// SPDX-License-Identifier: AGPL-3.0-or-later

/* PASST - Plug A Simple Socket Transport
 *  for qemu/UNIX domain socket mode
 *
 * PASTA - Pack A Subtle Tap Abstraction
 *  for network namespace/tap device mode
 *
 * log.c - Logging functions
 *
 * Copyright (c) 2020-2022 Red Hat GmbH
 * Author: Stefano Brivio <sbrivio@redhat.com>
 */

#include <arpa/inet.h>
#include <limits.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <time.h>
#include <syslog.h>
#include <stdarg.h>
#include <sys/socket.h>

#include "log.h"
#include "util.h"
#include "passt.h"

static int	log_sock = -1;		/* Optional socket to system logger */
static char	log_ident[BUFSIZ];	/* Identifier string for openlog() */
static int	log_mask;		/* Current log priority mask */
static int	log_opt;		/* Options for openlog() */
static int	log_daemon_mode = false; /* true once process is daemonized */

static int	log_file = -1;		/* Optional log file descriptor */
static size_t	log_size;		/* Maximum log file size in bytes */
static size_t	log_written;		/* Currently used bytes in log file */
static size_t	log_cut_size;		/* Bytes to cut at start on rotation */
static char	log_header[BUFSIZ];	/* File header, written back on cuts */

static time_t	log_start;		/* Start timestamp */
int		log_trace;		/* --trace mode enabled */

#define logfn(name, level)						\
void name(const char *format, ...) {					\
	struct timespec tp;						\
	va_list args;							\
									\
	if (setlogmask(0) & LOG_MASK(LOG_DEBUG) && log_file == -1) {	\
		clock_gettime(CLOCK_REALTIME, &tp);			\
		fprintf(stderr, "%li.%04li: ",				\
			tp.tv_sec - log_start,				\
			tp.tv_nsec / (100L * 1000));			\
	}								\
									\
	if ((LOG_MASK(LOG_PRI(level)) & log_mask) ||			\
	    setlogmask(0) == LOG_MASK(LOG_EMERG)) {			\
		va_start(args, format);					\
		if (log_file != -1)					\
			logfile_write(level, format, args);		\
		else if (!(setlogmask(0) & LOG_MASK(LOG_DEBUG)))	\
			passt_vsyslog(level, format, args);		\
		va_end(args);						\
	}								\
									\
	if ((setlogmask(0) & LOG_MASK(LOG_DEBUG) ||			\
	     setlogmask(0) == LOG_MASK(LOG_EMERG))			\
	     && (log_file == -1 || !log_daemon_mode)) {			\
		va_start(args, format);					\
		(void)vfprintf(stderr, format, args); 			\
		va_end(args);						\
		if (format[strlen(format)] != '\n')			\
			fprintf(stderr, "\n");				\
	}								\
}

/* Prefixes for log file messages, indexed by priority */
const char *logfile_prefix[] = {
	NULL, NULL, NULL,	/* Unused: LOG_EMERG, LOG_ALERT, LOG_CRIT */
	"ERROR:   ",
	"WARNING: ",
	NULL,			/* Unused: LOG_NOTICE */
	"info:    ",
	"         ",		/* LOG_DEBUG */
};

logfn(err,   LOG_ERR)
logfn(warn,  LOG_WARNING)
logfn(info,  LOG_INFO)
logfn(debug, LOG_DEBUG)

/**
 * log_go_daemon() - tell logging subsystem that the process has been
 *		     been daemonized, so it stop logging to stderr
 *		     if appropriate.
 */
void log_go_daemon(void)
{
	log_daemon_mode = true;
}

/**
 * trace_init() - Set log_trace depending on trace (debug) mode
 * @enable:	Tracing debug mode enabled if non-zero
 */
void trace_init(int enable)
{
	log_trace = enable;
}

