vhost: allow fd adoption

CMakeLists.txt

@@ -662,6 +662,8 @@ CHECK_C_SOURCE_COMPILES("#include <inttypes.h>\nvoid main(void) { while(1) ; } v
 CHECK_C_SOURCE_COMPILES("#include <sys/resource.h>\nvoid main(void) { while(1) ; } void xxexit(void){}" LWS_HAVE_SYS_RESOURCE_H)
 CHECK_C_SOURCE_COMPILES("#include <linux/ipv6.h>\nvoid main(void) { while(1) ; } void xxexit(void){}" LWS_HAVE_LINUX_IPV6_H)
 CHECK_C_SOURCE_COMPILES("#include <net/ethernet.h>\nvoid main(void) { while(1) ; } void xxexit(void){}" LWS_HAVE_NET_ETHERNET_H)
+CHECK_C_SOURCE_COMPILES("#include <systemd/sd-daemon.h>\nvoid main(void) { while(1) ; } void xxexit(void){}" LWS_HAVE_SYSTEMD_H)
+
 
 
 if (LWS_EXT_PTHREAD_INCLUDE_DIR)

cmake/lws_config.h.in

@@ -242,6 +242,7 @@
 #cmakedefine LWS_WITH_SYS_METRICS
 #cmakedefine LWS_WITH_SYS_NTPCLIENT
 #cmakedefine LWS_WITH_SYS_STATE
+#cmakedefine LWS_HAVE_SYSTEMD_H
 #cmakedefine LWS_WITHOUT_TEST_SERVER
 #cmakedefine LWS_WITHOUT_TESTAPPS
 #cmakedefine LWS_WITH_THREADPOOL

include/libwebsockets/lws-context-vhost.h

@@ -959,6 +959,14 @@ struct lws_context_creation_info {
 	 * selected default loglevel can then be cleanly overridden using -d 1039 etc
 	 * commandline switch */
 
+	lws_sockfd_type		vh_listen_sockfd;
+	/**< VHOST: 0 for normal vhost listen socket fd creation, if any.
+	 * Nonzero to force the selection of an already-existing fd for the
+	 * vhost's listen socket, which is already prepared.  This is intended
+	 * for an external process having chosen the fd, which cannot then be
+	 * zero.
+	 */
+
 	/* Add new things just above here ---^
 	 * This is part of the ABI, don't needlessly break compatibility
 	 *
@@ -1253,6 +1261,20 @@ lws_context_default_loop_run_destroy(struct lws_context *cx);
 LWS_VISIBLE LWS_EXTERN int
 lws_cmdline_passfail(int argc, const char **argv, int actual);
 
+/**
+ * lws_systemd_inherited_fd() - prepare vhost creation info for systemd exported fd if any
+ *
+ * \param index: 0+ index of exported fd
+ * \param info: info struct to be prepared with related info, if any
+ *
+ * Returns 0 and points info to the related fd, aligning the other information
+ * to the type of fd and port it is bound to, or returns nonzero if no such
+ * inherited fd.
+ */
+LWS_VISIBLE LWS_EXTERN int
+lws_systemd_inherited_fd(unsigned int index,
+			 struct lws_context_creation_info *info);
+
 /**
  * lws_context_is_being_destroyed() - find out if context is being destroyed
  *

lib/plat/unix/CMakeLists.txt

@@ -63,6 +63,12 @@ if (LWS_WITH_NETWORK)
 			list(APPEND SOURCES plat/unix/unix-resolv.c)
 		endif()
 	endif()
+	if (LWS_HAVE_SYSTEMD_H)
+		list(APPEND SOURCES
+			plat/unix/unix-systemd.c
+		)
+		list(APPEND LIB_LIST_AT_END systemd)
+	endif()
 endif()
 	
 if (LWS_WITH_PLUGINS_API)

