Implement Songbird driver configuration (#1074)

src/driver/config.rs

@@ -1,10 +1,81 @@
-use super::CryptoMode;
+use super::{CryptoMode, DecodeMode};
 
 /// Configuration for the inner Driver.
 ///
-/// At present, this cannot be changed.
+#[derive(Clone, Debug)]
-#[derive(Clone, Debug, Default)]
 pub struct Config {
     /// Selected tagging mode for voice packet encryption.
-    pub crypto_mode: Option<CryptoMode>,
+    ///
+    /// Defaults to [`CryptoMode::Normal`].
+    ///
+    /// Changes to this field will not immediately apply if the
+    /// driver is actively connected, but will apply to subsequent
+    /// sessions.
+    ///
+    /// [`CryptoMode::Normal`]: enum.CryptoMode.html#variant.Normal
+    pub crypto_mode: CryptoMode,
+    /// Configures whether decoding and decryption occur for all received packets.
+    ///
+    /// If voice receiving voice packets, generally you should choose [`DecodeMode::Decode`].
+    /// [`DecodeMode::Decrypt`] is intended for users running their own selective decoding,
+    /// who rely upon [user speaking events], or who need to inspect Opus packets.
+    /// If you're certain you will never need any RT(C)P events, then consider [`DecodeMode::Pass`].
+    ///
+    /// Defaults to [`DecodeMode::Decrypt`]. This is due to per-packet decoding costs,
+    /// which most users will not want to pay, but allowing speaking events which are commonly used.
+    ///
+    /// [`DecodeMode::Decode`]: enum.DecodeMode.html#variant.Decode
+    /// [`DecodeMode::Decrypt`]: enum.DecodeMode.html#variant.Decrypt
+    /// [`DecodeMode::Pass`]: enum.DecodeMode.html#variant.Pass
+    /// [user speaking events]: ../events/enum.CoreEvent.html#variant.SpeakingUpdate
+    pub decode_mode: DecodeMode,
+    /// Number of concurrently active tracks to allocate memory for.
+    ///
+    /// This should be set at, or just above, the maximum number of tracks
+    /// you expect your bot will play at the same time. Exceeding the size of
+    /// the internal queue will trigger a larger memory allocation and copy,
+    /// possibly causing the mixer thread to miss a packet deadline.
+    ///
+    /// Defaults to `1`.
+    ///
+    /// Changes to this field in a running driver will only ever increase
+    /// the capacity of the track store.
+    pub preallocated_tracks: usize,
+}
+
+impl Default for Config {
+    fn default() -> Self {
+        Self {
+            crypto_mode: CryptoMode::Normal,
+            decode_mode: DecodeMode::Decrypt,
+            preallocated_tracks: 1,
+        }
+    }
+}
+
+impl Config {
+    /// Sets this `Config`'s chosen cryptographic tagging scheme.
+    pub fn crypto_mode(mut self, crypto_mode: CryptoMode) -> Self {
+        self.crypto_mode = crypto_mode;
+        self
+    }
+
+    /// Sets this `Config`'s received packet decryption/decoding behaviour.
+    pub fn decode_mode(mut self, decode_mode: DecodeMode) -> Self {
+        self.decode_mode = decode_mode;
+        self
+    }
+
+    /// Sets this `Config`'s number of tracks to preallocate.
+    pub fn preallocated_tracks(mut self, preallocated_tracks: usize) -> Self {
+        self.preallocated_tracks = preallocated_tracks;
+        self
+    }
+
+    /// This is used to prevent changes which would invalidate the current session.
+    pub(crate) fn make_safe(&mut self, previous: &Config, connected: bool) {
+        if connected {
+            self.crypto_mode = previous.crypto_mode;
+        }
+    }
 }

src/driver/connection/mod.rs

@@ -41,8 +41,6 @@ impl Connection {
         interconnect: &Interconnect,
         config: &Config,
     ) -> Result<Connection> {
-        let crypto_mode = config.crypto_mode.unwrap_or(CryptoMode::Normal);
-
         let url = generate_url(&mut info.endpoint)?;
 
         #[cfg(all(feature = "rustls", not(feature = "native")))]
@@ -95,7 +93,7 @@ impl Connection {
         let ready =
             ready.expect("Ready packet expected in connection initialisation, but not found.");
 
-        if !has_valid_mode(&ready.modes, crypto_mode) {
+        if !has_valid_mode(&ready.modes, config.crypto_mode) {
             return Err(Error::CryptoModeUnavailable);
         }
 
@@ -147,14 +145,14 @@ impl Connection {
                     protocol: "udp".into(),
                     data: ProtocolData {
                         address,
-                        mode: crypto_mode.to_request_str().into(),
+                        mode: config.crypto_mode.to_request_str().into(),
                         port: view.get_port(),
                     },
                 }))
                 .await?;
         }
 
-        let cipher = init_cipher(&mut client, crypto_mode).await?;
+        let cipher = init_cipher(&mut client, config.crypto_mode).await?;
 
         info!("Connected to: {}", info.endpoint);
 
