Question

我正在编写一个简单的traceroute程序使用ICMP数据包。验证传入的数据包时遇到问题。在发送icmp数据包之前，我将hcmp header id设置为进程ID。当我收到回复时，我只能在重播响应时获得icmp标头ID。问题是当时间超过响应时，因为我得到0作为icmp标题id。当超过时间时，我该怎么做才能获得icmp标头ID？或者也许还有另一种方法来识别响应？我需要知道响应是针对我的流程的。有人能帮助我吗？

我的设置icmp标题：

struct icmphdr setIcmpHdr(int sequence){
  struct icmphdr icmp_header;
  icmp_header.type = ICMP_ECHO;
  icmp_header.code = 0;
  icmp_header.un.echo.id = getpid(); // here I set the id
  icmp_header.un.echo.sequence = sequence;
  icmp_header.checksum = 0;
  icmp_header.checksum = compute_icmp_checksum((u_int16_t*)&icmp_header, 
                          sizeof(icmp_header));
  return icmp_header;
}

发送请求：

int sequence = hop;
struct icmphdr icmp_header = setIcmpHdr(sequence);
struct sockaddr_in recipeint = setRecipient(destination);
int ttl = hop;

setTTLOption(ttl, sockfd);

ssize_t bytes_sent = sendto(sockfd, &icmp_header, sizeof(icmp_header), 0,
                            (struct sockaddr*)&recipeint,sizeof(recipeint));

接收：

 //receiving

struct sockaddr_in sender;
socklen_t sender_len = sizeof(sender);
u_int8_t buffer[IP_MAXPACKET];

ssize_t packet_len = recvfrom(sockfd, buffer, IP_MAXPACKET, 0, (struct 
                                      sockaddr*)&sender, &sender_len);

char ip_str[20];
inet_ntop(AF_INET, &(sender.sin_addr), ip_str, sizeof(ip_str));

struct iphdr* ip_header = (struct iphdr*) buffer;
ssize_t ip_header_len = 4*ip_header->ihl;

u_int8_t* icmp_packet = (buffer + 4 * ip_header->ihl);
struct icmphdr *icmp_header2 = (struct icmphdr *) icmp_packet;

printf("pid: %d\n", icmp_header2->un.echo.id); //here is zero when it is time exceeded ;/
if(icmp_header2->type != 0){ 
     printf("IP packet with ICMP content from %s, hop %d\n\n", ip_str, 
               hop);
}else if(icmp_header2->type == 0){
     printf("Reached destination: %s with %d hops.\n", destination, hop);
     exit(EXIT_SUCCESS);
}

我将不胜感激任何帮助。：）

如何获得时间超过icmp标头响应ID？

0 个答案: