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-/* ====================================================================
- * The Apache Software License, Version 1.1
- *
- * Copyright (c) 2000-2001 The Apache Software Foundation. All rights
- * reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- *
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- *
- * 3. The end-user documentation included with the redistribution,
- * if any, must include the following acknowledgment:
- * "This product includes software developed by the
- * Apache Software Foundation (http://www.apache.org/)."
- * Alternately, this acknowledgment may appear in the software itself,
- * if and wherever such third-party acknowledgments normally appear.
- *
- * 4. The names "Apache" and "Apache Software Foundation" must
- * not be used to endorse or promote products derived from this
- * software without prior written permission. For written
- * permission, please contact apache@apache.org.
- *
- * 5. Products derived from this software may not be called "Apache",
- * nor may "Apache" appear in their name, without prior written
- * permission of the Apache Software Foundation.
- *
- * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
- * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
- * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
- * DISCLAIMED. IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
- * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
- * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
- * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
- * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
- * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
- * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
- * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
- * SUCH DAMAGE.
- * ====================================================================
- *
- * This software consists of voluntary contributions made by many
- * individuals on behalf of the Apache Software Foundation. For more
- * information on the Apache Software Foundation, please see
- * <http://www.apache.org/>.
- *
- * Portions of this software are based upon public domain software
- * originally written at the National Center for Supercomputing Applications,
- * University of Illinois, Urbana-Champaign.
- */
-
-/*
- * mod_unique_id.c: generate a unique identifier for each request
- *
- * Original author: Dean Gaudet <dgaudet@arctic.org>
- * UUencoding modified by: Alvaro Martinez Echevarria <alvaro@lander.es>
- */
-
-#include "apr_general.h" /* for XtOffsetOf */
-
-#include "httpd.h"
-#include "http_config.h"
-#include "http_log.h"
-#include "http_protocol.h" /* for ap_hook_post_read_request */
-
-#if APR_HAVE_NETDB_H
-#include <netdb.h>
-#endif
-#if APR_HAVE_ARPA_INET_H
-#include <arpa/inet.h>
-#endif
-#if APR_HAVE_UNISTD_H
-#include <unistd.h>
-#endif
-
-typedef struct {
- unsigned int stamp;
- unsigned int in_addr;
- unsigned int pid;
- unsigned short counter;
- unsigned int thread_index;
-} unique_id_rec;
-
-/* We are using thread_index (the index into the scoreboard), because we
- * cannont garauntee the thread_id will be an integer.
- *
- * This code looks like it won't give a unique ID with the new thread logic.
- * It will. The reason is, we don't increment the counter in a thread_safe
- * manner. Because the thread_index is also in the unique ID now, this does
- * not matter. In order for the id to not be unique, the same thread would
- * have to get the same counter twice in the same second.
- */
-
-/* Comments:
- *
- * We want an identifier which is unique across all hits, everywhere.
- * "everywhere" includes multiple httpd instances on the same machine, or on
- * multiple machines. Essentially "everywhere" should include all possible
- * httpds across all servers at a particular "site". We make some assumptions
- * that if the site has a cluster of machines then their time is relatively
- * synchronized. We also assume that the first address returned by a
- * gethostbyname (gethostname()) is unique across all the machines at the
- * "site".
- *
- * We also further assume that pids fit in 32-bits. If something uses more
- * than 32-bits, the fix is trivial, but it requires the unrolled uuencoding
- * loop to be extended. * A similar fix is needed to support multithreaded
- * servers, using a pid/tid combo.
- *
- * Together, the in_addr and pid are assumed to absolutely uniquely identify
- * this one child from all other currently running children on all servers
- * (including this physical server if it is running multiple httpds) from each
- * other.
- *
- * The stamp and counter are used to distinguish all hits for a particular
- * (in_addr,pid) pair. The stamp is updated using r->request_time,
- * saving cpu cycles. The counter is never reset, and is used to permit up to
- * 64k requests in a single second by a single child.
- *
- * The 112-bits of unique_id_rec are encoded using the alphabet
- * [A-Za-z0-9@-], resulting in 19 bytes of printable characters. That is then
- * stuffed into the environment variable UNIQUE_ID so that it is available to
- * other modules. The alphabet choice differs from normal base64 encoding
- * [A-Za-z0-9+/] because + and / are special characters in URLs and we want to
- * make it easy to use UNIQUE_ID in URLs.
- *
- * Note that UNIQUE_ID should be considered an opaque token by other
- * applications. No attempt should be made to dissect its internal components.
- * It is an abstraction that may change in the future as the needs of this
- * module change.
- *
- * It is highly desirable that identifiers exist for "eternity". But future
- * needs (such as much faster webservers, moving to 64-bit pids, or moving to a
- * multithreaded server) may dictate a need to change the contents of
- * unique_id_rec. Such a future implementation should ensure that the first
- * field is still a time_t stamp. By doing that, it is possible for a site to
- * have a "flag second" in which they stop all of their old-format servers,
- * wait one entire second, and then start all of their new-servers. This
- * procedure will ensure that the new space of identifiers is completely unique
- * from the old space. (Since the first four unencoded bytes always differ.)