@@ -169,6 +167,7 @@ impl Connection {
 
         let mix_conn = MixerConnection {
             cipher: cipher.clone(),
+            crypto_state: config.crypto_mode.into(),
             udp_rx: udp_receiver_msg_tx,
             udp_tx: udp_sender_msg_tx,
         };
@@ -193,7 +192,7 @@ impl Connection {
             interconnect.clone(),
             udp_receiver_msg_rx,
             cipher,
-            crypto_mode,
+            config.clone(),
             udp_rx,
         ));
         tokio::spawn(udp_tx::runner(udp_sender_msg_rx, ssrc, udp_tx));

src/driver/crypto.rs

@@ -1,38 +1,223 @@
 //! Encryption schemes supported by Discord's secure RTP negotiation.
+use byteorder::{NetworkEndian, WriteBytesExt};
+use discortp::{rtp::RtpPacket, MutablePacket};
+use rand::Rng;
+use std::num::Wrapping;
+use xsalsa20poly1305::{
+    aead::{AeadInPlace, Error as CryptoError},
+    Nonce,
+    Tag,
+    XSalsa20Poly1305 as Cipher,
+    NONCE_SIZE,
+    TAG_SIZE,
+};
 
 /// Variants of the XSalsa20Poly1305 encryption scheme.
-///
-/// At present, only `Normal` is supported or selectable.
 #[derive(Clone, Copy, Debug, Eq, PartialEq)]
 #[non_exhaustive]
-pub enum Mode {
+pub enum CryptoMode {
     /// The RTP header is used as the source of nonce bytes for the packet.
     ///
     /// Equivalent to a nonce of at most 48b (6B) at no extra packet overhead:
     /// the RTP sequence number and timestamp are the varying quantities.
     Normal,
     /// An additional random 24B suffix is used as the source of nonce bytes for the packet.
+    /// This is regenerated randomly for each packet.
     ///
     /// Full nonce width of 24B (192b), at an extra 24B per packet (~1.2 kB/s).
     Suffix,
-    /// An additional random 24B suffix is used as the source of nonce bytes for the packet.
+    /// An additional random 4B suffix is used as the source of nonce bytes for the packet.
+    /// This nonce value increments by `1` with each packet.
     ///
     /// Nonce width of 4B (32b), at an extra 4B per packet (~0.2 kB/s).
     Lite,
 }
 
-impl Mode {
+impl From<CryptoState> for CryptoMode {
+    fn from(val: CryptoState) -> Self {
+        use CryptoState::*;
+        match val {
+            Normal => CryptoMode::Normal,
+            Suffix => CryptoMode::Suffix,
+            Lite(_) => CryptoMode::Lite,
+        }
+    }
+}
+
+impl CryptoMode {
     /// Returns the name of a mode as it will appear during negotiation.
     pub fn to_request_str(self) -> &'static str {
-        use Mode::*;
+        use CryptoMode::*;
         match self {
             Normal => "xsalsa20_poly1305",
             Suffix => "xsalsa20_poly1305_suffix",
             Lite => "xsalsa20_poly1305_lite",
         }
     }
+
+    /// Returns the number of bytes each nonce is stored as within
+    /// a packet.
+    pub fn nonce_size(self) -> usize {
+        use CryptoMode::*;
+        match self {
+            Normal => RtpPacket::minimum_packet_size(),
+            Suffix => NONCE_SIZE,
+            Lite => 4,
+        }
     }
 
