api: add JSON-RPC API to get ICE servers

Currently with a hardcoded TURN server
so it can be used in the UIs.

deltachat-jsonrpc/src/api.rs

@@ -8,6 +8,7 @@ use std::{collections::HashMap, str::FromStr};
 use anyhow::{anyhow, bail, ensure, Context, Result};
 pub use deltachat::accounts::Accounts;
 use deltachat::blob::BlobObject;
+use deltachat::calls::ice_servers;
 use deltachat::chat::{
     self, add_contact_to_chat, forward_msgs, get_chat_media, get_chat_msgs, get_chat_msgs_ex,
     marknoticed_chat, remove_contact_from_chat, Chat, ChatId, ChatItem, MessageListOptions,
@@ -2111,6 +2112,12 @@ impl CommandApi {
         Ok(())
     }
 
+    /// Returns JSON with ICE servers, to be used for WebRTC video calls.
+    async fn ice_servers(&self, account_id: u32) -> Result<String> {
+        let ctx = self.get_context(account_id).await?;
+        ice_servers(&ctx).await
+    }
+
     /// Makes an HTTP GET request and returns a response.
     ///
     /// `url` is the HTTP or HTTPS URL.

deltachat-rpc-client/src/deltachat_rpc_client/account.py

@@ -2,6 +2,7 @@
 
 from __future__ import annotations
 
+import json
 from dataclasses import dataclass
 from typing import TYPE_CHECKING, Optional, Union
 from warnings import warn
@@ -470,3 +471,8 @@ class Account:
     def initiate_autocrypt_key_transfer(self) -> None:
         """Send Autocrypt Setup Message."""
         return self._rpc.initiate_autocrypt_key_transfer(self.id)
+
+    def ice_servers(self) -> list:
+        """Return ICE servers for WebRTC configuration."""
+        ice_servers_json = self._rpc.ice_servers(self.id)
+        return json.loads(ice_servers_json)

deltachat-rpc-client/tests/test_calls.py

@@ -66,3 +66,10 @@ a=extmap:1 urn:ietf:params:rtp-hdrext:sdes:mid\r
     incoming_call_event = bob.wait_for_event(EventType.INCOMING_CALL)
     assert incoming_call_event.place_call_info == place_call_info
     assert incoming_call_event.has_video
+
+
+def test_ice_servers(acfactory) -> None:
+    alice = acfactory.get_online_account()
+
+    ice_servers = alice.ice_servers()
+    assert len(ice_servers) == 1

src/calls.rs

@@ -11,10 +11,12 @@ use crate::headerdef::HeaderDef;
 use crate::log::{info, warn};
 use crate::message::{self, Message, MsgId, Viewtype};
 use crate::mimeparser::{MimeMessage, SystemMessage};
+use crate::net::dns::lookup_host_with_cache;
 use crate::param::Param;
 use crate::tools::time;
 use anyhow::{Context as _, Result, ensure};
 use sdp::SessionDescription;
+use serde::Serialize;
 use std::io::Cursor;
 use std::time::Duration;
 use tokio::task;
@@ -393,5 +395,51 @@ fn sdp_has_video(sdp: &str) -> Result<bool> {
     Ok(false)
 }
 
+/// ICE server for JSON serialization.
+#[derive(Serialize, Debug, Clone, PartialEq)]
+struct IceServer {
+    /// STUN or TURN URLs.
+    pub urls: Vec<String>,
+
+    /// Username for TURN server authentication.
+    pub username: Option<String>,
+
+    /// Password for logging into the server.
+    pub credential: Option<String>,
+}
+
+/// Returns JSON with ICE servers.
+///
+/// <https://developer.mozilla.org/en-US/docs/Web/API/RTCPeerConnection/RTCPeerConnection#iceservers>
+///
+/// All returned servers are resolved to their IP addresses.
+/// The primary point of DNS lookup is that Delta Chat Desktop
+/// relies on the servers being specified by IP,
+/// because it itself cannot utilize DNS. See
+/// <https://github.com/deltachat/deltachat-desktop/issues/5447>.
+pub async fn ice_servers(context: &Context) -> Result<String> {
+    let hostname = "ci-chatmail.testrun.org";
+    let port = 3478;
+    let username = "ohV8aec1".to_string();
+    let password = "zo3theiY".to_string();
+
+    // Do not use cache because there is no TLS.
+    let load_cache = false;
+    let urls: Vec<String> = lookup_host_with_cache(context, hostname, port, "", load_cache)
+        .await?
+        .into_iter()
+        .map(|addr| format!("turn:{addr}"))
+        .collect();
+
+    let ice_server = IceServer {
+        urls,
+        username: Some(username),
+        credential: Some(password),
+    };
+
+    let json = serde_json::to_string(&[ice_server])?;
+    Ok(json)
+}
+
 #[cfg(test)]
 mod calls_tests;