systemd: add support for acquiring socket from systemd

5 files changed, 793 insertions, 58 deletions

diff --git a/avahi-daemon/Makefile.am b/avahi-daemon/Makefile.am
index 0aac0fc..c406a62 100644
--- a/avahi-daemon/Makefile.am
+++ b/avahi-daemon/Makefile.am
@@ -1,7 +1,7 @@
 # $Id$
 #
 # This file is part of avahi.
-# 
+#
 # avahi is free software; you can redistribute it and/or modify it
 # under the terms of the GNU Lesser General Public License as
 # published by the Free Software Foundation; either version 2 of the
@@ -53,6 +53,7 @@ avahi_daemon_SOURCES = \
 	static-hosts.c static-hosts.h \
 	ini-file-parser.c ini-file-parser.h \
 	setproctitle.c setproctitle.h \
+	sd-daemon.h sd-daemon.c \
 	../avahi-client/check-nss.c
 
 avahi_daemon_CFLAGS = $(AM_CFLAGS) $(LIBDAEMON_CFLAGS) $(XML_CFLAGS)
@@ -63,7 +64,7 @@ ini_file_parser_test_SOURCES = \
 	ini-file-parser-test.c
 
 ini_file_parser_test_CFLAGS = $(AM_CFLAGS)
-ini_file_parser_test_LDADD = $(AM_LDADD) ../avahi-common/libavahi-common.la ../avahi-core/libavahi-core.la 
+ini_file_parser_test_LDADD = $(AM_LDADD) ../avahi-common/libavahi-common.la ../avahi-core/libavahi-core.la
 
 pkgsysconf_DATA = \
 	avahi-daemon.conf \
@@ -163,3 +164,7 @@ xmllint:
 
 install-data-local:
 	test -z "$(localstatedir)/run" || $(mkdir_p) "$(DESTDIR)$(localstatedir)/run"
+
+update-systemd:
+	curl http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.c > sd-daemon.c
+	curl http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.h > sd-daemon.h
diff --git a/avahi-daemon/main.c b/avahi-daemon/main.c
index c3cbb0e..a32c706 100644
--- a/avahi-daemon/main.c
+++ b/avahi-daemon/main.c
@@ -79,6 +79,7 @@
 #include "static-services.h"
 #include "static-hosts.h"
 #include "ini-file-parser.h"
+#include "sd-daemon.h"
 
 #ifdef HAVE_DBUS
 #include "dbus-protocol.h"
@@ -1455,10 +1456,11 @@ int main(int argc, char *argv[]) {
         if (config.use_syslog || config.daemonize)
             daemon_log_use = DAEMON_LOG_SYSLOG;
 
-        if (daemon_close_all(-1) < 0) {
-            avahi_log_error("Failed to close remaining file descriptors: %s", strerror(errno));
-            goto finish;
-        }
+        if (sd_listen_fds(0) <= 0)
+            if (daemon_close_all(-1) < 0) {
+                avahi_log_error("Failed to close remaining file descriptors: %s", strerror(errno));
+                goto finish;
+            }
 