-// TODO: implement encrypt + decrypt + nonce selection for each.
+    /// Returns the number of bytes occupied by the encryption scheme
-// This will probably need some research into correct handling of
+    /// which fall before the payload.
-// padding, reported length, SRTP profiles, and so on.
+    pub fn payload_prefix_len(self) -> usize {
+        TAG_SIZE
+    }
+
+    /// Returns the number of bytes occupied by the encryption scheme
+    /// which fall after the payload.
+    pub fn payload_suffix_len(self) -> usize {
+        use CryptoMode::*;
+        match self {
+            Normal => 0,
+            Suffix | Lite => self.nonce_size(),
+        }
+    }
+
+    /// Calculates the number of additional bytes required compared
+    /// to an unencrypted payload.
+    pub fn payload_overhead(self) -> usize {
+        self.payload_prefix_len() + self.payload_suffix_len()
+    }
+
+    /// Extracts the byte slice in a packet used as the nonce, and the remaining mutable
+    /// portion of the packet.
+    fn nonce_slice<'a>(self, header: &'a [u8], body: &'a mut [u8]) -> (&'a [u8], &'a mut [u8]) {
+        use CryptoMode::*;
+        match self {
+            Normal => (header, body),
+            Suffix | Lite => {
+                let len = body.len();
+                let (body_left, nonce_loc) = body.split_at_mut(len - self.payload_suffix_len());
+                (&nonce_loc[..self.nonce_size()], body_left)
+            },
+        }
+    }
+
+    /// Decrypts a Discord RT(C)P packet using the given key.
+    ///
+    /// If successful, this returns the number of bytes to be ignored from the
+    /// start and end of the packet payload.
+    #[inline]
+    pub(crate) fn decrypt_in_place(
+        self,
+        packet: &mut impl MutablePacket,
+        cipher: &Cipher,
+    ) -> Result<(usize, usize), CryptoError> {
+        let header_len = packet.packet().len() - packet.payload().len();
+        let (header, body) = packet.packet_mut().split_at_mut(header_len);
+        let (slice_to_use, body_remaining) = self.nonce_slice(header, body);
+
+        let mut nonce = Nonce::default();
+        let nonce_slice = if slice_to_use.len() == NONCE_SIZE {
+            Nonce::from_slice(&slice_to_use[..NONCE_SIZE])
+        } else {
+            let max_bytes_avail = slice_to_use.len();
+            nonce[..self.nonce_size().min(max_bytes_avail)].copy_from_slice(slice_to_use);
+            &nonce
+        };
+
+        let body_start = self.payload_prefix_len();
+        let body_tail = self.payload_suffix_len();
+
+        let (tag_bytes, data_bytes) = body_remaining.split_at_mut(body_start);
+        let tag = Tag::from_slice(tag_bytes);
+
+        Ok(cipher
+            .decrypt_in_place_detached(nonce_slice, b"", data_bytes, tag)
+            .map(|_| (body_start, body_tail))?)
+    }
+
+    /// Encrypts a Discord RT(C)P packet using the given key.
+    ///
+    /// Use of this requires that the input packet has had a nonce generated in the correct location,
+    /// and `payload_len` specifies the number of bytes after the header including this nonce.
+    #[inline]
+    pub fn encrypt_in_place(
+        self,
+        packet: &mut impl MutablePacket,
+        cipher: &Cipher,
+        payload_len: usize,
+    ) -> Result<(), CryptoError> {
+        let header_len = packet.packet().len() - packet.payload().len();
+        let (header, body) = packet.packet_mut().split_at_mut(header_len);
+        let (slice_to_use, body_remaining) = self.nonce_slice(header, &mut body[..payload_len]);
+
+        let mut nonce = Nonce::default();
+        let nonce_slice = if slice_to_use.len() == NONCE_SIZE {
+            Nonce::from_slice(&slice_to_use[..NONCE_SIZE])
+        } else {
+            nonce[..self.nonce_size()].copy_from_slice(slice_to_use);
+            &nonce
+        };
+
+        // body_remaining is now correctly truncated by this point.
+        // the true_payload to encrypt follows after the first TAG_LEN bytes.
+        let tag =
+            cipher.encrypt_in_place_detached(nonce_slice, b"", &mut body_remaining[TAG_SIZE..])?;
+        body_remaining[..TAG_SIZE].copy_from_slice(&tag[..]);
+
+        Ok(())
+    }
+}
+
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[non_exhaustive]
+pub(crate) enum CryptoState {
+    Normal,
+    Suffix,
+    Lite(Wrapping<u32>),
+}
+
+impl From<CryptoMode> for CryptoState {
+    fn from(val: CryptoMode) -> Self {
+        use CryptoMode::*;
+        match val {
+            Normal => CryptoState::Normal,
+            Suffix => CryptoState::Suffix,
+            Lite => CryptoState::Lite(Wrapping(rand::random::<u32>())),
+        }
+    }
+}
+
+impl CryptoState {
+    /// Writes packet nonce into the body, if required, returning the new length.
+    pub fn write_packet_nonce(
+        &mut self,
+        packet: &mut impl MutablePacket,
+        payload_end: usize,
+    ) -> usize {
+        let mode = self.kind();
+        let endpoint = payload_end + mode.payload_suffix_len();
+
+        use CryptoState::*;
+        match self {
+            Suffix => {
+                rand::thread_rng().fill(&mut packet.payload_mut()[payload_end..endpoint]);
+            },
+            Lite(mut i) => {
+                (&mut packet.payload_mut()[payload_end..endpoint])
+                    .write_u32::<NetworkEndian>(i.0)
+                    .expect(
+                        "Nonce size is guaranteed to be sufficient to write u32 for lite tagging.",
+                    );
+                i += Wrapping(1);
+            },
+            _ => {},
+        }
+
+        endpoint
+    }
+
+    pub fn kind(&self) -> CryptoMode {
+        CryptoMode::from(*self)
+    }
+}

src/driver/decode_mode.rs

@@ -0,0 +1,32 @@
+/// Decode behaviour for received RTP packets within the driver.
+#[derive(Clone, Copy, Debug, Eq, PartialEq)]
+#[non_exhaustive]
+pub enum DecodeMode {
+    /// Packets received from Discord are handed over to events without any
+    /// changes applied.
+    ///
+    /// No CPU work involved.
+    ///
+    /// *BEWARE: this will almost certainly break [user speaking events].
+    /// Silent frame detection only works if extensions can be parsed or
+    /// are not present, as they are encrypted.
+    /// This event requires such functionality.*
+    ///
+    /// [user speaking events]: ../events/enum.CoreEvent.html#variant.SpeakingUpdate
+    Pass,
+    /// Decrypts the body of each received packet.
+    ///
+    /// Small per-packet CPU use.
+    Decrypt,
+    /// Decrypts and decodes each received packet, correctly accounting for losses.
+    ///
+    /// Larger per-packet CPU use.
+    Decode,
+}
+
+impl DecodeMode {
+    /// Returns whether this mode will decrypt received packets.
+    pub fn should_decrypt(self) -> bool {
+        self != DecodeMode::Pass
+    }
+}

src/driver/mod.rs

@@ -11,11 +11,13 @@
 mod config;
 pub(crate) mod connection;
 mod crypto;
+mod decode_mode;
 pub(crate) mod tasks;
 
 pub use config::Config;
 use connection::error::Result;
-pub use crypto::Mode as CryptoMode;
+pub use crypto::*;
+pub use decode_mode::DecodeMode;
 
 use crate::{
     events::EventData,
@@ -187,6 +189,13 @@ impl Driver {
         self.send(CoreMessage::SetTrack(None))
     }
 
