So for the past week or so I’ve been trying to set up a dual-stack-payload OpenVPN server. I was playing around with some IPv6 route settings earlier when it started doing this:
$ sudo openvpn /etc/openvpn/server.conf Wed Aug 31 02:41:06 2011 Herp derp, herpity derp derp... Wed Aug 31 02:41:06 2011 TCP/UDP: Socket bind failed on local address [AF_INET]64.71.167.212:1194: Address already in use Wed Aug 31 02:41:06 2011 Exiting due to fatal error $ echo "OH FUCK WHY WONT IT WORK!!!!1!1one!!1!" OH FUCK WHY WONT IT WORK!!!!1!1one!!1!
$ cat /etc/openvpn/up.sh #!/bin/sh sysctl -w net.ipv4.ip_forward=1 sysctl -w net.ipv6.conf.all.forwarding=1 ip link set $dev up promisc on mtu $tun_mtu brctl addif br0 $dev iptables -t nat -A POSTROUTING -s 10.4.4.0/24 -o eth0 -j MASQUERADE service radvd restart true
$ sudo lsof -i ":openvpn" COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME radvd 2486 root 6u IPv4 12816 0t0 TCP srwz.us:openvpn (LISTEN) radvd 2487 radvd 6u IPv4 12816 0t0 TCP srwz.us:openvpn (LISTEN)
WHAT??? radvd is listening on OpenVPN’s port?
Some background: I was restarting radvd in the up script because it’s set to advertise on tap0, but tap0 doesn’t exist when the system boots, so instead of messing with the init scripts, I decided to just restart radvd in the up script. However, since the up script is executed as a subprocess of OpenVPN, it apparently inherits OpenVPN’s sockets, and radvd in turn inherits the shell script’s sockets, causing problems when you restart OpenVPN (even with SIGHUP, I would assume). *
Now I do have IgnoreIfMissing on; in my radvd.conf file (it’s not the default yet in the radvd 1.7 that ships with natty), but I didn’t realize that starting radvd succeeded when tap0 didn’t exist, which is why I was doing it in the up file. radvd rereads its config file on SIGHUP, so to fix the issue, I simply changed this line in the up script:
service radvd restart
to:
kill -HUP `cat /var/run/radvd/radvd.pid`
and restarting OpenVPN worked again.
Time to go to bed now. I hope this helps someone.
* Disclaimer: I don’t have 200 years of UNIX experience like some people do, so I may be a little bit wrong about this. But I’m probably right. 