lib/plat/unix/unix-systemd.c

@@ -0,0 +1,83 @@
+/*
+ * libwebsockets - small server side websockets and web server implementation
+ *
+ * Copyright (C) 2010 - 2024 Andy Green <andy@warmcat.com>
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to
+ * deal in the Software without restriction, including without limitation the
+ * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
+ * sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ */
+
+#if !defined(_GNU_SOURCE)
+#define _GNU_SOURCE
+#endif
+
+#include <sys/socket.h>
+#include <systemd/sd-daemon.h>
+
+#include "private-lib-core.h"
+
+
+int
+lws_systemd_inherited_fd(unsigned int index,
+			 struct lws_context_creation_info *info)
+{
+	unsigned int inherited = (unsigned int)sd_listen_fds(0);
+
+	if (index >= inherited)
+		return -1;
+
+	info->vh_listen_sockfd = (int)(SD_LISTEN_FDS_START + index);
+
+	if (sd_is_socket_unix(info->vh_listen_sockfd, 0, 0, NULL, 0))
+		info->options |= LWS_SERVER_OPTION_UNIX_SOCK;
+
+	if (sd_is_socket_inet(info->vh_listen_sockfd, AF_UNSPEC, 0, 1, 0)) {
+		struct sockaddr_storage addr;
+		socklen_t addrlen = sizeof(addr);
+
+		if (getsockname(info->vh_listen_sockfd,
+				(struct sockaddr *)&addr, &addrlen)) {
+			lwsl_err("%s: getsockname failed for fd %d\n",
+				 __func__, info->vh_listen_sockfd);
+			return -1;
+		}
+
+		switch (((struct sockaddr *)&addr)->sa_family) {
+		case AF_INET:
+			info->port = ntohs(((struct sockaddr_in *)&addr)->sin_port);
+			lwsl_info("%s: inet socket %d\n", __func__, info->port);
+			break;
+		case AF_INET6:
+			info->port = ntohs(((struct sockaddr_in6 *)&addr)->sin6_port);
+			lwsl_info("%s: inet6 socket %d\n", __func__, info->port);
+			break;
+		}
+
+		if (sd_is_socket_inet(info->vh_listen_sockfd, AF_INET6, 0, 1, 0))
+			info->options |= LWS_SERVER_OPTION_IPV6_V6ONLY_MODIFY |
+				         LWS_SERVER_OPTION_IPV6_V6ONLY_VALUE;
+
+		if (sd_is_socket_inet(info->vh_listen_sockfd, AF_INET, 0, 1, 0)) {
+			info->options &= (uint64_t)~(LWS_SERVER_OPTION_IPV6_V6ONLY_MODIFY |
+				         LWS_SERVER_OPTION_IPV6_V6ONLY_VALUE);
+			info->options |= LWS_SERVER_OPTION_DISABLE_IPV6;
+		}
+	}
+
+	return 0;
+}

lib/roles/http/server/server.c

@@ -72,6 +72,10 @@ check_extant(struct lws_dll2 *d, void *user)
 	if (wsi->af != a ->af)
 		return 0;
 
+	if (a->info && a->info->vh_listen_sockfd &&
+	    wsi->desc.sockfd != a->info->vh_listen_sockfd)
+		return 0;
+
 	lwsl_notice(" using listen skt from vhost %s\n", wsi->a.vhost->name);
 
 	return 1;
@@ -107,7 +111,7 @@ deal:
 	if (!san--)
 		return -1;
 
-	if (a->vhost->iface) {
+	if (a->vhost->iface && (!a->info || !a->info->vh_listen_sockfd)) {
 
 		/*
 		 * let's check before we do anything else about the disposition
@@ -183,6 +187,11 @@ done_list:
 				LWS_SERVER_OPTION_FAIL_UPON_UNABLE_TO_BIND ?
 				-1 : 1;
 		}
+	} else {
+		if (a->info && a->info->vh_listen_sockfd) {
+			a->vhost->iface = "inherited";
+			a->vhost->listen_port = a->info->port;
+		}
 	}
 
