3f79300e37
In arpping.h, fix structure alignment of "struct arpMsg". GCC can insert padding in the structure which causes udhcpd to send an invalid ARP packet on the network. It will then not receive a valid reply, which can cause it to assign an IP address that's already in use on the network. (With kernels before 2.4.20, the "struct ethhdr" in linux/if_ether.h wasn't marked as packed. This is also an issue if your toolchain was built with a pre-2.4.20 kernel).
107 lines
2.8 KiB
C
107 lines
2.8 KiB
C
/*
|
|
* arpping.c
|
|
*
|
|
* Mostly stolen from: dhcpcd - DHCP client daemon
|
|
* by Yoichi Hariguchi <yoichi@fore.com>
|
|
*/
|
|
|
|
#include <sys/time.h>
|
|
#include <time.h>
|
|
#include <sys/socket.h>
|
|
#include <netinet/if_ether.h>
|
|
#include <net/if_arp.h>
|
|
#include <netinet/in.h>
|
|
#include <string.h>
|
|
#include <unistd.h>
|
|
#include <errno.h>
|
|
|
|
#include "dhcpd.h"
|
|
#include "arpping.h"
|
|
#include "common.h"
|
|
|
|
/* args: yiaddr - what IP to ping
|
|
* ip - our ip
|
|
* mac - our arp address
|
|
* interface - interface to use
|
|
* retn: 1 addr free
|
|
* 0 addr used
|
|
* -1 error
|
|
*/
|
|
|
|
/* FIXME: match response against chaddr */
|
|
int arpping(uint32_t yiaddr, uint32_t ip, uint8_t *mac, char *interface)
|
|
{
|
|
|
|
int timeout = 2;
|
|
int optval = 1;
|
|
int s; /* socket */
|
|
int rv = 1; /* return value */
|
|
struct sockaddr addr; /* for interface name */
|
|
struct arpMsg arp;
|
|
fd_set fdset;
|
|
struct timeval tm;
|
|
time_t prevTime;
|
|
|
|
|
|
if ((s = socket (PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP))) == -1) {
|
|
#ifdef IN_BUSYBOX
|
|
LOG(LOG_ERR, bb_msg_can_not_create_raw_socket);
|
|
#else
|
|
LOG(LOG_ERR, "Could not open raw socket");
|
|
#endif
|
|
return -1;
|
|
}
|
|
|
|
if (setsockopt(s, SOL_SOCKET, SO_BROADCAST, &optval, sizeof(optval)) == -1) {
|
|
LOG(LOG_ERR, "Could not setsocketopt on raw socket");
|
|
close(s);
|
|
return -1;
|
|
}
|
|
|
|
/* send arp request */
|
|
memset(&arp, 0, sizeof(arp));
|
|
memcpy(arp.h_dest, MAC_BCAST_ADDR, 6); /* MAC DA */
|
|
memcpy(arp.h_source, mac, 6); /* MAC SA */
|
|
arp.h_proto = htons(ETH_P_ARP); /* protocol type (Ethernet) */
|
|
arp.htype = htons(ARPHRD_ETHER); /* hardware type */
|
|
arp.ptype = htons(ETH_P_IP); /* protocol type (ARP message) */
|
|
arp.hlen = 6; /* hardware address length */
|
|
arp.plen = 4; /* protocol address length */
|
|
arp.operation = htons(ARPOP_REQUEST); /* ARP op code */
|
|
memcpy(arp.sInaddr, &ip, sizeof(ip)); /* source IP address */
|
|
memcpy(arp.sHaddr, mac, 6); /* source hardware address */
|
|
memcpy(arp.tInaddr, &yiaddr, sizeof(yiaddr)); /* target IP address */
|
|
|
|
memset(&addr, 0, sizeof(addr));
|
|
strcpy(addr.sa_data, interface);
|
|
if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0)
|
|
rv = 0;
|
|
|
|
/* wait arp reply, and check it */
|
|
tm.tv_usec = 0;
|
|
time(&prevTime);
|
|
while (timeout > 0) {
|
|
FD_ZERO(&fdset);
|
|
FD_SET(s, &fdset);
|
|
tm.tv_sec = timeout;
|
|
if (select(s + 1, &fdset, (fd_set *) NULL, (fd_set *) NULL, &tm) < 0) {
|
|
DEBUG(LOG_ERR, "Error on ARPING request: %m");
|
|
if (errno != EINTR) rv = 0;
|
|
} else if (FD_ISSET(s, &fdset)) {
|
|
if (recv(s, &arp, sizeof(arp), 0) < 0 ) rv = 0;
|
|
if (arp.operation == htons(ARPOP_REPLY) &&
|
|
bcmp(arp.tHaddr, mac, 6) == 0 &&
|
|
*((uint32_t *) arp.sInaddr) == yiaddr) {
|
|
DEBUG(LOG_INFO, "Valid arp reply receved for this address");
|
|
rv = 0;
|
|
break;
|
|
}
|
|
}
|
|
timeout -= time(NULL) - prevTime;
|
|
time(&prevTime);
|
|
}
|
|
close(s);
|
|
DEBUG(LOG_INFO, "%salid arp replies for this address", rv ? "No v" : "V");
|
|
return rv;
|
|
}
|