notify: add minimal readiness/status protocol for spawned daemons

1 files changed, 112 insertions, 1 deletions

diff --git a/src/sd-daemon.c b/src/sd-daemon.c
index 29bd204680..0dad73f94d 100644
--- a/src/sd-daemon.c
+++ b/src/sd-daemon.c
@@ -24,6 +24,10 @@
   SOFTWARE.
 ***/
 
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include <sys/types.h>
 #include <sys/stat.h>
 #include <sys/socket.h>
@@ -34,12 +38,14 @@
 #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) {
 
-#ifdef DISABLE_SYSTEMD
+#if defined(DISABLE_SYSTEMD) || !defined(__linux__)
         return 0;
 #else
         int r, fd;
@@ -317,3 +323,108 @@ int sd_is_socket_unix(int fd, int type, int listening, const char *path, size_t
 
         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"))) {
+                r = 0;
+                goto finish;
+        }
+
+        /* 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 = 0;
+
+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
+}