在Linux上嗅探以太网接口

Sniffing an ethernet interface on linux

本文关键字：以太网 接口 嗅探 Linux      更新时间：2023-10-16

我正在尝试从特定接口中捕获数据包，而是从所有接口中获取数据包。我在做什么错？

bool Snooper::raw_init (const char *device)
{
uid_t    privid = geteuid();
int      retval;
bool     retVal = false;
do {
    if ((retval = setuid(0)) != 0) {
        perror("seteuid error");
        break;
    }
    cap_t caps = cap_get_proc();
    cap_value_t cap_list[2];
    cap_list[0] = CAP_NET_RAW;
    cap_list[1] = CAP_SETUID;
    if ((retval = cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET)) == -1) {
        perror("cap_set_flag error");
        break;
    }
    if ((retval = cap_set_proc(caps)) == -1) {
        perror("cap_set_proc error");
        break;
    }
    struct ifreq ifr;
    memset(&ifr, 0, sizeof (struct ifreq));
    /* Open A Raw Socket */
    if ((m_sockfd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_ALL))) < 1) {
        perror("Snooper::raw_init:socket Error");
        break;
    }
    /* Set the device to use */
    strncpy(ifr.ifr_name, device, strlen(device) + 1);
    /* Get the current flags that the device might have */
    if (ioctl(m_sockfd, SIOCGIFFLAGS, &ifr) == -1) {
        perror("Error: Could not retrieve the flags from the device.n");
        break;
    }
    printf("The interface is ::: %sn", device);
    perror("Retrieved flags from interface successfully");
    /* Set the old flags plus the IFF_PROMISC flag */
    ifr.ifr_flags |= IFF_PROMISC;
    if (ioctl(m_sockfd, SIOCSIFFLAGS, &ifr) == -1) {
        perror("Error: Could not set flag IFF_PROMISC");
        break;
    }
    printf("Setting interface ::: %s ::: to promiscn", device);
    /* Configure the device */
    if (ioctl(m_sockfd, SIOCGIFINDEX, &ifr) < 0) {
        perror("Error: Error getting the device index.n");
        break;
    }
    retVal = true;
} while(false);
if ((retval = seteuid(privid)) != 0) {
    perror("seteuid error");
}
return retVal;
}

我首先验证我可以提起扎根，因为IFF_Promisc需要它。然后为UDP流量创建套接字，为设备预成立IOCTL，最后为Promisc。

。

现在我有一个插座，我在RECV上循环，但是我也从其他接口中获取数据包。

要从特定接口捕获数据包，必须使用bind函数将套接字绑定到该接口。您可以查看此答案以示例。

一个可能能够帮助您的小型pcap程序

#include<stdio.h> 
#include<stdlib.h>
#include<string.h>
#include<pcap/pcap.h>
#include<netinet/if_ether.h>
#include<netinet/ip.h>
#include<netinet/tcp.h>
void process_packet(u_char *args, const struct pcap_pkthdr *header,
                               const u_char *buffer)
{
//  printf("In Process_Packetn");
struct ethhdr *eth = (struct ethhdr *)(buffer);
printf("%.2x: %.2x: %.2x: %.2x: %.2x: %.2x: %.2x:n ", eth->h_dest[0], eth->h_dest[1], eth->h_dest[2], eth->h_dest[3], eth->h_dest[4], eth->h_dest[5], eth->h_dest[6]);
printf("%x n", htons(eth->h_proto));
if(htons(eth->h_proto)== ETHERTYPE_ARP)
{
    printf("ARP PACKETn");
}
struct iphdr *iph = (struct iphdr*)(buffer + sizeof(struct ethhdr));
int ipheader = iph-> ihl *4;
printf("Source IP Address :%sn ", inet_ntoa(iph->saddr));
printf("Destination IP Address :%sn ", inet_ntoa(iph->daddr));
}
int main()
{
pcap_if_t *alldevspec,*devices;
pcap_addr_t *a;
pcap_t *handle;
const char filter_exp[]="IP";
bpf_u_int32 netp;
char errbuf[PCAP_ERRBUF_SIZE];
struct bpf_program fp;
int ret=0, count =1, n=0;
char devs[100][100],*devicename;
ret = pcap_findalldevs(&alldevspec,errbuf);
if(ret < 0)
{
    printf("Error in finding the devicesn");
    return -1;
}
for(devices = alldevspec; devices!= NULL; devices = devices->next)
{
    printf("%d %s-%s n",count, devices->name,devices->description);
    for(a=devices->addresses;a;a=a->next)
    {
        printf("family %d n", (a->addr)->sa_family);
        if(devices->name != NULL)
        {
            strcpy(devs[count], devices->name);
        }
        switch((a->addr)->sa_family)
        {
            case AF_INET:
            printf("%s n",inet_ntoa(((struct sockaddr_in*)a->addr)->sin_addr.s_addr));
            break;
            case AF_INET6:
            break;
        }
    }
++count;
}
printf("Enter the device u want to selectn");
scanf("%d",&n);
devicename = devs[n];
handle = pcap_open_live(devicename,65536,1,-1,errbuf);
if(handle == NULL)
{
    printf("Error in opening the devicen");
    return -1;
}
pcap_compile(handle,&fp, filter_exp,-1,netp);
pcap_setfilter(handle, &fp);
pcap_loop(handle,-1,process_packet,NULL);
return 0;
}
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