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Kuniyuki Iwashima 4b01a96742 tcp: bind(0) remove the SO_REUSEADDR restriction when ephemeral ports are exhausted. 
Commit aacd9289af ("tcp: bind() use stronger
condition for bind_conflict") introduced a restriction to forbid to bind
SO_REUSEADDR enabled sockets to the same (addr, port) tuple in order to
assign ports dispersedly so that we can connect to the same remote host.

The change results in accelerating port depletion so that we fail to bind
sockets to the same local port even if we want to connect to the different
remote hosts.

You can reproduce this issue by following instructions below.

  1. # sysctl -w net.ipv4.ip_local_port_range="32768 32768"
  2. set SO_REUSEADDR to two sockets.
  3. bind two sockets to (localhost, 0) and the latter fails.

Therefore, when ephemeral ports are exhausted, bind(0) should fallback to
the legacy behaviour to enable the SO_REUSEADDR option and make it possible
to connect to different remote (addr, port) tuples.

This patch allows us to bind SO_REUSEADDR enabled sockets to the same
(addr, port) only when net.ipv4.ip_autobind_reuse is set 1 and all
ephemeral ports are exhausted. This also allows connect() and listen() to
share ports in the following way and may break some applications. So the
ip_autobind_reuse is 0 by default and disables the feature.

  1. setsockopt(sk1, SO_REUSEADDR)
  2. setsockopt(sk2, SO_REUSEADDR)
  3. bind(sk1, saddr, 0)
  4. bind(sk2, saddr, 0)
  5. connect(sk1, daddr)
  6. listen(sk2)

If it is set 1, we can fully utilize the 4-tuples, but we should use
IP_BIND_ADDRESS_NO_PORT for bind()+connect() as possible.

The notable thing is that if all sockets bound to the same port have
both SO_REUSEADDR and SO_REUSEPORT enabled, we can bind sockets to an
ephemeral port and also do listen().

Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Signed-off-by: David S. Miller <davem@davemloft.net>
2020-03-12 12:08:09 -07:00
..
ABI xen: branch for v5.6-rc1 2020-02-05 17:44:14 +00:00
accounting docs: add some documentation dirs to the driver-api book 2019-07-15 11:03:02 -03:00
admin-guide Tracing updates: 2020-02-26 10:34:42 -08:00
arm ARM: at91: Documentation: add sam9x60 product and datasheet 2020-01-10 23:40:31 +01:00
arm64 mm: Avoid creating virtual address aliases in brk()/mmap()/mremap() 2020-02-20 10:03:14 +00:00
block docs: block/biovecs: update the location of bio.c 2020-01-10 10:23:15 -07:00
bpf docs/bpf: Update bpf development Q/A file 2020-02-20 18:05:37 -08:00
cdrom docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
core-api mm, tree-wide: rename put_user_page*() to unpin_user_page*() 2020-01-31 10:30:38 -08:00
cpu-freq Documentation: cpufreq: Update policy notifier documentation 2019-09-02 22:44:05 +02:00
crypto crypto: algapi - make unregistration functions return void 2019-12-20 14:58:35 +08:00
dev-tools Documentation: kunit: fixed sphinx error in code block 2020-02-10 17:16:42 -07:00
devicetree dt-bindings: soc: qcom: fix IPA binding 2020-03-12 00:05:45 -07:00
doc-guide Documentation: build warnings related to missing blank lines after explicit markups has been fixed 2020-02-05 10:30:03 -07:00
driver-api Minor bug fixes for IPMI 2020-02-16 13:05:46 -08:00
EDID docs: driver-api: add a series of orphaned documents 2019-07-15 11:03:02 -03:00
fault-injection docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
fb fbdev: fbmem: allow overriding the number of bootup logos 2020-01-03 14:27:40 +01:00
features s390 updates for the 5.6 merge window #2 2020-02-05 17:33:35 +00:00
filesystems zonefs: fix documentation typos etc. 2020-02-21 18:09:26 +09:00
firmware_class
firmware-guide docs: firmware-guide: ACPI: Replace dma_request_slave_channel() with dma_request_chan() 2019-12-19 22:58:12 +01:00
fpga Documentation: fpga: dfl: add descriptions for thermal/power management interfaces 2019-10-16 19:18:26 -07:00
gpu drm-misc-next for v5.6: 2020-01-03 11:43:44 +10:00
hid docs: add some documentation dirs to the driver-api book 2019-07-15 11:03:02 -03:00
hwmon Documentation/hwmon: fix xdpe12284 Sphinx warnings 2020-02-17 14:20:55 -08:00
i2c docs: i2c: writing-clients: properly name the stop condition 2020-01-29 22:02:09 +01:00
ia64 docs: add SPDX tags to new index files 2019-07-15 11:03:03 -03:00
ide docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
iio docs: add some documentation dirs to the driver-api book 2019-07-15 11:03:02 -03:00
infiniband Documentation/infiniband: update name of some functions 2019-09-13 16:55:55 -03:00
input Input: docs: fix spelling mistake "potocol" -> "protocol" 2019-08-06 11:24:49 -06:00
isdn isdn: capi: dead code removal 2019-12-11 09:12:38 +01:00
kbuild kbuild: get rid of trailing slash from subdir- example 2020-02-27 10:03:27 +09:00
kernel-hacking Documentation: kernel-hacking: hacking.rst: Change reference to document namespaces.rst to symbol-namespaces.rst 2019-12-19 09:36:23 -07:00
leds leds: core: Add support for composing LED class device names 2019-07-25 20:07:52 +02:00
livepatch livepatch: Documentation of the new API for tracking system state changes 2019-11-01 13:08:24 +01:00
locking docs/locking: Fix outdated section names 2020-02-05 10:21:12 -07:00
m68k docs: README.buddha: convert to ReST and add to m68k book 2019-07-31 13:30:10 -06:00
maintainer Add a maintainer entry profile for documentation 2020-01-24 09:48:39 -07:00
media media updates for v5.6-rc1 2020-01-31 14:43:23 -08:00
mic docs: driver-api: add remaining converted dirs to it 2019-07-15 11:03:03 -03:00
mips docs: fix some broken references 2019-10-10 11:25:39 -06:00
misc-devices Documentation: fix Sphinx warning in xilinx_sdfec.rst 2019-12-19 09:26:25 -07:00
netlabel docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
networking tcp: bind(0) remove the SO_REUSEADDR restriction when ephemeral ports are exhausted. 2020-03-12 12:08:09 -07:00
nios2 docs: nios2: add it to the main Documentation body 2019-07-31 13:31:51 -06:00
nvdimm docs: nvdimm: use ReST notation for subsection 2020-01-24 09:54:42 -07:00
openrisc docs: openrisc: convert to ReST and add to documentation body 2019-07-31 13:30:20 -06:00
parisc docs: parisc: convert to ReST and add to documentation body 2019-07-31 13:30:15 -06:00