+    /// Sets the configuration for this driver.
+    #[instrument(skip(self))]
+    pub fn set_config(&mut self, config: Config) {
+        self.config = config.clone();
+        self.send(CoreMessage::SetConfig(config))
+    }
+
     /// Attach a global event handler to an audio context. Global events may receive
     /// any [`EventContext`].
     ///

src/driver/tasks/message/core.rs

@@ -1,5 +1,5 @@
 use crate::{
-    driver::connection::error::Error,
+    driver::{connection::error::Error, Config},
     events::EventData,
     tracks::Track,
     Bitrate,
@@ -16,6 +16,7 @@ pub enum CoreMessage {
     AddTrack(Track),
     SetBitrate(Bitrate),
     AddEvent(EventData),
+    SetConfig(Config),
     Mute(bool),
     Reconnect,
     FullReconnect,

src/driver/tasks/message/mixer.rs

@@ -1,11 +1,16 @@
 use super::{Interconnect, UdpRxMessage, UdpTxMessage, WsMessage};
 
-use crate::{tracks::Track, Bitrate};
+use crate::{
+    driver::{Config, CryptoState},
+    tracks::Track,
+    Bitrate,
+};
 use flume::Sender;
 use xsalsa20poly1305::XSalsa20Poly1305 as Cipher;
 
 pub(crate) struct MixerConnection {
     pub cipher: Cipher,
+    pub crypto_state: CryptoState,
     pub udp_rx: Sender<UdpRxMessage>,
     pub udp_tx: Sender<UdpTxMessage>,
 }
@@ -20,13 +25,17 @@ impl Drop for MixerConnection {
 pub(crate) enum MixerMessage {
     AddTrack(Track),
     SetTrack(Option<Track>),
+
     SetBitrate(Bitrate),
+    SetConfig(Config),
     SetMute(bool),
+
     SetConn(MixerConnection, u32),
+    Ws(Option<Sender<WsMessage>>),
     DropConn,
+
     ReplaceInterconnect(Interconnect),
     RebuildEncoder,
 
-    Ws(Option<Sender<WsMessage>>),
     Poison,
 }

src/driver/tasks/message/udp_rx.rs

@@ -1,6 +1,8 @@
 use super::Interconnect;
+use crate::driver::Config;
 
 pub(crate) enum UdpRxMessage {
+    SetConfig(Config),
     ReplaceInterconnect(Interconnect),
 
     Poison,

src/driver/tasks/mixer.rs

@@ -1,4 +1,4 @@
-use super::{error::Result, message::*};
+use super::{error::Result, message::*, Config};
 use crate::{
     constants::*,
     tracks::{PlayMode, Track},
@@ -13,7 +13,6 @@ use audiopus::{
 use discortp::{
     rtp::{MutableRtpPacket, RtpPacket},
     MutablePacket,
-    Packet,
 };
 use flume::{Receiver, Sender, TryRecvError};
 use rand::random;
@@ -21,11 +20,12 @@ use spin_sleep::SpinSleeper;
 use std::time::Instant;
 use tokio::runtime::Handle;
 use tracing::{error, instrument};
-use xsalsa20poly1305::{aead::AeadInPlace, Nonce, TAG_SIZE};
+use xsalsa20poly1305::TAG_SIZE;
 
 struct Mixer {
     async_handle: Handle,
     bitrate: Bitrate,
+    config: Config,
     conn_active: Option<MixerConnection>,
     deadline: Instant,
     encoder: OpusEncoder,
@@ -53,6 +53,7 @@ impl Mixer {
         mix_rx: Receiver<MixerMessage>,
         async_handle: Handle,
         interconnect: Interconnect,
+        config: Config,
     ) -> Self {
         let bitrate = DEFAULT_BITRATE;
         let encoder = new_encoder(bitrate)
@@ -70,9 +71,12 @@ impl Mixer {
         rtp.set_sequence(random::<u16>().into());
         rtp.set_timestamp(random::<u32>().into());
 
+        let tracks = Vec::with_capacity(1.max(config.preallocated_tracks));
+
         Self {
             async_handle,
             bitrate,
+            config,
             conn_active: None,
             deadline: Instant::now(),
             encoder,
@@ -84,7 +88,7 @@ impl Mixer {
             silence_frames: 0,
             sleeper: Default::default(),
             soft_clip,
-            tracks: vec![],
+            tracks,
             ws: None,
         }
     }
@@ -137,6 +141,8 @@ impl Mixer {
                                 (Blame: VOICE_PACKET_MAX?)",
                         );
                         rtp.set_ssrc(ssrc);
+                        rtp.set_sequence(random::<u16>().into());
+                        rtp.set_timestamp(random::<u32>().into());
                         self.deadline = Instant::now();
                         Ok(())
                     },
@@ -160,6 +166,23 @@ impl Mixer {
 
                         self.rebuild_tracks()
                     },
+                    Ok(SetConfig(new_config)) => {
+                        self.config = new_config.clone();
+
+                        if self.tracks.capacity() < self.config.preallocated_tracks {
+                            self.tracks
+                                .reserve(self.config.preallocated_tracks - self.tracks.len());
+                        }
+
+                        if let Some(conn) = &self.conn_active {
+                            conn_failure |= conn
+                                .udp_rx
+                                .send(UdpRxMessage::SetConfig(new_config))
+                                .is_err();
+                        }
+
+                        Ok(())
+                    },
                     Ok(RebuildEncoder) => match new_encoder(self.bitrate) {
                         Ok(encoder) => {
                             self.encoder = encoder;
@@ -449,38 +472,38 @@ impl Mixer {
             .as_mut()
             .expect("Shouldn't be mixing packets without access to a cipher + UDP dest.");
 
-        let mut nonce = Nonce::default();
         let index = {
             let mut rtp = MutableRtpPacket::new(&mut self.packet[..]).expect(
                 "FATAL: Too few bytes in self.packet for RTP header.\
                     (Blame: VOICE_PACKET_MAX?)",
             );
 
