const next = cache->next;
-      char *const block = (char*) cache->next;
-      char *const str = block + sizeof(t_dnscache);
-      memcpy(str, iadr, iadr_len);
-      next->iadr = str;
-      if (sa != NULL) {
-        next->host_length = SOCaddr_size(*sa);
-        assertf(next->host_length <= sizeof(next->host_addr));
-        memcpy(next->host_addr, &SOCaddr_sockaddr(*sa), next->host_length);
-      } else {
-        next->host_length = 0;      // non existant dans le dns
+    /* attempt to store new entry (coucal owns it and dups the host key) */
+    record = malloct(sizeof(t_dnscache));
+    if (record != NULL) {
+      memset(record, 0, sizeof(*record));
+      record->host_count = count;
+      for (i = 0; i < count; i++) {
+        record->host_length[i] = SOCaddr_size(resolved[i]);
+        assertf(record->host_length[i] <= sizeof(record->host_addr[i]));
+        memcpy(record->host_addr[i], &SOCaddr_sockaddr(resolved[i]),
+               record->host_length[i]);
       }
-      next->next = NULL;
-      return sa;
+      coucal_add_pvoid(cache, iadr, record);
     }
 
-    /* return result if any */
-    return sa;
-  }                             // retour hp du cache
+    /* copy result to caller (cache store may have failed; result still valid)
+     */
+    for (i = 0; i < count && i < max; i++) {
+      SOCaddr_copy_SOCaddr(out[i], resolved[i]);
+    }
+    return count;
+  } // retour hp du cache
 }
 
-SOCaddr* hts_dns_resolve2(httrackp * opt, const char *_iadr, SOCaddr *const addr, const char **error) {
-  SOCaddr *ret;
+int hts_dns_resolve_all(httrackp *opt, const char *iadr, SOCaddr *out, int max,
+                        const char **error) {
+  int count;
+
+  if (!strnotempty(iadr) || max <= 0) {
+    return 0;
+  }
   hts_mutexlock(&opt->state.lock);
-  ret = hts_dns_resolve_(opt, _iadr, addr, error);
+  count = hts_dns_resolve_list_(opt, iadr, out, max, error);
   hts_mutexrelease(&opt->state.lock);
-  return ret;
+  return count;
+}
+
+SOCaddr *hts_dns_resolve2(httrackp *opt, const char *_iadr, SOCaddr *const addr,
+                          const char **error) {
+  SOCaddr_clear(*addr);
+  if (hts_dns_resolve_all(opt, _iadr, addr, 1, error) > 0) {
+    return SOCaddr_is_valid(*addr) ? addr : NULL;
+  }
+  return NULL;
 }
 
 SOCaddr* hts_dns_resolve(httrackp * opt, const char *_iadr, SOCaddr *const addr) {
@@ -5308,6 +5487,11 @@ static int get_loglevel_from_coucal(coucal_loglevel level) {
 static void default_coucal_loghandler(void *arg, coucal_loglevel level, 
                                        const char* format, va_list args) {
 
+  /* informational chatter (hashtable stats on delete, etc.) only when
+     debugging; keep warnings and critical errors always visible. */
+  if (level > coucal_log_warning && hts_dgb_init <= 0) {
+    return;
+  }
   if (level <= coucal_log_warning) {
     fprintf(stderr, "** warning: ");
   }
@@ -5808,14 +5992,14 @@ HTSEXT_API void hts_free_opt(httrackp * opt) {
 
     /* Cache */
     if (opt->state.dns_cache != NULL) {
-      t_dnscache *root;
+      coucal root;
 
       hts_mutexlock(&opt->state.lock);
       root = opt->state.dns_cache;
       opt->state.dns_cache = NULL;
       hts_mutexrelease(&opt->state.lock);
 
-      hts_cache_free(root);
+      coucal_delete(&root); // frees records via hts_cache_value_free
     }
 
