Spurious wakeups in tcp_msg_wait_data() isn't being handled by
tcp_bpf_recvmsg() and tcp_bpf_recvmsg_parser(), leading to unexpected
EAGAIN errors returned by recvfrom()/recv().  Adding handling for the
wakeup and a selftest.

Changes in v2:
- In tcp_bpf_recvmsg, handle signals and the socket closing in the loop.
- Fix spurious wakeups when SO_RCVTIMEO has been set on the socket.
- Link to v1: https://patch.msgid.link/ak_rR-Skd8Mvn4mH@localhost.localdomain

Changes in v3:
- Added the sockmap_recvfrom selftest.
- Link to v2: https://patch.msgid.link/alFRK66z45eDNZA7@localhost.localdomain

Signed-off-by: Nnamdi Onyeyiri <redacted>
---
Nnamdi Onyeyiri (2):
  bpf, sockmap: handle spurious tcp_msg_wait_data() wakeup
  bpf, sockmap: handle spurious tcp_msg_wait_data() wakeup

 net/ipv4/tcp_bpf.c                            |  55 +++-
 tools/testing/selftests/net/.gitignore        |   2 +
 tools/testing/selftests/net/Makefile          |   6 +
 .../selftests/net/sockmap_recvfrom.bpf.c      |  31 ++
 .../testing/selftests/net/sockmap_recvfrom.c  | 288 ++++++++++++++++++
 5 files changed, 373 insertions(+), 9 deletions(-)
 create mode 100644 tools/testing/selftests/net/sockmap_recvfrom.bpf.c
 create mode 100644 tools/testing/selftests/net/sockmap_recvfrom.c

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2.52.0