英文:
raw socket didn't receive icmp response
问题
我正在尝试发送一个TTL为1的ICMP消息,并期望接收到一个超时消息。我可以从Wireshark中看到该消息的到达,但我的程序在syscall.Recvfrom
上阻塞。有人知道为什么吗?
以下是你提供的代码的翻译:
package main
import (
"bytes"
"encoding/binary"
"fmt"
"net"
"os"
"syscall"
)
type ICMP struct {
Type uint8
Code uint8
Checksum uint16
Identifier uint16
SeqNo uint16
}
func Checksum(data []byte) uint16 {
var (
sum uint32
length int = len(data)
index int
)
for length > 1 {
sum += uint32(data[index])<<8 + uint32(data[index+1])
index += 2
length -= 2
}
if length > 0 {
sum += uint32(data[index])
}
sum += (sum >> 16)
return uint16(^sum)
}
func main() {
h := Header{
Version: 4,
Len: 20,
TotalLen: 20 + 8,
TTL: 1,
Protocol: 1,
// Dst:
}
argc := len(os.Args)
if argc < 2 {
fmt.Println("usage: program + host")
return
}
ipAddr, _ := net.ResolveIPAddr("ip", os.Args[1])
h.Dst = ipAddr.IP
icmpReq := ICMP{
Type: 8,
Code: 0,
Identifier: 0,
SeqNo: 0,
}
out, err := h.Marshal()
if err != nil {
fmt.Println("ip header error", err)
return
}
var icmpBuf bytes.Buffer
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
icmpReq.Checksum = Checksum(icmpBuf.Bytes())
icmpBuf.Reset()
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
fd, _ := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
addr := syscall.SockaddrInet4{
Port: 0,
}
copy(addr.Addr[:], ipAddr.IP[12:16])
pkg := append(out, icmpBuf.Bytes()...)
fmt.Println("ip length", len(pkg))
if err := syscall.Sendto(fd, pkg, 0, &addr); err != nil {
fmt.Println("Sendto err:", err)
}
var recvBuf []byte
if nBytes, rAddr, err := syscall.Recvfrom(fd, recvBuf, 0); err == nil {
fmt.Printf("recv %d bytes from %v\n", nBytes, rAddr)
}
}
另外,我使用了来自https://github.com/golang/net/tree/master/ipv4的header.go
和helper.go
文件。
英文:
I'm trying to send an icmp message whose TTL is just 1, and expect to receive a time exceeded message. that message does come(I see it from wireshark), but my program blocks on syscall.Recvfrom
. Anyone knows why?
icmp.go
package main
import (
"bytes"
"encoding/binary"
"fmt"
"net"
"os"
"syscall"
)
type ICMP struct {
Type uint8
Code uint8
Checksum uint16
Identifier uint16
SeqNo uint16
}
func Checksum(data []byte) uint16 {
var (
sum uint32
length int = len(data)
index int
)
for length > 1 {
sum += uint32(data[index])<<8 + uint32(data[index+1])
index += 2
length -= 2
}
if length > 0 {
sum += uint32(data[index])
}
sum += (sum >> 16)
return uint16(^sum)
}
func main() {
h := Header{
Version: 4,
Len: 20,
TotalLen: 20 + 8,
TTL: 1,
Protocol: 1,
// Dst:
}
argc := len(os.Args)
if argc < 2 {
fmt.Println("usage: program + host")
return
}
ipAddr, _ := net.ResolveIPAddr("ip", os.Args[1])
h.Dst = ipAddr.IP
icmpReq := ICMP{
Type: 8,
Code: 0,
Identifier: 0,
SeqNo: 0,
}
out, err := h.Marshal()
if err != nil {
fmt.Println("ip header error", err)
return
}
var icmpBuf bytes.Buffer
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
icmpReq.Checksum = Checksum(icmpBuf.Bytes())
icmpBuf.Reset()
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
fd, _ := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
addr := syscall.SockaddrInet4{
Port: 0,
}
copy(addr.Addr[:], ipAddr.IP[12:16])
pkg := append(out, icmpBuf.Bytes()...)
