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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:59:48 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-07 15:59:48 +0000
commit3b9b6d0b8e7f798023c9d109c490449d528fde80 (patch)
tree2e1c188dd7b8d7475cd163de9ae02c428343669b /bin/plugins
parentInitial commit. (diff)
downloadbind9-3b9b6d0b8e7f798023c9d109c490449d528fde80.tar.xz
bind9-3b9b6d0b8e7f798023c9d109c490449d528fde80.zip
Adding upstream version 1:9.18.19.upstream/1%9.18.19upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r--bin/plugins/Makefile.am15
-rw-r--r--bin/plugins/Makefile.in847
-rw-r--r--bin/plugins/filter-a.c879
-rw-r--r--bin/plugins/filter-a.rst86
-rw-r--r--bin/plugins/filter-aaaa.c881
-rw-r--r--bin/plugins/filter-aaaa.rst90
6 files changed, 2798 insertions, 0 deletions
diff --git a/bin/plugins/Makefile.am b/bin/plugins/Makefile.am
new file mode 100644
index 0000000..611dd1b
--- /dev/null
+++ b/bin/plugins/Makefile.am
@@ -0,0 +1,15 @@
+include $(top_srcdir)/Makefile.top
+
+AM_CPPFLAGS += \
+ $(LIBISC_CFLAGS) \
+ $(LIBDNS_CFLAGS) \
+ $(LIBNS_CFLAGS) \
+ $(LIBISCCFG_CFLAGS)
+
+pkglib_LTLIBRARIES = filter-aaaa.la
+pkglib_LTLIBRARIES += filter-a.la
+
+filter_aaaa_la_SOURCES = filter-aaaa.c
+filter_a_la_SOURCES = filter-a.c
+filter_aaaa_la_LDFLAGS = -avoid-version -module -shared -export-dynamic
+filter_a_la_LDFLAGS = -avoid-version -module -shared -export-dynamic
diff --git a/bin/plugins/Makefile.in b/bin/plugins/Makefile.in
new file mode 100644
index 0000000..b1d1bb8
--- /dev/null
+++ b/bin/plugins/Makefile.in
@@ -0,0 +1,847 @@
+# Makefile.in generated by automake 1.16.5 from Makefile.am.
+# @configure_input@
+
+# Copyright (C) 1994-2021 Free Software Foundation, Inc.
+
+# This Makefile.in is free software; the Free Software Foundation
+# gives unlimited permission to copy and/or distribute it,
+# with or without modifications, as long as this notice is preserved.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY, to the extent permitted by law; without
+# even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+# PARTICULAR PURPOSE.
+
+@SET_MAKE@
+
+# Hey Emacs, this is -*- makefile-automake -*- file!
+# vim: filetype=automake
+
+VPATH = @srcdir@
+am__is_gnu_make = { \
+ if test -z '$(MAKELEVEL)'; then \
+ false; \
+ elif test -n '$(MAKE_HOST)'; then \
+ true; \
+ elif test -n '$(MAKE_VERSION)' && test -n '$(CURDIR)'; then \
+ true; \
+ else \
+ false; \
+ fi; \
+}
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+ ?) ;; \
+ *) echo "am__make_running_with_option: internal error: invalid" \
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+ exit 1;; \
+ esac; \
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+ else \
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+ *\\[\ \ ]*) \
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+ | sed "s/$$bs$$bs[$$bs $$bs ]*//g"`;; \
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+ case $$flg in \
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+pkglibexecdir = $(libexecdir)/@PACKAGE@
+am__cd = CDPATH="$${ZSH_VERSION+.}$(PATH_SEPARATOR)" && cd
+install_sh_DATA = $(install_sh) -c -m 644
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+INSTALL_HEADER = $(INSTALL_DATA)
+transform = $(program_transform_name)
+NORMAL_INSTALL = :
+PRE_INSTALL = :
+POST_INSTALL = :
+NORMAL_UNINSTALL = :
+PRE_UNINSTALL = :
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+@HOST_MACOS_TRUE@am__append_1 = \
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+
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+ $(top_srcdir)/m4/ax_jemalloc.m4 \
+ $(top_srcdir)/m4/ax_lib_lmdb.m4 \
+ $(top_srcdir)/m4/ax_perl_module.m4 \
+ $(top_srcdir)/m4/ax_posix_shell.m4 \
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+am_filter_a_la_OBJECTS = filter-a.lo
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+ $(LIBTOOLFLAGS) --mode=link $(CCLD) $(AM_CFLAGS) $(CFLAGS) \
+ $(filter_a_la_LDFLAGS) $(LDFLAGS) -o $@
+filter_aaaa_la_LIBADD =
+am_filter_aaaa_la_OBJECTS = filter-aaaa.lo
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+ $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=link $(CCLD) \
+ $(AM_CFLAGS) $(CFLAGS) $(filter_aaaa_la_LDFLAGS) $(LDFLAGS) -o \
+ $@
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+am__maybe_remake_depfiles = depfiles
+am__depfiles_remade = ./$(DEPDIR)/filter-a.Plo \
+ ./$(DEPDIR)/filter-aaaa.Plo
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+ $(CPPFLAGS) $(AM_CFLAGS) $(CFLAGS)
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+ $(LIBTOOLFLAGS) --mode=compile $(CC) $(DEFS) \
+ $(DEFAULT_INCLUDES) $(INCLUDES) $(AM_CPPFLAGS) $(CPPFLAGS) \
+ $(AM_CFLAGS) $(CFLAGS)
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+ $(AM_LDFLAGS) $(LDFLAGS) -o $@
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+
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+ $(top_builddir)/lib/isccfg/libisccfg.la
+
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+
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+
+LIBBIND9_CFLAGS = \
+ -I$(top_srcdir)/lib/bind9/include
+
+LIBBIND9_LIBS = \
+ $(top_builddir)/lib/bind9/libbind9.la
+
+pkglib_LTLIBRARIES = filter-aaaa.la filter-a.la
+filter_aaaa_la_SOURCES = filter-aaaa.c
+filter_a_la_SOURCES = filter-a.c
+filter_aaaa_la_LDFLAGS = -avoid-version -module -shared -export-dynamic
+filter_a_la_LDFLAGS = -avoid-version -module -shared -export-dynamic
+all: all-am
+
+.SUFFIXES:
+.SUFFIXES: .c .lo .o .obj
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+ @for dep in $?; do \
+ case '$(am__configure_deps)' in \
+ *$$dep*) \
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+ && { if test -f $@; then exit 0; else break; fi; }; \
+ exit 1;; \
+ esac; \
+ done; \
+ echo ' cd $(top_srcdir) && $(AUTOMAKE) --foreign bin/plugins/Makefile'; \
+ $(am__cd) $(top_srcdir) && \
+ $(AUTOMAKE) --foreign bin/plugins/Makefile
+Makefile: $(srcdir)/Makefile.in $(top_builddir)/config.status
+ @case '$?' in \
+ *config.status*) \
+ cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh;; \
+ *) \
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+
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+ cd $(top_builddir) && $(MAKE) $(AM_MAKEFLAGS) am--refresh
+$(am__aclocal_m4_deps):
+
+install-pkglibLTLIBRARIES: $(pkglib_LTLIBRARIES)
+ @$(NORMAL_INSTALL)
+ @list='$(pkglib_LTLIBRARIES)'; test -n "$(pkglibdir)" || list=; \
+ list2=; for p in $$list; do \
+ if test -f $$p; then \
+ list2="$$list2 $$p"; \
+ else :; fi; \
+ done; \
+ test -z "$$list2" || { \
+ echo " $(MKDIR_P) '$(DESTDIR)$(pkglibdir)'"; \
+ $(MKDIR_P) "$(DESTDIR)$(pkglibdir)" || exit 1; \
+ echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 '$(DESTDIR)$(pkglibdir)'"; \
+ $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=install $(INSTALL) $(INSTALL_STRIP_FLAG) $$list2 "$(DESTDIR)$(pkglibdir)"; \
+ }
+
+uninstall-pkglibLTLIBRARIES:
+ @$(NORMAL_UNINSTALL)
+ @list='$(pkglib_LTLIBRARIES)'; test -n "$(pkglibdir)" || list=; \
+ for p in $$list; do \
+ $(am__strip_dir) \
+ echo " $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f '$(DESTDIR)$(pkglibdir)/$$f'"; \
+ $(LIBTOOL) $(AM_LIBTOOLFLAGS) $(LIBTOOLFLAGS) --mode=uninstall rm -f "$(DESTDIR)$(pkglibdir)/$$f"; \
+ done
+
+clean-pkglibLTLIBRARIES:
+ -test -z "$(pkglib_LTLIBRARIES)" || rm -f $(pkglib_LTLIBRARIES)
+ @list='$(pkglib_LTLIBRARIES)'; \
+ locs=`for p in $$list; do echo $$p; done | \
+ sed 's|^[^/]*$$|.|; s|/[^/]*$$||; s|$$|/so_locations|' | \
+ sort -u`; \
+ test -z "$$locs" || { \
+ echo rm -f $${locs}; \
+ rm -f $${locs}; \
+ }
+
+filter-a.la: $(filter_a_la_OBJECTS) $(filter_a_la_DEPENDENCIES) $(EXTRA_filter_a_la_DEPENDENCIES)
+ $(AM_V_CCLD)$(filter_a_la_LINK) -rpath $(pkglibdir) $(filter_a_la_OBJECTS) $(filter_a_la_LIBADD) $(LIBS)
+
+filter-aaaa.la: $(filter_aaaa_la_OBJECTS) $(filter_aaaa_la_DEPENDENCIES) $(EXTRA_filter_aaaa_la_DEPENDENCIES)
+ $(AM_V_CCLD)$(filter_aaaa_la_LINK) -rpath $(pkglibdir) $(filter_aaaa_la_OBJECTS) $(filter_aaaa_la_LIBADD) $(LIBS)
