Implement DNS notifications from resolved via varlink

* The new varlink interface exposes a method to subscribe to DNS
resolutions on the system. The socket permissions are open for owner and
group only.
* Notifications are sent to subscriber(s), if any, after successful
resolution of A and AAAA records.

This feature could be used by applications for auditing/logging services
downstream of the resolver. It could also be used to asynchronously
update the firewall. For example, a system that has a tightly configured
firewall could open up connections selectively to known good hosts based
on a known allow-list of hostnames. Of course, updating the firewall
asynchronously will require other design considerations (such as
queueing packets in the user space while a verdict is made).

See also:
https://lists.freedesktop.org/archives/systemd-devel/2022-August/048202.html
https://lists.freedesktop.org/archives/systemd-devel/2022-February/047441.html

1 files changed, 1 insertions, 0 deletions

diff --git a/src/resolve/resolved-dns-query.h b/src/resolve/resolved-dns-query.h
index 43a833a08a..0b00465008 100644
--- a/src/resolve/resolved-dns-query.h
+++ b/src/resolve/resolved-dns-query.h
@@ -95,6 +95,7 @@ struct DnsQuery {
         union in_addr_union request_address;
         unsigned block_all_complete;
         char *request_address_string;
+        char *request_name;
 
         /* DNS stub information */
         DnsPacket *request_packet;