Function calls not permitted in kernel code

From: Mark James (mrj@cs.usyd.edu.au)
Date: Wed Sep 20 2000 - 07:01:16 EST


Hi, couldn't find an answer to this in any FAQ:

Can anyone point me to a clear summary of what can and what
can't be called by kernel code.

That is, can a kernel module open and read files or sockets,
call libc functions, start processes?

If, as I suspect, none of these are possible, are the options
to:

(1) Get a user process to do the work, communicating
    with the kernel via /proc or some other way.

(2) Doing things really low-level through kernel calls
    (such as injecting skbs into TCP/IP code).

Thanks -- Mark

PS: Are there any plans to go beyond store and forward for
    IP forwarding to implement Tx as soon as the IP header is
    Rx-ed and checked, while the packet data is still being
    Rx-ed? How useful would this be for Internet latency
    on unsaturated links?
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