I have built a xl2tpd/ipsec server on my ubuntu 12.04.3, and I managed to make a l2tp vpn connection to the xl2tpd server from my android phone. The xl2tpd log said

xl2tpd[10828]: Enabling IPsec SAref processing for L2TP transport mode SAs
xl2tpd[10828]: IPsec SAref does not work with L2TP kernel mode yet, enabling     forceuserspace=yes
xl2tpd[10828]: setsockopt recvref[22]: Protocol not available
xl2tpd[10828]: This binary does not support kernel L2TP.
xl2tpd[10828]: xl2tpd version xl2tpd-1.2.8 started on atime.me PID:10828
xl2tpd[10828]: Written by Mark Spencer, Copyright (C) 1998, Adtran, Inc.
xl2tpd[10828]: Forked by Scott Balmos and David Stipp, (C) 2001
xl2tpd[10828]: Inherited by Jeff McAdams, (C) 2002
xl2tpd[10828]: Forked again by Xelerance (www.xelerance.com) (C) 2006
xl2tpd[10828]: Listening on IP address 0.0.0.0, port 1701
xl2tpd[10828]: control_finish: Peer requested tunnel 39154 twice, ignoring second one.
xl2tpd[10828]: Connection established to 117.136.8.59, 43149.  Local: 25339, Remote: 39154 (ref=0/0).  LNS session is 'default'

However I cannot access the web in my browser. The pppd log said

rcvd [Compressed data] 00 1d 82 c4 7c 04 d8 09 ...
sent [CCP ResetReq id=0x7]

I have googled a lot and found that this was mostly caused by a mppe decompression error. I have disabled BSD-Compress compression with nobsdcomp in /etc/ppp/xl2tpd-options but it did not work.

I used openswan-2.6.33 and xl2tpd-1.2.8 which were built from source. And my configurations:

/etc/ipsec.conf

version 2.0

config setup
    nat_traversal=yes
    virtual_private=%v4:10.0.0.0/8,%v4:192.168.0.0/16,%v4:172.16.0.0/12
    oe=off
    protostack=netkey

conn L2TP-PSK-NAT
    rightsubnet=vhost:%priv
    also=L2TP-PSK-noNAT

conn L2TP-PSK-noNAT
    authby=secret
    pfs=no
    auto=add
    keyingtries=3
    rekey=no
    ikelifetime=8h
    keylife=1h
    type=transport
    left=106.186.121.214
    leftprotoport=17/1701
    right=%any
    rightprotoport=17/%any

/etc/xl2tpd/xl2tpd.conf

[global]
ipsec saref = yes

[lns default]
local ip = 10.10.11.1
ip range = 10.10.11.2-10.10.11.245
refuse chap = yes
refuse pap = yes
require authentication = yes
ppp debug = yes
pppoptfile = /etc/ppp/xl2tpd-options
length bit = yes

/etc/ppp/xl2tpd-options

require-mschap-v2
ms-dns 8.8.8.8
ms-dns 8.8.4.4
asyncmap 0
auth
crtscts
lock
hide-password
modem
name l2tpd
proxyarp
lcp-echo-interval 30
lcp-echo-failure 4
debug
nobsdcomp

Any suggestions? Thanks in advance.