- */
-/*
- * Sun Jun 7 05:43:49 CEST 1998 -- Alvaro
- * More comments:
- * 1) The UUencoding prodecure is now done in a general way, avoiding the problems
- * with sizes and paddings that can arise depending on the architecture. Now the
- * offsets and sizes of the elements of the unique_id_rec structure are calculated
- * in unique_id_global_init; and then used to duplicate the structure without the
- * paddings that might exist. The multithreaded server fix should be now very easy:
- * just add a new "tid" field to the unique_id_rec structure, and increase by one
- * UNIQUE_ID_REC_MAX.
- * 2) unique_id_rec.stamp has been changed from "time_t" to "unsigned int", because
- * its size is 64bits on some platforms (linux/alpha), and this caused problems with
- * htonl/ntohl. Well, this shouldn't be a problem till year 2106.
- */
-
-static unsigned global_in_addr;
-
-static unique_id_rec cur_unique_id;
-
-/*
- * Number of elements in the structure unique_id_rec.
- */
-#define UNIQUE_ID_REC_MAX 5
-
-static unsigned short unique_id_rec_offset[UNIQUE_ID_REC_MAX],
- unique_id_rec_size[UNIQUE_ID_REC_MAX],
- unique_id_rec_total_size,
- unique_id_rec_size_uu;
-
-static void unique_id_global_init(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *main_server)
-{
-#ifndef MAXHOSTNAMELEN
-#define MAXHOSTNAMELEN 256
-#endif
- char str[MAXHOSTNAMELEN + 1];
- struct hostent *hent;
- apr_short_interval_time_t pause;
-
- /*
- * Calculate the sizes and offsets in cur_unique_id.
- */
- unique_id_rec_offset[0] = XtOffsetOf(unique_id_rec, stamp);
- unique_id_rec_size[0] = sizeof(cur_unique_id.stamp);
- unique_id_rec_offset[1] = XtOffsetOf(unique_id_rec, in_addr);
- unique_id_rec_size[1] = sizeof(cur_unique_id.in_addr);
- unique_id_rec_offset[2] = XtOffsetOf(unique_id_rec, pid);
- unique_id_rec_size[2] = sizeof(cur_unique_id.pid);
- unique_id_rec_offset[3] = XtOffsetOf(unique_id_rec, counter);
- unique_id_rec_size[3] = sizeof(cur_unique_id.counter);
- unique_id_rec_offset[4] = XtOffsetOf(unique_id_rec, thread_index);
- unique_id_rec_size[4] = sizeof(cur_unique_id.thread_index);
- unique_id_rec_total_size = unique_id_rec_size[0] + unique_id_rec_size[1] +
- unique_id_rec_size[2] + unique_id_rec_size[3] +
- unique_id_rec_size[4];
-
- /*
- * Calculate the size of the structure when encoded.
- */
- unique_id_rec_size_uu = (unique_id_rec_total_size*8+5)/6;
-
- /*
- * Now get the global in_addr. Note that it is not sufficient to use one
- * of the addresses from the main_server, since those aren't as likely to
- * be unique as the physical address of the machine
- */
- if (gethostname(str, sizeof(str) - 1) != 0) {
- ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_ALERT, errno, main_server,
- "gethostname: mod_unique_id requires the hostname of the server");
- exit(1);
- }
- str[sizeof(str) - 1] = '\0';
-
- if ((hent = gethostbyname(str)) == NULL) {
- ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_ALERT, h_errno, main_server,
- "mod_unique_id: unable to gethostbyname(\"%s\")", str);
- exit(1);
- }
-
- global_in_addr = ((struct in_addr *) hent->h_addr_list[0])->s_addr;
-
- ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_INFO, 0, main_server,
- "mod_unique_id: using ip addr %s",
- inet_ntoa(*(struct in_addr *) hent->h_addr_list[0]));
-
- /*
- * If the server is pummelled with restart requests we could possibly end
- * up in a situation where we're starting again during the same second
- * that has been used in previous identifiers. Avoid that situation.
- *
- * In truth, for this to actually happen not only would it have to restart
- * in the same second, but it would have to somehow get the same pids as
- * one of the other servers that was running in that second. Which would
- * mean a 64k wraparound on pids ... not very likely at all.
- *
- * But protecting against it is relatively cheap. We just sleep into the
- * next second.
- */
- pause = (apr_short_interval_time_t)(1000000 - (apr_time_now() % APR_USEC_PER_SEC));
- apr_sleep(pause);
-}
-
-static void unique_id_child_init(apr_pool_t *p, server_rec *s)
-{
- pid_t pid;
- apr_time_t tv;
-
- /*
- * Note that we use the pid because it's possible that on the same
- * physical machine there are multiple servers (i.e. using Listen). But
- * it's guaranteed that none of them will share the same pids between
- * children.
- *
- * XXX: for multithread this needs to use a pid/tid combo and probably
- * needs to be expanded to 32 bits
- */
- pid = getpid();
- cur_unique_id.pid = pid;
-
- /*
- * Test our assumption that the pid is 32-bits. It's possible that
- * 64-bit machines will declare pid_t to be 64 bits but only use 32
- * of them. It would have been really nice to test this during
- * global_init ... but oh well.
