PPTP VPN错误追踪
时间：2010-10-14 来源：劲松
PPTP VPN 错误"buffering packet 88058 (expecting 88057, lost or reordered)"追踪
情况介绍 : 在4M的ADSL线路上,两台LINUX网关建立pptp vpn连接 ,目的在于让其中一台网关负责的内网用户可借用另外一台网关上的光纤线路访问国外.
在VPN连接建立以后,pptp连接经常自动中断,有时候内网用户可以发现网络连接被卡住或者被迫中断的现象.为了解决这个问题查一查出错日志 /var/log/message 可以发现vpn中断前有以下这些与此相关的信息 :
Oct 7 16:22:07 localhost pppd[10693]: CHAP authentication succeeded
Oct 7 16:22:07 localhost pppd[10693]: MPPE 128-bit stateless compression enabled
Oct 7 16:22:07 localhost pppd[10693]: local IP address 192.168.10.x
Oct 7 16:22:07 localhost pppd[10693]: remote IP address 192.168.10.x
Oct 7 16:23:04 localhost pptp[10701]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received.
Oct 7 16:24:04 localhost pptp[10701]: anon log[logecho:pptp_ctrl.c:677]: Echo Reply received.
Oct 7 16:26:04 localhost last message repeated 2 times
Oct 7 16:28:04 localhost last message repeated 2 times
Oct 7 16:30:04 localhost last message repeated 2 times
Oct 7 16:32:04 localhost last message repeated 2 times
Oct 7 16:32:04 localhost pptp[10701]: anon log[logecho:pptp_ctrl.c:679]: no more Echo Reply/Request packets will be reported.
Oct 7 22:23:36 localhost pptp[10694]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 87470 (expecting 87469, lost or reordered)
Oct 7 22:24:37 localhost pptp[10694]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 87517 (expecting 87516, lost or reordered)
Oct 7 22:36:50 localhost pptp[10694]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 88058 (expecting 88057, lost or reordered)
Oct 7 22:36:50 localhost pptp[10694]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 88059 (expecting 88057, lost or reordered)
Oct 7 22:36:50 localhost pptp[10694]: anon log[decaps_gre:pptp_gre.c:414]: buffering packet 88060 (expecting 88057, lost or reordered)
通过TCPDUMP抓包未有看出什么异常.
在PPTP 和 PPTPD 进程都打开DEBUG
1 . 修改/etc/syslog.conf 并重启syslog服务
*.debug;mail.none /var/log/debug
2. 在配置文件或命令行添加debug参数
3. 重新建立pptp连接, 即可以看到/var/log/debug内记录debug信息
在pptpd服务端输出的debug信息:
Oct 8 10:55:56 localhost pptpd[12225]: GRE: accepting packet #12217
Oct 8 10:55:56 localhost pptpd[12225]: GRE: accepting packet #12218
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12220 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12221 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12222 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12223 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12224 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12225 (expecting #12219, lost or reordered)
Oct 8 10:55:56 localhost pptpd[12225]: GRE: buffering packet #12226 (expecting #12219, lost or reordered)
Oct 8 10:55:57 localhost pptpd[12225]: GRE: timeout waiting for 1 packets
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12220 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12221 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12222 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12223 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12224 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12225 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting #12226 from queue
Oct 8 10:55:57 localhost pptpd[12225]: GRE: accepting packet #12227
根据这种错误信息,搜索了internet
http://pptpclient.sourceforge.net/howto-diagnosis.phtml#debug
buffering out-of-order packet
|
Symptom: while running pptp, this message appears, which may or may not be associated with any other problem:
Diagnosis: this is a normal situation. Many network links drop or re-order packets as a normal part of their operation. This message informs you that a packet was lost or re-ordered. The TCP network infrastructure above this level will retransmit the lost data. (out-of-order in this context relates to the sequence of the packets, and should not be confused with the use of the phrase in some locales to warn that public equipment is not operating.) Solution: if the loss is higher than the physical layer should provide, check the physical layer for problems. You can also use the link statistics feature of pptp, see the man page for how to obtain and understand the statistics. |
根据howto的解释这是发生在物理链路层面的故障.属正常现象.数据包不会丢失而是进行重组
现暂时记一笔,待下次的进展.
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