Merge tag 'pull-nbd-2025-03-05' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2025-03-05

- Several iotest fixes
- Refactor QMP for NbdServerOptions for less repetition
- Avoid a han

Merge tag 'pull-nbd-2025-03-05' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2025-03-05

- Several iotest fixes
- Refactor QMP for NbdServerOptions for less repetition
- Avoid a hang in 'qemu-nbd --fork' when simple trace backend is enabled

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAmfI2I0ACgkQp6FrSiUn
# Q2pMWQf/ZNnuLC5O5W4Yiyki7mYjN3Izve5+xgM/gNv9uTrHmYXogYzswpYz1USo
# aU1i/EFLJ5K7ImefQYBvySox+opwFs63xPscI/liwrKu54csp1rYGNg3hjKYaZCc
# ukR5tB4bRQ2/JXNo0JueiocMZLyC5fZRUt9Z423D3ReHCtEJof0v1rTL2r7mzGJg
# EdaRSGr0s592rFjWLwwvWWun5f0mEAFXM2YvZRRLE7M+x2XJeAR4F400GfvSMDNo
# chGX41QKhmCYTMI5Shc/mX+5hMllEt/TyYBJUUk0cslJriVnNDV5VTFf184BmH5s
# tqiUtzJubxt8/Wtpg6OV9RPAzVmr1g==
# =NO+l
# -----END PGP SIGNATURE-----
# gpg: Signature made Thu 06 Mar 2025 07:04:45 HKT
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2 F3AA A7A1 6B4A 2527 436A

* tag 'pull-nbd-2025-03-05' of https://repo.or.cz/qemu/ericb:
nbd: Defer trace init until after daemonization
qapi: merge common parts of NbdServerOptions and nbd-server-start data
iotests: Stop NBD server in test 162 before starting the next one
iotest: Unbreak 302 with python 3.13

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

qapi: merge common parts of NbdServerOptions and nbd-server-start data

Instead of comment
"Keep this type consistent with the nbd-server-start arguments", we
can simply merge these things.

Note tha

qapi: merge common parts of NbdServerOptions and nbd-server-start data

Instead of comment
"Keep this type consistent with the nbd-server-start arguments", we
can simply merge these things.

Note that each field of new base already has "since" tag, equal in both
original copies. So "since" information is saved.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20250219191914.440451-1-vsementsov@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...

Merge tag 'pull-nbd-2025-02-11' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2025-02-11

- Add --handshake-limit option to qemu-nbd

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAd

Merge tag 'pull-nbd-2025-02-11' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2025-02-11

- Add --handshake-limit option to qemu-nbd

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAmersd8ACgkQp6FrSiUn
# Q2pDUAf/c7inV7W+9vQv15lZoadIJkXAhqu+j1YuITC52gMgmU1QcwXMXRPEak4V
# qEIodiInzOtktMRXr6tbMroQgqo9eNd+VivxVa+J5LBILuZwdpZnLxsVNjblhbfI
# R3swWs2qluh9/1czntRu0J+YVOj3YZnF86Z5+iwEdLQ+i15dtjXDirBRvGCd6miV
# HLiEXwHdyPYb4g50a5oZCf3HhqPOgXOd+NWr4ifGut3bDulQk+FMDeBwV6/fmRPw
# g7dFPHMrAEYMw8tScYTMCoZGSZl0lg1JNuSh/WwgXx7BgXtDDxyP4HaAXlIyOHIA
# FbPU6aNrGZ9EDN4NA688IwUDh+lkmQ==
# =WyjJ
# -----END PGP SIGNATURE-----
# gpg: Signature made Tue 11 Feb 2025 15:23:59 EST
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2 F3AA A7A1 6B4A 2527 436A

* tag 'pull-nbd-2025-02-11' of https://repo.or.cz/qemu/ericb:
nbd/server: Allow users to adjust handshake limit in QMP
qemu-nbd: Allow users to adjust handshake limit

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

nbd/server: Allow users to adjust handshake limit in QMP

Although defaulting the handshake limit to 10 seconds was a nice QoI
change to weed out intentionally slow clients, it can interfere with
int

nbd/server: Allow users to adjust handshake limit in QMP

Although defaulting the handshake limit to 10 seconds was a nice QoI
change to weed out intentionally slow clients, it can interfere with
integration testing done with manual NBD_OPT commands over 'nbdsh
--opt-mode'. Expose a QMP knob 'handshake-max-secs' to allow the user
to alter the timeout away from the default.

The parameter name here intentionally matches the spelling of the
constant added in commit fb1c2aaa98, and not the command-line spelling
added in the previous patch for qemu-nbd; that's because in QMP,
longer names serve as good self-documentation, and unlike the command
line, machines don't have problems generating longer spellings.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20250203222722.650694-6-eblake@redhat.com>
[eblake: s/max-secs/max-seconds/ in QMP]
Acked-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

show more ...

