sane-backends: fails to find any scanners

[dacioromero]

Describe the bug

Simple Scan, Skanlite, and scanimage -L fail to find any scanners immediately on nixos-unstable.

Steps To Reproduce

Steps to reproduce the behavior:

1. Have a WiFi enabled printer/scanner.
2. Enable avahi w/ nssmdns and sane

   {
     services.avahi.enable = true;
     services.avahi.nssmdns = true;
     hardware.sane.enable = true;
   }

3. Run scanimage -L and observe

Expected behavior

SANE should be able to find printers and webcams (v4l).

Screenshots

N/A

Additional context

Reverting to sane-backends 1.1.1 allows scanimage -L to search for scanners again. 1.2.1 might be bugged or require more configuration.

#216017

Notify maintainers

@symphorien

Metadata

 - system: `"x86_64-linux"`
 - host os: `Linux 6.1.21, NixOS, 23.05 (Stoat), 23.05.20230330.e3652e0`
 - multi-user?: `yes`
 - sandbox: `yes`
 - version: `nix-env (Nix) 2.13.3`
 - channels(root): `"nixos"`
 - channels(xxxxx): `"home-manager-22.05.tar.gz"`
 - nixpkgs: `/nix/var/nix/profiles/per-user/root/channels/nixos`

[symphorien]

I can reproduce: scanimage -L does not list anything. What is weird is that it works on top of #216017 but not on your commit anymore e3652e0
I tried to bisect it, but I end up in a staging iteration:

$  git bisect log
git bisect start
# status : en attente d'un commit bon et d'un commit mauvais
# bad: [e3652e0735fbec227f342712f180f4f21f0594f2] Merge pull request #218587 from sephii/python-wagtail
git bisect bad e3652e0735fbec227f342712f180f4f21f0594f2
# status : en attente de bon(s) commit(s), un mauvais commit connu
# good: [f0ddf281c593b82a2bd11110e8147ba85a1de70c] sane-backends: 1.1.1 -> 1.2.1
git bisect good f0ddf281c593b82a2bd11110e8147ba85a1de70c
# good: [90ef5c3c337d8d9f0c97e7641ece70a41f6c16a2] Merge pull request #219870 from mweinelt/evcc-0.114.1
git bisect good 90ef5c3c337d8d9f0c97e7641ece70a41f6c16a2
# good: [7dcef0a1e28f55f887e88e545b6f3544b5c375e7] Merge pull request #219777 from r-ryantm/auto-update/tdb
git bisect good 7dcef0a1e28f55f887e88e545b6f3544b5c375e7
# good: [2e4e45290e8a0e178642ae2414de558ecca0041a] Merge pull request #222930 from Ma27/bump-nextcloud
git bisect good 2e4e45290e8a0e178642ae2414de558ecca0041a
# bad: [ca7c52c4f514952d9cb70a20364f93f1a84e8b49] Merge pull request #222762 from Kiskae/nvidia/530.41.03
git bisect bad ca7c52c4f514952d9cb70a20364f93f1a84e8b49
# bad: [07fb9cae4e13da222e9d356d34e990c162f08a51] Merge master into staging-next
git bisect bad 07fb9cae4e13da222e9d356d34e990c162f08a51
# skip: [d970a8103542838477286f0aa5f6b2c2b4d8a630] Merge branch 'staging' into staging-next
git bisect skip d970a8103542838477286f0aa5f6b2c2b4d8a630
# good: [cceff04ce9c2c4cc3eab27a10dd220cc5c381b3d] mongodb-4_2: 4.2.19 -> 4.2.24
git bisect good cceff04ce9c2c4cc3eab27a10dd220cc5c381b3d
# skip: [1fab86929f7df5cdd60bcf65b4c78f4058777a03] nixos/pipewire: spring cleaning
git bisect skip 1fab86929f7df5cdd60bcf65b4c78f4058777a03
# skip: [764dd10ac0d7700d065571c438953a12aea84cf3] iproute2: 6.1.0 -> 6.2.0
git bisect skip 764dd10ac0d7700d065571c438953a12aea84cf3
# good: [89e0570cab7e8858edad5054f0cbb35a104a7d44] Merge pull request #223078 from wegank/scons-latest
git bisect good 89e0570cab7e8858edad5054f0cbb35a104a7d44
# skip: [05aaf0ddc5bdb6cc4e66fd18b0de70a4d06c6e4a] Merge pull request #219465 from erdnaxe/readline-strictdeps
git bisect skip 05aaf0ddc5bdb6cc4e66fd18b0de70a4d06c6e4a
# good: [7590ada96f561c77b9c5b9e564ab684b9eb34d97] liburcu: add changelog to meta
git bisect good 7590ada96f561c77b9c5b9e564ab684b9eb34d97
# good: [8b0faba367f833e9233172860233fe2b7e3eb503] python310Packages.scmrepo: 0.1.16 -> 0.1.17
git bisect good 8b0faba367f833e9233172860233fe2b7e3eb503
# skip: [7060259b5bc782e9630dc1e2122f0b7154259ab6] Merge pull request #219692 from r-ryantm/auto-update/iproute2
git bisect skip 7060259b5bc782e9630dc1e2122f0b7154259ab6
# skip: [00dff290ed9e4938d06403a69aa4083497178643] Merge staging-next into staging
git bisect skip 00dff290ed9e4938d06403a69aa4083497178643
# skip: [52ffebb7a7a6fb1ad2d64e8099451d0cbb281e68] ruby: add strictDeps
git bisect skip 52ffebb7a7a6fb1ad2d64e8099451d0cbb281e68
# skip: [1e5a594e686f5154b706dfab68550f9f3bde675e] spandsp: enableParallelBuilding = true
git bisect skip 1e5a594e686f5154b706dfab68550f9f3bde675e
# skip: [79cfdf110a45c668879686546e36672dced2426c] Merge pull request #219351 from tie/make-bios-bootable
git bisect skip 79cfdf110a45c668879686546e36672dced2426c

