我有一个 Ubuntu 客户端 OpenVPN，它连接到 Debian OpenVPN 服务器。
有一段时间，我使用 udp 在默认端口 1194 上进行设置，并且我从一个没有过滤连接的网络上进行连接。一切正常。
然后我需要从仅允许端口 80 和 443 的网络连接到它，因此我切换配置以在端口 443 上使用 tcp。它再次运行良好。
现在我在另一个不直接连接到互联网的网络上，我可以使用 http 代理进行访问。所以我将客户端的配置切换为使用 http 代理。从那时起，连接就变得不稳定。它连接到服务器，在很短的一段时间内，连接似乎工作正常（我可以访问互联网上的所有端口，ping 工作正常……）然后突然断开连接。如果我什么都不做，连接就不会断开！它在传递一些数据包后会断开，所以如果我使用 ssh，我还需要一些时间才能断开，但如果我尝试加载网页，它会很快断开。我使用 ubuntu 网络管理器进行配置。路由正常，一切都按预期进行。
编辑 1：我在同一台服务器上还有一个 www 服务器。可能是 OpenVPN 正在接收一些非预期的数据包，但我使用“共享端口”选项，该选项应将所有这些数据包重定向到 www 服务器。
据我了解，TCP 数据包可能会在传输过程中损坏（很可能是通过 http 代理），这会损坏 HMAC。
编辑 2：运行 Zenmap 我可以看到代理是 squid 并且操作系统是 MikroTik。
编辑 3：只是为了好玩，我尝试在第一个 openVPN 上运行另一个 openVPN，第二个配置为使用 UDP。但在重新配置路由并尝试加载网页后，第一个仍然以同样的方式崩溃。
编辑4：我已经在服务器上安装了sslh，作为端口443上的多路复用器，因此当它接收到ssh或openvpn或https的流量时，它会将其重定向到相应的服务，现在我正尝试通过corkscrew通过ssh进行连接，但它也失败了（远程主机关闭连接，服务器实际上接收到连接但将其丢弃）。
编辑 5：我能够通过 ssh 配置服务器，这要感谢我通过 DNS 服务器用碘建立的隧道。这听起来很愚蠢，但实际上它运行良好，非常稳定，唯一的问题是它非常慢，仅对 ssh 来说还算不错。
编辑 6：我可以使用另一个 http 代理，它可以立即工作，而且非常稳定，所以我现在会坚持使用那个。我仍然不知道第一个有什么问题。
客户端上的日志显示：（所有这一切都发生在启用vpn和加载半个网页的不到2分钟内）
NetworkManager[1249]: <info> Starting VPN service 'openvpn'...
NetworkManager[1249]: <info> VPN service 'openvpn' started (org.freedesktop.NetworkManager.openvpn), PID 12305
NetworkManager[1249]: <info> VPN service 'openvpn' appeared; activating connections
NetworkManager[1249]: <info> VPN plugin state changed: starting (3)
NetworkManager[1249]: <info> VPN connection 'domain.com' (Connect) reply received.
nm-openvpn[12311]: OpenVPN 2.2.1 i686-linux-gnu [SSL] [LZO2] [EPOLL] [PKCS11] [eurephia] [MH] [PF_INET6] [IPv6 payload 20110424-2 (2.2RC2)] built on Feb 13 2013
nm-openvpn[12311]: WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
nm-openvpn[12311]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
nm-openvpn[12311]: WARNING: file '/home/user/openvpn-client-conf/ta.key' is group or others accessible
nm-openvpn[12311]: Control Channel Authentication: using '/home/user/openvpn-client-conf/ta.key' as a OpenVPN static key file
nm-openvpn[12311]: LZO compression initialized
nm-openvpn[12311]: Attempting to establish TCP connection with [AF_INET]x.x.x.x:xxxx(http proxy) [nonblock]
nm-openvpn[12311]: TCP connection established with [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: TCPv4_CLIENT link local: [undef]
nm-openvpn[12311]: TCPv4_CLIENT link remote: [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: [domain.com] Peer Connection Initiated with [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: TUN/TAP device tun0 opened
nm-openvpn[12311]: /usr/lib/NetworkManager/nm-openvpn-service-openvpn-helper tun0 1500 1544 10.8.0.2 255.255.255.0 init
NetworkManager[1249]: SCPlugin-Ifupdown: devices added (path: /sys/devices/virtual/net/tun0, iface: tun0)
NetworkManager[1249]: SCPlugin-Ifupdown: device added (path: /sys/devices/virtual/net/tun0, iface: tun0): no ifupdown configuration found.
NetworkManager[1249]: <warn> /sys/devices/virtual/net/tun0: couldn't determine device driver; ignoring...
NetworkManager[1249]: <info> VPN connection 'domain.com' (IP4 Config Get) reply received from old-style plugin.