         if (make_runtime_dir() < 0)
             goto finish;
diff --git a/avahi-daemon/sd-daemon.c b/avahi-daemon/sd-daemon.c
new file mode 100644
index 0000000..cb568b5
--- /dev/null
+++ b/avahi-daemon/sd-daemon.c
@@ -0,0 +1,448 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+/***
+  Copyright 2010 Lennart Poettering
+
+  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.
+***/
+
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <sys/fcntl.h>
+#include <netinet/in.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <unistd.h>
+#include <string.h>
+#include <stdarg.h>
+#include <stdio.h>
+
+#include "sd-daemon.h"
+
+int sd_listen_fds(int unset_environment) {
+
+#if defined(DISABLE_SYSTEMD) || !defined(__linux__)
+        return 0;
+#else
+        int r, fd;
+        const char *e;
+        char *p = NULL;
+        unsigned long l;
+
+        if (!(e = getenv("LISTEN_PID"))) {
+                r = 0;
+                goto finish;
+        }
+
+        errno = 0;
+        l = strtoul(e, &p, 10);
+
+        if (errno != 0) {
+                r = -errno;
+                goto finish;
+        }
+
+        if (!p || *p || l <= 0) {
+                r = -EINVAL;
+                goto finish;
+        }
+
+        /* Is this for us? */
+        if (getpid() != (pid_t) l) {
+                r = 0;
+                goto finish;
+        }
+
+        if (!(e = getenv("LISTEN_FDS"))) {
+                r = 0;
+                goto finish;
+        }
+
+        errno = 0;
+        l = strtoul(e, &p, 10);
+
+        if (errno != 0) {
+                r = -errno;
+                goto finish;
+        }
+
+        if (!p || *p) {
+                r = -EINVAL;
+                goto finish;
+        }
+
+        for (fd = SD_LISTEN_FDS_START; fd < SD_LISTEN_FDS_START + (int) l; fd ++) {
+                int flags;
+
+                if ((flags = fcntl(fd, F_GETFD)) < 0) {
+                        r = -errno;
+                        goto finish;
+                }
+
+                if (flags & FD_CLOEXEC)
+                        continue;
+
+                if (fcntl(fd, F_SETFD, flags | FD_CLOEXEC) < 0) {
+                        r = -errno;
+                        goto finish;
+                }
+        }
+
+        r = (int) l;
+
+finish:
+        if (unset_environment) {
+                unsetenv("LISTEN_PID");
+                unsetenv("LISTEN_FDS");
+        }
+
+        return r;
+#endif
+}
+
+int sd_is_fifo(int fd, const char *path) {
+        struct stat st_fd;
+
+        if (fd < 0)
+                return -EINVAL;
+
+        memset(&st_fd, 0, sizeof(st_fd));
+        if (fstat(fd, &st_fd) < 0)
+                return -errno;
+
+        if (!S_ISFIFO(st_fd.st_mode))
+                return 0;
+
+        if (path) {
+                struct stat st_path;
+
+                memset(&st_path, 0, sizeof(st_path));
+                if (fstat(fd, &st_path) < 0) {
+
+                        if (errno == ENOENT || errno == ENOTDIR)
+                                return 0;
+
+                        return -errno;
+                }
+
+                return
+                        st_path.st_dev == st_fd.st_dev &&
+                        st_path.st_ino == st_fd.st_ino;
+        }
+
+        return 1;
+}
+
+static int sd_is_socket_internal(int fd, int type, int listening) {
+        struct stat st_fd;
+
+        if (fd < 0 || type < 0)
+                return -EINVAL;
+
+        if (fstat(fd, &st_fd) < 0)
+                return -errno;
+
+        if (!S_ISSOCK(st_fd.st_mode))
+                return 0;
+
+        if (type != 0) {
+                int other_type = 0;
+                socklen_t l = sizeof(other_type);
+
+                if (getsockopt(fd, SOL_SOCKET, SO_TYPE, &other_type, &l) < 0)
+                        return -errno;
+
+                if (l != sizeof(other_type))
+                        return -EINVAL;
+
+                if (other_type != type)
+                        return 0;
+        }
+
+        if (listening >= 0) {
+                int accepting = 0;
+                socklen_t l = sizeof(accepting);
+
+                if (getsockopt(fd, SOL_SOCKET, SO_ACCEPTCONN, &accepting, &l) < 0)
+                        return -errno;
+
+                if (l != sizeof(accepting))
+                        return -EINVAL;
+
+                if (!accepting != !listening)
+                        return 0;
+        }
+
+        return 1;
+}
+
+union sockaddr_union {
+        struct sockaddr sa;
+        struct sockaddr_in in4;
+        struct sockaddr_in6 in6;
+        struct sockaddr_un un;
+        struct sockaddr_storage storage;
+};
+
+int sd_is_socket(int fd, int family, int type, int listening) {
+        int r;
+
+        if (family < 0)
+                return -EINVAL;
+
+        if ((r = sd_is_socket_internal(fd, type, listening)) <= 0)
+                return r;
+
+        if (family > 0) {
+                union sockaddr_union sockaddr;
+                socklen_t l;
+
+                memset(&sockaddr, 0, sizeof(sockaddr));
+                l = sizeof(sockaddr);
+
+                if (getsockname(fd, &sockaddr.sa, &l) < 0)
+                        return -errno;
+
+                if (l < sizeof(sa_family_t))
+                        return -EINVAL;
+
