4

I'm having this weird issue that when I run bridge-start together with openvpn, the service won't start. If I don't let openvpn run bridge-start, and add the necessary interfaces (tap0, br0) manually (or run bridge-start from the shell) and I comment out the "up" directives so that openvpn won't invoke any script, then it works and everything's fine.

Looking into openvpn.log I can see that openvpn invokes the script with several options (/etc/openvpn/bridge-start tap0 1500 1654 init), and I don't really understand why that is. Could this be a problem?

openvpn.log: Tue May 8 20:18:34 2018 us=217442 Current Parameter Settings: Tue May 8 20:18:34 2018 us=217576 config = 'server.conf' Tue May 8 20:18:34 2018 us=217599 mode = 1 Tue May 8 20:18:34 2018 us=217616 persist_config = DISABLED Tue May 8 20:18:34 2018 us=217633 persist_mode = 1 Tue May 8 20:18:34 2018 us=217679 show_ciphers = DISABLED Tue May 8 20:18:34 2018 us=217697 show_digests = DISABLED Tue May 8 20:18:34 2018 us=217713 show_engines = DISABLED Tue May 8 20:18:34 2018 us=217729 genkey = DISABLED Tue May 8 20:18:34 2018 us=217745 key_pass_file = '[UNDEF]' Tue May 8 20:18:34 2018 us=217761 show_tls_ciphers = DISABLED Tue May 8 20:18:34 2018 us=217778 connect_retry_max = 0 Tue May 8 20:18:34 2018 us=217795 Connection profiles [0]: Tue May 8 20:18:34 2018 us=217812 proto = udp Tue May 8 20:18:34 2018 us=217829 local = '[UNDEF]' Tue May 8 20:18:34 2018 us=217845 local_port = '1194' Tue May 8 20:18:34 2018 us=217861 remote = '[UNDEF]' Tue May 8 20:18:34 2018 us=217877 remote_port = '1194' Tue May 8 20:18:34 2018 us=217893 remote_float = DISABLED Tue May 8 20:18:34 2018 us=217909 bind_defined = DISABLED Tue May 8 20:18:34 2018 us=217925 NOTE: --mute triggered... Tue May 8 20:18:34 2018 us=217949 268 variation(s) on previous 20 message(s) suppressed by --mute Tue May 8 20:18:34 2018 us=217974 OpenVPN 2.4.5 x86_64-redhat-linux-gnu [Fedora EPEL patched] [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Mar 1 2018 Tue May 8 20:18:34 2018 us=218005 library versions: OpenSSL 1.0.2k-fips 26 Jan 2017, LZO 2.06 Tue May 8 20:18:34 2018 us=218268 NOTE: when bridging your LAN adapter with the TAP adapter, note that the new bridge adapter will often take on its own IP address that is different from what the LAN adapter was previously set to Tue May 8 20:18:34 2018 us=218467 NOTE: the current --script-security setting may allow this configuration to call user-defined scripts Tue May 8 20:18:34 2018 us=219618 Diffie-Hellman initialized with 2048 bit key Tue May 8 20:18:34 2018 us=221006 Outgoing Control Channel Authentication: Using 512 bit message hash 'SHA512' for HMAC authentication Tue May 8 20:18:34 2018 us=221065 Incoming Control Channel Authentication: Using 512 bit message hash 'SHA512' for HMAC authentication Tue May 8 20:18:34 2018 us=221120 TLS-Auth MTU parms [ L:1654 D:1140 EF:110 EB:0 ET:0 EL:3 ] Tue May 8 20:18:34 2018 us=221554 TUN/TAP device tap0 opened Tue May 8 20:18:34 2018 us=221605 TUN/TAP TX queue length set to 100 Tue May 8 20:18:34 2018 us=221798 /etc/openvpn/bridge-start tap0 1500 1654 init Tue May 8 20:18:34 2018 ERROR: Cannot ioctl TUNSETIFF tap0: Device or resource busy (errno=16) Tue May 8 20:18:34 2018 Exiting due to fatal error RTNETLINK answers: File exists RTNETLINK answers: File exists Tue May 8 20:18:34 2018 us=249873 WARNING: Failed running command (--up/--down): external program exited with error status: 2 Tue May 8 20:18:34 2018 us=249933 Exiting due to fatal error