NetworkManager[1249]: <info> VPN Gateway: x.x.x.x(http proxy)
NetworkManager[1249]: <info> Tunnel Device: tun0
NetworkManager[1249]: <info> IPv4 configuration:
NetworkManager[1249]: <info> Internal Gateway: 10.8.0.1
NetworkManager[1249]: <info> Internal Address: 10.8.0.2
NetworkManager[1249]: <info> Internal Prefix: 24
NetworkManager[1249]: <info> Internal Point-to-Point Address: 0.0.0.0
NetworkManager[1249]: <info> Maximum Segment Size (MSS): 0
NetworkManager[1249]: <info> Forbid Default Route: no
NetworkManager[1249]: <info> Internal DNS: x.x.x.x(dns server)
NetworkManager[1249]: <info> DNS Domain: '(none)'
NetworkManager[1249]: <info> No IPv6 configuration
nm-openvpn[12311]: Initialization Sequence Completed
NetworkManager[1249]: <info> VPN connection 'domain.com' (IP Config Get) complete.
NetworkManager[1249]: <info> Policy set 'domain.com' (tun0) as default for IPv4 routing and DNS.
NetworkManager[1249]: <info> Writing DNS information to /sbin/resolvconf
dbus[975]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
NetworkManager[1249]: <info> VPN plugin state changed: started (4)
dbus[975]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
ntpdate[12428]: step time server 84.104.189.253 offset 1.749623 sec
nm-openvpn[12311]: Authenticate/Decrypt packet error: packet HMAC authentication failed
nm-openvpn[12311]: Fatal decryption error (process_incoming_link), restarting
nm-openvpn[12311]: SIGUSR1[soft,decryption-error] received, process restarting
nm-openvpn[12311]: WARNING: No server certificate verification method has been enabled. See http://openvpn.net/howto.html#mitm for more info.
nm-openvpn[12311]: NOTE: the current --script-security setting may allow this configuration to call user-defined scripts
nm-openvpn[12311]: Re-using SSL/TLS context
nm-openvpn[12311]: LZO compression initialized
nm-openvpn[12311]: Attempting to establish TCP connection with [AF_INET]x.x.x.x:xxxx(http proxy) [nonblock]
nm-openvpn[12311]: TCP connection established with [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: TCPv4_CLIENT link local: [undef]
nm-openvpn[12311]: TCPv4_CLIENT link remote: [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: [domain.com] Peer Connection Initiated with [AF_INET]x.x.x.x:xxxx(http proxy)
nm-openvpn[12311]: Preserving previous TUN/TAP instance: tun0
nm-openvpn[12311]: /usr/lib/NetworkManager/nm-openvpn-service-openvpn-helper tun0 1500 1544 10.8.0.2 255.255.255.0 restart
NetworkManager[1249]: <warn> VPN plugin failed: 2
nm-openvpn[12311]: WARNING: Failed running command (--up/--down): external program exited with error status: 1
nm-openvpn[12311]: Exiting
avahi-daemon[1176]: Withdrawing workstation service for tun0.
NetworkManager[1249]: SCPlugin-Ifupdown: devices removed (path: /sys/devices/virtual/net/tun0, iface: tun0)
NetworkManager[1249]: <warn> VPN plugin failed: 1
NetworkManager[1249]: <info> VPN plugin state changed: stopped (6)
NetworkManager[1249]: <info> VPN plugin state change reason: 0
avahi-daemon[1176]: Withdrawing address record for x.x.x.x(local ip) on eth0.
avahi-daemon[1176]: Leaving mDNS multicast group on interface eth0.IPv4 with address x.x.x.x(local ip).
avahi-daemon[1176]: Joining mDNS multicast group on interface eth0.IPv4 with address x.x.x.x(second local ip).
avahi-daemon[1176]: Withdrawing address record for x.x.x.x(second local ip) on eth0.
avahi-daemon[1176]: Leaving mDNS multicast group on interface eth0.IPv4 with address x.x.x.x(second local ip).
avahi-daemon[1176]: Interface eth0.IPv4 no longer relevant for mDNS.
avahi-daemon[1176]: Joining mDNS multicast group on interface eth0.IPv4 with address x.x.x.x(local ip).
avahi-daemon[1176]: New relevant interface eth0.IPv4 for mDNS.
avahi-daemon[1176]: Registering new address record for x.x.x.x(local ip) on eth0.IPv4.
avahi-daemon[1176]: Registering new address record for x.x.x.x(second local ip) on eth0.IPv4.
NetworkManager[1249]: <info> Policy set 'Wired connection 1' (eth0) as default for IPv4 routing and DNS.
NetworkManager[1249]: <info> Writing DNS information to /sbin/resolvconf
dbus[975]: [system] Activating service name='org.freedesktop.nm_dispatcher' (using servicehelper)
NetworkManager[1249]: <warn> error disconnecting VPN: Could not process the request because no VPN connection was active.
NetworkManager[1249]: <warn> (7) failed to find interface name for index
NetworkManager[1249]: nm_system_iface_flush_routes: assertion `iface != NULL' failed
NetworkManager[1249]: <warn> (7) failed to find interface name for index
dbus[975]: [system] Successfully activated service 'org.freedesktop.nm_dispatcher'
NetworkManager[1249]: <info> VPN service 'openvpn' disappeared