How can I stop openconnect from changing /etc/resolv.conf?

Question

When I run openconnect (with the default vpnc script) it changes /etc/resolv.conf and it really shouldn't do that. I am just using the VPN for a few specific host not for a full Internet connection.

Answer 1

Does vpnc-script look like this? If so, the belows code is why it changes your /etc/resolv.conf:

if [ -x /sbin/resolvconf ]; then # Optional tool on Debian, Ubuntu, Gentoo
    MODIFYRESOLVCONF=modify_resolvconf_manager
    RESTORERESOLVCONF=restore_resolvconf_manager
elif [ -x /sbin/modify_resolvconf ]; then # Mandatory tool on Suse earlier than 11.1
    MODIFYRESOLVCONF=modify_resolvconf_suse
    RESTORERESOLVCONF=restore_resolvconf_suse
else # Generic for any OS
    MODIFYRESOLVCONF=modify_resolvconf_generic
    RESTORERESOLVCONF=restore_resolvconf_generic
fi

modify_resolvconf_manager() {
    NEW_RESOLVCONF=""
    for i in $INTERNAL_IP4_DNS; do
        NEW_RESOLVCONF="$NEW_RESOLVCONF
nameserver $i"
    done
    if [ -n "$CISCO_DEF_DOMAIN" ]; then
        NEW_RESOLVCONF="$NEW_RESOLVCONF
domain $CISCO_DEF_DOMAIN"
    fi
    echo "$NEW_RESOLVCONF" | /sbin/resolvconf -a $TUNDEV
}

The 'dirty' way is make the /etc/resolv.conf file immutable:

# chattr +i /etc/resolv.conf

The proper way is edit your vpnc-script to make it shouldn't change the /etc/resolv.conf.