 	(void)n;
@@ -202,7 +211,10 @@ done_list:
 
 	for (m = 0; m < limit; m++) {
 
-		sockfd = lws_fi(&a->vhost->fic, "listenskt") ?
+		if (a->info && a->info->vh_listen_sockfd)
+			sockfd = dup(a->info->vh_listen_sockfd);
+		else
+			sockfd = lws_fi(&a->vhost->fic, "listenskt") ?
 					LWS_SOCK_INVALID :
 					socket(a->af, SOCK_STREAM, 0);
 
@@ -248,9 +260,11 @@ done_list:
 		 * There will be a separate ipv4 listen socket if that's
 		 * enabled.
 		 */
-		if (a->af == AF_INET6 &&
+		if (a->af == AF_INET6 && (!a->info || !a->info->vh_listen_sockfd) &&
 		    setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
 			       (const void*)&value, sizeof(value)) < 0) {
+			lwsl_err("ipv6 only failed\n");
+
 			compatible_close(sockfd);
 			return -1;
 		}
@@ -267,6 +281,7 @@ done_list:
 		if (n || cx->count_threads > 1) /* ... also implied by threads > 1 */
 			if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEPORT,
 					(const void *)&opt, sizeof(opt)) < 0) {
+				lwsl_err("reuseport failed\n");
 				compatible_close(sockfd);
 				return -1;
 			}
@@ -274,28 +289,30 @@ done_list:
 #endif
 		lws_plat_set_socket_options(a->vhost, sockfd, 0);
 
-		is = lws_socket_bind(a->vhost, NULL, sockfd,
-				     a->vhost->listen_port,
-				     a->vhost->iface, a->af);
+		if (!a->info || !a->info->vh_listen_sockfd) {
+			is = lws_socket_bind(a->vhost, NULL, sockfd,
+					     a->vhost->listen_port,
+					     a->vhost->iface, a->af);
 
-		if (is == LWS_ITOSA_BUSY) {
-			/* treat as fatal */
-			compatible_close(sockfd);
+			if (is == LWS_ITOSA_BUSY) {
+				/* treat as fatal */
+				compatible_close(sockfd);
 
-			return -1;
-		}
+				return -1;
+			}
 
-		/*
-		 * There is a race where the network device may come up and then
-		 * go away and fail here.  So correctly handle unexpected failure
-		 * here despite we earlier confirmed it.
-		 */
-		if (is < 0) {
-			lwsl_info("%s: lws_socket_bind says %d\n", __func__, is);
-			compatible_close(sockfd);
-			if (a->vhost->iface)
-				goto deal;
-			return -1;
+			/*
+			 * There is a race where the network device may come up and then
+			 * go away and fail here.  So correctly handle unexpected failure
+			 * here despite we earlier confirmed it.
+			 */
+			if (is < 0) {
+				lwsl_info("%s: lws_socket_bind says %d\n", __func__, is);
+				compatible_close(sockfd);
+				if (a->vhost->iface)
+					goto deal;
+				return -1;
+			}
 		}
 
 		/*
@@ -373,13 +390,17 @@ done_list:
 			goto bail;
 		}
 
-		if (wsi)
+		if (wsi) {
+			if (a->info && a->info->vh_listen_sockfd)
+				a->vhost->listen_port = a->info->port;
+
 			__lws_lc_tag(a->vhost->context,
 				     &a->vhost->context->lcg[LWSLCG_WSI],
 				     &wsi->lc, "listen|%s|%s|%d",
 				     a->vhost->name,
 				     a->vhost->iface ? a->vhost->iface : "",
 				     (int)a->vhost->listen_port);
+		}
 
 	} /* for each thread able to independently listen */
 
@@ -399,6 +420,7 @@ done_list:
 	return 0;
 
 bail:
+	lwsl_err("%s: bailing\n", __func__);
 	compatible_close(sockfd);
 
 	return -1;