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--- trunk/modules/metadata/mod_unique_id.c	2011/12/02 23:02:04	1209766
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+++ trunk/modules/metadata/mod_unique_id.c	2013/07/10 16:20:31	1501827
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@@ -31,14 +31,11 @@
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 #include "http_log.h"
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 #include "http_protocol.h"  /* for ap_hook_post_read_request */
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-#if APR_HAVE_UNISTD_H
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-#include <unistd.h>         /* for getpid() */
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-#endif
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+#define ROOT_SIZE 10
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 typedef struct {
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     unsigned int stamp;
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-    unsigned int in_addr;
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-    unsigned int pid;
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+    char root[ROOT_SIZE];
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     unsigned short counter;
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     unsigned int thread_index;
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 } unique_id_rec;
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@@ -64,20 +61,15 @@
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  * gethostbyname (gethostname()) is unique across all the machines at the
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  * "site".
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  *
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- * We also further assume that pids fit in 32-bits.  If something uses more
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- * than 32-bits, the fix is trivial, but it requires the unrolled uuencoding
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- * loop to be extended.  * A similar fix is needed to support multithreaded
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- * servers, using a pid/tid combo.
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- *
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- * Together, the in_addr and pid are assumed to absolutely uniquely identify
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- * this one child from all other currently running children on all servers
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- * (including this physical server if it is running multiple httpds) from each
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+ * The root is assumed to absolutely uniquely identify this one child
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+ * from all other currently running children on all servers (including
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+ * this physical server if it is running multiple httpds) from each
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  * other.
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  *
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- * The stamp and counter are used to distinguish all hits for a particular
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- * (in_addr,pid) pair.  The stamp is updated using r->request_time,
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- * saving cpu cycles.  The counter is never reset, and is used to permit up to
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- * 64k requests in a single second by a single child.
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+ * The stamp and counter are used to distinguish all hits for a
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+ * particular root.  The stamp is updated using r->request_time,
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+ * saving cpu cycles.  The counter is never reset, and is used to
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+ * permit up to 64k requests in a single second by a single child.
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  *
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  * The 144-bits of unique_id_rec are encoded using the alphabet
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  * [A-Za-z0-9@-], resulting in 24 bytes of printable characters.  That is then
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@@ -92,7 +84,7 @@
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  * module change.
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  *
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  * It is highly desirable that identifiers exist for "eternity".  But future
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- * needs (such as much faster webservers, moving to 64-bit pids, or moving to a
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+ * needs (such as much faster webservers, or moving to a
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  * multithreaded server) may dictate a need to change the contents of
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  * unique_id_rec.  Such a future implementation should ensure that the first
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  * field is still a time_t stamp.  By doing that, it is possible for a site to
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@@ -100,7 +92,15 @@
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  * wait one entire second, and then start all of their new-servers.  This
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  * procedure will ensure that the new space of identifiers is completely unique
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  * from the old space.  (Since the first four unencoded bytes always differ.)
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+ *
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+ * Note: previous implementations used 32-bits of IP address plus pid
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+ * in place of the PRNG output in the "root" field.  This was
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+ * insufficient for IPv6-only hosts, required working DNS to determine
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+ * a unique IP address (fragile), and needed a [0, 1) second sleep
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+ * call at startup to avoid pid reuse.  Use of the PRNG avoids all
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+ * these issues.
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  */
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+
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 /*
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  * Sun Jun  7 05:43:49 CEST 1998 -- Alvaro
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  * More comments:
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@@ -116,8 +116,6 @@
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  * htonl/ntohl. Well, this shouldn't be a problem till year 2106.
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  */
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-static unsigned global_in_addr;
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-
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 /*
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  * XXX: We should have a per-thread counter and not use cur_unique_id.counter
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  * XXX: in all threads, because this is bad for performance on multi-processor
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@@ -129,7 +127,7 @@
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 /*
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  * Number of elements in the structure unique_id_rec.
