refactoring: read_name and name compression

[keepsimple1]

Re-implemented read_name that hopefully help resolve this comment: #468 (comment)

[Phyks]

Hi,

I did a quick test rebuilding netmuxd against this branch, and it seems the issue is still present:

$ sudo -u usbmux RUST_LOG=debug ./netmuxd --disable-unix --host 127.0.0.1
Starting netmuxd
[2026-08-17T18:34:31Z INFO  netmuxd] Logger initialized
[2026-08-17T18:34:31Z INFO  netmuxd] Collected arguments, proceeding
[2026-08-17T18:34:31Z INFO  netmuxd::mdns] Starting mDNS discovery for _apple-mobdev2._tcp.local. with mdns-sd
Listening on 127.0.0.1:27015
WARNING: Running in host mode will not work unless you are running a daemon in unix mode as well
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V4 on lo addr 127.0.0.1
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V4 on ens18 addr 10.42.4.102
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V4 on br-c2548c7b1cc0 addr 172.18.0.1
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V4 on br-f78b176b13fe addr 172.19.0.1
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on lo addr ::1 with index 1
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on ens18 addr 2a01:XXX with index 2
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on ens18 addr fe80::XXX with index 2
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] failed to join multicast: fe80::XXX: PKT join multicast group on addr fe80::XXX: Address already in use (os error 98). Skipped.
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on br-c2548c7b1cc0 addr fe80::XXX with index 21
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on br-f78b176b13fe addr fe80::XXX with index 22
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on vethc2fd722 addr fe80::XXX with index 23
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on vethfcd878d addr fe80::XXX with index 24
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on vethd5c140a addr fe80::XXX with index 25
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on vethf260437 addr fe80::XXX with index 26
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on veth1a365cc addr fe80::XXX with index 27
[2026-08-17T18:34:31Z DEBUG mdns_sd::service_daemon] join multicast group V6 on veth70758b7 addr fe80::XXX with index 28
[2026-08-17T18:37:05Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 106 must be less than the start offset 100
[2026-08-17T18:38:13Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 106 must be less than the start offset 100

RUST_LOG=trace is very verbose, and does not seem to provide much more details. I'm not sure if there is any extra logging that would be helpful?

I'll make a proper and clean tcpdump and report back with it! :)

[keepsimple1]

I did a quick test rebuilding netmuxd against this branch, and it seems the issue is still present:

from your log, it seems that the test was not using this PR branch? The following log line no longer exists in this branch:

[2026-08-17T18:37:05Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 106 must be less than the start offset 100

Just a note, you can update the dependency using the following :

mdns-sd = { git = "https://github.com/keepsimple1/mdns-sd", branch = "name-pointer" }

[Phyks]

Oops, sorry, thanks for pointing out. I had updated the Cargo.toml but forgot to run a cargo update prior to build. Upon rebuild, these are the typical log lines that I get:

2026-08-18T07:15:58Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:15:59Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:15:59Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:16:00Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:16:01Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:16:05Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:25:06Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:25:07Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:25:07Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:25:08Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:25:09Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:25:13Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:34:41Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:34:42Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:34:42Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:34:43Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:34:44Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 150 at offset 148 must point backwards
[2026-08-18T07:34:45Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:34:48Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Invalid name compression: pointer 169 at offset 125 must point backwards
[2026-08-18T07:39:54Z DEBUG mdns_sd::service_daemon] Invalid incoming DNS message: Bad name with invalid length: 0x6e offset 80, data (so far): [0, 0, 84, 0, 0, 0, 0, d, 0, 0, 0, 0, 8, 5f, 61, 69, 72, 70, 6c, 61, 79, 4, 5f, 74, 63, 70, 5, 6c, 6f, 63, 61, 6c, 0, 0, c, 0, 1, 0, 0, 11, 94, 0, 13, 10, 44, 65, 6e, 6f, 6e, 20, 41, 56, 43, 2d, 58, 33, 38, 30, 30, 48, c0, c, 1d, 38, 43, 41, 39, 36, 46, 33, 35, 31, 32, 36, 31, 40, 44, 65, 6e, 6f]

Thanks!