The RFC 6056 algorithms

The following algorithms are available:

bsd

This is the default NetBSD port selection algorithm, which starts from anonportmax and proceeds decreasingly through the available ephemeral ports.

random_start

Select ports randomly from the available ephemeral ports. In case a collision with a local port is detected, the algorithm proceeds decreasingly through the sequence of ephemeral ports until a free port is found. Note that the random port selection algorithms are not guaranteed to find a free port.

random_pick

Select ports randomly from the available ephemeral ports. In case a collision with a local port is detected the algorithm tries selecting a new port randomly until a free port is found.

hash

Select ports using a md5(3) hash of the local address, the foreign address, and the foreign port. Note that in the case of a bind(2) call some of this information might be unavailable and the port selection is delayed until the time of a connect(2) call, performed either explicitly or up calling sendto(2).

doublehash

Select ports using a md5(3) hash of the local address, foreign address, and foreign port coupled with a md5(3) hash of the same components obtained using a separate table that is associated with a subset of all outgoing connections. The same considerations regarding late connection as in the case of hash apply.

randinc

Use random increments in order to select the next port.