Force to connect via IPv4

[Thomas Glanzmann]

Hello,
I'm on a network where there is no IPv6 connectivity. When I try to fire
up openconnect, it tries to connect via IPv6 and there does not seem to
be an option to force IPv4. I now removed the DNS entry and waiting for
it to time out, but I wonder if there is a trick, otherwise I would
probably would make a patch ready.

(x1) [~/work/openconnect-7.08] /local/openconnect-7.08/sbin/openconnect vpn.gmvl.de
POST https://vpn.gmvl.de/
Failed to connect to [2a01:4f8:b0:2fff::2]:443: Network is unreachable
Failed to connect to host vpn.gmvl.de
Failed to open HTTPS connection to vpn.gmvl.de
Failed to obtain WebVPN cookie

(x1) [~/work/openconnect-7.08] ip a s
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 54:ee:75:43:af:c9 brd ff:ff:ff:ff:ff:ff
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 60:57:18:91:6f:7c brd ff:ff:ff:ff:ff:ff
    inet 192.168.4.84/20 brd 192.168.15.255 scope global wlan0
       valid_lft forever preferred_lft forever
    inet6 fe80::6257:18ff:fe91:6f7c/64 scope link
       valid_lft forever preferred_lft forever
4: wwan0: <BROADCAST,MULTICAST,NOARP> mtu 1428 qdisc noop state DOWN group default qlen 1000
    link/ether 06:54:d8:8b:e2:dd brd ff:ff:ff:ff:ff:ff

Cheers,
        Thomas