syslog: add minimal syslog/kmsg bridge syslogd

1 files changed, 545 insertions, 0 deletions

diff --git a/src/kmsg-syslogd.c b/src/kmsg-syslogd.c
new file mode 100644
index 0000000000..f5c8e7121d
--- /dev/null
+++ b/src/kmsg-syslogd.c
@@ -0,0 +1,545 @@
+/*-*- 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
+#define TIMEOUT ((int) (10*MSEC_PER_SEC))
+
+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 = 3, n;
+
+        if (getppid() != 1) {
+                log_error("This program should be invoked by init only.");
+                return 1;
+        }
+
+        if (argc > 1) {
+                log_error("This program does not take arguments.");
+                return 1;
+        }
+
+        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 1;
+        }
+
+        if (n <= 0 || n > SERVER_FD_MAX) {
+                log_error("No or too many file descriptors passed.");
+                return 2;
+        }
+
+        if (server_init(&server, (unsigned) n) < 0)
+                return 3;
+
+        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, TIMEOUT)) < 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 = 0;
+
+        log_debug("systemd-kmsg-syslogd stopped as pid %lu", (unsigned long) getpid());
+
+fail:
+        sd_notify(false,
+                  "STATUS=Shutting down...");
+
+        server_done(&server);
+
+        return r;
+}