Debugging printing to a remote printer

pdo debian eng cups firewalld

I upgraded to Debian testing/trixie, and my network printer stopped appearing in print dialogs. These are notes from the debugging session.

Check firewall configuration

I tried out kde, which installed plasma-firewall, which installed firewalld, which closed by default the ports used for printing.

For extra fun, appindicators are not working in Gnome and so firewall-applet is currently useless, although one can run firewall-config manually, or use the command line that might be more user friendly than the UI.

Step 1: change the zone for the home wifi to "Home":

firewall-cmd  --zone home --list-interfaces
firewall-cmd  --zone home --add-interface wlp1s0

Step 2: make sure the home zone can print:

firewall-cmd --zone home --list-services
firewall-cmd --zone home --add-service=ipp
firewall-cmd --zone home --add-service=ipp-client
firewall-cmd --zone home --add-service=mdns

I searched and searched but I could not find out whether ipp is needed, ipp-client is needed, or both are needed.

Check if avahi can see the printer

Is the printer advertised correctly over mdns?

When it didn't work:

$ avahi-browse -avrt
= wlp1s0 IPv6 Brother HL-2030 series @ server                UNIX Printer         local
   hostname = [server.local]
   address = [...ipv6 address...]
   port = [0]
   txt = []
= wlp1s0 IPv4 Brother HL-2030 series @ server                UNIX Printer         local
   hostname = [server.local]
   address = [...ipv4 address...]
   port = [0]
   txt = []

$ avahi-browse -rt _ipp._tcp
[empty]

When it works:

$ avahi-browse -avrt
= wlp1s0 IPv6 Brother HL-2030 series @ server                Secure Internet Printer local
   hostname = [server.local]
   address = [...ipv6 address...]
   port = [631]
   txt = ["printer-type=0x1046" "printer-state=3" "Copies=T" "TLS=1.2" "UUID=…" "URF=DM3" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "product=(HL-2030 series)" "priority=0" "note=" "adminurl=https://server.local.:631/printers/Brother_HL-2030_series" "ty=Brother HL-2030 series, using brlaser v6" "rp=printers/Brother_HL-2030_series" "qtotal=1" "txtvers=1"]
= wlp1s0 IPv6 Brother HL-2030 series @ server                UNIX Printer         local
   hostname = [server.local]
   address = [...ipv6 address...]
   port = [0]
   txt = []
= wlp1s0 IPv4 Brother HL-2030 series @ server                Secure Internet Printer local
   hostname = [server.local]
   address = [...ipv4 address...]
   port = [631]
   txt = ["printer-type=0x1046" "printer-state=3" "Copies=T" "TLS=1.2" "UUID=…" "URF=DM3" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "product=(HL-2030 series)" "priority=0" "note=" "adminurl=https://server.local.:631/printers/Brother_HL-2030_series" "ty=Brother HL-2030 series, using brlaser v6" "rp=printers/Brother_HL-2030_series" "qtotal=1" "txtvers=1"]
= wlp1s0 IPv4 Brother HL-2030 series @ server                UNIX Printer         local
   hostname = [server.local]
   address = [...ipv4 address...]
   port = [0]
   txt = []

$ avahi-browse -rt _ipp._tcp
+ wlp1s0 IPv6 Brother HL-2030 series @ server                Internet Printer     local
+ wlp1s0 IPv4 Brother HL-2030 series @ server                Internet Printer     local
= wlp1s0 IPv4 Brother HL-2030 series @ server                Internet Printer     local
   hostname = [server.local]
   address = [...ipv4 address...]
   port = [631]
   txt = ["printer-type=0x1046" "printer-state=3" "Copies=T" "TLS=1.2" "UUID=…" "URF=DM3" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "product=(HL-2030 series)" "priority=0" "note=" "adminurl=https://server.local.:631/printers/Brother_HL-2030_series" "ty=Brother HL-2030 series, using brlaser v6" "rp=printers/Brother_HL-2030_series" "qtotal=1" "txtvers=1"]
= wlp1s0 IPv6 Brother HL-2030 series @ server                Internet Printer     local
   hostname = [server.local]https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1092109
   address = [...ipv6 address...]
   port = [631]
   txt = ["printer-type=0x1046" "printer-state=3" "Copies=T" "TLS=1.2" "UUID=…" "URF=DM3" "pdl=application/octet-stream,application/pdf,application/postscript,image/jpeg,image/png,image/pwg-raster,image/urf" "product=(HL-2030 series)" "priority=0" "note=" "adminurl=https://server.local.:631/printers/Brother_HL-2030_series" "ty=Brother HL-2030 series, using brlaser v6" "rp=printers/Brother_HL-2030_series" "qtotal=1" "txtvers=1"]

Check if cups can see the printer

From CUPS' Using Network Printers:

$ /usr/sbin/lpinfo --include-schemes dnssd -v

network dnssd://Brother%20HL-2030%20series%20%40%20server._ipp._tcp.local/cups?uuid=…

Debugging session interrupted

At this point, the printer appeared.

It could be that:

lpinfo somehow made it work
after opening ipp services on the firewall and spending enough minutes researching, eventually cups-browsed could see the printer
logging into the remote server to list printers woke it up somehow
the printer just realised I was level headed, determined and not in a hurry.

In the end, debugging failed successfully, and this log now remains as a reference for possible further issues.