In order to prioritize iSCSI traffic across a network,
DSCP can be used. In order not to rely on "ipfw setdscp"
or in-network reclassification, this adds the dscp value
directly to the portal group (where TCP sessions are accepted).
As the an incoming iSCSI session is first handled by ctld for
CHAP authentication and the socket - once found to match all
prerequisites - is then handed off to the in-kernel iscsi
driver without modification of the socket parameters, simply
setting up the socket here is sufficient to keep sending
outgoing iSCSI related traffic with the correct DSCP.