implement trivial socket activated logger daemon

.gitignore

@@ -2,3 +2,4 @@ systemd
 *.o
 test-engine
 test-job-type
+systemd-logger

Makefile

@@ -25,11 +25,14 @@ COMMON= \
 	load-dropin.o \
 	execute.o
 
-all: systemd test-engine test-job-type
+all: systemd test-engine test-job-type systemd-logger
 
 systemd: main.o $(COMMON)
 	$(CC) $(CFLAGS) -o $@ $^  $(LIBS)
 
+systemd-logger: logger.o $(COMMON)
+	$(CC) $(CFLAGS) -o $@ $^  $(LIBS)
+
 test-engine: test-engine.o $(COMMON)
 	$(CC) $(CFLAGS) -o $@ $^  $(LIBS)
 

logger.c

@@ -0,0 +1,496 @@
+/*-*- Mode: C; c-basic-offset: 8 -*-*/
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <assert.h>
+#include <time.h>
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <sys/poll.h>
+#include <sys/epoll.h>
+#include <sys/un.h>
+
+#include "util.h"
+#include "log.h"
+#include "list.h"
+
+#define STREAM_BUFFER 2048
+#define STREAMS_MAX 256
+#define SERVER_FD_START 3
+#define SERVER_FD_MAX 16
+#define TIMEOUT ((int) (10*MSEC_PER_SEC))
+
+typedef struct Stream Stream;
+
+typedef struct Server {
+        int log_fd;
+        int epoll_fd;
+
+        unsigned n_server_fd;
+
+        LIST_HEAD(Stream, streams);
+        unsigned n_streams;
+} Server;
+
+typedef enum StreamState {
+        STREAM_PRIORITY,
+        STREAM_PROCESS,
+        STREAM_RUNNING
+} StreamState;
+
+struct Stream {
+        Server *server;
+
+        StreamState state;
+
+        int fd;
+        int priority;
+        char *process;
+
+        char buffer[STREAM_BUFFER];
+        size_t length;
+
+        pid_t pid;
+
+        LIST_FIELDS(Stream, stream);
+};
+
+#define IOVEC_SET_STRING(iovec, s)              \
+        do {                                    \
+                (iovec).iov_base = s;           \
+                (iovec).iov_len = strlen(s);    \
+        } while(false);
+
+static int stream_log(Stream *s, char *p, usec_t timestamp) {
+
+        char header_priority[16], header_time[64], header_pid[16];
+        time_t t;
+        struct tm *tm;
+        struct msghdr msghdr;
+        struct iovec iovec[5];
+
+        assert(s);
+        assert(p);
+
+        if (*p == 0)
+                return 0;
+
+        /*
+         * The format glibc uses is:
+         *
+         * <priority>time process[pid]: msg
+         */
+
+        snprintf(header_priority, sizeof(header_priority), "<%i>", s->priority);
+        char_array_0(header_priority);
+
+        t = (time_t) (timestamp / USEC_PER_SEC);
+        if (!(tm = localtime(&t)))
+                return -EINVAL;
+
+        if (strftime(header_time, sizeof(header_time), "%h %e %T ", tm) <= 0)
+                return -EINVAL;
+
+        snprintf(header_pid, sizeof(header_pid), "[%llu]: ", (unsigned long long) s->pid);
+        char_array_0(header_pid);
+
+        zero(iovec);
+        IOVEC_SET_STRING(iovec[0], header_priority);
+        IOVEC_SET_STRING(iovec[1], header_time);
+        IOVEC_SET_STRING(iovec[2], s->process);
+        IOVEC_SET_STRING(iovec[3], header_pid);
+        IOVEC_SET_STRING(iovec[4], p);
+
+        zero(msghdr);
+        msghdr.msg_iov = iovec;
+        msghdr.msg_iovlen = ELEMENTSOF(iovec);
+
+        if (sendmsg(s->server->log_fd, &msghdr, MSG_NOSIGNAL) < 0)
+                return -errno;
+
+        return 0;
+}
+
+static int stream_line(Stream *s, char *p, usec_t timestamp) {
+        int r;
+
+        assert(s);
+        assert(p);
+
+        p = strstrip(p);
+
+        switch (s->state) {
+
+        case STREAM_PRIORITY:
+                if ((r = safe_atoi(p, &s->priority)) < 0)
+                        return r;
+
+                if (s->priority < 0)
+                        return -ERANGE;
+
+                s->state = STREAM_PROCESS;
+                return 0;
+
+        case STREAM_PROCESS:
+                if (!(s->process = strdup(p)))
+                        return -ENOMEM;
+
+                s->state = STREAM_RUNNING;
+                return 0;
+
+        case STREAM_RUNNING:
+                return stream_log(s, p, timestamp);
+        }
+
+        assert_not_reached("Unknown stream state");
+}
+
+static int stream_scan(Stream *s, usec_t timestamp) {
+        char *p;
+        size_t remaining;
+        int r = 0;
+
+        assert(s);
+
+        p = s->buffer;
+        remaining = s->length;
+        for (;;) {
+                char *newline;
+
+                if (!(newline = memchr(p, '\n', remaining)))
+                        break;
+
+                *newline = 0;
+
+                if ((r = stream_line(s, p, timestamp)) >= 0) {
+                        remaining -= newline-p+1;
+                        p = newline+1;
+                }
+        }
+
+        if (p > s->buffer) {
