mppe_decompress[1]: osize too small! (have: 1400 need: 1401)

[rusxakep]

mppe_decompress[1]: osize too small! (have: 1400 need: 1401)

This message from dmesg familiar? The PPTP connection works fine using ping, until you try to send or receive a packet near the MTU?

It’s a bug in current versions of the linux kernel’s PPTP support (2.6.20 too). You can update your kernel to the latest (2.6.21?) version, and this problem will go away, or as a temporary solution, you can manually specify a lower MTU in windows. Note that using pppd’s options to achieve this won’t work.

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\NdisWan\Parameters\Protocols\0]
"ProtocolType"=dword:00000800
"PPPProtocolType"=dword:00000021
"TunnelMTU"=dword:00000514

With this simple .reg file, you can lower the windows MTU, and get successful connections. This is especially useful if you can’t upgrade the kernel for one reason or another.