我在服务器端用原始套接字发包给客户端程序。出现了以下问题：
1. 如果客户端和服务端都绑定ip地址为0.0.0.0，虽然包能在客户端的机器上被wireshark抓到，但是不能被客户端程序收到。
2. 如果客户端绑定真实的ip地址，服务器端绑定0.0.0.0， 在有些无线网络环境下，包能够被客户端的wireshark抓到，但是不能客户端程序收到
3. 如果服务器端绑定真实ip地址，无论客户端绑定是0.0.0.0还是真实ip地址，都能正常收到包。
我的代码如下`
客户端：
int _tmain(int argc, _TCHAR* argv[])
{
SOCKET udpSock;
WSADATA wsa;
if(WSAStartup(MAKEWORD(2,2),&wsa)){
return 0;
}
udpSock = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP);
if(udpSock == INVALID_SOCKET){
return 0;
}
SOCKADDR_IN localAddr;
localAddr.sin_family = AF_INET;
localAddr.sin_port = htons(8622);
//localAddr.sin_addr.s_addr = INADDR_ANY;
//localAddr.sin_addr.s_addr = inet_addr("192.168.191.5");
localAddr.sin_addr.s_addr = inet_addr("10.6.192.112");
int opt = 1;
::setsockopt( udpSock, IPPROTO_UDP, 19,(char*) &opt, sizeof ( opt ) );
int aa = 8192;
::setsockopt(udpSock,SOL_SOCKET,SO_SNDBUF,(char*)&aa,sizeof(aa));
if(bind(udpSock,(sockaddr*)&localAddr,sizeof(localAddr)) != 0){
return 0;
}
sockaddr_in RecvAddr;
RecvAddr.sin_family = AF_INET;
RecvAddr.sin_port = htons(8821);
RecvAddr.sin_addr.s_addr = inet_addr("10.6.192.111");
char sendBuf[2048];
strcpy(sendBuf,"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\0");
BYTE recvBuf[4096];
int recvLen = 0;
SOCKADDR_IN tmpAddr;
int tmpRecvLen;
tmpRecvLen = sizeof(tmpAddr);
int i = 0;
while(true)
{
int len2 = sendto(udpSock, sendBuf, strlen(sendBuf), 0, (SOCKADDR *) &RecvAddr, sizeof(RecvAddr));
printf("start recv");
Sleep(100);
ZeroMemory(recvBuf,4096);
recvLen = recvfrom(udpSock,(char *)recvBuf,4096,0,(SOCKADDR *)&tmpAddr,&tmpRecvLen);
printf("recvLen = %d\n",recvLen);
if(recvLen > 0)
{
recvLen = 0;
printf("%s ",recvBuf);
printf("\n");
}
}
closesocket(udpSock);
return 0;
}
服务器代码：
#include<stdio.h> //for printf
#include<string.h> //memset
#include<sys/socket.h> //for socket ofcourse
#include<stdlib.h> //for exit(0);
#include<errno.h> //For errno - the error number
#include<netinet/udp.h> //Provides declarations for udp header
#include<netinet/ip.h> //Provides declarations for ip header
#include <unistd.h>
#include <arpa/inet.h>
/*
96 bit (12 bytes) pseudo header needed for udp header checksum calculation
*/
struct pseudo_header
{
u_int32_t source_address;
u_int32_t dest_address;
u_int8_t placeholder;
u_int8_t protocol;
u_int16_t udp_length;
};
/*
Generic checksum calculation function
*/
unsigned short csum(unsigned short *ptr,int nbytes)
{
register long sum;
unsigned short oddbyte;
register short answer;
sum=0;
while(nbytes>1) {
sum+=*ptr++;
nbytes-=2;
}
if(nbytes==1) {
oddbyte=0;
*((u_char*)&oddbyte)=*(u_char*)ptr;
sum+=oddbyte;
}
sum = (sum>>16)+(sum & 0xffff);
sum = sum + (sum>>16);
answer=(short)~sum;
return(answer);
}
int main (void)
{
int RcvSock = socket(AF_INET, SOCK_DGRAM, 0);
struct sockaddr_in localAddr;
memset(&localAddr, 0, sizeof(struct sockaddr_in));
localAddr.sin_family = AF_INET;
localAddr.sin_addr.s_addr = inet_addr("0.0.0.0");
localAddr.sin_port = htons(8821);
if (bind(RcvSock, (struct sockaddr *)&localAddr, sizeof(struct sockaddr_in)) < 0)
{
printf("bind failed: %d\n", errno);
return -1;