+
+mostlyclean-compile:
+ -rm -f *.$(OBJEXT)
+
+distclean-compile:
+ -rm -f *.tab.c
+
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/filter-a.Plo@am__quote@ # am--include-marker
+@AMDEP_TRUE@@am__include@ @am__quote@./$(DEPDIR)/filter-aaaa.Plo@am__quote@ # am--include-marker
+
+$(am__depfiles_remade):
+ @$(MKDIR_P) $(@D)
+ @echo '# dummy' >$@-t && $(am__mv) $@-t $@
+
+am--depfiles: $(am__depfiles_remade)
+
+.c.o:
+@am__fastdepCC_TRUE@ $(AM_V_CC)depbase=`echo $@ | sed 's|[^/]*$$|$(DEPDIR)/&|;s|\.o$$||'`;\
+@am__fastdepCC_TRUE@ $(COMPILE) -MT $@ -MD -MP -MF $$depbase.Tpo -c -o $@ $< &&\
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+
+.c.obj:
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+
+.c.lo:
+@am__fastdepCC_TRUE@ $(AM_V_CC)depbase=`echo $@ | sed 's|[^/]*$$|$(DEPDIR)/&|;s|\.lo$$||'`;\
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+@am__fastdepCC_FALSE@ $(AM_V_CC@am__nodep@)$(LTCOMPILE) -c -o $@ $<
+
+mostlyclean-libtool:
+ -rm -f *.lo
+
+clean-libtool:
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+ID: $(am__tagged_files)
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+ $(ETAGS) $(ETAGSFLAGS) $(AM_ETAGSFLAGS) $(ETAGS_ARGS) \
+ "$$@" $$unique; \
+ else \
+ $(ETAGS) $(ETAGSFLAGS) $(AM_ETAGSFLAGS) $(ETAGS_ARGS) \
+ $$unique; \
+ fi; \
+ fi
+ctags: ctags-am
+
+CTAGS: ctags
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+GTAGS:
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+ esac; \
+ for i in $$list; do \
+ if test -f "$$i"; then \
+ echo "$(subdir)/$$i"; \
+ else \
+ echo "$$sdir/$$i"; \
+ fi; \
+ done >> $(top_builddir)/cscope.files
+
+distclean-tags:
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+distdir: $(BUILT_SOURCES)
+ $(MAKE) $(AM_MAKEFLAGS) distdir-am
+
+distdir-am: $(DISTFILES)
+ @srcdirstrip=`echo "$(srcdir)" | sed 's/[].[^$$\\*]/\\\\&/g'`; \
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+ list='$(DISTFILES)'; \
+ dist_files=`for file in $$list; do echo $$file; done | \
+ sed -e "s|^$$srcdirstrip/||;t" \
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+ sort -u` ;; \
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+ for file in $$dist_files; do \
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+ test -f "$(distdir)/$$file" \
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+ || exit 1; \
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+ done
+check-am: all-am
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+ test -z "$$dir" || $(MKDIR_P) "$$dir"; \
+ done
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+ $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+ install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+ install; \
+ else \
+ $(MAKE) $(AM_MAKEFLAGS) INSTALL_PROGRAM="$(INSTALL_STRIP_PROGRAM)" \
+ install_sh_PROGRAM="$(INSTALL_STRIP_PROGRAM)" INSTALL_STRIP_FLAG=-s \
+ "INSTALL_PROGRAM_ENV=STRIPPROG='$(STRIP)'" install; \
+ fi
+mostlyclean-generic:
+
+clean-generic:
+
+distclean-generic:
+ -test -z "$(CONFIG_CLEAN_FILES)" || rm -f $(CONFIG_CLEAN_FILES)
+ -test . = "$(srcdir)" || test -z "$(CONFIG_CLEAN_VPATH_FILES)" || rm -f $(CONFIG_CLEAN_VPATH_FILES)
+
+maintainer-clean-generic:
+ @echo "This command is intended for maintainers to use"
+ @echo "it deletes files that may require special tools to rebuild."
+clean: clean-am
+
+clean-am: clean-generic clean-libtool clean-pkglibLTLIBRARIES \
+ mostlyclean-am
+
+distclean: distclean-am
+ -rm -f ./$(DEPDIR)/filter-a.Plo
+ -rm -f ./$(DEPDIR)/filter-aaaa.Plo
+ -rm -f Makefile
+distclean-am: clean-am distclean-compile distclean-generic \
+ distclean-tags
+
+doc: doc-am
+
+doc-am: doc-local
+
+dvi: dvi-am
+
+dvi-am:
+
+html: html-am
+
+html-am:
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+ -rm -f ./$(DEPDIR)/filter-a.Plo
+ -rm -f ./$(DEPDIR)/filter-aaaa.Plo
+ -rm -f Makefile
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+ mostlyclean-libtool
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+
+test-am: test-local
+
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+
+unit: unit-am
+
+unit-am: unit-local
+
+.MAKE: install-am install-strip
+
+.PHONY: CTAGS GTAGS TAGS all all-am am--depfiles check check-am clean \
+ clean-generic clean-libtool clean-pkglibLTLIBRARIES \
+ cscopelist-am ctags ctags-am distclean distclean-compile \
+ distclean-generic distclean-libtool distclean-tags distdir \
+ doc-am doc-local dvi dvi-am html html-am info info-am install \
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+ install-html-am install-info install-info-am install-man \
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+ tags tags-am test-am test-local uninstall uninstall-am \
+ uninstall-pkglibLTLIBRARIES unit-am unit-local
+
+.PRECIOUS: Makefile
+
+
+# Tell versions [3.59,3.63) of GNU make to not export all variables.
+# Otherwise a system limit (for SysV at least) may be exceeded.
+.NOEXPORT:
diff --git a/bin/plugins/filter-a.c b/bin/plugins/filter-a.c
new file mode 100644
index 0000000..8556cb7
--- /dev/null
+++ b/bin/plugins/filter-a.c
@@ -0,0 +1,879 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file */
+
+/* aliases for the exported symbols */
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <isc/buffer.h>
+#include <isc/hash.h>
+#include <isc/ht.h>
+#include <isc/log.h>
+#include <isc/mem.h>
+#include <isc/netaddr.h>
+#include <isc/result.h>
+#include <isc/types.h>
+#include <isc/util.h>
+
+#include <dns/acl.h>
+#include <dns/db.h>
+#include <dns/enumtype.h>
+#include <dns/log.h>
+#include <dns/message.h>
+#include <dns/rdataset.h>
+#include <dns/types.h>
+#include <dns/view.h>
+
+#include <isccfg/aclconf.h>
+#include <isccfg/cfg.h>
+#include <isccfg/grammar.h>
+
+#include <ns/client.h>
+#include <ns/hooks.h>
+#include <ns/log.h>
+#include <ns/query.h>
+#include <ns/types.h>
+
+#define CHECK(op) \
+ do { \
+ result = (op); \
+ if (result != ISC_R_SUCCESS) { \
+ goto cleanup; \
+ } \
+ } while (0)
+
+/*
+ * Possible values for the settings of filter-a-on-v6 and
+ * filter-a-on-v4: "no" is NONE, "yes" is FILTER, "break-dnssec"
+ * is BREAK_DNSSEC.
+ */
+typedef enum { NONE = 0, FILTER = 1, BREAK_DNSSEC = 2 } filter_a_t;
+
+/*
+ * Persistent data for use by this module. This will be associated
+ * with client object address in the hash table, and will remain
+ * accessible until the client object is detached.
+ */
+typedef struct filter_data {
+ filter_a_t mode;
+ uint32_t flags;
+} filter_data_t;
+
+typedef struct filter_instance {
+ ns_plugin_t *module;
+ isc_mem_t *mctx;
+
+ /*
+ * Hash table associating a client object with its persistent data.
+ */
+ isc_ht_t *ht;
+ isc_mutex_t hlock;
+
+ /*
+ * Values configured when the module is loaded.
+ */
+ filter_a_t v4_a;
+ filter_a_t v6_a;
+ dns_acl_t *a_acl;
+} filter_instance_t;
+
+/*
+ * Per-client flags set by this module
+ */
+#define FILTER_A_RECURSING 0x0001 /* Recursing for AAAA */
+#define FILTER_A_FILTERED 0x0002 /* A was removed from answer */
+
+/*
+ * Client attribute tests.
+ */
+#define WANTDNSSEC(c) (((c)->attributes & NS_CLIENTATTR_WANTDNSSEC) != 0)
+#define RECURSIONOK(c) (((c)->query.attributes & NS_QUERYATTR_RECURSIONOK) != 0)
+
+/*
+ * Forward declarations of functions referenced in install_hooks().
+ */
+static ns_hookresult_t
+filter_qctx_initialize(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_respond_begin(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_respond_any_found(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_prep_response_begin(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_query_done_send(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_qctx_destroy(void *arg, void *cbdata, isc_result_t *resp);
+
+/*%
+ * Register the functions to be called at each hook point in 'hooktable', using
+ * memory context 'mctx' for allocating copies of stack-allocated structures
+ * passed to ns_hook_add(). Make sure 'inst' will be passed as the 'cbdata'
+ * argument to every callback.
