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suricata抓包方式之一 AF_PACKET

2024-08-19 13:29:31   214人阅读

1、前言

　　　　linux提供了原始套接字RAW_SOCKET，可以抓取数据链路层的报文。这样可以对报文进行深入分析。今天介绍一下AF_PACKET的用法，分为两种方式。第一种方法是通过套接字，打开指定的网卡，然后使用recvmsg读取，实际过程需要需要将报文从内核区拷贝到用户区。第二种方法是使用packet_mmap，使用共享内存方式，在内核空间中分配一块内核缓冲区，然后用户空间程序调用mmap映射到用户空间。将接收到的skb拷贝到那块内核缓冲区中，这样用户空间的程序就可以直接读到捕获的数据包了。PACKET_MMAP减少了系统调用，不用recvmsg就可以读取到捕获的报文，相比原始套接字+recvfrom的方式，减少了一次拷贝和一次系统调用。libpcap就是采用第二种方式。suricata默认方式也是使用packet mmap抓包。

2、测试例子

　　为了方便测试，可以使用linux提供的sock_filter过滤ip地址。使用tcpdump可以反汇编出来过滤的条件。以www.qq.com为例进行说明：

ping www.qq.com得到ip地址：101.226.103.106

tcpdump ip -s 2048 -d host 101.226.103.106(000) ldh      [12](001) jeq      #0x800           jt 2    jf 7(002) ld       [26](003) jeq      #0x65e2676a      jt 6    jf 4(004) ld       [30](005) jeq      #0x65e2676a      jt 6    jf 7(006) ret      #2048(007) ret      #0
 tcpdump -dd host 101.226.103.106{ 0x28, 0, 0, 0x0000000c },{ 0x15, 0, 4, 0x00000800 },{ 0x20, 0, 0, 0x0000001a },{ 0x15, 8, 0, 0x65e2676a },{ 0x20, 0, 0, 0x0000001e },{ 0x15, 6, 7, 0x65e2676a },{ 0x15, 1, 0, 0x00000806 },{ 0x15, 0, 5, 0x00008035 },{ 0x20, 0, 0, 0x0000001c },{ 0x15, 2, 0, 0x65e2676a },{ 0x20, 0, 0, 0x00000026 },{ 0x15, 0, 1, 0x65e2676a },{ 0x6, 0, 0, 0x0000ffff },{ 0x6, 0, 0, 0x00000000 }

