Remote "access" points

[Calum]

Hello all,

I am looking through the Erlang source for any remote access points.
My plan is to try restricting what can be called on a node.

I've found the ones for spawn - partly because I was looking in the
right place, and partly because they're helpfully commented in
net_kernel.erl as

%%
%% The spawn/4 BIF ends up here.
%%
handle_call({spawn,M,F,A,Gleader},{From,Tag},State) when is_pid(From) ->
    do_spawn([no_link,{From,Tag},M,F,A,Gleader],[],State);

By changing that to
handle_call({spawn,M,F,A,Gleader},{From,Tag},State) when is_pid(From),
M =:= 'public' ->
    do_spawn([no_link,{From,Tag},M,F,A,Gleader],[],State);

I get the desired effect. Trying to spawn('paranoid@REDACTED', os,
cmd, ['ls']) fails on the calling node (although the "paranoid" node
dies a noisy death which isn't ideal, but is fine for testing).
Spawning a public:* function works.

However, I'm not able to find the place where rpc:*call requests
arrive. Can anyone point me at the right place? As well as any other
points at which remote nodes can start new processes.

Another thing - putting a debug io:format doesn't seem to be a good
way to debug which functions are being hit - is there a better way?

Someone also mentioned that when you obtained a Pid from a spawn, you
can do other things with it? Could someone explain what you can do
with it?


C