Custom resolver configuration do not work on Big Sur

Question

I have configured DNSmasq locally to translate all *.localhost requests to 127.0.0.1 (as per now expired RFC draft let-localhost-be-localhost).

I am running DNSmasq on non standard port (to not collide with multipass):

18411   ??  Ss     0:00.03 /nix/store/qv29whm9sdfwbxpsysjdiki6z0rylabv-dnsmasq-2.82/bin/dnsmasq --listen-address=127.0.0.1 --port=35353 --keep-in-foreground --address=/localhost/127.0.0.1

Which is ran using Launchd:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple Computer//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
<plist version="1.0">
<dict>
    <key>KeepAlive</key>
    <true/>
    <key>Label</key>
    <string>org.nixos.dnsmasq</string>
    <key>ProgramArguments</key>
    <array>
        <string>/nix/store/qv29whm9sdfwbxpsysjdiki6z0rylabv-dnsmasq-2.82/bin/dnsmasq</string>
        <string>--listen-address=127.0.0.1</string>
        <string>--port=35353</string>
        <string>--keep-in-foreground</string>
        <string>--address=/localhost/127.0.0.1</string>
    </array>
    <key>RunAtLoad</key>
    <true/>
    <key>StandardErrorPath</key>
    <string>/var/log/dnsmasq.log</string>
</dict>
</plist>

The /etc/resolver/localhost contain:

nameserver 127.0.0.1.35353

scutil --dns returns entry for localhost TLD:

DNS configuration
resolver #1
  search domain[0] : srebrna.space
  nameserver[0] : 192.168.188.199
  if_index : 6 (en0)
  flags    : Request A records
  reach    : 0x00020002 (Reachable,Directly Reachable Address)
resolver #2
  domain   : local
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 300000
resolver #3
  domain   : 254.169.in-addr.arpa
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 300200
resolver #4
  domain   : 8.e.f.ip6.arpa
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 300400
resolver #5
  domain   : 9.e.f.ip6.arpa
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 300600
resolver #6
  domain   : a.e.f.ip6.arpa
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 300800
resolver #7
  domain   : b.e.f.ip6.arpa
  options  : mdns
  timeout  : 5
  flags    : Request A records
  reach    : 0x00000000 (Not Reachable)
  order    : 301000
resolver #8
  domain   : localhost
  nameserver[0] : 127.0.0.1
  flags    : Request A records, Request AAAA records
  reach    : 0x00030002 (Reachable,Local Address,Directly Reachable Address)
DNS configuration (for scoped queries)
resolver #1
  search domain[0] : srebrna.space
  nameserver[0] : 192.168.188.199
  if_index : 6 (en0)
  flags    : Scoped, Request A records
  reach    : 0x00020002 (Reachable,Directly Reachable Address)

But I cannot resolve it:

$ host test.localhost
Host test.localhost not found: 3(NXDOMAIN)

Even while querying DNSmasq directly returns correct response:

$ dig -p 35353 @127.0.0.1 test.localhost
; <<>> DiG 9.10.6 <<>> -p 35353 @127.0.0.1 test.localhost
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 18207
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1
;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 4096
;; QUESTION SECTION:
;test.localhost.            IN  A
;; ANSWER SECTION:
test.localhost.     0   IN  A   127.0.0.1
;; Query time: 0 msec
;; SERVER: 127.0.0.1#35353(127.0.0.1)
;; WHEN: Mon Jan 25 14:23:47 CET 2021
;; MSG SIZE  rcvd: 59

My system is Big Sur 11.1

Darwin 20.2.0 Darwin Kernel Version 20.2.0: Wed Dec  2 20:39:59 PST 2020; root:xnu-7195.60.75~1/RELEASE_X86_64 x86_64 i386

Don't use host (or dig or nslookup) to test things like this, since they bypass the system resolver (and its various policies, like /etc/resolver/* files, /etc/hosts entries, etc) and just do raw DNS queries to the default server. Use e.g. dscacheutil -q host -a name test.localhost to test via the system resolver. See my answer here. — Gordon Davisson, Apr 28 '21 at 01:50

score 2 · Answer 1 · edited Apr 28 '21 at 06:18

This got me going: https://gist.github.com/petemcw/9265821

I used localhost as the .com. Not sure if it was reloading dnsmasq plist or adding the domain to the resolver, but this is what I did and have it working now, after setting up the dnsmasq configuration file:

Reload configuration and clear cache:

$ sudo launchctl unload /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist
$ sudo launchctl load /Library/LaunchDaemons/homebrew.mxcl.dnsmasq.plist
$ dscacheutil -flushcache

Setup DNS resolving:

$ sudo tee /etc/resolver/localhost > /dev/null <<EOF
nameserver 127.0.0.1
domain localhost
search_order 1
EOF

Custom resolver configuration do not work on Big Sur

1 Answers1