1

I want to set up an OpenVPN Server on a CentOS 7 server. From my ISP, I only have public IPv6 address, the IPv4 is NAT-ed at the ISP, so I decided to configure my VPN to be based on IPv6.

I followed this tutorial, which means I used the downloaded script to set things up for me with IPv4, then alter the config to be IPv6 compatible. The result is:

port 1194
proto udp
dev tun
sndbuf 0
rcvbuf 0
ca ca.crt
cert server.crt
key server.key
dh dh.pem
auth SHA512
tls-auth ta.key 0
topology subnet
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
push "redirect-gateway def1 bypass-dhcp"
push "dhcp-option DNS 192.168.10.1"
keepalive 10 120
cipher AES-256-CBC
user nobody
group nobody
persist-key
persist-tun
status openvpn-status.log
verb 4
crl-verify crl.pem

log-append /var/log/openvpn.log

server-ipv6 2001:db8:0:123::/64
tun-ipv6
push tun-ipv6
ifconfig-ipv6 2001:db8:0:123::1 2001:db8:0:123::2
push "route-ipv6 2001:db8:0:abc::/64"
push "route-ipv6 2000::/3"

The server started up successfully, so I downloaded the client.ovpn file on the client, but I get Thu Jan 10 23:53:23 2019 read UDP: Unknown error (code=10054), which should mean that it failed to connect to the host, but I'm already connected to the target machine with SSH. I also have the port 1194 open on the firewall.

server log:

