The mentioned MIB is currently incremented even when a packet
with an old sequence number (i.e. a zero window probe) is received,
which is IMHO misleading.
Explicitly restrict such MIB increment at the relevant events.
Fixes: 6c758062c6 ("tcp: add LINUX_MIB_BEYOND_WINDOW")
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Link: https://patch.msgid.link/20d147292eb4b13b6535e0ad6f56be64d9c330d3.1753118029.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The nipa CI is reporting frequent failures in the mptcp_connect
self-tests.
In the failing scenarios (TCP -> MPTCP) the involved sockets are
actually plain TCP ones, as fallback for passive socket at 2whs
time cause the MPTCP listener to actually create a TCP socket.
The transfer is stuck due to the receiver buffer being zero.
With the stronger check in place, tcp_clamp_window() can be invoked
while the TCP socket has sk_rmem_alloc == 0, and the receive buffer
will be zeroed, too.
Check for the critical condition in tcp_prune_queue() and just
drop the packet without shrinking the receiver buffer.
Fixes: 1d2fbaad7c ("tcp: stronger sk_rcvbuf checks")
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20c18165d3f848e1c5c1b782d88c1a5ab38b3f70.1753118029.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The CI reported a UaF in tcp_prune_ofo_queue():
BUG: KASAN: slab-use-after-free in tcp_prune_ofo_queue+0x55d/0x660
Read of size 4 at addr ffff8880134729d8 by task socat/20348
CPU: 0 UID: 0 PID: 20348 Comm: socat Not tainted 6.16.0-rc5-virtme #1 PREEMPT(full)
Hardware name: Bochs Bochs, BIOS Bochs 01/01/2011
Call Trace:
<TASK>
dump_stack_lvl+0x82/0xd0
print_address_description.constprop.0+0x2c/0x400
print_report+0xb4/0x270
kasan_report+0xca/0x100
tcp_prune_ofo_queue+0x55d/0x660
tcp_try_rmem_schedule+0x855/0x12e0
tcp_data_queue+0x4dd/0x2260
tcp_rcv_established+0x5e8/0x2370
tcp_v4_do_rcv+0x4ba/0x8c0
__release_sock+0x27a/0x390
release_sock+0x53/0x1d0
tcp_sendmsg+0x37/0x50
sock_write_iter+0x3c1/0x520
vfs_write+0xc09/0x1210
ksys_write+0x183/0x1d0
do_syscall_64+0xc1/0x380
entry_SYSCALL_64_after_hwframe+0x77/0x7f
RIP: 0033:0x7fcf73ef2337
Code: 0f 00 f7 d8 64 89 02 48 c7 c0 ff ff ff ff eb b7 0f 1f 00 f3 0f 1e fa 64 8b 04 25 18 00 00 00 85 c0 75 10 b8 01 00 00 00 0f 05 <48> 3d 00 f0 ff ff 77 51 c3 48 83 ec 28 48 89 54 24 18 48 89 74 24
RSP: 002b:00007ffd4f924708 EFLAGS: 00000246 ORIG_RAX: 0000000000000001
RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fcf73ef2337
RDX: 0000000000002000 RSI: 0000555f11d1a000 RDI: 0000000000000008
RBP: 0000555f11d1a000 R08: 0000000000002000 R09: 0000000000000000
R10: 0000000000000040 R11: 0000000000000246 R12: 0000000000000008
R13: 0000000000002000 R14: 0000555ee1a44570 R15: 0000000000002000
</TASK>
Allocated by task 20348:
kasan_save_stack+0x24/0x50
kasan_save_track+0x14/0x30
__kasan_slab_alloc+0x59/0x70
kmem_cache_alloc_node_noprof+0x110/0x340
__alloc_skb+0x213/0x2e0
tcp_collapse+0x43f/0xff0
tcp_try_rmem_schedule+0x6b9/0x12e0
tcp_data_queue+0x4dd/0x2260
tcp_rcv_established+0x5e8/0x2370
tcp_v4_do_rcv+0x4ba/0x8c0
__release_sock+0x27a/0x390
release_sock+0x53/0x1d0
tcp_sendmsg+0x37/0x50
sock_write_iter+0x3c1/0x520
vfs_write+0xc09/0x1210
ksys_write+0x183/0x1d0
do_syscall_64+0xc1/0x380
entry_SYSCALL_64_after_hwframe+0x77/0x7f
Freed by task 20348:
kasan_save_stack+0x24/0x50
