Update libssh to 0.11.1 #3735

Sploder12 · 2024-10-16T19:26:56Z

Sets the timeout to infinite since no messages for extended periods of time is expected behavior. Libssh updated to fix timeout being ignored.
Sets the pty mode explicitly to default since Libssh updated to inherit settings from stdin.

Fixes #3745

MULTI-1528

codecov · 2024-10-16T19:50:23Z

Codecov Report

Attention: Patch coverage is 26.66667% with 22 lines in your changes missing coverage. Please review.

Project coverage is 88.86%. Comparing base (f01004e) to head (431ff31).
Report is 14 commits behind head on main.

Files with missing lines	Patch %	Lines
src/platform/platform_unix.cpp	0.00%	19 Missing ⚠️
src/sshfs_mount/sshfs_mount.cpp	75.00%	2 Missing ⚠️
src/platform/console/unix_console.cpp	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3735      +/-   ##
==========================================
- Coverage   88.94%   88.86%   -0.09%     
==========================================
  Files         256      255       -1     
  Lines       14584    14602      +18     
==========================================
+ Hits        12972    12976       +4     
- Misses       1612     1626      +14

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ricab

Nice work Trevor, thanks. I ask only for some unit tests for the new code. Other than that, +1 on my secondary review.

Sploder12 · 2024-10-21T14:40:10Z

Some reproduction steps for the issues.

Formatting:

Run multipass launch -n <instance-name>
Run multipass shell <instance-name>
Observe incorrectly formatted shell and no ECHO

Mounts:

Run multipass launch -n <instance-name>
Run multipass mount <source> <target>
Wait ~30 seconds after mount finishes mounting
Run multipass shell <instance-name> (GUI doesn't have shell formatting issues)
Attempt to navigate to the files in <target>
Run ls or cd
Observe shell hang

georgeliao

Hi @Sploder12

Thanks for the good work, the fix seems to be solid. I only have a few minor comments and questions.

src/platform/console/unix_console.cpp

src/sshfs_mount/sshfs_mount.cpp

georgeliao · 2024-12-03T09:24:55Z

src/sshfs_mount/sshfs_mount.cpp

+                           const std::string& target,
+                           const mp::id_mappings& gid_mappings,
+                           const mp::id_mappings& uid_mappings)
+    : running{true},


Should setting running to be true be in the sftp_thread as a way of localizing the variable?

It should not be true until the sftp_server is running, so maybe before sftp_server->run(); is more appropriate. What do you think?

I had the same intuition, but I believe this needs to be alive right after construction, so that the watchdog doesn't quit before the thread starts.

To avoid confusion, one alternative would be to have an enum to distinguish the running state, instead of a bool. Something like "unstarted, running, stopped". Then in the watchdog condition, look for stopped. The logic would be the same, but it would help readers and future devs not move this and introduce a bug. WDYT?

Ricardo's belief is correct. The watchdog would immediately exit if the thread takes a while to start. I think the enum approach would work well though.

ok, i see, then the enum approach is fine.

src/sshfs_mount/sshfs_mount.h

georgeliao · 2024-12-03T09:44:24Z

src/ssh/ssh_session.cpp

    : session{ssh_new(), ssh_free}, mut{}
 {
    if (session == nullptr)
        throw mp::SSHException("could not allocate ssh session");

-    const long timeout_secs = std::chrono::duration_cast<std::chrono::seconds>(timeout).count();
+    const long timeout_secs = std::numeric_limits<long>::max();


About this change, I think the timeout_secs is used to set the SSH_OPTIONS_TIMEOUT, and this option is the timeout value for ssh session connection establishment wait time (not entire sure about this, hard to find a clear documentation as well). Therefore, having a reasonable value (like the original 20 seconds) seems to makes sense here.

Besides, with your watchdog fix ( which is essentially checking the sftp_threading running together with other SIGQUIT, SIGTERM, SIGHUP signals), the program already behaves correctly. So I am doubting whether we still make the time out change here. What do you think?

Wasn't this a keep-alive timeout? A better var name might help here.

The program will not behave correctly with a reasonable timeout unfortunately. After the timeout expires, the sshfs_server process will exit, the watchdog fix makes it so that it doesn't hang. It behaves like a keep-alive timeout, but libssh has no keep-alive messages.

ok, so it looks like a keep-alive timeout as opposed to ssh session connection establishment wait time, interesting. It is a weird option offered to users though.

I do have a wondering here though, the SSH_OPTIONS_TIMEOUT is the a ssh option. If it were a keep-alive timeout, should it be the timeout of ssh session alive? If so, should the multipass shell hang without mount?

multipass shell doesn't hang since it's setup to automatically reconnect. You can see this behavior in #3810 where the SSH session is restarting every 20 seconds. Also with normal use it's much more likely there is some SSH traffic within the 20 seconds compared to SFTP which is likely to not get any traffic for long periods of time.

src/platform/platform_unix.cpp

ricab

Great PR @Sploder12! And nice review as well @georgeliao 😃

A few comments on my secondary review.

src/platform/platform_unix.cpp

include/multipass/platform.h

ricab · 2024-12-03T11:55:45Z

src/sshfs_mount/sshfs_mount.cpp

+                           const std::string& target,
+                           const mp::id_mappings& gid_mappings,
+                           const mp::id_mappings& uid_mappings)
+    : running{true},


I had the same intuition, but I believe this needs to be alive right after construction, so that the watchdog doesn't quit before the thread starts.