-            let pkt = rtp.packet();
-            let rtp_len = RtpPacket::minimum_packet_size();
-            nonce[..rtp_len].copy_from_slice(&pkt[..rtp_len]);
-
             let payload = rtp.payload_mut();
+            let crypto_mode = conn.crypto_state.kind();
 
             let payload_len = if opus_frame.is_empty() {
-                self.encoder
+                let total_payload_space = payload.len() - crypto_mode.payload_suffix_len();
-                    .encode_float(&buffer[..STEREO_FRAME_SIZE], &mut payload[TAG_SIZE..])?
+                self.encoder.encode_float(
+                    &buffer[..STEREO_FRAME_SIZE],
+                    &mut payload[TAG_SIZE..total_payload_space],
+                )?
             } else {
                 let len = opus_frame.len();
                 payload[TAG_SIZE..TAG_SIZE + len].clone_from_slice(opus_frame);
                 len
             };
 
-            let final_payload_size = TAG_SIZE + payload_len;
+            let final_payload_size = conn
+                .crypto_state
+                .write_packet_nonce(&mut rtp, TAG_SIZE + payload_len);
 
-            let tag = conn.cipher.encrypt_in_place_detached(
+            conn.crypto_state.kind().encrypt_in_place(
-                &nonce,
+                &mut rtp,
-                b"",
+                &conn.cipher,
-                &mut payload[TAG_SIZE..final_payload_size],
+                final_payload_size,
             )?;
-            payload[..TAG_SIZE].copy_from_slice(&tag[..]);
 
-            rtp_len + final_payload_size
+            RtpPacket::minimum_packet_size() + final_payload_size
         };
 
         // TODO: This is dog slow, don't do this.
@@ -509,8 +532,9 @@ pub(crate) fn runner(
     interconnect: Interconnect,
     mix_rx: Receiver<MixerMessage>,
     async_handle: Handle,
+    config: Config,
 ) {
-    let mut mixer = Mixer::new(mix_rx, async_handle, interconnect);
+    let mut mixer = Mixer::new(mix_rx, async_handle, interconnect, config);
 
     mixer.run();
 }

src/driver/tasks/mod.rs

@@ -23,7 +23,7 @@ pub(crate) fn start(config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMe
     });
 }
 
-fn start_internals(core: Sender<CoreMessage>) -> Interconnect {
+fn start_internals(core: Sender<CoreMessage>, config: Config) -> Interconnect {
     let (evt_tx, evt_rx) = flume::unbounded();
     let (mix_tx, mix_rx) = flume::unbounded();
 
@@ -44,7 +44,7 @@ fn start_internals(core: Sender<CoreMessage>) -> Interconnect {
     let handle = Handle::current();
     std::thread::spawn(move || {
         info!("Mixer started.");
-        mixer::runner(ic, mix_rx, handle);
+        mixer::runner(ic, mix_rx, handle, config);
         info!("Mixer finished.");
     });
 
@@ -52,13 +52,23 @@ fn start_internals(core: Sender<CoreMessage>) -> Interconnect {
 }
 
 #[instrument(skip(rx, tx))]
-async fn runner(config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMessage>) {
+async fn runner(mut config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMessage>) {
+    let mut next_config: Option<Config> = None;
     let mut connection = None;
-    let mut interconnect = start_internals(tx);
+    let mut interconnect = start_internals(tx, config.clone());
 
     loop {
         match rx.recv_async().await {
             Ok(CoreMessage::ConnectWithResult(info, tx)) => {
+                config = if let Some(new_config) = next_config.take() {
+                    let _ = interconnect
+                        .mixer
+                        .send(MixerMessage::SetConfig(new_config.clone()));
+                    new_config
+                } else {
+                    config
+                };
+
                 connection = match Connection::new(info, &interconnect, &config).await {
                     Ok(connection) => {
                         // Other side may not be listening: this is fine.
@@ -87,6 +97,13 @@ async fn runner(config: Config, rx: Receiver<CoreMessage>, tx: Sender<CoreMessag
             Ok(CoreMessage::SetBitrate(b)) => {
                 let _ = interconnect.mixer.send(MixerMessage::SetBitrate(b));
             },
+            Ok(CoreMessage::SetConfig(mut new_config)) => {
+                next_config = Some(new_config.clone());
+
+                new_config.make_safe(&config, connection.is_some());
+
+                let _ = interconnect.mixer.send(MixerMessage::SetConfig(new_config));
+            },
             Ok(CoreMessage::AddEvent(evt)) => {
                 let _ = interconnect.events.send(EventMessage::AddGlobalEvent(evt));
             },

src/driver/tasks/udp_rx.rs

@@ -2,13 +2,16 @@ use super::{
     error::{Error, Result},
     message::*,
 };
-use crate::{constants::*, driver::CryptoMode, events::CoreContext};
+use crate::{
+    constants::*,
+    driver::{Config, DecodeMode},
+    events::CoreContext,
+};
 use audiopus::{coder::Decoder as OpusDecoder, Channels};
 use discortp::{
     demux::{self, DemuxedMut},
     rtp::{RtpExtensionPacket, RtpPacket},
     FromPacket,
-    MutablePacket,
     Packet,
     PacketSize,
 };
@@ -16,7 +19,7 @@ use flume::Receiver;
 use std::collections::HashMap;
 use tokio::net::udp::RecvHalf;
 use tracing::{error, info, instrument, warn};
-use xsalsa20poly1305::{aead::AeadInPlace, Nonce, Tag, XSalsa20Poly1305 as Cipher, TAG_SIZE};
+use xsalsa20poly1305::XSalsa20Poly1305 as Cipher;
 
