transport: promote FMP stream framing to transport::framing

The FMP frame-boundary reader lived in transport/tcp/stream.rs, but the
Tor and Nym transports both reached across module boundaries to
'use crate::transport::tcp::stream::read_fmp_packet', a layering smell:
the reader is a shared stream-framing utility, not a TCP-private one.
Move the file to transport/framing.rs and repoint the tcp/tor/nym use
sites, removing the tor->tcp and nym->tcp dependencies. Behavior
unchanged.

src/transport/framing.rs

@@ -3,8 +3,8 @@
 //! Recovers FIPS packet boundaries from a TCP byte stream using the
 //! existing 4-byte FMP common prefix `[ver+phase:1][flags:1][payload_len:2 LE]`.
 //!
-//! This module is deliberately separate from the TCP transport so it can
-//! be reused by the future Tor transport.
+//! This module is deliberately separate from any single transport so it can
+//! be shared by the stream-oriented transports (TCP, Tor, Nym).
 
 use tokio::io::{AsyncRead, AsyncReadExt};
 

src/transport/mod.rs

@@ -34,6 +34,8 @@ use tor::TorTransport;
 use tor::control::TorMonitoringInfo;
 use udp::UdpTransport;
 
+pub(crate) mod framing;
+
 mod stats_common;
 pub(crate) use stats_common::PoolCounters;
 

src/transport/nym/mod.rs

@@ -9,7 +9,7 @@
 //!
 //! Outbound-only: connects to remote TCP peers through the local
 //! nym-socks5-client SOCKS5 proxy. Like the Tor transport, reuses FMP
-//! stream framing from `tcp::stream` and follows the same connection
+//! stream framing from `transport::framing` and follows the same connection
 //! pool pattern. No inbound service is supported.
 
 pub mod stats;
@@ -22,7 +22,7 @@ use super::{
     TransportError, TransportId, TransportState, TransportType,
 };
 use crate::config::NymConfig;
-use crate::transport::tcp::stream::read_fmp_packet;
+use crate::transport::framing::read_fmp_packet;
 use stats::NymStats;
 
 use futures::FutureExt;

src/transport/tcp/mod.rs

@@ -23,7 +23,6 @@
 //! TCP stream and the receiver uses phase-dependent size computation.
 
 pub mod stats;
-pub mod stream;
 
 use super::resolve_socket_addr;
 use super::{
@@ -31,8 +30,8 @@ use super::{
     TransportError, TransportId, TransportState, TransportType,
 };
 use crate::config::TcpConfig;
+use crate::transport::framing::read_fmp_packet;
 use stats::TcpStats;
-use stream::read_fmp_packet;
 
 use futures::FutureExt;
 use socket2::TcpKeepalive;

src/transport/tor/mod.rs

@@ -14,8 +14,8 @@
 //! ## Architecture
 //!
 //! Like TCP, each peer has its own connection. The transport reuses FMP
-//! stream framing from `tcp::stream` and follows the same connection pool
-//! pattern as the TCP transport. Inbound connections arrive via a local
+//! stream framing from `transport::framing` and follows the same connection
+//! pool pattern as the TCP transport. Inbound connections arrive via a local
 //! TCP listener that the Tor daemon forwards onion service traffic to.
 
 pub mod control;
@@ -31,7 +31,7 @@ use super::{
     TransportError, TransportId, TransportState, TransportType,
 };
 use crate::config::TorConfig;
-use crate::transport::tcp::stream::read_fmp_packet;
+use crate::transport::framing::read_fmp_packet;
 use control::{ControlAuth, TorControlClient, TorMonitoringInfo};
 use stats::TorStats;