* The origin PID is the PID of the process that created this socket,
either explicitly by calling socket(), or implicitly by accepting
a TCP connection. Note that accepting a local socket connection
does not create a new socket, it reuses the one connect() was
called on, so for accepted local sockets the origin PID points
to the connecting process.
* The acceptor PID is the PID of the process that accept()ed this
socket. For accepted TCP sockets, this is the same as origin PID.
This is more logical and allows us to solve the problem of
non-blocking TCP sockets getting stuck in SocketRole::None.
The only complication is that a single LocalSocket may be shared
between two file descriptions (on the connect and accept sides),
and should have two different roles depending from which side
you look at it. To deal with it, Socket::role() is made a
virtual method that accepts a file description, and LocalSocket
internally tracks which FileDescription is the which one and
returns a correct role.
The situations in IPv4Socket and LocalSocket were mirrors of each other
where one had implemented read/write as wrappers and the other had
sendto/recvfrom as wrappers.
Instead of this silliness, move read and write up to the Socket base.
Then mark them final, so subclasses have no choice but to implement
sendto and recvfrom.
After reading a bunch of POSIX specs, I've learned that a file descriptor
is the number that refers to a file description, not the description itself.
So this patch renames FileDescriptor to FileDescription, and Process now has
FileDescription* file_description(int fd).
links requests SO_ERROR, so in not supporting it, things were unhappy.
Supporting this properly looks a little messy. I guess Socket will need
an m_error member it sets everywhere it returns an error. Or Syscall
could set it, perhaps, but I don't know if that's the right thing to
do, so let's just stub this for now and file a bug.