Thu Jan 10 22:55:02 2019 us=932367 event_wait : Interrupted system call (code=4)
Thu Jan 10 22:55:02 2019 us=933688 TCP/UDP: Closing socket
Thu Jan 10 22:55:02 2019 us=933822 Closing TUN/TAP interface
Thu Jan 10 22:55:02 2019 us=933907 /sbin/ip addr del dev tun0 10.8.0.1/24
RTNETLINK answers: Operation not permitted
Thu Jan 10 22:55:02 2019 us=943788 Linux ip addr del failed: external program exited with error status: 2
Thu Jan 10 22:55:02 2019 us=943944 /sbin/ip -6 addr del 2001:db8:0:123::1/64 dev tun0
RTNETLINK answers: Operation not permitted
Thu Jan 10 22:55:02 2019 us=948530 Linux ip -6 addr del failed: external program exited with error status: 2
Thu Jan 10 22:55:02 2019 us=963888 SIGTERM[hard,] received, process exiting
Thu Jan 10 22:55:03 2019 Note: option tun-ipv6 is ignored because modern operating systems do not need special IPv6 tun handling anymore.
Thu Jan 10 22:55:03 2019 us=23634 Current Parameter Settings:
Thu Jan 10 22:55:03 2019 us=23684   config = 'server.conf'
Thu Jan 10 22:55:03 2019 us=23720   mode = 1
Thu Jan 10 22:55:03 2019 us=23754   persist_config = DISABLED
Thu Jan 10 22:55:03 2019 us=23788   persist_mode = 1
Thu Jan 10 22:55:03 2019 us=23822   show_ciphers = DISABLED
Thu Jan 10 22:55:03 2019 us=23855   show_digests = DISABLED
Thu Jan 10 22:55:03 2019 us=23889   show_engines = DISABLED
Thu Jan 10 22:55:03 2019 us=23922   genkey = DISABLED
Thu Jan 10 22:55:03 2019 us=23955   key_pass_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=23989   show_tls_ciphers = DISABLED
Thu Jan 10 22:55:03 2019 us=24022   connect_retry_max = 0
Thu Jan 10 22:55:03 2019 us=24056 Connection profiles [0]:
Thu Jan 10 22:55:03 2019 us=24092   proto = udp
Thu Jan 10 22:55:03 2019 us=24126   local = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=24160   local_port = '1194'
Thu Jan 10 22:55:03 2019 us=24193   remote = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=24227   remote_port = '1194'
Thu Jan 10 22:55:03 2019 us=24279   remote_float = DISABLED
Thu Jan 10 22:55:03 2019 us=24313   bind_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=24346   bind_local = ENABLED
Thu Jan 10 22:55:03 2019 us=24380   bind_ipv6_only = DISABLED
Thu Jan 10 22:55:03 2019 us=24413   connect_retry_seconds = 5
Thu Jan 10 22:55:03 2019 us=24447   connect_timeout = 120
Thu Jan 10 22:55:03 2019 us=24482   socks_proxy_server = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=24515   socks_proxy_port = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=24549   tun_mtu = 1500
Thu Jan 10 22:55:03 2019 us=24583   tun_mtu_defined = ENABLED
Thu Jan 10 22:55:03 2019 us=24616   link_mtu = 1500
Thu Jan 10 22:55:03 2019 us=24650   link_mtu_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=24683   tun_mtu_extra = 0
Thu Jan 10 22:55:03 2019 us=24717   tun_mtu_extra_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=24750   mtu_discover_type = -1
Thu Jan 10 22:55:03 2019 us=24784   fragment = 0
Thu Jan 10 22:55:03 2019 us=24818   mssfix = 1450
Thu Jan 10 22:55:03 2019 us=24854   explicit_exit_notification = 0
Thu Jan 10 22:55:03 2019 us=24887 Connection profiles END
Thu Jan 10 22:55:03 2019 us=24920   remote_random = DISABLED
Thu Jan 10 22:55:03 2019 us=24956   ipchange = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=24990   dev = 'tun'
Thu Jan 10 22:55:03 2019 us=25023   dev_type = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=25057   dev_node = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=25090   lladdr = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=25124   topology = 3
Thu Jan 10 22:55:03 2019 us=25157   ifconfig_local = '10.8.0.1'
Thu Jan 10 22:55:03 2019 us=25193   ifconfig_remote_netmask = '255.255.255.0'
Thu Jan 10 22:55:03 2019 us=25227   ifconfig_noexec = DISABLED
Thu Jan 10 22:55:03 2019 us=25274   ifconfig_nowarn = DISABLED
Thu Jan 10 22:55:03 2019 us=25307   ifconfig_ipv6_local = '2001:db8:0:123::1'
Thu Jan 10 22:55:03 2019 us=25341   ifconfig_ipv6_netbits = 64
Thu Jan 10 22:55:03 2019 us=25377   ifconfig_ipv6_remote = '2001:db8:0:123::2'
Thu Jan 10 22:55:03 2019 us=25411   shaper = 0
Thu Jan 10 22:55:03 2019 us=25445   mtu_test = 0
Thu Jan 10 22:55:03 2019 us=25478   mlock = DISABLED
Thu Jan 10 22:55:03 2019 us=25512   keepalive_ping = 10
Thu Jan 10 22:55:03 2019 us=25547   keepalive_timeout = 120
Thu Jan 10 22:55:03 2019 us=25581   inactivity_timeout = 0
Thu Jan 10 22:55:03 2019 us=25616   ping_send_timeout = 10
Thu Jan 10 22:55:03 2019 us=25650   ping_rec_timeout = 240
Thu Jan 10 22:55:03 2019 us=25685   ping_rec_timeout_action = 2
Thu Jan 10 22:55:03 2019 us=25720   ping_timer_remote = DISABLED
Thu Jan 10 22:55:03 2019 us=25755   remap_sigusr1 = 0
Thu Jan 10 22:55:03 2019 us=25789   persist_tun = ENABLED
Thu Jan 10 22:55:03 2019 us=25825   persist_local_ip = DISABLED
Thu Jan 10 22:55:03 2019 us=25861   persist_remote_ip = DISABLED
Thu Jan 10 22:55:03 2019 us=25894   persist_key = ENABLED
Thu Jan 10 22:55:03 2019 us=25940   passtos = DISABLED
Thu Jan 10 22:55:03 2019 us=25975   resolve_retry_seconds = 1000000000
Thu Jan 10 22:55:03 2019 us=26009   resolve_in_advance = DISABLED
Thu Jan 10 22:55:03 2019 us=26043   username = 'nobody'
Thu Jan 10 22:55:03 2019 us=26078   groupname = 'nobody'
Thu Jan 10 22:55:03 2019 us=26114   chroot_dir = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=26150   cd_dir = '/etc/openvpn/'
