SWupdate 2025.12 Delta Updates with Zchunk

[simone bongini]

Hello,

I'm using successfully swupdate to delta update A/B ext4 partitions with zchunk, but I'm seeing a strange behaviour.

When I'm trying to install the same ext4 image to the standby partition (i.e.nothing to download, I compared the raw partition), swupdate found everytimes 50-56bytes to download. It download the range but this range has not the ZSTD header and it fails for:

" 

ZSTD_decompressStream failed: Unknown frame descriptor

"

Here a partial log

...

...

[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 !
....

....

Thanks!

SB