     /* Cancel chain */

src/htslib.h

@@ -147,11 +147,13 @@ struct OLD_htsblk {
 #define HTS_DEF_FWSTRUCT_t_dnscache
 typedef struct t_dnscache t_dnscache;
 #endif
+// One DNS cache record, stored as a coucal value keyed by hostname.
 struct t_dnscache {
-  struct t_dnscache *next;
-  const char *iadr;
-  size_t host_length;                   // length ; (4 or 16) ; 0 for error
-  char host_addr[HTS_MAXADDRLEN];
+  // resolved addresses, in resolver (RFC 6724) order; host_count==0 means the
+  // name does not resolve (negative cache). host_count<=HTS_MAXADDRNUM.
+  int host_count;
+  size_t host_length[HTS_MAXADDRNUM]; // sockaddr length of each (16 or 28)
+  char host_addr[HTS_MAXADDRNUM][HTS_MAXADDRLEN];
 };
 
 /* Library internal definictions */
@@ -191,6 +193,13 @@ int http_cookie_header_selftest(t_cookie *cookie, const char *domain,
 //int newhttp(char* iadr,char* err=NULL);
 T_SOC newhttp(httrackp * opt, const char *iadr, htsblk * retour, int port,
               int waitconnect);
+/* Like newhttp(), but connect to the addr_index-th resolved address of the host
+   (0-based) instead of always the first; *addr_count, if non-NULL, is set to
+   the total resolved addresses. newhttp() == newhttp_addr(...,0,NULL). Used by
+   the slot scheduler to try the next address when a connect fails (dead IPv6
+   etc.). */
+T_SOC newhttp_addr(httrackp *opt, const char *iadr, htsblk *retour, int port,
+                   int waitconnect, int addr_index, int *addr_count);
 HTS_INLINE void deletehttp(htsblk * r);
 HTS_INLINE int deleteaddr(htsblk * r);
 HTS_INLINE void deletesoc(T_SOC soc);
@@ -215,9 +224,14 @@ void treatfirstline(htsblk * retour, const char *rcvd);
 
 // sous-fonctions
 LLint http_xfread1(htsblk * r, int bufl);
-HTS_INLINE SOCaddr* hts_dns_resolve2(httrackp * opt, const char *iadr,
-                                     SOCaddr *const addr, 
-                                     const char **error);
+/* Cached resolver: fill out[0..count-1] with up to max addresses for iadr (in
+   resolver order), returning the count (0 = does not resolve, negative-cached).
+   Resolves once per host; later calls read the DNS cache. Must hold no lock
+   (brackets opt->state.lock itself). */
+int hts_dns_resolve_all(httrackp *opt, const char *iadr, SOCaddr *out, int max,
+                        const char **error);
+HTS_INLINE SOCaddr *hts_dns_resolve2(httrackp *opt, const char *iadr,
+                                     SOCaddr *const addr, const char **error);
 HTS_INLINE SOCaddr* hts_dns_resolve(httrackp * opt, const char *iadr,
                                     SOCaddr *const addr);
 HTSEXT_API SOCaddr* hts_dns_resolve_nocache2(const char *const hostname, 
@@ -230,8 +244,9 @@ HTSEXT_API int check_hostname_dns(const char *const hostname);
 int ftp_available(void);
 
 #if HTS_DNSCACHE
-void hts_cache_free(t_dnscache *const cache);
-t_dnscache *hts_cache(httrackp * opt);
+/* Return opt's DNS cache hashtable (hostname -> t_dnscache record), creating it
+   on first use. Records are owned by the table and freed on coucal_delete. */
+coucal hts_cache(httrackp *opt);
 #endif
 
 // outils divers
@@ -481,10 +496,22 @@ HTS_STATIC int strcmpnocase(const char *a, const char *b) {
 
 // is this MIME an hypertext MIME (text/html), html/js-style or other script/text type?
 #define HTS_HYPERTEXT_DEFAULT_MIME "text/html"
+/* Sentinel stored when the server declared no Content-Type. It is html-ish
+   for every type test (so a typeless response still parses/stores as today),
+   but the naming code (wire_patches_ext) treats it as "no declared type" and
+   keeps the URL extension. It rides the cache, so updates name consistently. */
+#define HTS_UNKNOWN_MIME "unknown/unknown"
+/* Map the no-declared-type sentinel back to a real type for any header or
+   record we EMIT or PERSIST, so "unknown/unknown" never reaches a consumer
+   (a served Content-Type, a ProxyTrack .arc record, ...). */
+#define hts_effective_mime(m)                                                  \
+  (strfield2((m), HTS_UNKNOWN_MIME) ? HTS_HYPERTEXT_DEFAULT_MIME : (m))
 
