root@t-Aspire-5742:/# sudo ipsec verify
Checking your system to see if IPsec got installed and started correctly:
Version check and ipsec on-path [OK]
Linux Openswan U2.6.37/K3.5.0-42-generic (netkey)
Checking for IPsec support in kernel [OK]
SAref kernel support [N/A]
NETKEY: Testing XFRM related proc values [FAILED]
Please disable /proc/sys/net/ipv4/conf/*/send_redirects
or NETKEY will cause the sending of bogus ICMP redirects! [FAILED]
Please disable /proc/sys/net/ipv4/conf/*/accept_redirects
or NETKEY will accept bogus ICMP redirects [OK]
Checking that pluto is running [OK]
Pluto listening for IKE on udp 500 [OK]
Pluto listening for NAT-T on udp 4500 [OK]
Two or more interfaces found, checking IP forwarding [FAILED]
Checking for 'ip' command [OK]
Checking /bin/sh is not /bin/dash [WARNING]
Checking for 'iptables' command [OK]
Opportunistic Encryption Support [DISABLED]
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2 Answers
You need to disable send and accept:
# Disable send redirects
echo 0 > /proc/sys/net/ipv4/conf/all/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/default/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth0/send_redirects
echo 0 > /proc/sys/net/ipv4/conf/lo/send_redirects
# Disable accept redirects
echo 0 > /proc/sys/net/ipv4/conf/all/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/default/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/eth0/accept_redirects
echo 0 > /proc/sys/net/ipv4/conf/lo/accept_redirects
To make it permanent on reboot, in your sysctl.conf place the below lines
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0
net.ipv4.conf.eth0.send_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.lo.accept_redirects = 0
net.ipv4.conf.lo.send_redirects = 0
Please norice the /proc/sys/net/ipv4/conf/... files are read only even for root user. You should disable it using your VPN configuration. For example in OpenSwan you should do:
Prompt> sudo vi /etc/sysctl.conf
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
You can also use
sudo sysctl stuff.you.want.to.change=newValue
As suggested by comments to avoid reboot
-
That is technically not true, you just don't write directly to those files. You use
sudo sysctl stuff.you.want.to.change=newValue
. To make your changes persistent, you need to edit the/etc/sysctl.conf
. Sep 1, 2016 at 12:51 -
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Persistence. If you change the configuration file, it is not changing the kernel value in real time. You need to reboot. If you use
sysctl
you change the values real time, just as if you had write access on the (read-only) files. Sep 2, 2016 at 15:05 -