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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 <sys/signalfd.h>
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#include "sd-daemon.h"
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#define SERVER_FD_MAX 16
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typedef struct Stream Stream;
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typedef struct Server {
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static void server_done(Server *s) {
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close_nointr_nofail(s->epoll_fd);
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close_nointr_nofail(s->kmsg_fd);
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if (s->signal_fd >= 0)
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close_nointr_nofail(s->signal_fd);
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fdset_free(s->syslog_fds);
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static int server_init(Server *s, unsigned n_sockets) {
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struct epoll_event ev;
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assert(n_sockets > 0);
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s->kmsg_fd = s->signal_fd = -1;
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if ((s->epoll_fd = epoll_create1(EPOLL_CLOEXEC)) < 0) {
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log_error("Failed to create epoll object: %s", strerror(errno));
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if (!(s->syslog_fds = fdset_new())) {
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log_error("Failed to allocate file descriptor set: %s", strerror(errno));
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for (i = 0; i < n_sockets; i++) {
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fd = SD_LISTEN_FDS_START+i;
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if ((r = sd_is_socket(fd, AF_UNSPEC, SOCK_DGRAM, -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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if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)) < 0)
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log_error("SO_PASSCRED failed: %m");
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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: %s", strerror(errno));
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if ((r = fdset_put(s->syslog_fds, fd)) < 0) {
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log_error("Failed to store file descriptor in set: %s", strerror(-r));
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if ((s->kmsg_fd = open("/dev/kmsg", O_WRONLY|O_NOCTTY|O_CLOEXEC)) < 0) {
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log_error("Failed to open /dev/kmsg for logging: %m");
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assert_se(sigemptyset(&mask) == 0);
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sigset_add_many(&mask, SIGINT, SIGTERM, -1);
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assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
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if ((s->signal_fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
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log_error("signalfd(): %m");
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ev.data.fd = s->signal_fd;
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if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, s->signal_fd, &ev) < 0) {
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log_error("epoll_ctl(): %m");
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static void skip_date(const char **buf) {
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LETTER, LETTER, LETTER,
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SPACE_OR_NUMBER, NUMBER,
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SPACE_OR_NUMBER, NUMBER,
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SPACE_OR_NUMBER, NUMBER,
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SPACE_OR_NUMBER, NUMBER,
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for (i = 0; i < ELEMENTSOF(sequence); i++, p++) {
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switch (sequence[i]) {
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case SPACE_OR_NUMBER:
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if (*p < '0' || *p > '9')
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if (!(*p >= 'A' && *p <= 'Z') &&
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!(*p >= 'a' && *p <= 'z'))
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static int read_process(const char **buf, struct iovec *iovec) {
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p += strspn(p, WHITESPACE);
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l = strcspn(p, WHITESPACE);
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iovec->iov_base = (char*) p;
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static void skip_pid(const char **buf) {
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p += strspn(p, "0123456789");
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static int write_message(Server *s, const char *buf, struct ucred *ucred) {
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char priority[6], pid[16];
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struct iovec iovec[5];
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char *process = NULL;
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int prio = LOG_USER | LOG_INFO;
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parse_syslog_priority((char**) &buf, &prio);
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if ((prio & LOG_FACMASK) == 0)
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prio = LOG_USER | LOG_PRI(prio);
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/* First, set priority field */
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snprintf(priority, sizeof(priority), "<%i>", prio);
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char_array_0(priority);
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IOVEC_SET_STRING(iovec[i++], priority);
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/* Second, skip date */
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/* Then, add process if set */
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if (read_process(&buf, &iovec[i]) > 0)
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get_process_name(ucred->pid, &process) >= 0)
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IOVEC_SET_STRING(iovec[i++], process);
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/* Skip the stored PID if we have a better one */
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snprintf(pid, sizeof(pid), "[%lu]: ", (unsigned long) ucred->pid);
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IOVEC_SET_STRING(iovec[i++], pid);
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buf += strspn(buf, WHITESPACE);
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/* Is the remaining message empty? */
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/* And the rest is the message */
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IOVEC_SET_STRING(iovec[i++], buf);
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IOVEC_SET_STRING(iovec[i++], "\n");
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if ((k = writev(s->kmsg_fd, iovec, i)) <= 0) {
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log_error("Failed to write log message to kmsg: %s", k < 0 ? strerror(errno) : "short write");
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r = k < 0 ? -errno : -EIO;
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static int process_event(Server *s, struct epoll_event *ev) {
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if (ev->events != EPOLLIN) {
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log_info("Got invalid event from epoll.");
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if (ev->data.fd == s->signal_fd) {
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struct signalfd_siginfo sfsi;
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if ((n = read(s->signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {
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if (errno == EINTR || errno == EAGAIN)
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log_debug("Received SIG%s", signal_to_string(sfsi.ssi_signo));
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char buf[LINE_MAX+1];
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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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iovec.iov_base = buf;
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iovec.iov_len = sizeof(buf)-1;
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msghdr.msg_iov = &iovec;
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msghdr.msg_iovlen = 1;
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msghdr.msg_control = &control;
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msghdr.msg_controllen = sizeof(control);
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if ((n = recvmsg(ev->data.fd, &msghdr, MSG_DONTWAIT)) < 0) {
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if (errno == EINTR || errno == EAGAIN)
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log_error("recvmsg() failed: %m");
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if (msghdr.msg_controllen >= CMSG_LEN(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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if ((e = memchr(buf, '\n', n)))
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if ((k = write_message(s, strstrip(buf), ucred)) < 0)
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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_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-kmsg-syslogd running as pid %lu", (unsigned long) getpid());
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"STATUS=Processing messages...");
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struct epoll_event event;
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if ((k = epoll_wait(server.epoll_fd, &event, 1, -1)) < 0) {
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log_error("epoll_wait() failed: %m");
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if ((k = process_event(&server, &event)) < 0)
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log_debug("systemd-kmsg-syslogd stopped as pid %lu", (unsigned long) getpid());
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"STATUS=Shutting down...");
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server_done(&server);
added
removed
src/kmsg-syslogd.c
