| /* 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. |
| */ |
| |
| /* |
| * 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 "httpd.h" |
| #include "http_config.h" |
| #include "http_log.h" |
| #include "multithread.h" |
| |
| typedef struct { |
| unsigned int stamp; |
| unsigned int in_addr; |
| unsigned int pid; |
| #ifdef MULTITHREAD |
| unsigned int tid; |
| #endif |
| unsigned short counter; |
| } unique_id_rec; |
| |
| /* 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. |
| * |
| * 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; |
| |
| #ifdef WIN32 |
| |
| static DWORD tls_index; |
| |
| BOOL WINAPI DllMain (HINSTANCE dllhandle, DWORD reason, LPVOID reserved) |
| { |
| LPVOID memptr; |
| |
| switch (reason) { |
| case DLL_PROCESS_ATTACH: |
| tls_index = TlsAlloc(); |
| case DLL_THREAD_ATTACH: /* intentional no break */ |
| TlsSetValue(tls_index, calloc(sizeof(unique_id_rec), 1)); |
| break; |
| case DLL_THREAD_DETACH: |
| memptr = TlsGetValue(tls_index); |
| if (memptr) { |
| free (memptr); |
| TlsSetValue (tls_index, 0); |
| } |
| break; |
| } |
| |
| return TRUE; |
| } |
| |
| static unique_id_rec* get_cur_unique_id(int parent) |
| { |
| /* Apache initializes the child process, not the individual child threads. |
| * Copy the original parent record if this->pid is not yet initialized. |
| */ |
| static unique_id_rec *parent_id; |
| unique_id_rec *cur_unique_id = (unique_id_rec *) TlsGetValue(tls_index); |
| |
| if (parent) { |
| parent_id = cur_unique_id; |
| } |
| else if (!cur_unique_id->pid) { |
| memcpy(cur_unique_id, parent_id, sizeof(*parent_id)); |
| } |
| return cur_unique_id; |
| } |
| |
| #else /* !WIN32 */ |
| |
| /* Even when not MULTITHREAD, this will return a single structure, since |
| * APACHE_TLS should be defined as empty on single-threaded platforms. |
| */ |
| static unique_id_rec* get_cur_unique_id(int parent) |
| { |
| static APACHE_TLS unique_id_rec spcid; |
| return &spcid; |
| } |
| |
| #endif /* !WIN32 */ |
| |
| |
| /* |
| * Number of elements in the structure unique_id_rec. |
| */ |
| #ifdef MULTITHREAD |
| #define UNIQUE_ID_REC_MAX 5 |
| #else |
| #define UNIQUE_ID_REC_MAX 4 |
| #endif |
| |
| 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(server_rec *s, pool *p) |
| { |
| #ifndef MAXHOSTNAMELEN |
| #define MAXHOSTNAMELEN 256 |
| #endif |
| char str[MAXHOSTNAMELEN + 1]; |
| struct hostent *hent; |
| #ifndef NO_GETTIMEOFDAY |
| struct timeval tv; |
| #endif |
| unique_id_rec *cur_unique_id = get_cur_unique_id(1); |
| |
| /* |
| * 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); |
| #ifdef MULTITHREAD |
| unique_id_rec_offset[3] = XtOffsetOf(unique_id_rec, tid); |
| unique_id_rec_size[3] = sizeof(cur_unique_id->tid); |
| unique_id_rec_offset[4] = XtOffsetOf(unique_id_rec, counter); |
| unique_id_rec_size[4] = sizeof(cur_unique_id->counter); |
| 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]; |
| #else |
| unique_id_rec_offset[3] = XtOffsetOf(unique_id_rec, counter); |
| unique_id_rec_size[3] = sizeof(cur_unique_id->counter); |
| 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]; |
| #endif |
| |
| /* |
| * 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, s, |
| "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, s, |
| "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, s, |
| "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. |
| */ |
| #ifdef NO_GETTIMEOFDAY |
| sleep(1); |
| #else |
| if (gettimeofday(&tv, NULL) == -1) { |
| sleep(1); |
| } |
| else if (tv.tv_usec) { |
| tv.tv_sec = 0; |
| tv.tv_usec = 1000000 - tv.tv_usec; |
| select(0, NULL, NULL, NULL, &tv); |
| } |
| #endif |
| } |
| |
| static void unique_id_child_init(server_rec *s, pool *p) |
| { |
| pid_t pid; |
| #ifndef NO_GETTIMEOFDAY |
| struct timeval tv; |
| #endif |
| unique_id_rec *cur_unique_id = get_cur_unique_id(1); |
| |
| /* |
| * 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. |
| */ |
| 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 ((pid_t)cur_unique_id->pid != pid) { |
| ap_log_error(APLOG_MARK, APLOG_NOERRNO|APLOG_CRIT, 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. |
| */ |
| #ifndef NO_GETTIMEOFDAY |
| if (gettimeofday(&tv, NULL) == -1) { |
| cur_unique_id->counter = 0; |
| } |
| else { |
| /* Some systems have very low variance on the low end of their |
| * system counter, defend against that. |
| */ |
| cur_unique_id->counter = tv.tv_usec / 10; |
| } |
| #else |
| cur_unique_id->counter = 0; |
| #endif |
| |
| /* |
| * 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. |
| */ |
| struct { |
| unique_id_rec foo; |
| unsigned char pad[2]; |
| } paddedbuf; |
| unsigned char *x,*y; |
| unsigned short counter; |
| const char *e; |
| int i,j,k; |
| unique_id_rec *cur_unique_id = get_cur_unique_id(0); |
| |
| /* 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 = ap_table_get(r->subprocess_env, "REDIRECT_UNIQUE_ID"))) { |
| ap_table_setn(r->subprocess_env, "UNIQUE_ID", e); |
| return DECLINED; |
| } |
| |
| cur_unique_id->stamp = htonl((unsigned int)r->request_time); |
| |
| #ifdef MULTITHREAD |
| /* |
| * 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 pid+tids between |
| * children. |
| */ |
| cur_unique_id->tid = gettid(); |
| cur_unique_id->tid = htonl(cur_unique_id->tid); |
| #endif |
| |
| /* we'll use a temporal buffer to avoid uuencoding the possible internal |
| * paddings of the original structure |
| */ |
| x = (unsigned char *) &paddedbuf; |
| y = (unsigned char *) cur_unique_id; |
| k = 0; |
| for (i = 0; i < UNIQUE_ID_REC_MAX; i++) { |
| y = ((unsigned char *) cur_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 *)ap_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 */ |
| ap_table_setn(r->subprocess_env, "UNIQUE_ID", str); |
| |
| /* and increment the identifier for the next call */ |
| counter = ntohs(cur_unique_id->counter) + 1; |
| cur_unique_id->counter = htons(counter); |
| |
| return DECLINED; |
| } |
| |
| module MODULE_VAR_EXPORT unique_id_module = { |
| STANDARD_MODULE_STUFF, |
| unique_id_global_init, /* initializer */ |
| NULL, /* dir config creater */ |
| NULL, /* dir merger --- default is to override */ |
| NULL, /* server config */ |
| NULL, /* merge server configs */ |
| NULL, /* command table */ |
| NULL, /* handlers */ |
| NULL, /* filename translation */ |
| NULL, /* check_user_id */ |
| NULL, /* check auth */ |
| NULL, /* check access */ |
| NULL, /* type_checker */ |
| NULL, /* fixups */ |
| NULL, /* logger */ |
| NULL, /* header parser */ |
| unique_id_child_init, /* child_init */ |
| NULL, /* child_exit */ |
| gen_unique_id /* post_read_request */ |
| }; |