-#define is_html_mime_type(a) \
-  ( (strfield2((a),"text/html")!=0)\
-  || (strfield2((a),"application/xhtml+xml")!=0) \
+#define is_html_mime_type(a)                                                   \
+  ((strfield2((a), "text/html") != 0) ||                                       \
+   (strfield2((a), "application/xhtml+xml") != 0) ||                           \
+   (strfield2((a), HTS_UNKNOWN_MIME) !=                                        \
+    0) /* no declared type: treat as html */                                   \
   )
 #define is_hypertext_mime__(a) \
   ( \

src/htsname.c

@@ -142,10 +142,11 @@ static void cleanEndingSpaceOrDot(char *s) {
    saved file? True when the type is patchable (may_unknown2) and either the URL
    extension implies no specific type or the server declared a disagreeing one.
    A URL extension mapping to a specific non-HTML type is kept only when the
-   server sent NO Content-Type (the #267 mangle guard): a typeless .png stays
-   .png, but a .pdf explicitly served as text/html is named .html. */
+   server declared NO type (the HTS_UNKNOWN_MIME sentinel; the #267 mangle
+   guard): a typeless .png stays .png, but a .pdf explicitly served as text/html
+   is named .html. The sentinel rides the cache, so updates stay consistent. */
 static int wire_patches_ext(httrackp *opt, const char *wiremime,
-                            const char *file, int contenttype_given) {
+                            const char *file) {
   char urlmime[256];
 
   if (may_unknown2(opt, wiremime, file))
@@ -157,11 +158,11 @@ static int wire_patches_ext(httrackp *opt, const char *wiremime,
   if (strfield2(wiremime, urlmime))
     return 0; /* wire agrees with the ext: keep it (no .htm->.html churn) */
   /* wire disagrees with a specific non-HTML URL ext. Keep the ext only when
-     the server sent NO Content-Type: a missing type is defaulted to text/html
-     upstream and must not clobber e.g. a .png. An explicitly declared type is
-     trusted, so a binary-looking URL that really serves HTML (login/error
-     interstitial, soft-404) is named .html instead of kept as .pdf/.jpg. */
-  if (!is_hypertext_mime(opt, urlmime, file) && !contenttype_given)
+     the server declared no type (the sentinel); an explicitly declared type,
+     even text/html, is trusted, so a binary-looking URL that really serves
+     HTML (login/error interstitial, soft-404) is named .html. */
+  if (!is_hypertext_mime(opt, urlmime, file) &&
+      strfield2(wiremime, HTS_UNKNOWN_MIME))
     return 0;
   return 1;
 }
@@ -411,8 +412,7 @@ int url_savename(lien_adrfilsave *const afs,
               if (strnotempty(r.cdispo)) {        /* filename given */
                 ext_chg = 2;      /* change filename */
                 strcpybuff(ext, r.cdispo);
-              } else if (wire_patches_ext(opt, r.contenttype, fil,
-                                          r.contenttype_given)) {
+              } else if (wire_patches_ext(opt, r.contenttype, fil)) {
                 if (give_mimext(s, sizeof(s),
                                 r.contenttype)) { // recognized extension
                   ext_chg = 1;
@@ -458,8 +458,7 @@ int url_savename(lien_adrfilsave *const afs,
                 ext_chg = 2;      /* change filename */
                 strcpybuff(ext, headers->r.cdispo);
               } else if (wire_patches_ext(opt, headers->r.contenttype,
-                                          headers->url_fil,
-                                          headers->r.contenttype_given)) {
+                                          headers->url_fil)) {
                 char s[16];
                 if (give_mimext(
                         s, sizeof(s),
@@ -675,7 +674,8 @@ int url_savename(lien_adrfilsave *const afs,
                 if (!has_been_moved) {
                   if (back[b].r.statuscode != -10) {    // erreur
                     if (strnotempty(back[b].r.contenttype) == 0)
-                      strcpybuff(back[b].r.contenttype, "text/html");   // message d'erreur en html
+                      strcpybuff(back[b].r.contenttype,
+                                 HTS_UNKNOWN_MIME); // no declared type
                     // Finalement on, renvoie un erreur, pour ne toucher à rien dans le code
                     // libérer emplacement backing
                   }
@@ -688,8 +688,7 @@ int url_savename(lien_adrfilsave *const afs,
                       ext_chg = 2;      /* change filename */
                       strcpybuff(ext, back[b].r.cdispo);
                     } else if (wire_patches_ext(opt, back[b].r.contenttype,
-                                                back[b].url_fil,
-                                                back[b].r.contenttype_given)) {
+                                                back[b].url_fil)) {
                       if (give_mimext(
                               s, sizeof(s),
                               back[b].r.contenttype)) { // recognized extension

