mptcp: prefer strscpy over strcpy

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehav

mptcp: prefer strscpy over strcpy

strcpy() performs no bounds checking on the destination buffer. This
could result in linear overflows beyond the end of the buffer, leading
to all kinds of misbehaviors. The safe replacement is strscpy() [1].

This is in preparation of a possible future step where all strcpy() uses
will be removed in favour of strscpy() [2].

This fixes CheckPatch warnings:

WARNING: Prefer strscpy over strcpy

Link: https://www.kernel.org/doc/html/latest/process/deprecated.html#strcpy [1]
Link: https://github.com/KSPP/linux/issues/88 [2]
Reviewed-by: Geliang Tang <geliang@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20240514011335.176158-6-martineau@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: sockopt: info: stop early if no buffer

Up to recently, it has been recommended to use getsockopt(MPTCP_INFO) to
check if a fallback to TCP happened, or if the client requested to use
MPTCP.

mptcp: sockopt: info: stop early if no buffer

Up to recently, it has been recommended to use getsockopt(MPTCP_INFO) to
check if a fallback to TCP happened, or if the client requested to use
MPTCP.

In this case, the userspace app is only interested by the returned value
of the getsocktop() call, and can then give 0 for the option length, and
NULL for the buffer address. An easy optimisation is then to stop early,
and avoid filling a local buffer -- which now requires two different
locks -- if it is not needed.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20240514011335.176158-4-martineau@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: fix full TCP keep-alive support

SO_KEEPALIVE support has been added a while ago, as part of a series
"adding SOL_SOCKET" support. To have a full control of this keep-alive
feature, it is impo

mptcp: fix full TCP keep-alive support

SO_KEEPALIVE support has been added a while ago, as part of a series
"adding SOL_SOCKET" support. To have a full control of this keep-alive
feature, it is important to also support TCP_KEEP* socket options at the
SOL_TCP level.

Supporting them on the setsockopt() part is easy, it is just a matter of
remembering each value in the MPTCP sock structure, and calling
tcp_sock_set_keep*() helpers on each subflow. If the value is not
modified (0), calling these helpers will not do anything. For the
getsockopt() part, the corresponding value from the MPTCP sock structure
or the default one is simply returned. All of this is very similar to
other TCP_* socket options supported by MPTCP.

It looks important for kernels supporting SO_KEEPALIVE, to also support
TCP_KEEP* options as well: some apps seem to (wrongly) consider that if
the former is supported, the latter ones will be supported as well. But
also, not having this simple and isolated change is preventing MPTCP
support in some apps, and libraries like GoLang [1]. This is why this
patch is seen as a fix.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/383
Fixes: 1b3e7ede1365 ("mptcp: setsockopt: handle SO_KEEPALIVE and SO_PRIORITY")
Link: https://github.com/golang/go/issues/56539 [1]
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20240514011335.176158-3-martineau@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: SO_KEEPALIVE: fix getsockopt support

SO_KEEPALIVE support has to be set on each subflow: on each TCP socket,
where sk_prot->keepalive is defined. Technically, nothing has to be done
on the MP

mptcp: SO_KEEPALIVE: fix getsockopt support

SO_KEEPALIVE support has to be set on each subflow: on each TCP socket,
where sk_prot->keepalive is defined. Technically, nothing has to be done
on the MPTCP socket. That's why mptcp_sol_socket_sync_intval() was
called instead of mptcp_sol_socket_intval().

Except that when nothing is done on the MPTCP socket, the
getsockopt(SO_KEEPALIVE), handled in net/core/sock.c:sk_getsockopt(),
will not know if SO_KEEPALIVE has been set on the different subflows or
not.

The fix is simple: simply call mptcp_sol_socket_intval() which will end
up calling net/core/sock.c:sk_setsockopt() where the SOCK_KEEPOPEN flag
will be set, the one used in sk_getsockopt().

So now, getsockopt(SO_KEEPALIVE) on an MPTCP socket will return the same
value as the one previously set with setsockopt(SO_KEEPALIVE).