PCI Documentation: PCI: Fix pci_alloc_irq_vectors() function name typo 2019-12-30 08:21:29 -06:00
pcmcia docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
power Documentation: admin-guide: PM: Update sleep states documentation 2020-02-03 11:58:26 +01:00
powerpc powerpc updates for 5.6 2020-02-04 13:06:46 +00:00
process Documentation/process: Swap out the ambassador for Canonical 2020-02-13 15:38:41 -08:00
RCU Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD 2020-01-24 10:37:27 -08:00
riscv It has been a relatively quiet cycle for documentation, but there's still a 2020-01-29 15:27:31 -08:00
s390 Documentation/s390: remove outdated debugging390 documentation 2019-08-21 12:41:43 +02:00
scheduler Documentation/scheduler: fix links in sched-stats 2019-10-29 04:35:41 -06:00
scsi scsi: smartpqi: Update attribute name to driver_version 2019-12-09 19:17:36 -05:00
security Documentation: security: core.rst: fix warnings 2019-11-22 10:01:47 -07:00
sh docs: remove extra conf.py files 2019-07-17 06:57:52 -03:00
sound sound updates for 5.6-rc1 2020-01-28 16:26:57 -08:00
sparc docs: add arch doc directories to the index 2019-07-15 11:03:01 -03:00
sphinx docs: Fix empty parallelism argument 2020-02-25 03:11:04 -07:00
sphinx-static doc-rst: Reduce CSS padding around Field 2019-10-02 10:03:06 -06:00
spi spi: docs: convert to ReST and add it to the kABI bookset 2019-07-31 14:13:13 -06:00
target docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
timers docs: add some directories to the main documentation index 2019-07-15 11:03:03 -03:00
trace A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
translations Documentation/process: Swap out the ambassador for Canonical 2020-02-13 15:38:41 -08:00
usb docs: usb: remove some broken references 2020-01-28 13:41:22 -07:00
userspace-api staging: remove isdn capi drivers 2019-12-11 09:11:29 +01:00
virt KVM: s390: rstify new ioctls in api.rst 2020-02-24 19:28:40 +01:00
vm mm/zswap.c: add allocation hysteresis if pool limit is hit 2020-01-31 10:30:39 -08:00
w1 docs: w1: Fix a typo in omap-hdq.rst 2019-12-30 11:58:02 -07:00
watchdog linux-watchdog 5.4-rc1 tag 2019-09-27 11:17:38 -07:00
x86 docs: remove MPX from the x86 toc 2020-02-25 03:10:22 -07:00
xtensa docs: add arch doc directories to the index 2019-07-15 11:03:01 -03:00
.gitignore
asm-annotations.rst Documentation: Call out example SYM_FUNC_* usage as x86-specific 2020-01-16 12:53:16 -07:00
atomic_bitops.txt
atomic_t.txt Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2019-07-08 16:12:03 -07:00
bus-virt-phys-mapping.txt
Changes
CodingStyle
conf.py doc-rst: Programmatically render MAINTAINERS into ReST 2019-10-02 10:03:17 -06:00
COPYING-logo docs: logo.txt: rename it to COPYING-logo 2019-07-15 09:20:27 -03:00
crc32.txt
debugging-modules.txt
debugging-via-ohci1394.txt
digsig.txt
DMA-API-HOWTO.txt docs: DMA-API-HOWTO.txt: fix an unmarked code block 2019-07-15 09:20:24 -03:00
DMA-API.txt dma-mapping: remove dma_release_declared_memory 2019-09-04 11:13:19 +02:00
DMA-attributes.txt dma-mapping: remove the DMA_ATTR_WRITE_BARRIER flag 2019-11-14 12:01:54 -04:00
DMA-ISA-LPC.txt
docutils.conf doc-rst: Add missing newline at end of file 2019-06-20 14:16:56 -06:00
dontdiff modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
futex-requeue-pi.txt
hwspinlock.txt hwspinlock: add the 'in_atomic' API 2019-06-29 21:08:14 -07:00
index.rst Here's the main documentation changes for 5.5: 2019-12-02 11:51:02 -08:00
io_ordering.txt
io-mapping.txt
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
irqflags-tracing.txt
Kconfig
kobject.txt
kprobes.txt
kref.txt
logo.gif
lzo.txt
mailbox.txt
Makefile Kbuild updates for v5.5 2019-12-02 17:35:04 -08:00
memory-barriers.txt smp_mb__{before,after}_atomic(): update Documentation 2020-02-04 03:05:23 +00:00
nommu-mmap.txt
percpu-rw-semaphore.txt
pi-futex.txt docs: locking: convert docs to ReST and rename to *.rst 2019-07-15 08:53:27 -03:00
preempt-locking.txt
rbtree.txt docs: rbtree.txt: fix Sphinx build warnings 2019-07-15 09:20:24 -03:00
remoteproc.txt remoteproc: add vendor resources handling 2019-06-29 12:02:17 -07:00
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt
speculation.txt
static-keys.txt
SubmittingPatches
tee.txt Documentation: tee: add AMD-TEE driver details 2020-01-04 13:49:51 +08:00
this_cpu_ops.txt
unaligned-memory-access.txt
xz.txt