Attention is currently required from: flichtenheld, plaisthos.

Hello flichtenheld, plaisthos,

I'd like you to reexamine a change. Please visit

    http://gerrit.openvpn.net/c/openvpn/+/838?usp=email

to look at the new patch set (#12).


Change subject: dns: apply settings via script on unixoid systems
......................................................................

dns: apply settings via script on unixoid systems

This introduces a new script hook, the dns-script and implements such a
script for a few popular systems (and a default for the not so popular
ones). Like the name suggests this script is soleley for dealing with
modifying how names are resolved when the VPN pushes some --dns
settings.

The default dns script is part of the distribution and is installed with
openvpn. You can change the path the script is located at as a compile
time option, defaults to libexecdir. There's also a new runtime option
--dns-script, which can run a custom script.

Change-Id: Ifbe4ffb44d3bfcaa50adb38cacb3436fcdc71b10
Signed-off-by: Heiko Hund <he...@ist.eigentlich.net>
---
M .gitignore
M CMakeLists.txt
M configure.ac
M distro/Makefile.am
A distro/dns-scripts/Makefile.am
A distro/dns-scripts/haikuos_file-dns-updown.sh
A distro/dns-scripts/openresolv-dns-updown.sh
A distro/dns-scripts/resolvconf_file-dns-updown.sh
A distro/dns-scripts/systemd-dns-updown.sh
M doc/man-sections/script-options.rst
M src/openvpn/Makefile.am
M src/openvpn/dns.c
M src/openvpn/dns.h
M src/openvpn/options.c
14 files changed, 622 insertions(+), 8 deletions(-)


  git pull ssh://gerrit.openvpn.net:29418/openvpn refs/changes/38/838/12

diff --git a/.gitignore b/.gitignore
index db8bb73..04523af 100644
--- a/.gitignore
+++ b/.gitignore
@@ -49,6 +49,7 @@
 /doc/doxygen/latex/
 /doc/doxygen/openvpn.doxyfile
 distro/systemd/*.service
+distro/dns-scripts/dns-updown
 sample/sample-keys/sample-ca/
 vendor/cmocka_build
 vendor/dist
diff --git a/CMakeLists.txt b/CMakeLists.txt
index b04adce..2696691 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -41,7 +41,8 @@
 option(USE_WERROR "Treat compiler warnings as errors (-Werror)" ON)
 option(FAKE_ANDROID "Target Android but do not use actual cross 
compile/Android cmake to build for simple compile checks on Linux")

-set(PLUGIN_DIR /usr/local/lib/openvpn/plugins CACHE FILEPATH "Location of the 
plugin directory")
+set(DNS_UPDOWN_PATH "${CMAKE_INSTALL_PREFIX}/libexec/openvpn/dns-updown" CACHE 
STRING "Default location for the DNS up/down script")
+set(PLUGIN_DIR "${CMAKE_INSTALL_PREFIX}/lib/openvpn/plugins" CACHE FILEPATH 
"Location of the plugin directory")

 # Create machine readable compile commands
 option(ENABLE_COMPILE_COMMANDS "Generate compile_commands.json and a symlink 
for clangd to find it" OFF)
@@ -577,6 +578,8 @@

 add_library_deps(openvpn)

+target_compile_options(openvpn PRIVATE 
-DDNS_UPDOWN_PATH=\"${DNS_UPDOWN_PATH}\")
+
 if(MINGW)
     target_compile_options(openvpn PRIVATE -municode -UUNICODE)
     target_link_options(openvpn PRIVATE -municode)
diff --git a/configure.ac b/configure.ac
index 9777e36..45d3ac1 100644
--- a/configure.ac
+++ b/configure.ac
@@ -315,37 +315,50 @@
        plugindir="\${libdir}/openvpn/plugins"
 fi