Fixes: 1b3e7ede1365 ("mptcp: setsockopt: handle SO_KEEPALIVE and SO_PRIORITY")
Acked-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20240514011335.176158-2-martineau@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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tcp: socket option to check for MPTCP fallback to TCP

A way for an application to know if an MPTCP connection fell back to TCP
is to use getsockopt(MPTCP_INFO) and look for errors. The issue with
th

tcp: socket option to check for MPTCP fallback to TCP

A way for an application to know if an MPTCP connection fell back to TCP
is to use getsockopt(MPTCP_INFO) and look for errors. The issue with
this technique is that the same errors -- EOPNOTSUPP (IPv4) and
ENOPROTOOPT (IPv6) -- are returned if there was a fallback, *or* if the
kernel doesn't support this socket option. The userspace then has to
look at the kernel version to understand what the errors mean.

It is not clean, and it doesn't take into account older kernels where
the socket option has been backported. A cleaner way would be to expose
this info to the TCP socket level. In case of MPTCP socket where no
fallback happened, the socket options for the TCP level will be handled
in MPTCP code, in mptcp_getsockopt_sol_tcp(). If not, that will be in
TCP code, in do_tcp_getsockopt(). So MPTCP simply has to set the value
1, while TCP has to set 0.

If the socket option is not supported, one of these two errors will be
reported:
- EOPNOTSUPP (95 - Operation not supported) for MPTCP sockets
- ENOPROTOOPT (92 - Protocol not available) for TCP sockets, e.g. on the
socket received after an 'accept()', when the client didn't request to
use MPTCP: this socket will be a TCP one, even if the listen socket
was an MPTCP one.

With this new option, the kernel can return a clear answer to both "Is
this kernel new enough to tell me the fallback status?" and "If it is
new enough, is it currently a TCP or MPTCP socket?" questions, while not
breaking the previous method.

Acked-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240509-upstream-net-next-20240509-mptcp-tcp_is_mptcp-v1-1-f846df999202@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: add last time fields in mptcp_info

This patch adds "last time" fields last_data_sent, last_data_recv and
last_ack_recv in struct mptcp_sock to record the last time data_sent,
data_recv and ac

mptcp: add last time fields in mptcp_info

This patch adds "last time" fields last_data_sent, last_data_recv and
last_ack_recv in struct mptcp_sock to record the last time data_sent,
data_recv and ack_recv happened. They all are initialized as
tcp_jiffies32 in __mptcp_init_sock(), and updated as tcp_jiffies32 too
when data is sent in __subflow_push_pending(), data is received in
__mptcp_move_skbs_from_subflow(), and ack is received in ack_update_msk().

Similar to tcpi_last_data_sent, tcpi_last_data_recv and tcpi_last_ack_recv
exposed with TCP, this patch exposes the last time "an action happened" for
MPTCP in mptcp_info, named mptcpi_last_data_sent, mptcpi_last_data_recv and
mptcpi_last_ack_recv, calculated in mptcp_diag_fill_info() as the time
deltas between now and the newly added last time fields in mptcp_sock.

Since msk->last_ack_recv needs to be protected by mptcp_data_lock/unlock,
and lock_sock_fast can sleep and be quite slow, move the entire
mptcp_data_lock/unlock block after the lock/unlock_sock_fast block.
Then mptcpi_last_data_sent and mptcpi_last_data_recv are set in
lock/unlock_sock_fast block, while mptcpi_last_ack_recv is set in
mptcp_data_lock/unlock block, which is protected by a spinlock and
should not block for too long.

Also add three reserved bytes in struct mptcp_info not to have holes in
this structure exposed to userspace.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/446
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240410-upstream-net-next-20240405-mptcp-last-time-info-v2-1-f95bd6b33e51@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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tcp: annotate data-races around tp->window_clamp

tp->window_clamp can be read locklessly, add READ_ONCE()
and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by

tcp: annotate data-races around tp->window_clamp

tp->window_clamp can be read locklessly, add READ_ONCE()
and WRITE_ONCE() annotations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Link: https://lore.kernel.org/r/20240404114231.2195171-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: prevent BPF accessing lowat from a subflow socket.