+ */
+static void
+install_hooks(ns_hooktable_t *hooktable, isc_mem_t *mctx,
+ filter_instance_t *inst) {
+ const ns_hook_t filter_init = {
+ .action = filter_qctx_initialize,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_respbegin = {
+ .action = filter_respond_begin,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_respanyfound = {
+ .action = filter_respond_any_found,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_prepresp = {
+ .action = filter_prep_response_begin,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_donesend = {
+ .action = filter_query_done_send,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_destroy = {
+ .action = filter_qctx_destroy,
+ .action_data = inst,
+ };
+
+ ns_hook_add(hooktable, mctx, NS_QUERY_QCTX_INITIALIZED, &filter_init);
+ ns_hook_add(hooktable, mctx, NS_QUERY_RESPOND_BEGIN, &filter_respbegin);
+ ns_hook_add(hooktable, mctx, NS_QUERY_RESPOND_ANY_FOUND,
+ &filter_respanyfound);
+ ns_hook_add(hooktable, mctx, NS_QUERY_PREP_RESPONSE_BEGIN,
+ &filter_prepresp);
+ ns_hook_add(hooktable, mctx, NS_QUERY_DONE_SEND, &filter_donesend);
+ ns_hook_add(hooktable, mctx, NS_QUERY_QCTX_DESTROYED, &filter_destroy);
+}
+
+/**
+** Support for parsing of parameters and configuration of the module.
+**/
+
+/*
+ * Support for parsing of parameters.
+ */
+static const char *filter_a_enums[] = { "break-dnssec", NULL };
+
+static isc_result_t
+parse_filter_a(cfg_parser_t *pctx, const cfg_type_t *type, cfg_obj_t **ret) {
+ return (cfg_parse_enum_or_other(pctx, type, &cfg_type_boolean, ret));
+}
+
+static void
+doc_filter_a(cfg_printer_t *pctx, const cfg_type_t *type) {
+ cfg_doc_enum_or_other(pctx, type, &cfg_type_boolean);
+}
+
+static cfg_type_t cfg_type_filter_a = {
+ "filter_a", parse_filter_a, cfg_print_ustring,
+ doc_filter_a, &cfg_rep_string, filter_a_enums,
+};
+
+static cfg_clausedef_t param_clauses[] = {
+ { "filter-a", &cfg_type_bracketed_aml, 0 },
+ { "filter-a-on-v6", &cfg_type_filter_a, 0 },
+ { "filter-a-on-v4", &cfg_type_filter_a, 0 },
+};
+
+static cfg_clausedef_t *param_clausesets[] = { param_clauses, NULL };
+
+static cfg_type_t cfg_type_parameters = { "filter-a-params", cfg_parse_mapbody,
+ cfg_print_mapbody, cfg_doc_mapbody,
+ &cfg_rep_map, param_clausesets };
+
+static isc_result_t
+parse_filter_a_on(const cfg_obj_t *param_obj, const char *param_name,
+ filter_a_t *dstp) {
+ const cfg_obj_t *obj = NULL;
+ isc_result_t result;
+
+ result = cfg_map_get(param_obj, param_name, &obj);
+ if (result != ISC_R_SUCCESS) {
+ return (ISC_R_SUCCESS);
+ }
+
+ if (cfg_obj_isboolean(obj)) {
+ if (cfg_obj_asboolean(obj)) {
+ *dstp = FILTER;
+ } else {
+ *dstp = NONE;
+ }
+ } else if (strcasecmp(cfg_obj_asstring(obj), "break-dnssec") == 0) {
+ *dstp = BREAK_DNSSEC;
+ } else {
+ result = ISC_R_UNEXPECTED;
+ }
+
+ return (result);
+}
+
+static isc_result_t
+check_syntax(cfg_obj_t *fmap, const void *cfg, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ const cfg_obj_t *aclobj = NULL;
+ dns_acl_t *acl = NULL;
+ filter_a_t f4 = NONE, f6 = NONE;
+
+ cfg_map_get(fmap, "filter-a", &aclobj);
+ if (aclobj == NULL) {
+ return (result);
+ }
+
+ CHECK(cfg_acl_fromconfig(aclobj, (const cfg_obj_t *)cfg, lctx,
+ (cfg_aclconfctx_t *)actx, mctx, 0, &acl));
+
+ CHECK(parse_filter_a_on(fmap, "filter-a-on-v6", &f6));
+ CHECK(parse_filter_a_on(fmap, "filter-a-on-v4", &f4));
+
+ if ((f4 != NONE || f6 != NONE) && dns_acl_isnone(acl)) {
+ cfg_obj_log(aclobj, lctx, ISC_LOG_WARNING,
+ "\"filter-a\" is 'none;' but "
+ "either filter-a-on-v6 or filter-a-on-v4 "
+ "is enabled");
+ result = ISC_R_FAILURE;
+ } else if (f4 == NONE && f6 == NONE && !dns_acl_isnone(acl)) {
+ cfg_obj_log(aclobj, lctx, ISC_LOG_WARNING,
+ "\"filter-a\" is set but "
+ "neither filter-a-on-v6 or filter-a-on-v4 "
+ "is enabled");
+ result = ISC_R_FAILURE;
+ }
+
+cleanup:
+ if (acl != NULL) {
+ dns_acl_detach(&acl);
+ }
+
+ return (result);
+}
+
+static isc_result_t
+parse_parameters(filter_instance_t *inst, const char *parameters,
+ const void *cfg, const char *cfg_file, unsigned long cfg_line,
+ isc_mem_t *mctx, isc_log_t *lctx, void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ cfg_parser_t *parser = NULL;
+ cfg_obj_t *param_obj = NULL;
+ const cfg_obj_t *obj = NULL;
+ isc_buffer_t b;
+
+ CHECK(cfg_parser_create(mctx, lctx, &parser));
+
+ isc_buffer_constinit(&b, parameters, strlen(parameters));
+ isc_buffer_add(&b, strlen(parameters));
+ CHECK(cfg_parse_buffer(parser, &b, cfg_file, cfg_line,
+ &cfg_type_parameters, 0, &param_obj));
+
+ CHECK(check_syntax(param_obj, cfg, mctx, lctx, actx));
+
+ CHECK(parse_filter_a_on(param_obj, "filter-a-on-v6", &inst->v6_a));
+ CHECK(parse_filter_a_on(param_obj, "filter-a-on-v4", &inst->v4_a));
+
+ result = cfg_map_get(param_obj, "filter-a", &obj);
+ if (result == ISC_R_SUCCESS) {
+ CHECK(cfg_acl_fromconfig(obj, (const cfg_obj_t *)cfg, lctx,
+ (cfg_aclconfctx_t *)actx, mctx, 0,
+ &inst->a_acl));
+ } else {
+ CHECK(dns_acl_any(mctx, &inst->a_acl));
+ }
+
+cleanup:
+ if (param_obj != NULL) {
+ cfg_obj_destroy(parser, &param_obj);
+ }
+ if (parser != NULL) {
+ cfg_parser_destroy(&parser);
+ }
+ return (result);
+}
+
+/**
+** Mandatory plugin API functions:
+**
+** - plugin_destroy
+** - plugin_register
+** - plugin_version
+** - plugin_check
+**/
+
+/*
+ * Called by ns_plugin_register() to initialize the plugin and
+ * register hook functions into the view hook table.
+ */
+isc_result_t
+plugin_register(const char *parameters, const void *cfg, const char *cfg_file,
+ unsigned long cfg_line, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx, ns_hooktable_t *hooktable, void **instp) {
+ filter_instance_t *inst = NULL;
+ isc_result_t result = ISC_R_SUCCESS;
+
+ isc_log_write(lctx, NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_HOOKS,
+ ISC_LOG_INFO,
+ "registering 'filter-a' "
+ "module from %s:%lu, %s parameters",
+ cfg_file, cfg_line, parameters != NULL ? "with" : "no");
+
+ inst = isc_mem_get(mctx, sizeof(*inst));
+ memset(inst, 0, sizeof(*inst));
+ isc_mem_attach(mctx, &inst->mctx);
+
+ if (parameters != NULL) {
+ CHECK(parse_parameters(inst, parameters, cfg, cfg_file,
+ cfg_line, mctx, lctx, actx));
+ }
+
+ isc_ht_init(&inst->ht, mctx, 16, ISC_HT_CASE_SENSITIVE);
+ isc_mutex_init(&inst->hlock);
+
+ /*
+ * Set hook points in the view's hooktable.
+ */
+ install_hooks(hooktable, mctx, inst);
+
+ *instp = inst;
+
+cleanup:
+ if (result != ISC_R_SUCCESS) {
+ plugin_destroy((void **)&inst);
+ }
+
+ return (result);
+}
+
+isc_result_t
+plugin_check(const char *parameters, const void *cfg, const char *cfg_file,
+ unsigned long cfg_line, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ cfg_parser_t *parser = NULL;
+ cfg_obj_t *param_obj = NULL;
+ isc_buffer_t b;
+
+ CHECK(cfg_parser_create(mctx, lctx, &parser));
+
+ isc_buffer_constinit(&b, parameters, strlen(parameters));
+ isc_buffer_add(&b, strlen(parameters));
+ CHECK(cfg_parse_buffer(parser, &b, cfg_file, cfg_line,
+ &cfg_type_parameters, 0, &param_obj));
+
+ CHECK(check_syntax(param_obj, cfg, mctx, lctx, actx));
+
+cleanup:
+ if (param_obj != NULL) {
+ cfg_obj_destroy(parser, &param_obj);
+ }
+ if (parser != NULL) {
+ cfg_parser_destroy(&parser);
+ }
+ return (result);
+}
+
+/*
+ * Called by ns_plugins_free(); frees memory allocated by
+ * the module when it was registered.
+ */
+void
+plugin_destroy(void **instp) {
+ filter_instance_t *inst = (filter_instance_t *)*instp;
+
+ if (inst->ht != NULL) {
+ isc_ht_destroy(&inst->ht);
+ isc_mutex_destroy(&inst->hlock);
+ }
+ if (inst->a_acl != NULL) {
+ dns_acl_detach(&inst->a_acl);
+ }
+
+ isc_mem_putanddetach(&inst->mctx, inst, sizeof(*inst));
+ *instp = NULL;
+
+ return;
+}
+
+/*
+ * Returns plugin API version for compatibility checks.
