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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
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This file is part of systemd.
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Copyright 2010 Lennart Poettering
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systemd is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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systemd is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with systemd; If not, see <http://www.gnu.org/licenses/>.
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#include <sys/socket.h>
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#include <sys/types.h>
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#include <sys/epoll.h>
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#include "sd-daemon.h"
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#define STREAMS_MAX 4096
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#define SERVER_FD_MAX 16
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#define TIMEOUT_MSEC ((int) (DEFAULT_EXIT_USEC/USEC_PER_MSEC))
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typedef struct Stream Stream;
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typedef struct Server {
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bool syslog_is_stream;
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LIST_HEAD(Stream, streams);
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typedef enum StreamTarget {
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typedef enum StreamState {
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char buffer[LINE_MAX+1];
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LIST_FIELDS(Stream, stream);
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static int stream_log(Stream *s, char *p, usec_t ts) {
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char header_priority[16], header_time[64], header_pid[16];
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struct iovec iovec[5];
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priority = s->priority;
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parse_syslog_priority(&p, &priority);
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/* Patch in configured facility if necessary */
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if ((priority & LOG_FACMASK) == 0)
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priority = (s->priority & LOG_FACMASK) | priority;
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* The format glibc uses to talk to the syslog daemon is:
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* <priority>time process[pid]: msg
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* The format the kernel uses is:
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* We extend the latter to include the process name and pid.
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snprintf(header_priority, sizeof(header_priority), "<%i>", priority);
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char_array_0(header_priority);
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if (s->target == STREAM_SYSLOG) {
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t = (time_t) (ts / USEC_PER_SEC);
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if (!(tm = localtime(&t)))
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if (strftime(header_time, sizeof(header_time), "%h %e %T ", tm) <= 0)
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snprintf(header_pid, sizeof(header_pid), "[%lu]: ", (unsigned long) s->pid);
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char_array_0(header_pid);
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IOVEC_SET_STRING(iovec[0], header_priority);
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if (s->target == STREAM_SYSLOG) {
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struct msghdr msghdr;
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struct cmsghdr cmsghdr;
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uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
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control.cmsghdr.cmsg_level = SOL_SOCKET;
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control.cmsghdr.cmsg_type = SCM_CREDENTIALS;
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control.cmsghdr.cmsg_len = CMSG_LEN(sizeof(struct ucred));
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ucred = (struct ucred*) CMSG_DATA(&control.cmsghdr);
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IOVEC_SET_STRING(iovec[1], header_time);
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IOVEC_SET_STRING(iovec[2], s->process);
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IOVEC_SET_STRING(iovec[3], header_pid);
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IOVEC_SET_STRING(iovec[4], p);
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/* When using syslog via SOCK_STREAM separate the messages by NUL chars */
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if (s->server->syslog_is_stream)
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msghdr.msg_iov = iovec;
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msghdr.msg_iovlen = ELEMENTSOF(iovec);
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msghdr.msg_control = &control;
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msghdr.msg_controllen = control.cmsghdr.cmsg_len;
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if ((n = sendmsg(s->server->syslog_fd, &msghdr, MSG_NOSIGNAL)) < 0) {
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if (errno == ESRCH) {
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/* Hmm, maybe the process this
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* line originates from is
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* dead? Then let's patch in
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* our own pid and retry,
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* since we have nothing
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if (ucred->pid != our_pid) {
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ucred->pid = our_pid;
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if (!s->server->syslog_is_stream ||
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(size_t) n >= IOVEC_TOTAL_SIZE(iovec, ELEMENTSOF(iovec)))
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IOVEC_INCREMENT(iovec, ELEMENTSOF(iovec), n);
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} else if (s->target == STREAM_KMSG) {
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IOVEC_SET_STRING(iovec[1], s->process);
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IOVEC_SET_STRING(iovec[2], header_pid);
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IOVEC_SET_STRING(iovec[3], p);
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IOVEC_SET_STRING(iovec[4], (char*) "\n");
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if (writev(s->server->kmsg_fd, iovec, ELEMENTSOF(iovec)) < 0)
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assert_not_reached("Unknown log target");