Alexei reported the following splat:

WARNING: CPU: 32 PID: 3276 at net/mptcp/subflow.c:1430 subflow_data_ready+0x147/0x1c0
Modules linked

mptcp: prevent BPF accessing lowat from a subflow socket.

Alexei reported the following splat:

WARNING: CPU: 32 PID: 3276 at net/mptcp/subflow.c:1430 subflow_data_ready+0x147/0x1c0
Modules linked in: dummy bpf_testmod(O) [last unloaded: bpf_test_no_cfi(O)]
CPU: 32 PID: 3276 Comm: test_progs Tainted: GO 6.8.0-12873-g2c43c33bfd23
Call Trace:
<TASK>
mptcp_set_rcvlowat+0x79/0x1d0
sk_setsockopt+0x6c0/0x1540
__bpf_setsockopt+0x6f/0x90
bpf_sock_ops_setsockopt+0x3c/0x90
bpf_prog_509ce5db2c7f9981_bpf_test_sockopt_int+0xb4/0x11b
bpf_prog_dce07e362d941d2b_bpf_test_socket_sockopt+0x12b/0x132
bpf_prog_348c9b5faaf10092_skops_sockopt+0x954/0xe86
__cgroup_bpf_run_filter_sock_ops+0xbc/0x250
tcp_connect+0x879/0x1160
tcp_v6_connect+0x50c/0x870
mptcp_connect+0x129/0x280
__inet_stream_connect+0xce/0x370
inet_stream_connect+0x36/0x50
bpf_trampoline_6442491565+0x49/0xef
inet_stream_connect+0x5/0x50
__sys_connect+0x63/0x90
__x64_sys_connect+0x14/0x20

The root cause of the issue is that bpf allows accessing mptcp-level
proto_ops from a tcp subflow scope.

Fix the issue detecting the problematic call and preventing any action.

Reported-by: Alexei Starovoitov <alexei.starovoitov@gmail.com>
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/482
Fixes: 5684ab1a0eff ("mptcp: give rcvlowat some love")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/d8cb7d8476d66cb0812a6e29cd1e626869d9d53e.1711738080.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: cleanup SOL_TCP handling

Most TCP-level socket options get an integer from user space, and
set the corresponding field under the msk-level socket lock.

Reduce the code duplication moving suc

mptcp: cleanup SOL_TCP handling

Most TCP-level socket options get an integer from user space, and
set the corresponding field under the msk-level socket lock.

Reduce the code duplication moving such operations in the common code.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: implement TCP_NOTSENT_LOWAT support

Add support for such socket option storing the user-space provided
value in a new msk field, and using such data to implement the
_mptcp_stream_memory_free

mptcp: implement TCP_NOTSENT_LOWAT support

Add support for such socket option storing the user-space provided
value in a new msk field, and using such data to implement the
_mptcp_stream_memory_free() helper, similar to the TCP one.

To avoid adding more indirect calls in the fast path, open-code
a variant of sk_stream_memory_free() in mptcp_sendmsg() and add
direct calls to the mptcp stream memory free helper where possible.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/464
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: avoid some duplicate code in socket option handling

The mptcp_get_int_option() helper is needless open-coded in a
couple of places, replace the duplicate code with the helper
call.

Signed-of

mptcp: avoid some duplicate code in socket option handling

The mptcp_get_int_option() helper is needless open-coded in a
couple of places, replace the duplicate code with the helper
call.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: annotate lockless accesses around read-mostly fields

The following MPTCP socket fields:

- can_ack
- fully_established
- rcv_data_fin
- snd_data_fin_enable
- rcv_fastclose
- use_64bit_a

mptcp: annotate lockless accesses around read-mostly fields

The following MPTCP socket fields:

- can_ack
- fully_established
- rcv_data_fin
- snd_data_fin_enable
- rcv_fastclose
- use_64bit_ack

are accessed without any lock, add the appropriate annotation.