+ */
+int
+plugin_version(void) {
+ return (NS_PLUGIN_VERSION);
+}
+
+/**
+** "filter-a" feature implementation begins here.
+**/
+
+/*%
+ * Structure describing the filtering to be applied by process_section().
+ */
+typedef struct section_filter {
+ query_ctx_t *qctx;
+ filter_a_t mode;
+ dns_section_t section;
+ const dns_name_t *name;
+ dns_rdatatype_t type;
+ bool only_if_aaaa_exists;
+} section_filter_t;
+
+/*
+ * Check whether this is an IPv4 client.
+ */
+static bool
+is_v4_client(ns_client_t *client) {
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET) {
+ return (true);
+ }
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET6 &&
+ IN6_IS_ADDR_V4MAPPED(&client->peeraddr.type.sin6.sin6_addr))
+ {
+ return (true);
+ }
+ return (false);
+}
+
+/*
+ * Check whether this is an IPv6 client.
+ */
+static bool
+is_v6_client(ns_client_t *client) {
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET6 &&
+ !IN6_IS_ADDR_V4MAPPED(&client->peeraddr.type.sin6.sin6_addr))
+ {
+ return (true);
+ }
+ return (false);
+}
+
+static filter_data_t *
+client_state_get(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state = NULL;
+ isc_result_t result;
+
+ LOCK(&inst->hlock);
+ result = isc_ht_find(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client), (void **)&client_state);
+ UNLOCK(&inst->hlock);
+
+ return (result == ISC_R_SUCCESS ? client_state : NULL);
+}
+
+static void
+client_state_create(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state;
+ isc_result_t result;
+
+ client_state = isc_mem_get(inst->mctx, sizeof(*client_state));
+
+ client_state->mode = NONE;
+ client_state->flags = 0;
+
+ LOCK(&inst->hlock);
+ result = isc_ht_add(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client), client_state);
+ UNLOCK(&inst->hlock);
+ RUNTIME_CHECK(result == ISC_R_SUCCESS);
+}
+
+static void
+client_state_destroy(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result;
+
+ if (client_state == NULL) {
+ return;
+ }
+
+ LOCK(&inst->hlock);
+ result = isc_ht_delete(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client));
+ UNLOCK(&inst->hlock);
+ RUNTIME_CHECK(result == ISC_R_SUCCESS);
+
+ isc_mem_put(inst->mctx, client_state, sizeof(*client_state));
+}
+
+/*%
+ * Mark 'rdataset' and 'sigrdataset' as rendered, gracefully handling NULL
+ * pointers and non-associated rdatasets.
+ */
+static void
+mark_as_rendered(dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset) {
+ if (rdataset != NULL && dns_rdataset_isassociated(rdataset)) {
+ rdataset->attributes |= DNS_RDATASETATTR_RENDERED;
+ }
+ if (sigrdataset != NULL && dns_rdataset_isassociated(sigrdataset)) {
+ sigrdataset->attributes |= DNS_RDATASETATTR_RENDERED;
+ }
+}
+
+/*%
+ * Check whether an RRset of given 'type' is present at given 'name'. If
+ * it is found and either it is not signed or the combination of query
+ * flags and configured processing 'mode' allows it, mark the RRset and its
+ * associated signatures as already rendered to prevent them from appearing
+ * in the response message stored in 'qctx'. If 'only_if_aaaa_exists' is
+ * true, an RRset of type AAAA must also exist at 'name' in order for the
+ * above processing to happen.
+ */
+static bool
+process_name(query_ctx_t *qctx, filter_a_t mode, const dns_name_t *name,
+ dns_rdatatype_t type, bool only_if_aaaa_exists) {
+ dns_rdataset_t *rdataset = NULL, *sigrdataset = NULL;
+ isc_result_t result;
+ bool modified = false;
+
+ if (only_if_aaaa_exists) {
+ CHECK(dns_message_findtype(name, dns_rdatatype_aaaa, 0, NULL));
+ }
+
+ (void)dns_message_findtype(name, type, 0, &rdataset);
+ (void)dns_message_findtype(name, dns_rdatatype_rrsig, type,
+ &sigrdataset);
+
+ if (rdataset != NULL &&
+ (sigrdataset == NULL || !WANTDNSSEC(qctx->client) ||
+ mode == BREAK_DNSSEC))
+ {
+ /*
+ * An RRset of given 'type' was found at 'name' and at least
+ * one of the following is true:
+ *
+ * - the RRset is not signed,
+ * - the client did not set the DO bit in its request,
+ * - configuration allows us to tamper with signed responses.
+ *
+ * This means it is okay to filter out this RRset and its
+ * signatures, if any, from the response.
+ */
+ mark_as_rendered(rdataset, sigrdataset);
+ modified = true;
+ }
+
+cleanup:
+ return (modified);
+}
+
+/*%
+ * Apply the requested section filter, i.e. prevent (when possible, as
+ * determined by process_name()) RRsets of given 'type' from being rendered
+ * in the given 'section' of the response message stored in 'qctx'. Clear
+ * the AD bit if the answer and/or authority section was modified. If
+ * 'name' is NULL, all names in the given 'section' are processed;
+ * otherwise, only 'name' is. 'only_if_aaaa_exists' is passed through to
+ * process_name().
+ */
+static void
+process_section(const section_filter_t *filter) {
+ query_ctx_t *qctx = filter->qctx;
+ filter_a_t mode = filter->mode;
+ dns_section_t section = filter->section;
+ const dns_name_t *name = filter->name;
+ dns_rdatatype_t type = filter->type;
+ bool only_if_aaaa_exists = filter->only_if_aaaa_exists;
+
+ dns_message_t *message = qctx->client->message;
+ isc_result_t result;
+
+ for (result = dns_message_firstname(message, section);
+ result == ISC_R_SUCCESS;
+ result = dns_message_nextname(message, section))
+ {
+ dns_name_t *cur = NULL;
+ dns_message_currentname(message, section, &cur);
+ if (name != NULL && !dns_name_equal(name, cur)) {
+ /*
+ * We only want to process 'name' and this is not it.
+ */
+ continue;
+ }
+
+ if (!process_name(qctx, mode, cur, type, only_if_aaaa_exists)) {
+ /*
+ * Response was not modified, do not touch the AD bit.
+ */
+ continue;
+ }
+
+ if (section == DNS_SECTION_ANSWER ||
+ section == DNS_SECTION_AUTHORITY)
+ {
+ message->flags &= ~DNS_MESSAGEFLAG_AD;
+ }
+ }
+}
+
+/*
+ * Initialize filter state, fetching it from a memory pool and storing it
+ * in a hash table keyed according to the client object; this enables us to
+ * retrieve persistent data related to a client query for as long as the
+ * object persists.
+ */
+static ns_hookresult_t
+filter_qctx_initialize(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state;
+
+ *resp = ISC_R_UNSET;
+
+ client_state = client_state_get(qctx, inst);
+ if (client_state == NULL) {
+ client_state_create(qctx, inst);
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Determine whether this client should have A filtered or not, based on
+ * the client address family and the settings of filter-a-on-v6 and
+ * filter-a-on-v4.
+ */
+static ns_hookresult_t
+filter_prep_response_begin(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result;
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state == NULL) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (inst->v4_a != NONE || inst->v6_a != NONE) {
+ result = ns_client_checkaclsilent(qctx->client, NULL,
+ inst->a_acl, true);
+ if (result == ISC_R_SUCCESS && inst->v4_a != NONE &&
+ is_v4_client(qctx->client))
+ {
+ client_state->mode = inst->v4_a;
+ } else if (result == ISC_R_SUCCESS && inst->v6_a != NONE &&
+ is_v6_client(qctx->client))
+ {
+ client_state->mode = inst->v6_a;
+ }
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Hide A rrsets if there is a matching AAAA. Trigger recursion if
+ * necessary to find out whether an AAAA exists.
+ *
+ * (This version is for processing answers to explicit A queries; ANY
+ * queries are handled in filter_respond_any_found().)
+ */
+static ns_hookresult_t
+filter_respond_begin(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result = ISC_R_UNSET;
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state == NULL) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (client_state->mode != BREAK_DNSSEC &&
+ (client_state->mode != FILTER ||
+ (WANTDNSSEC(qctx->client) && qctx->sigrdataset != NULL &&
+ dns_rdataset_isassociated(qctx->sigrdataset))))
+ {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (qctx->qtype == dns_rdatatype_a) {
+ dns_rdataset_t *trdataset;
+ trdataset = ns_client_newrdataset(qctx->client);
+ result = dns_db_findrdataset(
+ qctx->db, qctx->node, qctx->version, dns_rdatatype_aaaa,
+ 0, qctx->client->now, trdataset, NULL);
+ if (dns_rdataset_isassociated(trdataset)) {
+ dns_rdataset_disassociate(trdataset);
+ }
+ ns_client_putrdataset(qctx->client, &trdataset);
+
+ /*
+ * We found an A. If we also found an AAAA, then the A
+ * must not be rendered.
+ *
+ * If the AAAA is not in our cache, then any result other than
+ * DNS_R_DELEGATION or ISC_R_NOTFOUND means there is no AAAAA,
+ * and so AAAAs are okay.
+ *
+ * We assume there is no AAAA if we can't recurse for this
+ * client. That might be the wrong answer, but what else
+ * can we do? Besides, the fact that we have the A and
+ * are using this mechanism in the first place suggests
+ * that we care more about AAAAs than As, and would have
+ * cached an AAAA if it existed.