+                return sockaddr.sa.sa_family == family;
+        }
+
+        return 1;
+}
+
+int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port) {
+        union sockaddr_union sockaddr;
+        socklen_t l;
+        int r;
+
+        if (family != 0 && family != AF_INET && family != AF_INET6)
+                return -EINVAL;
+
+        if ((r = sd_is_socket_internal(fd, type, listening)) <= 0)
+                return r;
+
+        memset(&sockaddr, 0, sizeof(sockaddr));
+        l = sizeof(sockaddr);
+
+        if (getsockname(fd, &sockaddr.sa, &l) < 0)
+                return -errno;
+
+        if (l < sizeof(sa_family_t))
+                return -EINVAL;
+
+        if (sockaddr.sa.sa_family != AF_INET &&
+            sockaddr.sa.sa_family != AF_INET6)
+                return 0;
+
+        if (family > 0)
+                if (sockaddr.sa.sa_family != family)
+                        return 0;
+
+        if (port > 0) {
+                if (sockaddr.sa.sa_family == AF_INET) {
+                        if (l < sizeof(struct sockaddr_in))
+                                return -EINVAL;
+
+                        return htons(port) == sockaddr.in4.sin_port;
+                } else {
+                        if (l < sizeof(struct sockaddr_in6))
+                                return -EINVAL;
+
+                        return htons(port) == sockaddr.in6.sin6_port;
+                }
+        }
+
+        return 1;
+}
+
+int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) {
+        union sockaddr_union sockaddr;
+        socklen_t l;
+        int r;
+
+        if ((r = sd_is_socket_internal(fd, type, listening)) <= 0)
+                return r;
+
+        memset(&sockaddr, 0, sizeof(sockaddr));
+        l = sizeof(sockaddr);
+
+        if (getsockname(fd, &sockaddr.sa, &l) < 0)
+                return -errno;
+
+        if (l < sizeof(sa_family_t))
+                return -EINVAL;
+
+        if (sockaddr.sa.sa_family != AF_UNIX)
+                return 0;
+
+        if (path) {
+                if (length <= 0)
+                        length = strlen(path);
+
+                if (length <= 0)
+                        /* Unnamed socket */
+                        return l == sizeof(sa_family_t);
+
+                if (path[0])
+                        /* Normal path socket */
+                        return
+                                (l >= sizeof(sa_family_t) + length + 1) &&
+                                memcmp(path, sockaddr.un.sun_path, length+1) == 0;
+                else
+                        /* Abstract namespace socket */
+                        return
+                                (l == sizeof(sa_family_t) + length) &&
+                                memcmp(path, sockaddr.un.sun_path, length) == 0;
+        }
+
+        return 1;
+}
+
+int sd_notify(int unset_environment, const char *state) {
+#if defined(DISABLE_SYSTEMD) || !defined(__linux__)
+        return 0;
+#else
+        int fd = -1, r;
+        struct msghdr msghdr;
+        struct iovec iovec;
+        union sockaddr_union sockaddr;
+        struct ucred *ucred;
+        union {
+                struct cmsghdr cmsghdr;
+                uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
+        } control;
+        const char *e;
+
+        if (!state) {
+                r = -EINVAL;
+                goto finish;
+        }
+
+        if (!(e = getenv("NOTIFY_SOCKET")))
+                return 0;
+
+        /* Must be an abstract socket, or an absolute path */
+        if ((e[0] != '@' && e[0] != '/') || e[1] == 0) {
+                r = -EINVAL;
+                goto finish;
+        }
+
+        if ((fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0)) < 0) {
+                r = -errno;
+                goto finish;
+        }
+
+        memset(&sockaddr, 0, sizeof(sockaddr));
+        sockaddr.sa.sa_family = AF_UNIX;
+        strncpy(sockaddr.un.sun_path, e, sizeof(sockaddr.un.sun_path));
+
+        if (sockaddr.un.sun_path[0] == '@')
+                sockaddr.un.sun_path[0] = 0;
+
+        memset(&iovec, 0, sizeof(iovec));
+        iovec.iov_base = (char*) state;
+        iovec.iov_len = strlen(state);
+
+        memset(&control, 0, sizeof(control));
+        control.cmsghdr.cmsg_level = SOL_SOCKET;
+        control.cmsghdr.cmsg_type = SCM_CREDENTIALS;
+        control.cmsghdr.cmsg_len = CMSG_LEN(sizeof(struct ucred));
+
+        ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
+        ucred->pid = getpid();
+        ucred->uid = getuid();
+        ucred->gid = getgid();
+
+        memset(&msghdr, 0, sizeof(msghdr));
+        msghdr.msg_name = &sockaddr;
+        msghdr.msg_namelen = sizeof(struct sockaddr_un);
+        msghdr.msg_iov = &iovec;
+        msghdr.msg_iovlen = 1;
+        msghdr.msg_control = &control;
+        msghdr.msg_controllen = control.cmsghdr.cmsg_len;
+
+        if (sendmsg(fd, &msghdr, MSG_NOSIGNAL) < 0) {
+                r = -errno;
+                goto finish;
+        }
+
+        r = 1;
+
+finish:
+        if (unset_environment)
+                unsetenv("NOTIFY_SOCKET");
+
+        if (fd >= 0)
+                close(fd);
+
+        return r;
+#endif
+}
+
+int sd_notifyf(int unset_environment, const char *format, ...) {