The schema is safe as each field can change its value at most
once in the whole mptcp socket life cycle.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: sockopt: support IP_LOCAL_PORT_RANGE and IP_BIND_ADDRESS_NO_PORT

Support for IP_BIND_ADDRESS_NO_PORT sockopt was introduced in [1].
Recently [2] allowed its value to be accessed without locki

mptcp: sockopt: support IP_LOCAL_PORT_RANGE and IP_BIND_ADDRESS_NO_PORT

Support for IP_BIND_ADDRESS_NO_PORT sockopt was introduced in [1].
Recently [2] allowed its value to be accessed without locking the
socket.

Support for (newer) IP_LOCAL_PORT_RANGE sockopt was introduced in [3].
In the same series a selftest was added in [4]. This selftest also
covers the IP_BIND_ADDRESS_NO_PORT sockopt.

This patch enables getsockopt()/setsockopt() on MPTCP sockets for these
socket options, syncing set values to subflows in sync_socket_options().
Ephemeral port range is synced to subflows, enabling NAT usecase
described in [3].

[1] commit 90c337da1524 ("inet: add IP_BIND_ADDRESS_NO_PORT to overcome
bind(0) limitations")
[2] commit ca571e2eb7eb ("inet: move inet->bind_address_no_port to
inet->inet_flags")
[3] commit 91d0b78c5177 ("inet: Add IP_LOCAL_PORT_RANGE socket option")
[4] commit ae5439658cce ("selftests/net: Cover the IP_LOCAL_PORT_RANGE
socket option")

Signed-off-by: Maxim Galaganov <max@internet.ru>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: rename mptcp_setsockopt_sol_ip_set_transparent()

Next patch extends this function so that it's not specific to
IP_TRANSPARENT. Change function name to mptcp_setsockopt_sol_ip_set().

Reviewed

mptcp: rename mptcp_setsockopt_sol_ip_set_transparent()

Next patch extends this function so that it's not specific to
IP_TRANSPARENT. Change function name to mptcp_setsockopt_sol_ip_set().

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Maxim Galaganov <max@internet.ru>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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mptcp: add mptcpi_subflows_total counter

If the initial subflow has been removed, we cannot know without checking
other counters, e.g. ss -ti <filter> | grep -c tcp-ulp-mptcp or
getsockopt(SOL_MPTCP

mptcp: add mptcpi_subflows_total counter

If the initial subflow has been removed, we cannot know without checking
other counters, e.g. ss -ti <filter> | grep -c tcp-ulp-mptcp or
getsockopt(SOL_MPTCP, MPTCP_FULL_INFO, ...) (or others except MPTCP_INFO
of course) and then check mptcp_subflow_data->num_subflows to get the
total amount of subflows.

This patch adds a new counter mptcpi_subflows_total in mptcpi_flags to
store the total amount of subflows, including the initial one. A new
helper __mptcp_has_initial_subflow() is added to check whether the
initial subflow has been removed or not. With this helper, we can then
compute the total amount of subflows from mptcp_info by doing something
like:

mptcpi_subflows_total = mptcpi_subflows +
__mptcp_has_initial_subflow(msk).

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/428
Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231128-send-net-next-2023107-v4-1-8d6b94150f6b@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: fix setsockopt(IP_TOS) subflow locking

The MPTCP implementation of the IP_TOS socket option uses the lockless
variant of the TOS manipulation helper and does not hold such lock at
the helper

mptcp: fix setsockopt(IP_TOS) subflow locking

The MPTCP implementation of the IP_TOS socket option uses the lockless
variant of the TOS manipulation helper and does not hold such lock at
the helper invocation time.

Add the required locking.

Fixes: ffcacff87cd6 ("mptcp: Support for IP_TOS for MPTCP setsockopt()")
Cc: stable@vger.kernel.org
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/457
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Matthieu Baerts <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20231114-upstream-net-20231113-mptcp-misc-fixes-6-7-rc2-v1-4-7b9cd6a7b7f4@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: use mptcp_check_fallback helper

Use __mptcp_check_fallback() helper defined in net/mptcp/protocol.h,
instead of open-coding it in both __mptcp_do_fallback() and
mptcp_diag_fill_info().

