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Systemd/src/kmsg-syslogd.c
Lennart Poettering b670e92b50 syslog: make sure the kmsg bridge is always pulled in and never terminated automatically 
Since we want to replace the bridge dynamically by the real syslog
implementation such as rsyslog we need to make sure that the the bridge
stays running right to the moment rsyslog is up so that we process
messages enqueued by other processes started before rsyslog, so that
those clients don't stay stuck.
2011-03-07 21:56:13 +01:00

545 lines
14 KiB
C
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/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
systemd 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
General Public License for more details.
You should have received a copy of the GNU General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#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 <fcntl.h>
#include <sys/signalfd.h>
#include "util.h"
#include "log.h"
#include "sd-daemon.h"
#include "fdset.h"
#define SERVER_FD_MAX 16
typedef struct Stream Stream;
typedef struct Server {
FDSet *syslog_fds;
int kmsg_fd;
int epoll_fd;
int signal_fd;
} Server;
static void server_done(Server *s) {
assert(s);
if (s->epoll_fd >= 0)
close_nointr_nofail(s->epoll_fd);
if (s->kmsg_fd >= 0)
close_nointr_nofail(s->kmsg_fd);
if (s->signal_fd >= 0)
close_nointr_nofail(s->signal_fd);
if (s->syslog_fds)
fdset_free(s->syslog_fds);
}
static int server_init(Server *s, unsigned n_sockets) {
int r;
unsigned i;
struct epoll_event ev;
sigset_t mask;
assert(s);
assert(n_sockets > 0);
zero(*s);
s->kmsg_fd = s->signal_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;
}
if (!(s->syslog_fds = fdset_new())) {
r = -ENOMEM;
log_error("Failed to allocate file descriptor set: %s", strerror(errno));
goto fail;
}
for (i = 0; i < n_sockets; i++) {
int fd, one = 1;
fd = SD_LISTEN_FDS_START+i;
if ((r = sd_is_socket(fd, AF_UNSPEC, SOCK_DGRAM, -1)) < 0) {
log_error("Failed to determine file descriptor type: %s", strerror(-r));
goto fail;
}
if (!r) {
log_error("Wrong file descriptor type.");
r = -EINVAL;
goto fail;
}
if (setsockopt(fd, SOL_SOCKET, SO_PASSCRED, &one, sizeof(one)) < 0)
log_error("SO_PASSCRED failed: %m");
zero(ev);
ev.events = EPOLLIN;
ev.data.fd = fd;
if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {
r = -errno;
log_error("Failed to add server fd to epoll object: %s", strerror(errno));
goto fail;
}
if ((r = fdset_put(s->syslog_fds, fd)) < 0) {
log_error("Failed to store file descriptor in set: %s", strerror(-r));
goto fail;
}
}
if ((s->kmsg_fd = open("/dev/kmsg", O_WRONLY|O_NOCTTY|O_CLOEXEC)) < 0) {
log_error("Failed to open /dev/kmsg for logging: %m");
return -errno;
}
assert_se(sigemptyset(&mask) == 0);
sigset_add_many(&mask, SIGINT, SIGTERM, -1);
assert_se(sigprocmask(SIG_SETMASK, &mask, NULL) == 0);
if ((s->signal_fd = signalfd(-1, &mask, SFD_NONBLOCK|SFD_CLOEXEC)) < 0) {
log_error("signalfd(): %m");
return -errno;
}
zero(ev);
ev.events = EPOLLIN;
