This patch reintroduces the LwIP stack to libc as a VFS plugin
implementing the socket_fs interface. Rather than use LwIP's socket
emulation layer this plugin interfaces directly to LwIP raw API and is
single threaded.
The internal TCP parameters of the stack are untuned.
Fix#2050Fix#2335
Generic code that operates over both UDP and TCP sockets might use
'sendto', but in the case of TCP the destination address ought to be
safely discarded. This seems to be the case for certain DNS software
that operates over both UDP and TCP.
Fix#2807
Socket_fs sockets are now created each time a 'new_socket' control file
is opened, not each time a 'new_socket' file is read. When a handle on a
'new_socket' file is closed the socket and its socket files are
destroyed. The accept control file on a listening socket reads "1" or
reads nothing to indicate a client connection is queued. Client sockets
are accepted by opening an 'accept_socket' file in the listen socket
directory. This file behaves like the aforementioned 'new_socket' file.
Ref #2707
This prevents diagnostic messages like
Error: partial write detected 0 vs 31
for writes into already released socket directories due to a still-open
handle to the socket data file.
There are programs, e.g. curl, that check if a connection was
established successfully by looking at SO_ERROR. Pretend that
the getsockopt() call was executed to keep them happy. If they
try to use a broken connection, the other socket functions will
bail.
If 'close' does not call 'unlink' like 'shutdown', the Lxip_socket_dir
never gets destroyed and thus the socket server leaks resources like
RAM and ports.
Ref #2285
Our 'shutdown' implementation handles only the case that 'how' is 'RDWR'.
Thus, print an error and continue if a user calls it with another value.
Fixes#2285
The socket file system can be configured in the "socket" attribute of
the libc config node like follows.
<vfs> <dir name="socket"> <fs/> </dir> </vfs>
<libc ... socket="/socket"/>
This configures the socket file system libc backend to access files in
"/socket" for socket operations.
