Re: [lwip-users] lwip2.0.2 l2tp question

[Sylvain Rochet]

Hi,

On Thu, Jul 06, 2017 at 11:10:41PM -0700, odobryabov wrote:
> Yes, you are right, these are just echo requests and replies:
> 
> ppp phase changed[1]: phase=10
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP EchoReq id=0x1 magic=0x5e33e1ff]
> sent [LCP EchoRep id=0x1 magic=0xb4b7bbcf]
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP EchoReq id=0x2 magic=0x5e33e1ff]
> sent [LCP EchoRep id=0x2 magic=0xb4b7bbcf]
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP EchoReq id=0x3 magic=0x5e33e1ff]
> sent [LCP EchoRep id=0x3 magic=0xb4b7bbcf]
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP EchoReq id=0x4 magic=0x5e33e1ff]
> sent [LCP EchoRep id=0x4 magic=0xb4b7bbcf]
> .....
> pppol2tp: input packet, len=20, tunnel=21944, session=0, ns=2, nr=4
> pppol2tp: input packet, len=20, tunnel=21944, session=0, ns=2, nr=4

That's a clue, L2TP session is restarted here in the middle of perfectly 
working LCP probes.


> .....
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP EchoReq id=0x1c magic=0x5e33e1ff]
> sent [LCP EchoRep id=0x1c magic=0xb4b7bbcf]
> pppol2tp: input packet, len=45, tunnel=21944, session=0, ns=3, nr=4
> pppol2tp: input packet, len=0, tunnel=21944, session=8324, ns=0, nr=0
> rcvd [LCP TermReq id=0x3 "User request"]
> LCP terminated by peer (User request)
> 
> May be the problem is in that timeout message:
> 
> pppol2tp: input packet, len=0, tunnel=47089, session=35933, ns=0, nr=0 
> rcvd [LCP ConfReq id=0x2 <auth chap MS-v2> <magic 0xd9bb4bcc>] 
> sent [LCP ConfAck id=0x2 <auth chap MS-v2> <magic 0xd9bb4bcc>] 
> pppol2tp: timeout 
> sent [LCP ConfReq id=0x5 <mru 1450> <magic 0xdadcdfcd>] 
> pppol2tp: input packet, len=0, tunnel=47089, session=35933, ns=0, nr=0 
> rcvd [LCP ConfAck id=0x5 <mru 1450> <magic 0xdadcdfcd>] 
> netif_set_mtu[1]: mtu=1450 
> ppp_send_config[1] 
> ppp_recv_config[1]
> 

> But if LwIP reached running phase, doesn't it mean l2tp initialisation was
> clear (even with that timeout)?

That's strange indeed, it looks like your L2TP server is not sending a 
packet acknowledging the ICCN packet (any packet with peer nr greater 
than our ns).

Could you try replacing

      if (l2tp->iccn_retried >= PPPOL2TP_MAXICCN) {
        pppol2tp_abort_connect(l2tp);
        return;
      }

by

      if (l2tp->iccn_retried >= PPPOL2TP_MAXICCN) {
        PPPDEBUG(LOG_DEBUG, ("pppol2tp: reached max ICCN"));
        l2tp->phase = PPPOL2TP_STATE_DATA;
        return;
      }


Sylvain

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