Re: [lwip-devel] [bug #44032] LWIP_NETCONN_FULLDUPLEX: select might work on invalid/reused socket

[Fabian Koch]

Hey Joel,

Well the ultimate problem that "the application" has to keep track of all its 
sockets over all different threads involved will never go away, but I guess 
that's a given.

So you have scenarios like this:

"main application thread" creates a socket, creates a child thread, gives the 
socket fd to the child thread but keeps track of it too.
Now when the child is blocking on accept() and the whole application is 
supposed to be shut down, the main app thread can call close() on the socket 
that the child thread is waiting on without the universe exploding as it used 
to be in LWIP.

Same thing for full duplex protocols. They will also need a main thread that 
creates a send and a receive thread and gives them the fd of a socket to 
send/rec on. Or either of them creates a sockets and provides the others with 
the fd.
Still you should have one main thread that keeps track of all socket fds.

So in essence, implementing the long awaited "multiple threads can work on the 
same socket" feature in LWIP of course does not change the fact that 
application developers need to know what they are doing with their sockets.
Now they just have to spread that knowledge among more threads than one.

Cheers,
Fabian