+AC_ARG_VAR([SCRIPTDIR], [Path of script directory 
@<:@default=PKGLIBEXECDIR@:>@])
+if test -n "${SCRIPTDIR}"; then
+       scriptdir="${SCRIPTDIR}"
+else
+       scriptdir="\${pkglibexecdir}"
+fi
+
 AC_DEFINE_UNQUOTED([TARGET_ALIAS], ["${host}"], [A string representing our 
host])
-AM_CONDITIONAL([TARGET_LINUX], [false])
+AM_CONDITIONAL([ENABLE_DNS_SCRIPT],[true])
 case "$host" in
        *-*-linux*)
                AC_DEFINE([TARGET_LINUX], [1], [Are we running on Linux?])
-               AM_CONDITIONAL([TARGET_LINUX], [true])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["L"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["systemd"])
                have_sitnl="yes"
                pkg_config_required="yes"
                ;;
        *-*-solaris*)
                AC_DEFINE([TARGET_SOLARIS], [1], [Are we running on Solaris?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["S"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["resolvconf_file"])
                CPPFLAGS="$CPPFLAGS -D_XPG4_2"
                test -x /bin/bash && SHELL="/bin/bash"
                ;;
        *-*-openbsd*)
                AC_DEFINE([TARGET_OPENBSD], [1], [Are we running on OpenBSD?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["O"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["resolvconf_file"])
                ;;
        *-*-freebsd*)
                AC_DEFINE([TARGET_FREEBSD], [1], [Are we running on FreeBSD?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["F"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["openresolv"])
                ;;
        *-*-netbsd*)
                AC_DEFINE([TARGET_NETBSD], [1], [Are we running NetBSD?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["N"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["openresolv"])
                ;;
        *-*-darwin*)
                AC_DEFINE([TARGET_DARWIN], [1], [Are we running on Mac OS X?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["M"], [Target prefix])
+               AM_CONDITIONAL([ENABLE_DNS_SCRIPT],[false])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["resolvconf_file"])
                have_tap_header="yes"
                ac_cv_type_struct_in_pktinfo=no
                ;;
@@ -353,6 +366,8 @@
                AC_DEFINE([TARGET_WIN32], [1], [Are we running WIN32?])
                AC_DEFINE([ENABLE_DCO], [1], [DCO is always enabled on Windows])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["W"], [Target prefix])
+               AM_CONDITIONAL([ENABLE_DNS_SCRIPT],[false])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["windows"])
                CPPFLAGS="${CPPFLAGS} -DWIN32_LEAN_AND_MEAN"
                CPPFLAGS="${CPPFLAGS} -DNTDDI_VERSION=NTDDI_VISTA 
-D_WIN32_WINNT=_WIN32_WINNT_VISTA"
                WIN32=yes
@@ -360,10 +375,12 @@
        *-*-dragonfly*)
                AC_DEFINE([TARGET_DRAGONFLY], [1], [Are we running on 
DragonFlyBSD?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["D"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["openresolv"])
                ;;
        *-aix*)
                AC_DEFINE([TARGET_AIX], [1], [Are we running AIX?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["A"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["resolvconf_file"])
                ROUTE="/usr/sbin/route"
                have_tap_header="yes"
                ac_cv_header_net_if_h="no"      # exists, but breaks things
@@ -371,10 +388,12 @@
        *-*-haiku*)
                AC_DEFINE([TARGET_HAIKU], [1], [Are we running Haiku?])
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["H"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["haikuos_file"])
                LIBS="${LIBS} -lnetwork"
                ;;
        *)
                AC_DEFINE_UNQUOTED([TARGET_PREFIX], ["X"], [Target prefix])
+               AC_SUBST([DNS_UPDOWN_TYPE], ["resolvconf_file"])
                have_tap_header="yes"
                ;;
 esac
@@ -1505,6 +1524,7 @@

 sampledir="\$(docdir)/sample"
 AC_SUBST([plugindir])
+AC_SUBST([scriptdir])
 AC_SUBST([sampledir])

 AC_SUBST([systemdunitdir])
@@ -1541,6 +1561,7 @@
        Makefile
        distro/Makefile
        distro/systemd/Makefile
+       distro/dns-scripts/Makefile
        doc/Makefile
        doc/doxygen/Makefile
        doc/doxygen/openvpn.doxyfile
diff --git a/distro/Makefile.am b/distro/Makefile.am
index 7a588da..b8fb85b 100644
--- a/distro/Makefile.am
+++ b/distro/Makefile.am
@@ -13,3 +13,7 @@
        $(srcdir)/Makefile.in