kasan_save_track+0x14/0x30
kasan_save_free_info+0x3b/0x60
__kasan_slab_free+0x38/0x50
kmem_cache_free+0x149/0x330
tcp_prune_ofo_queue+0x211/0x660
tcp_try_rmem_schedule+0x855/0x12e0
tcp_data_queue+0x4dd/0x2260
tcp_rcv_established+0x5e8/0x2370
tcp_v4_do_rcv+0x4ba/0x8c0
__release_sock+0x27a/0x390
release_sock+0x53/0x1d0
tcp_sendmsg+0x37/0x50
sock_write_iter+0x3c1/0x520
vfs_write+0xc09/0x1210
ksys_write+0x183/0x1d0
do_syscall_64+0xc1/0x380
entry_SYSCALL_64_after_hwframe+0x77/0x7f
The buggy address belongs to the object at ffff888013472900
which belongs to the cache skbuff_head_cache of size 232
The buggy address is located 216 bytes inside of
freed 232-byte region [ffff888013472900, ffff8880134729e8)
The buggy address belongs to the physical page:
page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x13472
head: order:1 mapcount:0 entire_mapcount:0 nr_pages_mapped:0 pincount:0
flags: 0x80000000000040(head|node=0|zone=1)
page_type: f5(slab)
raw: 0080000000000040 ffff88800198fb40 ffffea0000347b10 ffffea00004f5290
raw: 0000000000000000 0000000000120012 00000000f5000000 0000000000000000
head: 0080000000000040 ffff88800198fb40 ffffea0000347b10 ffffea00004f5290
head: 0000000000000000 0000000000120012 00000000f5000000 0000000000000000
head: 0080000000000001 ffffea00004d1c81 00000000ffffffff 00000000ffffffff
head: 0000000000000000 0000000000000000 00000000ffffffff 0000000000000000
page dumped because: kasan: bad access detected
Memory state around the buggy address:
ffff888013472880: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888013472900: fa fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
>ffff888013472980: fb fb fb fb fb fb fb fb fb fb fb fb fb fc fc fc
^
ffff888013472a00: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
ffff888013472a80: fc fc fc fc fc fc fc fc fa fb fb fb fb fb fb fb
Indeed tcp_prune_ofo_queue() is reusing the skb dropped a few lines
above. The caller wants to enqueue 'in_skb', lets check space vs the
latter.
Fixes: 1d2fbaad7c ("tcp: stronger sk_rcvbuf checks")
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Tested-by: syzbot+865aca08c0533171bf6a@syzkaller.appspotmail.com
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/b78d2d9bdccca29021eed9a0e7097dd8dc00f485.1752567053.git.pabeni@redhat.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently, TCP stack accepts incoming packet if sizes of receive queues
are below sk->sk_rcvbuf limit.
This can cause memory overshoot if the packet is big, like an 1/2 MB
BIG TCP one.
Refine the check to take into account the incoming skb truesize.
Note that we still accept the packet if the receive queue is empty,
to not completely freeze TCP flows in pathological conditions.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250711114006.480026-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
These functions to not modify the skb, add a const qualifier.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250711114006.480026-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcp_measure_rcv_mss() is used to update icsk->icsk_ack.rcv_mss
(tcpi_rcv_mss in tcp_info) and tp->scaling_ratio.
Calling it from tcp_data_queue_ofo() makes sure these
fields are updated, and permits a better tuning
of sk->sk_rcvbuf, in the case a new flow receives many ooo
packets.
