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#!/usr/bin/env bash |
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# |
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# Modified to support distributions that rely either on systemd-resolve |
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# (such as Ubuntu 18.04 or 20.04) or on NetworkManager/netconfig (such |
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# as OpenSUSE Leap/Tumbleweed) for DNS resolver setup |
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configure_logging() { |
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log_folder="/var/log/aws-vpn-client" |
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mkdir -p $log_folder |
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# $script_type is set by OpenVPN |
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if [[ $script_type == *up* ]]; then |
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log_file=$log_folder/configure-dns-up.log |
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elif [[ $script_type == *down* ]]; then |
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log_file=$log_folder/configure-dns-down.log |
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fi |
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if [[ -f "$log_file" ]]; then |
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rm -f "$log_file" |
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fi |
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} |
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log() { |
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echo "$(date) $1" >> "$log_file" |
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} |
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# Get distribution via lsb-release in order to support more |
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# than just Ubuntu 18.04 LTS (bionic) and 20.04 LTS (focal) |
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get_distribution() { |
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# if available, use LSB release utility |
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LSBREL=$(type -p lsb-release) |
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test -n "${LSBREL}" && dist=$("${LSBREL}" -s -i) || dist="" |
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} |
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check_systemd_resolve_status() { |
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output=$(systemd-resolve --status 2>&1) |
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exit_code=$? |
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log "'systemd-resolve --status' exit code: $exit_code output:" |
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log "$output" |
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} |
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call_systemd_resolved() { |
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log "Calling busctl with parameters '$*'" |
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output=$(busctl call "org.freedesktop.resolve1" "/org/freedesktop/resolve1" "org.freedesktop.resolve1.Manager" "$@" 2>&1) |
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exit_code=$? |
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log "busctl command exit code: $exit_code, output: $output" |
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if [[ $exit_code -ne 0 ]]; then |
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exit $exit_code |
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fi |
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} |
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# Remove DNS name servers from the resolver config |
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# file and add the ones passed on the argument list |
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edit_resolv_conf_servers() { |
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cp ${rslvcnf} ${rslvcnf}.ovpnsave |
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grep -v -e nameserver ${rslvcnf}.ovpnsave > ${rslvcnf} |
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for dsrv in "$@"; do |
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log "Adding DNS server: ${dsrv}" |
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echo "nameserver ${dsrv}" >> ${rslvcnf} |
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done |
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rm -f ${rslvcnf}.ovpnsave |
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} |
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# Remove DNS domain search list from the resolver |
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# config file and add new one from the argument list |
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edit_resolv_conf_search() { |
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cp ${rslvcnf} ${rslvcnf}.ovpnsave |
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grep -v -e search ${rslvcnf}.ovpnsave > ${rslvcnf} |
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log "Adding domain search list: ${*}" |
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echo "search ${@}" >> ${rslvcnf} |
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rm -f ${rslvcnf}.ovpnsave |
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} |
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# Refresh the Name Service Cache by restarting the nscd daemon |
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refresh_nscd() { |
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log "Refreshing the name service cache" |
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output=$(systemctl restart nscd 2>&1) |
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exit_code=$? |
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log "systemctl restart nscd exit code: $exit_code, output: $output" |
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} |
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# $foreign_option_<n> is set by OpenVPN. |
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# Currently we support DNS and DOMAIN types. |
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# Search domains are used in the order they appear in the OpenVPN config |
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# Example: |
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# "dhcp-option DNS 172.168.0.1" |
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# "dhcp-option DOMAIN amazon.com" |
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# "dhcp-option DOMAIN amazonaws.com" |
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# Domains will be set in the order 1) amazon.com, 2) amazonaws.com |
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# Client VPN service doesn't support IPv6. |
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get_dns_from_server() { |
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log "Getting DNS servers from OpenVPN" |
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for fopt in "${!foreign_option_@}"; do |
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fopt_val="${!fopt}" |
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log "$fopt from OpenVPN: $fopt_val" |
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if [[ "${fopt_val}" == *dhcp-option\ DNS* ]]; then |
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dns_server_count=$((dns_server_count + 1)) |
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# dhcp-option DNS 172.168.0.1 -> 172.168.0.1 |
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dns_server_ip="${fopt_val#dhcp-option DNS }" |
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# |
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# Append: 2 4 172 168 0 1 for the systemd-resolve case |
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# or simply the DNS server IP address for netconfig |
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# |
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test "${namesrv}" = "netconfig" && \ |
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dns_servers+=(${dns_server_ip}) || \ |
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dns_servers+=(2 4 ${dns_server_ip//./ }) |
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elif [[ "${fopt_val}" == *dhcp-option\ DOMAIN\ * ]]; then |
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dns_domain_count=$((dns_domain_count + 1)) |
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# dhcp-option DOMAIN example.com -> example.com |
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dns_domain="${fopt_val#dhcp-option DOMAIN }" |
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# |
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# For the netconfig case simply add the domain to the list |
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# |
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# For the systemd-resolve case [1]: |
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# "It takes a network interface index and an array of domains, each with |
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# a boolean parameter indicating whether the specified domain shall be |
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# used as a search domain (false), or just as a routing domain (true)" |
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# [1] https://www.freedesktop.org/software/systemd/man/org.freedesktop.resolve1.html |
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# |
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test "${namesrv}" = "netconfig" && \ |
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dns_domains+=(${dns_domain}) || \ |