 SUBDIRS = systemd
+
+if ENABLE_DNS_SCRIPT
+SUBDIRS += dns-scripts
+endif
diff --git a/distro/dns-scripts/Makefile.am b/distro/dns-scripts/Makefile.am
new file mode 100644
index 0000000..ec7bfde
--- /dev/null
+++ b/distro/dns-scripts/Makefile.am
@@ -0,0 +1,28 @@
+#
+#  OpenVPN -- An application to securely tunnel IP networks
+#             over a single UDP port, with support for SSL/TLS-based
+#             session authentication and key exchange,
+#             packet encryption, packet authentication, and
+#             packet compression.
+#
+#  Copyright (C) 2002-2024 OpenVPN Inc <sa...@openvpn.net>
+#
+
+MAINTAINERCLEANFILES = \
+       $(srcdir)/Makefile.in
+
+EXTRA_DIST = \
+       systemd-dns-updown.sh \
+       openresolv-dns-updown.sh \
+       haikuos_file-dns-updown.sh \
+       resolvconf_file-dns-updown.sh
+
+script_SCRIPTS = \
+       dns-updown
+
+CLEANFILES = $(script_SCRIPTS)
+
+dns-updown: @dns_updown_t...@-dns-updown.sh
+       cp ${srcdir}/@dns_updown_t...@-dns-updown.sh $@
+
+all: $(script_SCRIPTS)
diff --git a/distro/dns-scripts/haikuos_file-dns-updown.sh 
b/distro/dns-scripts/haikuos_file-dns-updown.sh
new file mode 100644
index 0000000..1b03e9c
--- /dev/null
+++ b/distro/dns-scripts/haikuos_file-dns-updown.sh
@@ -0,0 +1,84 @@
+#!/bin/sh
+#
+# Simple OpenVPN up/down script for modifying Haiku OS resolv.conf
+# (C) Copyright 2024 OpenVPN Inc <sa...@openvpn.net>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Example env from openvpn (most are not applied):
+#
+#   dev tun0
+#   script-type dns-up
+#   dns_search_domain_1 mycorp.in
+#   dns_search_domain_2 eu.mycorp.com
+#   dns_server_1_address_1 192.168.99.254
+#   dns_server_1_address_2 fd00::99:53
+#   dns_server_1_port_1 53
+#   dns_server_1_port_2 53
+#   dns_server_1_resolve_domain_1 mycorp.in
+#   dns_server_1_resolve_domain_2 eu.mycorp.com
+#   dns_server_1_dnssec true
+#   dns_server_1_transport DoH
+#   dns_server_1_sni dns.mycorp.in
+#
+
+set -e +u
+
+conly_standard_server_ports() {
+    i=1
+    while true; do
+        eval addr=\"\$dns_server_${n}_address_${i}\"
+        [ -n "$addr" ] || return 0
+
+        eval port=\"\$dns_server_${n}_port_${i}\"
+        [ -z "$port" -o "$port" = "53" ] || return 1
+
+        i=$(expr $i + 1)
+    done
+}
+
+onf=/boot/system/settings/network/resolv.conf
+test -e "$conf" || exit 1
+case "${script_type}" in
+dns-up)
+    n=1
+    while :; do
+        eval addr=\"\$dns_server_${n}_address_1\"
+        [ -n "$addr" ] || {
+            echo "setting DNS failed, no compatible server profile"
+            exit 1
+        }
+
+        # Skip server profiles which require DNSSEC,
+        # secure transport or use a custom port
+        eval dnssec=\"\$dns_server_${n}_dnssec\"
+        eval transport=\"\$dns_server_${n}_transport\"
+        [ -z "$transport" -o "$transport" = "plain" ] \
+            && [ -z "$dnssec" -o "$dnssec" = "no" ] \
+            && only_standard_server_ports && break
+
+        n=$(expr $n + 1)
+    done
+
+    eval addr1=\"\$dns_server_${n}_address_1\"
+    eval addr2=\"\$dns_server_${n}_address_2\"
+    eval addr3=\"\$dns_server_${n}_address_3\"
+    text="### openvpn ${dev} begin ###\n"
+    text="${text}nameserver $addr1\n"
+    test -z "$addr2" || text="${text}nameserver $addr2\n"
+    test -z "$addr3" || text="${text}nameserver $addr3\n"
+
+    test -z "$dns_search_domain_1" || {
+        for i in $(seq 1 6); do
+            eval domains=\"$domains\$dns_search_domain_${i} \" || break
+        done
+        text="${text}search $domains\n"
+    }
+    text="${text}### openvpn ${dev} end ###"
+
+    sed -i "1i${text}" "$conf"
+    ;;
+dns-down)
+    sed -i "/### openvpn ${dev} begin ###/,/### openvpn ${dev} end ###/d" 
"$conf"
+    ;;
+esac
diff --git a/distro/dns-scripts/openresolv-dns-updown.sh 