+                memmove(s->buffer, p, remaining);
+                s->length = remaining;
+        }
+
+        return r;
+}
+
+static int stream_process(Stream *s, usec_t timestamp) {
+        ssize_t l;
+        int r;
+        assert(s);
+
+        if ((l = read(s->fd, s->buffer+s->length, STREAM_BUFFER-s->length)) < 0) {
+
+                if (errno == EAGAIN)
+                        return 0;
+
+                log_warning("Failed to read from stream: %s", strerror(errno));
+                return -1;
+        }
+
+
+        if (l == 0)
+                return 0;
+
+        s->length += l;
+        r = stream_scan(s, timestamp);
+
+        if (r < 0)
+                return r;
+
+        return 1;
+}
+
+static void stream_free(Stream *s) {
+        assert(s);
+
+        if (s->server) {
+                assert(s->server->n_streams > 0);
+                s->server->n_streams--;
+                LIST_REMOVE(Stream, stream, s->server->streams, s);
+
+        }
+
+        if (s->fd >= 0) {
+                if (s->server)
+                        epoll_ctl(s->server->epoll_fd, EPOLL_CTL_DEL, s->fd, NULL);
+
+                assert_se(close_nointr(s->fd) == 0);
+        }
+
+        free(s->process);
+        free(s);
+}
+
+static int stream_new(Server *s, int server_fd) {
+        Stream *stream;
+        int fd;
+        struct ucred ucred;
+        socklen_t len = sizeof(ucred);
+        struct epoll_event ev;
+        int r;
+
+        assert(s);
+
+        if ((fd = accept4(server_fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC)) < 0)
+                return -errno;
+
+        if (s->n_streams >= STREAMS_MAX) {
+                log_warning("Too many connections, refusing connection.");
+                assert_se(close_nointr(fd) == 0);
+                return 0;
+        }
+
+        if (!(stream = new0(Stream, 1))) {
+                assert_se(close_nointr(fd) == 0);
+                return -ENOMEM;
+        }
+
+        stream->fd = fd;
+
+        if (getsockopt(stream->fd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        if (shutdown(fd, SHUT_WR) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        zero(ev);
+        ev.data.ptr = stream;
+        ev.events = POLLIN;
+        if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
+                r = -errno;
+                goto fail;
+        }
+
+        stream->pid = ucred.pid;
+
+        stream->server = s;
+        LIST_PREPEND(Stream, stream, s->streams, stream);
+        s->n_streams ++;
+
+        return 0;
+
+fail:
+        stream_free(stream);
+        return r;
+}
+
+static int verify_environment(unsigned *n_sockets) {
+        unsigned long long pid;
+        const char *e;
+        int r;
+        unsigned ns;
+
+        assert_se(n_sockets);
+
+        if (!(e = getenv("LISTEN_PID"))) {
+                log_error("Missing $LISTEN_PID environment variable.");
+                return -ENOENT;
+        }
+
+        if ((r = safe_atollu(e, &pid)) < 0) {
+                log_error("Failed to parse $LISTEN_PID: %s", strerror(-r));
+                return r;
+        }
+
+        if (pid != (unsigned long long) getpid()) {
+                log_error("Socket nor for me.");
+                return -ENOENT;
+        }
+
+        if (!(e = getenv("LISTEN_FDS"))) {
+                log_error("Missing $LISTEN_FDS environment variable.");
+                return -ENOENT;
+        }
+
+        if ((r = safe_atou(e, &ns)) < 0) {
+                log_error("Failed to parse $LISTEN_FDS: %s", strerror(-r));
+                return -E2BIG;
+        }
+
+        if (ns <= 0 || ns > SERVER_FD_MAX) {
+                log_error("Wrong number of file descriptors passed: %s", e);
+                return -E2BIG;
+        }
+
+        *n_sockets = ns;
+
+        return 0;
+}
+
+static void server_done(Server *s) {
+        unsigned i;
+        assert(s);
+
+        while (s->streams)
+                stream_free(s->streams);
+
+        for (i = 0; i < s->n_server_fd; i++)
+                assert_se(close_nointr(SERVER_FD_START+i) == 0);
+
+        if (s->log_fd >= 0)
+                assert_se(close_nointr(s->log_fd) == 0);
+
+        if (s->epoll_fd >= 0)
+                assert_se(close_nointr(s->epoll_fd) == 0);
+}
+
+static int server_init(Server *s, unsigned n_sockets) {
+        int r;
+        unsigned i;
+        union {
+                struct sockaddr sa;
+                struct sockaddr_un un;
+        } sa;
+
+        assert(s);
+        assert(n_sockets > 0);
+
+        zero(*s);
+
+        s->n_server_fd = n_sockets;
+        s->log_fd = -1;
+
+        if ((s->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0) {
+                r = -errno;
