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diff --git a/src/resolve.c b/src/resolve.c
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+/*
+// AUTHOR
+// N. Nielsen
+//
+// VERSION
+// 0.2
+//
+// LICENSE
+// This software is in the public domain.
+//
+// The software is provided "as is", without warranty of any kind,
+// express or implied, including but not limited to the warranties
+// of merchantability, fitness for a particular purpose, and
+// noninfringement. In no event shall the author(s) be liable for any
+// claim, damages, or other liability, whether in an action of
+// contract, tort, or otherwise, arising from, out of, or in connection
+// with the software or the use or other dealings in the software.
+//
+// SUPPORT
+// Send bug reports to: <nielsen@memberwebs.com>
+*/
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <stdarg.h>
+#include <unistd.h>
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/sockio.h>
+#include <sys/sysctl.h>
+#include <sys/ioctl.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/nameser.h>
+#include <arpa/inet.h>
+
+#include <resolv.h>
+
+#if HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+/* The main processing functions */
+static void processFile(FILE* fIn, FILE* fOut);
+static void processReverse(const char* address, FILE* fOut);
+static void processNone(const char* address, FILE* fOut);
+static void processAddress(const char* address, FILE* fOut);
+static void processHost(const char* address, FILE* fOut);
+static void processMAC(const char* address, FILE* fOut);
+
+static void atExit();
+static void usage();
+
+/* Are we in reverse resolve mode? */
+int g_doReverse = 0;
+int g_doVerbose = 0;
+
+/* These are globals for efficiency */
+u_char* g_packetBuf = NULL;
+char* g_domainBuf = NULL;
+u_char* g_routeBuf = NULL;
+size_t g_routeLen = 0;
+
+
+int main(int argc, char** argv)
+{
+ int useFiles = 0;
+ int ch;
+
+ /* Register clean up function */
+ atexit(atExit);
+
+ /* Parse command line options here */
+ while((ch = getopt(argc, argv, "rfv")) != -1)
+ {
+ switch(ch)
+ {
+ /* Treat arguments as files */
+ case 'f':
+ useFiles = 1;
+ break;
+
+ case 'v':
+ g_doVerbose = 1;
+ break;
+
+ /* Do reverse resolve */
+ case 'r':
+ g_doReverse = 1;
+ break;
+
+ case '?':
+ default:
+ usage();
+ }
+ }
+
+ argc -= optind;
+ argv += optind;
+
+ if(argc)
+ {
+ while(argc > 0)
+ {
+ /* Process the argument as a file full of addresses */
+ if(useFiles)
+ {
+ FILE* file = fopen(argv[0], "r");
+ if(file == NULL)
+ err(1, "can't open file: %s", argv[0]);
+
+ processFile(file, stdout);
+
+ fclose(file);
+ }
+
+ /* Process each argument as an address */
+ else
+ {
+ processAddress(argv[0], stdout);
+ }
+
+ argc--;
+ argv++;
+ }
+ }
+ else
+ {
+ /* No args, just process stdin etc... */
+ processFile(stdin, stdout);
+ }
+
+ exit(0);
+}
+
+
+/**
+ * Eats comments and spaces
+ */
+static void eatSpace(FILE* file)
+{
+ char ch;
+
+ do
+ {
+ ch = getc(file);
+
+ if(ch == '#')
+ {
+ while(ch != '\n')
+ ch = getc(file);
+ }
+ }
+ while(isspace(ch));
+
+ ungetc(ch, file);
+}
+
+
+/**
+ * Read addresses from a file and process
+ */
+static void processFile(FILE* fIn, FILE* fOut)
+{
+ /* Allocate memory, cache for efficiency */
+ if(g_domainBuf == NULL)
+ {
+ g_domainBuf = (char*)malloc(sizeof(char) * MAXDNAME);
+ if(g_domainBuf == NULL)
+ errx(1, "out of memory.");
+ }
+
+
+ /* And process rest of file */
+ eatSpace(fIn);
+
+ while(!feof(fIn) && !ferror(fIn))
+ {
+ char ch;
+ int i = 0;
+
+ while(1)
+ {
+ ch = fgetc(fIn);
+
+ if(isspace(ch))
+ break;
+
+ if(i < MAXDNAME)
+ g_domainBuf[i] = ch;
+
+ i++;
+ }
+
+ g_domainBuf[i] = 0;
+
+ processAddress(g_domainBuf, fOut);
+
+ eatSpace(fIn);
+ }
+
+ /* TODO: Should this be a warning or quit? */
+ if(ferror(fIn))
+ err(1, "error reading file");
+}
+
+
+/**
+ * Main address processing function
+ */
+static void processAddress(const char* address, FILE* fOut)
+{
+ if(g_doVerbose)
+ fprintf(stderr, "resolve: resolving %s\n", address);
+
+ /* If it's an IP then .... */
+ if(strlen(address) == strspn(address, "0123456789."))
