fix(metrics): fix metrics

readme.hints.md

@@ -2,6 +2,27 @@
 
 ## Byte Tracking and Metrics
 
+### What Gets Counted (Network Interface Throughput)
+
+The byte tracking is designed to match network interface throughput (what Unifi/network monitoring tools show):
+
+**Counted bytes include:**
+- All application data
+- TLS handshakes and protocol overhead
+- TLS record headers and encryption padding
+- HTTP headers and protocol data
+- WebSocket frames and protocol overhead
+- TLS alerts sent to clients
+
+**NOT counted:**
+- PROXY protocol headers (sent to backend, not client)
+- TCP/IP headers (handled by OS, not visible at application layer)
+
+**Byte direction:**
+- `bytesReceived`: All bytes received FROM the client on the incoming connection
+- `bytesSent`: All bytes sent TO the client on the incoming connection
+- Backend connections are separate and not mixed with client metrics
+
 ### Double Counting Issue (Fixed)
 
 **Problem**: Initial data chunks were being counted twice in the byte tracking:
@@ -25,6 +46,51 @@ The metrics system has three layers:
 
 Total byte counts come from connection records only, preventing double counting.
 
+### Understanding "High" Byte Counts
+
+If byte counts seem high compared to actual application data, remember:
+- TLS handshakes can be 1-5KB depending on cipher suites and certificates
+- Each TLS record has 5 bytes of header overhead
+- TLS encryption adds 16-48 bytes of padding/MAC per record
+- HTTP/2 has additional framing overhead
+- WebSocket has frame headers (2-14 bytes per message)
+
+This overhead is real network traffic and should be counted for accurate throughput metrics.
+
+### Byte Counting Paths
+
+There are two mutually exclusive paths for connections:
+
+1. **Direct forwarding** (route-connection-handler.ts):
+   - Used for TCP passthrough, TLS passthrough, and direct connections
+   - Bytes counted in `setupBidirectionalForwarding` callbacks
+   - Initial chunk NOT counted separately (flows through bidirectional forwarding)
+
+2. **HttpProxy forwarding** (http-proxy-bridge.ts):
+   - Used for TLS termination (terminate, terminate-and-reencrypt)
+   - Initial chunk counted when written to proxy
+   - All subsequent bytes counted in `setupBidirectionalForwarding` callbacks
+   - This is the ONLY counting point for these connections
+
+### Byte Counting Audit (2025-01-06)
+
+A comprehensive audit was performed to verify byte counting accuracy:
+
+**Audit Results:**
+- ✅ No double counting detected in any connection flow
+- ✅ Each byte counted exactly once in each direction
+- ✅ Connection records and metrics updated consistently
+- ✅ PROXY protocol headers correctly excluded from client metrics
+- ✅ NFTables forwarded connections correctly not counted (kernel handles)
+
+**Key Implementation Points:**
+- All byte counting happens in only 2 files: `route-connection-handler.ts` and `http-proxy-bridge.ts`
+- Both use the same pattern: increment `record.bytesReceived/Sent` AND call `metricsCollector.recordBytes()`
+- Initial chunks handled correctly: stored but not counted until forwarded
+- TLS alerts counted as sent bytes (correct - they are sent to client)
+
+For full audit details, see `readme.byte-counting-audit.md`
+
 ## Connection Cleanup
 
 ### Zombie Connection Detection