linux.git/include/linux/tcp.h, branch v6.16-rc2

tcp: add receive queue awareness in tcp_rcv_space_adjust()

2025-05-15T18:30:08+00:00

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 
Reviewed-by: Wei Wang 
Link: https://patch.msgid.link/20250513193919.1089692-5-edumazet@google.com
Signed-off-by: Jakub Kicinski

tcp: fastopen: note that a child socket was created

2025-04-25T01:21:04+00:00

tcp: fastopen: note that a child socket was created

This uses up the last bit in a field of tcp_sock.

Signed-off-by: Jeremy Harris 
Reviewed-by: Eric Dumazet 
Reviewed-by: Neal Cardwell 
Link: https://patch.msgid.link/20250423124334.4916-2-jgh@exim.org
Signed-off-by: Jakub Kicinski

tcp: move icsk_clean_acked to a better location

2025-03-24T16:55:18+00:00

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 
Reviewed-by: Neal Cardwell 
Reviewed-by: Sabrina Dubroca 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250317085313.2023214-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

tcp: be less liberal in TSEcr received while in SYN_RECV state

2025-02-27T02:11:17+00:00

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 
Signed-off-by: Eric Dumazet 
Reviewed-by: Matthieu Baerts (NGI0) 
Reviewed-by: Neal Cardwell 
Reviewed-by: Kuniyuki Iwashima 
Link: https://patch.msgid.link/20250225171048.3105061-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

net: tcp: replace the document for "lsndtime" in tcp_sock

2024-11-05T02:10:56+00:00

Commit d5fed5addb2b ("tcp: reorganize tcp_sock fast path variables")
moved the fields around and misplaced the documentation for "lsndtime".
So, let's replace it in the proper place.

Signed-off-by: Menglong Dong 
Reviewed-by: Eric Dumazet 
Link: https://patch.msgid.link/20241104070041.64302-1-dongml2@chinatelecom.cn
Signed-off-by: Jakub Kicinski

tcp: more struct tcp_sock adjustments

2024-04-08T10:49:02+00:00

tp->recvmsg_inq is used from tcp recvmsg() thus should
be in tcp_sock_read_rx group.

tp->tcp_clock_cache and tp->tcp_mstamp are written
both in rx and tx paths, thus are better placed
in tcp_sock_write_txrx group.

Signed-off-by: Eric Dumazet 
Signed-off-by: David S. Miller

tcp: align tcp_sock_write_rx group

2024-03-05T04:46:18+00:00

Stephen Rothwell and kernel test robot reported that some arches
(parisc, hexagon) and/or compilers would not like blamed commit.

Lets make sure tcp_sock_write_rx group does not start with a hole.

While we are at it, correct tcp_sock_write_tx CACHELINE_ASSERT_GROUP_SIZE()
since after the blamed commit, we went to 105 bytes.

Fixes: 99123622050f ("tcp: remove some holes in struct tcp_sock")
Reported-by: Stephen Rothwell 
Reported-by: kernel test robot 
Link: https://lore.kernel.org/netdev/20240301121108.5d39e4f9@canb.auug.org.au/
Closes: https://lore.kernel.org/oe-kbuild-all/202403011451.csPYOS3C-lkp@intel.com/
Signed-off-by: Eric Dumazet 
Reviewed-by: Simon Horman 
Tested-by: Simon Horman  # build-tested
Link: https://lore.kernel.org/r/20240301171945.2958176-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

tcp: remove some holes in struct tcp_sock

2024-02-29T04:21:24+00:00

By moving some fields around, this patch shrinks
holes size from 56 to 32, saving 24 bytes on 64bit arches.

After the patch pahole gives the following for 'struct tcp_sock':

	/* size: 2304, cachelines: 36, members: 162 */
	/* sum members: 2234, holes: 6, sum holes: 32 */
	/* sum bitfield members: 34 bits, bit holes: 5, sum bit holes: 14 bits */
	/* padding: 32 */
	/* paddings: 3, sum paddings: 10 */
	/* forced alignments: 1, forced holes: 1, sum forced holes: 12 */

Signed-off-by: Eric Dumazet 
Reviewed-by: Jiri Pirko 
Link: https://lore.kernel.org/r/20240227192721.3558982-1-edumazet@google.com
Signed-off-by: Jakub Kicinski

tcp: move tp->tcp_usec_ts to tcp_sock_read_txrx group

2024-02-12T09:51:26+00:00

tp->tcp_usec_ts is a read mostly field, used in rx and tx fast paths.

Fixes: d5fed5addb2b ("tcp: reorganize tcp_sock fast path variables")
Signed-off-by: Eric Dumazet 
Cc: Coco Li 
Cc: Wei Wang 
Reviewed-by: Simon Horman 
Signed-off-by: David S. Miller

tcp: move tp->scaling_ratio to tcp_sock_read_txrx group

2024-02-12T09:51:26+00:00

tp->scaling_ratio is a read mostly field, used in rx and tx fast paths.

Fixes: d5fed5addb2b ("tcp: reorganize tcp_sock fast path variables")
Signed-off-by: Eric Dumazet 
Cc: Coco Li 
Cc: Wei Wang 
Reviewed-by: Simon Horman 
Signed-off-by: David S. Miller