options.c: enforce a minimal fragment size

options.c: enforce a minimal fragment size

Very low values for 'fragment' can result in a division by zero in
optimal_fragment_size() (because it rounds max_frag_size down with
FRAG_SIZE_ROUND_MASK).

Enforce a minimal fragment size of 68 bytes, based on RFC 791 ("Every
internet module must be able to forward a datagram of 68 octets without
further fragmentation.")

Signed-off-by: Kristof Provost <kprovost@netgate.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20230301091851.82243-1-kprovost@netgate.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg26313.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>