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if (s->tee_console) {
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if ((console = open_terminal("/dev/console", O_WRONLY|O_NOCTTY|O_CLOEXEC)) >= 0) {
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IOVEC_SET_STRING(iovec[0], s->process);
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IOVEC_SET_STRING(iovec[1], header_pid);
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IOVEC_SET_STRING(iovec[2], p);
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IOVEC_SET_STRING(iovec[3], (char*) "\n");
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writev(console, iovec, 4);
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static int stream_line(Stream *s, char *p, usec_t ts) {
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if (streq(p, "syslog") || streq(p, "syslog+console"))
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s->target = STREAM_SYSLOG;
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else if (streq(p, "kmsg") || streq(p, "kmsg+console")) {
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if (s->server->kmsg_fd >= 0 && s->uid == 0)
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s->target = STREAM_KMSG;
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log_warning("/dev/kmsg logging not available.");
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log_warning("Failed to parse log target line.");
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if (endswith(p, "+console"))
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s->tee_console = true;
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s->state = STREAM_PRIORITY;
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case STREAM_PRIORITY:
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if ((r = safe_atoi(p, &s->priority)) < 0) {
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log_warning("Failed to parse log priority line: %m");
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if (s->priority < 0) {
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log_warning("Log priority negative: %m");
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s->state = STREAM_PROCESS;
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if (!(s->process = strdup(p)))
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s->state = STREAM_PREFIX;
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if ((r = parse_boolean(p)) < 0)
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s->state = STREAM_RUNNING;
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return stream_log(s, p, ts);
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assert_not_reached("Unknown stream state");
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static int stream_scan(Stream *s, usec_t ts) {
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remaining = s->length;
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end = memchr(p, '\n', remaining);
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if (remaining >= LINE_MAX) {
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r = stream_line(s, p, ts);
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memmove(s->buffer, p, remaining);
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s->length = remaining;
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static int stream_process(Stream *s, usec_t ts) {
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l = read(s->fd, s->buffer+s->length, LINE_MAX-s->length);
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log_warning("Failed to read from stream: %m");
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r = stream_scan(s, ts);
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static void stream_free(Stream *s) {
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assert(s->server->n_streams > 0);
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s->server->n_streams--;
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LIST_REMOVE(Stream, stream, s->server->streams, s);
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epoll_ctl(s->server->epoll_fd, EPOLL_CTL_DEL, s->fd, NULL);
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close_nointr_nofail(s->fd);
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static int stream_new(Server *s, int server_fd) {
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socklen_t len = sizeof(ucred);
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struct epoll_event ev;
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if ((fd = accept4(server_fd, NULL, NULL, SOCK_NONBLOCK|SOCK_CLOEXEC)) < 0)
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if (s->n_streams >= STREAMS_MAX) {
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log_warning("Too many connections, refusing connection.");
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close_nointr_nofail(fd);
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if (!socket_tcpwrap(fd, "systemd-stdout-syslog-bridge")) {
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close_nointr_nofail(fd);
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if (!(stream = new0(Stream, 1))) {
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close_nointr_nofail(fd);
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if (getsockopt(stream->fd, SOL_SOCKET, SO_PEERCRED, &ucred, &len) < 0) {
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if (shutdown(fd, SHUT_WR) < 0) {
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ev.data.ptr = stream;
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if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
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stream->pid = ucred.pid;
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stream->uid = ucred.uid;
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stream->gid = ucred.gid;
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LIST_PREPEND(Stream, stream, s->streams, stream);
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static void server_done(Server *s) {
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stream_free(s->streams);
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for (i = 0; i < s->n_server_fd; i++)
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close_nointr_nofail(SD_LISTEN_FDS_START+i);
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if (s->syslog_fd >= 0)
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close_nointr_nofail(s->syslog_fd);
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if (s->epoll_fd >= 0)
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close_nointr_nofail(s->epoll_fd);
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close_nointr_nofail(s->kmsg_fd);
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static int server_init(Server *s, unsigned n_sockets) {
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struct sockaddr_un un;
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assert(n_sockets > 0);
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s->n_server_fd = n_sockets;