Merge tag 'exec-20241220' of https://github.com/philmd/qemu into staging

Accel & Exec patch queue

- Ignore writes to CNTP_CTL_EL0 on HVF ARM (Alexander)
- Add '-d invalid_mem' logging option (Zolta

Merge tag 'exec-20241220' of https://github.com/philmd/qemu into staging

Accel & Exec patch queue

- Ignore writes to CNTP_CTL_EL0 on HVF ARM (Alexander)
- Add '-d invalid_mem' logging option (Zoltan)
- Create QOM containers explicitly (Peter)
- Rename sysemu/ -> system/ (Philippe)
- Re-orderning of include/exec/ headers (Philippe)
Move a lot of declarations from these legacy mixed bag headers:
. "exec/cpu-all.h"
. "exec/cpu-common.h"
. "exec/cpu-defs.h"
. "exec/exec-all.h"
. "exec/translate-all"
to these more specific ones:
. "exec/page-protection.h"
. "exec/translation-block.h"
. "user/cpu_loop.h"
. "user/guest-host.h"
. "user/page-protection.h"

# -----BEGIN PGP SIGNATURE-----
#
# iQIzBAABCAAdFiEE+qvnXhKRciHc/Wuy4+MsLN6twN4FAmdlnyAACgkQ4+MsLN6t
# wN6mBw//QFWi7CrU+bb8KMM53kOU9C507tjn99LLGFb5or73/umDsw6eo/b8DHBt
# KIwGLgATel42oojKfNKavtAzLK5rOrywpboPDpa3SNeF1onW+99NGJ52LQUqIX6K
# A6bS0fPdGG9ZzEuPpbjDXlp++0yhDcdSgZsS42fEsT7Dyj5gzJYlqpqhiXGqpsn8
# 4Y0UMxSL21K3HEexlzw2hsoOBFA3tUm2ujNDhNkt8QASr85yQVLCypABJnuoe///
# 5Ojl5wTBeDwhANET0rhwHK8eIYaNboiM9fHopJYhvyw1bz6yAu9jQwzF/MrL3s/r
# xa4OBHBy5mq2hQV9Shcl3UfCQdk/vDaYaWpgzJGX8stgMGYfnfej1SIl8haJIfcl
# VMX8/jEFdYbjhO4AeGRYcBzWjEJymkDJZoiSWp2NuEDi6jqIW+7yW1q0Rnlg9lay
# ShAqLK5Pv4zUw3t0Jy3qv9KSW8sbs6PQxtzXjk8p97rTf76BJ2pF8sv1tVzmsidP
# 9L92Hv5O34IqzBu2oATOUZYJk89YGmTIUSLkpT7asJZpBLwNM2qLp5jO00WVU0Sd
# +kAn324guYPkko/TVnjC/AY7CMu55EOtD9NU35k3mUAnxXT9oDUeL4NlYtfgrJx6
# x1Nzr2FkS68+wlPAFKNSSU5lTjsjNaFM0bIJ4LCNtenJVP+SnRo=
# =cjz8
# -----END PGP SIGNATURE-----
# gpg: Signature made Fri 20 Dec 2024 11:45:20 EST
# gpg: using RSA key FAABE75E12917221DCFD6BB2E3E32C2CDEADC0DE
# gpg: Good signature from "Philippe Mathieu-Daudé (F4BUG) <f4bug@amsat.org>" [unknown]
# gpg: WARNING: This key is not certified with a trusted signature!
# gpg: There is no indication that the signature belongs to the owner.
# Primary key fingerprint: FAAB E75E 1291 7221 DCFD 6BB2 E3E3 2C2C DEAD C0DE

* tag 'exec-20241220' of https://github.com/philmd/qemu: (59 commits)
util/qemu-timer: fix indentation
meson: Do not define CONFIG_DEVICES on user emulation
system/accel-ops: Remove unnecessary 'exec/cpu-common.h' header
system/numa: Remove unnecessary 'exec/cpu-common.h' header
hw/xen: Remove unnecessary 'exec/cpu-common.h' header
target/mips: Drop left-over comment about Jazz machine
target/mips: Remove tswap() calls in semihosting uhi_fstat_cb()
target/xtensa: Remove tswap() calls in semihosting simcall() helper
accel/tcg: Un-inline translator_is_same_page()
accel/tcg: Include missing 'exec/translation-block.h' header
accel/tcg: Move tcg_cflags_has/set() to 'exec/translation-block.h'
accel/tcg: Restrict curr_cflags() declaration to 'internal-common.h'
qemu/coroutine: Include missing 'qemu/atomic.h' header
exec/translation-block: Include missing 'qemu/atomic.h' header
accel/tcg: Declare cpu_loop_exit_requested() in 'exec/cpu-common.h'
exec/cpu-all: Include 'cpu.h' earlier so MMU_USER_IDX is always defined
target/sparc: Move sparc_restore_state_to_opc() to cpu.c
target/sparc: Uninline cpu_get_tb_cpu_state()
target/loongarch: Declare loongarch_cpu_dump_state() locally
user: Move various declarations out of 'exec/exec-all.h'
...

Conflicts:
hw/char/riscv_htif.c
hw/intc/riscv_aplic.c
target/s390x/cpu.c

Apply sysemu header path changes to not in the pull request.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

include: Rename sysemu/ -> system/

Headers in include/sysemu/ are not only related to system
*emulation*, they are also used by virtualization. Rename
as system/ which is clearer.

Files renamed man

include: Rename sysemu/ -> system/

Headers in include/sysemu/ are not only related to system
*emulation*, they are also used by virtualization. Rename
as system/ which is clearer.

Files renamed manually then mechanical change using sed tool.

Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Tested-by: Lei Yang <leiyang@redhat.com>
Message-Id: <20241203172445.28576-1-philmd@linaro.org>

show more ...

