tcp/dccp: remove icsk->icsk_ack.timeout

icsk->icsk_ack.timeout can be replaced by icsk->csk_delack_timer.expires

This saves 8 bytes in TCP/DCCP sockets and helps for better cache locality.

Signed-

tcp/dccp: remove icsk->icsk_ack.timeout

icsk->icsk_ack.timeout can be replaced by icsk->csk_delack_timer.expires

This saves 8 bytes in TCP/DCCP sockets and helps for better cache locality.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp/dccp: remove icsk->icsk_timeout

icsk->icsk_timeout can be replaced by icsk->icsk_retransmit_timer.expires

This saves 8 bytes in TCP/DCCP sockets and helps for better cache locality.

Signed-off

tcp/dccp: remove icsk->icsk_timeout

icsk->icsk_timeout can be replaced by icsk->icsk_retransmit_timer.expires

This saves 8 bytes in TCP/DCCP sockets and helps for better cache locality.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp/dccp: Remove inet_connection_sock_af_ops.addr2sockaddr().

inet_connection_sock_af_ops.addr2sockaddr() hasn't been used at all
in the git era.

$ git grep addr2sockaddr $(git rev-list HEAD | ta

tcp/dccp: Remove inet_connection_sock_af_ops.addr2sockaddr().

inet_connection_sock_af_ops.addr2sockaddr() hasn't been used at all
in the git era.

$ git grep addr2sockaddr $(git rev-list HEAD | tail -n 1)

Let's remove it.

Note that there was a 4 bytes hole after sockaddr_len and now it's
6 bytes, so the binary layout is not changed.

Signed-off-by: Kuniyuki Iwashima <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: move icsk_clean_acked to a better location

As a followup of my presentation in Zagreb for netdev 0x19:

icsk_clean_acked is only used by TCP when/if CONFIG_TLS_DEVICE
is enabled from tcp_ack().

tcp: move icsk_clean_acked to a better location

As a followup of my presentation in Zagreb for netdev 0x19:

icsk_clean_acked is only used by TCP when/if CONFIG_TLS_DEVICE
is enabled from tcp_ack().

Rename it to tcp_clean_acked, move it to tcp_sock structure
in the tcp_sock_read_rx for better cache locality in TCP
fast path.

Define this field only when CONFIG_TLS_DEVICE is enabled
saving 8 bytes on configs not using it.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Neal Cardwell <[email protected]>
Reviewed-by: Sabrina Dubroca <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: cache RTAX_QUICKACK metric in a hot cache line

tcp_in_quickack_mode() is called from input path for small packets.

It calls __sk_dst_get() which reads sk->sk_dst_cache which has been
put in so

tcp: cache RTAX_QUICKACK metric in a hot cache line

tcp_in_quickack_mode() is called from input path for small packets.

It calls __sk_dst_get() which reads sk->sk_dst_cache which has been
put in sock_read_tx group (for good reasons).

Then dst_metric(dst, RTAX_QUICKACK) also needs extra cache line misses.

Cache RTAX_QUICKACK in icsk->icsk_ack.dst_quick_ack to no longer pull
these cache lines for the cases a delayed ACK is scheduled.

After this patch TCP receive path does not longer access sock_read_tx
group.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Jason Xing <[email protected]>
Reviewed-by: Neal Cardwell <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

tcp: add the ability to control max RTO

Currently, TCP stack uses a constant (120 seconds)
to limit the RTO value exponential growth.

Some applications want to set a lower value.

Add TCP_RTO_MAX_M

tcp: add the ability to control max RTO

Currently, TCP stack uses a constant (120 seconds)
to limit the RTO value exponential growth.

Some applications want to set a lower value.

Add TCP_RTO_MAX_MS socket option to set a value (in ms)
between 1 and 120 seconds.

It is discouraged to change the socket rto max on a live
socket, as it might lead to unexpected disconnects.

Following patch is adding a netns sysctl to control the
default value at socket creation time.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Jason Xing <[email protected]>
Reviewed-by: Neal Cardwell <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

tcp: rename inet_csk_{delete|reset}_keepalive_timer()

inet_csk_delete_keepalive_timer() and inet_csk_reset_keepalive_timer()
are only used from core TCP, there is no need to export them.