 #[derive(Debug)]
 struct SsrcState {
@@ -46,19 +49,38 @@ impl SsrcState {
         &mut self,
         pkt: RtpPacket<'_>,
         data_offset: usize,
-    ) -> Result<(SpeakingDelta, Vec<i16>)> {
+        data_trailer: usize,
+        decode_mode: DecodeMode,
+        decrypted: bool,
+    ) -> Result<(SpeakingDelta, Option<Vec<i16>>)> {
         let new_seq: u16 = pkt.get_sequence().into();
+        let payload_len = pkt.payload().len();
 
         let extensions = pkt.get_extension() != 0;
         let seq_delta = new_seq.wrapping_sub(self.last_seq);
         Ok(if seq_delta >= (1 << 15) {
             // Overflow, reordered (previously missing) packet.
-            (SpeakingDelta::Same, vec![])
+            (SpeakingDelta::Same, Some(vec![]))
         } else {
             self.last_seq = new_seq;
             let missed_packets = seq_delta.saturating_sub(1);
-            let (audio, pkt_size) =
+
-                self.scan_and_decode(&pkt.payload()[data_offset..], extensions, missed_packets)?;
+            // Note: we still need to handle this for non-decoded.
+            // This is mainly because packet events and speaking events can be handed to the
+            // user.
+            let (audio, pkt_size) = if decode_mode.should_decrypt() && decrypted {
+                self.scan_and_decode(
+                    &pkt.payload()[data_offset..payload_len - data_trailer],
+                    extensions,
+                    missed_packets,
+                    decode_mode == DecodeMode::Decode,
+                )?
+            } else {
+                // The latter part is an upper bound, as we cannot determine
+                // how long packet extensions are.
+                // WIthout decryption, speaking detection is thus broken.
+                (None, payload_len - data_offset - data_trailer)
+            };
 
             let delta = if pkt_size == SILENT_FRAME.len() {
                 // Frame is silent.
@@ -91,8 +113,8 @@ impl SsrcState {
         data: &[u8],
         extension: bool,
         missed_packets: u16,
-    ) -> Result<(Vec<i16>, usize)> {
+        decode: bool,
-        let mut out = vec![0; STEREO_FRAME_SIZE];
+    ) -> Result<(Option<Vec<i16>>, usize)> {
         let start = if extension {
             RtpExtensionPacket::new(data)
                 .map(|pkt| pkt.packet_size())
@@ -104,6 +126,9 @@ impl SsrcState {
             Ok(0)
         }?;
 
+        let pkt = if decode {
+            let mut out = vec![0; STEREO_FRAME_SIZE];
+
             for _ in 0..missed_packets {
                 let missing_frame: Option<&[u8]> = None;
                 if let Err(e) = self.decoder.decode(missing_frame, &mut out[..], false) {
@@ -123,7 +148,12 @@ impl SsrcState {
             // => multiply by number of channels.
             out.truncate(2 * audio_len);
 
-        Ok((out, data.len() - start))
+            Some(out)
+        } else {
+            None
+        };
+
+        Ok((pkt, data.len() - start))
     }
 }
 
@@ -131,7 +161,7 @@ struct UdpRx {
     cipher: Cipher,
     decoder_map: HashMap<u32, SsrcState>,
     #[allow(dead_code)]
-    mode: CryptoMode, // In future, this will allow crypto mode selection.
+    config: Config,
     packet_buffer: [u8; VOICE_PACKET_MAX],
     rx: Receiver<UdpRxMessage>,
     udp_socket: RecvHalf,
@@ -150,7 +180,10 @@ impl UdpRx {
                     match msg {
                         Ok(ReplaceInterconnect(i)) => {
                             *interconnect = i;
-                        }
+                        },
+                        Ok(SetConfig(c)) => {
+                            self.config = c;
+                        },
                         Ok(Poison) | Err(_) => break,
                     }
                 }
@@ -166,6 +199,7 @@ impl UdpRx {
         // For simplicity, we nominate the mixing context to rebuild the event
         // context if it fails (hence, the `let _ =` statements.), as it will try to
         // make contact every 20ms.
+        let crypto_mode = self.config.crypto_mode;
         let packet = &mut self.packet_buffer[..len];
 
         match demux::demux_mut(packet) {
@@ -175,15 +209,40 @@ impl UdpRx {
                     return;
                 }
 
-                let rtp_body_start =
+                let packet_data = if self.config.decode_mode.should_decrypt() {
-                    decrypt_in_place(&mut rtp, &self.cipher).expect("RTP decryption failed.");
+                    let out = crypto_mode
+                        .decrypt_in_place(&mut rtp, &self.cipher)
+                        .map(|(s, t)| (s, t, true));
+
+                    if let Err(e) = out {
+                        warn!("RTP decryption failed: {:?}", e);
+                    }
+
+                    out.ok()
+                } else {
+                    None
+                };
+
+                let (rtp_body_start, rtp_body_tail, decrypted) = packet_data.unwrap_or_else(|| {
+                    (
+                        crypto_mode.payload_prefix_len(),
+                        crypto_mode.payload_suffix_len(),
+                        false,
+                    )
+                });
 
                 let entry = self
                     .decoder_map
                     .entry(rtp.get_ssrc())
                     .or_insert_with(|| SsrcState::new(rtp.to_immutable()));
 