To avoid confusion, one alternative would be to have an enum to distinguish the running state, instead of a bool. Something like "unstarted, running, stopped". Then in the watchdog condition, look for stopped. The logic would be the same, but it would help readers and future devs not move this and introduce a bug. WDYT?

ricab · 2024-12-03T12:00:32Z

src/ssh/ssh_session.cpp

    : session{ssh_new(), ssh_free}, mut{}
 {
    if (session == nullptr)
        throw mp::SSHException("could not allocate ssh session");

-    const long timeout_secs = std::chrono::duration_cast<std::chrono::seconds>(timeout).count();
+    const long timeout_secs = std::numeric_limits<long>::max();


Wasn't this a keep-alive timeout? A better var name might help here.

src/platform/platform_unix.cpp

georgeliao · 2024-12-11T16:59:34Z

src/platform/platform_unix.cpp

+        int sig = SIGUSR2;
+
+        // A signal generator that triggers after `timeout`
+        AutoJoinThread signaler([&sig_mtx, &sig_cv, &sig, &timeout, signalee = pthread_self()] {


Ok, we need to replace this in house utility when std::jthread is available.

georgeliao · 2024-12-11T17:36:17Z

src/platform/platform_unix.cpp

+        }
+
+        {
+            std::unique_lock lock(sig_mtx);


Maybe use std::lock_guard<std::mutex> as opposed to std::unique_lock since we do not need to move the lock into a function.

georgeliao · 2024-12-12T11:10:54Z

src/platform/platform_unix.cpp

+            std::unique_lock lock(sig_mtx);
+            while (sig == SIGUSR2)
+            {
+                auto status = sig_cv.wait_for(lock, timeout);


I think you can use the wait_for overloaded function with the predicate to check the sig != SIGUSR2, which can simplify the code here.

Good catch, so something like this should work

while (!sig_cv.wait_for(lock, timeout, [&sig]() { return sig != SIGUSR2; })) { pthread_kill(signalee, SIGUSR2); }

Sploder12 force-pushed the update-libssh branch from da5d0fc to 79996f8 Compare October 18, 2024 16:49

Sploder12 marked this pull request as ready for review October 18, 2024 18:54

ricab requested a review from georgeliao October 21, 2024 09:06

ricab reviewed Oct 21, 2024

View reviewed changes

sharder996 added this to the 1.15.0 milestone Oct 30, 2024

lars18th mentioned this pull request Nov 15, 2024

multipass.exe in Windows is not redirecting STDIN #3749

Open

Sploder12 force-pushed the update-libssh branch 2 times, most recently from de690f1 to 96d1a01 Compare November 27, 2024 20:17

ricab modified the milestones: 1.15.0, 1.15.1 Nov 29, 2024

georgeliao reviewed Dec 3, 2024

View reviewed changes

ricab reviewed Dec 3, 2024

View reviewed changes

Sploder12 marked this pull request as draft December 4, 2024 19:28

Sploder12 added 11 commits December 5, 2024 10:56

[libssh] Reapply previous version

1e74ce4

[ssh] Set timeout to infinite

6e5b64b

[ssh] Do not inherit settings from stdin

52b54b0

[ssh] Apply missed formatting

659f1ce

[ssh] Set stdin to Raw only after libssh inherits sane settings

70d3309

[ssh] Fix sshfs process ignoring child not running anymore

479199f

[ssh] Treat stfp thread exit as failure

cd7b935

[ssh] Formatted [[nodiscard]]

cbbe301

[sshfs] Use optional for watchdog

3631553

[sshfs] Use state enum instead of running bool

848a4e5

[sshfs] Change watchdog to not use sigtimedwait

3df817f

Sploder12 force-pushed the update-libssh branch from 16562f3 to 3df817f Compare December 5, 2024 15:56

[sshfs] Use seperate signaling thread

979ee07

Sploder12 marked this pull request as ready for review December 9, 2024 21:41

georgeliao reviewed Dec 11, 2024

View reviewed changes

src/platform/platform_unix.cpp Outdated Show resolved Hide resolved

georgeliao reviewed Dec 11, 2024

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[libssh] Remove stray include

431ff31

georgeliao reviewed Dec 11, 2024

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georgeliao reviewed Dec 12, 2024

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Update libssh to 0.11.1 #3735

Update libssh to 0.11.1 #3735

Sploder12 commented Oct 16, 2024 •

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Update libssh to 0.11.1 #3735

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Update libssh to 0.11.1 #3735

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Formatting:

Mounts:

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