Replace th

tcp: rename inet_csk_{delete|reset}_keepalive_timer()

inet_csk_delete_keepalive_timer() and inet_csk_reset_keepalive_timer()
are only used from core TCP, there is no need to export them.

Replace their prefix by tcp.

Move them to net/ipv4/tcp_timer.c and make tcp_delete_keepalive_timer()
static.

Signed-off-by: Eric Dumazet <[email protected]>
Reviewed-by: Jason Xing <[email protected]>
Reviewed-by: Joe Damato <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp/dccp: allow a connection when sk_max_ack_backlog is zero

If the backlog of listen() is set to zero, sk_acceptq_is_full() allows
one connection to be made, but inet_csk_reqsk_queue_is_full() does

tcp/dccp: allow a connection when sk_max_ack_backlog is zero

If the backlog of listen() is set to zero, sk_acceptq_is_full() allows
one connection to be made, but inet_csk_reqsk_queue_is_full() does not.
When the net.ipv4.tcp_syncookies is zero, inet_csk_reqsk_queue_is_full()
will cause an immediate drop before the sk_acceptq_is_full() check in
tcp_conn_request(), resulting in no connection can be made.

This patch tries to keep consistent with 64a146513f8f ("[NET]: Revert
incorrect accept queue backlog changes.").

Link: https://lore.kernel.org/netdev/[email protected]/
Fixes: ef547f2ac16b ("tcp: remove max_qlen_log")
Signed-off-by: Zhongqiu Duan <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Reviewed-by: Jason Xing <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: add a fast path in tcp_delack_timer()

delack timer is not stopped from inet_csk_clear_xmit_timer()
because we do not define INET_CSK_CLEAR_TIMERS.

This is a conscious choice : inet_csk_clear_x

tcp: add a fast path in tcp_delack_timer()

delack timer is not stopped from inet_csk_clear_xmit_timer()
because we do not define INET_CSK_CLEAR_TIMERS.

This is a conscious choice : inet_csk_clear_xmit_timer()
is often called from another cpu. Calling del_timer()
would cause false sharing and lock contention.

This means that very often, tcp_delack_timer() is called
at the timer expiration, while there is no ACK to transmit.

This can be detected very early, avoiding the socket spinlock.

Notes:
- test about tp->compressed_ack is racy,
but in the unlikely case there is a race, the dedicated
compressed_ack_timer hrtimer would close it.

- Even if the fast path is not taken, reading
icsk->icsk_ack.pending and tp->compressed_ack
before acquiring the socket spinlock reduces
acquisition time and chances of contention.

Signed-off-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: annotate data-races around icsk->icsk_pending

icsk->icsk_pending can be read locklessly already.

Following patch in the series will add another lockless read.

Add smp_load_acquire() and smp_s

tcp: annotate data-races around icsk->icsk_pending

icsk->icsk_pending can be read locklessly already.

Following patch in the series will add another lockless read.

Add smp_load_acquire() and smp_store_release() annotations
because following patch will add a test in tcp_write_timer(),
and READ_ONCE()/WRITE_ONCE() alone would possibly lead to races.

Signed-off-by: Eric Dumazet <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

Fix race for duplicate reqsk on identical SYN

When bonding is configured in BOND_MODE_BROADCAST mode, if two identical
SYN packets are received at the same time and processed on different CPUs,
it c

Fix race for duplicate reqsk on identical SYN

When bonding is configured in BOND_MODE_BROADCAST mode, if two identical
SYN packets are received at the same time and processed on different CPUs,
it can potentially create the same sk (sock) but two different reqsk
(request_sock) in tcp_conn_request().

These two different reqsk will respond with two SYNACK packets, and since
the generation of the seq (ISN) incorporates a timestamp, the final two
SYNACK packets will have different seq values.

The consequence is that when the Client receives and replies with an ACK
to the earlier SYNACK packet, we will reset(RST) it.

========================================================================

This behavior is consistently reproducible in my local setup,
which comprises:

| NETA1 ------ NETB1 |
PC_A --- bond --- | | --- bond --- PC_B
| NETA2 ------ NETB2 |

- PC_A is the Server and has two network cards, NETA1 and NETA2. I have
bonded these two cards using BOND_MODE_BROADCAST mode and configured
them to be handled by different CPU.

- PC_B is the Client, also equipped with two network cards, NETB1 and
NETB2, which are also bonded and configured in BOND_MODE_BROADCAST mode.

