diff --git a/main.c b/main.c
index a650b30..b6ad4bf 100644
--- a/main.c
+++ b/main.c
@@ -3,8 +3,11 @@
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
+#include <unistd.h>
 #include <sys/types.h>
+#include <sys/ioctl.h>
 #include <sys/socket.h>
+#include <net/if.h>
 #include <netinet/in.h>
 #include <net/ethernet.h>
 #include <linux/if_packet.h>
@@ -38,15 +41,17 @@ struct linkinterface {
     uint8_t gateway[ETH_ALEN];
 
     int fd; // raw socket
+    int if_idx;
 };
 
-struct linkinterface* link_parse(const char* if_name, const char* host, const char* gateway) {
+struct linkinterface* link_parse(const char* if_name, 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);
+
+    return link;
 }
 
 int link_open(struct linkinterface* link) {
@@ -54,7 +59,25 @@ int link_open(struct linkinterface* link) {
     if (link->fd < 0) {
         return 1;
     }
-    setsockopt(link->fd, SOL_SOCKET, SO_BINDTODEVICE, link->if_name, link->if_name);
+    setsockopt(link->fd, SOL_SOCKET, SO_BINDTODEVICE, link->if_name, link->if_len);
+
+    // get interface index and MAC
+    struct ifreq netlink;
+    memset(&netlink, '\0', sizeof(netlink));
+    strncpy(netlink.ifr_ifrn.ifrn_name, link->if_name, IFNAMSIZ-1);
+    if (ioctl(link->fd, SIOCGIFINDEX, &netlink) < 0) {
+        return 1;
+    }
+    link->if_idx = netlink.ifr_ifru.ifru_ivalue; // index
+
+    memset(&netlink, '\0', sizeof(netlink));
+    strncpy(netlink.ifr_ifrn.ifrn_name, link->if_name, IFNAMSIZ-1);
+    if (ioctl(link->fd, SIOCGIFHWADDR, &netlink) < 0) {
+        return 1;
+    }
+    memcpy(link->host, netlink.ifr_ifru.ifru_hwaddr.sa_data, ETH_ALEN); // MAC
+
+    return 0;
 }
 
 void link_free(struct linkinterface* link) {
@@ -63,24 +86,7 @@ void link_free(struct linkinterface* link) {
     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 link_send(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t len) {
+ssize_t link_send(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t len) {
     struct ether_header* ether = (struct ether_header*)packet;
     memcpy(ether->ether_shost, link->host, ETH_ALEN);
     memcpy(ether->ether_dhost, link->gateway, ETH_ALEN);
@@ -89,7 +95,7 @@ int link_send(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t
     return send(link->fd, packet, len, 0);
 }
 
-int link_recv(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t len) {
+ssize_t link_recv(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t len) {
     char buffer[MTU];
     uint16_t want_type = htons(type);
     do {
@@ -117,23 +123,59 @@ int link_recv(struct linkinterface* link, uint16_t type, uint8_t* packet, size_t
     // TODO: timeout
 }
 
+#define ARP_HW_ETHER        0x000F
+#define ARP_PT_IP           0x0800
+
+#define ARP_OP_REQUEST      1
+#define ARP_OP_REPLY        2
+
+// Inverse ARP
+#define INARP_OP_REQUEST    8
+#define INART_OP_REPLY      9
+
+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;
+
 int main(int argc, char** argv) {
     // ifname hostMAC gatewayMAC targetMAC
-    struct linkinterface* link = link_parse(argv[1], argv[2], argv[3]);
+    struct linkinterface* link = link_parse(argv[1], argv[2]);
 
     uint8_t target[ETH_ALEN];
-    parse_mac(argv[4], target);
+    parse_mac(argv[3], target);
 
-    link_open(link);
-
-    // test receive
-    while (1) {
-        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);
+    if (link_open(link) < 0) {
+        perror("link_open");
+        return 1;
     }
+    print_mac(link->host);
+
+    uint8_t ip[4] = {192, 168, 100, 3};
+
+    // test arp send
+    arp_packet_t arp;
+    arp.hrd = htons(ARP_HW_ETHER);
+    arp.pro = htons(ARP_PT_IP);
+    arp.hln = htons(ETH_ALEN);
+    arp.pln = htons(4);
+    arp.op = htons(INARP_OP_REQUEST);
+    memcpy(arp.sha, link->host, ETH_ALEN);
+    memcpy(arp.spa, ip, 4);
+    memcpy(arp.tha, target, ETH_ALEN);
+    memset(arp.tpa, '\0', 4);
+
+    ssize_t sent = link_send(link, ETHERTYPE_ARP, (uint8_t*)&arp, sizeof(arp));
+    printf("sent %ld\n", sent);
 
     link_free(link);
     return 0;