Merge branch 'vsock-tests'

Stefano Garzarella says:

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vsock/test: add recv_buf()/send_buf() utility functions and some improvements

We recently found that some tests were failing [1].

The problem was that we were not waiting for all the bytes correctly,
so we had a partial read. I had initially suggested using MSG_WAITALL,
but this could have timeout problems.

Since we already had send_byte() and recv_byte() that handled the timeout,
but also the expected return value, I moved that code to two new functions
that we can now use to send/receive generic buffers.

The last commit is just an improvement to a test I found difficult to
understand while using the new functions.

@Arseniy a review and some testing are really appreciated :-)

[1] https://lore.kernel.org/netdev/63xflnwiohdfo6m3vnrrxgv2ulplencpwug5qqacugqh7xxpu3@tsczkuqgwurb/
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Signed-off-by: David S. Miller <davem@davemloft.net>