Go to file
Ryan Sharpelletti afcd3ea8af tcp: only postpone PROBE_RTT if RTT is < current min_rtt estimate
[ Upstream commit 1b9e2a8c99a5c021041bfb2d512dc3ed92a94ffd ]

During loss recovery, retransmitted packets are forced to use TCP
timestamps to calculate the RTT samples, which have a millisecond
granularity. BBR is designed using a microsecond granularity. As a
result, multiple RTT samples could be truncated to the same RTT value
during loss recovery. This is problematic, as BBR will not enter
PROBE_RTT if the RTT sample is <= the current min_rtt sample, meaning
that if there are persistent losses, PROBE_RTT will constantly be
pushed off and potentially never re-entered. This patch makes sure
that BBR enters PROBE_RTT by checking if RTT sample is < the current
min_rtt sample, rather than <=.

The Netflix transport/TCP team discovered this bug in the Linux TCP
BBR code during lab tests.

Fixes: 0f8782ea1497 ("tcp_bbr: add BBR congestion control")
Signed-off-by: Ryan Sharpelletti <sharpelletti@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Soheil Hassas Yeganeh <soheil@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Link: https://lore.kernel.org/r/20201116174412.1433277-1-sharpelletti.kdev@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-03-16 16:41:08 +08:00
Documentation powerpc/64s: flush L1D after user accesses 2021-03-16 16:41:00 +08:00
LICENSES Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
arch KVM: x86: clflushopt should be treated as a no-op by emulation 2021-03-16 16:41:03 +08:00
block blk-cgroup: Pre-allocate tree node on blkg_conf_prep 2021-03-16 16:40:25 +08:00
certs 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 crypto: algif_skcipher - EBUSY on aio should be an error 2021-03-16 16:38:24 +08:00
drivers qlcnic: fix error return code in qlcnic_83xx_restart_hw() 2021-03-16 16:41:08 +08:00
fs Convert trailing spaces and periods in path components 2021-03-16 16:41:00 +08:00
include Exempt multicast addresses from five-second neighbor lifetime 2021-03-16 16:41:04 +08:00
init printk: reduce LOG_BUF_SHIFT range for H8300 2021-03-16 16:39:45 +08:00
ipc ipc/util.c: sysvipc_find_ipc() incorrectly updates position index 2021-03-16 16:27:51 +08:00
kernel perf/core: Fix race in the perf_mmap_close() function 2021-03-16 16:40:59 +08:00
lib random32: make prandom_u32() output unpredictable 2021-03-16 16:40:40 +08:00
mm page_frag: Recover from memory pressure 2021-03-16 16:41:08 +08:00
net tcp: only postpone PROBE_RTT if RTT is < current min_rtt estimate 2021-03-16 16:41:08 +08:00
package config/arm64: OPEN CONFIG_PSI and phytium configs 2021-03-16 11:02:59 +08:00
samples samples/bpf: Fix possible deadlock in xdpsock 2021-03-16 16:39:46 +08:00
scripts scripts/setlocalversion: make git describe output more reliable 2021-03-16 16:39:28 +08:00
security selinux: Fix error return code in sel_ib_pkey_sid_slow() 2021-03-16 16:40:55 +08:00
sound ALSA: hda: Reinstate runtime_allow() for all hda controllers 2021-03-16 16:40:42 +08:00
tools selftests/powerpc: entry flush test 2021-03-16 16:41:01 +08:00
usr Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
virt KVM: arm64: ARM_SMCCC_ARCH_WORKAROUND_1 doesn't return SMCCC_RET_NOT_REQUIRED 2021-03-16 16:40:40 +08:00
.clang-format Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
.cocciconfig Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
.get_maintainer.ignore Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
.gitattributes Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
.gitignore Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
COPYING Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
CREDITS Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kbuild Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
Kconfig Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
MAINTAINERS Documentation/llvm: add documentation on building w/ Clang/LLVM 2021-03-16 16:34:24 +08:00
Makefile kbuild: fix broken builds because of GZIP,BZIP2,LZOP variables 2021-03-16 16:35:20 +08:00
README Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
README.md Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
backport_remove_lists.txt Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00
tools_key.pub Init Repo base on linux 5.4.32 long term, and add base tlinux kernel interfaces. 2021-03-16 11:01:34 +08:00

README.md

Tencent Linux Kernel 4.0