更新详细过滤细节可以参考： http://blog.csdn.net/eqiang8271/article/details/8489769

（1）第一种方法：

  1 #include <sys/types.h>  2 #include <sys/time.h>  3 #include <sys/ioctl.h>  4 #include <sys/socket.h>  5 #include <linux/types.h>  6 #include <netinet/in.h>  7 #include <netinet/udp.h>  8 #include <netinet/ip.h>  9 #include <netpacket/packet.h> 10 #include <net/ethernet.h> 11 #include <arpa/inet.h> 12 #include <string.h> 13 #include <signal.h> 14 #include <net/if.h> 15 #include <stdio.h> 16 #include <sys/uio.h> 17 #include <fcntl.h> 18 #include <unistd.h> 19 #include <linux/filter.h> 20 #include <stdlib.h> 21  22 #define ETH_HDR_LEN 14 23 #define IP_HDR_LEN 20 24 #define UDP_HDR_LEN 8 25 #define TCP_HDR_LEN 20 26  27 static int sock; 28  29 void sig_handler(int sig)  30 { 31     struct ifreq ethreq; 32     if(sig == SIGTERM) 33         printf("SIGTERM recieved, exiting.../n"); 34     else if(sig == SIGINT) 35         printf("SIGINT recieved, exiting.../n"); 36     else if(sig == SIGQUIT) 37         printf("SIGQUIT recieved, exiting.../n"); 38     // turn off the PROMISCOUS mode  39     strncpy(ethreq.ifr_name, "eth1", IFNAMSIZ); 40     if(ioctl(sock, SIOCGIFFLAGS, &ethreq) != -1) { 41         ethreq.ifr_flags &= ~IFF_PROMISC; 42         ioctl(sock, SIOCSIFFLAGS, &ethreq); 43     } 44     close(sock); 45     exit(0); 46 } 47  48 int main(int argc, char ** argv) { 49     int n; 50     char buf[2048]; 51     unsigned char *ethhead; 52     unsigned char *iphead; 53     struct ifreq ethreq; 54     struct sigaction sighandle; 55  56 #if 0 57     $tcpdump ip -s 2048 -d host 192.168.1.2 58         (000) ldh      [12] 59         (001) jeq      #0x800           jt 2 jf 7 60         (002) ld       [26] 61         (003) jeq      #0xc0a80102      jt 6 jf 4 62         (004) ld       [30] 63         (005) jeq      #0xc0a80102      jt 6 jf 7 64         (006) ret      #2048 65         (007) ret      #0 66 #endif 67  68 #if 0 69         测试访问www.qq.com  70         ping www.qq.com 得到ip地址为:101.226.103.106 71         tcpdump -dd host 101.226.103.106 72          { 0x28, 0, 0, 0x0000000c }, 73          { 0x15, 0, 4, 0x00000800 }, 74          { 0x20, 0, 0, 0x0000001a }, 75          { 0x15, 8, 0, 0x65e2676a }, 76          { 0x20, 0, 0, 0x0000001e }, 77          { 0x15, 6, 7, 0x65e2676a }, 78          { 0x15, 1, 0, 0x00000806 }, 79          { 0x15, 0, 5, 0x00008035 }, 80          { 0x20, 0, 0, 0x0000001c }, 81          { 0x15, 2, 0, 0x65e2676a }, 82          { 0x20, 0, 0, 0x00000026 }, 83          { 0x15, 0, 1, 0x65e2676a }, 84          { 0x6, 0, 0, 0x0000ffff }, 85          { 0x6, 0, 0, 0x00000000 }, 86 #endif 87         struct sock_filter bpf_code[] = { 88             { 0x28, 0, 0, 0x0000000c }, 89             { 0x15, 0, 5, 0x00000800 }, 90             { 0x20, 0, 0, 0x0000001a }, 91             { 0x15, 2, 0, 0x65e2676a }, 92             { 0x20, 0, 0, 0x00000026 }, 93             { 0x15, 0, 1, 0x65e2676a }, 94             { 0x6, 0, 0, 0x0000ffff }, 95             { 0x6, 0, 0, 0x00000000 } 96         }; 97  98     struct sock_fprog filter; 99     filter.len = sizeof(bpf_code)/sizeof(bpf_code[0]);100     filter.filter = bpf_code;101 102     sighandle.sa_flags = 0;103     