Sending Signals Between Processes Owned by Different Users

[rorys]

Hello,

I have a small chat program I'm working on (in C), which attaches to some shared memory, where it will write/read all the messages. I'm using interrupts to wake up all the other clients when one client sends a message to the shared memory (this way all the other clients will read the memory and display the message). My problem is, processes owned by one user cannot send signals to a process owned by a different user (unless the user sending signals is root of course). So, is there anyway in OpenBSD to allow processes owned by two different users to send signals to eachother? In Linux, I know there is something called libcap, which allows setting the file capabilities of a binary; could there be anything similar in OpenBSD? Thanks!

[jggimi]

Hello, and welcome!


Have you considered TCP sockets? I believe that's what talk(1) uses.

[rorys]

Aren't TCP sockets blocking, though? I'm trying not to use polling if at all possible, since it would eat up a lot of CPU time if there aren't many messages being sent.

Also, thanks for the welcome!

[jggimi]

OpenBSD has System V IPCS shared memory tools, but I have never tried to program with them and don't know their limitations or restrictions. See ipcs(1), ipcrm(1), shmctl(2), shmget(2), shmat(2), ...

[e1-531g]

TCP sockets may be non-blocking, see socket(2).

SOCK_NONBLOCK Set non-blocking I/O mode on the new socket.

[rorys]

I will look into IPCS tools some more and see if it has any utilities for setting permissions regarding signals. I'll also take a look at sockets then if I have no look with IPCS. I did not realize sockets could be non-blocking.

Thanks everyone for the replies !