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[l2tpns.git] / arp.c
1 // L2TPNS: arp
2
3 char const *cvs_id_arp = "$Id: arp.c,v 1.5 2004/12/16 08:49:52 bodea Exp $";
4
5 #include <string.h>
6 #include <unistd.h>
7 #include <net/ethernet.h>
8 #include <net/if_arp.h>
9 #include <linux/if_packet.h>
10
11 #include "l2tpns.h"
12
13 /* Most of this code is based on keepalived:vrrp_arp.c */
14
15 struct arp_buf {
16 struct ether_header eth;
17 struct arphdr arp;
18
19 /* Data bit - variably sized, so not present in |struct arphdr| */
20 unsigned char ar_sha[ETH_ALEN]; /* Sender hardware address */
21 in_addr_t ar_sip; /* Sender IP address. */
22 unsigned char ar_tha[ETH_ALEN]; /* Target hardware address */
23 in_addr_t ar_tip; /* Target ip */
24 } __attribute__((packed));
25
26 void sendarp(int ifr_idx, const unsigned char* mac, in_addr_t ip)
27 {
28 int fd;
29 struct sockaddr_ll sll;
30 struct arp_buf buf;
31
32 CSTAT(call_sendarp);
33 STAT(arp_sent);
34
35 /* Ethernet */
36 memset(buf.eth.ether_dhost, 0xFF, ETH_ALEN);
37 memcpy(buf.eth.ether_shost, mac, ETH_ALEN);
38 buf.eth.ether_type = htons(ETHERTYPE_ARP);
39
40 /* ARP */
41 buf.arp.ar_hrd = htons(ARPHRD_ETHER);
42 buf.arp.ar_pro = htons(ETHERTYPE_IP);
43 buf.arp.ar_hln = ETH_ALEN;
44 buf.arp.ar_pln = 4; //IPPROTO_ADDR_LEN;
45 buf.arp.ar_op = htons(ARPOP_REQUEST);
46
47 /* Data */
48 memcpy(buf.ar_sha, mac, ETH_ALEN);
49 memcpy(&buf.ar_sip, &ip, sizeof(ip));
50 memcpy(buf.ar_tha, mac, ETH_ALEN);
51 memcpy(&buf.ar_tip, &ip, sizeof(ip));
52
53 /* Now actually send the thing */
54 fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_RARP));
55
56 memset(&sll, 0, sizeof(sll));
57 sll.sll_family = AF_PACKET;
58 strncpy(sll.sll_addr, mac, sizeof(sll.sll_addr) - 1);
59 sll.sll_halen = ETH_ALEN;
60 sll.sll_ifindex = ifr_idx;
61
62 sendto(fd, &buf, sizeof(buf), 0, (struct sockaddr*)&sll, sizeof(sll));
63 close(fd);
64 }