src/htsnet.h

@@ -304,6 +304,22 @@ static HTS_UNUSED void SOCaddr_inetntoa_(char *namebuf, size_t namebuflen,
 /** Length type for socket APIs (getsockname, accept, ...). */
 typedef socklen_t SOClen;
 
+#if HTS_INET6 != 0
+/** Resolver backend: getaddrinfo/freeaddrinfo as a swappable pair, so the
+    self-test can script DNS answers (families, multiplicity, errors)
+    in-process. The free function must match its getaddrinfo (a fake allocates
+    its own chain), hence the pair. */
+typedef struct hts_resolver_backend {
+  int (*getaddrinfo)(const char *node, const char *service,
+                     const struct addrinfo *hints, struct addrinfo **res);
+  void (*freeaddrinfo)(struct addrinfo *res);
+} hts_resolver_backend;
+
+/** Install a resolver backend for the process; NULL restores the libc default.
+    Test-only seam, not thread-safe; callers must serialize against resolves. */
+void hts_dns_set_resolver_backend(const hts_resolver_backend *backend);
+#endif
+
 #ifdef __cplusplus
 }
 #endif

src/htsopt.h

@@ -241,7 +241,7 @@ struct htsoptstate {
   char *userhttptype;
   int verif_backblue_done; /**< backblue.gif/fade.gif already emitted */
   int verif_external_status;
-  t_dnscache *dns_cache;  /**< DNS resolution cache */
+  coucal dns_cache; /**< DNS resolution cache: hostname -> t_dnscache record */
   int dns_cache_nthreads; /**< number of in-flight DNS resolver threads */
   /* HTML parsing state */
   char _hts_errmsg[HTS_CDLMAXSIZE + 256]; /**< last engine error message */
@@ -428,11 +428,11 @@ struct httrackp {
   LLint maxfile_html;         /**< max bytes per HTML file */
   int maxsoc;                 /**< max simultaneous sockets (-cN) */
   LLint fragment;             /**< split site after this many bytes */
-  hts_boolean
+  hts_tristate
       nearlink; /**< also fetch images/data adjacent to a page but off-site */
   hts_boolean makeindex;  /**< build a top-level index.html */
   hts_boolean kindex;     /**< build a keyword index */
-  hts_boolean delete_old; /**< delete locally obsolete files after update */
+  hts_tristate delete_old; /**< delete locally obsolete files after update */
   int timeout;            /**< connection timeout in seconds */
   int rateout;            /**< minimum transfer rate (bytes/s) before abort */
   int maxtime;            /**< max total mirror duration in seconds */
@@ -465,13 +465,13 @@ struct httrackp {
   hts_boolean maketrack; /**< maintain an operations-statistics log */
   int parsejava;         /**< Java/JS parsing mode; see htsparsejava_flags */
   int hostcontrol; /**< ban slow/timing-out hosts; see hts_hostcontrol bits */
-  hts_boolean errpage; /**< generate an error page on 404 and similar */
+  hts_tristate errpage; /**< generate an error page on 404 and similar */
   hts_boolean
       check_type; /**< probe unknown-type links (cgi/asp/dir) and follow moves
                    */
   hts_boolean all_in_cache;      /**< keep all retrieved data in the cache */
   hts_robots robots;             /**< robots.txt handling level */
-  hts_boolean external;          /**< render external links as error pages */
+  hts_tristate external;         /**< render external links as error pages */
   hts_boolean passprivacy;       /**< strip passwords from external links */
   hts_boolean includequery;      /**< include the query string in saved names */
   hts_boolean mirror_first_page; /**< only mirror the links of the first page */
@@ -485,7 +485,7 @@ struct httrackp {
   hts_boolean sizehack;          /**< treat same-size response as "updated" */
   hts_boolean urlhack;           // force "url normalization" to avoid loops
   hts_boolean tolerant;          /**< accept an incorrect Content-Length */
-  hts_boolean
+  hts_tristate
       parseall; /**< parse aggressively, including unknown tags with links */
   hts_boolean parsedebug; /**< parser debug mode */
   hts_boolean norecatch;  /**< do not re-fetch files the user deleted locally */
@@ -651,8 +651,6 @@ struct htsblk {
   int debugid;           /**< connection debug id */
   /* */
   htsrequest req; /**< parameters used for the request */
-  /* a Content-Type header was received (else contenttype holds a default) */
-  hts_boolean contenttype_given;
   /*char digest[32+2];   // md5 digest generated by the engine ("" if none) */
 };
 