Merge tag 'pull-nbd-2024-08-26' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2024-08-26

- One more patch for CVE-2024-7409 (use-after-free on nbd-server-stop)

# -----BEGIN PGP SIG

Merge tag 'pull-nbd-2024-08-26' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2024-08-26

- One more patch for CVE-2024-7409 (use-after-free on nbd-server-stop)

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAmbMh9MACgkQp6FrSiUn
# Q2ovfAf/TyHYtJUwSAQ3dgn4PlTym4FqN8CXa+EJQR9xSLJ5jAX3QgLBieUiIT31
# AFr9W6eqWNz4NksbeoHdwZVqUlkGJFsfiyTOK93k4/fYQdTbqSHPwo2FYlOXqdJB
# bZN10zEvd7YRMrxTjGyPxNFCm2iIMZy8uEerOrY9hV1PVULHg6u3Pu8a6El4BK8k
# k5S0SwluTkUkBLbqtEC6fHjdfFFr/dC8IB11Ly8FdxKHixIaUTVsZ20guNM0Q5Ca
# kU2em2PcroDq3B0x3linD3xh3pVmlHdb4H+9runmGPnpJj5wjPL35aDzlU7GCT3B
# kEGX5VzOJOJUXoHVyYrvJCD4I7YgMw==
# =ZDYx
# -----END PGP SIGNATURE-----
# gpg: Signature made Mon 26 Aug 2024 11:49:07 PM AEST
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]

* tag 'pull-nbd-2024-08-26' of https://repo.or.cz/qemu/ericb:
nbd/server: CVE-2024-7409: Avoid use-after-free when closing server

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

show more ...

nbd/server: CVE-2024-7409: Avoid use-after-free when closing server

Commit 3e7ef738 plugged the use-after-free of the global nbd_server
object, but overlooked a use-after-free of nbd_server->listene

nbd/server: CVE-2024-7409: Avoid use-after-free when closing server

Commit 3e7ef738 plugged the use-after-free of the global nbd_server
object, but overlooked a use-after-free of nbd_server->listener.
Although this race is harder to hit, notice that our shutdown path
first drops the reference count of nbd_server->listener, then triggers
actions that can result in a pending client reaching the
nbd_blockdev_client_closed() callback, which in turn calls
qio_net_listener_set_client_func on a potentially stale object.

If we know we don't want any more clients to connect, and have already
told the listener socket to shut down, then we should not be trying to
update the listener socket's associated function.

Reproducer:

> #!/usr/bin/python3
>
> import os
> from threading import Thread
>
> def start_stop():
> while 1:
> os.system('virsh qemu-monitor-command VM \'{"execute": "nbd-server-start",
+"arguments":{"addr":{"type":"unix","data":{"path":"/tmp/nbd-sock"}}}}\'')
> os.system('virsh qemu-monitor-command VM \'{"execute": "nbd-server-stop"}\'')
>
> def nbd_list():
> while 1:
> os.system('/path/to/build/qemu-nbd -L -k /tmp/nbd-sock')
>
> def test():
> sst = Thread(target=start_stop)
> sst.start()
> nlt = Thread(target=nbd_list)
> nlt.start()
>
> sst.join()
> nlt.join()
>
> test()

Fixes: CVE-2024-7409
Fixes: 3e7ef738c8 ("nbd/server: CVE-2024-7409: Close stray clients at server-stop")
CC: qemu-stable@nongnu.org
Reported-by: Andrey Drobyshev <andrey.drobyshev@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240822143617.800419-2-eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>

show more ...

Merge tag 'pull-nbd-2024-08-08' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2024-08-08

- plug CVE-2024-7409, a DoS attack exploiting nbd-server-stop

# -----BEGIN PGP SIGNATURE---

Merge tag 'pull-nbd-2024-08-08' of https://repo.or.cz/qemu/ericb into staging

NBD patches for 2024-08-08

- plug CVE-2024-7409, a DoS attack exploiting nbd-server-stop

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAma1PVEACgkQp6FrSiUn
# Q2qdHQf/dMydqNcPYnwEI238APyljpNvHNq6p9TYb0l5aVWisXHRlhFWM117hH7T
# Aq2KUgS5ppiEpw8mxa6/OaDa74VpMGyEPgn9w6o7T1xjVBVzpMxOKp5wFa8uICLj
# mFMYXtj9i0Rb+z0iZ+X+CqIV2Wy/FyV00Wr9T4HW94IV/9EK1sWvZvfyGWyxYyBZ
# XKTQV1Co3HYX8gfq7E88SgS064DnHjtRy2no4lwNFkBbVQCSbqwbK63TRPi7kEyC
# DmSLdHCdsD7Ev9kMZ6uNJS5T/9t7hjO5mWJckLt/cXOjHgL7GkoisLH8/nGjVkyc
# 3SUGjMn4TlzqMU99STRP+a48TLCVhA==
# =kDut
# -----END PGP SIGNATURE-----
# gpg: Signature made Fri 09 Aug 2024 07:49:05 AM AEST
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]

* tag 'pull-nbd-2024-08-08' of https://repo.or.cz/qemu/ericb:
nbd/server: CVE-2024-7409: Close stray clients at server-stop
nbd/server: CVE-2024-7409: Drop non-negotiating clients
nbd/server: CVE-2024-7409: Cap default max-connections to 100
nbd/server: Plumb in new args to nbd_client_add()
nbd: Minor style and typo fixes

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

show more ...

nbd/server: CVE-2024-7409: Close stray clients at server-stop

A malicious client can attempt to connect to an NBD server, and then
intentionally delay progress in the handshake, including if it does

nbd/server: CVE-2024-7409: Close stray clients at server-stop

A malicious client can attempt to connect to an NBD server, and then
intentionally delay progress in the handshake, including if it does
not know the TLS secrets. Although the previous two patches reduce
this behavior by capping the default max-connections parameter and
killing slow clients, they did not eliminate the possibility of a
client waiting to close the socket until after the QMP nbd-server-stop
command is executed, at which point qemu would SEGV when trying to
dereference the NULL nbd_server global which is no longer present.
This amounts to a denial of service attack. Worse, if another NBD
server is started before the malicious client disconnects, I cannot
rule out additional adverse effects when the old client interferes
with the connection count of the new server (although the most likely
is a crash due to an assertion failure when checking
nbd_server->connections > 0).