Fixes: dfa2f04833 ("tcp: get rid of sysctl_tcp_adv_win_scale")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250711114006.480026-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Add a new SNMP MIB : LINUX_MIB_BEYOND_WINDOW
Incremented when an incoming packet is received beyond the
receiver window.
nstat -az | grep TcpExtBeyondWindow
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250711114006.480026-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Currently, TCP accepts incoming packets which might go beyond the
offered RWIN.
Add to tcp_sequence() the validation of packet end sequence.
Add the corresponding check in the fast path.
We relax this new constraint if the receive queue is empty,
to not freeze flows from buggy peers.
Add a new drop reason : SKB_DROP_REASON_TCP_INVALID_END_SEQUENCE.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250711114006.480026-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
When a passive flow has not been accepted yet, it is
not wise to increase sk_rcvbuf when receiving ooo packets.
A very busy server might tune down tcp_rmem[1] to better
control how much memory can be used by sockets waiting
in its listeners accept queues.
Fixes: 63ad7dfedf ("tcp: adjust rcvbuf in presence of reorders")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250707213900.1543248-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
As RACK-TLP was published as a standards-track RFC8985,
so the outdated ref draft-ietf-tcpm-rack need to be updated.
Signed-off-by: Xin Guo <guoxin0309@gmail.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20250705163647.301231-1-guoxin0309@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
If the new coming segment covers more than one skbs in the ofo queue,
and which seq is equal to rcv_nxt, then the sequence range
that is duplicated will be sent as DUP SACK, the detail as below,
in step6, the {501,2001} range is clearly including too much
DUP SACK range, in violation of RFC 2883 rules.
1. client > server: Flags [.], seq 501:1001, ack 1325288529, win 20000, length 500
2. server > client: Flags [.], ack 1, [nop,nop,sack 1 {501:1001}], length 0
3. client > server: Flags [.], seq 1501:2001, ack 1325288529, win 20000, length 500
4. server > client: Flags [.], ack 1, [nop,nop,sack 2 {1501:2001} {501:1001}], length 0
5. client > server: Flags [.], seq 1:2001, ack 1325288529, win 20000, length 2000
6. server > client: Flags [.], ack 2001, [nop,nop,sack 1 {501:2001}], length 0
After this fix, the final ACK is as below:
6. server > client: Flags [.], ack 2001, options [nop,nop,sack 1 {501:1001}], length 0
[edumazet] added a new packetdrill test in the following patch.
Fixes: 1da177e4c3 ("Linux-2.6.12-rc2")
Signed-off-by: xin.guo <guoxin0309@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250626123420.1933835-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcp_time_to_recover() does not need the @flag argument.
Its first parameter can be marked const, and of tcp_sock type.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250618091246.1260322-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
After the following commit from 2024:
commit e37ab73736 ("tcp: fix to allow timestamp undo if no retransmits were sent")
...there was buggy behavior where TCP connections without SACK support
could easily see erroneous undo events at the end of fast recovery or
RTO recovery episodes. The erroneous undo events could cause those
connections to suffer repeated loss recovery episodes and high
retransmit rates.
The problem was an interaction between the non-SACK behavior on these
connections and the undo logic. The problem is that, for non-SACK
connections at the end of a loss recovery episode, if snd_una ==
high_seq, then tcp_is_non_sack_preventing_reopen() holds steady in
CA_Recovery or CA_Loss, but clears tp->retrans_stamp to 0. Then upon
the next ACK the "tcp: fix to allow timestamp undo if no retransmits
were sent" logic saw the tp->retrans_stamp at 0 and erroneously
concluded that no data was retransmitted, and erroneously performed an
undo of the cwnd reduction, restoring cwnd immediately to the value it
had before loss recovery. This caused an immediate burst of traffic
and build-up of queues and likely another immediate loss recovery
episode.
This commit fixes tcp_packet_delayed() to ignore zero retrans_stamp
values for non-SACK connections when snd_una is at or above high_seq,
because tcp_is_non_sack_preventing_reopen() clears retrans_stamp in
this case, so it's not a valid signal that we can undo.