sighandle.sa_handler = sig_handler;104     sigemptyset(&sighandle.sa_mask);105     //sigaddset(&sighandle.sa_mask, SIGTERM);106     //sigaddset(&sighandle.sa_mask, SIGINT);107     //sigaddset(&sighandle.sa_mask, SIGQUIT);108     sigaction(SIGTERM, &sighandle, NULL);109     sigaction(SIGINT, &sighandle, NULL);110     sigaction(SIGQUIT, &sighandle, NULL);111 112     // AF_PACKET allows application to read pecket from and write packet to network device113     // SOCK_DGRAM the packet exclude ethernet header114     // SOCK_RAW raw data from the device including ethernet header115     // ETH_P_IP all IP packets 116     if((sock = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_IP))) == -1) {117         perror("socket");118         exit(1);119     }120 121     // set NIC to promiscous mode, so we can recieve all packets of the network122     strncpy(ethreq.ifr_name, "eth1", IFNAMSIZ);123     if(ioctl(sock, SIOCGIFFLAGS, &ethreq) == -1) {124         perror("ioctl");125         close(sock);126         exit(1);127     }128 129     ethreq.ifr_flags |= IFF_PROMISC;130     if(ioctl(sock, SIOCSIFFLAGS, &ethreq) == -1) {131         perror("ioctl");132         close(sock);133         exit(1);134     }135 136 #if 1137     // attach the bpf filter138     if(setsockopt(sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) == -1) {139         perror("setsockopt");140         close(sock);141         exit(1);142     }143 #endif144 145     while(1) {146         n = recvfrom(sock, buf, sizeof(buf), 0, NULL, NULL);147         if(n < (ETH_HDR_LEN+IP_HDR_LEN+UDP_HDR_LEN)) {148             printf("invalid packet\n");149             continue;150         }151 152         printf("%d bytes recieved\n", n);153 154         ethhead = buf;155         printf("Ethernet: MAC[%02X:%02X:%02X:%02X:%02X:%02X]", ethhead[0], ethhead[1], ethhead[2],156                 ethhead[3], ethhead[4], ethhead[5]);157         printf("->[%02X:%02X:%02X:%02X:%02X:%02X]", ethhead[6], ethhead[7], ethhead[8],158                 ethhead[9], ethhead[10], ethhead[11]);159         printf(" type[%04x]\n", (ntohs(ethhead[12]|ethhead[13]<<8)));160 161         iphead = ethhead + ETH_HDR_LEN;162         // header length as 32-bit163         printf("IP: Version: %d HeaderLen: %d[%d]", (*iphead>>4), (*iphead & 0x0f), (*iphead & 0x0f)*4);164         printf(" TotalLen %d", (iphead[2]<<8|iphead[3]));165         printf(" IP [%d.%d.%d.%d]", iphead[12], iphead[13], iphead[14], iphead[15]);166         printf("->[%d.%d.%d.%d]", iphead[16], iphead[17], iphead[18], iphead[19]);167         printf(" %d", iphead[9]);168 169         if(iphead[9] == IPPROTO_TCP)170             printf("[TCP]");171         else if(iphead[9] == IPPROTO_UDP)172             printf("[UDP]");173         else if(iphead[9] == IPPROTO_ICMP)174             printf("[ICMP]");175         else if(iphead[9] == IPPROTO_IGMP)176             printf("[IGMP]");177         else if(iphead[9] == IPPROTO_IGMP)178             printf("[IGMP]");179         else180             printf("[OTHERS]");181 182         printf(" PORT [%d]->[%d]\n", (iphead[20]<<8|iphead[21]), (iphead[22]<<8|iphead[23]));183     }184     close(sock);185     exit(0);186 }