If the client attempts a TCP connection to the server, it might encounter
a failure. Capturing packets from the server side reveals:

10.10.10.10.45182 > localhost: Flags [S], seq 320236027,
10.10.10.10.45182 > localhost: Flags [S], seq 320236027,
localhost > 10.10.10.10.45182: Flags [S.], seq 2967855116,
localhost > 10.10.10.10.45182: Flags [S.], seq 2967855123, <==
10.10.10.10.45182 > localhost: Flags [.], ack 4294967290,
10.10.10.10.45182 > localhost: Flags [.], ack 4294967290,
localhost > 10.10.10.10.45182: Flags [R], seq 2967855117, <==
localhost > 10.10.10.10.45182: Flags [R], seq 2967855117,

Two SYNACKs with different seq numbers are sent by localhost,
resulting in an anomaly.

========================================================================

The attempted solution is as follows:
Add a return value to inet_csk_reqsk_queue_hash_add() to confirm if the
ehash insertion is successful (Up to now, the reason for unsuccessful
insertion is that a reqsk for the same connection has already been
inserted). If the insertion fails, release the reqsk.

Due to the refcnt, Kuniyuki suggests also adding a return value check
for the DCCP module; if ehash insertion fails, indicating a successful
insertion of the same connection, simply release the reqsk as well.

Simultaneously, In the reqsk_queue_hash_req(), the start of the
req->rsk_timer is adjusted to be after successful insertion.

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: luoxuanqiang <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Paolo Abeni <[email protected]>

show more ...

net: change proto and proto_ops accept type

Rather than pass in flags, error pointer, and whether this is a kernel
invocation or not, add a struct proto_accept_arg struct as the argument.
This then

net: change proto and proto_ops accept type

Rather than pass in flags, error pointer, and whether this is a kernel
invocation or not, add a struct proto_accept_arg struct as the argument.
This then holds all of these arguments, and prepares accept for being
able to pass back more information.

No functional changes in this patch.

Acked-by: Jakub Kicinski <[email protected]>
Signed-off-by: Jens Axboe <[email protected]>

show more ...

tcp/dccp: complete lockless accesses to sk->sk_max_ack_backlog

Since commit 099ecf59f05b ("net: annotate lockless accesses to
sk->sk_max_ack_backlog") decided to handle the sk_max_ack_backlog
lockle

tcp/dccp: complete lockless accesses to sk->sk_max_ack_backlog

Since commit 099ecf59f05b ("net: annotate lockless accesses to
sk->sk_max_ack_backlog") decided to handle the sk_max_ack_backlog
locklessly, there is one more function mostly called in TCP/DCCP
cases. So this patch completes it:)

Signed-off-by: Jason Xing <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

inet: preserve const qualifier in inet_csk()

We can change inet_csk() to propagate its argument const qualifier,
thanks to container_of_const().

We have to fix few places that had mistakes, like tc

inet: preserve const qualifier in inet_csk()

We can change inet_csk() to propagate its argument const qualifier,
thanks to container_of_const().

We have to fix few places that had mistakes, like tcp_bound_rto().

Signed-off-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: properly terminate timers for kernel sockets

We had various syzbot reports about tcp timers firing after
the corresponding netns has been dismantled.

Fortunately Josef Bacik could trigger the

tcp: properly terminate timers for kernel sockets

We had various syzbot reports about tcp timers firing after
the corresponding netns has been dismantled.

Fortunately Josef Bacik could trigger the issue more often,
and could test a patch I wrote two years ago.

When TCP sockets are closed, we call inet_csk_clear_xmit_timers()
to 'stop' the timers.

inet_csk_clear_xmit_timers() can be called from any context,
including when socket lock is held.
This is the reason it uses sk_stop_timer(), aka del_timer().
This means that ongoing timers might finish much later.

For user sockets, this is fine because each running timer
holds a reference on the socket, and the user socket holds
a reference on the netns.

For kernel sockets, we risk that the netns is freed before
timer can complete, because kernel sockets do not hold
reference on the netns.

This patch adds inet_csk_clear_xmit_timers_sync() function
that using sk_stop_timer_sync() to make sure all timers
are terminated before the kernel socket is released.
Modules using kernel sockets close them in their netns exit()
handler.

