WebRTC candidate hostname gets resolved by server instead of client

[kantlivelong]

When specifying a hostname as a WebRTC candidate it appears that go2rtc resolves the hostname to an IP and passes the IP to the client instead of passing the hostname and letting the client handle the resolution. This can be problematic with environments using split DNS.

Example config:

---
webrtc:
  listen: ":8555"
  candidates:
    - host.domain.com:8555

Internally the machine running go2rtc uses DNS 192.168.1.1.

Example internal DNS result:

$ dig host.domain.com @192.168.1.1

; <<>> DiG 9.18.1-1ubuntu1.2-Ubuntu <<>> host.domain.com @192.168.1.1
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 34579
;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;host.domain.com. IN	A

;; ANSWER SECTION:
host.domain.com. 3600 IN A	192.168.1.10

;; Query time: 0 msec
;; SERVER: 192.168.1.1#53(192.168.1.1) (UDP)
;; WHEN: Wed Jan 04 14:37:30 EST 2023
;; MSG SIZE  rcvd: 80

Example external DNS result:

$ dig host.domain.com @8.8.8.8              

; <<>> DiG 9.18.1-1ubuntu1.2-Ubuntu <<>> host.domain.com @8.8.8.8
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 24206
;; flags: qr rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 512
;; QUESTION SECTION:
;host.domain.com.		IN	A

;; ANSWER SECTION:
host.domain.com.	60	IN	A	123.123.123.123

;; Query time: 55 msec
;; SERVER: 8.8.8.8#53(8.8.8.8) (UDP)
;; WHEN: Wed Jan 04 14:41:02 EST 2023
;; MSG SIZE  rcvd: 66

go2rtc version: v0.1-rc.6

[AlexxIT]

You can try to ask pion team, why they support only IP as candidate. Theoretically it can be hostname, but library will fail on that step:

go2rtc/pkg/webrtc/helper.go

Lines 26 to 32 in 368562c

	cand, err := ice.NewCandidateHost(&ice.CandidateHostConfig{
	Network: "tcp",
	Address: host,
	Port: i,
	Component: ice.ComponentRTP,
	TCPType: ice.TCPTypePassive,
	})

[kantlivelong]

Ah ha! I had a feeling that would be the case somewhere. I'll open an issue up there. Thanks!

Until then maybe it's worth mentioning in the docs that lookup is done by the server and not client?

[AlexxIT]

Please let me know if the problem is relevant