bridge-start: br="br0" tap="tap0" eth="enp1s0" eth_ip="10.50.0.4" eth_netmask="24" eth_broadcast="10.50.0.255" for t in $tap; do /usr/sbin/openvpn --mktun --dev $t done /usr/sbin/ip link add $br type bridge /usr/sbin/ip link set $eth master $br for t in $tap; do /usr/sbin/ip link set $t master $br done for t in $tap; do /usr/sbin/ip link set $t up /usr/sbin/ip link set $t promisc on done /usr/sbin/ip link set $eth up /usr/sbin/ip link set $eth promisc on /usr/sbin/ip address add $eth_ip/$eth_netmask broadcast $eth_broadcast dev $br

sever conf:

port 1194 proto udp dev tap0 script-security 2 up "/etc/openvpn/bridge-start" down "/etc/openvpn/bridge-stop" tls-server ca ca.crt cert home-vpn.crt key home-vpn.key # This file should be kept secret dh dh2048.pem ifconfig-pool-persist ipp.txt server-bridge 10.50.0.4 255.255.255.0 10.50.0.50 10.50.0.100 push "redirect-gateway def1 bypass-dhcp" push "dhcp-option DNS 1.1.1.1" keepalive 10 120 tls-auth ta.key 0 # This file is secret auth-nocache cipher CAMELLIA-256-CBC auth SHA512 reneg-sec 3600 crl-verify crl.pem tls-version-min 1.2 tls-cipher TLS-DHE-RSA-WITH-AES-256-GCM-SHA384:TLS-DHE-RSA-WITH-AES-256-CBC-SHA256:TLS-DHE-RSA-WITH-AES-128-GCM-SHA256:TLS-DHE-RSA-WITH-AES-128-CBC-SHA256 compress lz4-v2 push "compress lz4-v2" max-clients 50 persist-key persist-tun status openvpn-status.log log-append openvpn.log verb 4 mute 20 explicit-exit-notify

Thanks!

7

This happens if you did not stop the service openvpn and immediately made changes to the configuration file - as a result, after restarting, you still have a lost process with the old interface. It is necessary to stop the openvpn service completely and execute the killall openvpn. - example for Linux Debian:

# /etc/init.d/openvpn stop
# killall openvpn

We check the process in memory:

# ps -A|grep openvpn

if none - start openvpn:

# /etc/init.d/openvpn start

the service should start without errors... :)

  • Hi. Thanks for the answer. I don't even remember if I solved it, to be honest, but after such a long time it's become irrelevant. If I come across this problem again, I'll check it out. – Lethargos Mar 25 '19 at 20:14
  • Actually the problem was not that an openvpn process was still running, but that the bridge-stop script isn't being executed when the vpn service is restarted. If I run it manually, then I can restart the openvpn service without any issues. This is what bridge-stop looks like on my server (sorry for that format, I don't seem to be able to do it right in comments): br="br0" tap="tap0" for t in $tap; do /usr/sbin/openvpn --rmtun --dev $t done /usr/sbin/ip link set $br down /usr/sbin/ip link delete $br type bridge – Lethargos May 30 '19 at 12:07
  • I stopped my service before running the script manually (to test it), and it worked: service openvpn stop, openvpn /etc/openvpn/client.conf. – xinthose Jun 21 '19 at 20:06
  • ps -A | grep openvpn followed by sudo kill -9 <pid> worked for me on Ubuntu 18.04 – aksh1618 Jun 26 '19 at 2:39

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