diff --git a/server/listen.c b/server/listen.c

index 1d9be83..f5f7754 100644

--- a/server/listen.c

+++ b/server/listen.c

@@ -34,6 +34,10 @@

 #include <unistd.h>

 #endif

+#ifdef HAVE_SYSTEMD

+#include <systemd/sd-daemon.h>

+#endif

+

 /* we know core's module_index is 0 */

 #undef APLOG_MODULE_INDEX

 #define APLOG_MODULE_INDEX AP_CORE_MODULE_INDEX

@@ -59,9 +63,12 @@ static int ap_listenbacklog;

 static int ap_listencbratio;

 static int send_buffer_size;

 static int receive_buffer_size;

+#ifdef HAVE_SYSTEMD

+static int use_systemd = -1;

+#endif

 /* TODO: make_sock is just begging and screaming for APR abstraction */

-static apr_status_t make_sock(apr_pool_t *p, ap_listen_rec *server)

+static apr_status_t make_sock(apr_pool_t *p, ap_listen_rec *server, int do_bind_listen)

 {

     apr_socket_t *s = server->sd;

     int one = 1;

@@ -94,20 +101,6 @@ static apr_status_t make_sock(apr_pool_t *p, ap_listen_rec *server)

         return stat;

     }

-#if APR_HAVE_IPV6

-    if (server->bind_addr->family == APR_INET6) {

-        stat = apr_socket_opt_set(s, APR_IPV6_V6ONLY, v6only_setting);

-        if (stat != APR_SUCCESS && stat != APR_ENOTIMPL) {

-            ap_log_perror(APLOG_MARK, APLOG_CRIT, stat, p, APLOGNO(00069)

-                          "make_sock: for address %pI, apr_socket_opt_set: "

-                          "(IPV6_V6ONLY)",

-                          server->bind_addr);

-            apr_socket_close(s);

-            return stat;

-        }

-    }

-#endif

-

     /*

      * To send data over high bandwidth-delay connections at full

      * speed we must force the TCP window to open wide enough to keep the

@@ -169,21 +162,37 @@ static apr_status_t make_sock(apr_pool_t *p, ap_listen_rec *server)

     }

 #endif

-    if ((stat = apr_socket_bind(s, server->bind_addr)) != APR_SUCCESS) {

-        ap_log_perror(APLOG_MARK, APLOG_STARTUP|APLOG_CRIT, stat, p, APLOGNO(00072)

-                      "make_sock: could not bind to address %pI",

-                      server->bind_addr);

-        apr_socket_close(s);

-        return stat;

-    }

+    if (do_bind_listen) {

+#if APR_HAVE_IPV6

+        if (server->bind_addr->family == APR_INET6) {

+            stat = apr_socket_opt_set(s, APR_IPV6_V6ONLY, v6only_setting);

+            if (stat != APR_SUCCESS && stat != APR_ENOTIMPL) {

+                ap_log_perror(APLOG_MARK, APLOG_CRIT, stat, p, APLOGNO(00069)

+                              "make_sock: for address %pI, apr_socket_opt_set: "

+                              "(IPV6_V6ONLY)",

+                              server->bind_addr);

+                apr_socket_close(s);

+                return stat;

+            }

+        }

+#endif

-    if ((stat = apr_socket_listen(s, ap_listenbacklog)) != APR_SUCCESS) {

-        ap_log_perror(APLOG_MARK, APLOG_STARTUP|APLOG_ERR, stat, p, APLOGNO(00073)

-                      "make_sock: unable to listen for connections "

-                      "on address %pI",

-                      server->bind_addr);

-        apr_socket_close(s);

-        return stat;

+        if ((stat = apr_socket_bind(s, server->bind_addr)) != APR_SUCCESS) {

+            ap_log_perror(APLOG_MARK, APLOG_STARTUP|APLOG_CRIT, stat, p, APLOGNO(00072)

+                          "make_sock: could not bind to address %pI",

+                          server->bind_addr);

+            apr_socket_close(s);

+            return stat;

+        }

+

+        if ((stat = apr_socket_listen(s, ap_listenbacklog)) != APR_SUCCESS) {

+            ap_log_perror(APLOG_MARK, APLOG_STARTUP|APLOG_ERR, stat, p, APLOGNO(00073)

+                          "make_sock: unable to listen for connections "

+                          "on address %pI",

+                          server->bind_addr);

+            apr_socket_close(s);

+            return stat;

+        }

     }

 #ifdef WIN32

@@ -277,6 +286,124 @@ static apr_status_t close_listeners_on_exec(void *v)

     return APR_SUCCESS;

 }

+

+#ifdef HAVE_SYSTEMD

+

+static int find_systemd_socket(process_rec * process, apr_port_t port) {

+    int fdcount, fd;

+    int sdc = sd_listen_fds(0);

+

+    if (sdc < 0) {

+        ap_log_perror(APLOG_MARK, APLOG_CRIT, sdc, process->pool, APLOGNO(02486)

+                      "find_systemd_socket: Error parsing enviroment, sd_listen_fds returned %d",

+                      sdc);

+        return -1;

+    }

+

+    if (sdc == 0) {

+        ap_log_perror(APLOG_MARK, APLOG_CRIT, sdc, process->pool, APLOGNO(02487)

+                      "find_systemd_socket: At least one socket must be set.");

+        return -1;

+    }

+

+    fdcount = atoi(getenv("LISTEN_FDS"));

+    for (fd = SD_LISTEN_FDS_START; fd < SD_LISTEN_FDS_START + fdcount; fd++) {

+        if (sd_is_socket_inet(fd, 0, 0, -1, port) > 0) {

+            return fd;

+        }

+    }

+

+    return -1;

