diff --git a/main.c b/main.c
index 9200fba..a6c3ff4 100644
--- a/main.c
+++ b/main.c
@@ -8,11 +8,10 @@
 #include <netinet/in.h>
 #include <net/ethernet.h>
 #include <linux/if_packet.h>
-#include <linux/if_arp.h>
 
-typedef uint8_t mac_t[6];
+#define MTU 1500
 
-void parse_mac(const char* str, mac_t mac) {
+void parse_mac(const char* str, uint8_t* mac) {
     char* s = strdup(str);
     char* octet = strtok(s, ":");
     int i = 0;
@@ -26,27 +25,79 @@ void parse_mac(const char* str, mac_t mac) {
     free(s);
 }
 
-int main(int argc, char** argv) {
-    // ifname hostMAC gatewayMAC targetMAC
+void print_mac(uint8_t* mac) {
+    printf("%02x:%02x:%02x:%02x:%02x:%02x\n",
+        mac[0], mac[1], mac[2], mac[3], mac[4], mac[5]);
+}
 
-    mac_t host, gateway, target;
-    parse_mac(argv[2], host);
-    parse_mac(argv[3], gateway);
-    parse_mac(argv[4], target);
+struct linkinterface {
+    char* if_name;
+    socklen_t if_len;
 
-    int raw = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
-    if (raw < 0) {
-        perror("socket");
+    uint8_t host[ETH_ALEN];
+    uint8_t gateway[ETH_ALEN];
+
+    int fd; // raw socket
+};
+
+struct linkinterface* link_parse(const char* if_name, const char* host, const char* gateway) {
+    struct linkinterface* link = (struct linkinterface*)malloc(sizeof(struct linkinterface));
+    link->if_name = strdup(if_name);
+    link->if_len = strlen(link->if_name);
+
+    parse_mac(host, link->host);
+    parse_mac(gateway, link->gateway);
+}
+
+int link_open(struct linkinterface* link) {
+    link->fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_ALL));
+    if (link->fd < 0) {
         return 1;
     }
-    setsockopt(raw, SOL_SOCKET, SO_BINDTODEVICE, argv[1], strlen(argv[1]));
+    setsockopt(link->fd, SOL_SOCKET, SO_BINDTODEVICE, link->if_name, link->if_name);
+}
+
+void link_free(struct linkinterface* link) {
+    close(link->fd);
+    free(link->if_name);
+    free(link);
+}
+
+typedef struct arp_packet_s {
+    struct ether_header ether;
+    
+    uint16_t hrd;           // Hardware address space (e.g., Ethernet, Packet Radio Net.)
+    uint16_t pro;           // Protocol address space.  For Ethernet hardware, this is from the set of type fields ether_typ$<protocol>.
+    uint8_t hln;            // byte length of each hardware address
+    uint8_t pln;            // byte length of each protocol address
+    uint16_t op;            // opcode (ares_op$REQUEST | ares_op$REPLY)
+    uint8_t sha[ETH_ALEN];  // Hardware address of sender of this packet
+    uint8_t spa[4];         // Protocol address of sender of this packet
+    uint8_t tha[ETH_ALEN];  // Hardware address of sender of this packet
+    uint8_t tpa[4];         // Protocol address of sender of this packet
+} __attribute__((packed)) arp_packet_t;
+
+#define ARP_OP_REQUEST      0x01
+#define ARP_OP_REPLY        0x02
+
+int main(int argc, char** argv) {
+    // ifname hostMAC gatewayMAC targetMAC
+    struct linkinterface* link = link_parse(argv[1], argv[2], argv[3]);
+
+    uint8_t target[ETH_ALEN];
+    parse_mac(argv[4], target);
+
+    link_open(link);
 
     // test receive
     while (1) {
-        uint8_t packet[1500];
-        ssize_t rd = recv(raw, packet, 1500, 0);
-        printf("%lu\n", rd);
+        uint8_t packet[MTU];
+        ssize_t rd = recv(link->fd, packet, MTU, 0);
+        
+        struct ether_header *ether = (struct ether_header *)&packet[0];
+        print_mac(ether->ether_shost);
     }
 
+    link_free(link);
     return 0;
 }
\ No newline at end of file