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  */
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-#define UNIQUE_ID_REC_MAX 5
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+#define UNIQUE_ID_REC_MAX 4
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 static unsigned short unique_id_rec_offset[UNIQUE_ID_REC_MAX],
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                       unique_id_rec_size[UNIQUE_ID_REC_MAX],
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@@ -138,113 +136,32 @@
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 static int unique_id_global_init(apr_pool_t *p, apr_pool_t *plog, apr_pool_t *ptemp, server_rec *main_server)
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 {
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-    char str[APRMAXHOSTLEN + 1];
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-    apr_status_t rv;
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-    char *ipaddrstr;
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-    apr_sockaddr_t *sockaddr;
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-
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     /*
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      * Calculate the sizes and offsets in cur_unique_id.
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      */
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     unique_id_rec_offset[0] = APR_OFFSETOF(unique_id_rec, stamp);
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     unique_id_rec_size[0] = sizeof(cur_unique_id.stamp);
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-    unique_id_rec_offset[1] = APR_OFFSETOF(unique_id_rec, in_addr);
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-    unique_id_rec_size[1] = sizeof(cur_unique_id.in_addr);
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-    unique_id_rec_offset[2] = APR_OFFSETOF(unique_id_rec, pid);
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-    unique_id_rec_size[2] = sizeof(cur_unique_id.pid);
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-    unique_id_rec_offset[3] = APR_OFFSETOF(unique_id_rec, counter);
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-    unique_id_rec_size[3] = sizeof(cur_unique_id.counter);
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-    unique_id_rec_offset[4] = APR_OFFSETOF(unique_id_rec, thread_index);
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-    unique_id_rec_size[4] = sizeof(cur_unique_id.thread_index);
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+    unique_id_rec_offset[1] = APR_OFFSETOF(unique_id_rec, root);
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+    unique_id_rec_size[1] = sizeof(cur_unique_id.root);
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+    unique_id_rec_offset[2] = APR_OFFSETOF(unique_id_rec, counter);
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+    unique_id_rec_size[2] = sizeof(cur_unique_id.counter);
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+    unique_id_rec_offset[3] = APR_OFFSETOF(unique_id_rec, thread_index);
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+    unique_id_rec_size[3] = sizeof(cur_unique_id.thread_index);
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     unique_id_rec_total_size = unique_id_rec_size[0] + unique_id_rec_size[1] +
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-                               unique_id_rec_size[2] + unique_id_rec_size[3] +
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-                               unique_id_rec_size[4];
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+                               unique_id_rec_size[2] + unique_id_rec_size[3];
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     /*
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      * Calculate the size of the structure when encoded.
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      */
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     unique_id_rec_size_uu = (unique_id_rec_total_size*8+5)/6;
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-    /*
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-     * Now get the global in_addr.  Note that it is not sufficient to use one
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-     * of the addresses from the main_server, since those aren't as likely to
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-     * be unique as the physical address of the machine
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-     */
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-    if ((rv = apr_gethostname(str, sizeof(str) - 1, p)) != APR_SUCCESS) {
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-        ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01563)
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-          "unable to find hostname of the server");
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-        return HTTP_INTERNAL_SERVER_ERROR;
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-    }
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-
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-    if ((rv = apr_sockaddr_info_get(&sockaddr, str, AF_INET, 0, 0, p)) == APR_SUCCESS) {
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-        global_in_addr = sockaddr->sa.sin.sin_addr.s_addr;
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-    }
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-    else {
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-        ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01564)
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-                    "unable to find IPv4 address of \"%s\"", str);
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-#if APR_HAVE_IPV6
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-        if ((rv = apr_sockaddr_info_get(&sockaddr, str, AF_INET6, 0, 0, p)) == APR_SUCCESS) {
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-            memcpy(&global_in_addr,
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-                   (char *)sockaddr->ipaddr_ptr + sockaddr->ipaddr_len - sizeof(global_in_addr),
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-                   sizeof(global_in_addr));
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-            ap_log_error(APLOG_MARK, APLOG_ALERT, rv, main_server, APLOGNO(01565)
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-                         "using low-order bits of IPv6 address "
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-                         "as if they were unique");
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-        }
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-        else
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-#endif
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-        return HTTP_INTERNAL_SERVER_ERROR;
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-    }
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-
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-    apr_sockaddr_ip_get(&ipaddrstr, sockaddr);
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-    ap_log_error(APLOG_MARK, APLOG_INFO, 0, main_server, APLOGNO(01566) "using ip addr %s",
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-                 ipaddrstr);
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-
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-    /*
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-     * If the server is pummelled with restart requests we could possibly end
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-     * up in a situation where we're starting again during the same second
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-     * that has been used in previous identifiers.  Avoid that situation.
