selftests: net: ip_defrag: ignore EPERM

When running with conntrack rules, the dropped overlap fragments may cause
EPERM to be returned to sendto. Instead of completely failing, just ignore
those errors and continue. If this causes packets with overlap fragments to
be dropped as expected, that is okay. And if it causes packets that are
expected to be received to be dropped, which should not happen, it will be
detected as failure.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests: net: ip_defrag: cover new IPv6 defrag behavior

This patch adds several changes to the ip_defrag selftest, to cover
new IPv6 defrag behavior:

- min IPv6 frag size is now 8 instead of 1280

- new test cases to cover IPv6 defragmentation in nf_conntrack_reasm.c

- new "permissive" mode in negative (overlap) tests: netfilter
sometimes drops invalid packets without passing them to IPv6
underneath, and thus defragmentation sometimes succeeds when
it is expected to fail; so the permissive mode does not fail the
test if the correct reassembled datagram is received instead of a
timeout.

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests: net: fix/improve ip_defrag selftest

Commit ade446403bfb ("net: ipv4: do not handle duplicate fragments as
overlapping") changed IPv4 defragmentation so that duplicate fragments,
as well as _some_ fragments completely covered by previously delivered
fragments, do not lead to the whole frag queue being discarded. This
makes the existing ip_defrag selftest flaky.

This patch
* makes sure that negative IPv4 defrag tests generate truly overlapping
fragments that trigger defrag queue drops;
* tests that duplicate IPv4 fragments do not trigger defrag queue drops;
* makes a couple of minor tweaks to the test aimed at increasing its code
coverage and reduce flakiness.

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests: net: Clean up an unused variable

Address compiler warning:

ip_defrag.c: In function 'send_udp_frags':
ip_defrag.c:206:16: warning: unused variable 'udphdr' [-Wunused-variable]
struct udphdr udphdr;
^~~~~~

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests/net: add ipv6 tests to ip_defrag selftest

This patch adds ipv6 defragmentation tests to ip_defrag selftest,
to complement existing ipv4 tests.

Signed-off-by: Peter Oskolkov <posk@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

selftests/net: add ip_defrag selftest

This test creates a raw IPv4 socket, fragments a largish UDP
datagram and sends the fragments out of order.

Then repeats in a loop with different message and fragment lengths.

Then does the same with overlapping fragments (with overlapping
fragments the expectation is that the recv times out).

Tested:

root@<host># time ./ip_defrag.sh
ipv4 defrag
PASS
ipv4 defrag with overlaps
PASS

real 1m7.679s
user 0m0.628s
sys 0m2.242s

A similar test for IPv6 is to follow.

Signed-off-by: Peter Oskolkov <posk@google.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>