src/proxy/proxytrack.c

@@ -1176,11 +1176,15 @@ static void proxytrack_process_HTTP(PT_Indexes indexes, T_SOC soc_c) {
         if (element != NULL) {
           msgCode = element->statuscode;
           StringRoom(headers, 8192);
-          sprintf(StringBuffRW(headers), "HTTP/1.1 %d %s\r\n"
+          sprintf(StringBuffRW(headers),
+                  "HTTP/1.1 %d %s\r\n"
 #ifndef NO_WEBDAV
                   "%s"
 #endif
-                  "Content-Type: %s%s%s%s\r\n" "%s%s%s" "%s%s%s" "%s%s%s",
+                  "Content-Type: %s%s%s%s\r\n"
+                  "%s%s%s"
+                  "%s%s%s"
+                  "%s%s%s",
                   /* */
                   msgCode, element->msg,
 #ifndef NO_WEBDAV
@@ -1188,16 +1192,18 @@ static void proxytrack_process_HTTP(PT_Indexes indexes, T_SOC soc_c) {
                   StringBuff(davHeaders),
 #endif
                   /* Content-type: foo; [ charset=bar ] */
-                  element->contenttype,
+                  hts_effective_mime(element->contenttype),
                   ((element->charset[0]) ? "; charset=\"" : ""),
                   element->charset, ((element->charset[0]) ? "\"" : ""),
                   /* location */
-                  ((element->location != NULL
-                    && element->location[0]) ? "Location: " : ""),
-                  ((element->location != NULL
-                    && element->location[0]) ? element->location : ""),
-                  ((element->location != NULL
-                    && element->location[0]) ? "\r\n" : ""),
+                  ((element->location != NULL && element->location[0])
+                       ? "Location: "
+                       : ""),
+                  ((element->location != NULL && element->location[0])
+                       ? element->location
+                       : ""),
+                  ((element->location != NULL && element->location[0]) ? "\r\n"
+                                                                       : ""),
                   /* last-modified */
                   ((element->lastmodified[0]) ? "Last-Modified: " : ""),
                   ((element->lastmodified[0]) ? element->lastmodified : ""),
@@ -1205,8 +1211,7 @@ static void proxytrack_process_HTTP(PT_Indexes indexes, T_SOC soc_c) {
                   /* etag */
                   ((element->etag[0]) ? "ETag: " : ""),
                   ((element->etag[0]) ? element->etag : ""),
-                  ((element->etag[0]) ? "\r\n" : "")
-            );
+                  ((element->etag[0]) ? "\r\n" : ""));
           StringLength(headers) = (int) strlen(StringBuff(headers));
         } else {
           /* No query string, no ending / : check the the <url>/ page */

src/proxy/store.c

@@ -52,6 +52,7 @@ Please visit our Website: http://www.httrack.com
 
 #include "htscore.h"
 #include "htsback.h"
+#include "htslib.h" /* hts_effective_mime */
 