+#if defined(DISABLE_SYSTEMD) || !defined(__linux__)
+        return 0;
+#else
+        va_list ap;
+        char *p = NULL;
+        int r;
+
+        va_start(ap, format);
+        r = vasprintf(&p, format, ap);
+        va_end(ap);
+
+        if (r < 0 || !p)
+                return -ENOMEM;
+
+        r = sd_notify(unset_environment, p);
+        free(p);
+
+        return r;
+#endif
+}
+
+int sd_booted(void) {
+#if defined(DISABLE_SYSTEMD) || !defined(__linux__)
+        return 0;
+#else
+
+        struct stat a, b;
+
+        /* We simply test whether the systemd cgroup hierarchy is
+         * mounted */
+
+        if (lstat("/cgroup", &a) < 0)
+                return 0;
+
+        if (lstat("/cgroup/systemd", &b) < 0)
+                return 0;
+
+        return a.st_dev != b.st_dev;
+#endif
+}
diff --git a/avahi-daemon/sd-daemon.h b/avahi-daemon/sd-daemon.h
new file mode 100644
index 0000000..fd6221f
--- /dev/null
+++ b/avahi-daemon/sd-daemon.h
@@ -0,0 +1,257 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#ifndef foosddaemonhfoo
+#define foosddaemonhfoo
+
+/***
+  Copyright 2010 Lennart Poettering
+
+  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.
+***/
+
+#include <sys/types.h>
+#include <inttypes.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*
+  Reference implementation of a few systemd related interfaces for
+  writing daemons. These interfaces are trivial to implement. To
+  simplify porting we provide this reference implementation.
+  Applications are welcome to reimplement the algorithms described
+  here if they do not want to include these two source files.
+
+  The following functionality is provided:
+
+  - Support for logging with log levels on stderr
+  - File descriptor passing for socket-based activation
+  - Daemon startup and status notification
+  - Detection of systemd boots
+
+  You may compile this with -DDISABLE_SYSTEMD to disable systemd
+  support. This makes all those calls NOPs that are directly related to
+  systemd (i.e. only sd_is_xxx() will stay useful).
+
+  Since this is drop-in code we don't want any of our symbols to be
+  exported in any case. Hence we declare hidden visibility for all of
+  them.
+
+  You may find an up-to-date version of these source files online:
+
+  http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.h
+  http://cgit.freedesktop.org/systemd/plain/src/sd-daemon.c
+
+  This should compile on non-Linux systems, too, but with the
+  exception of the sd_is_xxx() calls all functions will become NOPs.
+
+  See sd-daemon(7) for more information.
+*/
+
+#if __GNUC__ >= 4
+#define _sd_printf_attr_(a,b) __attribute__ ((format (printf, a, b)))
+#define _sd_hidden_ __attribute__ ((visibility("hidden")))
+#else
+#define _sd_printf_attr_(a,b)
+#define _sd_hidden_
+#endif
+
+/*
+  Log levels for usage on stderr:
+
+          fprintf(stderr, SD_NOTICE "Hello World!\n");
+
+  This is similar to printk() usage in the kernel.
+*/
+#define SD_EMERG   "<0>"  /* system is unusable */
+#define SD_ALERT   "<1>"  /* action must be taken immediately */
+#define SD_CRIT    "<2>"  /* critical conditions */
+#define SD_ERR     "<3>"  /* error conditions */
+#define SD_WARNING "<4>"  /* warning conditions */
+#define SD_NOTICE  "<5>"  /* normal but significant condition */
+#define SD_INFO    "<6>"  /* informational */
+#define SD_DEBUG   "<7>"  /* debug-level messages */
+
+/* The first passed file descriptor is fd 3 */
+#define SD_LISTEN_FDS_START 3
+
+/*
+  Returns how many file descriptors have been passed, or a negative
+  errno code on failure. Optionally, removes the $LISTEN_FDS and
+  $LISTEN_PID file descriptors from the environment (recommended, but
+  problematic in threaded environments). If r is the return value of
+  this function you'll find the file descriptors passed as fds
+  SD_LISTEN_FDS_START to SD_LISTEN_FDS_START+r-1. Returns a negative
+  errno style error code on failure. This function call ensures that
+  the FD_CLOEXEC flag is set for the passed file descriptors, to make
+  sure they are not passed on to child processes. If FD_CLOEXEC shall
+  not be set, the caller needs to unset it after this call for all file
+  descriptors that are used.
+
+  See sd_listen_fds(3) for more information.
+*/
+int sd_listen_fds(int unset_environment) _sd_hidden_;
+
+/*
+  Helper call for identifying a passed file descriptor. Returns 1 if
+  the file descriptor is a FIFO in the file system stored under the
+  specified path, 0 otherwise. If path is NULL a path name check will
+  not be done and the call only verifies if the file descriptor
+  refers to a FIFO. Returns a negative errno style error code on
+  failure.
+
+  See sd_is_fifo(3) for more information.
+*/
+int sd_is_fifo(int fd, const char *path) _sd_hidden_;
+
+/*
+  Helper call for identifying a passed file descriptor. Returns 1 if
+  the file descriptor is a socket of the specified family (AF_INET,
+  ...) and type (SOCK_DGRAM, SOCK_STREAM, ...), 0 otherwise. If
+  family is 0 a socket family check will not be done. If type is 0 a
+  socket type check will not be done and the call only verifies if
+  the file descriptor refers to a socket. If listening is > 0 it is
+  verified that the socket is in listening mode. (i.e. listen() has
+  been called) If listening is == 0 it is verified that the socket is