+ */
+ if (result == ISC_R_SUCCESS) {
+ mark_as_rendered(qctx->rdataset, qctx->sigrdataset);
+ qctx->client->message->flags &= ~DNS_MESSAGEFLAG_AD;
+ client_state->flags |= FILTER_A_FILTERED;
+ } else if (!qctx->authoritative && RECURSIONOK(qctx->client) &&
+ (result == DNS_R_DELEGATION ||
+ result == ISC_R_NOTFOUND))
+ {
+ /*
+ * This is an ugly kludge to recurse
+ * for the AAAA and discard the result.???
+ *
+ * Continue to add the A now.
+ * We'll make a note to not render it
+ * if the recursion for the AAAA succeeds.
+ */
+ result = ns_query_recurse(qctx->client,
+ dns_rdatatype_aaaa,
+ qctx->client->query.qname,
+ NULL, NULL, qctx->resuming);
+ if (result == ISC_R_SUCCESS) {
+ client_state->flags |= FILTER_A_RECURSING;
+ qctx->client->query.attributes |=
+ NS_QUERYATTR_RECURSING;
+ }
+ }
+ } else if (qctx->qtype == dns_rdatatype_aaaa &&
+ (client_state->flags & FILTER_A_RECURSING) != 0)
+ {
+ const section_filter_t filter_answer = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ANSWER,
+ .name = qctx->fname,
+ .type = dns_rdatatype_a,
+ };
+ process_section(&filter_answer);
+
+ client_state->flags &= ~FILTER_A_RECURSING;
+
+ result = ns_query_done(qctx);
+
+ *resp = result;
+
+ return (NS_HOOK_RETURN);
+ }
+
+ *resp = result;
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * When answering an ANY query, remove A if AAAA is present.
+ */
+static ns_hookresult_t
+filter_respond_any_found(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state != NULL && client_state->mode != NONE) {
+ /*
+ * If we are authoritative, require an AAAA record to be
+ * present before filtering out A records; otherwise,
+ * just assume an AAAA record exists even if it was not in the
+ * cache (and therefore is not in the response message),
+ * thus proceeding with filtering out A records.
+ */
+ const section_filter_t filter_answer = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ANSWER,
+ .name = qctx->tname,
+ .type = dns_rdatatype_a,
+ .only_if_aaaa_exists = qctx->authoritative,
+ };
+ process_section(&filter_answer);
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Hide A rrsets in the additional section if there is a matching AAAA, and
+ * hide NS in the authority section if A was filtered in the answer
+ * section.
+ */
+static ns_hookresult_t
+filter_query_done_send(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state != NULL && client_state->mode != NONE) {
+ const section_filter_t filter_additional = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ADDITIONAL,
+ .type = dns_rdatatype_a,
+ .only_if_aaaa_exists = true,
+ };
+ process_section(&filter_additional);
+
+ if ((client_state->flags & FILTER_A_FILTERED) != 0) {
+ const section_filter_t filter_authority = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_AUTHORITY,
+ .type = dns_rdatatype_ns,
+ };
+ process_section(&filter_authority);
+ }
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * If the client is being detached, then we can delete our persistent data
+ * from hash table and return it to the memory pool.
+ */
+static ns_hookresult_t
+filter_qctx_destroy(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+
+ *resp = ISC_R_UNSET;
+
+ if (!qctx->detach_client) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ client_state_destroy(qctx, inst);
+
+ return (NS_HOOK_CONTINUE);
+}
diff --git a/bin/plugins/filter-a.rst b/bin/plugins/filter-a.rst
new file mode 100644
index 0000000..16b3dee
--- /dev/null
+++ b/bin/plugins/filter-a.rst
@@ -0,0 +1,86 @@
+.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+..
+.. SPDX-License-Identifier: MPL-2.0
+..
+.. This Source Code Form is subject to the terms of the Mozilla Public
+.. License, v. 2.0. If a copy of the MPL was not distributed with this
+.. file, you can obtain one at https://mozilla.org/MPL/2.0/.
+..
+.. See the COPYRIGHT file distributed with this work for additional
+.. information regarding copyright ownership.
+
+.. highlight: console
+
+.. iscman:: filter-a
+.. _man_filter-a:
+
+filter-a.so - filter A in DNS responses when AAAA is present
+---------------------------------------------------------------
+
+Synopsis
+~~~~~~~~
+
+:program:`plugin query` "filter-a.so" [{ parameters }];
+
+Description
+~~~~~~~~~~~
+
+:program:`filter-a.so` is a query plugin module for :iscman:`named`, enabling
+:iscman:`named` to omit some IPv4 addresses when responding to clients.
+
+For example:
+
+::
+
+ plugin query "filter-a.so" {
+ filter-a-on-v6 yes;
+ filter-a-on-v4 yes;
+ filter-a { 192.0.2.1; 2001:db8:2::1; };
+ };
+
+This module is intended to aid transition from IPv4 to IPv6 by
+withholding IPv4 addresses from DNS clients which are not connected to
+the IPv4 Internet, when the name being looked up has an IPv6 address
+available. Use of this module is not recommended unless absolutely
+necessary.
+
+Note: This mechanism can erroneously cause other servers not to give
+A records to their clients. If a recursing server with both IPv6 and
+IPv4 network connections queries an authoritative server using this
+mechanism via IPv6, it is denied A records even if its client is
+using IPv4.
+
+Options
+~~~~~~~
+
+``filter-a``
+ This option specifies a list of client addresses for which A filtering is to
+ be applied. The default is ``any``.
+
+``filter-a-on-v6``
+ If set to ``yes``, this option indicates that the DNS client is at an IPv6 address, in
+ ``filter-a``. If the response does not include DNSSEC
+ signatures, then all A records are deleted from the response. This
+ filtering applies to all responses, not only authoritative
+ ones.
+
+ If set to ``break-dnssec``, then A records are deleted even when
+ DNSSEC is enabled. As suggested by the name, this causes the response
+ to fail to verify, because the DNSSEC protocol is designed to detect
+ deletions.
+
+ This mechanism can erroneously cause other servers not to give A
+ records to their clients. If a recursing server with both IPv6 and IPv4
+ network connections queries an authoritative server using this
+ mechanism via IPv6, it is denied A records even if its client is
+ using IPv4.
+
+``filter-a-on-v4``
+ This option is identical to ``filter-a-on-v6``, except that it filters A responses
+ to queries from IPv4 clients instead of IPv6 clients. To filter all
+ responses, set both options to ``yes``.
+
+See Also
+~~~~~~~~
+
+BIND 9 Administrator Reference Manual.
diff --git a/bin/plugins/filter-aaaa.c b/bin/plugins/filter-aaaa.c
new file mode 100644
index 0000000..1ec1fd8
--- /dev/null
+++ b/bin/plugins/filter-aaaa.c
@@ -0,0 +1,881 @@
+/*
+ * Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+ *
+ * SPDX-License-Identifier: MPL-2.0
+ *
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, you can obtain one at https://mozilla.org/MPL/2.0/.
+ *
+ * See the COPYRIGHT file distributed with this work for additional
+ * information regarding copyright ownership.
+ */
+
+/*! \file */
+
+/* aliases for the exported symbols */
+
+#include <inttypes.h>
+#include <stdbool.h>
+#include <string.h>
+
+#include <isc/buffer.h>
+#include <isc/hash.h>
+#include <isc/ht.h>
+#include <isc/log.h>
+#include <isc/mem.h>
+#include <isc/netaddr.h>
+#include <isc/result.h>
+#include <isc/types.h>
+#include <isc/util.h>
+
+#include <dns/acl.h>
+#include <dns/db.h>
+#include <dns/enumtype.h>
+#include <dns/log.h>
+#include <dns/message.h>
+#include <dns/rdataset.h>
+#include <dns/types.h>
+#include <dns/view.h>
+
+#include <isccfg/aclconf.h>
+#include <isccfg/cfg.h>
+#include <isccfg/grammar.h>
+
+#include <ns/client.h>
+#include <ns/hooks.h>
+#include <ns/log.h>
+#include <ns/query.h>
+#include <ns/types.h>
+
+#define CHECK(op) \
+ do { \
+ result = (op); \
+ if (result != ISC_R_SUCCESS) { \
+ goto cleanup; \
+ } \
+ } while (0)
+
+/*
+ * Possible values for the settings of filter-aaaa-on-v4 and
+ * filter-aaaa-on-v6: "no" is NONE, "yes" is FILTER, "break-dnssec"
+ * is BREAK_DNSSEC.
+ */
+typedef enum { NONE = 0, FILTER = 1, BREAK_DNSSEC = 2 } filter_aaaa_t;
+
+/*
+ * Persistent data for use by this module. This will be associated
+ * with client object address in the hash table, and will remain
+ * accessible until the client object is detached.
+ */
+typedef struct filter_data {
+ filter_aaaa_t mode;
+ uint32_t flags;
+} filter_data_t;
+
+typedef struct filter_instance {
+ ns_plugin_t *module;
+ isc_mem_t *mctx;
+
+ /*
+ * Hash table associating a client object with its persistent data.
+ */
+ isc_ht_t *ht;
+ isc_mutex_t hlock;
+
+ /*
+ * Values configured when the module is loaded.
+ */
+ filter_aaaa_t v4_aaaa;
+ filter_aaaa_t v6_aaaa;
+ dns_acl_t *aaaa_acl;
+} filter_instance_t;
+
+/*
+ * Per-client flags set by this module
+ */
+#define FILTER_AAAA_RECURSING 0x0001 /* Recursing for A */
+#define FILTER_AAAA_FILTERED 0x0002 /* AAAA was removed from answer */
+
+/*
+ * Client attribute tests.