 #include "store.h"
 #include "proxystrings.h"
@@ -2289,10 +2290,17 @@ static int PT_SaveCache__Arc_Fun(void *arg, const char *url, PT_Element element)
   int size_headers;
 
   sprintf(st->headers,
-          "HTTP/1.0 %d %s" "\r\n" "X-Server: ProxyTrack " PROXYTRACK_VERSION
-          "\r\n" "Content-type: %s%s%s%s" "\r\n" "Last-modified: %s" "\r\n"
-          "Content-length: %d" "\r\n", element->statuscode, element->msg,
-          /**/ element->contenttype,
+          "HTTP/1.0 %d %s"
+          "\r\n"
+          "X-Server: ProxyTrack " PROXYTRACK_VERSION "\r\n"
+          "Content-type: %s%s%s%s"
+          "\r\n"
+          "Last-modified: %s"
+          "\r\n"
+          "Content-length: %d"
+          "\r\n",
+          element->statuscode, element->msg,
+          /**/ hts_effective_mime(element->contenttype),
           (element->charset[0] ? "; charset=\"" : ""),
           (element->charset[0] ? element->charset : ""),
           (element->charset[0] ? "\"" : ""), /**/ element->lastmodified,
@@ -2328,10 +2336,10 @@ static int PT_SaveCache__Arc_Fun(void *arg, const char *url, PT_Element element)
           /* args */
           (link_has_authority(url) ? "" : "http://"), url, "0.0.0.0",
           tm->tm_year + 1900, tm->tm_mon + 1, tm->tm_mday, tm->tm_hour,
-          tm->tm_min, tm->tm_sec, element->contenttype, element->statuscode,
-          st->md5, (element->location ? element->location : "-"),
-          (long int) ftell(fp), st->filename,
-          (long int) (size_headers + element->size));
+          tm->tm_min, tm->tm_sec, hts_effective_mime(element->contenttype),
+          element->statuscode, st->md5,
+          (element->location ? element->location : "-"), (long int) ftell(fp),
+          st->filename, (long int) (size_headers + element->size));
   /* network_doc */
   if (fwrite(st->headers, 1, size_headers, fp) != size_headers
       || (element->size > 0

tests/01_engine-dns.test

@@ -0,0 +1,15 @@
+#!/bin/bash
+#
+
+set -euo pipefail
+
+# DNS resolver/cache self-test: a mock getaddrinfo (no network) checks address
+# family, single-address selection, the -@i4/-@i6 family filter, and cache reuse.
+# The trailing token is required, like the other -# selftests, so a bare command
+# line isn't treated as "no arguments" and routed to the usage screen.
+out=$(httrack -#D run)
+
+test "$out" = "dns-selftest: OK" || {
+    echo "expected 'dns-selftest: OK', got: $out" >&2
+    exit 1
+}

tests/15_local-types.test

@@ -10,7 +10,7 @@
 : "${top_srcdir:=..}"
 
 bash "$top_srcdir/tests/local-crawl.sh" --errors 0 \
-    --found 'types/notype.png' \
+    --found 'types/notype.png' --not-found 'types/notype.html' \
     --found 'types/notype.pdf' --not-found 'types/notype.html' \
     --found 'types/photo.png' \
     --found 'types/doc.pdf' \