b/distro/dns-scripts/openresolv-dns-updown.sh
new file mode 100644
index 0000000..1b218f5
--- /dev/null
+++ b/distro/dns-scripts/openresolv-dns-updown.sh
@@ -0,0 +1,89 @@
+#!/bin/sh
+#
+# Simple OpenVPN up/down script for openresolv integration
+# (C) Copyright 2016 Baptiste Daroussin
+#               2024 OpenVPN Inc <sa...@openvpn.net>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Example env from openvpn (most are not applied):
+#
+#   dev tun0
+#   script-type dns-up
+#   dns_search_domain_1 mycorp.in
+#   dns_search_domain_2 eu.mycorp.com
+#   dns_server_1_address_1 192.168.99.254
+#   dns_server_1_address_2 fd00::99:53
+#   dns_server_1_port_1 53
+#   dns_server_1_port_2 53
+#   dns_server_1_resolve_domain_1 mycorp.in
+#   dns_server_1_resolve_domain_2 eu.mycorp.com
+#   dns_server_1_dnssec true
+#   dns_server_1_transport DoH
+#   dns_server_1_sni dns.mycorp.in
+#
+
+set -e +u
+
+only_standard_server_ports() {
+    i=1
+    while true; do
+        eval addr=\"\$dns_server_${n}_address_${i}\"
+        [ -n "$addr" ] || return 0
+
+        eval port=\"\$dns_server_${n}_port_${i}\"
+        [ -z "$port" -o "$port" = "53" ] || return 1
+
+        i=$(expr $i + 1)
+    done
+}
+
+: ${script_type:=dns-down}
+case "${script_type}" in
+dns-up)
+    n=1
+    while :; do
+        eval addr=\"\$dns_server_${n}_address_1\"
+        [ -n "$addr" ] || {
+            echo "setting DNS failed, no compatible server profile"
+            exit 1
+        }
+
+        # Skip server profiles which require DNSSEC,
+        # secure transport or use a custom port
+        eval dnssec=\"\$dns_server_${n}_dnssec\"
+        eval transport=\"\$dns_server_${n}_transport\"
+        [ -z "$transport" -o "$transport" = "plain" ] \
+            && [ -z "$dnssec" -o "$dnssec" = "no" ] \
+            && only_standard_server_ports && break
+
+        n=$(expr $n + 1)
+    done
+
+    {
+        i=1
+        maxns=3
+        while :; do
+            maxns=$((maxns - 1))
+            [ $maxns -gt 0 ] || break
+            eval option=\"\$dns_server_${n}_address_${i}\" || break
+            [ "${option}" ] || break
+            i=$((i + 1))
+            echo "nameserver ${option}"
+        done
+        i=1
+        maxdom=6
+        while :; do
+            maxdom=$((maxdom - 1))
+            [ $maxdom -gt 0 ] || break
+            eval option=\"\$dns_search_domain_${i}\" || break
+            [ "${option}" ] || break
+            i=$((i + 1))
+            echo "search ${option}"
+        done
+    } | /sbin/resolvconf -a "${dev}"
+    ;;
+dns-down)
+    /sbin/resolvconf -d "${dev}" -f
+    ;;
+esac
diff --git a/distro/dns-scripts/resolvconf_file-dns-updown.sh 
b/distro/dns-scripts/resolvconf_file-dns-updown.sh
new file mode 100644
index 0000000..c469490
--- /dev/null
+++ b/distro/dns-scripts/resolvconf_file-dns-updown.sh
@@ -0,0 +1,84 @@
+#!/bin/sh
+#
+# Simple OpenVPN up/down script for modifying /etc/resolv.conf
+# (C) Copyright 2024 OpenVPN Inc <sa...@openvpn.net>
+#
+# SPDX-License-Identifier: BSD-2-Clause
+#
+# Example env from openvpn (most are not applied):
+#
+#   dev tun0
+#   script-type dns-up
+#   dns_search_domain_1 mycorp.in
+#   dns_search_domain_2 eu.mycorp.com
+#   dns_server_1_address_1 192.168.99.254
+#   dns_server_1_address_2 fd00::99:53
+#   dns_server_1_port_1 53
+#   dns_server_1_port_2 53
+#   dns_server_1_resolve_domain_1 mycorp.in
+#   dns_server_1_resolve_domain_2 eu.mycorp.com
+#   dns_server_1_dnssec true
+#   dns_server_1_transport DoH
+#   dns_server_1_sni dns.mycorp.in
+#
+
+set -e +u
+
+only_standard_server_ports() {
+    i=1
+    while true; do
+        eval addr=\"\$dns_server_${n}_address_${i}\"
+        [ -n "$addr" ] || return 0
+
+        eval port=\"\$dns_server_${n}_port_${i}\"
