117 lines
3.6 KiB
C
117 lines
3.6 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* arpping.c
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*
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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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#include <netinet/if_ether.h>
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#include <net/if_arp.h>
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#include "common.h"
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#include "dhcpd.h"
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struct arpMsg {
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/* Ethernet header */
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uint8_t h_dest[6]; /* 00 destination ether addr */
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uint8_t h_source[6]; /* 06 source ether addr */
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uint16_t h_proto; /* 0c packet type ID field */
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/* ARP packet */
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uint16_t htype; /* 0e hardware type (must be ARPHRD_ETHER) */
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uint16_t ptype; /* 10 protocol type (must be ETH_P_IP) */
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uint8_t hlen; /* 12 hardware address length (must be 6) */
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uint8_t plen; /* 13 protocol address length (must be 4) */
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uint16_t operation; /* 14 ARP opcode */
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uint8_t sHaddr[6]; /* 16 sender's hardware address */
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uint8_t sInaddr[4]; /* 1c sender's IP address */
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uint8_t tHaddr[6]; /* 20 target's hardware address */
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uint8_t tInaddr[4]; /* 26 target's IP address */
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uint8_t pad[18]; /* 2a pad for min. ethernet payload (60 bytes) */
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} PACKED;
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enum {
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ARP_MSG_SIZE = 0x2a
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};
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/* Returns 1 if no reply received */
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int arpping(uint32_t test_ip, uint32_t from_ip, uint8_t *from_mac, const char *interface)
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{
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int timeout_ms;
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struct pollfd pfd[1];
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#define s (pfd[0].fd) /* socket */
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int rv = 1; /* "no reply received" yet */
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struct sockaddr addr; /* for interface name */
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struct arpMsg arp;
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s = socket(PF_PACKET, SOCK_PACKET, htons(ETH_P_ARP));
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if (s == -1) {
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bb_perror_msg(bb_msg_can_not_create_raw_socket);
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return -1;
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}
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if (setsockopt_broadcast(s) == -1) {
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bb_perror_msg("cannot enable bcast on raw socket");
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goto ret;
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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, from_mac, 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.sHaddr, from_mac, 6); /* source hardware address */
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memcpy(arp.sInaddr, &from_ip, sizeof(from_ip)); /* source IP address */
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/* tHaddr is zero-fiiled */ /* target hardware address */
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memcpy(arp.tInaddr, &test_ip, sizeof(test_ip)); /* target IP address */
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memset(&addr, 0, sizeof(addr));
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safe_strncpy(addr.sa_data, interface, sizeof(addr.sa_data));
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if (sendto(s, &arp, sizeof(arp), 0, &addr, sizeof(addr)) < 0) {
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// TODO: error message? caller didn't expect us to fail,
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// just returning 1 "no reply received" misleads it.
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goto ret;
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}
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/* wait for arp reply, and check it */
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timeout_ms = 2000;
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do {
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int r;
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unsigned prevTime = monotonic_us();
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pfd[0].events = POLLIN;
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r = safe_poll(pfd, 1, timeout_ms);
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if (r < 0)
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break;
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if (r) {
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r = read(s, &arp, sizeof(arp));
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if (r < 0)
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break;
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if (r >= ARP_MSG_SIZE
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&& arp.operation == htons(ARPOP_REPLY)
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/* don't check it: Linux doesn't return proper tHaddr (fixed in 2.6.24?) */
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/* && memcmp(arp.tHaddr, from_mac, 6) == 0 */
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&& *((uint32_t *) arp.sInaddr) == test_ip
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) {
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rv = 0;
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break;
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}
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}
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timeout_ms -= ((unsigned)monotonic_us() - prevTime) / 1000;
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} while (timeout_ms > 0);
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ret:
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close(s);
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DEBUG("%srp reply received for this address", rv ? "No a" : "A");
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return rv;
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}
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