Simple test program to check the behaviour we need for bind() address
conflicts between listening sockets and repair mode sockets.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Add both format string and ((noreturn)) attributes to the version of die()
used in the test programs in doc/platform-requirements.  As well as
potentially catching problems in format strings, this means that the
compiler and static checkers can properly reason about the fact that it
will exit, preventing bogus warnings.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Recent clang-tidy versions complain about enums defined with some but not
all entries given explicit values.  I'm not entirely convinced about
whether that's a useful warning, but in any case we really don't need the
explicit values in doc/platform-requirements/reuseaddr-priority.c, so
remove them to make clang happy.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

This test program verifies that we can receive and discard datagrams by
using recv() with a NULL buffer and zero-length.  Extend it to verify it
also works using recvmsg() and either an iov with a zero-length NULL
buffer or an iov that itself is NULL and zero-length.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Fixed printf() message in main of recv-zero.c]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

To simplify lifetime management of "listening" UDP sockets, UDP flow
support needs to duplicate existing bound sockets.  Those duplicates will
be close()d when their corresponding flow expires, but we expect the
original to still receive datagrams as always.  That is, we expect the
close() on the duplicate to remove the duplicated fd, but not to close the
underlying UDP socket.

Add a test program to doc/platform-requirements to verify this requirement.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

This test program checks for particular behaviour regardless of order of
operations.  So, we step through the test with all possible orders for
a number of different of parts.  Or at least, we're supposed to, a copy
pasta error led to using the same order for two things which should be
independent.

Fixes: 299c40750137 ("doc: Add program to document and test assumptions about SO_REUSEADDR")
Reported-by: David Taylor <davidt@yadt.co.uk>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

Add a test program verifying that we're able to discard datagrams from a
socket without needing a big discard buffer, by using a zero length recv().

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

For the approach we intend to use for handling UDP flows, we have some
pretty specific requirements about how SO_REUSEADDR works with UDP sockets.
Specifically SO_REUSEADDR allows multiple sockets with overlapping bind()s,
and therefore there can be multiple sockets which are eligible to receive
the same datagram.  Which one will actually receive it is important to us.

Add a test program which verifies things work the way we expect, which
documents what those expectations are in the process.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>