-                if let Ok((delta, audio)) = entry.process(rtp.to_immutable(), rtp_body_start) {
+                if let Ok((delta, audio)) = entry.process(
+                    rtp.to_immutable(),
+                    rtp_body_start,
+                    rtp_body_tail,
+                    self.config.decode_mode,
+                    decrypted,
+                ) {
                     match delta {
                         SpeakingDelta::Start => {
                             let _ = interconnect.events.send(EventMessage::FireCoreEvent(
@@ -209,25 +268,40 @@ impl UdpRx {
                             audio,
                             packet: rtp.from_packet(),
                             payload_offset: rtp_body_start,
+                            payload_end_pad: rtp_body_tail,
                         },
                     ));
                 } else {
-                    warn!("RTP decoding/decrytion failed.");
+                    warn!("RTP decoding/processing failed.");
                 }
             },
             DemuxedMut::Rtcp(mut rtcp) => {
-                let rtcp_body_start = decrypt_in_place(&mut rtcp, &self.cipher);
+                let packet_data = if self.config.decode_mode.should_decrypt() {
+                    let out = crypto_mode.decrypt_in_place(&mut rtcp, &self.cipher);
+
+                    if let Err(e) = out {
+                        warn!("RTCP decryption failed: {:?}", e);
+                    }
+
+                    out.ok()
+                } else {
+                    None
+                };
+
+                let (start, tail) = packet_data.unwrap_or_else(|| {
+                    (
+                        crypto_mode.payload_prefix_len(),
+                        crypto_mode.payload_suffix_len(),
+                    )
+                });
 
-                if let Ok(start) = rtcp_body_start {
                 let _ = interconnect.events.send(EventMessage::FireCoreEvent(
                     CoreContext::RtcpPacket {
                         packet: rtcp.from_packet(),
                         payload_offset: start,
+                        payload_end_pad: tail,
                     },
                 ));
-                } else {
-                    warn!("RTCP decryption failed.");
-                }
             },
             DemuxedMut::FailedParse(t) => {
                 warn!("Failed to parse message of type {:?}.", t);
@@ -244,7 +318,7 @@ pub(crate) async fn runner(
     mut interconnect: Interconnect,
     rx: Receiver<UdpRxMessage>,
     cipher: Cipher,
-    mode: CryptoMode,
+    config: Config,
     udp_socket: RecvHalf,
 ) {
     info!("UDP receive handle started.");
@@ -252,7 +326,7 @@ pub(crate) async fn runner(
     let mut state = UdpRx {
         cipher,
         decoder_map: Default::default(),
-        mode,
+        config,
         packet_buffer: [0u8; VOICE_PACKET_MAX],
         rx,
         udp_socket,
@@ -263,23 +337,6 @@ pub(crate) async fn runner(
     info!("UDP receive handle stopped.");
 }
 
-#[inline]
-fn decrypt_in_place(packet: &mut impl MutablePacket, cipher: &Cipher) -> Result<usize> {
-    // Applies discord's cheapest.
-    // In future, might want to make a choice...
-    let header_len = packet.packet().len() - packet.payload().len();
-    let mut nonce = Nonce::default();
-    nonce[..header_len].copy_from_slice(&packet.packet()[..header_len]);
-
-    let data = packet.payload_mut();
-    let (tag_bytes, data_bytes) = data.split_at_mut(TAG_SIZE);
-    let tag = Tag::from_slice(tag_bytes);
-
-    Ok(cipher
-        .decrypt_in_place_detached(&nonce, b"", data_bytes, tag)
-        .map(|_| TAG_SIZE)?)
-}
-
 #[inline]
 fn rtp_valid(packet: RtpPacket<'_>) -> bool {
     packet.get_version() == RTP_VERSION && packet.get_payload_type() == RTP_PROFILE_TYPE

src/events/context.rs

@@ -42,13 +42,15 @@ pub enum EventContext<'a> {
     /// if `audio.len() == 0`, then this packet arrived out-of-order.
     VoicePacket {
         /// Decoded audio from this packet.
-        audio: &'a Vec<i16>,
+        audio: &'a Option<Vec<i16>>,
         /// Raw RTP packet data.
         ///
         /// Includes the SSRC (i.e., sender) of this packet.
         packet: &'a Rtp,
-        /// Byte index into the packet for where the payload begins.
+        /// Byte index into the packet body (after headers) for where the payload begins.
         payload_offset: usize,
+        /// Number of bytes at the end of the packet to discard.
+        payload_end_pad: usize,
     },
     /// Telemetry/statistics packet, received from another stream (detailed in `packet`).
     /// `payload_offset` contains the true payload location within the raw packet's `payload()`,
@@ -56,8 +58,10 @@ pub enum EventContext<'a> {
     RtcpPacket {
         /// Raw RTCP packet data.
         packet: &'a Rtcp,
-        /// Byte index into the packet for where the payload begins.
+        /// Byte index into the packet body (after headers) for where the payload begins.
         payload_offset: usize,
+        /// Number of bytes at the end of the packet to discard.
+        payload_end_pad: usize,
     },
     /// Fired whenever a client connects to a call for the first time, allowing SSRC/UserID
     /// matching.
@@ -74,13 +78,15 @@ pub(crate) enum CoreContext {
         speaking: bool,
     },
     VoicePacket {
-        audio: Vec<i16>,
+        audio: Option<Vec<i16>>,
         packet: Rtp,
         payload_offset: usize,
+        payload_end_pad: usize,
     },
     RtcpPacket {
         packet: Rtcp,
         payload_offset: usize,
+        payload_end_pad: usize,
     },
     ClientConnect(ClientConnect),
     ClientDisconnect(ClientDisconnect),
@@ -100,17 +106,21 @@ impl<'a> CoreContext {
                 audio,
                 packet,
                 payload_offset,
+                payload_end_pad,
             } => EventContext::VoicePacket {
                 audio,
                 packet,
                 payload_offset: *payload_offset,
+                payload_end_pad: *payload_end_pad,
             },
             RtcpPacket {
                 packet,
                 payload_offset,
+                payload_end_pad,
             } => EventContext::RtcpPacket {
                 packet,
                 payload_offset: *payload_offset,
+                payload_end_pad: *payload_end_pad,
             },
             ClientConnect(evt) => EventContext::ClientConnect(*evt),
             ClientDisconnect(evt) => EventContext::ClientDisconnect(*evt),

