Fix v6_routethrough misplaced technique switch

[ArnoStiefvater]

What:

procroutetechnique is the default technique for getting the interface we want to use for some given destination addr. This technique is represented as a static enum. Previously the technique was set to fallback method connectsockettechnique even though an appropriate interface was found because the fallback method was activated after the first route in /proc/net/ipv6_route was checked and not after all routes were checked. Every additional invocation of the function therefore used the fallback method as new default.

Why:

Fix issue, improve performance.

How:

Add the following code at the beginning of openvas.c/openvas() and add some prints in misc/pcap.c/v6_routethrough() for printing out what method we are using.

  char *interface;
  struct in6_addr dest;
  inet_pton(AF_INET6, <ipv6 addr with matching route in /proc/net/ipv6_route>, &dest);
  interface = v6_routethrough (&dest, NULL);
  g_warning("%s: interface: %s",__func__, interface);
  interface = v6_routethrough (&dest, NULL);
  g_warning("%s: interface: %s",__func__, interface);
  inet_pton(AF_INET6, <ipv6 addr with NO matching route in /proc/net/ipv6_route>, &dest);
  interface = v6_routethrough (&dest, NULL);
  g_warning("%s: interface: %s",__func__, interface);
  exit (0);

Result should be something like the following with the PR:

>> using procroutetechnique
>> interface: enp0s3
>> using procroutetechnique
>> interface: enp0s3
>> using connectsockettechnique
>> interface: enp0s9

And something like the following without the PR:

>> using procroutetechnique
>> interface: enp0s3
>> using connectsockettechnique
>> interface: enp0s3
>> using connectsockettechnique
>> interface: enp0s9

Checklist:

• Tests
• CHANGELOG Entry