13 Oct
2020
13 Oct
'20
4:19 p.m.
On Oct 13, 2020, at 10:01 AM, Johnny Billquist <bqt
at softjar.se> wrote:
I thought the message receive blocks were only used for interprocess communication, and
not for anything DECnet related. But then again, DECnet under RSTS/E is not something I
ever was exposed to.
No, DECnet uses an extension of the IPC feature. A receive block allows you do to either,
subject to quotas. Local messages and the various DECnet messages are all queued to the
receive block, with a type code indicating what sort of message it is.
The "with privilege mask" message I mentioned is a variation on the local IPC
message, with a distinct function code and a portion of the payload dedicated to the masks
and PPN. Those fields are all set by the kernel, so the receiving program can use and
trust those values.
paul
...
In RSTS, it isn't a privilege but rather a quota (for "message receive
blocks" which are somewhat like Unix sockets). If your quota for those is 0 you
can't do networking. There are also login terminal flags that control (a) any
interactive login, (b) any login on a dialup line (modem controlled line) and (c) login
via DECnet. So it's possible to set up an account that can't be accessed via SET
HOST.