Revie

mptcp: use mptcp_check_fallback helper

Use __mptcp_check_fallback() helper defined in net/mptcp/protocol.h,
instead of open-coding it in both __mptcp_do_fallback() and
mptcp_diag_fill_info().

Reviewed-by: Matthieu Baerts <matttbe@kernel.org>
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231025-send-net-next-20231025-v1-5-db8f25f798eb@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: refactor sndbuf auto-tuning

The MPTCP protocol account for the data enqueued on all the subflows
to the main socket send buffer, while the send buffer auto-tuning
algorithm set the main socke

mptcp: refactor sndbuf auto-tuning

The MPTCP protocol account for the data enqueued on all the subflows
to the main socket send buffer, while the send buffer auto-tuning
algorithm set the main socket send buffer size as the max size among
the subflows.

That causes bad performances when at least one subflow is sndbuf
limited, e.g. due to very high latency, as the MPTCP scheduler can't
even fill such buffer.

Change the send-buffer auto-tuning algorithm to compute the main socket
send buffer size as the sum of all the subflows buffer size.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-9-9dc60939d371@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: ignore notsent_lowat setting at the subflow level

Any latency related tuning taking action at the subflow level does
not really affect the user-space, as only the main MPTCP socket is
relevan

mptcp: ignore notsent_lowat setting at the subflow level

Any latency related tuning taking action at the subflow level does
not really affect the user-space, as only the main MPTCP socket is
relevant.

Anyway any limiting setting may foul the MPTCP scheduler, not being
able to fully use the subflow-level cwin, leading to very poor b/w
usage.

Enforce notsent_lowat to be a no-op on every subflow.

Note that TCP_NOTSENT_LOWAT is currently not supported, and properly
dealing with that will require more invasive changes.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-8-9dc60939d371@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: consolidate sockopt synchronization

Move the socket option synchronization for active subflows
at subflow creation time. This allows removing the now unused
unlocked variant of such helper.

mptcp: consolidate sockopt synchronization

Move the socket option synchronization for active subflows
at subflow creation time. This allows removing the now unused
unlocked variant of such helper.

While at that, clean-up a bit the mptcp_subflow_create_socket()
errors path.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-7-9dc60939d371@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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mptcp: give rcvlowat some love

The MPTCP protocol allow setting sk_rcvlowat, but the value there
is currently ignored.

Additionally, the default subflows sk_rcvlowat basically disables per
subflow

mptcp: give rcvlowat some love

The MPTCP protocol allow setting sk_rcvlowat, but the value there
is currently ignored.

Additionally, the default subflows sk_rcvlowat basically disables per
subflow delayed ack: the MPTCP protocol move the incoming data from the
subflows into the msk socket as soon as the TCP stacks invokes the subflow
data_ready callback. Later, when __tcp_ack_snd_check() takes action,
the subflow-level copied_seq matches rcv_nxt, and that mandate for an
immediate ack.

Let the mptcp receive path be aware of such threshold, explicitly tracking
the amount of data available to be ready and checking vs sk_rcvlowat in
mptcp_poll() and before waking-up readers.

Additionally implement the set_rcvlowat() callback, to properly handle
the rcvbuf auto-tuning on sk_rcvlowat changes.

Finally to properly handle delayed ack, force the subflow level threshold
to 0 and instead explicitly ask for an immediate ack when the msk level th
is not reached.

Reviewed-by: Mat Martineau <martineau@kernel.org>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <martineau@kernel.org>
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-5-9dc60939d371@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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inet: lock the socket in ip_sock_set_tos()

Christoph Paasch reported a panic in TCP stack [1]

Indeed, we should not call sk_dst_reset() without holding
the socket lock, as __sk_dst_get() callers do

inet: lock the socket in ip_sock_set_tos()

Christoph Paasch reported a panic in TCP stack [1]

Indeed, we should not call sk_dst_reset() without holding
the socket lock, as __sk_dst_get() callers do not all rely
on bare RCU.

