dns-client: if /etc/resolv.conf modifies, update the internal list of resolvers #291
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… resolvers Only affects lwt and unix. Previously, when you started an application, /etc/resolv.conf was read once at startup. When you switch to a different network, and /etc/resolv.conf is updated by DHCP, this is not reflected in the dns-client. Now, the digest of /etc/resolv.conf is stored internally, and if it changes, it is parsed again. The lwt implementation needed to be modified slightly since connect_to_ns_via_tcp carried a nameserver list, and a different task may have been woken up. Now, there are two functions and it should play out nicely.
lwt/client/dns_client_lwt.ml
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| match nameservers with | ||
| | Some (`Udp, _) -> invalid_arg "UDP is not supported" | ||
| | Some (`Tcp, ns) -> ns | ||
| | Some (`Tcp, ns) -> ns, None |
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Perhaps we should preserve whether the nameservers were passed explicitly and then not try to read resolv.conf.
In Dns_client_lwt and Dns_client_unix.
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Wouldn't it make more sense to just look at mtime on /etc/resolv.conf instead of constantly calculating digests ? |
@haesbaert we discussed this on IRC and most of it is summarized in #296. Note that the lwt implementation will reuse the connection if possible and "only" re-read resolv.conf when reconnecting. |
Ack, sorry for the noise :D |
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I made a pull request to this pull request hannesm#1 where I implement the behavior I mentioned earlier. |
Static and resolv.conf nameservers list
…er, dns-mirage, dns-client, dns-cli and dns-certify (6.2.0) CHANGES: * New opam package "dnssec" implementing dnssec validation (@reynir @hannesm) * Use custom log sources, not the default one from Logs (@reynir @hannesm) * BUGFIX dns-resolver: unlisten on the listen port, not the packet src_port (mirage/ocaml-dns#290 @hannesm) * dns-resolver: add IPv6 addresses of root servers (fixes mirage/ocaml-dns#262, @hannesm) * dns-resolver: preliminary support for DNSSec (mirage/ocaml-dns#262 @reynir @hannesm) * dns-client: when /etc/resolv.conf modifies, update the list of nameservers (mirage/ocaml-dns#291 @hannesm @reynir) * dns-cli: update to cmdliner 1.1.0 (mirage/ocaml-dns#300 @hannesm) * dns-client-mirage: add module type and nameserver_of_string and connect to allow creation of a MirageOS device (mirage/ocaml-dns#297 @dinosaure) * dns-cache: add size, capacity, and weight to metrics (mirage/ocaml-dns#301, fixes mirage/ocaml-dns#299, @hannesm)
Only affects lwt and unix.
Previously, when you started an application, /etc/resolv.conf was read once at
startup. When you switch to a different network, and /etc/resolv.conf is updated
by DHCP, this is not reflected in the dns-client.
Now, the digest of /etc/resolv.conf is stored internally, and if it changes, it
is parsed again. The lwt implementation needed to be modified slightly since
connect_to_ns_via_tcp carried a nameserver list, and a different task may have
been woken up. Now, there are two functions and it should play out nicely.
//cc @reynir addresses #243