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Sourcecode: l2tpns version File versions

arp.c

// L2TPNS: arp

char const *cvs_id_arp = "$Id: arp.c,v 1.5 2004/12/16 08:49:52 bodea Exp $";

#include <string.h>
#include <unistd.h>
#include <net/ethernet.h>
#include <net/if_arp.h>
#include <linux/if_packet.h>

#include "l2tpns.h"

/* Most of this code is based on keepalived:vrrp_arp.c */

struct arp_buf {
      struct ether_header eth;
      struct arphdr arp;

      /* Data bit - variably sized, so not present in |struct arphdr| */
      unsigned char ar_sha[ETH_ALEN];     /* Sender hardware address */
      in_addr_t ar_sip;       /* Sender IP address. */
      unsigned char ar_tha[ETH_ALEN]; /* Target hardware address */
      in_addr_t ar_tip;       /* Target ip */
} __attribute__((packed));

void sendarp(int ifr_idx, const unsigned char* mac, in_addr_t ip)
{
      int fd;
      struct sockaddr_ll sll;
      struct arp_buf buf;

      CSTAT(call_sendarp);
      STAT(arp_sent);

      /* Ethernet */
      memset(buf.eth.ether_dhost, 0xFF, ETH_ALEN);
      memcpy(buf.eth.ether_shost, mac, ETH_ALEN);
      buf.eth.ether_type = htons(ETHERTYPE_ARP);

      /* ARP */
      buf.arp.ar_hrd = htons(ARPHRD_ETHER);
      buf.arp.ar_pro = htons(ETHERTYPE_IP);
      buf.arp.ar_hln = ETH_ALEN;
      buf.arp.ar_pln = 4; //IPPROTO_ADDR_LEN;
      buf.arp.ar_op = htons(ARPOP_REQUEST);

      /* Data */
      memcpy(buf.ar_sha, mac, ETH_ALEN);
      memcpy(&buf.ar_sip, &ip, sizeof(ip));
      memcpy(buf.ar_tha, mac, ETH_ALEN);
      memcpy(&buf.ar_tip, &ip, sizeof(ip));

      /* Now actually send the thing */
      fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_RARP));

      memset(&sll, 0, sizeof(sll));
      sll.sll_family = AF_PACKET;
      strncpy(sll.sll_addr, mac, sizeof(sll.sll_addr) - 1);
      sll.sll_halen = ETH_ALEN;
      sll.sll_ifindex = ifr_idx;

      sendto(fd, &buf, sizeof(buf), 0, (struct sockaddr*)&sll, sizeof(sll));
      close(fd);
}

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