Thu Jan 10 22:55:03 2019 us=26183   selinux_context = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=26219   writepid = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=26278   up_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=26313   down_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=26347   down_pre = DISABLED
Thu Jan 10 22:55:03 2019 us=26381   up_restart = DISABLED
Thu Jan 10 22:55:03 2019 us=26415   up_delay = DISABLED
Thu Jan 10 22:55:03 2019 us=26450   daemon = DISABLED
Thu Jan 10 22:55:03 2019 us=26484   inetd = 0
Thu Jan 10 22:55:03 2019 us=26519   log = ENABLED
Thu Jan 10 22:55:03 2019 us=26555   suppress_timestamps = DISABLED
Thu Jan 10 22:55:03 2019 us=26591   machine_readable_output = DISABLED
Thu Jan 10 22:55:03 2019 us=26624   nice = 0
Thu Jan 10 22:55:03 2019 us=26660   verbosity = 4
Thu Jan 10 22:55:03 2019 us=26696   mute = 0
Thu Jan 10 22:55:03 2019 us=26729   gremlin = 0
Thu Jan 10 22:55:03 2019 us=26762   status_file = 'openvpn-status.log'
Thu Jan 10 22:55:03 2019 us=26796   status_file_version = 1
Thu Jan 10 22:55:03 2019 us=26829   status_file_update_freq = 60
Thu Jan 10 22:55:03 2019 us=26863   occ = ENABLED
Thu Jan 10 22:55:03 2019 us=26896   rcvbuf = 0
Thu Jan 10 22:55:03 2019 us=26929   sndbuf = 0
Thu Jan 10 22:55:03 2019 us=26962   mark = 0
Thu Jan 10 22:55:03 2019 us=26996   sockflags = 0
Thu Jan 10 22:55:03 2019 us=27029   fast_io = DISABLED
Thu Jan 10 22:55:03 2019 us=27062   comp.alg = 0
Thu Jan 10 22:55:03 2019 us=27098   comp.flags = 0
Thu Jan 10 22:55:03 2019 us=27132   route_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27166   route_default_gateway = '10.8.0.2'
Thu Jan 10 22:55:03 2019 us=27200   route_default_metric = 0
Thu Jan 10 22:55:03 2019 us=27234   route_noexec = DISABLED
Thu Jan 10 22:55:03 2019 us=27295   route_delay = 0
Thu Jan 10 22:55:03 2019 us=27330   route_delay_window = 30
Thu Jan 10 22:55:03 2019 us=27366   route_delay_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=27402   route_nopull = DISABLED
Thu Jan 10 22:55:03 2019 us=27438   route_gateway_via_dhcp = DISABLED
Thu Jan 10 22:55:03 2019 us=27472   allow_pull_fqdn = DISABLED
Thu Jan 10 22:55:03 2019 us=27507   management_addr = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27544   management_port = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27580   management_user_pass = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27614   management_log_history_cache = 250
Thu Jan 10 22:55:03 2019 us=27651   management_echo_buffer_size = 100
Thu Jan 10 22:55:03 2019 us=27685   management_write_peer_info_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27721   management_client_user = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27755   management_client_group = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27789   management_flags = 0
Thu Jan 10 22:55:03 2019 us=27826   shared_secret_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=27860   key_direction = 0
Thu Jan 10 22:55:03 2019 us=27896   ciphername = 'AES-256-CBC'
Thu Jan 10 22:55:03 2019 us=27930   ncp_enabled = ENABLED
Thu Jan 10 22:55:03 2019 us=27964   ncp_ciphers = 'AES-256-GCM:AES-128-GCM'
Thu Jan 10 22:55:03 2019 us=27998   authname = 'SHA512'
Thu Jan 10 22:55:03 2019 us=28034   prng_hash = 'SHA1'
Thu Jan 10 22:55:03 2019 us=28068   prng_nonce_secret_len = 16
Thu Jan 10 22:55:03 2019 us=28105   keysize = 0
Thu Jan 10 22:55:03 2019 us=28138   engine = DISABLED
Thu Jan 10 22:55:03 2019 us=28174   replay = ENABLED
Thu Jan 10 22:55:03 2019 us=28210   mute_replay_warnings = DISABLED
Thu Jan 10 22:55:03 2019 us=28260   replay_window = 64
Thu Jan 10 22:55:03 2019 us=28332   replay_time = 15
Thu Jan 10 22:55:03 2019 us=28377   packet_id_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=28422   use_iv = ENABLED
Thu Jan 10 22:55:03 2019 us=28476   test_crypto = DISABLED
Thu Jan 10 22:55:03 2019 us=28519   tls_server = ENABLED
Thu Jan 10 22:55:03 2019 us=28561   tls_client = DISABLED
Thu Jan 10 22:55:03 2019 us=28604   key_method = 2
Thu Jan 10 22:55:03 2019 us=28646   ca_file = 'ca.crt'
Thu Jan 10 22:55:03 2019 us=28689   ca_path = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=28731   dh_file = 'dh.pem'
Thu Jan 10 22:55:03 2019 us=28776   cert_file = 'server.crt'
Thu Jan 10 22:55:03 2019 us=28819   extra_certs_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=28864   priv_key_file = 'server.key'
Thu Jan 10 22:55:03 2019 us=28910   pkcs12_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=28952   cipher_list = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=28995   tls_cert_profile = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=29037   tls_verify = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=29080   tls_export_cert = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=29123   verify_x509_type = 0
Thu Jan 10 22:55:03 2019 us=29166   verify_x509_name = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=29208   crl_file = 'crl.pem'
Thu Jan 10 22:55:03 2019 us=29267   ns_cert_type = 0
