[embedded Linux] digest and list operations work but extract fails to acquire the index file

[agambier]

Using Buildroot I've created an embedded Linux distro.
To implement the update mechanism of this system I'm evaluating casync.

The casync buildroot package compiles the commit 4ad9bcb which is almost the latest one.

The digest command works fine :
casync digest http://10.0.10.151:8080/rootfs.caidx --log-level=debug --verbose

The list command works fine too :
casync list http://10.0.10.151:8080/rootfs.caidx --log-level=debug --verbose

But the extract fails with the error .
casync extract http://10.0.10.151:8080/rootfs.caidx --log-level=debug --verbose

Here's the output :

Acquiring http://10.0.10.151:8080/rootfs.caidx...
Setting min/avg/max chunk size: 16384 / 65536 / 262144
Failed to run synchronizer: Operation not supported

The HTTP server accepted the file access (like for digest and list) :
10.0.10.184 - - [10/Aug/2022 08:27:48] "GET /rootfs.caidx HTTP/1.1" 200 -

Is there any dependency not mentioned that should be installed on the system ?

[agambier]

I got it working.
The make operation uses by default --with=best, if I use --with=unix then the extract operation works.