/* Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/*
 * logresolve 1.1
 *
 * Tom Rathborne - tomr uunet.ca - http://www.uunet.ca/~tomr/
 * UUNET Canada, April 16, 1995
 *
 * Rewritten by David Robinson. (drtr ast.cam.ac.uk)
 *
 * Usage: logresolve [-s filename] [-c] < access_log > new_log
 *
 * Arguments:
 *    -s filename     name of a file to record statistics
 *    -c              check the DNS for a matching A record for the host.
 *
 * Notes:
 *
 * To generate meaningful statistics from an HTTPD log file, it's good
 * to have the domain name of each machine that accessed your site, but
 * doing this on the fly can slow HTTPD down.
 *
 * Compiling NCSA HTTPD with the -DMINIMAL_DNS flag turns IP#->hostname
 * resolution off. Before running your stats program, just run your log
 * file through this program (logresolve) and all of your IP numbers will
 * be resolved into hostnames (where possible).
 *
 * logresolve takes an HTTPD access log (in the COMMON log file format,
 * or any other format that has the IP number/domain name as the first
 * field for that matter), and outputs the same file with all of the
 * domain names looked up. Where no domain name can be found, the IP
 * number is left in.
 *
 * To minimize impact on your nameserver, logresolve has its very own
 * internal hash-table cache. This means that each IP number will only
 * be looked up the first time it is found in the log file.
 *
 * The -c option causes logresolve to apply the same check as httpd
 * compiled with -DMAXIMUM_DNS; after finding the hostname from the IP
 * address, it looks up the IP addresses for the hostname and checks
 * that one of these matches the original address.
 */

#include "apr_lib.h"
#if APR_HAVE_STDIO_H
#include <stdio.h>
#endif
#if APR_HAVE_STDLIB_H
#include <stdlib.h>
#endif
#if APR_HAVE_CTYPE_H
#include <ctype.h>
#endif
#if APR_HAVE_NETDB_H
#include <netdb.h>
#endif
#if APR_HAVE_NETINET_IN_H
#include <netinet/in.h>
#endif
#if APR_HAVE_STRING_H
#include <string.h>
#endif
#if APR_HAVE_SYS_SOCKET_H
#include <sys/socket.h>
#endif
#if APR_HAVE_ARPA_INET_H
#include <arpa/inet.h>
#endif

static void cgethost(struct in_addr ipnum, char *string, int check);
static int get_line();
static void stats(FILE *output);

#ifdef BEOS
#define NO_ADDRESS NO_DATA
#endif


/* maximum length of a domain name */
#ifndef MAXDNAME
#define MAXDNAME 256
#endif

/* number of buckets in cache hash apr_table_t */
#define BUCKETS 256

/*
 * struct nsrec - record of nameservice for cache linked list
 *
 * ipnum - IP number hostname - hostname noname - nonzero if IP number has no
 * hostname, i.e. hostname=IP number
 */

struct nsrec {
    struct in_addr ipnum;
    char *hostname;
    int noname;
    struct nsrec *next;
}    *nscache[BUCKETS];

/*
 * statistics - obvious
 */

#ifndef h_errno
#ifdef __CYGWIN__
extern __declspec(dllimport) int h_errno;
#else
extern int h_errno; /* some machines don't have this in their headers */
#endif
#endif

/* largest value for h_errno */

#define MAX_ERR (NO_ADDRESS)
#define UNKNOWN_ERR (MAX_ERR+1)
#define NO_REVERSE  (MAX_ERR+2)

static int cachehits = 0;
static int cachesize = 0;
static int entries = 0;
static int resolves = 0;
static int withname = 0;
static int errors[MAX_ERR + 3];
static size_t maxline=0;
static char *line = NULL;

/*
 * cgethost - gets hostname by IP address, caching, and adding unresolvable
 * IP numbers with their IP number as hostname, setting noname flag
 */

static void cgethost (struct in_addr ipnum, char *string, int check)
{
    struct nsrec **current, *new;
    struct hostent *hostdata;
    char *name;

    current = &nscache[((ipnum.s_addr + (ipnum.s_addr >> 8) +
                         (ipnum.s_addr >> 16) + (ipnum.s_addr >> 24)) % BUCKETS)];

    while (*current != NULL && ipnum.s_addr != (*current)->ipnum.s_addr)
        current = &(*current)->next;

    if (*current == NULL) {
        cachesize++;
        new = (struct nsrec *) malloc(sizeof(struct nsrec));
        if (new == NULL) {
            perror("malloc");
            fprintf(stderr, "Insufficient memory\n");
            exit(1);
        }
        *current = new;
        new->next = NULL;

        new->ipnum = ipnum;

        hostdata = gethostbyaddr((const char *) &ipnum, sizeof(struct in_addr),
                                 AF_INET);
        if (hostdata == NULL) {
            if (h_errno > MAX_ERR)
                errors[UNKNOWN_ERR]++;
            else
                errors[h_errno]++;
            new->noname = h_errno;
            name = strdup(inet_ntoa(ipnum));
        }
        else {
            new->noname = 0;
            name = strdup(hostdata->h_name);
            if (check) {
                if (name == NULL) {
                    perror("strdup");
                    fprintf(stderr, "Insufficient memory\n");
                    exit(1);
                }
                hostdata = gethostbyname(name);
                if (hostdata != NULL) {
                    char **hptr;

                    for (hptr = hostdata->h_addr_list; *hptr != NULL; hptr++)
                        if (((struct in_addr *) (*hptr))->s_addr == ipnum.s_addr)
                            break;
                    if (*hptr == NULL)
                        hostdata = NULL;
                }
                if (hostdata == NULL) {
                    fprintf(stderr, "Bad host: %s != %s\n", name,
                            inet_ntoa(ipnum));
                    new->noname = NO_REVERSE;
                    free(name);
                    name = strdup(inet_ntoa(ipnum));
                    errors[NO_REVERSE]++;
                }
            }
        }
        new->hostname = name;
        if (new->hostname == NULL) {
            perror("strdup");
            fprintf(stderr, "Insufficient memory\n");
            exit(1);
        }
    }
    else
        cachehits++;