Also add sock_not_owned_by_me() helper to get LOCKDEP
support : inet_csk_clear_xmit_timers_sync() must not be called
while socket lock is held.

It is very possible we can revert in the future commit
3a58f13a881e ("net: rds: acquire refcount on TCP sockets")
which attempted to solve the issue in rds only.
(net/smc/af_smc.c and net/mptcp/subflow.c have similar code)

We probably can remove the check_net() tests from
tcp_out_of_resources() and __tcp_close() in the future.

Reported-by: Josef Bacik <[email protected]>
Closes: https://lore.kernel.org/netdev/20240314210740.GA2823176@perftesting/
Fixes: 26abe14379f8 ("net: Modify sk_alloc to not reference count the netns of kernel sockets.")
Fixes: 8a68173691f0 ("net: sk_clone_lock() should only do get_net() if the parent is not a kernel socket")
Link: https://lore.kernel.org/bpf/CANn89i+484ffqb93aQm1N-tjxxvb3WDKX0EbD7318RwRgsatjw@mail.gmail.com/
Signed-off-by: Eric Dumazet <[email protected]>
Tested-by: Josef Bacik <[email protected]>
Cc: Tetsuo Handa <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: make sure init the accept_queue's spinlocks once

When I run syz's reproduction C program locally, it causes the following
issue:
pvqspinlock: lock 0xffff9d181cd5c660 has corrupted value 0x0!
WA

tcp: make sure init the accept_queue's spinlocks once

When I run syz's reproduction C program locally, it causes the following
issue:
pvqspinlock: lock 0xffff9d181cd5c660 has corrupted value 0x0!
WARNING: CPU: 19 PID: 21160 at __pv_queued_spin_unlock_slowpath (kernel/locking/qspinlock_paravirt.h:508)
Hardware name: Red Hat KVM, BIOS 0.5.1 01/01/2011
RIP: 0010:__pv_queued_spin_unlock_slowpath (kernel/locking/qspinlock_paravirt.h:508)
Code: 73 56 3a ff 90 c3 cc cc cc cc 8b 05 bb 1f 48 01 85 c0 74 05 c3 cc cc cc cc 8b 17 48 89 fe 48 c7 c7
30 20 ce 8f e8 ad 56 42 ff <0f> 0b c3 cc cc cc cc 0f 0b 0f 1f 40 00 90 90 90 90 90 90 90 90 90
RSP: 0018:ffffa8d200604cb8 EFLAGS: 00010282
RAX: 0000000000000000 RBX: 0000000000000000 RCX: ffff9d1ef60e0908
RDX: 00000000ffffffd8 RSI: 0000000000000027 RDI: ffff9d1ef60e0900
RBP: ffff9d181cd5c280 R08: 0000000000000000 R09: 00000000ffff7fff
R10: ffffa8d200604b68 R11: ffffffff907dcdc8 R12: 0000000000000000
R13: ffff9d181cd5c660 R14: ffff9d1813a3f330 R15: 0000000000001000
FS: 00007fa110184640(0000) GS:ffff9d1ef60c0000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 0000000020000000 CR3: 000000011f65e000 CR4: 00000000000006f0
Call Trace:
<IRQ>
_raw_spin_unlock (kernel/locking/spinlock.c:186)
inet_csk_reqsk_queue_add (net/ipv4/inet_connection_sock.c:1321)
inet_csk_complete_hashdance (net/ipv4/inet_connection_sock.c:1358)
tcp_check_req (net/ipv4/tcp_minisocks.c:868)
tcp_v4_rcv (net/ipv4/tcp_ipv4.c:2260)
ip_protocol_deliver_rcu (net/ipv4/ip_input.c:205)
ip_local_deliver_finish (net/ipv4/ip_input.c:234)
__netif_receive_skb_one_core (net/core/dev.c:5529)
process_backlog (./include/linux/rcupdate.h:779)
__napi_poll (net/core/dev.c:6533)
net_rx_action (net/core/dev.c:6604)
__do_softirq (./arch/x86/include/asm/jump_label.h:27)
do_softirq (kernel/softirq.c:454 kernel/softirq.c:441)
</IRQ>
<TASK>
__local_bh_enable_ip (kernel/softirq.c:381)
__dev_queue_xmit (net/core/dev.c:4374)
ip_finish_output2 (./include/net/neighbour.h:540 net/ipv4/ip_output.c:235)
__ip_queue_xmit (net/ipv4/ip_output.c:535)
__tcp_transmit_skb (net/ipv4/tcp_output.c:1462)
tcp_rcv_synsent_state_process (net/ipv4/tcp_input.c:6469)
tcp_rcv_state_process (net/ipv4/tcp_input.c:6657)
tcp_v4_do_rcv (net/ipv4/tcp_ipv4.c:1929)
__release_sock (./include/net/sock.h:1121 net/core/sock.c:2968)
release_sock (net/core/sock.c:3536)
inet_wait_for_connect (net/ipv4/af_inet.c:609)
__inet_stream_connect (net/ipv4/af_inet.c:702)
inet_stream_connect (net/ipv4/af_inet.c:748)
__sys_connect (./include/linux/file.h:45 net/socket.c:2064)
__x64_sys_connect (net/socket.c:2073 net/socket.c:2070 net/socket.c:2070)
do_syscall_64 (arch/x86/entry/common.c:51 arch/x86/entry/common.c:82)
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:129)
RIP: 0033:0x7fa10ff05a3d
Code: 5b 41 5c c3 66 0f 1f 84 00 00 00 00 00 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89
c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 8b 0d ab a3 0e 00 f7 d8 64 89 01 48
RSP: 002b:00007fa110183de8 EFLAGS: 00000202 ORIG_RAX: 000000000000002a
RAX: ffffffffffffffda RBX: 0000000020000054 RCX: 00007fa10ff05a3d
RDX: 000000000000001c RSI: 0000000020000040 RDI: 0000000000000003
RBP: 00007fa110183e20 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000202 R12: 00007fa110184640
R13: 0000000000000000 R14: 00007fa10fe8b060 R15: 00007fff73e23b20
</TASK>