+        [ -z "$port" -o "$port" = "53" ] || return 1
+
+        i=$(expr $i + 1)
+    done
+}
+
+conf=/etc/resolv.conf
+test -e "$conf" || exit 1
+case "${script_type}" in
+dns-up)
+    n=1
+    while :; do
+        eval addr=\"\$dns_server_${n}_address_1\"
+        [ -n "$addr" ] || {
+            echo "setting DNS failed, no compatible server profile"
+            exit 1
+        }
+
+        # Skip server profiles which require DNSSEC,
+        # secure transport or use a custom port
+        eval dnssec=\"\$dns_server_${n}_dnssec\"
+        eval transport=\"\$dns_server_${n}_transport\"
+        [ -z "$transport" -o "$transport" = "plain" ] \
+            && [ -z "$dnssec" -o "$dnssec" = "no" ] \
+            && only_standard_server_ports && break
+
+        n=$(expr $n + 1)
+    done
+
+    eval addr1=\"\$dns_server_${n}_address_1\"
+    eval addr2=\"\$dns_server_${n}_address_2\"
+    eval addr3=\"\$dns_server_${n}_address_3\"
+    text="### openvpn ${dev} begin ###\n"
+    text="${text}nameserver $addr1\n"
+    test -z "$addr2" || text="${text}nameserver $addr2\n"
+    test -z "$addr3" || text="${text}nameserver $addr3\n"
+
+    test -z "$dns_search_domain_1" || {
+        for i in $(seq 1 6); do
+            eval domains=\"$domains\$dns_search_domain_${i} \" || break
+        done
+        text="${text}search $domains\n"
+    }
+    text="${text}### openvpn ${dev} end ###"
+
+    sed -i "1i${text}" "$conf"
+    ;;
+dns-down)
+    sed -i "/### openvpn ${dev} begin ###/,/### openvpn ${dev} end ###/d" 
"$conf"
+    ;;
+esac
diff --git a/distro/dns-scripts/systemd-dns-updown.sh 
b/distro/dns-scripts/systemd-dns-updown.sh
new file mode 100644
index 0000000..69bbebf
--- /dev/null
+++ b/distro/dns-scripts/systemd-dns-updown.sh
@@ -0,0 +1,194 @@
+#!/bin/bash
+#
+# dns-updown - add/remove openvpn provided DNS information
+#
+# Copyright (C) 2024 OpenVPN Inc <sa...@openvpn.net>
+#
+# SPDX-License-Identifier: GPL-2.0
+#
+# Add/remove openvpn DNS settings from the env into/from
+# the system. Supported backends in this order:
+#
+#   * systemd-resolved
+#   * resolvconf
+#
+# Example env from openvpn (not all are always applied):
+#
+#   dev tun0
+#   script-type dns-up
+#   dns_search_domain_1 mycorp.in
+#   dns_search_domain_2 eu.mycorp.com
+#   dns_server_1_address_1 192.168.99.254
+#   dns_server_1_address_2 fd00::99:53
+#   dns_server_1_port_1 53
+#   dns_server_1_port_2 53
+#   dns_server_1_resolve_domain_1 mycorp.in
+#   dns_server_1_resolve_domain_2 eu.mycorp.com
+#   dns_server_1_dnssec true
+#   dns_server_1_transport DoH
+#   dns_server_1_sni dns.mycorp.in
+#
+
+function do_resolved_servers {
+    local sni=""
+    local transport_var=dns_server_${n}_transport
+    local sni_var=dns_server_${n}_sni
+    [ "${!transport_var}" = "DoT" ] && sni="#${!sni_var}"
+
+    local i=1
+    local addrs=""
+    while :; do
+        local addr_var=dns_server_${n}_address_${i}
+        local addr="${!addr_var}"
+        [ -n "$addr" ] || break
+
+        local port_var=dns_server_${n}_port_${i}
+        if [ -n "${!port_var}" ]; then
+            if [[ "$addr" =~ : ]]; then
+                addr="[$addr]"
+            fi
+            addrs+="${addr}:${!port_var}${sni} "
+        else
+            addrs+="${addr}${sni} "
+        fi
+        i=$((i+1))
+    done
+
+    resolvectl dns "$dev" $addrs
+}
+
+function do_resolved_domains {
+    local list=""
+    for domain_var in ${!dns_search_domain_*}; do
+        list+="${!domain_var} "
+    done
+    local domain_var=dns_server_${n}_resolve_domain_1
+    if [ -z "${!domain_var}" ]; then
+        resolvectl default-route "$dev" true
+        list+="~."
+    else
+        resolvectl default-route "$dev" false
+        local i=1
+        while :; do