Note that the commit named in the Fixes footer restored long-present
behavior from roughly 2005-2019, so apparently this bug was present
for a while during that era, and this was simply not caught.
Fixes: e37ab73736 ("tcp: fix to allow timestamp undo if no retransmits were sent")
Reported-by: Eric Wheeler <netdev@lists.ewheeler.net>
Closes: https://lore.kernel.org/netdev/64ea9333-e7f9-0df-b0f2-8d566143acab@ewheeler.net/
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Co-developed-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Now that we have removed the RFC3517/RFC6675 hints,
tcp_clear_retrans_hints_partial() is empty, and can be removed.
Suggested-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250615001435.2390793-4-ncardwell.sw@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now that obsolete RFC3517/RFC6675 TCP loss detection has been removed,
we can remove the somewhat complex and intrusive code to maintain its
hint state: lost_skb_hint and lost_cnt_hint.
This commit makes tcp_clear_retrans_hints_partial() empty. We will
remove tcp_clear_retrans_hints_partial() and its call sites in the
next commit.
Suggested-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250615001435.2390793-3-ncardwell.sw@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
RACK-TLP loss detection has been enabled as the default loss detection
algorithm for Linux TCP since 2018, in:
commit b38a51fec1 ("tcp: disable RFC6675 loss detection")
In case users ran into unexpected bugs or performance regressions,
that commit allowed Linux system administrators to revert to using
RFC3517/RFC6675 loss recovery by setting net.ipv4.tcp_recovery to 0.
In the seven years since 2018, our team has not heard reports of
anyone reverting Linux TCP to use RFC3517/RFC6675 loss recovery, and
we can't find any record in web searches of such a revert.
RACK-TLP was published as a standards-track RFC, RFC8985, in February
2021.
Several other major TCP implementations have default-enabled RACK-TLP
at this point as well.
RACK-TLP offers several significant performance advantages over
RFC3517/RFC6675 loss recovery, including much better performance in
the common cases of tail drops, lost retransmissions, and reordering.
It is now time to remove the obsolete and unused RFC3517/RFC6675 loss
recovery code. This will allow a substantial simplification of the
Linux TCP code base, and removes 12 bytes of state in every tcp_sock
for 64-bit machines (8 bytes on 32-bit machines).
To arrange the commits in reasonable sizes, this patch series is split
into 3 commits. The following 2 commits remove bookkeeping state and
code that is no longer needed after this removal of RFC3517/RFC6675
loss recovery.
Suggested-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250615001435.2390793-2-ncardwell.sw@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcp_rcv_rtt_update() role is to keep an estimation
of RTT (tp->rcv_rtt_est.rtt_us) for receivers.
If an application is too slow to drain the TCP receive
queue, it is better to leave the RTT estimation small,
so that tcp_rcv_space_adjust() does not inflate
tp->rcvq_space.space and sk->sk_rcvbuf.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-9-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcp_rcv_rtt_update() goal is to maintain an estimation of the RTT
in tp->rcv_rtt_est.rtt_us, used by tcp_rcv_space_adjust()
When TCP TS are enabled, tcp_rcv_rtt_update() is using
EWMA to smooth the samples.
Change this to immediately latch the incoming value if it
is lower than tp->rcv_rtt_est.rtt_us, so that tcp_rcv_space_adjust()
does not overshoot tp->rcvq_space.space and sk->sk_rcvbuf.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-8-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
tcp_rcv_state_process() must tweak tp->advmss for TS enabled flows
before the call to tcp_init_transfer() / tcp_init_buffer_space().
Otherwise tp->rcvq_space.space is off by 120 bytes
(TCP_INIT_CWND * TCPOLEN_TSTAMP_ALIGNED).
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Wei Wang <weiwan@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-7-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
If the application can not drain fast enough a TCP socket queue,
tcp_rcv_space_adjust() can overestimate tp->rcvq_space.space.
Then sk->sk_rcvbuf can grow and hit tcp_rmem[2] for no good reason.