+                log_error("Failed to create epoll object: %s", strerror(errno));
+                goto fail;
+        }
+
+        for (i = 0; i < n_sockets; i++) {
+                struct epoll_event ev;
+
+                zero(ev);
+                ev.events = POLLIN;
+                ev.data.ptr = UINT_TO_PTR(SERVER_FD_START+i);
+                if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, SERVER_FD_START+i, &ev) < 0) {
+                        r = -errno;
+                        log_error("Failed to add server fd to epoll object: %s", strerror(errno));
+                        goto fail;
+                }
+        }
+
+        if ((s->log_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0)) < 0) {
+                r = -errno;
+                log_error("Failed to create log fd: %s", strerror(errno));
+                goto fail;
+        }
+
+        zero(sa);
+        sa.un.sun_family = AF_UNIX;
+        strncpy(sa.un.sun_path, "/dev/log", sizeof(sa.un.sun_path));
+
+        if (connect(s->log_fd, &sa.sa, sizeof(sa)) < 0) {
+                r = -errno;
+                log_error("Failed to connect log socket to /dev/log: %s", strerror(errno));
+                goto fail;
+        }
+
+        return 0;
+
+fail:
+        server_done(s);
+        return r;
+}
+
+static int process_event(Server *s, struct epoll_event *ev) {
+        int r;
+
+        assert(s);
+
+        /* Yes, this is a bit ugly, we assume that that valid pointers
+         * are > SERVER_FD_START+SERVER_FD_MAX. Which is certainly
+         * true on Linux (and probably most other OSes, too, since the
+         * first 4k usually are part of a seperate null pointer
+         * dereference page. */
+
+        if (PTR_TO_UINT(ev->data.ptr) >= SERVER_FD_START &&
+            PTR_TO_UINT(ev->data.ptr) < SERVER_FD_START+s->n_server_fd) {
+
+                if (ev->events != POLLIN) {
+                        log_info("Got invalid event from epoll. (1)");
+                        return -EIO;
+                }
+
+                if ((r = stream_new(s, PTR_TO_UINT(ev->data.ptr))) < 0) {
+                        log_info("Failed to accept new connection: %s", strerror(-r));
+                        return r;
+                }
+
+        } else {
+                usec_t timestamp;
+                Stream *stream = ev->data.ptr;
+
+                timestamp = now(CLOCK_REALTIME);
+
+                if (!(ev->events & POLLIN)) {
+                        log_info("Got invalid event from epoll. (3)");
+                        stream_free(stream);
+                        return 0;
+                }
+
+                if ((r = stream_process(stream, timestamp)) <= 0) {
+
+                        if (r < 0)
+                                log_info("Got error on stream: %s", strerror(-r));
+
+                        stream_free(stream);
+                        return 0;
+                }
+        }
+
+        return 0;
+}
+
+int main(int argc, char *argv[]) {
+        Server server;
+        int r = 3;
+        unsigned n;
+
+        log_info("systemd-logger running as pid %llu", (unsigned long long) getpid());
+
+        if (verify_environment(&n) < 0)
+                return 1;
+
+        if (server_init(&server, n) < 0)
+                return 2;
+
+
+        for (;;) {
+                struct epoll_event event;
+                int n;
+
+                if ((n = epoll_wait(server.epoll_fd,
+                                    &event, 1,
+                                    server.n_streams <= 0 ? TIMEOUT : -1)) < 0) {
+
+                        if (errno == EINTR)
+                                continue;
+
+                        log_error("epoll_wait() failed: %s", strerror(errno));
+                        goto fail;
+                }
+
+                if (n <= 0)
+                        break;
+
+                if ((r = process_event(&server, &event)) < 0)
+                        goto fail;
+        }
+        r = 0;
+
+fail:
+        server_done(&server);
+
+        log_info("systemd-logger stopped as pid %llu", (unsigned long long) getpid());
+
+        return r;
+}

test1/multiuser.target

@@ -1,3 +1,2 @@
 [Meta]
-Wants=syslog.socket
 Description=Multi-User Target

test1/multiuser.target.wants/systemd-logger.socket

@@ -0,0 +1 @@
+../systemd-logger.socket

test1/systemd-logger.service

@@ -0,0 +1,6 @@
+[Meta]
+Description=systemd Logging Daemon
+
+[Service]
+ExecStart=/home/lennart/projects/systemd/systemd-logger
+Type=simple

test1/systemd-logger.socket

@@ -0,0 +1,7 @@
+[Meta]
+Description=systemd Logging Socket
+
+[Socket]
+ExecStartPre=/bin/rm /tmp/systemd-logger
+ListenStream==/systemd/logger
+ListenStream=/tmp/systemd-logger