swupdate 2025.12 delta update with zchunk

[simone bongini]

Hello,

i'm successfull using delta updates with zchunk to update ext4 A/B partition.

But i'm seen something strange when I'm tring to update the standby partition with exactely the same ext4 blob of the running partition.

Indeed also if the running ext4 (mounted as read-only dm-verity) partition is the same as the remote, so nothing to download, swupdate try to download a range (about 50byte) and then stuck for "zstd_step : 481 : ZSTD_decompressStream failed"

[TRACE] : SWUPDATE running :  [zck_log_toswupdate] : (zck_end_chunk) Finished chunk size: 31234
[INFO ] : SWUPDATE running :  [get_total_size] : Total bytes to be reused     :     81364478

[INFO ] : SWUPDATE running :  [get_total_size] : Total bytes to be downloaded :           51

[INFO ] : SWUPDATE running :  [install_delta] : Size of artifact to be installed : 81387520
[TRACE] : SWUPDATE running :  [install_single_image] : Found installer for stream asw.ext4.verity.header raw
[TRACE] : SWUPDATE running :  [trigger_download] : Range request : 26900125-26900175
[DEBUG] : SWUPDATE running :  [read_settings_file] : Reading config file /etc/swupdate.cfg
[DEBUG] : SWUPDATE running :  [read_module_settings] : Reading config settings for module delta
[DEBUG] : SWUPDATE running :  [channel_set_options] : cURL's low download speed timeout is disabled, this is most probably not what you want. Adapted it to 300s instead.

[TRACE] : SWUPDATE running :  [channel_log_effective_url] : Channel's effective URL resolved to http: private_address
[DEBUG] : SWUPDATE running :  [channel_get_file] : Channel downloaded 51 bytes ~ 0 MiB.
[ERROR] : SWUPDATE failed [0] ERROR cpio_utils.c : zstd_step : 481 : ZSTD_decompressStream failed: Unknown frame descriptor
[ERROR] : SWUPDATE failed [0] ERROR delta_handler.c : network_process_data : 181 : copyfile failed !
[ERROR] : SWUPDATE failed [0] ERROR delta_handler.c : install_delta : 1096 : Delta Update fails : aborting
[TRACE] : SWUPDATE running :  [zck_log_toswupdate] : (comp_close) Closing compression
[TRACE] : SWUPDATE running :  [zck_log_toswupdate] : (comp_close) Closing compression
[TRACE] : SWUPDATE running :  [install_single_image] : Installer for delta not successful !
[ERROR] : SWUPDATE failed [1] Installation failed !
[ERROR] : SWUPDATE failed [0] ERROR install_from_file.c : endupdate : 55 : SWUpdate *failed* !
[TRACE] : SWUPDATE running :  [unlink_sockets] : unlink socket /tmp/swupdateprog
[TRACE] : SWUPDATE running :  [unlink_sockets] : unlink socket /tmp/sockinstctrl
[TRACE] : SWUPDATE running :  [network_initializer] : Main thread sleep again !

Note that when I have something different to install in standby partition, everithing works like a charme..

Seems a bug, have you ever been something similar?!

Thanks,

Simone