- */
- if (cur_unique_id.pid != pid) {
- ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_CRIT, 0, s,
- "oh no! pids are greater than 32-bits! I'm broken!");
- }
-
- cur_unique_id.in_addr = global_in_addr;
-
- /*
- * If we use 0 as the initial counter we have a little less protection
- * against restart problems, and a little less protection against a clock
- * going backwards in time.
- */
- tv = apr_time_now();
- /* Some systems have very low variance on the low end of their system
- * counter, defend against that.
- */
- cur_unique_id.counter = tv % APR_USEC_PER_SEC / 10;
-
- /*
- * We must always use network ordering for these bytes, so that
- * identifiers are comparable between machines of different byte
- * orderings. Note in_addr is already in network order.
- */
- cur_unique_id.pid = htonl(cur_unique_id.pid);
- cur_unique_id.counter = htons(cur_unique_id.counter);
-}
-
-/* NOTE: This is *NOT* the same encoding used by base64encode ... the last two
- * characters should be + and /. But those two characters have very special
- * meanings in URLs, and we want to make it easy to use identifiers in
- * URLs. So we replace them with @ and -.
- */
-static const char uuencoder[64] = {
- 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M',
- 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z',
- 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm',
- 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z',
- '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '@', '-',
-};
-
-static int gen_unique_id(request_rec *r)
-{
- char *str;
- /*
- * Buffer padded with two final bytes, used to copy the unique_id_red
- * structure without the internal paddings that it could have.
- */
- unique_id_rec new_unique_id;
- struct {
- unique_id_rec foo;
- unsigned char pad[2];
- } paddedbuf;
- unsigned char *x,*y;
- unsigned short counter;
- const char *e;
- int i,j,k;
-
- /* copy the unique_id if this is an internal redirect (we're never
- * actually called for sub requests, so we don't need to test for
- * them) */
- if (r->prev && (e = apr_table_get(r->subprocess_env, "REDIRECT_UNIQUE_ID"))) {
- apr_table_setn(r->subprocess_env, "UNIQUE_ID", e);
- return DECLINED;
- }
-
- new_unique_id.in_addr = cur_unique_id.in_addr;
- new_unique_id.pid = cur_unique_id.pid;
- new_unique_id.counter = cur_unique_id.counter;
-
- new_unique_id.stamp = htonl((unsigned int)r->request_time);
- new_unique_id.thread_index = htonl((unsigned int)r->connection->id);
-
- /* we'll use a temporal buffer to avoid uuencoding the possible internal
- * paddings of the original structure */
- x = (unsigned char *) &paddedbuf;
- y = (unsigned char *) &new_unique_id;
- k = 0;
- for (i = 0; i < UNIQUE_ID_REC_MAX; i++) {
- y = ((unsigned char *) &new_unique_id) + unique_id_rec_offset[i];
- for (j = 0; j < unique_id_rec_size[i]; j++, k++) {
- x[k] = y[j];
- }
- }
- /*
- * We reset two more bytes just in case padding is needed for the uuencoding.
- */
- x[k++] = '\0';
- x[k++] = '\0';
-
- /* alloc str and do the uuencoding */
- str = (char *)apr_palloc(r->pool, unique_id_rec_size_uu + 1);
- k = 0;
- for (i = 0; i < unique_id_rec_total_size; i += 3) {
- y = x + i;
- str[k++] = uuencoder[y[0] >> 2];
- str[k++] = uuencoder[((y[0] & 0x03) << 4) | ((y[1] & 0xf0) >> 4)];
- if (k == unique_id_rec_size_uu) break;
- str[k++] = uuencoder[((y[1] & 0x0f) << 2) | ((y[2] & 0xc0) >> 6)];
- if (k == unique_id_rec_size_uu) break;
- str[k++] = uuencoder[y[2] & 0x3f];
- }
- str[k++] = '\0';
-
- /* set the environment variable */
- apr_table_setn(r->subprocess_env, "UNIQUE_ID", str);
-
- /* and increment the identifier for the next call */
-
- counter = ntohs(new_unique_id.counter) + 1;
- cur_unique_id.counter = htons(counter);
-
- return DECLINED;
-}
-
-static void register_hooks(apr_pool_t *p)
-{
- ap_hook_post_config(unique_id_global_init, NULL, NULL, APR_HOOK_MIDDLE);
- ap_hook_child_init(unique_id_child_init, NULL, NULL, APR_HOOK_MIDDLE);
- ap_hook_post_read_request(gen_unique_id, NULL, NULL, APR_HOOK_MIDDLE);
-}
-
-module AP_MODULE_DECLARE_DATA unique_id_module = {
- STANDARD20_MODULE_STUFF,
- NULL, /* dir config creater */
- NULL, /* dir merger --- default is to override */
- NULL, /* server config */
- NULL, /* merge server configs */
- NULL, /* command apr_table_t */
- register_hooks /* register hooks */
-};