ev.data.fd = s->signal_fd;
if (epoll_ctl(s->epoll_fd, EPOLL_CTL_ADD, s->signal_fd, &ev) < 0) {
log_error("epoll_ctl(): %m");
return -errno;
}
return 0;
fail:
server_done(s);
return r;
}
static int read_priority(const char **buf) {
int priority;
size_t n;
const char *p;
int a, b, c;
assert(buf);
assert(*buf);
p = *buf;
n = strlen(p);
if (n < 3 || p[0] != '<')
goto fail;
if (p[2] == '>') {
a = b = 0;
c = undecchar(p[1]);
p += 3;
} else if (n >= 4 && p[3] == '>') {
a = 0;
b = undecchar(p[1]);
c = undecchar(p[2]);
p += 4;
} else if (n >= 5 && p[4] == '>') {
a = undecchar(p[1]);
b = undecchar(p[2]);
c = undecchar(p[3]);
p += 5;
} else
goto fail;
if (a < 0 || b < 0 || c < 0)
goto fail;
*buf = p;
priority = 100*a + 10*b + c;
return LOG_PRI(priority);
fail:
return LOG_INFO;
}
static void skip_date(const char **buf) {
enum {
LETTER,
SPACE,
NUMBER,
SPACE_OR_NUMBER,
COLON
} sequence[] = {
LETTER, LETTER, LETTER,
SPACE,
SPACE_OR_NUMBER, NUMBER,
SPACE,
SPACE_OR_NUMBER, NUMBER,
COLON,
SPACE_OR_NUMBER, NUMBER,
COLON,
SPACE_OR_NUMBER, NUMBER,
SPACE
};
const char *p;
unsigned i;
assert(buf);
assert(*buf);
p = *buf;
for (i = 0; i < ELEMENTSOF(sequence); i++, p++) {
if (!*p)
return;
switch (sequence[i]) {
case SPACE:
if (*p != ' ')
return;
break;
case SPACE_OR_NUMBER:
if (*p == ' ')
break;
/* fall through */
case NUMBER:
if (*p < '0' || *p > '9')
return;
break;
case LETTER:
if (!(*p >= 'A' && *p <= 'Z') &&
!(*p >= 'a' && *p <= 'z'))
return;
break;
case COLON:
if (*p != ':')
return;
break;
}
}
*buf = p;
}
static int read_process(const char **buf, struct iovec *iovec) {
const char *p;
size_t l;
assert(buf);
assert(*buf);
assert(iovec);
p = *buf;
p += strspn(p, WHITESPACE);
l = strcspn(p, WHITESPACE);
if (l <= 0 ||
p[l-1] != ':')
return 0;
l--;
if (p[l-1] == ']') {
size_t k = l-1;
for (;;) {
if (p[k] == '[') {
l = k;
break;
}
if (k == 0)
break;
k--;
}
}
iovec->iov_base = (char*) p;
iovec->iov_len = l;
*buf = p + l;
return 1;
}
static void skip_pid(const char **buf) {
const char *p;
assert(buf);
assert(*buf);
p = *buf;
if (*p != '[')
return;
p++;
p += strspn(p, "0123456789");
if (*p != ']')
return;
p++;
*buf = p;
}
static int write_message(Server *s, const char *buf, struct ucred *ucred) {
ssize_t k;
char priority[4], pid[16];
struct iovec iovec[5];
unsigned i = 0;
char *process = NULL;
int r = 0;
assert(s);
assert(buf);
/* First, set priority field */
snprintf(priority, sizeof(priority), "<%i>", read_priority(&buf));
char_array_0(priority);
IOVEC_SET_STRING(iovec[i++], priority);
/* Second, skip date */
skip_date(&buf);
/* Then, add process if set */
if (read_process(&buf, &iovec[i]) > 0)
i++;
else if (ucred && get_process_name(ucred->pid, &process) >= 0)
IOVEC_SET_STRING(iovec[i++], process);
/* Skip the stored PID if we have a better one */
if (ucred) {
snprintf(pid, sizeof(pid), "[%lu]: ", (unsigned long) ucred->pid);
char_array_0(pid);
IOVEC_SET_STRING(iovec[i++], pid);
skip_pid(&buf);
if (*buf == ':')
buf++;
buf += strspn(buf, WHITESPACE);
}
/* Is the remaining message empty? */