For environments without this patch, the CVE can be mitigated by
ensuring (such as via a firewall) that only trusted clients can
connect to an NBD server. Note that using frameworks like libvirt
that ensure that TLS is used and that nbd-server-stop is not executed
while any trusted clients are still connected will only help if there
is also no possibility for an untrusted client to open a connection
but then stall on the NBD handshake.

Given the previous patches, it would be possible to guarantee that no
clients remain connected by having nbd-server-stop sleep for longer
than the default handshake deadline before finally freeing the global
nbd_server object, but that could make QMP non-responsive for a long
time. So intead, this patch fixes the problem by tracking all client
sockets opened while the server is running, and forcefully closing any
such sockets remaining without a completed handshake at the time of
nbd-server-stop, then waiting until the coroutines servicing those
sockets notice the state change. nbd-server-stop now has a second
AIO_WAIT_WHILE_UNLOCKED (the first is indirectly through the
blk_exp_close_all_type() that disconnects all clients that completed
handshakes), but forced socket shutdown is enough to progress the
coroutines and quickly tear down all clients before the server is
freed, thus finally fixing the CVE.

This patch relies heavily on the fact that nbd/server.c guarantees
that it only calls nbd_blockdev_client_closed() from the main loop
(see the assertion in nbd_client_put() and the hoops used in
nbd_client_put_nonzero() to achieve that); if we did not have that
guarantee, we would also need a mutex protecting our accesses of the
list of connections to survive re-entrancy from independent iothreads.

Although I did not actually try to test old builds, it looks like this
problem has existed since at least commit 862172f45c (v2.12.0, 2017) -
even back when that patch started using a QIONetListener to handle
listening on multiple sockets, nbd_server_free() was already unaware
that the nbd_blockdev_client_closed callback can be reached later by a
client thread that has not completed handshakes (and therefore the
client's socket never got added to the list closed in
nbd_export_close_all), despite that patch intentionally tearing down
the QIONetListener to prevent new clients.

Reported-by: Alexander Ivanov <alexander.ivanov@virtuozzo.com>
Fixes: CVE-2024-7409
CC: qemu-stable@nongnu.org
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240807174943.771624-14-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

show more ...

nbd/server: CVE-2024-7409: Cap default max-connections to 100

Allowing an unlimited number of clients to any web service is a recipe
for a rudimentary denial of service attack: the client merely nee

nbd/server: CVE-2024-7409: Cap default max-connections to 100

Allowing an unlimited number of clients to any web service is a recipe
for a rudimentary denial of service attack: the client merely needs to
open lots of sockets without closing them, until qemu no longer has
any more fds available to allocate.

For qemu-nbd, we default to allowing only 1 connection unless more are
explicitly asked for (-e or --shared); this was historically picked as
a nice default (without an explicit -t, a non-persistent qemu-nbd goes
away after a client disconnects, without needing any additional
follow-up commands), and we are not going to change that interface now
(besides, someday we want to point people towards qemu-storage-daemon
instead of qemu-nbd).

But for qemu proper, and the newer qemu-storage-daemon, the QMP
nbd-server-start command has historically had a default of unlimited
number of connections, in part because unlike qemu-nbd it is
inherently persistent until nbd-server-stop. Allowing multiple client
sockets is particularly useful for clients that can take advantage of
MULTI_CONN (creating parallel sockets to increase throughput),
although known clients that do so (such as libnbd's nbdcopy) typically
use only 8 or 16 connections (the benefits of scaling diminish once
more sockets are competing for kernel attention). Picking a number
large enough for typical use cases, but not unlimited, makes it
slightly harder for a malicious client to perform a denial of service
merely by opening lots of connections withot progressing through the
handshake.

This change does not eliminate CVE-2024-7409 on its own, but reduces
the chance for fd exhaustion or unlimited memory usage as an attack
surface. On the other hand, by itself, it makes it more obvious that
with a finite limit, we have the problem of an unauthenticated client
holding 100 fds opened as a way to block out a legitimate client from
being able to connect; thus, later patches will further add timeouts
to reject clients that are not making progress.

This is an INTENTIONAL change in behavior, and will break any client
of nbd-server-start that was not passing an explicit max-connections
parameter, yet expects more than 100 simultaneous connections. We are
not aware of any such client (as stated above, most clients aware of
MULTI_CONN get by just fine on 8 or 16 connections, and probably cope
with later connections failing by relying on the earlier connections;
libvirt has not yet been passing max-connections, but generally
creates NBD servers with the intent for a single client for the sake
of live storage migration; meanwhile, the KubeSAN project anticipates
a large cluster sharing multiple clients [up to 8 per node, and up to
100 nodes in a cluster], but it currently uses qemu-nbd with an
explicit --shared=0 rather than qemu-storage-daemon with
nbd-server-start).