Thu Jan 10 22:55:03 2019 us=29319   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29362   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29405   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29448   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29491   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29533   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29576   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29619   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29661   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29704   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29747   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29789   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29832   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29875   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29917   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=29960   remote_cert_ku[i] = 0
Thu Jan 10 22:55:03 2019 us=30005   remote_cert_eku = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=30048   ssl_flags = 0
Thu Jan 10 22:55:03 2019 us=30091   tls_timeout = 2
Thu Jan 10 22:55:03 2019 us=30134   renegotiate_bytes = -1
Thu Jan 10 22:55:03 2019 us=30177   renegotiate_packets = 0
Thu Jan 10 22:55:03 2019 us=30220   renegotiate_seconds = 3600
Thu Jan 10 22:55:03 2019 us=30288   handshake_window = 60
Thu Jan 10 22:55:03 2019 us=30332   transition_window = 3600
Thu Jan 10 22:55:03 2019 us=30375   single_session = DISABLED
Thu Jan 10 22:55:03 2019 us=30417   push_peer_info = DISABLED
Thu Jan 10 22:55:03 2019 us=30460   tls_exit = DISABLED
Thu Jan 10 22:55:03 2019 us=30502   tls_auth_file = 'ta.key'
Thu Jan 10 22:55:03 2019 us=30545   tls_crypt_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=30588   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30631   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30673   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30716   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30759   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30801   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30844   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30889   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30931   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=30974   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31016   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31059   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31102   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31144   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31187   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31229   pkcs11_protected_authentication = DISABLED
Thu Jan 10 22:55:03 2019 us=31299   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31344   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31387   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31431   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31474   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31517   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31560   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31603   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31646   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31689   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31733   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31776   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31819   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31862   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31905   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31948   pkcs11_private_mode = 00000000
Thu Jan 10 22:55:03 2019 us=31993   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32035   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32078   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32120   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32163   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32205   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32260   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32309   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32351   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32394   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32437   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32479   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32522   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32565   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32607   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32650   pkcs11_cert_private = DISABLED
Thu Jan 10 22:55:03 2019 us=32703   pkcs11_pin_cache_period = -1
Thu Jan 10 22:55:03 2019 us=32746   pkcs11_id = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=32789   pkcs11_id_management = DISABLED
Thu Jan 10 22:55:03 2019 us=32837   server_network = 10.8.0.0
Thu Jan 10 22:55:03 2019 us=32883   server_netmask = 255.255.255.0
Thu Jan 10 22:55:03 2019 us=32931   server_network_ipv6 = 2001:db8:0:123::
Thu Jan 10 22:55:03 2019 us=32975   server_netbits_ipv6 = 64
Thu Jan 10 22:55:03 2019 us=33021   server_bridge_ip = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=33067   server_bridge_netmask = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=33114   server_bridge_pool_start = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=33160   server_bridge_pool_end = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=33203   push_entry = 'redirect-gateway def1 bypass-dhcp'
Thu Jan 10 22:55:03 2019 us=33258   push_entry = 'dhcp-option DNS 192.168.10.1'
Thu Jan 10 22:55:03 2019 us=33308   push_entry = 'tun-ipv6'
Thu Jan 10 22:55:03 2019 us=33351   push_entry = 'route-ipv6 2001:db8:0:abc::/64'
Thu Jan 10 22:55:03 2019 us=33393   push_entry = 'route-ipv6 2000::/3'