+  not in listening mode. If listening is < 0 no listening mode check
+  is done. Returns a negative errno style error code on failure.
+
+  See sd_is_socket(3) for more information.
+*/
+int sd_is_socket(int fd, int family, int type, int listening) _sd_hidden_;
+
+/*
+  Helper call for identifying a passed file descriptor. Returns 1 if
+  the file descriptor is an Internet socket, of the specified family
+  (either AF_INET or AF_INET6) and the specified type (SOCK_DGRAM,
+  SOCK_STREAM, ...), 0 otherwise. If version is 0 a protocol version
+  check is not done. If type is 0 a socket type check will not be
+  done. If port is 0 a socket port check will not be done. The
+  listening flag is used the same way as in sd_is_socket(). Returns a
+  negative errno style error code on failure.
+
+  See sd_is_socket_inet(3) for more information.
+*/
+int sd_is_socket_inet(int fd, int family, int type, int listening, uint16_t port) _sd_hidden_;
+
+/*
+  Helper call for identifying a passed file descriptor. Returns 1 if
+  the file descriptor is an AF_UNIX socket of the specified type
+  (SOCK_DGRAM, SOCK_STREAM, ...) and path, 0 otherwise. If type is 0
+  a socket type check will not be done. If path is NULL a socket path
+  check will not be done. For normal AF_UNIX sockets set length to
+  0. For abstract namespace sockets set length to the length of the
+  socket name (including the initial 0 byte), and pass the full
+  socket path in path (including the initial 0 byte). The listening
+  flag is used the same way as in sd_is_socket(). Returns a negative
+  errno style error code on failure.
+
+  See sd_is_socket_unix(3) for more information.
+*/
+int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t length) _sd_hidden_;
+
+/*
+  Informs systemd about changed daemon state. This takes a number of
+  newline seperated environment-style variable assignments in a
+  string. The following variables are known:
+
+     READY=1      Tells systemd that daemon startup is finished (only
+                  relevant for services of Type=notify). The passed
+                  argument is a boolean "1" or "0". Since there is
+                  little value in signalling non-readiness the only
+                  value daemons should send is "READY=1".
+
+     STATUS=...   Passes a single-line status string back to systemd
+                  that describes the daemon state. This is free-from
+                  and can be used for various purposes: general state
+                  feedback, fsck-like programs could pass completion
+                  percentages and failing programs could pass a human
+                  readable error message. Example: "STATUS=Completed
+                  66% of file system check..."
+
+     ERRNO=...    If a daemon fails, the errno-style error code,
+                  formatted as string. Example: "ERRNO=2" for ENOENT.
+
+     BUSERROR=... If a daemon fails, the D-Bus error-style error
+                  code. Example: "BUSERROR=org.freedesktop.DBus.Error.TimedOut"
+
+     MAINPID=...  The main pid of a daemon, in case systemd did not
+                  fork off the process itself. Example: "MAINPID=4711"
+
+  Daemons can choose to send additional variables. However, it is
+  recommened to prefix variable names not listed above with X_.
+
+  Returns a negative errno-style error code on failure. Returns > 0
+  if systemd could be notified, 0 if it couldn't possibly because
+  systemd is not running.
+
+  Example: When a daemon finished starting up, it could issue this
+  call to notify systemd about it:
+
+     sd_notify(0, "READY=1");
+
+  See sd_notifyf() for more complete examples.
+
+  See sd_notify(3) for more information.
+*/
+int sd_notify(int unset_environment, const char *state) _sd_hidden_;
+
+/*
+  Similar to sd_notify() but takes a format string.
+
+  Example 1: A daemon could send the following after initialization:
+
+     sd_notifyf(0, "READY=1\n"
+                   "STATUS=Processing requests...\n"
+                   "MAINPID=%lu",
+                   (unsigned long) getpid());
+
+  Example 2: A daemon could send the following shortly before
+  exiting, on failure:
+
+     sd_notifyf(0, "STATUS=Failed to start up: %s\n"
+                   "ERRNO=%i",
+                   strerror(errno),
+                   errno);
+
+  See sd_notifyf(3) for more information.
+*/
+int sd_notifyf(int unset_environment, const char *format, ...) _sd_printf_attr_(2,3) _sd_hidden_;
+
+/*
+  Returns > 0 if the system was booted with systemd. Returns < 0 on
+  error. Returns 0 if the system was not booted with systemd. Note
+  that all of the functions above handle non-systemd boots just
+  fine. You should NOT protect them with a call to this function. Also
+  note that this function checks whether the system, not the user
+  session is controlled by systemd. However the functions above work
+  for both session and system services.
+
+  See sd_booted(3) for more information.
+*/
+int sd_booted(void) _sd_hidden_;
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
diff --git a/avahi-daemon/simple-protocol.c b/avahi-daemon/simple-protocol.c
index 33e5db3..ffe079f 100644
--- a/avahi-daemon/simple-protocol.c
+++ b/avahi-daemon/simple-protocol.c
@@ -2,17 +2,17 @@
 