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dns_domains+=("${dns_domain}" false) |
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elif [[ "${fopt_val}" == *dhcp-option\ DOMAIN-ROUTE* ]]; then |
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dns_domain_count=$((dns_domain_count + 1)) |
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# dhcp-option DOMAIN-ROUTE . -> . |
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dns_domain="${fopt_val#dhcp-option DOMAIN-ROUTE }" |
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# |
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# Domain route '~.' needs to be added to prevent DNS leakage |
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# https://github.com/systemd/systemd/issues/6076#issuecomment-387332572 |
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# |
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test "${namesrv}" = "netconfig" && \ |
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dns_domains+=(${dns_domain}) || \ |
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dns_domains+=("${dns_domain}" true) |
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fi |
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done |
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} |
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# $dev is set by OpenVPN |
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# "The actual name of the TUN/TAP device, including a unit number if it exists." |
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get_device_index() { |
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log "Getting device index for $dev" |
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device_info="$(ip link show dev "$dev")" |
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exit_code=$? |
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log "'ip link show dev "$dev"' exit code: $exit_code, output: $device_info" |
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if [[ $exit_code -ne 0 ]]; then |
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exit $exit_code |
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fi |
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device_index="${device_info%%:*}" |
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log "Device index for $dev: $device_index" |
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} |
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configure_dns() { |
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local -a dns_servers=() dns_domains=() |
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local -i dns_server_count=0 dns_domain_count=0 |
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local device_index |
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log "Configuring to use DNS servers from OpenVPN" |
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get_dns_from_server |
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if [[ $dns_server_count -eq 0 && $dns_domain_count -eq 0 ]]; then |
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log "No DNS configured for the endpoint" |
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return 0 |
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fi |
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# The device index is not needed for the netconfig case |
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test "${namesrv}" != "netconfig" && get_device_index |
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if [[ $dns_server_count -gt 0 ]]; then |
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case "${namesrv}" in |
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"netconfig") |
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log "Updating ${rslvcnf} DNS servers with: '${dns_servers[*]}'" |
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edit_resolv_conf_servers "${dns_servers[@]}" |
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;; |
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"systemd-resolve") |
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params=("$device_index" "$dns_server_count" "${dns_servers[@]}") |
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log "Calling SetLinkDNS with parameters: '${params[*]}'" |
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# Example: SetLinkDNS 'ia(iay)' 125 2 2 4 172 31 29 109 2 4 172 31 4 164 |
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call_systemd_resolved SetLinkDNS 'ia(iay)' "${params[@]}" |
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;; |
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*) |
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;; |
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esac |
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fi |
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if [[ $dns_domain_count -gt 0 ]]; then |
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case "${namesrv}" in |
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"netconfig") |
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log "Updating ${rslvcnf} domain search list with: '${dns_domains[*]}'" |
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edit_resolv_conf_search "${dns_domains[@]}" |
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;; |
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"systemd-resolve") |
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params=("$device_index" "$dns_domain_count" "${dns_domains[@]}") |
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log "Calling SetLinkDomains with parameters: '${params[*]}'" |
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# Example: SetLinkDomains 'ia(sb)' amazon.com false example.com false |
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call_systemd_resolved SetLinkDomains 'ia(sb)' "${params[@]}" |
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;; |
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*) |
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;; |
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esac |
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fi |
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test "${namesrv}" = "netconfig" && refresh_nscd || check_systemd_resolve_status |
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} |
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reset_dns() { |
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log "Restoring DNS setting to the state before VPN connection" |
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case "${namesrv}" in |
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"netconfig") |
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${netconf} update -f |
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;; |
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"systemd-resolve") |
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local device_index |
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get_device_index |
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call_systemd_resolved RevertLink i "$device_index" |
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check_systemd_resolve_status |
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;; |
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*) |
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;; |
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esac |
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} |
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# Script args example: tun0 1500 1552 10.0.1.2 255.255.255.224 init |
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main() { |
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local dist |
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declare namesrv |
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declare rslvcnf |
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declare netconf |
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configure_logging |
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get_distribution |
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case "${dist}" in |
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"openSUSE") |
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namesrv="netconfig" |
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rslvcnf="/etc/resolv.conf" |
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netconf="/sbin/netconfig" |
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;; |
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"Ubuntu") |
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namesrv="systemd-resolve" |
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;; |
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*) |
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log "Unsupported distribution: ${dist}" |
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exit 1 |
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;; |
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esac |
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# $script_type is set by OpenVPN |
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log "Executing $script_type script with parameters '$*' under $dist" |
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if [[ $script_type == *up* ]]; then |
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configure_dns |
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elif [[ $script_type == *down* ]]; then |
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reset_dns |
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fi |
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} |
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main "$@" |
