On Tue, 2022-02-01 at 22:38 +0000, Barry wrote: > I thought that mDNS that Avahi implements only uses multicast on the > LAN. You could set up multicast across multiple LAN segments. > > How does that end up getting answers from the internet? > Especially when all ISPs block multicast it seems. It shouldn't (go out on the internet). But what happens when something doesn't get an answer from within the LAN, or, some part of your LAN isn't using mDNS? Is *it*, then, going to try a normal DNS query? *It* being something on your computer, not specifically Avahi, querying beyond the internal LAN. On a whim, I've just tried this on my system which doesn't use mDNS: $ dig router.local ; <<>> DiG 9.11.4-P2-RedHat-9.11.4-26.P2.el7_9.8 <<>> router.local ;; global options: +cmd ;; Got answer: ;; WARNING: .local is reserved for Multicast DNS ;; You are currently testing what happens when an mDNS query is leaked to DNS ;; ->>HEADER<<- opcode: QUERY, status: NXDOMAIN, id: 41071 ;; flags: qr rd ra ad; QUERY: 1, ANSWER: 0, AUTHORITY: 1, ADDITIONAL: 1 ;; OPT PSEUDOSECTION: ; EDNS: version: 0, flags:; udp: 4096 ;; QUESTION SECTION: ;router.local. IN A ;; AUTHORITY SECTION: . 10800 IN SOA a.root-servers.net. nstld.verisign-grs.com. 2022020101 1800 900 604800 86400 ;; Query time: 86 msec ;; SERVER: 127.0.0.1#53(127.0.0.1) ;; WHEN: Wed Feb 02 13:17:02 ACDT 2022 ;; MSG SIZE rcvd: 116 So, the "dig" tool, at least, is prepared to break out of the confines of my LAN. And, so it would seem, is BIND (I have BIND running on this machine), and dig queried it. I suppose I should customise BIND to internally abort .local domain name queries. Though I think I have turned off mDNS/Avahi, et al, in all the devices in the LAN. On the other hand: $ nslookup router.local Server: 127.0.0.1 Address: 127.0.0.1#53 ** server can't find router.local: NXDOMAIN Doesn't really tell me how far the query went before it got nixed. -- uname -rsvp Linux 3.10.0-1160.53.1.el7.x86_64 #1 SMP Fri Jan 14 13:59:45 UTC 2022 x86_64 Boilerplate: All unexpected mail to my mailbox is automatically deleted. I will only get to see the messages that are posted to the mailing list. _______________________________________________ users mailing list -- users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe send an email to users-leave@xxxxxxxxxxxxxxxxxxxxxxx Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@xxxxxxxxxxxxxxxxxxxxxxx Do not reply to spam on the list, report it: https://pagure.io/fedora-infrastructure