We considered using a deprecation period (declare that omitting
max-parameters is deprecated, and make it mandatory in 3 releases -
then we don't need to pick an arbitrary default); that has zero risk
of breaking any apps that accidentally depended on more than 100
connections, and where such breakage might not be noticed under unit
testing but only under the larger loads of production usage. But it
does not close the denial-of-service hole until far into the future,
and requires all apps to change to add the parameter even if 100 was
good enough. It also has a drawback that any app (like libvirt) that
is accidentally relying on an unlimited default should seriously
consider their own CVE now, at which point they are going to change to
pass explicit max-connections sooner than waiting for 3 qemu releases.
Finally, if our changed default breaks an app, that app can always
pass in an explicit max-parameters with a larger value.

It is also intentional that the HMP interface to nbd-server-start is
not changed to expose max-connections (any client needing to fine-tune
things should be using QMP).

Suggested-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240807174943.771624-12-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[ericb: Expand commit message to summarize Dan's argument for why we
break corner-case back-compat behavior without a deprecation period]
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...

nbd/server: Plumb in new args to nbd_client_add()

Upcoming patches to fix a CVE need to track an opaque pointer passed
in by the owner of a client object, as well as request for a time
limit on how

nbd/server: Plumb in new args to nbd_client_add()

Upcoming patches to fix a CVE need to track an opaque pointer passed
in by the owner of a client object, as well as request for a time
limit on how fast negotiation must complete. Prepare for that by
changing the signature of nbd_client_new() and adding an accessor to
get at the opaque pointer, although for now the two servers
(qemu-nbd.c and blockdev-nbd.c) do not change behavior even though
they pass in a new default timeout value.

Suggested-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20240807174943.771624-11-eblake@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
[eblake: s/LIMIT/MAX_SECS/ as suggested by Dan]
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...

Merge tag 'pull-qapi-2022-12-14-v2' of https://repo.or.cz/qemu/armbru into staging

QAPI patches patches for 2022-12-14

# gpg: Signature made Wed 14 Dec 2022 19:14:34 GMT
# gpg: using

Merge tag 'pull-qapi-2022-12-14-v2' of https://repo.or.cz/qemu/armbru into staging

QAPI patches patches for 2022-12-14

# gpg: Signature made Wed 14 Dec 2022 19:14:34 GMT
# gpg: using RSA key 354BC8B3D7EB2A6B68674E5F3870B400EB918653
# gpg: issuer "armbru@redhat.com"
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>" [full]
# gpg: aka "Markus Armbruster <armbru@pond.sub.org>" [full]
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867 4E5F 3870 B400 EB91 8653

* tag 'pull-qapi-2022-12-14-v2' of https://repo.or.cz/qemu/armbru: (30 commits)
qapi: Drop temporary logic to support conversion step by step
qapi qga: Elide redundant has_FOO in generated C
qapi virtio: Elide redundant has_FOO in generated C
qapi ui: Elide redundant has_FOO in generated C
qapi transaction: Elide redundant has_FOO in generated C
qapi tpm: Elide redundant has_FOO in generated C
qapi stats: Elide redundant has_FOO in generated C
qapi run-state: Elide redundant has_FOO in generated C
qapi rocker: Elide redundant has_FOO in generated C
qapi replay: Elide redundant has_FOO in generated C
qapi qdev qom: Elide redundant has_FOO in generated C
qapi pci: Elide redundant has_FOO in generated C
qapi net: Elide redundant has_FOO in generated C
qapi misc: Elide redundant has_FOO in generated C
qapi migration: Elide redundant has_FOO in generated C
qapi machine: Elide redundant has_FOO in generated C
qapi job: Elide redundant has_FOO in generated C
qapi dump: Elide redundant has_FOO in generated C
qapi crypto: Elide redundant has_FOO in generated C
qapi chardev: Elide redundant has_FOO in generated C
...

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

qapi block: Elide redundant has_FOO in generated C

The has_FOO for pointer-valued FOO are redundant, except for arrays.
They are also a nuisance to work with. Recent commit "qapi: Start to
elide re

qapi block: Elide redundant has_FOO in generated C

The has_FOO for pointer-valued FOO are redundant, except for arrays.
They are also a nuisance to work with. Recent commit "qapi: Start to
elide redundant has_FOO in generated C" provided the means to elide
them step by step. This is the step for qapi/block*.json.

Said commit explains the transformation in more detail.

There is one instance of the invariant violation mentioned there:
qcow2_signal_corruption() passes false, "" when node_name is an empty
string. Take care to pass NULL then.

The previous two commits cleaned up two more.

Additionally, helper bdrv_latency_histogram_stats() loses its output
parameters and returns a value instead.

Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Hanna Reitz <hreitz@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20221104160712.3005652-11-armbru@redhat.com>
[Fixes for #ifndef LIBRBD_SUPPORTS_ENCRYPTION and MacOS squashed in]

show more ...

