56 lines
1.5 KiB
C
56 lines
1.5 KiB
C
#include <string.h>
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#include <unistd.h>
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#include <net/ethernet.h>
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#include <net/if_arp.h>
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#include <linux/if_packet.h>
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#include "l2tpns.h"
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/* Most of this code is based on keepalived:vrrp_arp.c */
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struct arp_buf {
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struct ether_header eth;
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struct arphdr arp;
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/* Data bit - variably sized, so not present in |struct arphdr| */
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unsigned char ar_sha[ETH_ALEN]; /* Sender hardware address */
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ipt ar_sip; /* Sender IP address. */
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unsigned char ar_tha[ETH_ALEN]; /* Target hardware address */
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ipt ar_tip; /* Target ip */
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} __attribute__((packed));
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void sendarp(int ifr_idx, const unsigned char* mac, ipt ip)
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{
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int fd;
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struct sockaddr_ll sll;
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struct arp_buf buf;
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/* Ethernet */
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memset(buf.eth.ether_dhost, 0xFF, ETH_ALEN);
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memcpy(buf.eth.ether_shost, mac, ETH_ALEN);
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buf.eth.ether_type = htons(ETHERTYPE_ARP);
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/* ARP */
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buf.arp.ar_hrd = htons(ARPHRD_ETHER);
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buf.arp.ar_pro = htons(ETHERTYPE_IP);
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buf.arp.ar_hln = ETH_ALEN;
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buf.arp.ar_pln = 4; //IPPROTO_ADDR_LEN;
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buf.arp.ar_op = htons(ARPOP_REQUEST);
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/* Data */
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memcpy(buf.ar_sha, mac, ETH_ALEN);
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memcpy(&buf.ar_sip, &ip, sizeof(ip));
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memcpy(buf.ar_tha, mac, ETH_ALEN);
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memcpy(&buf.ar_tip, &ip, sizeof(ip));
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/* Now actually send the thing */
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fd = socket(PF_PACKET, SOCK_RAW, htons(ETH_P_RARP));
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memset(&sll, 0, sizeof(sll));
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sll.sll_family = AF_PACKET;
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strncpy(sll.sll_addr, mac, sizeof(sll.sll_addr)); /* Null-pad */
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sll.sll_halen = ETH_ALEN;
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sll.sll_ifindex = ifr_idx;
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sendto(fd, &buf, sizeof(buf), 0, (struct sockaddr*)&sll, sizeof(sll));
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}
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