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if ((s->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0) {
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log_error("Failed to create epoll object: %m");
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for (i = 0; i < n_sockets; i++) {
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struct epoll_event ev;
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fd = SD_LISTEN_FDS_START+i;
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if ((r = sd_is_socket(fd, AF_UNSPEC, SOCK_STREAM, 1)) < 0) {
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log_error("Failed to determine file descriptor type: %s", strerror(-r));
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log_error("Wrong file descriptor type.");
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/* We use ev.data.ptr instead of ev.data.fd here,
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* since on 64bit archs fd is 32bit while a pointer is
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* 64bit. To make sure we can easily distinguish fd
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* values and pointer values we want to make sure to
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* write the full field unconditionally. */
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ev.data.ptr = INT_TO_PTR(fd);
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if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
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log_error("Failed to add server fd to epoll object: %m");
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sa.un.sun_family = AF_UNIX;
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strncpy(sa.un.sun_path, "/dev/log", sizeof(sa.un.sun_path));
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if ((s->syslog_fd = socket(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0)) < 0) {
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log_error("Failed to create log fd: %m");
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if (connect(s->syslog_fd, &sa.sa, sizeof(sa)) < 0) {
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close_nointr_nofail(s->syslog_fd);
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if ((s->syslog_fd = socket(AF_UNIX, SOCK_STREAM|SOCK_CLOEXEC, 0)) < 0) {
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log_error("Failed to create log fd: %m");
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if (connect(s->syslog_fd, &sa.sa, sizeof(sa)) < 0) {
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log_error("Failed to connect log socket to /dev/log: %m");
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s->syslog_is_stream = true;
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s->syslog_is_stream = false;
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/* /dev/kmsg logging is strictly optional */
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if ((s->kmsg_fd = open("/dev/kmsg", O_WRONLY|O_NOCTTY|O_CLOEXEC)) < 0)
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log_warning("Failed to open /dev/kmsg for logging, disabling kernel log buffer support: %m");
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static int process_event(Server *s, struct epoll_event *ev) {
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/* Yes, this is a bit ugly, we assume that that valid pointers
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* are > SD_LISTEN_FDS_START+SERVER_FD_MAX. Which is certainly
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* true on Linux (and probably most other OSes, too, since the
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* first 4k usually are part of a separate null pointer
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* dereference page. */
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if (PTR_TO_INT(ev->data.ptr) >= SD_LISTEN_FDS_START &&
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PTR_TO_INT(ev->data.ptr) < SD_LISTEN_FDS_START+(int)s->n_server_fd) {
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if (ev->events != EPOLLIN) {
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log_info("Got invalid event from epoll. (1)");
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if ((r = stream_new(s, PTR_TO_INT(ev->data.ptr))) < 0) {
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log_info("Failed to accept new connection: %s", strerror(-r));
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Stream *stream = ev->data.ptr;
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ts = now(CLOCK_REALTIME);
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if (!(ev->events & EPOLLIN)) {
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log_info("Got invalid event from epoll. (2)");
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if ((r = stream_process(stream, ts)) <= 0) {
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log_info("Got error on stream: %s", strerror(-r));
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int main(int argc, char *argv[]) {
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int r = EXIT_FAILURE, n;
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if (getppid() != 1) {
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log_error("This program should be invoked by init only.");
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log_error("This program does not take arguments.");
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log_set_target(LOG_TARGET_SYSLOG_OR_KMSG);
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log_parse_environment();
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if ((n = sd_listen_fds(true)) < 0) {
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log_error("Failed to read listening file descriptors from environment: %s", strerror(-r));
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if (n <= 0 || n > SERVER_FD_MAX) {
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log_error("No or too many file descriptors passed.");
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if (server_init(&server, (unsigned) n) < 0)
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log_debug("systemd-stdout-syslog-bridge running as pid %lu", (unsigned long) getpid());
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"STATUS=Processing requests...");
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struct epoll_event event;
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if ((k = epoll_wait(server.epoll_fd,
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server.n_streams <= 0 ? TIMEOUT_MSEC : -1)) < 0) {
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log_error("epoll_wait() failed: %m");
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if (process_event(&server, &event) < 0)
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log_debug("systemd-stdout-syslog-bridge stopped as pid %lu", (unsigned long) getpid());
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"STATUS=Shutting down...");
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server_done(&server);
added
removed
src/stdout-syslog-bridge.c
