dnssd.c: Let Avahi decide the hostname for register #902
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zdohnal
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Feb 29, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member reghost, which is used for saving listen-hostname, - new public accessors for that member, papplSystemSetRegHostName() and papplSystemGetRegHostName() - user can set the member to localhost or to the current hostname - dnssd functions will check this member, and if it is localhost, it will use loopback index - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN) The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Feb 29, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member reghost, which is used for saving listen-hostname, - new public accessors for that member, papplSystemSetRegHostName() and papplSystemGetRegHostName() - user can set the member to localhost or to the current hostname - dnssd functions will check this member, and if it is localhost, it will use loopback index - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN) The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Feb 29, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member reghost, which is used for saving listen-hostname, - new public accessors for that member, papplSystemSetRegHostName() and papplSystemGetRegHostName() - user can set the member to localhost or to the current hostname - dnssd functions will check this member, and if it is localhost, it will use loopback index - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN) The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 1, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member reghost, which is used for saving listen-hostname, - new public accessors for that member, papplSystemSetRegHostName() and papplSystemGetRegHostName() - user can set the member to localhost or to the current hostname - dnssd functions will check this member, and if it is localhost, it will use loopback index - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN) The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 1, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member reghost, which is used for saving listen-hostname, - new public accessors for that member, papplSystemSetRegHostName() and papplSystemGetRegHostName() - user can set the member to localhost or to the current hostname - dnssd functions will check this member, and if it is localhost, it will use loopback index - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN) The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
michaelrsweet
requested changes
Mar 1, 2024
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 6, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member listen_hostname, which is used for saving listen-hostname, - the member will be set in `papplSystemAddListeners()` - in case the listener is domain socket or the listener name is not defined and no hostname is set, listen_hostname is NULL and disables advertising, - dnssd functions will check this member, and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 6, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting listen-hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. This can be prevented if the machine hostname is changed to localhost, but that's not desired on machines IIUC. The PR does the following: - introduced new pappl system member listen_hostname, which is used for saving listen-hostname, - the member will be set in `papplSystemAddListeners()` - in case the listener is domain socket or the listener name is not defined and no hostname is set, listen_hostname is NULL and disables advertising, - dnssd functions will check this member, and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if reghost is set to localhost, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 13, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting system hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. The PR does the following: - set/reset system hostname in `papplSystemAddListeners()` directly, not via API. It prevents changing machine' hostname. - if the listener is domain socket, system hostname is freed if needed. This functionality disables advertising. - dnssd function will check the hostname and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if system hostname is set to localhost internally, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 13, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting system hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. The PR does the following: - set/reset system hostname in `papplSystemAddListeners()` directly, not via API. It prevents changing machine' hostname. - dnssd function will check the hostname and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if system hostname is set to localhost internally, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
zdohnal
added a commit
to zdohnal/pappl
that referenced
this pull request
Mar 14, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting system hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. The PR does the following: - set/reset system hostname in `papplSystemAddListeners()` directly, not via API. It prevents changing machine' hostname. - dnssd function will check the hostname and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if system hostname is set to localhost internally, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
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Sometimes it happens Avahi can register local service under a hostname of different machine, if the local daemon enforces the hostname as parameter, but the hostname is already taken by different machine. If NULL is passed as hostname into Avahi API for adding services, Avahi figures out hostname and IP address to use based on interface index passed into the function, and handles hostname changes as well. This way enables adding services to localhost only, because Avahi takes localhost as an invalid FQDN (unless the machine hostname is localhost). The current way of how to share the service on localhost only in Avahi is to use interface index for loopback and pass NULL as hostname.
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zdohnal
added a commit
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Mar 15, 2024
In case users would like to prevent sharing services from printer applications to local network, restrict it to localhost and let CUPS do the sharing. This can be done by setting system hostname in PAPPL API - this prevents accessing the public addresses, but the service is still published on those public addresses. The PR does the following: - set/reset system hostname in `papplSystemAddListeners()` directly, not via API. It prevents changing machine' hostname. - dnssd function will check the hostname and if it is localhost or matching IP address, it will use loopback index, - in case of Avahi it passes NULL as hostname to let Avahi decide what hostname to use (in case of hostname conflicts - and Avahi forbids using localhost if it is not FQDN). The result is that if system hostname is set to localhost internally, the service is published on .local address, but resolved to loopback because CUPS uses DNS-SD names in URIs. PAPPL 2.x version requires CUPS PR OpenPrinting/cups#902 to have it working.
michaelrsweet
requested changes
Apr 6, 2024
| // Avahi client callback is first run when client is created. | ||
| // Ignore the initial call to prevent regenerating hostnames | ||
| // and registrations for nothing... | ||
| dnssd->config_changes = -1; |
There was a problem hiding this comment.
config_changes is size_t so you can't assign it a negative value...
| @@ -1096,7 +1101,7 @@ cupsDNSSDServiceAdd( | |||
| *subtypes++ = '\0'; | |||
|
|
|||
| // Add the service entry... | |||
| if ((error = avahi_entry_group_add_service_strlst(service->group, avahi_if_index(service->if_index), AVAHI_PROTO_UNSPEC, /*flags*/0, service->name, regtype, domain, host, port, txtrec)) < 0) | |||
| if ((error = avahi_entry_group_add_service_strlst(service->group, avahi_if_index(service->if_index), AVAHI_PROTO_UNSPEC, /*flags*/0, service->name, regtype, domain, NULL, port, txtrec)) < 0) | |||
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This really needs to be "host" unless it is "localhost"...
michaelrsweet
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Apr 6, 2024
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Sometimes it happens Avahi can register local service under a hostname of different machine, if the local daemon enforces the hostname as parameter, but the hostname is already taken by different machine.
If NULL is passed as hostname into Avahi API for adding services, Avahi figures out hostname and IP address to use based on interface index passed into the function, and handles hostname changes as well.
This way enables adding services to localhost only, because Avahi takes localhost as an invalid FQDN (unless the machine hostname is localhost). The current way of how to share the service on localhost only in Avahi is to use interface index for loopback and pass NULL as hostname.