Thu Jan 10 22:55:03 2019 us=33436   push_entry = 'tun-ipv6'
Thu Jan 10 22:55:03 2019 us=33479   push_entry = 'route-gateway 10.8.0.1'
Thu Jan 10 22:55:03 2019 us=33521   push_entry = 'topology subnet'
Thu Jan 10 22:55:03 2019 us=33564   push_entry = 'ping 10'
Thu Jan 10 22:55:03 2019 us=33606   push_entry = 'ping-restart 120'
Thu Jan 10 22:55:03 2019 us=33649   ifconfig_pool_defined = ENABLED
Thu Jan 10 22:55:03 2019 us=33697   ifconfig_pool_start = 10.8.0.2
Thu Jan 10 22:55:03 2019 us=33742   ifconfig_pool_end = 10.8.0.253
Thu Jan 10 22:55:03 2019 us=33787   ifconfig_pool_netmask = 255.255.255.0
Thu Jan 10 22:55:03 2019 us=33830   ifconfig_pool_persist_filename = 'ipp.txt'
Thu Jan 10 22:55:03 2019 us=33873   ifconfig_pool_persist_refresh_freq = 600
Thu Jan 10 22:55:03 2019 us=33919   ifconfig_ipv6_pool_defined = ENABLED
Thu Jan 10 22:55:03 2019 us=33976   ifconfig_ipv6_pool_base = 2001:db8:0:123::1000
Thu Jan 10 22:55:03 2019 us=34020   ifconfig_ipv6_pool_netbits = 64
Thu Jan 10 22:55:03 2019 us=34065   n_bcast_buf = 256
Thu Jan 10 22:55:03 2019 us=34107   tcp_queue_limit = 64
Thu Jan 10 22:55:03 2019 us=34153   real_hash_size = 256
Thu Jan 10 22:55:03 2019 us=34196   virtual_hash_size = 256
Thu Jan 10 22:55:03 2019 us=34255   client_connect_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=34307   learn_address_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=34352   client_disconnect_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=34395   client_config_dir = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=34440   ccd_exclusive = DISABLED
Thu Jan 10 22:55:03 2019 us=34485   tmp_dir = '/tmp'
Thu Jan 10 22:55:03 2019 us=34530   push_ifconfig_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=34577   push_ifconfig_local = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=34622   push_ifconfig_remote_netmask = 0.0.0.0
Thu Jan 10 22:55:03 2019 us=34668   push_ifconfig_ipv6_defined = DISABLED
Thu Jan 10 22:55:03 2019 us=34715   push_ifconfig_ipv6_local = ::/0
Thu Jan 10 22:55:03 2019 us=34760   push_ifconfig_ipv6_remote = ::
Thu Jan 10 22:55:03 2019 us=34802   enable_c2c = DISABLED
Thu Jan 10 22:55:03 2019 us=34845   duplicate_cn = DISABLED
Thu Jan 10 22:55:03 2019 us=34887   cf_max = 0
Thu Jan 10 22:55:03 2019 us=34931   cf_per = 0
Thu Jan 10 22:55:03 2019 us=34974   max_clients = 1024
Thu Jan 10 22:55:03 2019 us=35017   max_routes_per_client = 256
Thu Jan 10 22:55:03 2019 us=35060   auth_user_pass_verify_script = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=35102   auth_user_pass_verify_script_via_file = DISABLED
Thu Jan 10 22:55:03 2019 us=35145   auth_token_generate = DISABLED
Thu Jan 10 22:55:03 2019 us=35188   auth_token_lifetime = 0
Thu Jan 10 22:55:03 2019 us=35231   port_share_host = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=35291   port_share_port = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=35334   client = DISABLED
Thu Jan 10 22:55:03 2019 us=35376   pull = DISABLED
Thu Jan 10 22:55:03 2019 us=35419   auth_user_pass_file = '[UNDEF]'
Thu Jan 10 22:55:03 2019 us=35475 OpenVPN 2.4.6 x86_64-redhat-linux-gnu [Fedora EPEL patched] [SSL (OpenSSL)] [LZO] [LZ4] [EPOLL] [PKCS11] [MH/PKTINFO] [AEAD] built on Apr 26 2018
Thu Jan 10 22:55:03 2019 us=35542 library versions: OpenSSL 1.0.2k-fips  26 Jan 2017, LZO 2.06
Thu Jan 10 22:55:03 2019 us=40832 NOTE: your local LAN uses the extremely common subnet address 192.168.0.x or 192.168.1.x.  Be aware that this might create routing conflicts if you connect to the VPN server from public locations such as internet cafes that use the same subnet.
Thu Jan 10 22:55:03 2019 us=43372 Diffie-Hellman initialized with 2048 bit key
Thu Jan 10 22:55:03 2019 us=45102 Outgoing Control Channel Authentication: Using 512 bit message hash 'SHA512' for HMAC authentication
Thu Jan 10 22:55:03 2019 us=45176 Incoming Control Channel Authentication: Using 512 bit message hash 'SHA512' for HMAC authentication
Thu Jan 10 22:55:03 2019 us=45273 TLS-Auth MTU parms [ L:1621 D:1140 EF:110 EB:0 ET:0 EL:3 ]
Thu Jan 10 22:55:03 2019 us=51203 TUN/TAP device tun0 opened
Thu Jan 10 22:55:03 2019 us=51391 TUN/TAP TX queue length set to 100
Thu Jan 10 22:55:03 2019 us=51480 do_ifconfig, tt->did_ifconfig_ipv6_setup=1
Thu Jan 10 22:55:03 2019 us=51564 /sbin/ip link set dev tun0 up mtu 1500
Thu Jan 10 22:55:03 2019 us=57581 /sbin/ip addr add dev tun0 10.8.0.1/24 broadcast 10.8.0.255
Thu Jan 10 22:55:03 2019 us=62748 /sbin/ip -6 addr add 2001:db8:0:123::1/64 dev tun0
Thu Jan 10 22:55:03 2019 us=69805 Data Channel MTU parms [ L:1621 D:1450 EF:121 EB:406 ET:0 EL:3 ]
Thu Jan 10 22:55:03 2019 us=71518 Could not determine IPv4/IPv6 protocol. Using AF_INET
Thu Jan 10 22:55:03 2019 us=71646 Socket Buffers: R=[212992->212992] S=[212992->212992]
Thu Jan 10 22:55:03 2019 us=71934 UDPv4 link local (bound): [AF_INET][undef]:1194
Thu Jan 10 22:55:03 2019 us=71981 UDPv4 link remote: [AF_UNSPEC]
Thu Jan 10 22:55:03 2019 us=72044 GID set to nobody
Thu Jan 10 22:55:03 2019 us=72105 UID set to nobody
Thu Jan 10 22:55:03 2019 us=72209 MULTI: multi_init called, r=256 v=256
Thu Jan 10 22:55:03 2019 us=72335 IFCONFIG POOL IPv6: (IPv4) size=252, size_ipv6=65536, netbits=64, base_ipv6=2001:db8:0:123::1000
Thu Jan 10 22:55:03 2019 us=72405 IFCONFIG POOL: base=10.8.0.2 size=252, ipv6=1
Thu Jan 10 22:55:03 2019 us=72477 IFCONFIG POOL LIST
Thu Jan 10 22:55:03 2019 us=72676 Initialization Sequence Completed

