The idea is to abstract over the users that kamid manages. The virtual table allows to use a custom userbase instead of the local UNIX users. The userdata tables maps (virtual) users to their home directory, which is the only directory tree exported by kamid as of now. Together, they allow a powerful and flexible management of the users and their data. The idea is somewhat stolen from smtpd(8).

The documentation says explicitly that the offset is *either* 0 or the last offset plus count; that means that after some read a client can require *again* an offset 0 (i.e. doing a rewinding the directory.)