C 未接收到从tap接口发送的广播数据包
我正在制作一个类似simpletun的程序C 未接收到从tap接口发送的广播数据包,c,linux,sockets,tun,C,Linux,Sockets,Tun,我正在制作一个类似simpletun的程序 应用程序向tap接口发送UDP广播 在tap接口上收听的节目(类似于simpletun)接收数据包,并将其作为广播再次回音 我可以在wireshark上看到这两个数据包,但应用程序没有收到它。看起来内核正在删除它们 如果从不同的机器发送相似的数据包。它很好用 tun/tap代码:- char datagram[4096]; struct pseudo_header { u_int32_t source_address;
char datagram[4096];
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;
};
struct pseudo_header psh;
char *pseudogram;
nread = cread(tap_fd, buffer, BUFSIZE);
memcpy(&source_port,(char *)(buffer+14+20),2);
memset (datagram, 0, 4096);
memcpy(datagram,buffer,14); //copy eth-header
datagram[6] = 0xXX;//change mac address
datagram[7] = 0xXX;
datagram[8] = 0xXX;
//IP header
struct iphdr *iph = (struct iphdr *) (datagram +14);
//TCP header
struct udphdr *udph = (struct udphdr *) (datagram + 14 + sizeof (struct iphdr));
data = datagram + sizeof(struct iphdr) + sizeof(struct udphdr) +14;
strcpy(data,"Any string");
iph->ihl = 5;
iph->version = 4;
iph->tos = 0;
iph->tot_len = sizeof (struct iphdr) + sizeof (struct udphdr) + strlen(data);
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
strcpy(source_ip , "192.168.0.99");
iph->saddr = inet_addr ( source_ip ); //Spoof the source ip address
strcpy(destination_ip , "255.255.255.255");
iph->daddr = inet_addr (destination_ip);
udph->source = htons(5933);
//udph->dest = htons(source_port);
udph->dest = (source_port);
udph->len = htons(sizeof(struct udphdr) + strlen(data));
//Now the UDP checksum
psh.source_address = inet_addr( source_ip );
psh.dest_address = inet_addr(destination_ip);
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 = malloc(psize);
memcpy(pseudogram , (char*) &psh , sizeof (struct pseudo_header));
memcpy(pseudogram + sizeof(struct pseudo_header) , udph , sizeof(struct udphdr) + strlen(data));
memcpy(pseudogram + sizeof(struct pseudo_header) + sizeof(struct udphdr), data , strlen(data));
udph->check = 0;
udph->check = csum( (unsigned short*) pseudogram , psize);
//Ip checksum
iph->check = csum ((unsigned short *) datagram, iph->tot_len);
//writeback
cwrite(tap_fd,datagram,iph->tot_len +14);
当使用原始套接字读写从另一台机器运行时,上述代码运行良好。(不带eth标题)
接收申请代码:-
int broadcast =1;
if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
err("socket");
setsockopt(sockfd,SOL_SOCKET,SO_BINDTODEVICE,"tun0",5);
bzero(&my_addr, sizeof(my_addr));
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(PORT);
memset(&my_addr.sin_addr.s_addr,255,sizeof(my_addr.sin_addr.s_addr));
ret = setsockopt(sockfd,SOL_SOCKET,SO_BROADCAST,&broadcast,sizeof(broadcast));
if(ret<0)
printf("setsockopt bindto failed");
if (sendto(sockfd,buf,500,0, (struct sockaddr*)&my_addr,slen_len) == -1)
err("send()");
recvfrom(sockfd, buf, 500, 0, (struct sockaddr*)&cli_addr, &slen);
int广播=1;
if((sockfd=socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP))=-1)
错误(“套接字”);
setsockopt(sockfd,SOL_SOCKET,SO_BINDTODEVICE,“tun0”,5);
bzero(&my_addr,sizeof(my_addr));
我的地址sin家庭=AFINET;
my_addr.sin_port=htons(端口);
memset(&my_addr.sin_addr.s_addr,255,sizeof(my_addr.sin_addr.s_addr));
ret=setsockopt(sockfd、SOL_SOCKET、SO_BROADCAST和BROADCAST、sizeof(BROADCAST));
如果(ret您是否检查了主机防火墙规则?在黑暗中拍摄猜测:
但是,当它将IP目的地视为广播IP(255.255.255.255)时,您可以尝试更改TUN/TAP代码,将目的地MAC地址设置为广播(FF:FF:FF:FF:FF:FF)地址。通过对IP头的tot\U len使用正确的校验和字节顺序来解决此问题
iph->tot_len=(htons)sizeof(struct iphdr)+sizeof(struct udphdr)+strlen(data);
iph->id=htons(54321);//此数据包的id
iph->check=htons(csum((无符号短*)数据报,sizeof(struct ip_hdr));
**其中,csum是计算校验和的常用函数
由于内核的网络堆栈正在重新计算iph->tot_len和ip校验和,所以从另一台机器接收到了数据包,因此数据包的格式正确
在更正应用程序收到tot_len数据包的校验和和字节顺序后,使用my tun接口。防火墙被禁用服务ufw stop
,则可能您没有在特定计算机上使用原始套接字的良好权限。例如,Windows不允许您创建完整的原始套接字。您可以在其中调用setsockopt带SO_广播-广播的类型和初始化值是什么变量?广播设置为1。仅添加了代码的相关部分。int broadcast=1;
这应该是正确的。这只是一种预感。嘿,感谢支持我并促使我更正进出tun/tap接口的两个数据包中的dest mac和dest ip。我在这一行中所做的更改数据报[6]=0xXX;//更改mac地址
仅是回显数据包时的源mac