Merge tag 'for-upstream' of git://repo.or.cz/qemu/kevin into staging

Block layer patches

- coroutine: Fix crashes due to too large pool batch size
- fdc: Prevent end-of-track overrun
- nbd: MULTI_C

Merge tag 'for-upstream' of git://repo.or.cz/qemu/kevin into staging

Block layer patches

- coroutine: Fix crashes due to too large pool batch size
- fdc: Prevent end-of-track overrun
- nbd: MULTI_CONN for shared writable exports
- iotests test runner improvements

# -----BEGIN PGP SIGNATURE-----
#
# iQJFBAABCAAvFiEE3D3rFZqa+V09dFb+fwmycsiPL9YFAmJ9KCkRHGt3b2xmQHJl
# ZGhhdC5jb20ACgkQfwmycsiPL9ZtSRAAmYDFBPqxfutpFXM7kIKwL6COXJC12MOx
# Tmu8cDiGB/jNChdi3kl6I5h5njzo3U0ZlL/Ign6EzHoeoXLAPSeUWmuRsARwsZ+A
# rL61gf6yrMjAo45FZuIS0GlMDk8BauRwPl9qPWeqQcrtOMYpxwZfyFGmcMpQgAOI
# MSC1I8p3FA7oJhGpKIHDPOjaZA97Lm2rLnDIwZ4f0YgssbybFBcFCXOQbhpsVhLy
# Tjp/L+qRUtna9xBsPHQvHZW0kITQbCQPdX+oVqqUmwzSvuHqfXKe1YppyPjBt/S0
# H7nxtx4HOgP0lP5Kea+wbIRAk9Da5uaOW8hlMWRLShEKv1iTUenQSKteBB6CD03t
# GD9ze1kGoR9b6szw795BXxZxcWii0cn359lIVHeKR/U8zDuz5w3zhyl0klK8xeJy
# nj+JErLwQ7BD8kNR+7WAfXTF3tk2dQao1AvsBjn087KjMiJ/Mg8HY4K2zrjBUrHL
# DLTyAIjzct3BWJDZ02fb5jb8pHmIP3JO6m9Zvjm7ibP65BqJOwIXUTFpbgnrOg45
# oFLDV4JgC4Hh4GEtdm+UhQE51A0VVW5pDaqWTdWkCcuk3QgxUdM3Wm3SW6pw1Gvb
# T0X0j5RgF/k3YrW576R/VIy6z4YPbzAtiG4O/zSlsujHoDcVNWnxApgSB/unaDh8
# LNkFPGEMeSs=
# =JmTm
# -----END PGP SIGNATURE-----
# gpg: Signature made Thu 12 May 2022 08:30:49 AM PDT
# gpg: using RSA key DC3DEB159A9AF95D3D7456FE7F09B272C88F2FD6
# gpg: issuer "kwolf@redhat.com"
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>" [full]

* tag 'for-upstream' of git://repo.or.cz/qemu/kevin:
qemu-iotests: inline common.config into common.rc
nbd/server: Allow MULTI_CONN for shared writable exports
qemu-nbd: Pass max connections to blockdev layer
tests/qtest/fdc-test: Add a regression test for CVE-2021-3507
hw/block/fdc: Prevent end-of-track overrun (CVE-2021-3507)
.gitlab-ci.d: export meson testlog.txt as an artifact
tests/qemu-iotests: print intent to run a test in TAP mode
iotests/testrunner: Flush after run_test()
coroutine: Revert to constant batch size
coroutine: Rename qemu_coroutine_inc/dec_pool_size()

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

show more ...

nbd/server: Allow MULTI_CONN for shared writable exports

According to the NBD spec, a server that advertises
NBD_FLAG_CAN_MULTI_CONN promises that multiple client connections will
not see any cache

nbd/server: Allow MULTI_CONN for shared writable exports

According to the NBD spec, a server that advertises
NBD_FLAG_CAN_MULTI_CONN promises that multiple client connections will
not see any cache inconsistencies: when properly separated by a single
flush, actions performed by one client will be visible to another
client, regardless of which client did the flush.

We always satisfy these conditions in qemu - even when we support
multiple clients, ALL clients go through a single point of reference
into the block layer, with no local caching. The effect of one client
is instantly visible to the next client. Even if our backend were a
network device, we argue that any multi-path caching effects that
would cause inconsistencies in back-to-back actions not seeing the
effect of previous actions would be a bug in that backend, and not the
fault of caching in qemu. As such, it is safe to unconditionally
advertise CAN_MULTI_CONN for any qemu NBD server situation that
supports parallel clients.

Note, however, that we don't want to advertise CAN_MULTI_CONN when we
know that a second client cannot connect (for historical reasons,
qemu-nbd defaults to a single connection while nbd-server-add and QMP
commands default to unlimited connections; but we already have
existing means to let either style of NBD server creation alter those
defaults). This is visible by no longer advertising MULTI_CONN for
'qemu-nbd -r' without -e, as in the iotest nbd-qemu-allocation.

The harder part of this patch is setting up an iotest to demonstrate
behavior of multiple NBD clients to a single server. It might be
possible with parallel qemu-io processes, but I found it easier to do
in python with the help of libnbd, and help from Nir and Vladimir in
writing the test.

Signed-off-by: Eric Blake <eblake@redhat.com>
Suggested-by: Nir Soffer <nsoffer@redhat.com>
Suggested-by: Vladimir Sementsov-Ogievskiy <v.sementsov-og@mail.ru>
Message-Id: <20220512004924.417153-3-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

qemu-nbd: Pass max connections to blockdev layer

The next patch wants to adjust whether the NBD server code advertises
MULTI_CONN based on whether it is known if the server limits to
exactly one cli

qemu-nbd: Pass max connections to blockdev layer

The next patch wants to adjust whether the NBD server code advertises
MULTI_CONN based on whether it is known if the server limits to
exactly one client. For a server started by QMP, this information is
obtained through nbd_server_start (which can support more than one
export); but for qemu-nbd (which supports exactly one export), it is
controlled only by the command-line option -e/--shared. Since we
already have a hook function used by qemu-nbd, it's easiest to just
alter its signature to fit our needs.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20220512004924.417153-2-eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

show more ...