+ {
+ if(g_doReverse)
+ processReverse(address, fOut);
+
+ else
+ processNone(address, fOut);
+ }
+
+ /* If it's a MAC address then .... */
+ else if(strlen(address) == strspn(address, "0123456789abcdefABCDEF-:"))
+ {
+ if(g_doReverse)
+ processNone(address, fOut);
+ else
+ processMAC(address, fOut);
+ }
+
+ /* If it's a net block then .... */
+ if(strlen(address) == strspn(address, "0123456789./"))
+ {
+ if(g_doReverse)
+ warnx("can't reverse resolve net block: %s", address);
+ else
+ processNone(address, fOut);
+ }
+
+ /* Otherwise it should be a domain name. try to resolve it. */
+ else
+ {
+ if(g_doReverse)
+ processNone(address, fOut);
+ else
+ processHost(address, fOut);
+ }
+}
+
+
+/**
+ * Used if address is aleady (hopefully) in correct form
+ */
+static void processNone(const char* address, FILE* fOut)
+{
+ fprintf(fOut, address);
+ fputc('\n', fOut);
+}
+
+
+/**
+ * Forward resolve a host name into an IP
+ */
+static void processHost(const char* address, FILE* fOut)
+{
+ int ret;
+ ns_msg handle;
+ int rrnum;
+ ns_rr rr;
+
+ /* Allocation cached for efficiency */
+ if(g_packetBuf == NULL)
+ {
+ g_packetBuf = (u_char*)malloc(sizeof(u_char) * PACKETSZ);
+ if(g_packetBuf == NULL)
+ errx(1, "out of memory.");
+ }
+
+ /* Do a DNS lookup */
+ ret = res_search(address, C_IN, ns_t_a, g_packetBuf, PACKETSZ);
+ if(ret == -1)
+ warnx("couldn't resolve: %s\n", address);
+ else
+ {
+ /* Initialize a handle to this response. */
+ if(ns_initparse(g_packetBuf, ret, &handle) < 0)
+ warn("couldn't parse dns response: %s\n", strerror(errno));
+ else
+ {
+ /* Parse the packet */
+ for(rrnum = 0; rrnum < ns_msg_count(handle, ns_s_an); rrnum++)
+ {
+ if(!ns_parserr(&handle, ns_s_an, rrnum, &rr))
+ {
+ if(ns_rr_type(rr) == ns_t_a && /* It's a host adress */
+ ns_rr_rdlen(rr) == 0x04) /* And has an IP */
+ {
+ struct in_addr addr;
+ memcpy(&(addr.s_addr), ns_rr_rdata(rr), 0x04);
+ fprintf(fOut, inet_ntoa(addr));
+ fputc('\n', fOut);
+ }
+ }
+ }
+ }
+ }
+}
+
+
+/**
+ * Reverse resolve an IP into a host name
+ */
+static void processReverse(const char* address, FILE* fOut)
+{
+ int ret;
+ ns_msg handle;
+ int rrnum;
+ ns_rr rr;
+ u_int32_t ha;
+ char name[NS_MAXDNAME];
+ struct in_addr addr;
+
+ /* Is it a valid IP address first of all */
+ if(!inet_aton(address, &addr))
+ {
+ warnx("invalid ip address: %s\n", address);
+ return;
+ }
+
+ /* Format query */
+ ha = ntohl(addr.s_addr);
+
+ sprintf(name, "%u.%u.%u.%u.IN-ADDR.ARPA.",
+ (ha) & 0xff,
+ (ha >> 8) & 0xff,
+ (ha >> 16) & 0xff,
+ (ha >> 24) & 0xff);
+
+ /* Allocation cached for efficiency */
+ if(g_packetBuf == NULL)
+ {
+ g_packetBuf = (u_char*)malloc(sizeof(u_char) * PACKETSZ);
+ if(g_packetBuf == NULL)
+ errx("out of memory.");
+ }
+
+ /* Do that lookup */
+ ret = res_search(name, C_IN, ns_t_ptr, g_packetBuf, PACKETSZ);
+ if(ret == -1)
+ warnx("couldn't resolve: %s\n", name);
