Re: MTU size

On Thu, Nov 21, 2013 at 01:19:54PM +0000, Khapare Joshi wrote:
> ppp: compressor dropped pkt
> mppe_compress[31]: osize too small! (have: 1404 need: 1408)

These two messages are from kernel level ppp driver, not pptpd, so I
have not kept necessary knowledge.  I suggest you look for a kernel
upgrade from your Linux distribution, try the latest stable Linux
kernel (3.12), or check bug trackers for the kernel.

On the face of the meaning of the two messages, during encryption or
compression, the packet grew and would not fit, and was discarded.
This may cause hangs of HTTP get.

> these is only few users who are having issue, I will monitor their
> vpn connection and change the MTU size if needed. But where can I
> make change the MTU in VPN server ? is it in /etc/ppp/ip-up file ?

Yes.

ifconfig ${1} mtu 1200

(you may need to use a different variable name, do some research into
existing scripts)

> And, I see constantly following in the ppp.log files, could you
> please give me some hint or direction on resolving these issue ?
> 
> Nov 17 15:59:58 myvpn pptpd[32735]: MGR: dropped small initial connection
> Nov 19 17:58:50 myvpn pptpd[32735]: MGR: dropped slow initial connection
> Nov 19 19:35:16 myvpn pptpd[32735]: MGR: dropped slow initial connection
> Nov 20 10:57:20 myvpn pptpd[32735]: MGR: dropped small initial connection
> Nov 20 20:45:19 myvpn pptpd[32735]: MGR: dropped small initial connection

These are not an error, and will occur during either:

0.  port probing,

1.  automated robotic attacks on pptpd servers from the internet,

2.  users trying to start tunnel when their network link is saturated, or;

3.  saturation of the server's network link.

> Nov 17 08:32:17 myvpn pppd[27865]: Protocol-Reject for unsupported protocol 0xb5
> Nov 17 08:32:17 myvpn pppd[27865]: rcvd [LCP ProtRej id=0x73 d2 f5 79 0b 84 9c a4 ed 92 9c eb 76 88 e1 ce 0c 93 22 aa d3 03 ec 86 d0 91 3c d2 36 73 ea 37 7b ...]
> Nov 17 08:32:17 myvpn pppd[27865]: Protocol-Reject for unsupported protocol 0xd2f5

Incompatibility in software versions, refusal of the peer to follow
options negotiated, router firmware flaws, or corruption of packets.

> Nov 21 11:05:37 myvpn pppd[15722]: Refusing MPPE stateful mode offered by peer
> Nov 21 11:05:37 myvpn pppd[15722]: MPPE required but peer negotiation failed

Misconfiguration of peer.

These are symptoms, not problems.  I cannot tell if these symptoms
relate to any problem.

-- 
James Cameron
http://quozl.linux.org.au/

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