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io_uring does non-blocking connection attempts, which can yield some unexpected results if a connect request is re-attempted by an an application. This is equivalent to the following sync syscall sequence: sock = socket(AF_INET, SOCK_STREAM | SOCK_NONBLOCK, IPPROTO_TCP); connect(sock, &addr, sizeof(addr); ret == -1 and errno == EINPROGRESS expected here. Now poll for POLLOUT on sock, and when that returns, we expect the socket to be connected. But if we follow that procedure with: connect(sock, &addr, sizeof(addr)); you'd expect ret == -1 and errno == EISCONN here, but you actually get ret == 0. If we attempt the connection one more time, then we get EISCON as expected. io_uring used to do this, but turns out that bluetooth fails with EBADFD if you attempt to re-connect. Also looks like EISCONN _could_ occur with this sequence. Retain the ->in_progress logic, but work-around a potential EISCONN or EBADFD error and only in those cases look at the sock_error(). This should work in general and avoid the odd sequence of a repeated connect request returning success when the socket is already connected. This is all a side effect of the socket state being in a CONNECTING state when we get EINPROGRESS, and only a re-connect or other related operation will turn that into CONNECTED. Cc: stable@vger.kernel.org Fixes: 3fb1bd688172 ("io_uring/net: handle -EINPROGRESS correct for IORING_OP_CONNECT") Link: https://github.com/axboe/liburing/issues/980 Signed-off-by: Jens Axboe <axboe@kernel.dk>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.