只需在服务器上安装 Ubuntu 13.10，并配置 PPTP VPN。一切正常，直到另一个对等端断开其 VPN 连接。
我可以通过将我的 iPhone 连接到 VPN 来持续模拟这种情况，并且每当我断开 VPN 与 iPhone 的连接时，VPN 就会对所有人来说都断开。
这是服务器的日志文件：
Nov 28 01:14:51 thilak pppd[1620]: pppd 2.4.5 started by thilak, uid 0
Nov 28 01:14:51 thilak pppd[1620]: Using interface ppp0
Nov 28 01:14:51 thilak pppd[1620]: Connect: ppp0 <--> /dev/pts/2
Nov 28 01:14:51 thilak pptpd[1619]: GRE: Bad checksum from pppd.
Nov 28 01:14:54 thilak pppd[1620]: peer from calling number 106.51.51.20 authorized
Nov 28 01:14:55 thilak pppd[1620]: MPPE 128-bit stateless compression enabled
Nov 28 01:14:55 thilak pppd[1620]: Cannot determine ethernet address for proxy ARP
Nov 28 01:14:55 thilak pppd[1620]: local IP address 198.211.113.34
Nov 28 01:14:55 thilak pppd[1620]: remote IP address 10.10.0.2
Nov 28 01:17:01 thilak CRON[1648]: (root) CMD ( cd / && run-parts --report /etc/cron.hourly)
Nov 28 01:26:29 thilak pptpd[1677]: CTRL: Client 106.51.51.20 control connection started
Nov 28 01:26:29 thilak pptpd[1677]: CTRL: Starting call (launching pppd, opening GRE)
Nov 28 01:26:29 thilak pppd[1678]: Plugin /usr/lib/pptpd/pptpd-logwtmp.so loaded.
Nov 28 01:26:29 thilak pppd[1678]: pppd 2.4.5 started by thilak, uid 0
Nov 28 01:26:29 thilak pppd[1678]: Using interface ppp1
Nov 28 01:26:29 thilak pppd[1678]: Connect: ppp1 <--> /dev/pts/3
Nov 28 01:26:29 thilak pptpd[1677]: GRE: Bad checksum from pppd.
Nov 28 01:26:32 thilak pppd[1678]: peer from calling number 106.51.51.20 authorized
Nov 28 01:26:33 thilak pppd[1678]: MPPE 128-bit stateless compression enabled
Nov 28 01:26:33 thilak pppd[1678]: Cannot determine ethernet address for proxy ARP
Nov 28 01:26:33 thilak pppd[1678]: local IP address 198.211.113.34
Nov 28 01:26:33 thilak pppd[1678]: remote IP address 10.10.0.4
Nov 28 01:27:14 thilak pppd[1678]: LCP terminated by peer (MPPE disabled)
Nov 28 01:27:14 thilak pppd[1678]: Connect time 0.7 minutes.
Nov 28 01:27:14 thilak pppd[1678]: Sent 44172 bytes, received 16425 bytes.
Nov 28 01:27:14 thilak pptpd[1677]: CTRL: EOF or bad error reading ctrl packet length.
Nov 28 01:27:14 thilak pptpd[1677]: CTRL: couldn't read packet header (exit)
Nov 28 01:27:14 thilak pptpd[1677]: CTRL: CTRL read failed
Nov 28 01:27:14 thilak pptpd[1677]: CTRL: Reaping child PPP[1678]
Nov 28 01:27:14 thilak pppd[1678]: Hangup (SIGHUP)
Nov 28 01:27:14 thilak pppd[1678]: Modem hangup
Nov 28 01:27:14 thilak pppd[1678]: Connection terminated.
Nov 28 01:27:14 thilak pptpd[1619]: GRE: read(fd=7,buffer=7f38314b8460,len=8260) from network failed: status = -1 error = Protocol not available
Nov 28 01:27:14 thilak pptpd[1619]: CTRL: GRE read or PTY write failed (gre,pty)=(7,6)
Nov 28 01:27:14 thilak pptpd[1619]: CTRL: Reaping child PPP[1620]
Nov 28 01:27:14 thilak pppd[1620]: Hangup (SIGHUP)
Nov 28 01:27:14 thilak pppd[1620]: Modem hangup
Nov 28 01:27:14 thilak pppd[1620]: Connect time 12.4 minutes.
Nov 28 01:27:14 thilak pppd[1620]: Sent 19431067 bytes, received 7005368 bytes.
Nov 28 01:27:14 thilak pppd[1620]: MPPE disabled
Nov 28 01:27:14 thilak pppd[1620]: Connection terminated.
Nov 28 01:27:14 thilak pppd[1678]: Exit.
Nov 28 01:27:14 thilak pptpd[1677]: CTRL: Client 106.51.51.20 control connection finished
Nov 28 01:27:14 thilak pppd[1620]: Exit.
Nov 28 01:27:14 thilak pptpd[1619]: CTRL:
知道发生什么事了吗？
答案1
您应该尝试为连接设置不同的本地 IP，如下所示：
localip 172.20.1.1-100
remoteip 172.20.1.101-200
另外，设置你的文件墙规则：
# accept incoming control connections via conntrack
iptables -A INPUT -p tcp --dport 1723 -m conntrack --ctstate NEW -j ACCEPT
# accept GRE protocol
iptables -A INPUT -p gre -j ACCEPT
# allow packet forwarding from VPN subnet with TCP max segment size tune
iptables -A FORWARD -p tcp --tcp-flags SYN,RST SYN -s 172.20.1.0/24 -j TCPMSS --clamp-mss-to-pmtu
请发布您的 pptpd.conf 和 pptpd-options 文件