[1]
BUG: kernel NULL pointer dereference, address: 0000000000000000
PGD 12bad6067 P4D 12bad6067 PUD 12bad5067 PMD 0
Oops: 0000 [#1] PREEMPT SMP
CPU: 1 PID: 2750 Comm: syz-executor.5 Not tainted 6.6.0-rc4-g7a5720a344e7 #49
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.11.0-2.el7 04/01/2014
RIP: 0010:tcp_get_metrics+0x118/0x8f0 net/ipv4/tcp_metrics.c:321
Code: c7 44 24 70 02 00 8b 03 89 44 24 48 c7 44 24 4c 00 00 00 00 66 c7 44 24 58 02 00 66 ba 02 00 b1 01 89 4c 24 04 4c 89 7c 24 10 <49> 8b 0f 48 8b 89 50 05 00 00 48 89 4c 24 30 33 81 00 02 00 00 69
RSP: 0018:ffffc90000af79b8 EFLAGS: 00010293
RAX: 000000000100007f RBX: ffff88812ae8f500 RCX: ffff88812b5f8f01
RDX: 0000000000000002 RSI: ffffffff8300f080 RDI: 0000000000000002
RBP: 0000000000000002 R08: 0000000000000003 R09: ffffffff8205eca0
R10: 0000000000000002 R11: ffff88812b5f8f00 R12: ffff88812a9e0580
R13: 0000000000000000 R14: ffff88812ae8fbd2 R15: 0000000000000000
FS: 00007f70a006b640(0000) GS:ffff88813bd00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000000000000 CR3: 000000012bad7003 CR4: 0000000000170ee0
Call Trace:
<TASK>
tcp_fastopen_cache_get+0x32/0x140 net/ipv4/tcp_metrics.c:567
tcp_fastopen_cookie_check+0x28/0x180 net/ipv4/tcp_fastopen.c:419
tcp_connect+0x9c8/0x12a0 net/ipv4/tcp_output.c:3839
tcp_v4_connect+0x645/0x6e0 net/ipv4/tcp_ipv4.c:323
__inet_stream_connect+0x120/0x590 net/ipv4/af_inet.c:676
tcp_sendmsg_fastopen+0x2d6/0x3a0 net/ipv4/tcp.c:1021
tcp_sendmsg_locked+0x1957/0x1b00 net/ipv4/tcp.c:1073
tcp_sendmsg+0x30/0x50 net/ipv4/tcp.c:1336
__sock_sendmsg+0x83/0xd0 net/socket.c:730
__sys_sendto+0x20a/0x2a0 net/socket.c:2194
__do_sys_sendto net/socket.c:2206 [inline]

Fixes: e08d0b3d1723 ("inet: implement lockless IP_TOS")
Reported-by: Christoph Paasch <cpaasch@apple.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20231018090014.345158-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>

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inet: implement lockless IP_TOS

Some reads of inet->tos are racy.

Add needed READ_ONCE() annotations and convert IP_TOS option lockless.

v2: missing changes in include/net/route.h (David Ahern)

S

inet: implement lockless IP_TOS

Some reads of inet->tos are racy.

Add needed READ_ONCE() annotations and convert IP_TOS option lockless.

v2: missing changes in include/net/route.h (David Ahern)

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

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net: implement lockless SO_PRIORITY

This is a followup of 8bf43be799d4 ("net: annotate data-races
around sk->sk_priority").

sk->sk_priority can be read and written without holding the socket lock.

net: implement lockless SO_PRIORITY

This is a followup of 8bf43be799d4 ("net: annotate data-races
around sk->sk_priority").

sk->sk_priority can be read and written without holding the socket lock.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Wenjia Zhang <wenjia@linux.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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inet: move inet->transparent to inet->inet_flags

IP_TRANSPARENT socket option can now be set/read
without locking the socket.

v2: removed unused issk variable in mptcp_setsockopt_sol_ip_set_transpa

inet: move inet->transparent to inet->inet_flags

IP_TRANSPARENT socket option can now be set/read
without locking the socket.

v2: removed unused issk variable in mptcp_setsockopt_sol_ip_set_transparent()
v4: rebased after commit 3f326a821b99 ("mptcp: change the mpc check helper to return a sk")

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Paolo Abeni <pabeni@redhat.com>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

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