（2）第二种方法：

#include <stdio.h>#include <sys/types.h>          /* See NOTES */#include <sys/socket.h>#include <sys/mman.h>#include <poll.h>#include <linux/types.h>#include <unistd.h>#include <arpa/inet.h>#include <linux/if_packet.h>#include <linux/if_ether.h>#include <linux/filter.h>#include <net/ethernet.h>#define ETH_HDR_LEN 14void CallBackPacket(char *data){    unsigned char *ethhead;    unsigned char *iphead;    printf("Recv A Packet.\n");    ethhead = data;    printf("Ethernet: MAC[%02X:%02X:%02X:%02X:%02X:%02X]", ethhead[0], ethhead[1], ethhead[2],            ethhead[3], ethhead[4], ethhead[5]);    printf("->[%02X:%02X:%02X:%02X:%02X:%02X]", ethhead[6], ethhead[7], ethhead[8],            ethhead[9], ethhead[10], ethhead[11]);    printf(" type[%04x]\n", (ntohs(ethhead[12]|ethhead[13]<<8)));    iphead = ethhead + ETH_HDR_LEN;    // header length as 32-bit    printf("IP: Version: %d HeaderLen: %d[%d]", (*iphead>>4), (*iphead & 0x0f), (*iphead & 0x0f)*4);    printf(" TotalLen %d", (iphead[2]<<8|iphead[3]));    printf(" IP [%d.%d.%d.%d]", iphead[12], iphead[13], iphead[14], iphead[15]);    printf("->[%d.%d.%d.%d]", iphead[16], iphead[17], iphead[18], iphead[19]);    printf(" %d", iphead[9]);}int main(){    int fd = 0, ret = 0;    char *buff = NULL;    fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));    //可以使用ARP进行一下测试    //fd = socket(PF_PACKET, SOCK_DGRAM, htons (ETH_P_ARP));    if(fd<0)    {        perror("socket");        goto failed_2;    }    //PACKET_VERSION和SO_BINDTODEVICE可以省略#if 1    const int tpacket_version = TPACKET_V1;    /* set tpacket hdr version. */    ret = setsockopt(fd, SOL_PACKET, PACKET_VERSION, &tpacket_version, sizeof (int));    if(ret<0)    {        perror("setsockopt");        goto failed_2;    }    //#define NETDEV_NAME "wlan0"#define NETDEV_NAME "eth1"    /* bind to device. */    ret = setsockopt(fd, SOL_SOCKET, SO_BINDTODEVICE, NETDEV_NAME, sizeof (NETDEV_NAME));    if(ret<0)    {        perror("setsockopt");        goto failed_2;    }#endif    struct tpacket_req req;#define PER_PACKET_SIZE 2048    const int BUFFER_SIZE = 1024*1024*16; //16MB的缓冲区    req.tp_block_size = 4096;    req.tp_block_nr = BUFFER_SIZE/req.tp_block_size;    req.tp_frame_size = PER_PACKET_SIZE;    req.tp_frame_nr = BUFFER_SIZE/req.tp_frame_size;    ret = setsockopt(fd, SOL_PACKET, PACKET_RX_RING, (void *)&req, sizeof(req));    if(ret<0)    {        perror("setsockopt");        goto failed_2;    }#if 1    struct sock_filter bpf_code[] = {        { 0x28, 0, 0, 0x0000000c },        { 0x15, 0, 5, 0x00000800 },        { 0x20, 0, 0, 0x0000001a },        { 0x15, 2, 0, 0x65e2676a },        { 0x20, 0, 0, 0x00000026 },        { 0x15, 0, 1, 0x65e2676a },        { 0x6, 0, 0, 0x0000ffff },        { 0x6, 0, 0, 0x00000000 }    };    struct sock_fprog filter;    filter.len = sizeof(bpf_code)/sizeof(bpf_code[0]);    filter.filter = bpf_code;    // attach the bpf filter    if(setsockopt(fd, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) == -1) {        perror("setsockopt");        close(fd);        goto failed_2;    }#endif    buff = (char *)mmap(0, BUFFER_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0);    if(buff == MAP_FAILED)    {        perror("mmap");        goto failed_2;    }    int nIndex=0, i=0;    while(1)    {        //这里在poll前先检查是否已经有报文被捕获了        struct tpacket_hdr* pHead = (struct tpacket_hdr*)(buff+ nIndex*PER_PACKET_SIZE);        //如果frame的状态已经为TP_STATUS_USER了，说明已经在poll前已经有一个数据包被捕获了，如果poll后不再有数据包被捕获，那么这个报文不会被处理，这就是所谓的竞争情况。        if(pHead->tp_status == TP_STATUS_USER)            goto process_packet;        //poll检测报文捕获        struct pollfd pfd;        pfd.fd = fd;        //pfd.events = POLLIN|POLLRDNORM|POLLERR;        pfd.events = POLLIN;        pfd.revents = 0;        ret = poll(&pfd, 1, -1);        if(ret<0)        {            perror("poll");            goto failed_1;        }process_packet:        //尽力的去处理环形缓冲区中的数据frame，直到没有数据frame了        for(i=0; i < req.tp_frame_nr; i++)        {            struct tpacket_hdr* pHead = (struct tpacket_hdr*)(buff+ nIndex*PER_PACKET_SIZE);            //XXX: 由于frame都在一个环形缓冲区中，因此如果下一个frame中没有数据了，后面的frame也就没有frame了            if(pHead->tp_status == TP_STATUS_KERNEL)                break;            //处理数据frame            CallBackPacket((char*)pHead+pHead->tp_net);            //重新设置frame的状态为TP_STATUS_KERNEL            pHead->tp_len = 0;            pHead->tp_status = TP_STATUS_KERNEL;            //更新环形缓冲区的索引，指向下一个frame            nIndex++;            nIndex %= req.tp_frame_nr;        }    }success:    close(fd);    munmap(buff, BUFFER_SIZE);    return 0;failed_1:    munmap(buff, BUFFER_SIZE);failed_2:    close(fd);    return -1;}

3、测试结果：

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执行main程序，使用curl http://www.qq.com

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suricata抓包方式之一 AF_PACKET


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