我正在尝试使用套接字来嗅探 OpenFlow 数据包。我有一些代码试图收集 OF 数据包并打印标题信息，但它似乎没有打印正确的信息。我已经在 mininet 中设置了一个环境并将其指向一个遥控器。在wireshark中，我看到标准的回显请求/回复正在进行，在openflow中是在标题部分定义的类型2和3。当我查看我在程序中收集的数据包数据时，我似乎打印了奇数的 2 类数据包，没有其他任何东西让我认为我的代码不正确，并且打印的 2 类数据包不是 2 类数据包。
我一直在玩这个，所以如果它有点混乱/不完美，我很抱歉。我试图让它对每个人都可读：
#include <stdio.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <openflow/openflow.h>
#include "openflow/lib/ofpbuf.h"
int sock_raw;
void DieWithError(char *errorMessage);
void handlePacket(unsigned char *, int);
void printOFHeader(struct ofp_header *);
int main()
{
int saddr_size , data_size;
struct sockaddr saddr;
unsigned char *buffer = (unsigned char *)malloc(65536); //Its Big! -- Malloc allocates a block of size bytes of memory, returning a pointer to the beginning of the block
printf("Starting...\n");
//Create a raw socket that shall sniff
sock_raw = socket(AF_INET , SOCK_RAW , IPPROTO_TCP);
printf("socket: %d\n",sock_raw);
if(sock_raw < 0)
{
printf("Socket Error\n");
return 1;
}
while(1)
{
saddr_size = sizeof saddr;
//Receive a packet
data_size = recvfrom(sock_raw, buffer, 65536, 0 , &saddr , (socklen_t*)&saddr_size);
if(data_size <0 )
{
printf("Recvfrom error , failed to get packets\n");
return 1;
}
//Now process the packet
handlePacket(buffer, data_size);
}
close(sock_raw);
printf("Finished");
return 0;
}
void DieWithError(char *errorMessage)
{
perror(errorMessage);
exit(1);
}
void handlePacket(unsigned char *buff, int data_size)
{
//first get IP header length
struct iphdr *iph = (struct iphdr *)buff;
unsigned short iphdrlen = iph->ihl*4;
//get tcp header length
struct tcphdr *tcph = (struct tcphdr*)(buff + iphdrlen);
unsigned int ofph_offset = (iphdrlen+(unsigned int)tcph->doff*4);
//add total length of ip and tcp headers to the buffer to get the start of the OF Header
struct ofp_header *oh = (struct ofp_header*)(buff + ofph_offset);
//Check it is an OF Header -- Not sure this is right
if(oh->version == OFP_VERSION)
{
printOFHeader(oh);
}
else
{
printf("This is not an openflow packet\n");
}
}
void printOFHeader(struct ofp_header * oh)
{
printf("OPENFLOW PACKET HEADER\n");
printf(" |-OF Version %d\n", oh->version);
printf(" |-Type: %d\n", oh->type);
printf(" |-Transaction ID: %d\n", oh->xid);
printf(" |-Length: %d\n", oh->length);
printf("----------------------------------------------------");
printf("\n");
}
我已经测试了以下数据：
//first get IP header length
struct iphdr *iph = (struct iphdr *)buff;
unsigned short iphdrlen = iph->ihl*4;
//get tcp header length
struct tcphdr *tcph = (struct tcphdr*)(buff + iphdrlen);
这些打印数据包的正确端口地址和 IP 地址，所以我认为我的缺陷在于我如何分配 ofp_header 结构。这个问题最好放在 openflow.org 网站上，但我找不到邮件组。