Fix this by taking into acount the number of available bytes.
Keeping sk->sk_rcvbuf at the right size allows better cache efficiency.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Wei Wang <weiwan@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-5-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This patch takes care of the needed provisioning
when incoming packets are stored in the out of order queue.
This part was not implemented in the correct way, we need
to decouple it from tcp_rcv_space_adjust() logic.
Without it, stalls in the pipe could happen.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Current autosizing in tcp_rcv_space_adjust() is too aggressive.
Instead of betting on possible losses and over estimate BDP,
it is better to only account for slow start.
The following patch is then adding a more precise tuning
in the events of packet losses.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250513193919.1089692-3-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This reverts commit 0de2a5c4b8.
I forgot that a TCP socket could receive messages in its error queue.
sock_queue_err_skb() can be called without socket lock being held,
and changes sk->sk_rmem_alloc.
The fact that skbs in error queue are limited by sk->sk_rcvbuf
means that error messages can be dropped if socket receive
queues are full, which is an orthogonal issue.
In future kernels, we could use a separate sk->sk_error_mem_alloc
counter specifically for the error queue.
Fixes: 0de2a5c4b8 ("tcp: avoid atomic operations on sk->sk_rmem_alloc")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250331075946.31960-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
TCP uses generic skb_set_owner_r() and sock_rfree()
for received packets, with socket lock being owned.
Switch to private versions, avoiding two atomic operations
per packet.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250320121604.3342831-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250317085313.2023214-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250312083907.1931644-1-edumazet@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Create helpers for TCP ECN modes. No functional changes.
Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Rename tcp_ecn_check_ce to tcp_data_ecn_check as it is
called only for data segments, not for ACKs (with AccECN,
also ACKs may get ECN bits).
The extra "layer" in tcp_ecn_check_ce() function just
checks for ECN being enabled, that can be moved into
tcp_ecn_field_check rather than having the __ variant.
No functional changes.
Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Whenever timestamp advances, it declares progress which
can be used by the other parts of the stack to decide that
the ACK is the most recent one seen so far.
AccECN will use this flag when deciding whether to use the
ACK to update AccECN state or not.
Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
- Move tcp_count_delivered() earlier and split tcp_count_delivered_ce()
out of it
- Move tcp_in_ack_event() later
- While at it, remove the inline from tcp_in_ack_event() and let
the compiler to decide
Accurate ECN's heuristics does not know if there is going
to be ACE field based CE counter increase or not until after
rtx queue has been processed. Only then the number of ACKed
bytes/pkts is available. As CE or not affects presence of
FLAG_ECE, that information for tcp_in_ack_event is not yet
available in the old location of the call to tcp_in_ack_event().
Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
We want to add new drop reasons for packets dropped in 3WHS in the
following patches.
tcp_rcv_state_process() has to set reason to TCP_FASTOPEN,
because tcp_check_req() will conditionally overwrite the drop_reason.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250301201424.2046477-2-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Yong-Hao Zou mentioned that linux was not strict as other OS in 3WHS,
for flows using TCP TS option (RFC 7323)
As hinted by an old comment in tcp_check_req(),
we can check the TSEcr value in the incoming packet corresponds
to one of the SYNACK TSval values we have sent.
In this patch, I record the oldest and most recent values
that SYNACK packets have used.
Send a challenge ACK if we receive a TSEcr outside
of this range, and increase a new SNMP counter.
nstat -az | grep TSEcrRejected
TcpExtTSEcrRejected 0 0.0
Due to TCP fastopen implementation, do not apply yet these checks
for fastopen flows.
v2: No longer use req->num_timeout, but treq->snt_tsval_first
to detect when first SYNACK is prepared. This means
we make sure to not send an initial zero TSval.
Make sure MPTCP and TCP selftests are passing.
Change MIB name to TcpExtTSEcrRejected
v1: https://lore.kernel.org/netdev/CADVnQykD8i4ArpSZaPKaoNxLJ2if2ts9m4As+=Jvdkrgx1qMHw@mail.gmail.com/T/
Reported-by: Yong-Hao Zou <yonghaoz1994@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250225171048.3105061-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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Merge tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next
Martin KaFai Lau says:
====================
pull-request: bpf-next 2025-02-20
We've added 19 non-merge commits during the last 8 day(s) which contain
a total of 35 files changed, 1126 insertions(+), 53 deletions(-).
The main changes are:
1) Add TCP_RTO_MAX_MS support to bpf_set/getsockopt, from Jason Xing
2) Add network TX timestamping support to BPF sock_ops, from Jason Xing
3) Add TX metadata Launch Time support, from Song Yoong Siang
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
igc: Add launch time support to XDP ZC
igc: Refactor empty frame insertion for launch time support
net: stmmac: Add launch time support to XDP ZC
selftests/bpf: Add launch time request to xdp_hw_metadata
xsk: Add launch time hardware offload support to XDP Tx metadata
selftests/bpf: Add simple bpf tests in the tx path for timestamping feature
bpf: Support selective sampling for bpf timestamping
bpf: Add BPF_SOCK_OPS_TSTAMP_SENDMSG_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_ACK_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SND_HW_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SND_SW_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SCHED_CB callback
net-timestamp: Prepare for isolating two modes of SO_TIMESTAMPING
bpf: Disable unsafe helpers in TX timestamping callbacks
bpf: Prevent unsafe access to the sock fields in the BPF timestamping callback
bpf: Prepare the sock_ops ctx and call bpf prog for TX timestamping
bpf: Add networking timestamping support to bpf_get/setsockopt()
selftests/bpf: Add rto max for bpf_setsockopt test
bpf: Support TCP_RTO_MAX_MS for bpf_setsockopt
====================
Link: https://patch.msgid.link/20250221022104.386462-1-martin.lau@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
The subsequent patch will implement BPF TX timestamping. It will
call the sockops BPF program without holding the sock lock.
This breaks the current assumption that all sock ops programs will
hold the sock lock. The sock's fields of the uapi's bpf_sock_ops
requires this assumption.
To address this, a new "u8 is_locked_tcp_sock;" field is added. This
patch sets it in the current sock_ops callbacks. The "is_fullsock"
test is then replaced by the "is_locked_tcp_sock" test during
sock_ops_convert_ctx_access().
The new TX timestamping callbacks added in the subsequent patch will
not have this set. This will prevent unsafe access from the new
timestamping callbacks.
Potentially, we could allow read-only access. However, this would
require identifying which callback is read-safe-only and also requires
additional BPF instruction rewrites in the covert_ctx. Since the BPF
program can always read everything from a socket (e.g., by using
bpf_core_cast), this patch keeps it simple and disables all read
and write access to any socket fields through the bpf_sock_ops
UAPI from the new TX timestamping callback.
Moreover, note that some of the fields in bpf_sock_ops are specific
to tcp_sock, and sock_ops currently only supports tcp_sock. In
the future, UDP timestamping will be added, which will also break
this assumption. The same idea used in this patch will be reused.
Considering that the current sock_ops only supports tcp_sock, the
variable is named is_locked_"tcp"_sock.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250220072940.99994-4-kerneljasonxing@gmail.com
Xiumei reported hitting the WARN in xfrm6_tunnel_net_exit while
running tests that boil down to:
- create a pair of netns
- run a basic TCP test over ipcomp6
- delete the pair of netns
The xfrm_state found on spi_byaddr was not deleted at the time we
delete the netns, because we still have a reference on it. This
lingering reference comes from a secpath (which holds a ref on the
xfrm_state), which is still attached to an skb. This skb is not
leaked, it ends up on sk_receive_queue and then gets defer-free'd by
skb_attempt_defer_free.
The problem happens when we defer freeing an skb (push it on one CPU's
defer_list), and don't flush that list before the netns is deleted. In
that case, we still have a reference on the xfrm_state that we don't
expect at this point.
