Remove libsystemd dependency from main httpd binary

Until this change httpd was linking libsystemd to the main httpd binary. If you want to run lightweight version of httpd in container, sometimes you just want to install
httpd binary with as little dependencies as possible to make container small in size and do not pull uncencessary dependencies and libraries.

This change will move all systemd library calls from listen.c to mod_systemd module and remove systemd linking from the main httpd bin.
Fixed mixed declaration and wrongly declared variable.

Submitted by: Luboš Uhliarik <luhliari redhat.com>

Github: closes #312

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1899784 13f79535-47bb-0310-9956-ffa450edef68
(cherry picked from commit db0631e)

Author: notroj

changes-entries/systemd_socket_activation.txt

@@ -0,0 +1,3 @@
+  *) mod_systemd: Systemd socket activation can now be enabled at
+     build time but disabled at run time, if mod_systemd is not
+     loaded.  [Lubos Uhliarik <luhliari redhat.com>]

include/ap_listen.h

@@ -29,6 +29,7 @@
 #include "apr_network_io.h"
 #include "httpd.h"
 #include "http_config.h"
+#include "apr_optional.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -143,6 +144,15 @@ AP_DECLARE_NONSTD(const char *) ap_set_receive_buffer_size(cmd_parms *cmd,
                                                            void *dummy,
                                                            const char *arg);
 
+#ifdef HAVE_SYSTEMD
+APR_DECLARE_OPTIONAL_FN(int,
+                        ap_find_systemd_socket, (process_rec *, apr_port_t));
+
+APR_DECLARE_OPTIONAL_FN(int,
+                        ap_systemd_listen_fds, (int));
+#endif
+
+
 #define LISTEN_COMMANDS \
 AP_INIT_TAKE1("ListenBacklog", ap_set_listenbacklog, NULL, RSRC_CONF, \
   "Maximum length of the queue of pending connections, as used by listen(2)"), \

modules/arch/unix/mod_systemd.c

@@ -34,6 +34,12 @@
 #include <unistd.h>
 #endif
 
+APR_DECLARE_OPTIONAL_FN(int,
+                        ap_find_systemd_socket, (process_rec *, apr_port_t));
+
+APR_DECLARE_OPTIONAL_FN(int,
+                        ap_systemd_listen_fds, (int));
+
 static int systemd_pre_config(apr_pool_t *pconf, apr_pool_t *plog,
                               apr_pool_t *ptemp)
 {
@@ -96,8 +102,42 @@ static int systemd_monitor(apr_pool_t *p, server_rec *s)
     return DECLINED;
 }
 
+static int ap_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 int ap_systemd_listen_fds(int unset_environment){
+    return sd_listen_fds(unset_environment);
+}
+
 static void systemd_register_hooks(apr_pool_t *p)
 {
+    APR_REGISTER_OPTIONAL_FN(ap_systemd_listen_fds);
+    APR_REGISTER_OPTIONAL_FN(ap_find_systemd_socket);
+
     /* Enable ap_extended_status. */
     ap_hook_pre_config(systemd_pre_config, NULL, NULL, APR_HOOK_LAST);
     /* Signal service is ready. */

server/listen.c

@@ -283,34 +283,7 @@ static apr_status_t close_listeners_on_exec(void *v)
     return APR_SUCCESS;
 }
 
-#ifdef AP_SYSTEMD_SUPPORT
-
-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;
-}
+#ifdef HAVE_SYSTEMD
 
 static apr_status_t alloc_systemd_listener(process_rec * process,
                                            int fd, const char *proto,
@@ -371,7 +344,16 @@ static const char *set_systemd_listener(process_rec *process, apr_port_t port,
 {
     ap_listen_rec *last, *new;
     apr_status_t rv;
-    int fd = find_systemd_socket(process, port);
+    APR_OPTIONAL_FN_TYPE(ap_find_systemd_socket) *find_systemd_socket;
+    int fd;
+
+    find_systemd_socket = APR_RETRIEVE_OPTIONAL_FN(ap_find_systemd_socket);
+
+    if (!find_systemd_socket)
+       return "Systemd socket activation is used, but mod_systemd is probably "
+               "not loaded";
+
+    fd = find_systemd_socket(process, port);
     if (fd < 0) {
         return "Systemd socket activation is used, but this port is not "
                 "configured in systemd";
@@ -397,7 +379,6 @@ static const char *set_systemd_listener(process_rec *process, apr_port_t port,
 
     return NULL;
 }
-
 #endif /* HAVE_SYSTEMD */
 
 /* Returns non-zero if socket address SA matches hostname, port and
@@ -737,6 +718,9 @@ AP_DECLARE(int) ap_setup_listeners(server_rec *s)
     int num_listeners = 0;
     const char* proto;
     int found;
+#ifdef HAVE_SYSTEMD
+    APR_OPTIONAL_FN_TYPE(ap_systemd_listen_fds) *systemd_listen_fds;
+#endif
 
     for (ls = s; ls; ls = ls->next) {
         proto = ap_get_server_protocol(ls);
@@ -777,7 +761,10 @@ AP_DECLARE(int) ap_setup_listeners(server_rec *s)
                                 apr_pool_cleanup_null, s->process->pool);
         }
         else {
-            sd_listen_fds(1);
+            systemd_listen_fds = APR_RETRIEVE_OPTIONAL_FN(ap_systemd_listen_fds);
+            if (systemd_listen_fds != NULL) {
+                systemd_listen_fds(1);
+            }
         }        
     }
     else
@@ -1006,6 +993,9 @@ AP_DECLARE_NONSTD(const char *) ap_set_listener(cmd_parms *cmd, void *dummy,
     apr_port_t port;
     apr_status_t rv;
     const char *err = ap_check_cmd_context(cmd, GLOBAL_ONLY);
+#ifdef HAVE_SYSTEMD
+    APR_OPTIONAL_FN_TYPE(ap_systemd_listen_fds) *systemd_listen_fds;
+#endif
 
     if (err != NULL) {
         return err;
@@ -1016,7 +1006,12 @@ AP_DECLARE_NONSTD(const char *) ap_set_listener(cmd_parms *cmd, void *dummy,
     }
 #ifdef HAVE_SYSTEMD
     if (use_systemd == -1) {
-        use_systemd = sd_listen_fds(0) > 0;
+        systemd_listen_fds = APR_RETRIEVE_OPTIONAL_FN(ap_systemd_listen_fds);
+        if (systemd_listen_fds != NULL) {
+            use_systemd = systemd_listen_fds(0) > 0;
+        } else {
+            use_systemd = 0;
+        }
     }
 #endif