The issue triggering process is analyzed as follows:
Thread A Thread B
tcp_v4_rcv //receive ack TCP packet inet_shutdown
tcp_check_req tcp_disconnect //disconnect sock
... tcp_set_state(sk, TCP_CLOSE)
inet_csk_complete_hashdance ...
inet_csk_reqsk_queue_add inet_listen //start listen
spin_lock(&queue->rskq_lock) inet_csk_listen_start
... reqsk_queue_alloc
... spin_lock_init
spin_unlock(&queue->rskq_lock) //warning

When the socket receives the ACK packet during the three-way handshake,
it will hold spinlock. And then the user actively shutdowns the socket
and listens to the socket immediately, the spinlock will be initialized.
When the socket is going to release the spinlock, a warning is generated.
Also the same issue to fastopenq.lock.

Move init spinlock to inet_create and inet_accept to make sure init the
accept_queue's spinlocks once.

Fixes: fff1f3001cc5 ("tcp: add a spinlock to protect struct request_sock_queue")
Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path")
Reported-by: Ming Shu <[email protected]>
Signed-off-by: Zhengchao Shao <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

ipv6: drop feature RTAX_FEATURE_ALLFRAG

RTAX_FEATURE_ALLFRAG was added before the first git commit:

https://www.mail-archive.com/[email protected]/msg03399.html

The feature would sen

ipv6: drop feature RTAX_FEATURE_ALLFRAG

RTAX_FEATURE_ALLFRAG was added before the first git commit:

https://www.mail-archive.com/[email protected]/msg03399.html

The feature would send packets to the fragmentation path if a box
receives a PMTU value with less than 1280 byte. However, since commit
9d289715eb5c ("ipv6: stop sending PTB packets for MTU < 1280"), such
message would be simply discarded. The feature flag is neither supported
in iproute2 utility. In theory one can still manipulate it with direct
netlink message, but it is not ideal because it was based on obsoleted
guidance of RFC-2460 (replaced by RFC-8200).

The feature would always test false at the moment, so remove related
code or mark them as unused.

Signed-off-by: Yan Zhai <[email protected]>
Reviewed-by: Florian Westphal <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/d78e44dcd9968a252143ffe78460446476a472a1.1698156966.git.yan@cloudflare.com
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: Set pingpong threshold via sysctl

TCP pingpong threshold is 1 by default. But some applications, like SQL DB
may prefer a higher pingpong threshold to activate delayed acks in quick
ack mode fo

tcp: Set pingpong threshold via sysctl

TCP pingpong threshold is 1 by default. But some applications, like SQL DB
may prefer a higher pingpong threshold to activate delayed acks in quick
ack mode for better performance.