/**
 * __openlog() - Non-optional openlog() wrapper, to allow custom vsyslog()
 * @ident:	openlog() identity (program name)
 * @option:	openlog() options
 * @facility:	openlog() facility (LOG_DAEMON)
 */
void __openlog(const char *ident, int option, int facility)
{
	struct timespec tp;

	clock_gettime(CLOCK_REALTIME, &tp);
	log_start = tp.tv_sec;

	if (log_sock < 0) {
		struct sockaddr_un a = { .sun_family = AF_UNIX, };

		log_sock = socket(AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0);
		if (log_sock < 0)
			return;

		strncpy(a.sun_path, _PATH_LOG, sizeof(a.sun_path));
		if (connect(log_sock, (const struct sockaddr *)&a, sizeof(a))) {
			close(log_sock);
			log_sock = -1;
			return;
		}
	}

	log_mask |= facility;
	strncpy(log_ident, ident, sizeof(log_ident) - 1);
	log_opt = option;

	openlog(ident, option, facility);
}

/**
 * __setlogmask() - setlogmask() wrapper, to allow custom vsyslog()
 * @mask:	Same as setlogmask() mask
 */
void __setlogmask(int mask)
{
	log_mask = mask;
	setlogmask(mask);
}

/**
 * passt_vsyslog() - vsyslog() implementation not using heap memory
 * @pri:	Facility and level map, same as priority for vsyslog()
 * @format:	Same as vsyslog() format
 * @ap:		Same as vsyslog() ap
 */
void passt_vsyslog(int pri, const char *format, va_list ap)
{
	char buf[BUFSIZ];
	int n;

	/* Send without name and timestamp, the system logger should add them */
	n = snprintf(buf, BUFSIZ, "<%i> ", pri);

	n += vsnprintf(buf + n, BUFSIZ - n, format, ap);

	if (format[strlen(format)] != '\n')
		n += snprintf(buf + n, BUFSIZ - n, "\n");

	if (log_opt & LOG_PERROR)
		fprintf(stderr, "%s", buf + sizeof("<0>"));

	if (send(log_sock, buf, n, 0) != n)
		fprintf(stderr, "Failed to send %i bytes to syslog\n", n);
}

/**
 * logfile_init() - Open log file and write header with PID, version, path
 * @name:	Identifier for header: passt or pasta
 * @path:	Path to log file
 * @size:	Maximum size of log file: log_cut_size is calculatd here
 */
void logfile_init(const char *name, const char *path, size_t size)
{
	char nl = '\n', exe[PATH_MAX] = { 0 };
	int n;

	if (readlink("/proc/self/exe", exe, PATH_MAX - 1) < 0) {
		perror("readlink /proc/self/exe");
		exit(EXIT_FAILURE);
	}

	log_file = open(path, O_CREAT | O_TRUNC | O_APPEND | O_RDWR | O_CLOEXEC,
			S_IRUSR | S_IWUSR);
	if (log_file == -1) {
		err("Couldn't open log file %s: %s", path, strerror(errno));
		exit(EXIT_FAILURE);
	}

	log_size = size ? size : LOGFILE_SIZE_DEFAULT;

	n = snprintf(log_header, sizeof(log_header), "%s " VERSION ": %s (%i)",
		     name, exe, getpid());

	if (write(log_file, log_header, n) <= 0 ||
	    write(log_file, &nl, 1) <= 0) {
		perror("Couldn't write to log file\n");
		exit(EXIT_FAILURE);
	}

	/* For FALLOC_FL_COLLAPSE_RANGE: VFS block size can be up to one page */
	log_cut_size = ROUND_UP(log_size * LOGFILE_CUT_RATIO / 100, PAGE_SIZE);
}

#ifdef FALLOC_FL_COLLAPSE_RANGE
/**
 * logfile_rotate_fallocate() - Write header, set log_written after fallocate()
 * @fd:		Log file descriptor
 * @ts:		Current timestamp
 *
 * #syscalls lseek ppc64le:_llseek ppc64:_llseek armv6l:_llseek armv7l:_llseek
 */
static void logfile_rotate_fallocate(int fd, struct timespec *ts)
{
	char buf[BUFSIZ], *nl;
	int n;

	if (lseek(fd, 0, SEEK_SET) == -1)
		return;
	if (read(fd, buf, BUFSIZ) == -1)
		return;

	n = snprintf(buf, BUFSIZ,
		     "%s - log truncated at %li.%04li", log_header,
		     ts->tv_sec - log_start, ts->tv_nsec / (100L * 1000));