+ */
+#define WANTDNSSEC(c) (((c)->attributes & NS_CLIENTATTR_WANTDNSSEC) != 0)
+#define RECURSIONOK(c) (((c)->query.attributes & NS_QUERYATTR_RECURSIONOK) != 0)
+
+/*
+ * Forward declarations of functions referenced in install_hooks().
+ */
+static ns_hookresult_t
+filter_qctx_initialize(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_respond_begin(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_respond_any_found(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_prep_response_begin(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_query_done_send(void *arg, void *cbdata, isc_result_t *resp);
+static ns_hookresult_t
+filter_qctx_destroy(void *arg, void *cbdata, isc_result_t *resp);
+
+/*%
+ * Register the functions to be called at each hook point in 'hooktable', using
+ * memory context 'mctx' for allocating copies of stack-allocated structures
+ * passed to ns_hook_add(). Make sure 'inst' will be passed as the 'cbdata'
+ * argument to every callback.
+ */
+static void
+install_hooks(ns_hooktable_t *hooktable, isc_mem_t *mctx,
+ filter_instance_t *inst) {
+ const ns_hook_t filter_init = {
+ .action = filter_qctx_initialize,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_respbegin = {
+ .action = filter_respond_begin,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_respanyfound = {
+ .action = filter_respond_any_found,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_prepresp = {
+ .action = filter_prep_response_begin,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_donesend = {
+ .action = filter_query_done_send,
+ .action_data = inst,
+ };
+
+ const ns_hook_t filter_destroy = {
+ .action = filter_qctx_destroy,
+ .action_data = inst,
+ };
+
+ ns_hook_add(hooktable, mctx, NS_QUERY_QCTX_INITIALIZED, &filter_init);
+ ns_hook_add(hooktable, mctx, NS_QUERY_RESPOND_BEGIN, &filter_respbegin);
+ ns_hook_add(hooktable, mctx, NS_QUERY_RESPOND_ANY_FOUND,
+ &filter_respanyfound);
+ ns_hook_add(hooktable, mctx, NS_QUERY_PREP_RESPONSE_BEGIN,
+ &filter_prepresp);
+ ns_hook_add(hooktable, mctx, NS_QUERY_DONE_SEND, &filter_donesend);
+ ns_hook_add(hooktable, mctx, NS_QUERY_QCTX_DESTROYED, &filter_destroy);
+}
+
+/**
+** Support for parsing of parameters and configuration of the module.
+**/
+
+/*
+ * Support for parsing of parameters.
+ */
+static const char *filter_aaaa_enums[] = { "break-dnssec", NULL };
+
+static isc_result_t
+parse_filter_aaaa(cfg_parser_t *pctx, const cfg_type_t *type, cfg_obj_t **ret) {
+ return (cfg_parse_enum_or_other(pctx, type, &cfg_type_boolean, ret));
+}
+
+static void
+doc_filter_aaaa(cfg_printer_t *pctx, const cfg_type_t *type) {
+ cfg_doc_enum_or_other(pctx, type, &cfg_type_boolean);
+}
+
+static cfg_type_t cfg_type_filter_aaaa = {
+ "filter_aaaa", parse_filter_aaaa, cfg_print_ustring,
+ doc_filter_aaaa, &cfg_rep_string, filter_aaaa_enums,
+};
+
+static cfg_clausedef_t param_clauses[] = {
+ { "filter-aaaa", &cfg_type_bracketed_aml, 0 },
+ { "filter-aaaa-on-v4", &cfg_type_filter_aaaa, 0 },
+ { "filter-aaaa-on-v6", &cfg_type_filter_aaaa, 0 },
+};
+
+static cfg_clausedef_t *param_clausesets[] = { param_clauses, NULL };
+
+static cfg_type_t cfg_type_parameters = {
+ "filter-aaaa-params", cfg_parse_mapbody, cfg_print_mapbody,
+ cfg_doc_mapbody, &cfg_rep_map, param_clausesets
+};
+
+static isc_result_t
+parse_filter_aaaa_on(const cfg_obj_t *param_obj, const char *param_name,
+ filter_aaaa_t *dstp) {
+ const cfg_obj_t *obj = NULL;
+ isc_result_t result;
+
+ result = cfg_map_get(param_obj, param_name, &obj);
+ if (result != ISC_R_SUCCESS) {
+ return (ISC_R_SUCCESS);
+ }
+
+ if (cfg_obj_isboolean(obj)) {
+ if (cfg_obj_asboolean(obj)) {
+ *dstp = FILTER;
+ } else {
+ *dstp = NONE;
+ }
+ } else if (strcasecmp(cfg_obj_asstring(obj), "break-dnssec") == 0) {
+ *dstp = BREAK_DNSSEC;
+ } else {
+ result = ISC_R_UNEXPECTED;
+ }
+
+ return (result);
+}
+
+static isc_result_t
+check_syntax(cfg_obj_t *fmap, const void *cfg, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ const cfg_obj_t *aclobj = NULL;
+ dns_acl_t *acl = NULL;
+ filter_aaaa_t f4 = NONE, f6 = NONE;
+
+ cfg_map_get(fmap, "filter-aaaa", &aclobj);
+ if (aclobj == NULL) {
+ return (result);
+ }
+
+ CHECK(cfg_acl_fromconfig(aclobj, (const cfg_obj_t *)cfg, lctx,
+ (cfg_aclconfctx_t *)actx, mctx, 0, &acl));
+
+ CHECK(parse_filter_aaaa_on(fmap, "filter-aaaa-on-v4", &f4));
+ CHECK(parse_filter_aaaa_on(fmap, "filter-aaaa-on-v6", &f6));
+
+ if ((f4 != NONE || f6 != NONE) && dns_acl_isnone(acl)) {
+ cfg_obj_log(aclobj, lctx, ISC_LOG_WARNING,
+ "\"filter-aaaa\" is 'none;' but "
+ "either filter-aaaa-on-v4 or filter-aaaa-on-v6 "
+ "is enabled");
+ result = ISC_R_FAILURE;
+ } else if (f4 == NONE && f6 == NONE && !dns_acl_isnone(acl)) {
+ cfg_obj_log(aclobj, lctx, ISC_LOG_WARNING,
+ "\"filter-aaaa\" is set but "
+ "neither filter-aaaa-on-v4 or filter-aaaa-on-v6 "
+ "is enabled");
+ result = ISC_R_FAILURE;
+ }
+
+cleanup:
+ if (acl != NULL) {
+ dns_acl_detach(&acl);
+ }
+
+ return (result);
+}
+
+static isc_result_t
+parse_parameters(filter_instance_t *inst, const char *parameters,
+ const void *cfg, const char *cfg_file, unsigned long cfg_line,
+ isc_mem_t *mctx, isc_log_t *lctx, void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ cfg_parser_t *parser = NULL;
+ cfg_obj_t *param_obj = NULL;
+ const cfg_obj_t *obj = NULL;
+ isc_buffer_t b;
+
+ CHECK(cfg_parser_create(mctx, lctx, &parser));
+
+ isc_buffer_constinit(&b, parameters, strlen(parameters));
+ isc_buffer_add(&b, strlen(parameters));
+ CHECK(cfg_parse_buffer(parser, &b, cfg_file, cfg_line,
+ &cfg_type_parameters, 0, &param_obj));
+
+ CHECK(check_syntax(param_obj, cfg, mctx, lctx, actx));
+
+ CHECK(parse_filter_aaaa_on(param_obj, "filter-aaaa-on-v4",
+ &inst->v4_aaaa));
+ CHECK(parse_filter_aaaa_on(param_obj, "filter-aaaa-on-v6",
+ &inst->v6_aaaa));
+
+ result = cfg_map_get(param_obj, "filter-aaaa", &obj);
+ if (result == ISC_R_SUCCESS) {
+ CHECK(cfg_acl_fromconfig(obj, (const cfg_obj_t *)cfg, lctx,
+ (cfg_aclconfctx_t *)actx, mctx, 0,
+ &inst->aaaa_acl));
+ } else {
+ CHECK(dns_acl_any(mctx, &inst->aaaa_acl));
+ }
+
+cleanup:
+ if (param_obj != NULL) {
+ cfg_obj_destroy(parser, &param_obj);
+ }
+ if (parser != NULL) {
+ cfg_parser_destroy(&parser);
+ }
+ return (result);
+}
+
+/**
+** Mandatory plugin API functions:
+**
+** - plugin_destroy
+** - plugin_register
+** - plugin_version
+** - plugin_check
+**/
+
+/*
+ * Called by ns_plugin_register() to initialize the plugin and
+ * register hook functions into the view hook table.
+ */
+isc_result_t
+plugin_register(const char *parameters, const void *cfg, const char *cfg_file,
+ unsigned long cfg_line, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx, ns_hooktable_t *hooktable, void **instp) {
+ filter_instance_t *inst = NULL;
+ isc_result_t result = ISC_R_SUCCESS;
+
+ isc_log_write(lctx, NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_HOOKS,
+ ISC_LOG_INFO,
+ "registering 'filter-aaaa' "
+ "module from %s:%lu, %s parameters",
+ cfg_file, cfg_line, parameters != NULL ? "with" : "no");
+
+ inst = isc_mem_get(mctx, sizeof(*inst));
+ memset(inst, 0, sizeof(*inst));
+ isc_mem_attach(mctx, &inst->mctx);
+
+ if (parameters != NULL) {
+ CHECK(parse_parameters(inst, parameters, cfg, cfg_file,
+ cfg_line, mctx, lctx, actx));
+ }
+
+ isc_ht_init(&inst->ht, mctx, 16, ISC_HT_CASE_SENSITIVE);
+ isc_mutex_init(&inst->hlock);
+
+ /*
+ * Set hook points in the view's hooktable.
