下面是一个例子,用底层Socket函数实现了ICMP协议的功能,改成UDP应该不难.
它实现了报文的校验和计算等底层功能.
#define WIN32_LEAN_AND_MEAN
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdio.h>
#include <stdlib.h>
#define IP_RECORD_ROUTE 0x7
typedef struct _iphdr
{
unsigned int h_len:4;
// Length of the header
unsigned int version:4;
// Version of IP
unsigned char tos;
// Type of service
unsigned short total_len;
// Total length of the packet
unsigned short ident;
// Unique identifier
unsigned short frag_and_flags;
// Flags
unsigned char ttl;
// Time to live
unsigned char proto;
// Protocol (TCP, UDP etc)
unsigned short checksum;
// IP checksum
unsigned int sourceIP;
unsigned int destIP;
} IpHeader;
#define ICMP_ECHO 8
#define ICMP_ECHOREPLY 0
#define ICMP_MIN 8 // Minimum 8-byte ICMP packet (header)
typedef struct _icmphdr
{
BYTE i_type;
BYTE i_code;
// Type sub code
USHORT i_cksum;
USHORT i_id;
USHORT i_seq;
ULONG timestamp;
} IcmpHeader;
typedef struct _ipoptionhdr
{
unsigned char code;
// Option type
unsigned char len;
// Length of option hdr
unsigned char ptr;
// Offset into options
unsigned long addr[9];
// List of IP addrs
} IpOptionHeader;
#define DEF_PACKET_SIZE 32 // Default packet size
#define MAX_PACKET 1024 // Max ICMP packet size
#define MAX_IP_HDR_SIZE 60 // Max IP header size w/options
BOOL bRecordRoute;
int datasize;
char *lpdest;
void usage(char *progname)
{
printf("usage: ping -r <host> [data size]/n");
printf(" -r record route/n");
printf(" host remote machine to ping/n");
printf(" datasize can be up to 1KB/n");
ExitProcess(-1);
}
void FillICMPData(char *icmp_data, int datasize)
{
IcmpHeader *icmp_hdr = NULL;
char *datapart = NULL;
icmp_hdr = (IcmpHeader*)icmp_data;
icmp_hdr->i_type = ICMP_ECHO;
// Request an ICMP echo
icmp_hdr->i_code = 0;
icmp_hdr->i_id = (USHORT)GetCurrentProcessId();
icmp_hdr->i_cksum = 0;
icmp_hdr->i_seq = 0;
datapart = icmp_data + sizeof(IcmpHeader);
memset(datapart,'E', datasize - sizeof(IcmpHeader));
}
USHORT checksum(USHORT *buffer, int size)
{
unsigned long cksum=0;
while (size > 1)
{
cksum += *buffer++;
size -= sizeof(USHORT);
}
if (size)
{
cksum += *(UCHAR*)buffer;
}
cksum = (cksum >> 16) + (cksum &
0xffff);
cksum += (cksum >>16);
return (USHORT)(~cksum);
}
void DecodeIPOptions(char *buf, int bytes)
{
IpOptionHeader *ipopt = NULL;
IN_ADDR inaddr;
int i;
HOSTENT *host = NULL;
ipopt = (IpOptionHeader *)(buf + 20);
printf("RR: ");
for(i = 0;
i < (ipopt->ptr / 4) - 1;
i++)
{
inaddr.S_un.S_addr = ipopt->addr;
if (i != 0)
printf(" ");
host = gethostbyaddr((char *)&inaddr.S_un.S_addr,
sizeof(inaddr.S_un.S_addr), AF_INET);
if (host)
printf("(%-15s) %s/n", inet_ntoa(inaddr), host->h_name);
else
printf("(%-15s)/n", inet_ntoa(inaddr));
}
return;
}
void DecodeICMPHeader(char *buf, int bytes,
struct sockaddr_in *from)
{
IpHeader *iphdr = NULL;
IcmpHeader *icmphdr = NULL;
unsigned short iphdrlen;
DWORD tick;
static int icmpcount = 0;
iphdr = (IpHeader *)buf;
// Number of 32-bit words * 4 = bytes
iphdrlen = iphdr->h_len * 4;
tick = GetTickCount();
if ((iphdrlen == MAX_IP_HDR_SIZE) &&
(!icmpcount))
DecodeIPOptions(buf, bytes);
if (bytes < iphdrlen + ICMP_MIN)
{
printf("Too few bytes from %s/n",
inet_ntoa(from->sin_addr));
}
icmphdr = (IcmpHeader*)(buf + iphdrlen);
if (icmphdr->i_type != ICMP_ECHOREPLY)
{
printf("nonecho type %d recvd/n", icmphdr->i_type);
return;
}
// Make sure this is an ICMP reply to something we sent!