The pingpong threshold and related code were changed to 3 in the year
2019 in:
commit 4a41f453bedf ("tcp: change pingpong threshold to 3")
And reverted to 1 in the year 2022 in:
commit 4d8f24eeedc5 ("Revert "tcp: change pingpong threshold to 3"")

There is no single value that fits all applications.
Add net.ipv4.tcp_pingpong_thresh sysctl tunable, so it can be tuned for
optimal performance based on the application needs.

Signed-off-by: Haiyang Zhang <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Acked-by: Neal Cardwell <[email protected]>
Reviewed-by: Kuniyuki Iwashima <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

show more ...

tcp: record last received ipv6 flowlabel

In order to better estimate whether a data packet has been
retransmitted or is the result of a TLP, we save the last received
ipv6 flowlabel.

To make space

tcp: record last received ipv6 flowlabel

In order to better estimate whether a data packet has been
retransmitted or is the result of a TLP, we save the last received
ipv6 flowlabel.

To make space for this field we resize the "ato" field in
inet_connection_sock as the current value of TCP_DELACK_MAX can be
fully contained in 8 bits and add a compile_time_assert ensuring this
field is the required size.

v2: addressed kernel bot feedback about dccp_delack_timer()
v3: addressed build error introduced by commit bbf80d713fe7 ("tcp:
derive delack_max from rto_min")

Signed-off-by: David Morley <[email protected]>
Signed-off-by: Neal Cardwell <[email protected]>
Signed-off-by: Yuchung Cheng <[email protected]>
Tested-by: David Morley <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Signed-off-by: Paolo Abeni <[email protected]>

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inet: move inet->is_icsk to inet->inet_flags

We move single bit fields to inet->inet_flags to avoid races.

Signed-off-by: Eric Dumazet <[email protected]>
Acked-by: Soheil Hassas Yeganeh <soheil@

inet: move inet->is_icsk to inet->inet_flags

We move single bit fields to inet->inet_flags to avoid races.

Signed-off-by: Eric Dumazet <[email protected]>
Acked-by: Soheil Hassas Yeganeh <[email protected]>
Reviewed-by: Simon Horman <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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net: tcp: send zero-window ACK when no memory

For now, skb will be dropped when no memory, which makes client keep
retrans util timeout and it's not friendly to the users.

In this patch, we reply a

net: tcp: send zero-window ACK when no memory

For now, skb will be dropped when no memory, which makes client keep
retrans util timeout and it's not friendly to the users.

In this patch, we reply an ACK with zero-window in this case to update
the snd_wnd of the sender to 0. Therefore, the sender won't timeout the
connection and will probe the zero-window with the retransmits.

Signed-off-by: Menglong Dong <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

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net: Add a bhash2 table hashed by port and address

The current bind hashtable (bhash) is hashed by port only.
In the socket bind path, we have to check for bind conflicts by
traversing the specified

net: Add a bhash2 table hashed by port and address

The current bind hashtable (bhash) is hashed by port only.
In the socket bind path, we have to check for bind conflicts by
traversing the specified port's inet_bind_bucket while holding the
hashbucket's spinlock (see inet_csk_get_port() and
inet_csk_bind_conflict()). In instances where there are tons of
sockets hashed to the same port at different addresses, the bind
conflict check is time-intensive and can cause softirq cpu lockups,
as well as stops new tcp connections since __inet_inherit_port()
also contests for the spinlock.

This patch adds a second bind table, bhash2, that hashes by
port and sk->sk_rcv_saddr (ipv4) and sk->sk_v6_rcv_saddr (ipv6).
Searching the bhash2 table leads to significantly faster conflict
resolution and less time holding the hashbucket spinlock.

Please note a few things:
* There can be the case where the a socket's address changes after it
has been bound. There are two cases where this happens:

1) The case where there is a bind() call on INADDR_ANY (ipv4) or
IPV6_ADDR_ANY (ipv6) and then a connect() call. The kernel will
assign the socket an address when it handles the connect()

2) In inet_sk_reselect_saddr(), which is called when rebuilding the
sk header and a few pre-conditions are met (eg rerouting fails).