+ else
+ {
+ /* Initialize a handle to this response. */
+ if(ns_initparse(g_packetBuf, ret, &handle) < 0)
+ warn("couldn't parse dns response");
+ else
+ {
+ /* Parse the packet */
+ for(rrnum = 0; rrnum < ns_msg_count(handle, ns_s_an); rrnum++)
+ {
+ if(!ns_parserr(&handle, ns_s_an, rrnum, &rr))
+ {
+ if(ns_rr_type(rr) == ns_t_ptr) /* It's a domain pointer */
+ {
+ /* Expand the host's name */
+ if (ns_name_uncompress(
+ ns_msg_base(handle),/* Start of the packet */
+ ns_msg_end(handle), /* End of the packet */
+ ns_rr_rdata(rr), /* Position in the packet*/
+ name, /* Result */
+ MAXDNAME) /* Size of nsList buffer */
+ < 0) /* Negative: error */
+ {
+ warn("couldn't parse dns response");
+ }
+ else
+ {
+ fprintf(fOut, "%s\n", name);
+ }
+ }
+ }
+ }
+ }
+ }
+}
+
+
+/**
+ * Parse components of a MAC address
+ */
+static int parseMAC(const char* address, u_char* mac)
+{
+ int i;
+
+ for(i = 0; i < 6; i++)
+ {
+ char* end;
+ int part;
+
+ part = strtol(address, &end, 16);
+
+ if(i != 5 && *end != ':' && *end != '-')
+ return 0;
+
+ if(part < 0 || part > 255)
+ return 0;
+
+ mac[i] = (u_char)part;
+
+ address = end + 1;
+ }
+
+ return 1;
+}
+
+
+#define ROUNDUP(a) \
+ ((a) > 0 ? (1 + (((a) - 1) | (sizeof(long) - 1))) : sizeof(long))
+
+/**
+ * Reverse resolve MAC address if in the ARP table
+ */
+static void processMAC(const char* address, FILE* fOut)
+{
+ u_char* next;
+ struct rt_msghdr* rtm;
+ struct sockaddr_inarp* sin;
+ struct sockaddr_dl* sdl;
+ u_char mac[6];
+
+ /* Load the kernel routing table */
+ if(g_routeBuf == NULL)
+ {
+ int mib[6];
+
+ 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, &g_routeLen, NULL, 0) < 0)
+ errx(1, "can't load routing table");
+
+ g_routeBuf = malloc(g_routeLen);
+
+ if(g_routeBuf == NULL)
+ errx(1, "out of memory");
+
+ if(sysctl(mib, 6, g_routeBuf, &g_routeLen, NULL, 0) < 0)
+ errx(1, "can't load routing table");
+ }
+
+ /* Get MAC bytes */
+ if(!parseMAC(address, mac))
+ {
+ warn("invalid MAC address: %s", address);
+ return;
+ }
+
+ /* Look for it in the routing table */
+ for(next = g_routeBuf; next < (g_routeBuf + g_routeLen); next += rtm->rtm_msglen)
+ {
+ rtm = (struct rt_msghdr*)next;
+ sin = (struct sockaddr_inarp*)(rtm + 1);
+ (char*)sdl = (char*)sin + ROUNDUP(sin->sin_len);
+
+ if(!memcmp(LLADDR(sdl), mac, sizeof(mac)))
+ {
+ fprintf(fOut, inet_ntoa(sin->sin_addr));
+ fputc('\n', fOut);
+ return;
+ }
+ }
+
+ /* oops */
+ warnx("unlisted MAC address: %s", address);
+}
+
+
+
+static void usage()
+{
+ fprintf(stderr, "usage: resolve [-rv] -f file ...\n");
+ fprintf(stderr, " resolve [-rv] address ...\n");
+ exit(2);
+}
+
+
+/*
+ * Clean up function.
+ */
+static void atExit()
+{
+ if(g_packetBuf != NULL)
+ free(g_packetBuf);
+ if(g_domainBuf != NULL)
+ free(g_domainBuf);
+}
+
+
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