c - Mac OS X 上的奇怪 RAW 套接字

Question

当我在我的 Mac OS X 上运行一个用 C 编码的简单数据包嗅探器时，我根本没有输出，这是一件奇怪的事情!有人可以帮助我了解发生了什么。

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

int main(void) {
   int i, recv_length, sockfd;

   u_char buffer[9000];

   if ((sockfd = socket(PF_INET, SOCK_RAW, IPPROTO_TCP)) == -1) {
        printf("Socket failed!!\n");

        return -1;
   }

   for(i=0; i < 3; i++) {
      recv_length = recv(sockfd, buffer, 8000, 0);
      printf("Got some bytes : %d\n", recv_length);
   }

   return 0;
}

我编译它并在我的盒子上运行它，但没有任何进展:

MacOsxBox:Desktop evariste$sudo ./simpleSniffer

感谢您的帮助。

Answer 1

这不适用于 *BSD(包括 OSX/Darwin)。看调查here了解更多详情:

b. FreeBSD
**********

FreeBSD takes another approach. It *never* passes TCP or UDP packets to raw
sockets. Such packets need to be read directly at the datalink layer by using
libraries like libpcap or the bpf API. It also *never* passes any fragmented 
datagram. Each datagram has to be completeley reassembled before it is passed
to a raw socket.
FreeBSD passes to a raw socket:
    a) every IP datagram with a protocol field that is not registered in
    the kernel
    b) all IGMP packets after kernel finishes processing them
    c) all ICMP packets (except echo request, timestamp request and address
    mask request) after kernel finishes processes them

故事的寓意:为此使用libpcap。它会让你的生活更轻松。 (如果您使用 MacPorts，请执行 sudo port install libpcap。)