So the culprit is likely to be another dep, maybe curl because I suspect you use the escl backend?

[dacioromero]

I feel like there's more to it than that. 1.2.1 fails to find even my webcam and the failure is immediate with no signs of actually having doing anything to search.

[ulrikstrid]

I have this issue as well. scanimage -L doesn't find anything, but sane-find-scanner find it like this: found possible USB scanner (vendor=0x04a9 [Canon], product=0x174a [MG6100 series]) at libusb:002:002

[symphorien]

sane is actually not loading any plugins anymore: running LD_DEBUG=files scanimage -L does not show messages like

    813331:	file=/etc/sane-libs/libsane-canon.so.1 [0];  dynamically loaded by /nix/store/fvxr6brg9bhdi4k5x71f7kr9qsg8ipxg-sane-backends-1.0.32/lib/libsane.so.1 [0]

[symphorien]

Bisected down to

$  git bisect view --graph --oneline
*   f2499cd5ec2 Merge pull request #221215 from samuela/samuela/snappy
|\  
| * c3a42a047cf snappy: 1.1.9 -> 1.1.10
* 19680e9902c Merge pull request #217568 from trofi/stdenv-parallel-install
* 578fb7fd1ff Merge pull request #220557 from mweinelt/libxcrypt-strong
* 4472cf44eba treewide: Make yescrypt the default algorithm for pam_unix.so
* 909f394f28c pam: Make libxcrypt a non-optional dependency
* 0d7cd666520 nixos/users-groups: Update password scheme validation
* 4e300e071b9 libxcrypt: Build only with strong hashes

and weirdly disabling parallel installs (ie undoing 19680e9) does fix the issue, I don't know why.

Please test #225339 to confirm it is the right solution.

[dacioromero]

I overlayed your PR into my configuration and now scanimage -L works!