    /* size of string == MAXDNAME +1 */
    strncpy(string, (*current)->hostname, MAXDNAME);
    string[MAXDNAME] = '\0';
}

/*
 * prints various statistics to output
 */

static void stats (FILE *output)
{
    int i;
    char *ipstring;
    struct nsrec *current;
    char *errstring[MAX_ERR + 3];

    for (i = 0; i < MAX_ERR + 3; i++)
        errstring[i] = "Unknown error";
    errstring[HOST_NOT_FOUND] = "Host not found";
    errstring[TRY_AGAIN] = "Try again";
    errstring[NO_RECOVERY] = "Non recoverable error";
    errstring[NO_DATA] = "No data record";
    errstring[NO_ADDRESS] = "No address";
    errstring[NO_REVERSE] = "No reverse entry";

    fprintf(output, "logresolve Statistics:\n");

    fprintf(output, "Entries: %d\n", entries);
    fprintf(output, "    With name   : %d\n", withname);
    fprintf(output, "    Resolves    : %d\n", resolves);
    if (errors[HOST_NOT_FOUND])
        fprintf(output, "    - Not found : %d\n", errors[HOST_NOT_FOUND]);
    if (errors[TRY_AGAIN])
        fprintf(output, "    - Try again : %d\n", errors[TRY_AGAIN]);
    if (errors[NO_DATA])
        fprintf(output, "    - No data   : %d\n", errors[NO_DATA]);
    if (errors[NO_ADDRESS])
        fprintf(output, "    - No address: %d\n", errors[NO_ADDRESS]);
    if (errors[NO_REVERSE])
        fprintf(output, "    - No reverse: %d\n", errors[NO_REVERSE]);
    fprintf(output, "Cache hits      : %d\n", cachehits);
    fprintf(output, "Cache size      : %d\n", cachesize);
    fprintf(output, "Cache buckets   :     IP number * hostname\n");

    for (i = 0; i < BUCKETS; i++)
        for (current = nscache[i]; current != NULL; current = current->next) {
            ipstring = inet_ntoa(current->ipnum);
            if (current->noname == 0)
                fprintf(output, "  %3d  %15s - %s\n", i, ipstring,
                        current->hostname);
            else {
                if (current->noname > MAX_ERR + 2)
                    fprintf(output, "  %3d  %15s : Unknown error\n", i,
                            ipstring);
                else
                    fprintf(output, "  %3d  %15s : %s\n", i, ipstring,
                            errstring[current->noname]);
            }
        }
}


/*
 * gets a line from stdin
 */

static int get_line ()
{
    ssize_t len;
    char *cp;

    if ( (len = getline(&line, &maxline, stdin)) == -1 )
        return (0);
    cp = line + len -1;
    if (*cp == '\n')
        *cp = '\0';
    return (1);
}

int main (int argc, char *argv[])
{
    struct in_addr ipnum;
    char *bar, hoststring[MAXDNAME + 1], *statfile;
    int i, check;

#if defined(WIN32) || (defined(NETWARE) && defined(USE_WINSOCK))
    /*  If we apr'ify this code, apr_pool_create/apr_pool_destroy
     *  should perform the WSAStartup/WSACleanup for us.
     */
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 0), &wsaData);
#endif

    check = 0;
    statfile = NULL;
    for (i = 1; i < argc; i++) {
        if (strcmp(argv[i], "-c") == 0)
            check = 1;
        else if (strcmp(argv[i], "-s") == 0) {
            if (i == argc - 1) {
                fprintf(stderr, "logresolve: missing filename to -s\n");
                exit(1);
            }
            i++;
            statfile = argv[i];
        }
        else {
            fprintf(stderr, "Usage: logresolve [-s statfile] [-c] < input > output\n");
            exit(0);
        }
    }

    for (i = 0; i < BUCKETS; i++)
        nscache[i] = NULL;
    for (i = 0; i < MAX_ERR + 2; i++)
        errors[i] = 0;

    while (get_line()) {
        if (line[0] == '\0')
            continue;
        entries++;
        if (!apr_isdigit(line[0])) {  /* short cut */
            puts(line);
            withname++;
            continue;
        }
        bar = strchr(line, ' ');
        if (bar != NULL)
            *bar = '\0';
        ipnum.s_addr = inet_addr(line);
        if (ipnum.s_addr == 0xffffffffu) {
            if (bar != NULL)
                *bar = ' ';
            puts(line);
            withname++;
            continue;
        }

        resolves++;

        cgethost(ipnum, hoststring, check);
        if (bar != NULL)
            printf("%s %s\n", hoststring, bar + 1);
        else
            puts(hoststring);
    }

#if defined(WIN32) || (defined(NETWARE) && defined(USE_WINSOCK))
     WSACleanup();
#endif

    if (statfile != NULL) {
        FILE *fp;
        fp = fopen(statfile, "w");
        if (fp == NULL) {
            fprintf(stderr, "logresolve: could not open statistics file '%s'\n"
                    ,statfile);
            exit(1);
        }
        stats(fp);
        fclose(fp);
    }

    return (0);
}