+ */
+ install_hooks(hooktable, mctx, inst);
+
+ *instp = inst;
+
+cleanup:
+ if (result != ISC_R_SUCCESS) {
+ plugin_destroy((void **)&inst);
+ }
+
+ return (result);
+}
+
+isc_result_t
+plugin_check(const char *parameters, const void *cfg, const char *cfg_file,
+ unsigned long cfg_line, isc_mem_t *mctx, isc_log_t *lctx,
+ void *actx) {
+ isc_result_t result = ISC_R_SUCCESS;
+ cfg_parser_t *parser = NULL;
+ cfg_obj_t *param_obj = NULL;
+ isc_buffer_t b;
+
+ CHECK(cfg_parser_create(mctx, lctx, &parser));
+
+ isc_buffer_constinit(&b, parameters, strlen(parameters));
+ isc_buffer_add(&b, strlen(parameters));
+ CHECK(cfg_parse_buffer(parser, &b, cfg_file, cfg_line,
+ &cfg_type_parameters, 0, &param_obj));
+
+ CHECK(check_syntax(param_obj, cfg, mctx, lctx, actx));
+
+cleanup:
+ if (param_obj != NULL) {
+ cfg_obj_destroy(parser, &param_obj);
+ }
+ if (parser != NULL) {
+ cfg_parser_destroy(&parser);
+ }
+ return (result);
+}
+
+/*
+ * Called by ns_plugins_free(); frees memory allocated by
+ * the module when it was registered.
+ */
+void
+plugin_destroy(void **instp) {
+ filter_instance_t *inst = (filter_instance_t *)*instp;
+
+ if (inst->ht != NULL) {
+ isc_ht_destroy(&inst->ht);
+ isc_mutex_destroy(&inst->hlock);
+ }
+ if (inst->aaaa_acl != NULL) {
+ dns_acl_detach(&inst->aaaa_acl);
+ }
+
+ isc_mem_putanddetach(&inst->mctx, inst, sizeof(*inst));
+ *instp = NULL;
+
+ return;
+}
+
+/*
+ * Returns plugin API version for compatibility checks.
+ */
+int
+plugin_version(void) {
+ return (NS_PLUGIN_VERSION);
+}
+
+/**
+** "filter-aaaa" feature implementation begins here.
+**/
+
+/*%
+ * Structure describing the filtering to be applied by process_section().
+ */
+typedef struct section_filter {
+ query_ctx_t *qctx;
+ filter_aaaa_t mode;
+ dns_section_t section;
+ const dns_name_t *name;
+ dns_rdatatype_t type;
+ bool only_if_a_exists;
+} section_filter_t;
+
+/*
+ * Check whether this is an IPv4 client.
+ */
+static bool
+is_v4_client(ns_client_t *client) {
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET) {
+ return (true);
+ }
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET6 &&
+ IN6_IS_ADDR_V4MAPPED(&client->peeraddr.type.sin6.sin6_addr))
+ {
+ return (true);
+ }
+ return (false);
+}
+
+/*
+ * Check whether this is an IPv6 client.
+ */
+static bool
+is_v6_client(ns_client_t *client) {
+ if (isc_sockaddr_pf(&client->peeraddr) == AF_INET6 &&
+ !IN6_IS_ADDR_V4MAPPED(&client->peeraddr.type.sin6.sin6_addr))
+ {
+ return (true);
+ }
+ return (false);
+}
+
+static filter_data_t *
+client_state_get(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state = NULL;
+ isc_result_t result;
+
+ LOCK(&inst->hlock);
+ result = isc_ht_find(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client), (void **)&client_state);
+ UNLOCK(&inst->hlock);
+
+ return (result == ISC_R_SUCCESS ? client_state : NULL);
+}
+
+static void
+client_state_create(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state;
+ isc_result_t result;
+
+ client_state = isc_mem_get(inst->mctx, sizeof(*client_state));
+
+ client_state->mode = NONE;
+ client_state->flags = 0;
+
+ LOCK(&inst->hlock);
+ result = isc_ht_add(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client), client_state);
+ UNLOCK(&inst->hlock);
+ RUNTIME_CHECK(result == ISC_R_SUCCESS);
+}
+
+static void
+client_state_destroy(const query_ctx_t *qctx, filter_instance_t *inst) {
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result;
+
+ if (client_state == NULL) {
+ return;
+ }
+
+ LOCK(&inst->hlock);
+ result = isc_ht_delete(inst->ht, (const unsigned char *)&qctx->client,
+ sizeof(qctx->client));
+ UNLOCK(&inst->hlock);
+ RUNTIME_CHECK(result == ISC_R_SUCCESS);
+
+ isc_mem_put(inst->mctx, client_state, sizeof(*client_state));
+}
+
+/*%
+ * Mark 'rdataset' and 'sigrdataset' as rendered, gracefully handling NULL
+ * pointers and non-associated rdatasets.
+ */
+static void
+mark_as_rendered(dns_rdataset_t *rdataset, dns_rdataset_t *sigrdataset) {
+ if (rdataset != NULL && dns_rdataset_isassociated(rdataset)) {
+ rdataset->attributes |= DNS_RDATASETATTR_RENDERED;
+ }
+ if (sigrdataset != NULL && dns_rdataset_isassociated(sigrdataset)) {
+ sigrdataset->attributes |= DNS_RDATASETATTR_RENDERED;
+ }
+}
+
+/*%
+ * Check whether an RRset of given 'type' is present at given 'name'. If
+ * it is found and either it is not signed or the combination of query
+ * flags and configured processing 'mode' allows it, mark the RRset and its
+ * associated signatures as already rendered to prevent them from appearing
+ * in the response message stored in 'qctx'. If 'only_if_a_exists' is
+ * true, an RRset of type A must also exist at 'name' in order for the
+ * above processing to happen.
+ */
+static bool
+process_name(query_ctx_t *qctx, filter_aaaa_t mode, const dns_name_t *name,
+ dns_rdatatype_t type, bool only_if_a_exists) {
+ dns_rdataset_t *rdataset = NULL, *sigrdataset = NULL;
+ isc_result_t result;
+ bool modified = false;
+
+ if (only_if_a_exists) {
+ CHECK(dns_message_findtype(name, dns_rdatatype_a, 0, NULL));
+ }
+
+ (void)dns_message_findtype(name, type, 0, &rdataset);
+ (void)dns_message_findtype(name, dns_rdatatype_rrsig, type,
+ &sigrdataset);
+
+ if (rdataset != NULL &&
+ (sigrdataset == NULL || !WANTDNSSEC(qctx->client) ||
+ mode == BREAK_DNSSEC))
+ {
+ /*
+ * An RRset of given 'type' was found at 'name' and at least
+ * one of the following is true:
+ *
+ * - the RRset is not signed,
+ * - the client did not set the DO bit in its request,
+ * - configuration allows us to tamper with signed responses.
+ *
+ * This means it is okay to filter out this RRset and its
+ * signatures, if any, from the response.
+ */
+ mark_as_rendered(rdataset, sigrdataset);
+ modified = true;
+ }
+
+cleanup:
+ return (modified);
+}
+
+/*%
+ * Apply the requested section filter, i.e. prevent (when possible, as
+ * determined by process_name()) RRsets of given 'type' from being rendered
+ * in the given 'section' of the response message stored in 'qctx'. Clear
+ * the AD bit if the answer and/or authority section was modified. If
+ * 'name' is NULL, all names in the given 'section' are processed;
+ * otherwise, only 'name' is. 'only_if_a_exists' is passed through to
+ * process_name().
+ */
+static void
+process_section(const section_filter_t *filter) {
+ query_ctx_t *qctx = filter->qctx;
+ filter_aaaa_t mode = filter->mode;
+ dns_section_t section = filter->section;
+ const dns_name_t *name = filter->name;
+ dns_rdatatype_t type = filter->type;
+ bool only_if_a_exists = filter->only_if_a_exists;
+
+ dns_message_t *message = qctx->client->message;
+ isc_result_t result;
+
+ for (result = dns_message_firstname(message, section);
+ result == ISC_R_SUCCESS;
+ result = dns_message_nextname(message, section))
+ {
+ dns_name_t *cur = NULL;
+ dns_message_currentname(message, section, &cur);
+ if (name != NULL && !dns_name_equal(name, cur)) {
+ /*
+ * We only want to process 'name' and this is not it.
+ */
+ continue;
+ }
+
+ if (!process_name(qctx, mode, cur, type, only_if_a_exists)) {
+ /*
+ * Response was not modified, do not touch the AD bit.
+ */
+ continue;
+ }
+
+ if (section == DNS_SECTION_ANSWER ||
+ section == DNS_SECTION_AUTHORITY)
+ {
+ message->flags &= ~DNS_MESSAGEFLAG_AD;
+ }
+ }
+}
+
+/*
+ * Initialize filter state, fetching it from a memory pool and storing it
+ * in a hash table keyed according to the client object; this enables us to
+ * retrieve persistent data related to a client query for as long as the
+ * object persists.
+ */
+static ns_hookresult_t
+filter_qctx_initialize(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state;
+
+ *resp = ISC_R_UNSET;
+
+ client_state = client_state_get(qctx, inst);
+ if (client_state == NULL) {
+ client_state_create(qctx, inst);
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Determine whether this client should have AAAA filtered or not, based on
+ * the client address family and the settings of filter-aaaa-on-v4 and
+ * filter-aaaa-on-v6.
+ */
+static ns_hookresult_t
+filter_prep_response_begin(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result;
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state == NULL) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (inst->v4_aaaa != NONE || inst->v6_aaaa != NONE) {
+ result = ns_client_checkaclsilent(qctx->client, NULL,
+ inst->aaaa_acl, true);
+ if (result == ISC_R_SUCCESS && inst->v4_aaaa != NONE &&
+ is_v4_client(qctx->client))
+ {
+ client_state->mode = inst->v4_aaaa;
+ } else if (result == ISC_R_SUCCESS && inst->v6_aaaa != NONE &&
+ is_v6_client(qctx->client))
+ {
+ client_state->mode = inst->v6_aaaa;
+ }
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Hide AAAA rrsets if there is a matching A. Trigger recursion if
+ * necessary to find out whether an A exists.