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-     *
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-     * In truth, for this to actually happen not only would it have to restart
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-     * in the same second, but it would have to somehow get the same pids as
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-     * one of the other servers that was running in that second. Which would
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-     * mean a 64k wraparound on pids ... not very likely at all.
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-     *
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-     * But protecting against it is relatively cheap.  We just sleep into the
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-     * next second.
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-     */
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-    apr_sleep(apr_time_from_sec(1) - apr_time_usec(apr_time_now()));
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     return OK;
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 }
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 static void unique_id_child_init(apr_pool_t *p, server_rec *s)
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 {
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-    pid_t pid;
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-
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-    /*
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-     * Note that we use the pid because it's possible that on the same
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-     * physical machine there are multiple servers (i.e. using Listen). But
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-     * it's guaranteed that none of them will share the same pids between
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-     * children.
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-     *
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-     * XXX: for multithread this needs to use a pid/tid combo and probably
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-     * needs to be expanded to 32 bits
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-     */
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-    pid = getpid();
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-    cur_unique_id.pid = pid;
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-
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-    /*
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-     * Test our assumption that the pid is 32-bits.  It's possible that
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-     * 64-bit machines will declare pid_t to be 64 bits but only use 32
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-     * of them.  It would have been really nice to test this during
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-     * global_init ... but oh well.
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-     */
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-    if ((pid_t)cur_unique_id.pid != pid) {
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-        ap_log_error(APLOG_MARK, APLOG_CRIT, 0, s, APLOGNO(01567)
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-                    "oh no! pids are greater than 32-bits!  I'm broken!");
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-    }
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-
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-    cur_unique_id.in_addr = global_in_addr;
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+    ap_random_insecure_bytes(&cur_unique_id.root,
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+                             sizeof(cur_unique_id.root));
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     /*
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      * If we use 0 as the initial counter we have a little less protection
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@@ -253,13 +170,6 @@
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      */
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     ap_random_insecure_bytes(&cur_unique_id.counter,
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                              sizeof(cur_unique_id.counter));
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-
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-    /*
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-     * We must always use network ordering for these bytes, so that
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-     * identifiers are comparable between machines of different byte
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-     * orderings.  Note in_addr is already in network order.
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-     */
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-    cur_unique_id.pid = htonl(cur_unique_id.pid);
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 }
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 /* NOTE: This is *NOT* the same encoding used by base64encode ... the last two
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@@ -291,10 +201,8 @@
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     unsigned short counter;
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     int i,j,k;
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-    new_unique_id.in_addr = cur_unique_id.in_addr;
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-    new_unique_id.pid = cur_unique_id.pid;
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+    memcpy(&new_unique_id.root, &cur_unique_id.root, ROOT_SIZE);
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     new_unique_id.counter = cur_unique_id.counter;
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-
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     new_unique_id.stamp = htonl((unsigned int)apr_time_sec(r->request_time));
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     new_unique_id.thread_index = htonl((unsigned int)r->connection->id);
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