 /***
   This file is part of avahi.
- 
+
   avahi is free software; you can redistribute it and/or modify it
   under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.
- 
+
   avahi is distributed in the hope that it will be useful, but WITHOUT
   ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
   or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
   Public License for more details.
- 
+
   You should have received a copy of the GNU Lesser General Public
   License along with avahi; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
@@ -44,6 +44,7 @@
 
 #include "simple-protocol.h"
 #include "main.h"
+#include "sd-daemon.h"
 
 #ifdef ENABLE_CHROOT
 #include "chroot.h"
@@ -75,7 +76,7 @@ struct Client {
     Server *server;
 
     ClientState state;
-    
+
     int fd;
     AvahiWatch *watch;
 
@@ -87,7 +88,7 @@ struct Client {
     AvahiSDNSServerBrowser *dns_server_browser;
 
     AvahiProtocol afquery;
-    
+
     AVAHI_LLIST_FIELDS(Client, clients);
 };
 
@@ -98,7 +99,7 @@ struct Server {
     AVAHI_LLIST_HEAD(Client, clients);
 
     unsigned n_clients;
-    int bind_successful;
+    int remove_socket;
 };
 
 static Server *server = NULL;
@@ -122,7 +123,7 @@ static void client_free(Client *c) {
 
     c->server->poll_api->watch_free(c->watch);
     close(c->fd);
-    
+
     AVAHI_LLIST_REMOVE(Client, clients, c->server->clients, c);
     avahi_free(c);
 }
@@ -151,7 +152,7 @@ static void client_new(Server *s, int fd) {
 
 static void client_output(Client *c, const uint8_t*data, size_t size) {
     size_t k, m;
-    
+
     assert(c);
     assert(data);
 
@@ -170,7 +171,7 @@ static void client_output(Client *c, const uint8_t*data, size_t size) {
 static void client_output_printf(Client *c, const char *format, ...) {
     char *t;
     va_list ap;
-    
+
     va_start(ap, format);
     t = avahi_strdup_vprintf(format, ap);
     va_end(ap);
@@ -186,11 +187,11 @@ static void host_name_resolver_callback(
     AvahiResolverEvent event,
     const char *hostname,
     const AvahiAddress *a,
-    AVAHI_GCC_UNUSED AvahiLookupResultFlags flags, 
+    AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
     void* userdata) {
 