if (*buf) {
/* And the rest is the message */
IOVEC_SET_STRING(iovec[i++], buf);
IOVEC_SET_STRING(iovec[i++], "\n");
if ((k = writev(s->kmsg_fd, iovec, i)) <= 0) {
log_error("Failed to write log message to kmsg: %s", k < 0 ? strerror(errno) : "short write");
r = k < 0 ? -errno : -EIO;
}
}
free(process);
return r;
}
static int process_event(Server *s, struct epoll_event *ev) {
assert(s);
if (ev->events != EPOLLIN) {
log_info("Got invalid event from epoll.");
return -EIO;
}
if (ev->data.fd == s->signal_fd) {
struct signalfd_siginfo sfsi;
ssize_t n;
if ((n = read(s->signal_fd, &sfsi, sizeof(sfsi))) != sizeof(sfsi)) {
if (n >= 0)
return -EIO;
if (errno == EINTR || errno == EAGAIN)
return 0;
return -errno;
}
log_debug("Received SIG%s", strna(signal_to_string(sfsi.ssi_signo)));
return 0;
} else {
for (;;) {
char buf[LINE_MAX+1];
struct msghdr msghdr;
struct iovec iovec;
struct ucred *ucred;
union {
struct cmsghdr cmsghdr;
uint8_t buf[CMSG_SPACE(sizeof(struct ucred))];
} control;
ssize_t n;
int k;
char *e;
zero(iovec);
iovec.iov_base = buf;
iovec.iov_len = sizeof(buf)-1;
zero(control);
zero(msghdr);
msghdr.msg_iov = &iovec;
msghdr.msg_iovlen = 1;
msghdr.msg_control = &control;
msghdr.msg_controllen = sizeof(control);
if ((n = recvmsg(ev->data.fd, &msghdr, MSG_DONTWAIT)) < 0) {
if (errno == EINTR || errno == EAGAIN)
return 1;
log_error("recvmsg() failed: %m");
return -errno;
}
if (msghdr.msg_controllen >= CMSG_LEN(sizeof(struct ucred)) &&
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);
else
ucred = NULL;
if ((e = memchr(buf, '\n', n)))
*e = 0;
else
buf[n] = 0;
if ((k = write_message(s, strstrip(buf), ucred)) < 0)
return k;
}
}
return 1;
}
int main(int argc, char *argv[]) {
Server server;
int r = EXIT_FAILURE, n;
if (getppid() != 1) {
log_error("This program should be invoked by init only.");
return EXIT_FAILURE;
}
if (argc > 1) {
log_error("This program does not take arguments.");
return EXIT_FAILURE;
}
log_set_target(LOG_TARGET_KMSG);
log_parse_environment();
log_open();
if ((n = sd_listen_fds(true)) < 0) {
log_error("Failed to read listening file descriptors from environment: %s", strerror(-r));
return EXIT_FAILURE;
}
if (n <= 0 || n > SERVER_FD_MAX) {
log_error("No or too many file descriptors passed.");
return EXIT_FAILURE;
}
if (server_init(&server, (unsigned) n) < 0)
return EXIT_FAILURE;
log_debug("systemd-kmsg-syslogd running as pid %lu", (unsigned long) getpid());
sd_notify(false,
"READY=1\n"
"STATUS=Processing messages...");
for (;;) {
struct epoll_event event;
int k;
if ((k = epoll_wait(server.epoll_fd, &event, 1, -1)) < 0) {
if (errno == EINTR)
continue;
log_error("epoll_wait() failed: %m");
goto fail;
}
if (k <= 0)
break;
if ((k = process_event(&server, &event)) < 0)
goto fail;
if (k == 0)
break;
}
r = EXIT_SUCCESS;
log_debug("systemd-kmsg-syslogd stopped as pid %lu", (unsigned long) getpid());
fail:
sd_notify(false,
"STATUS=Shutting down...");
server_done(&server);
return r;
}
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