fmt.Println("ip length", len(pkg))
if err := syscall.Sendto(fd, pkg, 0, &addr); err != nil {
fmt.Println("Sendto err:", err)
}
var recvBuf []byte
if nBytes, rAddr, err := syscall.Recvfrom(fd, recvBuf, 0); err == nil {
fmt.Printf("recv %d bytes from %v\n", nBytes, rAddr)
}
}
additionally, I use header.go
and helper.go
from https://github.com/golang/net/tree/master/ipv4
答案1
得分: 2
正如Andy指出的,raw(7) man page中提到:
> IPPROTO_RAW套接字只能用于发送。如果你真的想接收所有的IP数据包,请使用具有ETH_P_IP协议的packet(7)套接字。请注意,与原始套接字不同,数据包套接字不会重新组装IP片段。
我知道如果我在创建套接字时将协议设置为IPPROTO_ICMP
,我可以接收到ICMP回复,但是我需要在IP层设置TTL
为1。因此,我使用IPPROTO_RAW
套接字发送ICMP请求,然后使用net.ListenIP
接收ICMP消息。以下是代码:
package main
import (
"bytes"
"encoding/binary"
"log"
"net"
"os"
"syscall"
)
const icmpID uint16 = 43565 // 暂时使用一个魔术数
type ICMP struct {
Type uint8
Code uint8
Checksum uint16
Identifier uint16
SeqNo uint16
}
func Checksum(data []byte) uint16 {
var (
sum uint32
length int = len(data)
index int
)
for length > 1 {
sum += uint32(data[index])<<8 + uint32(data[index+1])
index += 2
length -= 2
}
if length > 0 {
sum += uint32(data[index])
}
sum += (sum >> 16)
return uint16(^sum)
}
func main() {
h := Header{
Version: 4,
Len: 20,
TotalLen: 20 + 8,
TTL: 1,
Protocol: 1,
}
argc := len(os.Args)
if argc < 2 {
log.Println("usage: program + host")
return
}
ipAddr, _ := net.ResolveIPAddr("ip", os.Args[1])
h.Dst = ipAddr.IP
icmpReq := ICMP{
Type: 8,
Code: 0,
Identifier: icmpID,
SeqNo: 1,
}
out, err := h.Marshal()
if err != nil {
log.Println("ip header error", err)
return
}
var icmpBuf bytes.Buffer
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
icmpReq.Checksum = Checksum(icmpBuf.Bytes())
icmpBuf.Reset()
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
fd, _ := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
addr := syscall.SockaddrInet4{
Port: 0,
}
copy(addr.Addr[:], ipAddr.IP[12:16])
pkg := append(out, icmpBuf.Bytes()...)
if err := syscall.Sendto(fd, pkg, 0, &addr); err != nil {
log.Println("Sendto err:", err)
}
laddr, err := net.ResolveIPAddr("ip4:icmp", "0.0.0.0")
if err != nil {
log.Fatal(err)
}
c, err := net.ListenIP("ip4:icmp", laddr)
if err != nil {
log.Fatal(err)
}
for {
buf := make([]byte, 2048)
n, raddr, err := c.ReadFrom(buf)
if err != nil {
log.Println(err)
continue
}
icmpType := buf[0]
if icmpType == 11 {
if n == 36 { // Time exceeded messages
// A time exceeded message contain IP header(20 bytes) and first 64 bits of the original payload
id := binary.BigEndian.Uint16(buf[32:34])
log.Println("recv id", id)
if id == icmpID {
log.Println("recv Time Exceeded from", raddr)
}
}
}
}
}
实际上,我正在使用Go语言编写一个traceroute程序,如果有人对此感兴趣,完整的代码可以在GitHub上找到。
英文:
As Andy pointed out, the raw(7) man page says:
> An IPPROTO_RAW socket is send only. If you really want to receive
all IP packets, use a packet(7) socket with the ETH_P_IP protocol.
