[Openvpn-devel] mppe loses last 3 bytes of ping.

[Denis V. <vd...@po...>]

Hello.

Just started to play with pptp under Linux.
Everything looks ok except mppe.

mppe encrypted ping -c1:

ping source side:
# tcpdump -nlippp0 -s0 -vvv -xX
tcpdump: listening on ppp0, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
23:15:07.968863 IP (tos 0x0, ttl  64, id 0, offset 0, flags [DF], length: 84) 1.1.6.2 > 1.1.6.1: icmp 64: echo request seq 1
0x0000   0004 0200 0000 0000 0000 0000 0000 0800        ................
0x0010   4500 0054 0000 4000 4001 2ca5 0101 0602        E..T..@.@.,.....
0x0020   0101 0601 0800 1f1f a613 0001 4bc0 ab40        ............K..@
0x0030   42c8 0e00 0809 0a0b 0c0d 0e0f 1011 1213        B...............
0x0040   1415 1617 1819 1a1b 1c1d 1e1f 2021 2223        .............!"#
0x0050   2425 2627 2829 2a2b 2c2d 2e2f 3031 3233        $%&'()*+,-./0123
0x0060   3435 3637                                      4567

ping target side:
# tcpdump -nlippp0 -s0 -vvv -xX
tcpdump: listening on ppp0, link-type LINUX_SLL (Linux cooked), capture size 65535 bytes
23:15:01.521393 IP truncated-ip - 3 bytes missing! (tos 0x0, ttl  64, id 0, offset 0, flags [DF], length: 84) 1.1.6.2 > 1.1.6.1: icmp 64: echo
0x0000   0000 0200 0000 0000 0000 0000 0000 0800        ................
0x0010   4500 0054 0000 4000 4001 2ca5 0101 0602        E..T..@.@.,.....
0x0020   0101 0601 0800 1f1f a613 0001 4bc0 ab40        ............K..@
0x0030   42c8 0e00 0809 0a0b 0c0d 0e0f 1011 1213        B...............
0x0040   1415 1617 1819 1a1b 1c1d 1e1f 2021 2223        .............!"#
0x0050   2425 2627 2829 2a2b 2c2d 2e2f 3031 3233        $%&'()*+,-./0123
0x0060   34                                             4

If I run exactly the same config but with 'require-mppe' removed
from configs on both client and server side, this does not happen.

versions (identical for server and client)
========
poptop-1.1.4
ppp-2.4.2_cvs_20021120
pptp-linux-1.2.0
linux-2.6.6 patched with kernelmod-0.8/2.6/* files.
	I rediffed patch against 2.6.5.
	Patch is attached.
	Was applied to 2.6.6 (with offsets).

server
======
pppd options file:
mru 1467
mtu 1467
logfd 2
require-mppe
require-mschap-v2
debug
show-password
name PPTP
remotename test

pptpd conf file:
localip 1.1.6.1
remoteip 1.1.6.2-255

pptpd \
    --conf "$PWD/pptpd.conf" \
    --option "$PWD/options.pptpd.mppe" \
    --debug \
    --fg \
    --pidfile /dev/null

client
======
pppd options file: (empty)

pppd \
    noipdefault \
    name test \
    remotename PPTP \
    nodefaultroute \
    noproxyarp \
    nodetach \
    logfd 2 \
    noauth \
    nobsdcomp \
    nodeflate \
    require-mppe \
    nomppe-stateful \
    debug \
    show-password \
    mru 1467 \
    mtu 1467 \
    lcp-echo-failure 3 \
    lcp-echo-interval 27 \
    maxfail 1 \
    pty "pptp 1.1.1.1 --nolaunchpppd" \
--
vda