src/handler.rs

@@ -1,5 +1,8 @@
 #[cfg(feature = "driver")]
-use crate::{driver::Driver, error::ConnectionResult};
+use crate::{
+    driver::{Config, Driver},
+    error::ConnectionResult,
+};
 use crate::{
     error::{JoinError, JoinResult},
     id::{ChannelId, GuildId, UserId},
@@ -59,6 +62,19 @@ impl Call {
         Self::new_raw(guild_id, Some(ws), user_id)
     }
 
+    #[cfg(feature = "driver")]
+    /// Creates a new Call, configuring the driver as specified.
+    #[inline]
+    #[instrument]
+    pub fn from_driver_config(
+        guild_id: GuildId,
+        ws: Shard,
+        user_id: UserId,
+        config: Config,
+    ) -> Self {
+        Self::new_raw_cfg(guild_id, Some(ws), user_id, config)
+    }
+
     /// Creates a new, standalone Call which is not connected via
     /// WebSocket to the Gateway.
     ///
@@ -73,6 +89,18 @@ impl Call {
         Self::new_raw(guild_id, None, user_id)
     }
 
+    #[cfg(feature = "driver")]
+    /// Creates a new standalone Call, configuring the driver as specified.
+    #[inline]
+    #[instrument]
+    pub fn standalone_from_driver_config(
+        guild_id: GuildId,
+        user_id: UserId,
+        config: Config,
+    ) -> Self {
+        Self::new_raw_cfg(guild_id, None, user_id, config)
+    }
+
     fn new_raw(guild_id: GuildId, ws: Option<Shard>, user_id: UserId) -> Self {
         Call {
             connection: None,
@@ -86,6 +114,19 @@ impl Call {
         }
     }
 
+    #[cfg(feature = "driver")]
+    fn new_raw_cfg(guild_id: GuildId, ws: Option<Shard>, user_id: UserId, config: Config) -> Self {
+        Call {
+            connection: None,
+            driver: Driver::new(config),
+            guild_id,
+            self_deaf: false,
+            self_mute: false,
+            user_id,
+            ws,
+        }
+    }
+
     #[instrument(skip(self))]
     fn do_connect(&mut self) {
         match &self.connection {

src/manager.rs

@@ -1,5 +1,5 @@
 #[cfg(feature = "driver")]
-use crate::error::ConnectionResult;
+use crate::{driver::Config, error::ConnectionResult};
 use crate::{
     error::{JoinError, JoinResult},
     id::{ChannelId, GuildId, UserId},
@@ -47,6 +47,9 @@ pub struct Songbird {
     client_data: PRwLock<ClientData>,
     calls: PRwLock<HashMap<GuildId, Arc<Mutex<Call>>>>,
     sharder: Sharder,
+
+    #[cfg(feature = "driver")]
+    driver_config: PRwLock<Option<Config>>,
 }
 
 impl Songbird {
@@ -61,6 +64,9 @@ impl Songbird {
             client_data: Default::default(),
             calls: Default::default(),
             sharder: Sharder::Serenity(Default::default()),
+
+            #[cfg(feature = "driver")]
+            driver_config: Default::default(),
         })
     }
 
@@ -84,6 +90,9 @@ impl Songbird {
             }),
             calls: Default::default(),
             sharder: Sharder::Twilight(cluster),
+
+            #[cfg(feature = "driver")]
+            driver_config: Default::default(),
         })
     }
 
@@ -133,7 +142,18 @@ impl Songbird {
                         .get_shard(shard)
                         .expect("Failed to get shard handle: shard_count incorrect?");
 
-                    Arc::new(Mutex::new(Call::new(guild_id, shard_handle, info.user_id)))
+                    #[cfg(feature = "driver")]
+                    let call = Call::from_driver_config(
+                        guild_id,
+                        shard_handle,
+                        info.user_id,
+                        self.driver_config.read().clone().unwrap_or_default(),
+                    );
+
+                    #[cfg(not(feature = "driver"))]
+                    let call = Call::new(guild_id, shard_handle, info.user_id);
+
+                    Arc::new(Mutex::new(call))
                 })
                 .clone()
         })
@@ -347,6 +367,20 @@ impl VoiceGatewayManager for Songbird {
     }
 }
 
+#[cfg(feature = "driver")]
+impl Songbird {
+    /// Sets a shared configuration for all drivers created from this
+    /// manager.
+    ///
+    /// Changes made here will apply to new Call and Driver instances only.
+    ///
+    /// Requires the `"driver"` feature.
+    pub fn set_config(&self, new_config: Config) {
+        let mut config = self.driver_config.write();
+        *config = Some(new_config);
+    }
+}
+
 #[inline]
 fn shard_id(guild_id: u64, shard_count: u64) -> u64 {
     (guild_id >> 22) % shard_count