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Add details for how to set up TURN behind NAT (#11553)

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Signed-off-by: Andrew Ferrazzutti <fair@miscworks.net>
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changelog.d/11553.doc Normal file
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@ -0,0 +1 @@
Add details for how to configure a TURN server when behind a NAT. Contibuted by @AndrewFerr.

69
docs/turn-howto.md
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@ -15,8 +15,8 @@ The following sections describe how to install [coturn](<https://github.com/cotu
For TURN relaying with `coturn` to work, it must be hosted on a server/endpoint with a public IP.
Hosting TURN behind a NAT (even with appropriate port forwarding) is known to cause issues
and to often not work.
Hosting TURN behind NAT requires port forwaring and for the NAT gateway to have a public IP.
However, even with appropriate configuration, NAT is known to cause issues and to often not work.
## `coturn` setup
@ -103,7 +103,23 @@ This will install and start a systemd service called `coturn`.
denied-peer-ip=192.168.0.0-192.168.255.255
denied-peer-ip=172.16.0.0-172.31.255.255
# recommended additional local peers to block, to mitigate external access to internal services.
# https://www.rtcsec.com/article/slack-webrtc-turn-compromise-and-bug-bounty/#how-to-fix-an-open-turn-relay-to-address-this-vulnerability
no-multicast-peers
denied-peer-ip=0.0.0.0-0.255.255.255
denied-peer-ip=100.64.0.0-100.127.255.255
denied-peer-ip=127.0.0.0-127.255.255.255
denied-peer-ip=169.254.0.0-169.254.255.255
denied-peer-ip=192.0.0.0-192.0.0.255
denied-peer-ip=192.0.2.0-192.0.2.255
denied-peer-ip=192.88.99.0-192.88.99.255
denied-peer-ip=198.18.0.0-198.19.255.255
denied-peer-ip=198.51.100.0-198.51.100.255
denied-peer-ip=203.0.113.0-203.0.113.255
denied-peer-ip=240.0.0.0-255.255.255.255
# special case the turn server itself so that client->TURN->TURN->client flows work
# this should be one of the turn server's listening IPs
allowed-peer-ip=10.0.0.1
# consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
@ -123,7 +139,7 @@ This will install and start a systemd service called `coturn`.
pkey=/path/to/privkey.pem
```
In this case, replace the `turn:` schemes in the `turn_uri` settings below
In this case, replace the `turn:` schemes in the `turn_uris` settings below
with `turns:`.
We recommend that you only try to set up TLS/DTLS once you have set up a
@ -134,21 +150,33 @@ This will install and start a systemd service called `coturn`.
traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
for the UDP relay.)
1. We do not recommend running a TURN server behind NAT, and are not aware of
anyone doing so successfully.
If you want to try it anyway, you will at least need to tell coturn its
external IP address:
1. If your TURN server is behind NAT, the NAT gateway must have an external,
publicly-reachable IP address. You must configure coturn to advertise that
address to connecting clients:
```
external-ip=192.88.99.1
external-ip=EXTERNAL_NAT_IPv4_ADDRESS
```
... and your NAT gateway must forward all of the relayed ports directly
(eg, port 56789 on the external IP must be always be forwarded to port
56789 on the internal IP).
You may optionally limit the TURN server to listen only on the local
address that is mapped by NAT to the external address:
If you get this working, let us know!
```
listening-ip=INTERNAL_TURNSERVER_IPv4_ADDRESS
```
If your NAT gateway is reachable over both IPv4 and IPv6, you may
configure coturn to advertise each available address:
```
external-ip=EXTERNAL_NAT_IPv4_ADDRESS
external-ip=EXTERNAL_NAT_IPv6_ADDRESS
```
When advertising an external IPv6 address, ensure that the firewall and
network settings of the system running your TURN server are configured to
accept IPv6 traffic, and that the TURN server is listening on the local
IPv6 address that is mapped by NAT to the external IPv6 address.
1. (Re)start the turn server:
@ -216,9 +244,6 @@ connecting". Unfortunately, troubleshooting this can be tricky.
Here are a few things to try:
* Check that your TURN server is not behind NAT. As above, we're not aware of
anyone who has successfully set this up.
* Check that you have opened your firewall to allow TCP and UDP traffic to the
TURN ports (normally 3478 and 5349).
@ -234,6 +259,18 @@ Here are a few things to try:
Try removing any AAAA records for your TURN server, so that it is only
reachable over IPv4.
* If your TURN server is behind NAT:
* double-check that your NAT gateway is correctly forwarding all TURN
ports (normally 3478 & 5349 for TCP & UDP TURN traffic, and 49152-65535 for the UDP
relay) to the NAT-internal address of your TURN server. If advertising
both IPv4 and IPv6 external addresses via the `external-ip` option, ensure
that the NAT is forwarding both IPv4 and IPv6 traffic to the IPv4 and IPv6
internal addresses of your TURN server. When in doubt, remove AAAA records
for your TURN server and specify only an IPv4 address as your `external-ip`.
* ensure that your TURN server uses the NAT gateway as its default route.
* Enable more verbose logging in coturn via the `verbose` setting:
```