HP SmartTank 7305 webserver doesn't work using fqdn

[willi weikum]

I have installed my HP SmartTank 7305 AIO device using IP reservation and installed hplip-3.21.12 successfully.

The problem I was struggling was scanning failed with meaningless error 'SANE: Error during device I/O (code=9)' after hours of searching multiple reinstalls of different HPLIN versions (I'm not very experienced in Linux) I found 'journalctl -f' shows intersting lines:

'Dec 26 20:43:39 mint2020 /hp-scan[11703]: http.c 239: read_line len=24 index=24 cnt=158
Dec 26 20:43:39 mint2020 /hp-scan[11703]: http.c 322: invalid http_status=403
Dec 26 20:43:39 mint2020 /hp-scan[11703]: http.c 328: dumping len=158
Dec 26 20:43:40 mint2020 /hp-scan[11703]: io/hpmud/jd.c 694: timeout read_channel sec=1 hp:/net/Smart_Tank_7300_series?hostname=hp7305.fritz.box'

while running 'hp-scan' command

this send me to some issues describing the problem was due to disabled SNMP-write access (https://answers.launchpad.net/hplip/+question/105931) so I performed factory reset of the device without success... but trying to access the WebUI of the device using FQDN results in broken UI (empty areas) and shows exactly the same strange 403 errors in F12 browser console as mentioned in the log so once I figured out browser access works using IP address I tried to remove/add he device by IP address and it started working!!!!

AS conclusion there are multiple issues within HP SmartTank 73xx WebServer:
- it doesn't work well with FQDN (shows user 'admin' as logged in which is no true)
- prevents access to almost everything with 403 error
- doesn't allow to login (observer 403 errors in browser dev console=F12)
- prevents Linux scanning using HPLIN

as side effect I found the setting "don't redirect to https" doesn't work..

[Ikus-Soft (ikus-soft)]

Have the same problem, but in my case sane/hplip is uring "Host: localhost" instead of "Host: <ipaddress>" which is causing this issue. I manage to identify the colprit using wireshark and curl to simulate the problem.

[Ikus-Soft (ikus-soft)]

To fix this issue, I've login to the Printer Web settings and update the hostname to "localhost"