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copied!<p>Apple's implementation of <code>arp</code> is open source. Take a look at <a href="http://www.opensource.apple.com/source/bootp/bootp-133.8/bootplib/arp.c" rel="nofollow noreferrer">the file</a> for an idea of its implementation... it's not terribly convoluted. It is pure ANSI C, though.</p> <p>You should be able to simply copy-paste the majority of the functionality... and instead of printing the results, just store the raw address.</p> <p><strong>Edit:</strong> Here's a stripped down version of the source that just runs the equivalent of <code>arp -a</code>. This should compile without any special directives.</p> <pre><code>/* * Copyright (c) 1999 Apple Computer, Inc. All rights reserved. * * @APPLE_LICENSE_HEADER_START@ * * This file contains Original Code and/or Modifications of Original Code * as defined in and that are subject to the Apple Public Source License * Version 2.0 (the 'License'). You may not use this file except in * compliance with the License. Please obtain a copy of the License at * http://www.opensource.apple.com/apsl/ and read it before using this * file. * * The Original Code and all software distributed under the License are * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES, * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY, * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT. * Please see the License for the specific language governing rights and * limitations under the License. * * @APPLE_LICENSE_HEADER_END@ */ #include <sys/param.h> #include <sys/file.h> #include <sys/socket.h> #include <sys/sysctl.h> #include <net/if.h> #include <net/if_dl.h> #include <net/if_types.h> #include <net/route.h> #include <netinet/in.h> #include <netinet/if_ether.h> #include <arpa/inet.h> #include <err.h> #include <errno.h> #include <netdb.h> #include <nlist.h> #include <paths.h> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> static int nflag; void ether_print(cp) u_char *cp; { printf("%x:%x:%x:%x:%x:%x", cp[0], cp[1], cp[2], cp[3], cp[4], cp[5]); } /* * Dump the entire arp table */ int dump(addr) u_long addr; { int mib[6]; size_t needed; char *host, *lim, *buf, *next; struct rt_msghdr *rtm; struct sockaddr_inarp *sin; struct sockaddr_dl *sdl; extern int h_errno; struct hostent *hp; int found_entry = 0; mib[0] = CTL_NET; mib[1] = PF_ROUTE; mib[2] = 0; mib[3] = AF_INET; mib[4] = NET_RT_FLAGS; mib[5] = RTF_LLINFO; if (sysctl(mib, 6, NULL, &needed, NULL, 0) < 0) err(1, "route-sysctl-estimate"); if ((buf = malloc(needed)) == NULL) err(1, "malloc"); if (sysctl(mib, 6, buf, &needed, NULL, 0) < 0) err(1, "actual retrieval of routing table"); lim = buf + needed; for (next = buf; next < lim; next += rtm->rtm_msglen) { rtm = (struct rt_msghdr *)next; sin = (struct sockaddr_inarp *)(rtm + 1); sdl = (struct sockaddr_dl *)(sin + 1); if (addr) { if (addr != sin->sin_addr.s_addr) continue; found_entry = 1; } if (nflag == 0) hp = gethostbyaddr((caddr_t)&(sin->sin_addr), sizeof sin->sin_addr, AF_INET); else hp = 0; if (hp) host = hp->h_name; else { host = "?"; if (h_errno == TRY_AGAIN) nflag = 1; } printf("%s (%s) at ", host, inet_ntoa(sin->sin_addr)); if (sdl->sdl_alen) ether_print((u_char *)LLADDR(sdl)); else printf("(incomplete)"); if (rtm->rtm_rmx.rmx_expire == 0) printf(" permanent"); if (sin->sin_other & SIN_PROXY) printf(" published (proxy only)"); if (rtm->rtm_addrs & RTA_NETMASK) { sin = (struct sockaddr_inarp *) (sdl->sdl_len + (char *)sdl); if (sin->sin_addr.s_addr == 0xffffffff) printf(" published"); if (sin->sin_len != 8) printf("(weird)"); } printf("\n"); } return (found_entry); } int main (int argc, char const *argv[]) { dump(0); return 0; } </code></pre>

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