Merge tag 'pull-nbd-2022-04-26' of https://repo.or.cz/qemu/ericb into staging

nbd patches for 2022-04-26

- Paolo Bonzini: thread-safety improvements to NBD client
- Vladimir Sementsov-Ogievsky: fin

Merge tag 'pull-nbd-2022-04-26' of https://repo.or.cz/qemu/ericb into staging

nbd patches for 2022-04-26

- Paolo Bonzini: thread-safety improvements to NBD client
- Vladimir Sementsov-Ogievsky: finer-grained selection of bitmaps during
nbd-export

# -----BEGIN PGP SIGNATURE-----
#
# iQEzBAABCAAdFiEEccLMIrHEYCkn0vOqp6FrSiUnQ2oFAmJoUhAACgkQp6FrSiUn
# Q2qnpgf/YCuONdwAndjEo7he5c1BfB/F2sujQJJ00CebUqnz5OFKQ85RwLC8DCGB
# rXnxqC/NF4yyYM+6uYWDpggDd0bJVKbfG7NE/AZsEZrK+n9xMkvGLRwGqMugUii+
# Px4Ba98++0giqGoAI8pU/wQZNh1I6uGabv/DPRTpwzBjbfAcATqV09OzaGiK3SRC
# Zm/55zmXm1zM4XSUtUzN1gILPG09P+51m6NVkANZbzps9e2PtfFy8EsWc5+YhuBM
# 5K7sN+5g8GpRhz6j8RkrhrbNpvg3bGvgRJRMcW7Bo8KVUdvT1Jng6xs8CIRv39AF
# jDJwGe+cq5p5PNuyqOrVSA/ynBZxBw==
# =I1yM
# -----END PGP SIGNATURE-----
# gpg: Signature made Tue 26 Apr 2022 01:12:00 PM PDT
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]

* tag 'pull-nbd-2022-04-26' of https://repo.or.cz/qemu/ericb:
nbd: document what is protected by the CoMutexes
nbd: take receive_mutex when reading requests[].receiving
nbd: move s->state under requests_lock
nbd: code motion and function renaming
nbd: use a QemuMutex to synchronize yanking, reconnection and coroutines
nbd: keep send_mutex/free_sema handling outside nbd_co_do_establish_connection
nbd: remove peppering of nbd_client_connected
nbd: mark more coroutine_fns
nbd: safeguard against waking up invalid coroutine
iotests/223: check new possibility of exporting bitmaps by node/name
qapi: nbd-export: allow select bitmaps by node/name pair
qapi: rename BlockDirtyBitmapMergeSource to BlockDirtyBitmapOrStr

Signed-off-by: Richard Henderson <richard.henderson@linaro.org>

show more ...

qapi: nbd-export: allow select bitmaps by node/name pair

Hi all! Current logic of relying on search through backing chain is not
safe neither convenient.

Sometimes it leads to necessity of extra bi

qapi: nbd-export: allow select bitmaps by node/name pair

Hi all! Current logic of relying on search through backing chain is not
safe neither convenient.

Sometimes it leads to necessity of extra bitmap copying. Also, we are
going to add "snapshot-access" driver, to access some snapshot state
through NBD. And this driver is not formally a filter, and of course
it's not a COW format driver. So, searching through backing chain will
not work. Instead of widening the workaround of bitmap searching, let's
extend the interface so that user can select bitmap precisely.

Note, that checking for bitmap active status is not copied to the new
API, I don't see a reason for it, user should understand the risks. And
anyway, bitmap from other node is unrelated to this export being
read-only or read-write.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@openvz.org>
Message-Id: <20220314213226.362217-3-v.sementsov-og@mail.ru>
[eblake: Adjust S-o-b to Vladimir's new email, with permission]
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2022-03-07' into staging

nbd patches for 2022-03-07

- Dan Berrange: Allow qemu-nbd to support TLS over Unix sockets
- Eric Blake: Minor cle

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2022-03-07' into staging

nbd patches for 2022-03-07

- Dan Berrange: Allow qemu-nbd to support TLS over Unix sockets
- Eric Blake: Minor cleanups related to 64-bit block operations

# gpg: Signature made Tue 08 Mar 2022 01:41:35 GMT
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2 F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2022-03-07:
qemu-io: Allow larger write zeroes under no fallback
qemu-io: Utilize 64-bit status during map
nbd/server: Minor cleanups
tests/qemu-iotests: validate NBD TLS with UNIX sockets and PSK
tests/qemu-iotests: validate NBD TLS with UNIX sockets
tests/qemu-iotests: validate NBD TLS with hostname mismatch
tests/qemu-iotests: convert NBD TLS test to use standard filters
tests/qemu-iotests: introduce filter for qemu-nbd export list
tests/qemu-iotests: expand _filter_nbd rules
tests/qemu-iotests: add QEMU_IOTESTS_REGEN=1 to update reference file
block/nbd: don't restrict TLS usage to IP sockets
qemu-nbd: add --tls-hostname option for TLS certificate validation
block/nbd: support override of hostname for TLS certificate validation
block: pass desired TLS hostname through from block driver client
crypto: mandate a hostname when checking x509 creds on a client

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block/nbd: don't restrict TLS usage to IP sockets

The TLS usage for NBD was restricted to IP sockets because validating
x509 certificates requires knowledge of the hostname that the client
is connec

block/nbd: don't restrict TLS usage to IP sockets

The TLS usage for NBD was restricted to IP sockets because validating
x509 certificates requires knowledge of the hostname that the client
is connecting to.

