Unable to listen to unix domain socket inside bindfs mount

[slonopotamus]

binfs build instructions: mpartel/bindfs#100 (comment)

Minimal way to reproduce:

(as root)

$ mkdir a
$ mkdir b
$ bindfs a b
$ nc -U b/sock -l
nc: Input/output error
$ nc -U a/sock -l
<works>

My environment: macOS Ventura + fuse-t 1.0.23 + bindfs 1.17.3

Note that the same steps do work on Linux + netcat-openbsd.

bindfs devs believe the root of the issue is not in bindfs itself: mpartel/bindfs#132 (comment)

nc is just used as an example (it is installed on macOS out of the box), I observe the same behavior when trying to listen to unix domain socket from Go via net.Listen("unix", path.Join("b/sock")

[slonopotamus]

See additional details in mpartel/bindfs#132. It looks like fuse-t doesn't forward mknod call to bindfs at all.

[alexfs]

bindfs doesn't implement mknod with sock file type.
See https://libfuse.github.io/doxygen/example_2passthrough__helpers_8h_source.html

[slonopotamus]

Yeah, mknod implementation seems to be incomplete in bindfs, but if I read log in mpartel/bindfs#132 (comment) correctly, fuse-t doesn't even try to call mknod in bindfs?

[alexfs]

I will add this functionality in the next version

[slonopotamus]

I've tried 1.0.24, but it seems that fuse-t still doesn't pass mknod call to binds

Running bindfs -d -f shows that nc -U sock -l produces the following calls:

unique: 50, opcode: GETATTR (3), nodeid: 1, insize: 56, pid: 0
getattr /
   unique: 50, success, outsize: 136
unique: 51, opcode: STATFS (17), nodeid: 1, insize: 40, pid: 0
statfs_x /
   unique: 51, success, outsize: 96
unique: 52, opcode: STATFS (17), nodeid: 1, insize: 40, pid: 0
statfs_x /
   unique: 52, success, outsize: 96
unique: 53, opcode: LOOKUP (1), nodeid: 1, insize: 42, pid: 0
LOOKUP /b
getattr /b
   unique: 53, error: -2 (No such file or directory), outsize: 16
unique: 54, opcode: STATFS (17), nodeid: 1, insize: 40, pid: 0
statfs_x /
   unique: 54, success, outsize: 9

[alexfs]

bindfs -d -f a b
nc -U -l b/sock1

statfs_x /
unique: 55, success, outsize: 96
unique: 56, opcode: GETATTR (3), nodeid: 1, insize: 56, pid: 0
getattr /
unique: 56, success, outsize: 136
unique: 57, opcode: LOOKUP (1), nodeid: 1, insize: 46, pid: 0
LOOKUP /sock1
getattr /sock1
unique: 57, error: -2 (No such file or directory), outsize: 16
unique: 58, opcode: MKNOD (8), nodeid: 1, insize: 62, pid: 0
mknod /sock1 0140755 0x0 umask=0000

[slonopotamus]

Hmm... Not sure what I did wrong. After retrying, I confirm that mknod is now passed to binds. nc is still unable to create UNIX socket, but as was discussed, this needs to be fixed on binds side. Thanks for the fix.