Rewrite the ARP ping code to properly use modern interfaces. In detail:
- Use AF_PACKET and SOCK_RAW rather than the decade-deprecated SOCK_PACKET interface. - Separate out socket creation code into a subfunction. - Use C99 initializers for packet and address structures. - Cosmetic cleanups.
This commit is contained in:
Nicholas J. Kain
parent
8f5eb7e921
commit
c37d815754
89
ndhc/arp.c
89
ndhc/arp.c
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@ -3,10 +3,6 @@
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*
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* Copyright 2010-2011 Nicholas J. Kain <njkain@gmail.com>
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*
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* Originally derived from busybox's udhcpc variant, which in turn was...
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* Mostly stolen from: dhcpcd - DHCP client daemon
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* by Yoichi Hariguchi <yoichi@fore.com>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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@ -30,6 +26,7 @@
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <sys/time.h>
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#include <linux/if_packet.h>
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#include <fcntl.h>
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#include <errno.h>
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#include "arp.h"
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@ -38,7 +35,6 @@
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#include "ifchange.h"
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#include "leasefile.h"
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#include "log.h"
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#include "strl.h"
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#include "io.h"
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#define ARP_MSG_SIZE 0x2a
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@ -49,33 +45,18 @@ static int arpreply_offset;
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static struct dhcpMessage arp_dhcp_packet;
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static int arp_packet_num;
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static int arp_close_fd(struct client_state_t *cs)
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static int arp_open_fd(struct client_state_t *cs)
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{
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if (cs->arpFd != -1) {
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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return 1;
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}
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return 0;
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}
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/* Returns 0 on success, -1 on failure. */
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static int arpping(struct client_state_t *cs, uint32_t test_ip)
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{
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int opt = 1;
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struct sockaddr addr; /* for interface name */
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struct arpMsg arp;
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if (cs->arpFd == -1) {
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int arpfd = socket(AF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
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int arpfd = socket(AF_PACKET, SOCK_RAW, htons(ETH_P_ARP));
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if (arpfd == -1) {
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log_error("arp: failed to create socket: %s", strerror(errno));
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return -1;
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}
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int opt = 1;
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if (setsockopt(arpfd, SOL_SOCKET, SO_BROADCAST,
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&opt, sizeof opt) == -1) {
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&opt, sizeof opt) == -1) {
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log_error("arp: failed to set broadcast: %s", strerror(errno));
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close(arpfd);
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return -1;
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@ -88,26 +69,48 @@ static int arpping(struct client_state_t *cs, uint32_t test_ip)
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cs->arpFd = arpfd;
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epoll_add(cs, arpfd);
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}
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return 0;
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}
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/* send arp request */
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memset(&arp, 0, sizeof arp);
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memset(arp.h_dest, 0xff, 6); /* MAC DA */
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memcpy(arp.h_source, client_config.arp, 6); /* MAC SA */
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arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
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arp.htype = htons(ARPHRD_ETHER); /* hardware type */
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arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */
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arp.hlen = 6; /* hardware address length */
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arp.plen = 4; /* protocol address length */
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arp.operation = htons(ARPOP_REQUEST); /* ARP op code */
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memcpy(arp.smac, client_config.arp, 6); /* source hardware address */
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memset(arp.sip4, 0, sizeof arp.sip4); /* source IP address */
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/* dmac is zero-filled */ /* target hardware address */
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memcpy(arp.dip4, &test_ip, sizeof test_ip); /* target IP address */
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static int arp_close_fd(struct client_state_t *cs)
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{
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if (cs->arpFd != -1) {
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epoll_del(cs, cs->arpFd);
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close(cs->arpFd);
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cs->arpFd = -1;
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return 1;
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}
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return 0;
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}
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// Returns 0 on success, -1 on failure.
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static int arpping(struct client_state_t *cs, uint32_t test_ip)
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{
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if (arp_open_fd(cs) == -1)
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return -1;
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struct arpMsg arp = {
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.h_proto = htons(ETH_P_ARP),
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.htype = htons(ARPHRD_ETHER),
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.ptype = htons(ETH_P_IP),
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.hlen = 6,
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.plen = 4,
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.operation = htons(ARPOP_REQUEST),
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};
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memset(arp.h_dest, 0xff, 6);
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memcpy(arp.h_source, client_config.arp, 6);
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memcpy(arp.smac, client_config.arp, 6);
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memcpy(arp.dip4, &test_ip, sizeof test_ip);
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struct sockaddr_ll addr = {
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.sll_family = AF_PACKET,
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.sll_ifindex = client_config.ifindex,
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.sll_halen = 6,
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};
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memcpy(addr.sll_addr, client_config.arp, 6);
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memset(&addr, 0, sizeof addr);
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strlcpy(addr.sa_data, client_config.interface, sizeof addr.sa_data);
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if (safe_sendto(cs->arpFd, (const char *)&arp, sizeof arp,
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0, &addr, sizeof addr) < 0) {
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0, (struct sockaddr *)&addr, sizeof addr) < 0) {
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log_error("arp: sendto failed: %s", strerror(errno));
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arp_close_fd(cs);
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return -1;
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@ -195,10 +198,8 @@ void arp_success(struct client_state_t *cs)
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arp_close_fd(cs);
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/* enter bound state */
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cs->t1 = cs->lease >> 1;
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/* little fixed point for n * .875 */
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cs->t2 = (cs->lease * 0x7) >> 3;
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cs->t2 = (cs->lease * 0x7) >> 3; // T2 = lease * 0.875
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cs->timeout = cs->t1 * 1000;
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cs->leaseStartTime = curms();
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