+            domain_var=dns_server_${n}_resolve_domain_${i}
+            [ -n "${!domain_var}" ] || break
+            # Add as split domain (~ prefix), if it doesn't already exist
+            [[ "$list" =~ (^| )"${!domain_var}"( |$) ]] \
+                || list+="~${!domain_var} "
+            i=$((i+1))
+        done
+    fi
+
+    resolvectl domain "$dev" $list
+}
+
+function do_resolved_dnssec {
+    local dnssec_var=dns_server_${n}_dnssec
+    if [ "${!dnssec_var}" = "optional" ]; then
+        resolvectl dnssec "$dev" allow-downgrade
+    elif [ "${!dnssec_var}" = "yes" ]; then
+        resolvectl dnssec "$dev" true
+    else
+        resolvectl dnssec "$dev" false
+    fi
+}
+
+function do_resolved_dnsovertls {
+    local transport_var=dns_server_${n}_transport
+    if [ "${!transport_var}" = "DoT" ]; then
+        resolvectl dnsovertls "$dev" true
+    else
+        resolvectl dnsovertls "$dev" false
+    fi
+}
+
+function do_resolved {
+    [[ "$(readlink /etc/resolv.conf)" =~ systemd ]] || return 1
+
+    n=1
+    while :; do
+        local addr_var=dns_server_${n}_address_1
+        [ -n "${!addr_var}" ] || {
+            echo "setting DNS failed, no compatible server profile"
+            return 1
+        }
+
+        # Skip server profiles which require DNS-over-HTTPS
+        local transport_var=dns_server_${n}_transport
+        [ -n "${!transport_var}" -a "${!transport_var}" = "DoH" ] || break
+
+        n=$((n+1))
+    done
+
+    if [ "$script_type" = "dns-up" ]; then
+        echo "setting DNS using resolvectl"
+        do_resolved_servers
+        do_resolved_domains
+        do_resolved_dnssec
+        do_resolved_dnsovertls
+    else
+        echo "unsetting DNS using resolvectl"
+        resolvectl revert "$dev"
+    fi
+
+    return 0
+}
+
+function only_standard_server_ports {
+    local i=1
+    while :; do
+        local addr_var=dns_server_${n}_address_${i}
+        [ -n "${!addr_var}" ] || return 0
+
+        local port_var=dns_server_${n}_port_${i}
+        [ -z "${!port_var}" -o "${!port_var}" = "53" ] || return 1
+
+        i=$((i+1))
+    done
+}
+
+function do_resolvconf {
+    [ -x /sbin/resolvconf ] || return 1
+
+    n=1
+    while :; do
+        local server_addr_var=dns_server_${n}_address_1
+        [ -n "${!server_addr_var}" ] || {
+            echo "setting DNS failed, no compatible server profile"
+            return 1
+        }
+
+        # Skip server profiles which require DNSSEC,
+        # secure transport or use a custom port
+        local dnssec_var=dns_server_${n}_dnssec
+        local transport_var=dns_server_${n}_transport
+        [ -z "${!transport_var}" -o "${!transport_var}" = "plain" ] \
+            && [ -z "${!dnssec_var}" -o "${!dnssec_var}" = "no" ] \
+            && only_standard_server_ports && break
+
+        n=$((n+1))
+    done
+
+    if [ "$script_type" = "dns-up" ]; then
+        echo "setting DNS using resolvconf"
+        local domains=""
+        for domain_var in ${!dns_search_domain_*}; do
+            domains+="${!domain_var} "
+        done
+        {
+            local maxns=3
+            for addr_var in ${!dns_server_1_address_*}; do
+                [ $((maxns--)) -gt 0 ] || break
+                echo "nameserver ${!addr_var}"
+            done
+            [ -z "$domains" ] || echo "search $domains"
+        } | /sbin/resolvconf -a "$dev"
+    else
+        echo "unsetting DNS using resolvconf"
+        /sbin/resolvconf -d "$dev"
+    fi
+
+    return 0
+}
+
+do_resolved || do_resolvconf
diff --git a/doc/man-sections/script-options.rst 
b/doc/man-sections/script-options.rst
index 0d1f9ae..a671117 100644
--- a/doc/man-sections/script-options.rst
+++ b/doc/man-sections/script-options.rst
@@ -8,9 +8,13 @@
 Script Order of Execution
 -------------------------

