[PATCH mptcp-next v15 0/6] implement mptcp read_sock

[Geliang Tang <geliang@kernel.org>]

From: Geliang Tang <tanggeliang@kylinos.cn>

v15:
 - Patch 2, remove the maximum length limit as Mat suggested.
 - Move tcp_recv_should_stop() helper out of the series as Mat
   suggested.

v14:
 - Patch 2, new helper __mptcp_read_sock() with noack parameter,
 this makes it more similar to __tcp_read_sock() and also prepares
 for the use of mptcp_read_sock_noack() in MPTCP KTLS support. Also
 invoke msk_owned_by_me() in it to make sure socket was locked.
 - Patch 5, export tcp_splice_data_recv() as Paolo suggested in v7.
 - Patch 6, drop mptcp_splice_data_recv().
 - Link: https://patchwork.kernel.org/project/mptcp/cover/cover.1763974740.git.tanggeliang@kylinos.cn/

v13:
 - rebase on "mptcp: introduce backlog processing" v6
 - Link: https://patchwork.kernel.org/project/mptcp/cover/cover.1761198660.git.geliang@kernel.org/

v12:
 - rebase on "mptcp: receive path improvement" 1-7.
 - some cleanups.

v11:
 - drop "tcp: drop release and lock again in splice_read", and add this
   release and lock again in mptcp_splice_read too. (Thanks Mat, I didn't
   understand the intent of this code before.)
 - call mptcp_rps_record_subflows() in mptcp_splice_read as Mat
   suggested.

v10:
 - add an offset parameter for mptcp_recv_skb and make it more like
tcp_recv_skb.
 - Link: https://patchwork.kernel.org/project/mptcp/cover/cover.1756780274.git.tanggeliang@kylinos.cn/

v9:
 - merge the squash-to patches.
 - a new patch "drop release and lock again in splice_read".
 - Link: https://patchwork.kernel.org/project/mptcp/cover/cover.1752399660.git.tanggeliang@kylinos.cn/

v8:
 - export struct tcp_splice_state and tcp_splice_data_recv() in net/tcp.h.
 - add a new helper mptcp_recv_should_stop.
 - add mptcp_connect_splice.sh.
 - update commit logs.

v7:
 - only patch 1 and patch 2 changed.
 - add a new helper mptcp_eat_recv_skb.
 - invoke skb_peek in mptcp_recv_skb().
 - use while ((skb = mptcp_recv_skb(sk)) != NULL) instead of
 skb_queue_walk_safe(&sk->sk_receive_queue, skb, tmp).

v6:
 - address Paolo's comments for v4, v5 (thanks)

v5:
 - extract the common code of __mptcp_recvmsg_mskq() and mptcp_read_sock()
 into a new helper __mptcp_recvmsg_desc() to reduce duplication code.

v4:
 - v3 doesn't work for MPTCP fallback tests in mptcp_connect.sh, this
   set fix it.
 - invoke __mptcp_move_skbs in mptcp_read_sock.
 - use INDIRECT_CALL_INET_1 in __tcp_splice_read.

v3:
 - merge the two squash-to patches.
 - use sk->sk_rcvbuf instead of INT_MAX as the max len in
 mptcp_read_sock().
 - add splice io mode for mptcp_connect and drop mptcp_splice.c test.
 - the splice test for packetdrill is also added here:
https://github.com/multipath-tcp/packetdrill/pull/162

v2:
 - set splice_read of mptcp
 - add a splice selftest.

I have good news! I recently added MPTCP support to "NVME over TCP".
And my RFC patches are under review by NVME maintainer Hannes.

Replacing "NVME over TCP" with MPTCP is very simple. I used IPPROTO_MPTCP
instead of IPPROTO_TCP to create MPTCP sockets on both target and host
sides, these sockets are created in Kernel space.

nvmet_tcp_add_port:

	ret = sock_create(port->addr.ss_family, SOCK_STREAM,
				IPPROTO_MPTCP, &port->sock);

nvme_tcp_alloc_queue:

	ret = sock_create_kern(current->nsproxy->net_ns,
			ctrl->addr.ss_family, SOCK_STREAM,
			IPPROTO_MPTCP, &queue->sock);

nvme_tcp_try_recv() needs to call .read_sock interface of struct
proto_ops, but it is not implemented in MPTCP. So I implemented it
with reference to __mptcp_recvmsg_mskq().

Since the NVME part patches are still under reviewing, I only send the
MPTCP part patches in this set to MPTCP ML for your opinions.

Geliang Tang (6):
  mptcp: add eat_recv_skb helper
  mptcp: implement .read_sock
  tcp: export tcp_splice_state
  mptcp: implement .splice_read
  selftests: mptcp: add splice io mode
  selftests: mptcp: connect: cover splice mode

 include/net/tcp.h                             |  11 +
 net/ipv4/tcp.c                                |  13 +-
 net/mptcp/protocol.c                          | 215 +++++++++++++++++-
 tools/testing/selftests/net/mptcp/Makefile    |   1 +
 .../selftests/net/mptcp/mptcp_connect.c       |  63 ++++-
 .../net/mptcp/mptcp_connect_splice.sh         |   5 +
 6 files changed, 289 insertions(+), 19 deletions(-)
 create mode 100755 tools/testing/selftests/net/mptcp/mptcp_connect_splice.sh

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2.51.0