Fix possible heap overflow on read accessing getaddrinfo() result.

Fix possible heap overflow on read accessing getaddrinfo() result.

The code always tried to copy-out a "struct sockaddr_in6" even for IPv4
results, which reads more bytes than getaddrinfo() is guaranteed to
allocate.

Now, look at ai->ai_family and only copy "struct sockaddr" for IPv4.

Also, reformat this block of code to comply to coding style.

This is a specific 2.3 bug as the code in master (to be 2.4) has been
completely rewritten to properly handle dual-stack and multiple responses
from getaddrinfo() proper.

Bug found by Daniel Hirche using "gcc -fsanitize=address".  No possible
exploits are known.

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <1447192719-31381-1-git-send-email-gert@greenie.muc.de>
URL: http://article.gmane.org/gmane.network.openvpn.devel/10479