     Client *c = userdata;
-    
+
     assert(c);
 
     if (event == AVAHI_RESOLVER_FAILURE)
@@ -213,9 +214,9 @@ static void address_resolver_callback(
     const char *hostname,
     AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
     void* userdata) {
-    
+
     Client *c = userdata;
-    
+
     assert(c);
 
     if (event == AVAHI_RESOLVER_FAILURE)
@@ -236,10 +237,10 @@ static void dns_server_browser_callback(
     uint16_t port,
     AVAHI_GCC_UNUSED AvahiLookupResultFlags flags,
     void* userdata) {
-    
+
     Client *c = userdata;
     char t[AVAHI_ADDRESS_STR_MAX];
-    
+
     assert(c);
 
     if (!a)
@@ -257,7 +258,7 @@ static void dns_server_browser_callback(
 
         case AVAHI_BROWSER_NEW:
         case AVAHI_BROWSER_REMOVE:
-    
+
             avahi_address_snprint(t, sizeof(t), a);
             client_output_printf(c, "%c %i %u %s %u\n", event == AVAHI_BROWSER_NEW ? '>' : '<',  interface, protocol, t, port);
             break;
@@ -314,7 +315,7 @@ static void handle_line(Client *c, const char *s) {
         avahi_log_debug(__FILE__": Got %s request for '%s'.", cmd, arg);
     } else if (strcmp(cmd, "RESOLVE-ADDRESS") == 0 && n_args == 2) {
         AvahiAddress addr;
-        
+
         if (!(avahi_address_parse(arg, AVAHI_PROTO_UNSPEC, &addr))) {
             client_output_printf(c, "%+i Failed to parse address \"%s\".\n", AVAHI_ERR_INVALID_ADDRESS, arg);
             c->state = CLIENT_DEAD;
@@ -376,7 +377,7 @@ static void handle_input(Client *c) {
 
         k = e - (char*) c->inbuf;
         *e = 0;
-        
+
         handle_line(c, c->inbuf);
         c->inbuf_length -= k + 1;
         memmove(c->inbuf, e+1, c->inbuf_length);
@@ -390,7 +391,7 @@ static void client_work(AvahiWatch *watch, AVAHI_GCC_UNUSED int fd, AvahiWatchEv
 
     if ((events & AVAHI_WATCH_IN) && c->inbuf_length < sizeof(c->inbuf)) {
         ssize_t r;
-        
+
         if ((r = read(c->fd, c->inbuf + c->inbuf_length, sizeof(c->inbuf) - c->inbuf_length)) <= 0) {
             if (r < 0)
                 avahi_log_warn("read(): %s", strerror(errno));
@@ -415,7 +416,7 @@ static void client_work(AvahiWatch *watch, AVAHI_GCC_UNUSED int fd, AvahiWatchEv
 
         assert((size_t) r <= c->outbuf_length);
         c->outbuf_length -= r;
-        
+
         if (c->outbuf_length)
             memmove(c->outbuf, c->outbuf + r, c->outbuf_length - r);
 
@@ -426,7 +427,7 @@ static void client_work(AvahiWatch *watch, AVAHI_GCC_UNUSED int fd, AvahiWatchEv
     }
 
     c->server->poll_api->watch_update(
-        watch, 
+        watch,
         (c->outbuf_length > 0 ? AVAHI_WATCH_OUT : 0) |
         (c->inbuf_length < sizeof(c->inbuf) ? AVAHI_WATCH_IN : 0));
 }
@@ -445,59 +446,83 @@ static void server_work(AVAHI_GCC_UNUSED AvahiWatch *watch, int fd, AvahiWatchEv
             client_new(s, cfd);
     }
 }
-    
+
 int simple_protocol_setup(const AvahiPoll *poll_api) {
     struct sockaddr_un sa;
     mode_t u;
+    int n;
 
     assert(!server);
 
     server = avahi_new(Server, 1);
     server->poll_api = poll_api;
-    server->bind_successful = 0;
+    server->remove_socket = 0;
     server->fd = -1;
     server->n_clients = 0;
     AVAHI_LLIST_HEAD_INIT(Client, server->clients);
     server->watch = NULL;
-    
+
     u = umask(0000);
 