In these two cases, we need to update the bhash2 table by removing the
entry for the old address, and add a new entry reflecting the updated
address.

* The bhash2 table must have its own lock, even though concurrent
accesses on the same port are protected by the bhash lock. Bhash2 must
have its own lock to protect against cases where sockets on different
ports hash to different bhash hashbuckets but to the same bhash2
hashbucket.

This brings up a few stipulations:
1) When acquiring both the bhash and the bhash2 lock, the bhash2 lock
will always be acquired after the bhash lock and released before the
bhash lock is released.

2) There are no nested bhash2 hashbucket locks. A bhash2 lock is always
acquired+released before another bhash2 lock is acquired+released.

* The bhash table cannot be superseded by the bhash2 table because for
bind requests on INADDR_ANY (ipv4) or IPV6_ADDR_ANY (ipv6), every socket
bound to that port must be checked for a potential conflict. The bhash
table is the only source of port->socket associations.

Signed-off-by: Joanne Koong <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>

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Revert "tcp: change pingpong threshold to 3"

This reverts commit 4a41f453bedfd5e9cd040bad509d9da49feb3e2c.

This to-be-reverted commit was meant to apply a stricter rule for the
stack to enter pingp

Revert "tcp: change pingpong threshold to 3"

This reverts commit 4a41f453bedfd5e9cd040bad509d9da49feb3e2c.

This to-be-reverted commit was meant to apply a stricter rule for the
stack to enter pingpong mode. However, the condition used to check for
interactive session "before(tp->lsndtime, icsk->icsk_ack.lrcvtime)" is
jiffy based and might be too coarse, which delays the stack entering
pingpong mode.
We revert this patch so that we no longer use the above condition to
determine interactive session, and also reduce pingpong threshold to 1.

Fixes: 4a41f453bedf ("tcp: change pingpong threshold to 3")
Reported-by: LemmyHuang <[email protected]>
Suggested-by: Neal Cardwell <[email protected]>
Signed-off-by: Wei Wang <[email protected]>
Acked-by: Neal Cardwell <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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Revert "net: Add a second bind table hashed by port and address"

This reverts:

commit d5a42de8bdbe ("net: Add a second bind table hashed by port and address")
commit 538aaf9b2383 ("selftests: Add t

Revert "net: Add a second bind table hashed by port and address"

This reverts:

commit d5a42de8bdbe ("net: Add a second bind table hashed by port and address")
commit 538aaf9b2383 ("selftests: Add test for timing a bind request to a port with a populated bhash entry")
Link: https://lore.kernel.org/netdev/[email protected]/

There are a few things that need to be fixed here:
* Updating bhash2 in cases where the socket's rcv saddr changes
* Adding bhash2 hashbucket locks

Links to syzbot reports:
https://lore.kernel.org/netdev/[email protected]/
https://lore.kernel.org/netdev/[email protected]/

Fixes: d5a42de8bdbe ("net: Add a second bind table hashed by port and address")
Reported-by: [email protected]
Reported-by: [email protected]
Reported-by: [email protected]
Signed-off-by: Joanne Koong <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jakub Kicinski <[email protected]>

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net: Add a second bind table hashed by port and address

We currently have one tcp bind table (bhash) which hashes by port
number only. In the socket bind path, we check for bind conflicts by
travers

net: Add a second bind table hashed by port and address

We currently have one tcp bind table (bhash) which hashes by port
number only. In the socket bind path, we check for bind conflicts by
traversing the specified port's inet_bind2_bucket while holding the
bucket's spinlock (see inet_csk_get_port() and inet_csk_bind_conflict()).

In instances where there are tons of sockets hashed to the same port
at different addresses, checking for a bind conflict is time-intensive
and can cause softirq cpu lockups, as well as stops new tcp connections
since __inet_inherit_port() also contests for the spinlock.

This patch proposes adding a second bind table, bhash2, that hashes by
port and ip address. Searching the bhash2 table leads to significantly
faster conflict resolution and less time holding the spinlock.

Signed-off-by: Joanne Koong <[email protected]>
Reviewed-by: Eric Dumazet <[email protected]>
Acked-by: Kuniyuki Iwashima <[email protected]>
Signed-off-by: Jakub Kicinski <[email protected]>

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