+}

+

+static apr_status_t alloc_systemd_listener(process_rec * process,

+                                           int fd, const char *proto,

+                                           ap_listen_rec **out_rec)

+{

+    apr_status_t rv;

+    struct sockaddr sa;

+    socklen_t len = sizeof(struct sockaddr);

+    apr_os_sock_info_t si;

+    ap_listen_rec *rec;

+    *out_rec = NULL;

+

+    memset(&si, 0, sizeof(si));

+

+    rv = getsockname(fd, &sa, &len;;

+

+    if (rv != 0) {

+        rv = apr_get_netos_error();

+        ap_log_perror(APLOG_MARK, APLOG_CRIT, rv, process->pool, APLOGNO(02489)

+                      "getsockname on %d failed.", fd);

+        return rv;

+    }

+

+    si.os_sock = &fd;

+    si.family = sa.sa_family;

+    si.local = &sa;

+    si.type = SOCK_STREAM;

+    si.protocol = APR_PROTO_TCP;

+

+    rec = apr_palloc(process->pool, sizeof(ap_listen_rec));

+    rec->active = 0;

+    rec->next = 0;

+

+

+    rv = apr_os_sock_make(&rec->sd, &si, process->pool);

+    if (rv != APR_SUCCESS) {

+        ap_log_perror(APLOG_MARK, APLOG_CRIT, rv, process->pool, APLOGNO(02490)

+                      "apr_os_sock_make on %d failed.", fd);

+        return rv;

+    }

+

+    rv = apr_socket_addr_get(&rec->bind_addr, APR_LOCAL, rec->sd);

+    if (rv != APR_SUCCESS) {

+        ap_log_perror(APLOG_MARK, APLOG_CRIT, rv, process->pool, APLOGNO(02491)

+                      "apr_socket_addr_get on %d failed.", fd);

+        return rv;

+    }

+

+    rec->protocol = apr_pstrdup(process->pool, proto);

+

+    *out_rec = rec;

+

+    return make_sock(process->pool, rec, 0);

+}

+

+static const char *set_systemd_listener(process_rec *process, apr_port_t port,

+                                        const char *proto)

+{

+    ap_listen_rec *last, *new;

+    apr_status_t rv;

+    int fd = find_systemd_socket(process, port);

+    if (fd < 0) {

+        return "Systemd socket activation is used, but this port is not "

+                "configured in systemd";

+    }

+

+    last = ap_listeners;

+    while (last && last->next) {

+        last = last->next;

+    }

+

+    rv = alloc_systemd_listener(process, fd, proto, &new;;

+    if (rv != APR_SUCCESS) {

+        return "Failed to setup socket passed by systemd using socket activation";

+    }

+

+    if (last == NULL) {

+        ap_listeners = last = new;

+    }

+    else {

+        last->next = new;

+        last = new;

+    }

+

+    return NULL;

+}

+

+#endif /* HAVE_SYSTEMD */

+

 static const char *alloc_listener(process_rec *process, char *addr,

                                   apr_port_t port, const char* proto,

                                   void *slave)

@@ -479,7 +606,7 @@ static int open_listeners(apr_pool_t *pool)

                 }

             }

 #endif

-            if (make_sock(pool, lr) == APR_SUCCESS) {

+            if (make_sock(pool, lr, 1) == APR_SUCCESS) {

                 ++num_open;

             }

             else {

@@ -591,8 +718,28 @@ AP_DECLARE(int) ap_setup_listeners(server_rec *s)

         }

     }

-    if (open_listeners(s->process->pool)) {

-        return 0;

+#ifdef HAVE_SYSTEMD

+    if (use_systemd) {

+        const char *userdata_key = "ap_open_systemd_listeners";

+        void *data;

+        /* clear the enviroment on our second run

+        * so that none of our future children get confused.

+        */

+        apr_pool_userdata_get(&data, userdata_key, s->process->pool);

+        if (!data) {

+            apr_pool_userdata_set((const void *)1, userdata_key,

+                                apr_pool_cleanup_null, s->process->pool);

+        }

+        else {

+            sd_listen_fds(1);

+        }

+    }

+    else

+#endif

+    {

+        if (open_listeners(s->process->pool)) {

+            return 0;

+        }

     }

     for (lr = ap_listeners; lr; lr = lr->next) {

@@ -682,7 +829,7 @@ AP_DECLARE(apr_status_t) ap_duplicate_listeners(apr_pool_t *p, server_rec *s,

                             duplr->bind_addr);

                 return stat;

             }

-            make_sock(p, duplr);

+            make_sock(p, duplr, 1);

 #if AP_NONBLOCK_WHEN_MULTI_LISTEN

             use_nonblock = (ap_listeners && ap_listeners->next);

             stat = apr_socket_opt_set(duplr->sd, APR_SO_NONBLOCK, use_nonblock);

@@ -809,6 +956,11 @@ AP_DECLARE_NONSTD(const char *) ap_set_listener(cmd_parms *cmd, void *dummy,

     if (argc < 1 || argc > 2) {

         return "Listen requires 1 or 2 arguments.";

     }

+#ifdef HAVE_SYSTEMD

+    if (use_systemd == -1) {

+        use_systemd = sd_listen_fds(0) > 0;

+    }

+#endif

     rv = apr_parse_addr_port(&host, &scope_id, &port, argv[0], cmd->pool);

     if (rv != APR_SUCCESS) {

@@ -840,6 +992,12 @@ AP_DECLARE_NONSTD(const char *) ap_set_listener(cmd_parms *cmd, void *dummy,

         ap_str_tolower(proto);

     }

+#ifdef HAVE_SYSTEMD

+    if (use_systemd) {

+        return set_systemd_listener(cmd->server->process, port, proto);

+    }

+#endif

+

     return alloc_listener(cmd->server->process, host, port, proto, NULL);

 }