Note that packet sockets don't reassemble IP fragments, unlike raw
sockets.
I know I can receive ICMP reply if I set IPPROTO_ICMP
as the protocol when I create the socket, but I need to set TTL
to 1 which must be done in IP layer. Therefore I send the ICMP request with IPPROTO_RAW
socket, after that I use net.ListenIP
to receive ICMP messages. Here is the code:
package main
import (
"bytes"
"encoding/binary"
"log"
"net"
"os"
"syscall"
)
const icmpID uint16 = 43565 // use a magic number for now
type ICMP struct {
Type uint8
Code uint8
Checksum uint16
Identifier uint16
SeqNo uint16
}
func Checksum(data []byte) uint16 {
var (
sum uint32
length int = len(data)
index int
)
for length > 1 {
sum += uint32(data[index])<<8 + uint32(data[index+1])
index += 2
length -= 2
}
if length > 0 {
sum += uint32(data[index])
}
sum += (sum >> 16)
return uint16(^sum)
}
func main() {
h := Header{
Version: 4,
Len: 20,
TotalLen: 20 + 8,
TTL: 1,
Protocol: 1,
}
argc := len(os.Args)
if argc < 2 {
log.Println("usage: program + host")
return
}
ipAddr, _ := net.ResolveIPAddr("ip", os.Args[1])
h.Dst = ipAddr.IP
icmpReq := ICMP{
Type: 8,
Code: 0,
Identifier: icmpID,
SeqNo: 1,
}
out, err := h.Marshal()
if err != nil {
log.Println("ip header error", err)
return
}
var icmpBuf bytes.Buffer
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
icmpReq.Checksum = Checksum(icmpBuf.Bytes())
icmpBuf.Reset()
binary.Write(&icmpBuf, binary.BigEndian, icmpReq)
fd, _ := syscall.Socket(syscall.AF_INET, syscall.SOCK_RAW, syscall.IPPROTO_RAW)
addr := syscall.SockaddrInet4{
Port: 0,
}
copy(addr.Addr[:], ipAddr.IP[12:16])
pkg := append(out, icmpBuf.Bytes()...)
if err := syscall.Sendto(fd, pkg, 0, &addr); err != nil {
log.Println("Sendto err:", err)
}
laddr, err := net.ResolveIPAddr("ip4:icmp", "0.0.0.0")
if err != nil {
log.Fatal(err)
}
c, err := net.ListenIP("ip4:icmp", laddr)
if err != nil {
log.Fatal(err)
}
for {
buf := make([]byte, 2048)
n, raddr, err := c.ReadFrom(buf)
if err != nil {
log.Println(err)
continue
}
icmpType := buf[0]
if icmpType == 11 {
if n == 36 { // Time exceeded messages
// A time exceeded message contain IP header(20 bytes) and first 64 bits of the original payload
id := binary.BigEndian.Uint16(buf[32:34])
log.Println("recv id", id)
if id == icmpID {
log.Println("recv Time Exceeded from", raddr)
}
}
}
}
}
Actually, I am writing a traceroute in go, if anyone is interested about that, the whole code is in github.
答案2
得分: 1
我认为在创建套接字时,你需要将协议设置为IPPROTO_ICMP
。raw(7) man page中提到,IPPROTO_RAW
套接字只能用于发送。此外,如果你使用IPPROTO_ICMP
,就不需要提供IP头部。(注意:我没有在Go中实际尝试过这个。)
英文:
I think you need to give IPPROTO_ICMP
as the protocol when you create your socket. The raw(7) man page says that an IPPROTO_RAW
socket is send only. Also, if you use IPPROTO_ICMP
, you don't give the IP header. (Note: I haven't actually tried this in Go.)
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