fireflyc · December 25, 2016 12:43 · Dec 25, 2016 · Dec 25, 2016
diff --git a/arp_joke → arp_joke.c b/arp_joke → arp_joke.c
diff --git a/arp_joke b/arp_joke
@@ -0,0 +1,150 @@
+#include <pcap.h>
+#include <stdlib.h>
+#include <libnet.h>
+
+#define log_error(...) fprintf(stderr, __VA_ARGS__)
+#define log_info(...) fprintf(stdout, __VA_ARGS__)
+#define FALSE (0==1)
+#define TRUE (1==1)
+
+typedef struct arp_joke {
+    char *ifi;
+
+} arp_joke_t;
+
+typedef struct arphdr {
+    u_int16_t htype;    /* Hardware Type           */
+    u_int16_t ptype;    /* Protocol Type           */
+    u_char hlen;        /* Hardware Address Length */
+    u_char plen;        /* Protocol Address Length */
+    u_int16_t oper;     /* Operation Code          */
+    u_char sha[6];      /* Sender hardware address */
+    u_char spa[4];      /* Sender IP address       */
+    u_char tha[6];      /* Target hardware address */
+    u_char tpa[4];      /* Target IP address       */
+} arphdr_t;
+
+int response_arp(char *device, struct libnet_ethernet_hdr *eth_hdr, arphdr_t *arp_hdr, char *errbuf) {
+    libnet_t *net = libnet_init(LIBNET_LINK, device, errbuf);
+    if (net == NULL) {
+        return FALSE;
+    }
+    struct libnet_ether_addr *mac_addr = libnet_get_hwaddr(net);
+    if (memcmp(mac_addr->ether_addr_octet, arp_hdr->tha, 6) ||
+        memcmp(mac_addr->ether_addr_octet, arp_hdr->sha, 6)) {
+        return FALSE;
+    }
+    libnet_ptag_t t = libnet_autobuild_arp(
+            ARPOP_REPLY,                           /* operation type */
+            (const uint8_t *) mac_addr,                              /* sender hardware addr */
+            (uint8_t *) &arp_hdr->tpa,       /* sender protocol addr */
+            eth_hdr->ether_shost,                  /* target hardware addr */
+            (uint8_t *) &arp_hdr->spa,       /* target protocol addr */
+            net);                                     /* libnet id */
+
+    if (t == -1) {
+        snprintf(errbuf, BUFSIZ, "Can't build ARP header: %s\n", libnet_geterror(net));
+        libnet_destroy(net);
+        return EXIT_FAILURE;
+    }
+    t = libnet_build_ethernet(
+            arp_hdr->sha,                           /* ethernet destination */
+            (const uint8_t *) mac_addr,
+            ETHERTYPE_ARP,                          /* protocol type */
+            NULL,
+            0,
+            net, /* libnet handle */
+            0);
+    if (t == -1) {
+        snprintf(errbuf, BUFSIZ, "Can't build ethernet header: %s\n", libnet_geterror(net));
+        libnet_destroy(net);
+        return EXIT_FAILURE;
+    }
+    int write_size = libnet_write(net);
+    if (write_size == -1) {
+        snprintf(errbuf, BUFSIZ, "Writer error %s", libnet_geterror(net));
+        libnet_destroy(net);
+        return EXIT_FAILURE;
+    }
+    libnet_destroy(net);
+    return EXIT_SUCCESS;
+}
+
+void on_packet(u_char *arg, const struct pcap_pkthdr *pkthdr, const u_char *packet) {
+    arp_joke_t *arp_joke = (arp_joke_t *) arg;
+    char errbuf[BUFSIZ];
+
+    struct libnet_ethernet_hdr *ether_hdr = (struct libnet_ethernet_hdr *) packet;
+    if (ntohs(ether_hdr->ether_type) == ETHERTYPE_ARP) {
+        arphdr_t *arp_hdr = (arphdr_t *) (packet + LIBNET_ETH_H);
+        if (ntohs(arp_hdr->oper) == ARPOP_REQUEST) {
+            log_info("received arp query\n");
+            //收到ARP
+            response_arp(arp_joke->ifi, ether_hdr, arp_hdr, errbuf);
+            log_info("send response\n");
+        }
+        return;
+    }
+}
+
+pcap_t *init_pcap(const char *dev, const char *filter_exp, char *errbuf) {
+    bpf_u_int32 netp;
+    bpf_u_int32 maskp;
+    if (pcap_lookupnet(dev, &netp, &maskp, errbuf) == -1) {
+        snprintf(errbuf, BUFSIZ, "lookup %s failed", dev);
+        return NULL;
+    }
+    pcap_t *pcap = pcap_open_live(dev, 1500, 1, 0, errbuf);
+    if (pcap == NULL) {
+        return NULL;
+    }
+    if (filter_exp != NULL) {
+        struct bpf_program fp;
+        if (pcap_compile(pcap, &fp, filter_exp, 1, netp) == -1) {
+            snprintf(errbuf, BUFSIZ, "Compile filter expression failed %s cause: %s", filter_exp,
+                     pcap_geterr(pcap));
+            pcap_close(pcap);
+            return NULL;
+        }
+        if (pcap_setfilter(pcap, &fp) == -1) {
+            snprintf(errbuf, BUFSIZ, "Install filter failed %s", pcap_geterr(pcap));
+            pcap_close(pcap);
+            return NULL;
+        }
+    }
+    return pcap;
+}
+
+pcap_t *pcap = NULL;
+arp_joke_t *arp_joke = NULL;
+
+void on_exit(int sig) {
+    if (arp_joke != NULL) {
+        free(arp_joke);
+    }
+    if (pcap != NULL) {
+        pcap_close(pcap);
+    }
+}
+
+int main(int argc, char **argv) {
+    if (argc != 2) {
+        printf("usage arp_joke <network card>\n");
+        return EXIT_FAILURE;
+    }
+    char errbuf[BUFSIZ];
+    pcap = init_pcap(argv[1], NULL, errbuf);
+    if (pcap == NULL) {
+        log_error("init pcap failed %s\n", errbuf);
+        return EXIT_FAILURE;
+    }
+    //获取mac地址
+    log_info("Start Success\n");
+    arp_joke = (arp_joke_t *) malloc(sizeof(arp_joke_t));
+    arp_joke->ifi = argv[1];
+
+    signal(SIGINT, on_exit);
+    pcap_loop(pcap, -1, on_packet, (u_char *) arp_joke);
+
+    return 0;
+}
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