-    if ((server->fd = socket(PF_LOCAL, SOCK_STREAM, 0)) < 0) {
-        avahi_log_warn("socket(PF_LOCAL, SOCK_STREAM, 0): %s", strerror(errno));
+    if ((n = sd_listen_fds(1)) < 0) {
+        avahi_log_warn("Failed to acquire systemd file descriptors: %s", strerror(-n));
         goto fail;
     }
 
-    memset(&sa, 0, sizeof(sa));
-    sa.sun_family = AF_LOCAL;
-    strncpy(sa.sun_path, AVAHI_SOCKET, sizeof(sa.sun_path)-1);
-
-    /* We simply remove existing UNIX sockets under this name. The
-       Avahi daemon makes sure that it runs only once on a host,
-       therefore sockets that already exist are stale and may be
-       removed without any ill effects */
-
-    unlink(AVAHI_SOCKET);
-    
-    if (bind(server->fd, (struct sockaddr*) &sa, sizeof(sa)) < 0) {
-        avahi_log_warn("bind(): %s", strerror(errno));
+    if (n > 1) {
+        avahi_log_warn("Too many systemd file descriptors passed.");
         goto fail;
     }
 
-    server->bind_successful = 1;
-    
-    if (listen(server->fd, 2) < 0) {
-        avahi_log_warn("listen(): %s", strerror(errno));
-        goto fail;
+    if (n == 1) {
+        int r;
+
+        if ((r = sd_is_socket(AF_LOCAL, SOCK_STREAM, 1, 0)) < 0) {
+            avahi_log_warn("Passed systemd file descriptor is of wrong type: %s", strerror(-r));
+            goto fail;
+        }
+
+        server->fd = SD_LISTEN_FDS_START;
+
+    } else {
+
+        if ((server->fd = socket(AF_LOCAL, SOCK_STREAM, 0)) < 0) {
+            avahi_log_warn("socket(AF_LOCAL, SOCK_STREAM, 0): %s", strerror(errno));
+            goto fail;
+        }
+
+        memset(&sa, 0, sizeof(sa));
+        sa.sun_family = AF_LOCAL;
+        strncpy(sa.sun_path, AVAHI_SOCKET, sizeof(sa.sun_path)-1);
+
+        /* We simply remove existing UNIX sockets under this name. The
+           Avahi daemon makes sure that it runs only once on a host,
+           therefore sockets that already exist are stale and may be
+           removed without any ill effects */
+
+        unlink(AVAHI_SOCKET);
+
+        if (bind(server->fd, (struct sockaddr*) &sa, sizeof(sa)) < 0) {
+            avahi_log_warn("bind(): %s", strerror(errno));
+            goto fail;
+        }
+
+        server->remove_socket = 1;
+
+        if (listen(server->fd, SOMAXCONN) < 0) {
+            avahi_log_warn("listen(): %s", strerror(errno));
+            goto fail;
+        }
     }
 
     umask(u);
 
     server->watch = poll_api->watch_new(poll_api, server->fd, AVAHI_WATCH_IN, server_work, server);
-    
+
     return 0;
 
 fail:
-    
+
     umask(u);
     simple_protocol_shutdown();
 
@@ -508,7 +533,7 @@ void simple_protocol_shutdown(void) {
 
     if (server) {
 
-        if (server->bind_successful)
+        if (server->remove_socket)
 #ifdef ENABLE_CHROOT
             avahi_chroot_helper_unlink(AVAHI_SOCKET);
 #else
@@ -520,12 +545,12 @@ void simple_protocol_shutdown(void) {
 
         if (server->watch)
             server->poll_api->watch_free(server->watch);
-        
+
         if (server->fd >= 0)
             close(server->fd);
 
         avahi_free(server);
-        
+
         server = NULL;
     }
 }
@@ -534,7 +559,7 @@ void simple_protocol_restart_queries(void) {
     Client *c;
 
     /* Restart queries in case of local domain name changes */
-    
+
     assert(server);
 
     for (c = server->clients; c; c = c->clients_next)
@@ -543,5 +568,3 @@ void simple_protocol_restart_queries(void) {
             c->dns_server_browser = avahi_s_dns_server_browser_new(avahi_server, AVAHI_IF_UNSPEC, AVAHI_PROTO_UNSPEC, NULL, AVAHI_DNS_SERVER_RESOLVE, c->afquery, AVAHI_LOOKUP_USE_MULTICAST, dns_server_browser_callback, c);
         }
 }
-
-