[PATCH v5 bpf-next 0/7] bpf: Add socket destroy capability

[Aditi Ghag <aditi.ghag@isovalent.com>]

This patch adds the capability to destroy sockets in BPF. We plan to use
the capability in Cilium to force client sockets to reconnect when their
remote load-balancing backends are deleted. The other use case is
on-the-fly policy enforcement where existing socket connections prevented
by policies need to be terminated.

The use cases, and more details around
the selected approach were presented at LPC 2022 -
https://lpc.events/event/16/contributions/1358/.
RFC discussion -
https://lore.kernel.org/netdev/CABG=zsBEh-P4NXk23eBJw7eajB5YJeRS7oPXnTAzs=yob4EMoQ@mail.gmail.com/T/#u.
v4 patch series -
https://lore.kernel.org/bpf/20230323200633.3175753-1-aditi.ghag@isovalent.com/T/#t

v5 highlights:
Address review comments:
Martin:
- Fixed bugs in the resume operation for UDP iterator.
- Added clean-up preparatory commits prior to the batching commit.
Stan:
- Programmatically retrieve and share server port in the selftests.
- Acquire slow sock lock in UDP iterator to be consistent with TCP.
- Addressed formatting nits.

(Below notes are same as v2 patch series that are still relevant. Refer to
earlier patch series for other notes.)
- I hit a snag while writing the kfunc where verifier complained about the
  `sock_common` type passed from TCP iterator. With kfuncs, there don't
  seem to be any options available to pass BTF type hints to the verifier
  (equivalent of `ARG_PTR_TO_BTF_ID_SOCK_COMMON`, as was the case with the
  helper).  As a result, I changed the argument type of the sock_destory
  kfunc to `sock_common`.

Aditi Ghag (7):
  bpf: tcp: Avoid taking fast sock lock in iterator
  udp: seq_file: Remove bpf_seq_afinfo from udp_iter_state
  udp: seq_file: Helper function to match socket attributes
  bpf: udp: Implement batching for sockets iterator
  bpf: Add bpf_sock_destroy kfunc
  selftests/bpf: Add helper to get port using getsockname
  selftests/bpf: Test bpf_sock_destroy

 include/net/udp.h                             |   1 -
 net/core/filter.c                             |  54 ++++
 net/ipv4/tcp.c                                |  10 +-
 net/ipv4/tcp_ipv4.c                           |   5 +-
 net/ipv4/udp.c                                | 286 +++++++++++++++---
 tools/testing/selftests/bpf/network_helpers.c |  14 +
 tools/testing/selftests/bpf/network_helpers.h |   1 +
 .../selftests/bpf/prog_tests/sock_destroy.c   | 203 +++++++++++++
 .../selftests/bpf/progs/sock_destroy_prog.c   | 147 +++++++++
 9 files changed, 676 insertions(+), 45 deletions(-)
 create mode 100644 tools/testing/selftests/bpf/prog_tests/sock_destroy.c
 create mode 100644 tools/testing/selftests/bpf/progs/sock_destroy_prog.c

-- 
2.34.1