TLS does not have to use x509 certificates though, as PSK (pre-shared
keys) provide an alternative credential option. These have no
requirement for a hostname and can thus be trivially used for UNIX
sockets.

Furthermore, with the ability to overide the default hostname for
TLS validation in the previous patch, it is now also valid to want
to use x509 certificates with FD passing and UNIX sockets.

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
Message-Id: <20220304193610.3293146-6-berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/berrange-gitlab/tags/tls-deps-pull-request' into staging

Hide build time dependancy on gnutls fom non-crypto code

# gpg: Signature made Wed 30 Jun 2021 12:18:4

Merge remote-tracking branch 'remotes/berrange-gitlab/tags/tls-deps-pull-request' into staging

Hide build time dependancy on gnutls fom non-crypto code

# gpg: Signature made Wed 30 Jun 2021 12:18:47 BST
# gpg: using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg: aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E 8E3F BE86 EBB4 1510 4FDF

* remotes/berrange-gitlab/tags/tls-deps-pull-request:
crypto: Make QCryptoTLSCreds* structures private
ui/vnc: Use qcrypto_tls_creds_check_endpoint()
migration/tls: Use qcrypto_tls_creds_check_endpoint()
chardev/socket: Use qcrypto_tls_creds_check_endpoint()
qemu-nbd: Use qcrypto_tls_creds_check_endpoint()
block/nbd: Use qcrypto_tls_creds_check_endpoint()
crypto/tlscreds: Introduce qcrypto_tls_creds_check_endpoint() helper

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block/nbd: Use qcrypto_tls_creds_check_endpoint()

Avoid accessing QCryptoTLSCreds internals by using
the qcrypto_tls_creds_check_endpoint() helper.

Reviewed-by: Richard Henderson <richard.henderson

block/nbd: Use qcrypto_tls_creds_check_endpoint()

Avoid accessing QCryptoTLSCreds internals by using
the qcrypto_tls_creds_check_endpoint() helper.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

show more ...

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-02-12' into staging

nbd patches for 2021-02-12

- let qemu-nbd handle larger backlog of connecting clients
- fix a few NBD-related iote

Merge remote-tracking branch 'remotes/ericb/tags/pull-nbd-2021-02-12' into staging

nbd patches for 2021-02-12

- let qemu-nbd handle larger backlog of connecting clients
- fix a few NBD-related iotest failures
- add block cancellation hook for faster response to NBD failures

# gpg: Signature made Fri 12 Feb 2021 19:57:56 GMT
# gpg: using RSA key 71C2CC22B1C4602927D2F3AAA7A16B4A2527436A
# gpg: Good signature from "Eric Blake <eblake@redhat.com>" [full]
# gpg: aka "Eric Blake (Free Software Programmer) <ebb9@byu.net>" [full]
# gpg: aka "[jpeg image of size 6874]" [full]
# Primary key fingerprint: 71C2 CC22 B1C4 6029 27D2 F3AA A7A1 6B4A 2527 436A

* remotes/ericb/tags/pull-nbd-2021-02-12:
iotests/264: add backup-cancel test-case
block/backup: implement .cancel job handler
iotests/264: add mirror-cancel test-case
iotests.py: qemu_nbd_popen: remove pid file after use
iotests/264: move to python unittest
block/mirror: implement .cancel job handler
job: add .cancel handler for the driver
block/raw-format: implement .bdrv_cancel_in_flight handler
block/nbd: implement .bdrv_cancel_in_flight
block: add new BlockDriver handler: bdrv_cancel_in_flight
io: error_prepend() in qio_channel_readv_full_all() causes segfault
iotests/210: Fix reference output
qemu-nbd: Permit --shared=0 for unlimited clients
qemu-nbd: Use SOMAXCONN for socket listen() backlog

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

qemu-nbd: Use SOMAXCONN for socket listen() backlog

Our default of a backlog of 1 connection is rather puny; it gets in
the way when we are explicitly allowing multiple clients (such as
qemu-nbd -e

qemu-nbd: Use SOMAXCONN for socket listen() backlog

Our default of a backlog of 1 connection is rather puny; it gets in
the way when we are explicitly allowing multiple clients (such as
qemu-nbd -e N [--shared], or nbd-server-start with its default
"max-connections":0 for unlimited), but is even a problem when we
stick to qemu-nbd's default of only 1 active client but use -t
[--persistent] where a second client can start using the server once
the first finishes. While the effects are less noticeable on TCP
sockets (since the client can poll() to learn when the server is ready
again), it is definitely observable on Unix sockets, where on Linux, a
client will fail with EAGAIN and no recourse but to sleep an arbitrary
amount of time before retrying if the server backlog is already full.

Since QMP nbd-server-start is always persistent, it now always
requests a backlog of SOMAXCONN; meanwhile, qemu-nbd will request
SOMAXCONN if persistent, otherwise its backlog should be based on the
expected number of clients.

See https://bugzilla.redhat.com/1925045 for a demonstration of where
our low backlog prevents libnbd from connecting as many parallel
clients as it wants.

Reported-by: Richard W.M. Jones <rjones@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
CC: qemu-stable@nongnu.org
Message-Id: <20210209152759.209074-2-eblake@redhat.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

show more ...