+ *
+ * (This version is for processing answers to explicit AAAA queries; ANY
+ * queries are handled in filter_respond_any_found().)
+ */
+static ns_hookresult_t
+filter_respond_begin(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+ isc_result_t result = ISC_R_UNSET;
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state == NULL) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (client_state->mode != BREAK_DNSSEC &&
+ (client_state->mode != FILTER ||
+ (WANTDNSSEC(qctx->client) && qctx->sigrdataset != NULL &&
+ dns_rdataset_isassociated(qctx->sigrdataset))))
+ {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ if (qctx->qtype == dns_rdatatype_aaaa) {
+ dns_rdataset_t *trdataset;
+ trdataset = ns_client_newrdataset(qctx->client);
+ result = dns_db_findrdataset(
+ qctx->db, qctx->node, qctx->version, dns_rdatatype_a, 0,
+ qctx->client->now, trdataset, NULL);
+ if (dns_rdataset_isassociated(trdataset)) {
+ dns_rdataset_disassociate(trdataset);
+ }
+ ns_client_putrdataset(qctx->client, &trdataset);
+
+ /*
+ * We found an AAAA. If we also found an A, then the AAAA
+ * must not be rendered.
+ *
+ * If the A is not in our cache, then any result other than
+ * DNS_R_DELEGATION or ISC_R_NOTFOUND means there is no A,
+ * and so AAAAs are okay.
+ *
+ * We assume there is no A if we can't recurse for this
+ * client. That might be the wrong answer, but what else
+ * can we do? Besides, the fact that we have the AAAA and
+ * are using this mechanism in the first place suggests
+ * that we care more about As than AAAAs, and would have
+ * cached an A if it existed.
+ */
+ if (result == ISC_R_SUCCESS) {
+ mark_as_rendered(qctx->rdataset, qctx->sigrdataset);
+ qctx->client->message->flags &= ~DNS_MESSAGEFLAG_AD;
+ client_state->flags |= FILTER_AAAA_FILTERED;
+ } else if (!qctx->authoritative && RECURSIONOK(qctx->client) &&
+ (result == DNS_R_DELEGATION ||
+ result == ISC_R_NOTFOUND))
+ {
+ /*
+ * This is an ugly kludge to recurse
+ * for the A and discard the result.
+ *
+ * Continue to add the AAAA now.
+ * We'll make a note to not render it
+ * if the recursion for the A succeeds.
+ */
+ result = ns_query_recurse(qctx->client, dns_rdatatype_a,
+ qctx->client->query.qname,
+ NULL, NULL, qctx->resuming);
+ if (result == ISC_R_SUCCESS) {
+ client_state->flags |= FILTER_AAAA_RECURSING;
+ qctx->client->query.attributes |=
+ NS_QUERYATTR_RECURSING;
+ }
+ }
+ } else if (qctx->qtype == dns_rdatatype_a &&
+ (client_state->flags & FILTER_AAAA_RECURSING) != 0)
+ {
+ const section_filter_t filter_answer = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ANSWER,
+ .name = qctx->fname,
+ .type = dns_rdatatype_aaaa,
+ };
+ process_section(&filter_answer);
+
+ client_state->flags &= ~FILTER_AAAA_RECURSING;
+
+ result = ns_query_done(qctx);
+
+ *resp = result;
+
+ return (NS_HOOK_RETURN);
+ }
+
+ *resp = result;
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * When answering an ANY query, remove AAAA if A is present.
+ */
+static ns_hookresult_t
+filter_respond_any_found(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state != NULL && client_state->mode != NONE) {
+ /*
+ * If we are authoritative, require an A record to be
+ * present before filtering out AAAA records; otherwise,
+ * just assume an A record exists even if it was not in the
+ * cache (and therefore is not in the response message),
+ * thus proceeding with filtering out AAAA records.
+ */
+ const section_filter_t filter_answer = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ANSWER,
+ .name = qctx->tname,
+ .type = dns_rdatatype_aaaa,
+ .only_if_a_exists = qctx->authoritative,
+ };
+ process_section(&filter_answer);
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * Hide AAAA rrsets in the additional section if there is a matching A, and
+ * hide NS in the authority section if AAAA was filtered in the answer
+ * section.
+ */
+static ns_hookresult_t
+filter_query_done_send(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+ filter_data_t *client_state = client_state_get(qctx, inst);
+
+ *resp = ISC_R_UNSET;
+
+ if (client_state != NULL && client_state->mode != NONE) {
+ const section_filter_t filter_additional = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_ADDITIONAL,
+ .type = dns_rdatatype_aaaa,
+ .only_if_a_exists = true,
+ };
+ process_section(&filter_additional);
+
+ if ((client_state->flags & FILTER_AAAA_FILTERED) != 0) {
+ const section_filter_t filter_authority = {
+ .qctx = qctx,
+ .mode = client_state->mode,
+ .section = DNS_SECTION_AUTHORITY,
+ .type = dns_rdatatype_ns,
+ };
+ process_section(&filter_authority);
+ }
+ }
+
+ return (NS_HOOK_CONTINUE);
+}
+
+/*
+ * If the client is being detached, then we can delete our persistent data
+ * from hash table and return it to the memory pool.
+ */
+static ns_hookresult_t
+filter_qctx_destroy(void *arg, void *cbdata, isc_result_t *resp) {
+ query_ctx_t *qctx = (query_ctx_t *)arg;
+ filter_instance_t *inst = (filter_instance_t *)cbdata;
+
+ *resp = ISC_R_UNSET;
+
+ if (!qctx->detach_client) {
+ return (NS_HOOK_CONTINUE);
+ }
+
+ client_state_destroy(qctx, inst);
+
+ return (NS_HOOK_CONTINUE);
+}
diff --git a/bin/plugins/filter-aaaa.rst b/bin/plugins/filter-aaaa.rst
new file mode 100644
index 0000000..8cd7556
--- /dev/null
+++ b/bin/plugins/filter-aaaa.rst
@@ -0,0 +1,90 @@
+.. Copyright (C) Internet Systems Consortium, Inc. ("ISC")
+..
+.. SPDX-License-Identifier: MPL-2.0
+..
+.. This Source Code Form is subject to the terms of the Mozilla Public
+.. License, v. 2.0. If a copy of the MPL was not distributed with this
+.. file, you can obtain one at https://mozilla.org/MPL/2.0/.
+..
+.. See the COPYRIGHT file distributed with this work for additional
+.. information regarding copyright ownership.
+
+.. highlight: console
+
+.. iscman:: filter-aaaa
+.. _man_filter-aaaa:
+
+filter-aaaa.so - filter AAAA in DNS responses when A is present
+---------------------------------------------------------------
+
+Synopsis
+~~~~~~~~
+
+:program:`plugin query` "filter-aaaa.so" [{ parameters }];
+
+Description
+~~~~~~~~~~~
+
+:program:`filter-aaaa.so` is a query plugin module for :iscman:`named`, enabling
+:iscman:`named` to omit some IPv6 addresses when responding to clients.
+
+Until BIND 9.12, this feature was implemented natively in :iscman:`named` and
+enabled with the ``filter-aaaa`` ACL and the ``filter-aaaa-on-v4`` and
+``filter-aaaa-on-v6`` options. These options are now deprecated in
+:iscman:`named.conf` but can be passed as parameters to the
+``filter-aaaa.so`` plugin, for example:
+
+::
+
+ plugin query "filter-aaaa.so" {
+ filter-aaaa-on-v4 yes;
+ filter-aaaa-on-v6 yes;
+ filter-aaaa { 192.0.2.1; 2001:db8:2::1; };
+ };
+
+This module is intended to aid transition from IPv4 to IPv6 by
+withholding IPv6 addresses from DNS clients which are not connected to
+the IPv6 Internet, when the name being looked up has an IPv4 address
+available. Use of this module is not recommended unless absolutely
+necessary.
+
+Note: This mechanism can erroneously cause other servers not to give
+AAAA records to their clients. If a recursing server with both IPv6 and
+IPv4 network connections queries an authoritative server using this
+mechanism via IPv4, it is denied AAAA records even if its client is
+using IPv6.
+
+Options
+~~~~~~~
+
+``filter-aaaa``
+ This option specifies a list of client addresses for which AAAA filtering is to
+ be applied. The default is ``any``.
+
+``filter-aaaa-on-v4``
+ If set to ``yes``, this option indicates that the DNS client is at an IPv4 address, in
+ ``filter-aaaa``. If the response does not include DNSSEC
+ signatures, then all AAAA records are deleted from the response. This
+ filtering applies to all responses, not only authoritative
+ ones.
+
+ If set to ``break-dnssec``, then AAAA records are deleted even when
+ DNSSEC is enabled. As suggested by the name, this causes the response
+ to fail to verify, because the DNSSEC protocol is designed to detect
+ deletions.
+
+ This mechanism can erroneously cause other servers not to give AAAA
+ records to their clients. If a recursing server with both IPv6 and IPv4
+ network connections queries an authoritative server using this
+ mechanism via IPv4, it is denied AAAA records even if its client is
+ using IPv6.
+
+``filter-aaaa-on-v6``
+ This option is identical to ``filter-aaaa-on-v4``, except that it filters AAAA responses
+ to queries from IPv6 clients instead of IPv4 clients. To filter all
+ responses, set both options to ``yes``.
+
+See Also
+~~~~~~~~
+
+BIND 9 Administrator Reference Manual.