We already drop the skb's dst in the TCP receive path when it's no
longer needed, so let's also drop the secpath. At this point,
tcp_filter has already called into the LSM hooks that may require the
secpath, so it should not be needed anymore. However, in some of those
places, the MPTCP extension has just been attached to the skb, so we
cannot simply drop all extensions.
Fixes: 68822bdf76 ("net: generalize skb freeing deferral to per-cpu lists")
Reported-by: Xiumei Mu <xmu@redhat.com>
Signed-off-by: Sabrina Dubroca <sd@queasysnail.net>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/5055ba8f8f72bdcb602faa299faca73c280b7735.1739743613.git.sd@queasysnail.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Since commit under Fixes we set the window clamp in accordance
to newly measured rcvbuf scaling_ratio. If the scaling_ratio
decreased significantly we may put ourselves in a situation
where windows become smaller than rcvq_space, preventing
tcp_rcv_space_adjust() from increasing rcvbuf.
The significant decrease of scaling_ratio is far more likely
since commit 697a6c8cec ("tcp: increase the default TCP scaling ratio"),
which increased the "default" scaling ratio from ~30% to 50%.
Hitting the bad condition depends a lot on TCP tuning, and
drivers at play. One of Meta's workloads hits it reliably
under following conditions:
- default rcvbuf of 125k
- sender MTU 1500, receiver MTU 5000
- driver settles on scaling_ratio of 78 for the config above.
Initial rcvq_space gets calculated as TCP_INIT_CWND * tp->advmss
(10 * 5k = 50k). Once we find out the true scaling ratio and
MSS we clamp the windows to 38k. Triggering the condition also
depends on the message sequence of this workload. I can't repro
the problem with simple iperf or TCP_RR-style tests.
Fixes: a2cbb16039 ("tcp: Update window clamping condition")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Link: https://patch.msgid.link/20250217232905.3162187-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Add a lightweight tracepoint to monitor TCP congestion window
adjustments via tcp_cwnd_reduction(). This tracepoint enables tracking
of:
- TCP window size fluctuations
- Active socket behavior
- Congestion window reduction events
Meta has been using BPF programs to monitor this function for years.
Adding a proper tracepoint provides a stable API for all users who need
to monitor TCP congestion window behavior.
Use DECLARE_TRACE instead of TRACE_EVENT to avoid creating trace event
infrastructure and exporting to tracefs, keeping the implementation
minimal. (Thanks Steven Rostedt)
Given that this patch creates a rawtracepoint, you could hook into it
using regular tooling, like bpftrace, using regular rawtracepoint
infrastructure, such as:
rawtracepoint:tcp_cwnd_reduction_tp {
....
}
Signed-off-by: Breno Leitao <leitao@debian.org>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250214-cwnd_tracepoint-v2-1-ef8d15162d95@debian.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Use EXPORT_IPV6_MOD[_GPL]() for symbols that don't need
to be exported unless CONFIG_IPV6=m
tcp_hashinfo and tcp_openreq_init_rwin() are no longer
used from any module anyway.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: Mateusz Polchlopek <mateusz.polchlopek@intel.com>
Link: https://patch.msgid.link/20250212132418.1524422-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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 <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
We want to factorize calls to inet_csk_reset_xmit_timer(),
to ease TCP_RTO_MAX change.
Current users want to add tcp_pacing_delay(sk)
to the timeout.
Remaining calls to inet_csk_reset_xmit_timer()
do not add the pacing delay. Following patch
will convert them, passing false for @pace_delay.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
All callers use TCP_RTO_MAX, we can factorize this constant,
becoming a variable soon.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
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 <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250206094605.2694118-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
These two functions are not called from modules.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Reviewed-by: Joe Damato <jdamato@fastly.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250206093436.2609008-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Prior patch in the series added TCP_RFC7323_PAWS_ACK drop reason.
This patch adds the corresponding SNMP counter, for folks
using nstat instead of tracing for TCP diagnostics.
nstat -az | grep PAWSOldAck
Suggested-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Tested-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://patch.msgid.link/20250113135558.3180360-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