+#. ``--dns-script``
+
+   Executed after TCP/UDP socket bind and TUN/TAP open, before ``--up``.
+
 #. ``--up``

-   Executed after TCP/UDP socket bind and TUN/TAP open.
+   Executed after TCP/UDP socket bind and TUN/TAP open, after ``--dns-script``.

 #. ``--tls-verify``

@@ -38,9 +42,13 @@

    Executed in ``--mode server`` mode on client instance shutdown.

+#. ``--dns-script``
+
+   Executed before TCP/UDP and TUN/TAP close, before ``--down``.
+
 #. ``--down``

-   Executed after TCP/UDP and TUN/TAP close.
+   Executed after TCP/UDP and TUN/TAP close, after ``--dns-script``.

 #. ``--learn-address``

@@ -173,7 +181,7 @@
         client-crresponse cmd

   OpenVPN will write the response of the client into a temporary file.
-  The filename will be passed as an argument to ``cmd``, and the file will be
+  The filename will be passed as an argument to ``cmd``, and the file will
   automatically deleted by OpenVPN after the script returns.

   The response is passed as is from the client. The script needs to check
@@ -235,6 +243,23 @@
   The ``--client-disconnect`` command is not passed any extra arguments
   (only those arguments specified in cmd, if any).

+--dns-script cmd | disable
+  Run command ``cmd``, instead of the default DNS command that comes with
+  openvpn. If ``cmd`` is ``disable`` no command is executed to set ``--dns``
+  options. If you write your own command, please make sure to ignore ``--dns``
+  server profiles that cannot be applied. Port, DNSSEC and secure transport
+  settings need to be adhered to. If split DNS is not possible a full redirect
+  can be used as a fallback. If not all of the server addresses or search 
domains
+  can be configured, apply them on the order they are listed in.
+
+  Note that ``--dns-script`` is not supported on Windows. DNS will
+  always be set by the service there.
+
+  Note that DNS-related ``--dhcp-option``s will not be handled by this hook.
+  If any ``--dns server`` option is present, DNS-related ``--dhcp-option``s 
will
+  be ignored. Otherwise foreign_option environment variables will be passed to
+  ``--up`` and ``--down`` hooks for backward compatibility.
+
 --down cmd
   Run command ``cmd`` after TUN/TAP device close (post ``--user`` UID
   change and/or ``--chroot`` ). ``cmd`` consists of a path to script (or
@@ -661,7 +686,7 @@
     names). Set prior to ``--up`` or ``--down`` script execution.

 :code:`dns_*`
-    The ``--dns`` configuration options will be made available to script
+    The ``--dns`` configuration options will be made available to 
``--dns-script``
     execution through this set of environment variables. Variables appear
     only if the corresponding option has a value assigned. For the semantics
     of each individual variable, please refer to the documentation for 
``--dns``.
diff --git a/src/openvpn/Makefile.am b/src/openvpn/Makefile.am
index 37af683..6664aae 100644
--- a/src/openvpn/Makefile.am
+++ b/src/openvpn/Makefile.am
@@ -30,7 +30,8 @@
        $(OPTIONAL_LZ4_CFLAGS) \
        $(OPTIONAL_PKCS11_HELPER_CFLAGS) \
        $(OPTIONAL_INOTIFY_CFLAGS) \
-       -DPLUGIN_LIBDIR=\"${plugindir}\"
+       -DPLUGIN_LIBDIR=\"${plugindir}\" \
+       -DDNS_UPDOWN_PATH=\"${scriptdir}/dns-updown\"

 if WIN32
 # we want unicode entry point but not the macro
diff --git a/src/openvpn/dns.c b/src/openvpn/dns.c
index b6e524f..6a4669f 100644
--- a/src/openvpn/dns.c
+++ b/src/openvpn/dns.c
@@ -30,6 +30,7 @@
 #include "dns.h"
 #include "socket.h"
 #include "options.h"
+#include "run_command.h"

