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David Howells 24457be58e rxrpc: Fix the excessive initial retransmission timeout 
commit c410bf01933e5e09d142c66c3df9ad470a7eec13 upstream.

rxrpc currently uses a fixed 4s retransmission timeout until the RTT is
sufficiently sampled.  This can cause problems with some fileservers with
calls to the cache manager in the afs filesystem being dropped from the
fileserver because a packet goes missing and the retransmission timeout is
greater than the call expiry timeout.

Fix this by:

 (1) Copying the RTT/RTO calculation code from Linux's TCP implementation
     and altering it to fit rxrpc.

 (2) Altering the various users of the RTT to make use of the new SRTT
     value.

 (3) Replacing the use of rxrpc_resend_timeout to use the calculated RTO
     value instead (which is needed in jiffies), along with a backoff.

Notes:

 (1) rxrpc provides RTT samples by matching the serial numbers on outgoing
     DATA packets that have the RXRPC_REQUEST_ACK set and PING ACK packets
     against the reference serial number in incoming REQUESTED ACK and
     PING-RESPONSE ACK packets.

 (2) Each packet that is transmitted on an rxrpc connection gets a new
     per-connection serial number, even for retransmissions, so an ACK can
     be cross-referenced to a specific trigger packet.  This allows RTT
     information to be drawn from retransmitted DATA packets also.

 (3) rxrpc maintains the RTT/RTO state on the rxrpc_peer record rather than
     on an rxrpc_call because many RPC calls won't live long enough to
     generate more than one sample.

 (4) The calculated SRTT value is in units of 8ths of a microsecond rather
     than nanoseconds.

The (S)RTT and RTO values are displayed in /proc/net/rxrpc/peers.

Fixes: 17926a79320a ([AF_RXRPC]: Provide secure RxRPC sockets for use by userspace and kernel both"")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2021-03-16 16:28:20 +08:00
..
acpi x86: ACPI: fix CPU hotplug deadlock 2021-03-16 16:26:37 +08:00
asm-generic x86/Hyper-V: Report crash data in die() when panic_on_oops is set 2021-03-16 16:26:30 +08:00
clocksource Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
crypto Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
drm drm/bridge: analogix_dp: Split bind() into probe() and real bind() 2021-03-16 16:27:24 +08:00
dt-bindings Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
keys KEYS: Don't write out to userspace while holding key semaphore 2021-03-16 16:26:42 +08:00
kvm Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
linux bpf: Avoid setting bpf insns pages read-only when prog is jited 2021-03-16 16:28:17 +08:00
math-emu Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
media media: rc: add keymap for Videostrong KII Pro 2021-03-16 16:25:54 +08:00
misc Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
net rxrpc: Fix the excessive initial retransmission timeout 2021-03-16 16:28:20 +08:00
pcmcia Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
ras Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
rdma Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
scsi Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
soc Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
sound ALSA: hda: Manage concurrent reg access more properly 2021-03-16 16:28:13 +08:00
target scsi: target: fix hang when multiple threads try to destroy the same iscsi session 2021-03-16 16:26:27 +08:00
trace rxrpc: Fix the excessive initial retransmission timeout 2021-03-16 16:28:20 +08:00
uapi dma-buf: Fix SET_NAME ioctl uapi 2021-03-16 16:27:16 +08:00
vdso Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
video Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
xen Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00