}
char buf[2048]={0};
struct sockaddr_in remoteAddr;
memset(buf,0,sizeof(buf));
int srclen = sizeof(remoteAddr);
int len = recvfrom(RcvSock,buf,sizeof(buf),0,(sockaddr*)&remoteAddr,( socklen_t* )&srclen);
char * remoteIp = inet_ntoa(remoteAddr.sin_addr);
unsigned int remotePort = ntohl(remoteAddr.sin_port);
printf(" recv %s, remote ip %s, remote port %u\n",buf,remoteIp, remotePort);
char sBuf[2048]={0};
snprintf(sBuf,sizeof(sBuf),"iddddddhello\n");
sendto(RcvSock,sBuf,strlen(sBuf),0,(struct sockaddr*)&remoteAddr,sizeof(remoteAddr));
//Create a raw socket of type IPPROTO
int s = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
int on = 1;
if (setsockopt(s, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on)) < 0) {
printf(" can not set the IP_HDR_INCL option\n");
return -1;
}
if(s == -1)
{
//socket creation failed, may be because of non-root privileges
perror("Failed to create raw socket");
exit(1);
}
//Datagram to represent the packet
char datagram[4096] , source_ip[32] , *data , *pseudogram;
//zero out the packet buffer
memset (datagram, 0, 4096);
//IP header
struct iphdr *iph = (struct iphdr *) datagram;
//UDP header
struct udphdr *udph = (struct udphdr *) (datagram + sizeof (struct ip));
struct sockaddr_in *sin = &remoteAddr;
struct pseudo_header psh;
//Data part
data = datagram + sizeof(struct iphdr) + sizeof(struct udphdr);
strcpy(data , "ABCDEFGHIJKLMNOPQRSTUVWXYZ");
//some address resolution
strcpy(source_ip , "10.6.192.111");
// strcpy(source_ip , "0.0.0.0");
int tot_len = sizeof (struct iphdr) + sizeof (struct udphdr) + strlen(data);
//Fill in the IP Header
iph->ihl = 5;
iph->version = 4;
iph->tos = 0;
iph->tot_len = htonl(tot_len);
iph->id = htonl (54321); //Id of this packet
iph->frag_off = 0;
iph->ttl = 255;
iph->protocol = IPPROTO_UDP;
iph->check = 0; //Set to 0 before calculating checksum
iph->saddr = inet_addr ( source_ip ); //Spoof the source ip address
iph->daddr = remoteAddr.sin_addr.s_addr;
//Ip checksum
iph->check = csum ((unsigned short *) datagram, iph->tot_len);
//UDP header
udph->source = htons (8821);
udph->dest = remoteAddr.sin_port;
udph->len = htons(8 + strlen(data)); //tcp header size
udph->check = 0; //leave checksum 0 now, filled later by pseudo header
//Now the UDP checksum using the pseudo header
psh.source_address = inet_addr( source_ip );
psh.dest_address = remoteAddr.sin_addr.s_addr;
psh.placeholder = 0;
psh.protocol = IPPROTO_UDP;
psh.udp_length = htons(sizeof(struct udphdr) + strlen(data) );
int psize = sizeof(struct pseudo_header) + sizeof(struct udphdr) + strlen(data);
pseudogram = (char*)malloc(psize);
memcpy(pseudogram , (char*) &psh , sizeof (struct pseudo_header));
memcpy(pseudogram + sizeof(struct pseudo_header) , udph , sizeof(struct udphdr) + strlen(data));
udph->check = csum( (unsigned short*) pseudogram , psize);
//loop if you want to flood :)
while (1)
{
printf("start send\n");
//Send the packet
if (sendto (s, datagram, tot_len , 0, (struct sockaddr *) &remoteAddr, sizeof (remoteAddr)) < 0)
{
perror("sendto failed");
}
sleep(1);
}
return 0;
}