//
if (icmphdr->i_id != (USHORT)GetCurrentProcessId())
{
printf("someone else
's packet!/n");
return ;
}
printf("%d bytes from %s:", bytes, inet_ntoa(from->sin_addr));
printf(" icmp_seq = %d. ", icmphdr->i_seq);
printf(" time: %d ms", tick - icmphdr->timestamp);
printf("/n");
icmpcount++;
return;
}
void ValidateArgs(int argc, char **argv)
{
int i;
bRecordRoute = FALSE;
lpdest = NULL;
datasize = DEF_PACKET_SIZE;
for(i = 1;
i < argc;
i++)
{
if ((argv[0] == '-') || (argv[0] == '/'))
{
switch (tolower(argv[1]))
{
case 'r': // Record route option
bRecordRoute = TRUE;
break;
default:
usage(argv[0]);
break;
}
}
else
if (isdigit(argv[0]))
datasize = atoi(argv);
else
lpdest = argv;
}
}
//
// Function: main
//
int main(int argc, char **argv)
{
WSADATA wsaData;
SOCKET sockRaw = INVALID_SOCKET;
struct sockaddr_in dest,
from;
int bread,
fromlen = sizeof(from),
timeout = 1000,
ret;
char *icmp_data = NULL,
*recvbuf = NULL;
unsigned int addr = 0;
USHORT seq_no = 0;
struct hostent *hp = NULL;
IpOptionHeader ipopt;
if (WSAStartup(MAKEWORD(2, 2), &wsaData) != 0)
{
printf("WSAStartup() failed: %d/n", GetLastError());
return -1;
}
ValidateArgs(argc, argv);
sockRaw = WSASocket (AF_INET, SOCK_RAW, IPPROTO_ICMP, NULL, 0,
WSA_FLAG_OVERLAPPED);
if (sockRaw == INVALID_SOCKET)
{
printf("WSASocket() failed: %d/n", WSAGetLastError());
return -1;
}
if (bRecordRoute)
{
// Setup the IP option header to go out on every ICMP packet
//
ZeroMemory(&ipopt, sizeof(ipopt));
ipopt.code = IP_RECORD_ROUTE;
// Record route option
ipopt.ptr = 4;
// Point to the first addr offset
ipopt.len = 39;
// Length of option header
ret = setsockopt(sockRaw, IPPROTO_IP, IP_OPTIONS,
(char *)&ipopt, sizeof(ipopt));
if (ret == SOCKET_ERROR)
{
printf("setsockopt(IP_OPTIONS) failed: %d/n",
WSAGetLastError());
}
}
// Set the send/recv timeout values
//
bread = setsockopt(sockRaw, SOL_SOCKET, SO_RCVTIMEO,
(char*)&timeout, sizeof(timeout));
if(bread == SOCKET_ERROR)
{
printf("setsockopt(SO_RCVTIMEO) failed: %d/n",
WSAGetLastError());
return -1;
}
timeout = 1000;
bread = setsockopt(sockRaw, SOL_SOCKET, SO_SNDTIMEO,
(char*)&timeout, sizeof(timeout));
if (bread == SOCKET_ERROR)
{
printf("setsockopt(SO_SNDTIMEO) failed: %d/n",
WSAGetLastError());
return -1;
}
memset(&dest, 0, sizeof(dest));
//
// Resolve the endpoint's name if necessary
//
dest.sin_family = AF_INET;
if ((dest.sin_addr.s_addr = inet_addr(lpdest)) == INADDR_NONE)
{
if ((hp = gethostbyname(lpdest)) != NULL)
{
memcpy(&(dest.sin_addr), hp->h_addr, hp->h_length);
dest.sin_family = hp->h_addrtype;
printf("dest.sin_addr = %s/n", inet_ntoa(dest.sin_addr));
}
else
{
printf("gethostbyname() failed: %d/n",
WSAGetLastError());
return -1;
}
}
//
// Create the ICMP packet
//
datasize += sizeof(IcmpHeader);
icmp_data = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY,
MAX_PACKET);
recvbuf = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY,
MAX_PACKET);
if (!icmp_data)
{
printf("HeapAlloc() failed: %d/n", GetLastError());
return -1;
}
memset(icmp_data,0,MAX_PACKET);
FillICMPData(icmp_data,datasize);
//
// Start sending/receiving ICMP packets
//
while(1)
{
static int nCount = 0;
int bwrote;
if (nCount++ == 4)
break;
((IcmpHeader*)icmp_data)->i_cksum = 0;
((IcmpHeader*)icmp_data)->timestamp = GetTickCount();
((IcmpHeader*)icmp_data)->i_seq = seq_no++;
((IcmpHeader*)icmp_data)->i_cksum =
checksum((USHORT*)icmp_data, datasize);
bwrote = sendto(sockRaw, icmp_data, datasize, 0,
(struct sockaddr*)&dest, sizeof(dest));
if (bwrote == SOCKET_ERROR)
{
if (WSAGetLastError() == WSAETIMEDOUT)
{
printf("timed out/n");
continue;
}
printf("sendto() failed: %d/n", WSAGetLastError());
return -1;
}
if (bwrote < datasize)
{
printf("Wrote %d bytes/n", bwrote);
}
bread = recvfrom(sockRaw, recvbuf, MAX_PACKET, 0,
(struct sockaddr*)&from, &fromlen);
if (bread == SOCKET_ERROR)
{
if (WSAGetLastError() == WSAETIMEDOUT)
{
printf("timed out/n");
continue;
}
printf("recvfrom() failed: %d/n", WSAGetLastError());
return -1;
}
DecodeICMPHeader(recvbuf, bread, &from);
Sleep(1000);
}
// Cleanup
//
if (sockRaw != INVALID_SOCKET)
closesocket(sockRaw);
HeapFree(GetProcessHeap(), 0, recvbuf);
HeapFree(GetProcessHeap(), 0, icmp_data);
WSACleanup();
return 0;
}
!][