Method backendToClient

internal/handler/forwarder.go:129–178

backendToClient reads packets from backend and sends to client. Uses buffer pool to avoid per-session 64KB allocations.

(ctx *Context, session *Session)

// backendToClient reads packets from backend and sends to client.
// Uses buffer pool to avoid per-session 64KB allocations.
func (h *ForwarderHandler) backendToClient(ctx *Context, session *Session) {
	for {
		// Check if session is closed before reading
		if session.IsClosed() {
			return
		}

		// Get buffer from pool for this read
		buf := GetBuffer()

		// Set read deadline to detect idle connections
		session.BackendConn.SetReadDeadline(time.Now().Add(5 * time.Minute))

		n, err := session.BackendConn.Read(*buf)
		if err != nil {
			// Connection closed or timed out
			PutBuffer(buf)
			return
		}

		// Check again after read (session may have closed during blocking read)
		if session.IsClosed() {
			PutBuffer(buf)
			return
		}

		// Update activity timestamp (bidirectional tracking)
		session.Touch()

		// Notify proxy of server packets to learn server's SCID(s)
		// This enables routing subsequent client packets that use server's CID as DCID
		ctx.NotifyServerPacket((*buf)[:n])

		debug.Printf(" backend->client: %d bytes, first byte: 0x%02x", n, (*buf)[0])

		// Send to client via proxy's UDP connection
		if ctx.ProxyConn != nil {
			_, err = ctx.ProxyConn.WriteToUDP((*buf)[:n], session.ClientAddr())
			if err != nil {
				log.Printf("[forwarder] write to client failed: %v", err)
				PutBuffer(buf)
				return
			}
			debug.Printf(" sent to client %s", session.ClientAddr())
		}

		// Return buffer to pool after use
		PutBuffer(buf)
	}
}