John Fastabend says:

====================
When I added the test_sockmap to selftests I mistakenly changed the
test logic a bit. The result of this was on redirect cases we ended up
choosing the wrong sock from the BPF program and ended up sending to a
socket that had no receive handler. The result was the actual receive
handler, running on a different socket, is timing out and closing the
socket. This results in errors (-EPIPE to be specific) on the sending
side. Typically happening if the sender does not complete the send
before the receive side times out. So depending on timing and the size
of the send we may get errors. This exposed some bugs in the sockmap
error path handling.

This series fixes the errors. The primary issue is we did not do proper
memory accounting in these cases which resulted in missing a
sk_mem_uncharge(). This happened in the redirect path and in one case
on the normal send path. See the three patches for the details.

The other take-away from this is we need to fix the test_sockmap and
also add more negative test cases. That will happen in bpf-next.

Finally, I tested this using the existing test_sockmap program, the
older sockmap sample test script, and a few real use cases with
Cilium. All of these seem to be in working correctly.

v2: fix compiler warning, drop iterator variable 'i' that is no longer
    used in patch 3.
====================

Signed-off-by: Alexei Starovoitov <ast@kernel.org>