From a2c83c6040a6c26b9f005dc8e3cec46764956494 Mon Sep 17 00:00:00 2001
From: "M. Mert Yildiran" <mehmet@up9.com>
Date: Mon, 20 Jun 2022 14:13:45 +0300
Subject: [PATCH] Determine the endianness on runtime if it's possible in Go
 (default little-endian) #run_acceptance_tests

---
 tap/passive_tapper.go       | 25 +++++++++++++++++++++++--
 tap/tlstapper/bpf_logger.go |  4 ++--
 tap/tlstapper/tls_poller.go |  8 ++++----
 tap/tlstapper/tls_tapper.go |  9 +++++----
 4 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/tap/passive_tapper.go b/tap/passive_tapper.go
index b62ce3b40..24fed4ee0 100644
--- a/tap/passive_tapper.go
+++ b/tap/passive_tapper.go
@@ -9,6 +9,7 @@
 package tap
 
 import (
+	"encoding/binary"
 	"encoding/json"
 	"flag"
 	"fmt"
@@ -17,6 +18,7 @@ import (
 	"strconv"
 	"strings"
 	"time"
+	"unsafe"
 
 	"github.com/shirou/gopsutil/cpu"
 	"github.com/struCoder/pidusage"
@@ -298,8 +300,10 @@ func startTlsTapper(extension *api.Extension, outputItems chan *api.OutputChanne
 		OutputChannel: outputItems,
 	}
 
-	go tls.PollForLogging()
-	go tls.Poll(emitter, options, streamsMap)
+	byteOrder := getByteOrder()
+
+	go tls.PollForLogging(byteOrder)
+	go tls.Poll(byteOrder, emitter, options, streamsMap)
 
 	return &tls
 }
@@ -319,3 +323,20 @@ func buildIgnoredPortsList(ignoredPorts string) []uint16 {
 
 	return result
 }
+
+func getByteOrder() (byteOrder binary.ByteOrder) {
+	buf := [2]byte{}
+	*(*uint16)(unsafe.Pointer(&buf[0])) = uint16(0xABCD)
+
+	switch buf {
+	case [2]byte{0xCD, 0xAB}:
+		byteOrder = binary.LittleEndian
+	case [2]byte{0xAB, 0xCD}:
+		byteOrder = binary.BigEndian
+	default:
+		logger.Log.Warning("Could not determine native endianness. Defaulting to little-endian")
+		byteOrder = binary.LittleEndian
+	}
+
+	return
+}
diff --git a/tap/tlstapper/bpf_logger.go b/tap/tlstapper/bpf_logger.go
index 1cb1da48a..40b0dd94b 100644
--- a/tap/tlstapper/bpf_logger.go
+++ b/tap/tlstapper/bpf_logger.go
@@ -52,7 +52,7 @@ func (p *bpfLogger) close() error {
 	return p.logReader.Close()
 }
 
-func (p *bpfLogger) poll() {
+func (p *bpfLogger) poll(byteOrder binary.ByteOrder) {
 	logger.Log.Infof("Start polling for bpf logs")
 
 	for {
@@ -76,7 +76,7 @@ func (p *bpfLogger) poll() {
 
 		var log logMessage
 
-		if err := binary.Read(buffer, binary.LittleEndian, &log); err != nil {
+		if err := binary.Read(buffer, byteOrder, &log); err != nil {
 			LogError(errors.Errorf("Error parsing log %v", err))
 			continue
 		}
diff --git a/tap/tlstapper/tls_poller.go b/tap/tlstapper/tls_poller.go
index c0dddf9a4..9c450239a 100644
--- a/tap/tlstapper/tls_poller.go
+++ b/tap/tlstapper/tls_poller.go
@@ -75,11 +75,11 @@ func (p *tlsPoller) close() error {
 	return p.chunksReader.Close()
 }
 
-func (p *tlsPoller) poll(emitter api.Emitter, options *api.TrafficFilteringOptions, streamsMap api.TcpStreamMap) {
+func (p *tlsPoller) poll(byteOrder binary.ByteOrder, emitter api.Emitter, options *api.TrafficFilteringOptions, streamsMap api.TcpStreamMap) {
 	// tlsTapperTlsChunk is generated by bpf2go.
 	chunks := make(chan *tlsTapperTlsChunk)
 
-	go p.pollChunksPerfBuffer(chunks)
+	go p.pollChunksPerfBuffer(byteOrder, chunks)
 
 	for {
 		select {
@@ -97,7 +97,7 @@ func (p *tlsPoller) poll(emitter api.Emitter, options *api.TrafficFilteringOptio
 	}
 }
 
-func (p *tlsPoller) pollChunksPerfBuffer(chunks chan<- *tlsTapperTlsChunk) {
+func (p *tlsPoller) pollChunksPerfBuffer(byteOrder binary.ByteOrder, chunks chan<- *tlsTapperTlsChunk) {
 	logger.Log.Infof("Start polling for tls events")
 
 	for {
@@ -123,7 +123,7 @@ func (p *tlsPoller) pollChunksPerfBuffer(chunks chan<- *tlsTapperTlsChunk) {
 
 		var chunk tlsTapperTlsChunk
 
-		if err := binary.Read(buffer, binary.LittleEndian, &chunk); err != nil {
+		if err := binary.Read(buffer, byteOrder, &chunk); err != nil {
 			LogError(errors.Errorf("Error parsing chunk %v", err))
 			continue
 		}
diff --git a/tap/tlstapper/tls_tapper.go b/tap/tlstapper/tls_tapper.go
index 578e28f36..a311e1f68 100644
--- a/tap/tlstapper/tls_tapper.go
+++ b/tap/tlstapper/tls_tapper.go
@@ -1,6 +1,7 @@
 package tlstapper
 
 import (
+	"encoding/binary"
 	"strconv"
 	"sync"
 
@@ -58,12 +59,12 @@ func (t *TlsTapper) Init(chunksBufferSize int, logBufferSize int, procfs string,
 	return t.poller.init(&t.bpfObjects, chunksBufferSize)
 }
 
-func (t *TlsTapper) Poll(emitter api.Emitter, options *api.TrafficFilteringOptions, streamsMap api.TcpStreamMap) {
-	t.poller.poll(emitter, options, streamsMap)
+func (t *TlsTapper) Poll(byteOrder binary.ByteOrder, emitter api.Emitter, options *api.TrafficFilteringOptions, streamsMap api.TcpStreamMap) {
+	t.poller.poll(byteOrder, emitter, options, streamsMap)
 }
 
-func (t *TlsTapper) PollForLogging() {
-	t.bpfLogger.poll()
+func (t *TlsTapper) PollForLogging(byteOrder binary.ByteOrder) {
+	t.bpfLogger.poll(byteOrder)
 }
 
 func (t *TlsTapper) GlobalSsllibTap(sslLibrary string) error {