Ip packet differences in wireshark and pingo. Difference in datagram …

…lengths.

cmd/pingo/main.go

@@ -1,40 +1,33 @@
 package main
 
 import (
+	"encoding/hex"
 	"fmt"
-	"log"
 	"syscall"
 
 	"github.com/code-brew-lab/pingo/internal/ip"
+	"github.com/code-brew-lab/pingo/internal/netcore"
 )
 
 func main() {
-	h, err := ip.NewHeaderBuilder().Build()
-	if err != nil {
-		log.Fatalln(err)
-	}
-
-	req := h.Marshal()
-
-	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_IP)
+	fd, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_ICMP)
 	if err != nil {
 		fmt.Println(err)
 		return
 	}
 
-	syscall.Sendto(fd, req, 0, &syscall.SockaddrInet4{
-		Port: 0,
-		Addr: [4]byte{127, 0, 0, 1},
-	})
-
 	for {
 		buf := make([]byte, 1024)
 		numRead, err := syscall.Read(fd, buf)
 		if err != nil {
 			fmt.Println(err)
 		}
 
-		header, i, err := ip.ParseHeader(buf[:numRead])
+		packet := netcore.NewPacket(buf[:numRead])
+
+		fmt.Printf("Raw Packet: %s\n", hex.EncodeToString(packet.Raw()))
+
+		header, i, err := ip.ParseHeader(packet.Raw())
 		if err != nil {
 			fmt.Println(err)
 			continue
@@ -43,3 +36,17 @@ func main() {
 		fmt.Println(i)
 	}
 }
+
+/*
+	Wireshark:
+		Packet_1 [RESP]: 45000054000000003801c12cd8ef2678c0a8016d0000f2c767470000668bcac80001899808090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637
+
+		Packet_2 [RESP]: 45000054000000003801c12cd8ef2678c0a8016d0000dffa67470001668bcac900019c6308090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637
+*/
+
+/*
+	Pingo:
+		Packet_1 [RESP]:	45004000000000003801c12cd8ef2678c0a8016d0000f2c767470000668bcac80001899808090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637
+
+		Packet_2 [RESP]: 45004000000000003801c12cd8ef2678c0a8016d0000dffa67470001668bcac900019c6308090a0b0c0d0e0f101112131415161718191a1b1c1d1e1f202122232425262728292a2b2c2d2e2f3031323334353637
+*/

internal/ip/header.go

@@ -2,11 +2,10 @@ package ip
 
 import (
 	"encoding/binary"
-	"encoding/hex"
 	"errors"
 	"fmt"
 
-	"github.com/code-brew-lab/pingo/internal/checksum"
+	"github.com/code-brew-lab/pingo/internal/netcore/checksum"
 )
 
 type (
@@ -46,8 +45,8 @@ func ParseHeader(h []byte) (*Header, int, error) {
 	}
 
 	headerLen := h[0] & 0x0F
-	fmt.Println(hex.EncodeToString(h[:headerLen*headerMultiplier]))
-	if !checksum.Verify(h[:headerLen*headerMultiplier]) {
+	totalLen := headerLen * headerMultiplier
+	if !checksum.Verify(h[:totalLen]) {
 		return nil, 0, errors.New("ip.ParseHeader: Checksum verification failed")
 	}
 
@@ -70,9 +69,9 @@ func ParseHeader(h []byte) (*Header, int, error) {
 	copy(dstIP, h[16:20])
 
 	var options []byte
-	if headerLen > 5 {
+	if totalLen > minHeaderLen {
 		options = make([]byte, (headerLen-5)*headerMultiplier)
-		copy(options, h[20:headerLen*headerMultiplier])
+		copy(options, h[minHeaderLen:totalLen])
 	}
 
 	return &Header{
@@ -180,6 +179,3 @@ func (h *Header) Marshal() []byte {
 
 	return buff
 }
-
-// Wireshark => Req: 45000054df2100004001da0ac0a8016dd8ef2678,  Resp: 45000054000000003801c12cd8ef2678c0a8016d
-// Pingo     => 45004000000000003801c12cd8ef2678c0a8016d

internal/checksum/chechsum_test.go → internal/netcore/checksum/chechsum_test.go

@@ -25,6 +25,14 @@ var (
 			input:    []byte{0x45, 0x00, 0x00, 0x28, 0x04, 0x59, 0x00, 0x00, 0x40, 0x06, 0x00, 0x00, 0xc0, 0xa8, 0x01, 0x6d, 0x0d, 0x45, 0x44, 0x40},
 			expected: 25309,
 		},
+		{
+			input:    []byte{0x45, 0x00, 0x05, 0x58, 0xe8, 0x82, 0x00, 0x00, 0x40, 0x01, 0x00, 0x00, 0xc0, 0xa8, 0x01, 0x6d, 0xc0, 0xa8, 0x01, 0x01},
+			expected: 2404,
+		},
+		{
+			input:    []byte{0x45, 0x00, 0x00, 0x54, 0xca, 0xf3, 0x00, 0x00, 0x38, 0x01, 0x08, 0xab, 0x68, 0x10, 0x00, 0x00, 0xc0, 0xa8, 0x01, 0x6d},
+			expected: 34021,
+		},
 	}
 
 	verifyCases = []VerifyTestCase{
@@ -40,6 +48,22 @@ var (
 			input:   []byte{0x45, 0x00, 0x05, 0x58, 0x4e, 0xa0, 0x00, 0x00, 0x40, 0x01, 0x43, 0x2a, 0xc0, 0xa8, 0x01, 0x6d, 0x11, 0xfd, 0x0f, 0xc9},
 			isValid: true,
 		},
+		{
+			input:   []byte{0x45, 0x00, 0x05, 0x58, 0xe8, 0x82, 0x00, 0x00, 0x40, 0x01, 0x09, 0x64, 0xc0, 0xa8, 0x01, 0x6d, 0xc0, 0xa8, 0x01, 0x01},
+			isValid: true,
+		},
+		{
+			input:   []byte{0x45, 0x00, 0x00, 0x54, 0xca, 0xf3, 0x00, 0x00, 0x38, 0x01, 0x08, 0xab, 0x68, 0x10, 0x84, 0xe5, 0xc0, 0xa8, 0x01, 0x6d},
+			isValid: true,
+		},
+		{
+			input:   []byte{0x45, 0xdf, 0x05, 0x58, 0x4e, 0xa0, 0x00, 0x00, 0x40, 0x01, 0x43, 0x2a, 0xc0, 0xa8, 0x01, 0x6d, 0x11, 0xfd, 0x0f, 0xc9},
+			isValid: false,
+		},
+		{
+			input:   []byte{0x45, 0x00, 0x00, 0x28, 0x04, 0x59, 0x00, 0x00, 0x40, 0x06, 0x60, 0xdd, 0xc0, 0xa8, 0x01, 0x6d, 0x0d, 0x45, 0x44, 0x40},
+			isValid: false,
+		},
 	}
 )
 

internal/netcore/packet.go

@@ -0,0 +1,25 @@
+package netcore
+
+import (
+	"time"
+)
+
+type Packet struct {
+	timestamp time.Time
+	raw       []byte
+}
+
+func NewPacket(raw []byte) *Packet {
+	return &Packet{
+		timestamp: time.Now(),
+		raw:       raw,
+	}
+}
+
+func (p *Packet) Timestamp() time.Time {
+	return p.timestamp
+}
+
+func (p *Packet) Raw() []byte {
+	return p.raw
+}