This approach is a bit naiive - whenever we send a packet out, we
check to see if there are any other packets we should try to send.
This works well enough for a busy connection but not very well for a
quiet one. Ideally we would check for not-acked packets on some kind
of timer, and use the length of this not-acked list as feedback to
throttle the writes coming from userspace.
This allows us to take advantage of unsolicited ARP replies, such as
those that are emitted by many systems after their network interfaces
are enabled, or after their DHCP client sets their IP.
This also makes us a bit more vulnerable to ARP flooding, but we need
some kind of eviction strategy anyway, so we can deal with that later.
An incoming socket should only be considered connected after a
program has received it from accept(). Before that point, it's only
"half" open, and it might not ever actually be served to a program.
Socket::accept is where m_connected is correctly set.
This was a workaround to be able to build on case-insensitive file
systems where it might get confused about <string.h> vs <String.h>.
Let's just not support building that way, so String.h can have an
objectively nicer name. :^)
This replaces the previous placeholder routing layer with a real one!
It's still very primitive, doesn't deal with things like timeouts very
well, and will probably need several more iterations to support more
normal networking things.
I haven't confirmed that this works with anything other than the QEMU
user networking layer, but I suspect that's what nearly everybody is
using at this point, so that's the important target to keep working.
By setting up the devices in init() and looping over the registered
network adapters in NetworkTask_main, we can remove the remaining
hard-coded adapter references from the network code.
This also assigns IPs according to the default range supplied by QEMU
in its slirp networking mode.
* 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.
Now that there can't be multiple clones of the same fd,
we only need to track whether or not an fd exists on each
side. Also there's no point in tracking connecting fds.