	/* Avoid partial lines by padding the header with spaces */
	nl = memchr(buf + n + 1, '\n', BUFSIZ - n - 1);
	if (nl)
		memset(buf + n, ' ', nl - (buf + n));

	if (lseek(fd, 0, SEEK_SET) == -1)
		return;
	if (write(fd, buf, BUFSIZ) == -1)
		return;

	log_written -= log_cut_size;
}
#endif /* FALLOC_FL_COLLAPSE_RANGE */

/**
 * logfile_rotate_move() - Fallback: move recent entries toward start, then cut
 * @fd:		Log file descriptor
 * @ts:		Current timestamp
 *
 * #syscalls lseek ppc64le:_llseek ppc64:_llseek armv6l:_llseek armv7l:_llseek
 * #syscalls ftruncate
 */
static void logfile_rotate_move(int fd, struct timespec *ts)
{
	int header_len, write_offset, end, discard, n;
	char buf[BUFSIZ], *nl;

	header_len = snprintf(buf, BUFSIZ,
			      "%s - log truncated at %li.%04li\n", log_header,
			      ts->tv_sec - log_start,
			      ts->tv_nsec / (100L * 1000));
	if (lseek(fd, 0, SEEK_SET) == -1)
		return;
	if (write(fd, buf, header_len) == -1)
		return;

	end = write_offset = header_len;
	discard = log_cut_size + header_len;

	/* Try to cut cleanly at newline */
	if (lseek(fd, discard, SEEK_SET) == -1)
		goto out;
	if ((n = read(fd, buf, BUFSIZ)) <= 0)
		goto out;
	if ((nl = memchr(buf, '\n', n)))
		discard += (nl - buf) + 1;

	/* Go to first block to be moved */
	if (lseek(fd, discard, SEEK_SET) == -1)
		goto out;

	while ((n = read(fd, buf, BUFSIZ)) > 0) {
		end = header_len;

		if (lseek(fd, write_offset, SEEK_SET) == -1)
			goto out;
		if ((n = write(fd, buf, n)) == -1)
			goto out;
		write_offset += n;

		if ((n = lseek(fd, 0, SEEK_CUR)) == -1)
			goto out;

		if (lseek(fd, discard - header_len, SEEK_CUR) == -1)
			goto out;

		end = n;
	}

out:
	if (ftruncate(fd, end))
		return;

	log_written = end;
}

/**
 * logfile_rotate() - "Rotate" log file once it's full
 * @fd:		Log file descriptor
 * @ts:		Current timestamp
 *
 * Return: 0 on success, negative error code on failure
 *
 * #syscalls fcntl
 *
 * fallocate() passed as EXTRA_SYSCALL only if FALLOC_FL_COLLAPSE_RANGE is there
 */
static int logfile_rotate(int fd, struct timespec *ts)
{
	if (fcntl(fd, F_SETFL, O_RDWR /* Drop O_APPEND: explicit lseek() */))
		return -errno;

#ifdef FALLOC_FL_COLLAPSE_RANGE
	/* Only for Linux >= 3.15, extent-based ext4 or XFS, glibc >= 2.18 */
	if (!fallocate(fd, FALLOC_FL_COLLAPSE_RANGE, 0, log_cut_size))
		logfile_rotate_fallocate(fd, ts);
	else
#endif
		logfile_rotate_move(fd, ts);

	if (fcntl(fd, F_SETFL, O_RDWR | O_APPEND))
		return -errno;

	return 0;
}

/**
 * logfile_write() - Write entry to log file, trigger rotation if full
 * @pri:	Facility and level map, same as priority for vsyslog()
 * @format:	Same as vsyslog() format
 * @ap:		Same as vsyslog() ap
 */
void logfile_write(int pri, const char *format, va_list ap)
{
	struct timespec ts;
	char buf[BUFSIZ];
	int n;

	if (clock_gettime(CLOCK_REALTIME, &ts))
		return;

	n = snprintf(buf, BUFSIZ, "%li.%04li: %s",
		     ts.tv_sec - log_start, ts.tv_nsec / (100L * 1000),
		     logfile_prefix[pri]);

	n += vsnprintf(buf + n, BUFSIZ - n, format, ap);

	if (format[strlen(format)] != '\n')
		n += snprintf(buf + n, BUFSIZ - n, "\n");

	if ((log_written + n >= log_size) && logfile_rotate(log_file, &ts))
		return;

	if ((n = write(log_file, buf, n)) >= 0)
		log_written += n;
}