client log (SO wouldn't let me paste it in here)

Anyone has any input on how to solve this issue?

  • 1
    What version of Windows are you using? Is it up to date? – Michael Hampton Jan 10 at 23:14
  • Perform a tcpdump on the server, do you see the incoming udp/1194 packets reaching the server? – Zoredache Jan 10 at 23:15
  • @MichaelHampton my windows is updated regularly, I'm not 100% sure its the most up-to-date tho, but 99% there – László Stahorszki Jan 10 at 23:31
  • @Zoredache I get this from tcpdump: 23:29:45.906664 IP6 2a02:ab88:5081:7e00:34ba:6231:6db2:3790.50258 > ropi.centos.openvpn: UDP, length 86 when I try to connect, which is probably a yes – László Stahorszki Jan 10 at 23:32
  • Again, what version of Windows are you running? – Michael Hampton Jan 11 at 0:59
0

I am running Windows 10 and had the same issue with

Error when connect : read UDP: Unknown error (code=10054)

Additionally, I noticed this line in the log:

preserving recently used remote address 127.42.0.1

This is the wrong IP. A quick dig @8.8.8.8 my.serverdomain.com returned the same wrong address as using the default DNS server.

It turns out that the issue was caused by malwarebytes. It redirected my requests to the loopback interface because it sneakily activated all the premium protections as a trial. Deactivating all of them - as I wanted them deactivated anyways - fixes that issue.

-1

My mistake was the fact that I mixed up the IPv6, and IPv4 configs.

While I had a (probably) correct IPv4 config for OpenVPN, I tried connecting via IPv6, which obviously, because the udp protocol, didn't work.

When I replaced the correct protocol and some other config parameters, it all went right. Thanks for the help

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