 #ifdef _WIN32
 #include "win32.h"
@@ -262,6 +263,8 @@
     clone.search_domains = clone_dns_domains(o->search_domains, gc);
     clone.servers = clone_dns_servers(o->servers, gc);
     clone.servers_prepull = clone_dns_servers(o->servers_prepull, gc);
+    clone.script = o->script;
+    clone.user_defined_script = o->user_defined_script;

     return clone;
 }
@@ -548,6 +551,54 @@
     send_msg_iservice(o->msg_channel, &nrpt, sizeof(nrpt), &ack, "DNS");
 }

+#else /* ifdef _WIN32 */
+
+static void
+script_env_set(bool up, const struct dns_options *o, const struct tuntap *tt, 
struct env_set *es)
+{
+    setenv_str(es, "dev", tt->actual_name);
+    setenv_str(es, "script_type", up ? "dns-up" : "dns-down");
+    setenv_dns_options(o, es);
+}
+
+static int
+do_run_up_down_script(bool up, const struct dns_options *o, const struct 
tuntap *tt)
+{
+    struct gc_arena gc = gc_new();
+    struct argv argv = argv_new();
+    struct env_set *es = env_set_create(&gc);
+
+    script_env_set(up, o, tt, es);
+
+    argv_printf(&argv, "%s", o->script);
+    argv_msg(M_INFO, &argv);
+    int res;
+    if (o->user_defined_script)
+    {
+        res = openvpn_run_script(&argv, es, S_EXITCODE, "dns script");
+    }
+    else
+    {
+        res = openvpn_execve_check(&argv, es, S_EXITCODE, "WARNING: Failed 
running dns script");
+    }
+    argv_free(&argv);
+    gc_free(&gc);
+    return res;
+}
+
+static void
+run_up_down_script(bool up, struct options *o, const struct tuntap *tt)
+{
+    if (!o->dns_options.script)
+    {
+        return;
+    }
+
+    int status;
+    status = do_run_up_down_script(up, &o->dns_options, tt);
+    msg(M_INFO, "dns script exited with status %d", status);
+}
+
 #endif /* _WIN32 */

 void
@@ -666,5 +717,7 @@

 #ifdef _WIN32
     run_up_down_service(up, o, tt);
+#else
+    run_up_down_script(up, o, tt);
 #endif /* ifdef _WIN32 */
 }
diff --git a/src/openvpn/dns.h b/src/openvpn/dns.h
index f24e30b..38ced79 100644
--- a/src/openvpn/dns.h
+++ b/src/openvpn/dns.h
@@ -73,6 +73,8 @@
     struct dns_server *servers_prepull;
     struct dns_server *servers;
     struct gc_arena gc;
+    const char *script;
+    bool user_defined_script;
 };

 /**
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 11a19bb..48fefb2 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -528,6 +528,7 @@
     "                  sni <domain> : DNS server name indication\n"
     "--dns search-domains <domain> [domain ...]:\n"
     "                  Add domains to DNS domain search list\n"
+    "--dns-script cmd : Run cmd as user defined dns configuration script\n"
     "--auth-retry t  : How to handle auth failures.  Set t to\n"
     "                  none (default), interact, or nointeract.\n"
     "--static-challenge t e [<scrv1|concat>]: Enable static challenge/response 
protocol using\n"
@@ -919,6 +920,8 @@
 #ifndef ENABLE_DCO
     o->disable_dco = true;
 #endif /* ENABLE_DCO */
+
+    o->dns_options.script = DNS_UPDOWN_PATH;
 }

 void
@@ -8194,6 +8197,28 @@
         to->ip_win32_defined = true;
     }
 #endif /* ifdef _WIN32 */
+    else if (streq(p[0], "dns-script") && p[1])
+    {
+        VERIFY_PERMISSION(OPT_P_SCRIPT);
+        if (!no_more_than_n_args(msglevel, p, 2, NM_QUOTE_HINT))
+        {
+            goto err;
+        }
+        if (streq(p[1], "disable"))
+        {
+            options->dns_options.script = NULL;
+        }
+        else
+        {
+            if (options->dns_options.user_defined_script == false)
+            {
+                /* Unset the default script to prevent warnings */
+                options->dns_options.script = NULL;
+            }
+            set_user_script(options, &options->dns_options.script, p[1], p[0], 
false);
+            options->dns_options.user_defined_script = true;
+        }
+    }
     else if (streq(p[0], "dns") && p[1])
     {
         VERIFY_PERMISSION(OPT_P_DHCPDNS);

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