src: introduce common.{c,h} for shared functions

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
src: moving more socket helper functions

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
src: Connect as wrapper and adjust exit return codes

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
src: add an udp_flood program

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>