tests/18_local-update.test

@@ -0,0 +1,15 @@
+#!/bin/bash
+#
+# A second (update) pass must keep the names the first crawl chose. The stored
+# Content-Type rides the cache, so the update reads back the same value -- the
+# unknown/unknown sentinel for a typeless response, the declared type otherwise
+# -- and names consistently: a declared-text/html .pdf stays .html and a
+# typeless .png stays .png across the update rather than reverting.
+
+: "${top_srcdir:=..}"
+
+bash "$top_srcdir/tests/local-crawl.sh" --errors 0 --rerun \
+    --found 'types/report.html' --not-found 'types/report.pdf' \
+    --found 'types/notype.png' --not-found 'types/notype.html' \
+    --found 'types/lie.html' \
+    httrack 'BASEURL/types/index.html'

tests/19_local-connect-fallback.test

@@ -0,0 +1,110 @@
+#!/bin/bash
+#
+# A host that resolves to several addresses must fall back to the next one when
+# a connect fails, instead of giving up on the first (dead IPv6 on a dual-stack
+# host, ...). HTTRACK_DEBUG_RESOLVE pins "deadhost" to a refused address first
+# (127.0.0.2, nothing listening) then the live server (127.0.0.1): the crawl
+# only succeeds if httrack retries the second address. A second case pins every
+# address to a refused one, so the slot must exhaust the list and error out
+# (rather than hang or loop).
+
+set -euo pipefail
+
+: "${top_srcdir:=..}"
+
+if test "${V6_SUPPORT:-}" == "no"; then
+    echo "no IPv6 support (resolver list/override is IPv6-only), skipping"
+    exit 77
+fi
+if ! command -v python3 >/dev/null 2>&1; then
+    echo "python3 missing, skipping"
+    exit 77
+fi
+
+server="$top_srcdir/tests/local-server.py"
+root="$top_srcdir/tests/server-root"
+tmpdir=$(mktemp -d)
+serverpid=
+
+cleanup() {
+    if test -n "$serverpid"; then
+        kill "$serverpid" 2>/dev/null || true
+        wait "$serverpid" 2>/dev/null || true
+    fi
+    rm -rf "$tmpdir"
+    return 0
+}
+trap cleanup EXIT
+
+# bind the live server to 127.0.0.1 only, so 127.0.0.2 refuses the connect
+python3 "$server" --root "$root" --bind 127.0.0.1 >"$tmpdir/srv.out" 2>"$tmpdir/srv.err" &
+serverpid=$!
+port=
+for _ in $(seq 1 50); do
+    line=$(head -n1 "$tmpdir/srv.out" 2>/dev/null || true)
+    if test "${line%% *}" == "PORT"; then
+        port="${line#PORT }"
+        break
+    fi
+    kill -0 "$serverpid" 2>/dev/null || {
+        echo "server exited early: $(cat "$tmpdir/srv.err")"
+        exit 1
+    }
+    sleep 0.1
+done
+test -n "$port" || {
+    echo "could not discover server port"
+    exit 1
+}
+
+out="$tmpdir/crawl"
+HTTRACK_DEBUG_RESOLVE="deadhost:127.0.0.2,127.0.0.1" \
+    httrack "http://deadhost:$port/simple/basic.html" -O "$out" \
+    -c1 --robots=0 --timeout=30 --quiet -Z >"$tmpdir/log" 2>&1
+
+log="$out/hts-log.txt"
+
+# the dead address was tried, then the next one (proves the fallback ran)
+if ! grep -q "trying next address" "$log"; then
+    echo "FAIL: no connect fallback happened"
+    cat "$log"
+    exit 1
+fi
+
+# 0 errors and the file was actually fetched (over the live address)
+errs=$(grep -iEc "^[0-9:]*[[:space:]]Error:" "$log" || true)
+test "$errs" == "0" || {
+    echo "FAIL: $errs error(s) reported"
+    grep -iE "Error:" "$log"
+    exit 1
+}
+test -f "$out/deadhost_$port/simple/basic.html" || {
+    echo "FAIL: basic.html not downloaded via fallback"
+    find "$out" -type f
+    exit 1
+}
+
+# every address refused: the slot exhausts the list, then errors out (the
+# harness timeout would catch a hang/loop; refused connects are instant)
+out2="$tmpdir/crawl2"
+HTTRACK_DEBUG_RESOLVE="alldead:127.0.0.2,127.0.0.3" \
+    httrack "http://alldead:$port/simple/basic.html" -O "$out2" \
+    -c1 --robots=0 --timeout=30 --quiet -Z >"$tmpdir/log2" 2>&1
+log2="$out2/hts-log.txt"
+
+grep -q "trying next address" "$log2" || {
+    echo "FAIL: exhaustion path never tried the fallback address"
+    cat "$log2"
+    exit 1
+}
+grep -iqE "^[0-9:]*[[:space:]]Error:" "$log2" || {
+    echo "FAIL: all addresses failing did not report an error"
+    cat "$log2"
+    exit 1
+}
+test ! -f "$out2/alldead_$port/simple/basic.html" || {
+    echo "FAIL: file downloaded despite every address failing"
+    exit 1
+}
+
+echo "OK: connect fallback succeeds, and exhausting all addresses errors out"

