Re: [PATCH v3 1/1] python/machine: Fix AF_UNIX path too long on macOS

[Peter Delevoryas]

On Mon, Jan 09, 2023 at 04:09:32PM -0500, John Snow wrote:
> On Mon, Jul 25, 2022 at 5:06 AM Daniel P. Berrangé <berrange@redhat.com> 
> wrote:
> >
> > On Fri, Jul 22, 2022 at 11:25:08AM -0700, Peter Delevoryas wrote:
> > > On macOS, private $TMPDIR's are the default. These $TMPDIR's are
> > > generated from a user's unix UID and UUID [1], which can create a
> > > relatively long path:
> > >
> > >     /var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T/
> > >
> > > QEMU's avocado tests create a temporary directory prefixed by
> > > "avo_qemu_sock_", and create QMP sockets within _that_ as well.
> > > The QMP socket is unnecessarily long, because a temporary directory
> > > is created for every QEMUMachine object.
> > >
> > >     /avo_qemu_sock_uh3w_dgc/qemu-37331-10bacf110-monitor.sock
> > >
> > > The path limit for unix sockets on macOS is 104: [2]
> > >
> > >     /*
> > >      * [XSI] Definitions for UNIX IPC domain.
> > >      */
> > >     struct  sockaddr_un {
> > >         unsigned char   sun_len;        /* sockaddr len including null */
> > >         sa_family_t     sun_family;     /* [XSI] AF_UNIX */
> > >         char            sun_path[104];  /* [XSI] path name (gag) */
> > >     };
> > >
> > > This results in avocado tests failing on macOS because the QMP unix
> > > socket can't be created, because the path is too long:
> > >
> > >     ERROR| Failed to establish connection: OSError: AF_UNIX path too long
> > >
> > > This change resolves by reducing the size of the socket directory prefix
> > > and the suffix on the QMP and console socket names.
> > >
> > > The result is paths like this:
> > >
> > >     pdel@pdel-mbp:/var/folders/d7/rz20f6hd709c1ty8f6_6y_z40000gn/T
> > >     $ tree qemu*
> > >     qemu_df4evjeq
> > >     qemu_jbxel3gy
> > >     qemu_ml9s_gg7
> > >     qemu_oc7h7f3u
> > >     qemu_oqb1yf97
> > >     ├── 10a004050.con
> > >     └── 10a004050.qmp
> > >
> > > [1] 
> > > https://apple.stackexchange.com/questions/353832/why-is-mac-osx-temp-directory-in-weird-path
> > > [2] 
> > > /Library/Developer/CommandLineTools/SDKs/MacOSX12.3.sdk/usr/include/sys/un.h
> > >
> > > Signed-off-by: Peter Delevoryas <peter@pjd.dev>
> > > ---
> > >  python/qemu/machine/machine.py         | 6 +++---
> > >  tests/avocado/avocado_qemu/__init__.py | 2 +-
> > >  2 files changed, 4 insertions(+), 4 deletions(-)
> >
> > Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> 
> My apologies, I missed this update because it appeared in a thread
> underneath the old version.

Oh, that's ok, nice catch digging this up! I completely forgot about it, and
haven't been developing QEMU stuff on macOS in a little while

> 
> Peter, may I please ask for you to kindly re-submit this patch with an
> incremented version number?

Sure! I've resubmitted it as v4 and v5, v4 might not have been sent correctly
(I have so many problems with sending emails lol)

v4: 20230110080756.38271-1-peter@pjd.dev/T/#t">https://lore.kernel.org/qemu-devel/20230110080756.38271-1-peter@pjd.dev/T/#t
v5: < will probably show up on the mailing list soon >


- Peter

> 
> --js
>