tests/Makefile.am

@@ -13,6 +13,7 @@ TESTS_ENVIRONMENT += PATH=$(top_builddir)/src$(PATH_SEPARATOR)$$PATH
 ### TESTS_ENVIRONMENT += $(SHLIBPATH_VAR)="$(top_builddir)/src/$(LT_CV_OBJDIR)$${$(SHLIBPATH_VAR):+$(PATH_SEPARATOR)}$$$(SHLIBPATH_VAR)"
 TESTS_ENVIRONMENT += ONLINE_UNIT_TESTS=$(ONLINE_UNIT_TESTS)
 TESTS_ENVIRONMENT += HTTPS_SUPPORT=$(HTTPS_SUPPORT)
+TESTS_ENVIRONMENT += V6_SUPPORT=$(V6_SUPPORT)
 TESTS_ENVIRONMENT += top_srcdir=$(top_srcdir)
 
 TEST_EXTENSIONS = .test
@@ -29,6 +30,7 @@ TESTS = \
 	01_engine-cmdline.test \
 	01_engine-cookies.test \
 	01_engine-copyopt.test \
+	01_engine-dns.test \
 	01_engine-doitlog.test \
 	01_engine-entities.test \
 	01_engine-filter.test \
@@ -54,6 +56,8 @@ TESTS = \
 	14_local-https.test \
 	15_local-types.test \
 	16_local-assume.test \
-	17_local-empty-ct.test
+	17_local-empty-ct.test \
+	18_local-update.test \
+	19_local-connect-fallback.test
 
 CLEANFILES = check-network_sh.cache

tests/local-crawl.sh

@@ -26,6 +26,7 @@ key="${testdir}/server.key"
 
 tls=
 verbose=
+rerun=
 tmpdir=
 serverpid=
 crawlpid=
@@ -89,6 +90,7 @@ nargs=$#
 while test "$pos" -lt "$nargs"; do
     case "${args[$pos]}" in
     --debug) verbose=1 ;;
+    --rerun) rerun=1 ;; # run httrack a second time (update pass) before auditing
     --no-purge)
         nopurge=1
         audit+=("--no-purge")
@@ -180,6 +182,22 @@ test "$crawlres" -eq 0 || ! result "httrack exited $crawlres" || {
 result "OK"
 grep -iE "^[0-9:]*[[:space:]]Error:" "${out}/hts-log.txt" >&2
 
+# --- optional second pass: re-mirror into the same dir (cache/update path) ----
+if test -n "$rerun"; then
+    info "re-running httrack (update pass)"
+    httrack -O "$out" --user-agent="httrack $ver local ($(uname -omrs))" \
+        "${moreargs[@]}" "${hts[@]}" >"${log}.2" 2>&1 &
+    crawlpid=$!
+    wait "$crawlpid"
+    crawlres=$?
+    crawlpid=
+    test "$crawlres" -eq 0 || ! result "update pass exited $crawlres" || {
+        cat "${log}.2" >&2
+        exit 1
+    }
+    result "OK (update)"
+fi
+
 # --- discover the single host root (127.0.0.1_<port> or 127.0.0.1) -----------
 hostroot=
 for cand in "${out}/127.0.0.1_${port}" "${out}/127.0.0.1"; do