4 files changed, 319 insertions, 0 deletions
diff --git a/Sources/Shared/Logging/Logger.swift b/Sources/Shared/Logging/Logger.swift
new file mode 100644
index 0000000..f3ee2b7
--- /dev/null
+++ b/Sources/Shared/Logging/Logger.swift
@@ -0,0 +1,65 @@
+// SPDX-License-Identifier: MIT
+// Copyright © 2018-2023 WireGuard LLC. All Rights Reserved.
+
+import Foundation
+import os.log
+
+public class Logger {
+    enum LoggerError: Error {
+        case openFailure
+    }
+
+    static var global: Logger?
+
+    var log: OpaquePointer
+    var tag: String
+
+    init(tagged tag: String, withFilePath filePath: String) throws {
+        guard let log = open_log(filePath) else { throw LoggerError.openFailure }
+        self.log = log
+        self.tag = tag
+    }
+
+    deinit {
+        close_log(self.log)
+    }
+
+    func log(message: String) {
+        write_msg_to_log(log, tag, message.trimmingCharacters(in: .newlines))
+    }
+
+    func writeLog(to targetFile: String) -> Bool {
+        return write_log_to_file(targetFile, self.log) == 0
+    }
+
+    static func configureGlobal(tagged tag: String, withFilePath filePath: String?) {
+        if Logger.global != nil {
+            return
+        }
+        guard let filePath = filePath else {
+            os_log("Unable to determine log destination path. Log will not be saved to file.", log: OSLog.default, type: .error)
+            return
+        }
+        guard let logger = try? Logger(tagged: tag, withFilePath: filePath) else {
+            os_log("Unable to open log file for writing. Log will not be saved to file.", log: OSLog.default, type: .error)
+            return
+        }
+        Logger.global = logger
+        var appVersion = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "Unknown version"
+        if let appBuild = Bundle.main.infoDictionary?["CFBundleVersion"] as? String {
+            appVersion += " (\(appBuild))"
+        }
+
+        Logger.global?.log(message: "App version: \(appVersion)")
+    }
+}
+
+func wg_log(_ type: OSLogType, staticMessage msg: StaticString) {
+    os_log(msg, log: OSLog.default, type: type)
+    Logger.global?.log(message: "\(msg)")
+}
+
+func wg_log(_ type: OSLogType, message msg: String) {
+    os_log("%{public}s", log: OSLog.default, type: type, msg)
+    Logger.global?.log(message: msg)
+}
diff --git a/Sources/Shared/Logging/ringlogger.c b/Sources/Shared/Logging/ringlogger.c
new file mode 100644
index 0000000..9bb0d13
--- /dev/null
+++ b/Sources/Shared/Logging/ringlogger.c
@@ -0,0 +1,173 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdatomic.h>
+#include <stdbool.h>
+#include <time.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <sys/mman.h>
+#include "ringlogger.h"
+
+enum {
+	MAX_LOG_LINE_LENGTH = 512,
+	MAX_LINES = 2048,
+	MAGIC = 0xabadbeefU
+};
+
+struct log_line {
+	atomic_uint_fast64_t time_ns;
+	char line[MAX_LOG_LINE_LENGTH];
+};
+
+struct log {
+	atomic_uint_fast32_t next_index;
+	struct log_line lines[MAX_LINES];
+	uint32_t magic;
+};
+
+void write_msg_to_log(struct log *log, const char *tag, const char *msg)
+{
+	uint32_t index;
+	struct log_line *line;
+	struct timespec ts;
+
+	// Race: This isn't synchronized with the fetch_add below, so items might be slightly out of order.
+	clock_gettime(CLOCK_REALTIME, &ts);
+
+	// Race: More than MAX_LINES writers and this will clash.
+	index = atomic_fetch_add(&log->next_index, 1);
+	line = &log->lines[index % MAX_LINES];
+
+	// Race: Before this line executes, we'll display old data after new data.
+	atomic_store(&line->time_ns, 0);
+	memset(line->line, 0, MAX_LOG_LINE_LENGTH);
+
+	snprintf(line->line, MAX_LOG_LINE_LENGTH, "[%s] %s", tag, msg);
+	atomic_store(&line->time_ns, ts.tv_sec * 1000000000ULL + ts.tv_nsec);
+
+	msync(&log->next_index, sizeof(log->next_index), MS_ASYNC);
+	msync(line, sizeof(*line), MS_ASYNC);
+}
+
+int write_log_to_file(const char *file_name, const struct log *input_log)
+{
+	struct log *log;
+	uint32_t l, i;
+	FILE *file;
+	int ret;
+
+	log = malloc(sizeof(*log));
+	if (!log)
+		return -errno;
+	memcpy(log, input_log, sizeof(*log));
+
+	file = fopen(file_name, "w");
+	if (!file) {
+		free(log);
+		return -errno;
+	}
+
+	for (l = 0, i = log->next_index; l < MAX_LINES; ++l, ++i) {
+		const struct log_line *line = &log->lines[i % MAX_LINES];
+		time_t seconds = line->time_ns / 1000000000ULL;
+		uint32_t useconds = (line->time_ns % 1000000000ULL) / 1000ULL;
+		struct tm tm;
+
+		if (!line->time_ns)
+			continue;
+
+		if (!localtime_r(&seconds, &tm))
+			goto err;
+
+		if (fprintf(file, "%04d-%02d-%02d %02d:%02d:%02d.%06d: %s\n",
+				  tm.tm_year + 1900, tm.tm_mon + 1, tm.tm_mday,
+				  tm.tm_hour, tm.tm_min, tm.tm_sec, useconds,
+				  line->line) < 0)
+			goto err;
+
+
+	}
+	errno = 0;
+
+err:
+	ret = -errno;
+	fclose(file);
+	free(log);
+	return ret;
+}
+
+uint32_t view_lines_from_cursor(const struct log *input_log, uint32_t cursor, void *ctx, void(*cb)(const char *, uint64_t, void *))
+{
+	struct log *log;
+	uint32_t l, i = cursor;
+
+	log = malloc(sizeof(*log));
+	if (!log)
+		return cursor;
+	memcpy(log, input_log, sizeof(*log));
+
+	if (i == -1)
+		i = log->next_index;
+
+	for (l = 0; l < MAX_LINES; ++l, ++i) {
+		const struct log_line *line = &log->lines[i % MAX_LINES];
+
+		if (cursor != -1 && i % MAX_LINES == log->next_index % MAX_LINES)
+			break;
+
+		if (!line->time_ns) {
+			if (cursor == -1)
+				continue;
+			else
+				break;
+		}
+		cb(line->line, line->time_ns, ctx);
+		cursor = (i + 1) % MAX_LINES;
+	}
+	free(log);
+	return cursor;
+}
+
+struct log *open_log(const char *file_name)
+{
+	int fd;
+	struct log *log;
+
+	fd = open(file_name, O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
+	if (fd < 0)
+		return NULL;
+	if (ftruncate(fd, sizeof(*log)))
+		goto err;
+	log = mmap(NULL, sizeof(*log), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (log == MAP_FAILED)
+		goto err;
+	close(fd);
+
+	if (log->magic != MAGIC) {
+		memset(log, 0, sizeof(*log));
+		log->magic = MAGIC;
+		msync(log, sizeof(*log), MS_ASYNC);
+	}
+
+	return log;
+
+err:
+	close(fd);
+	return NULL;
+}
+
+void close_log(struct log *log)
+{
+	munmap(log, sizeof(*log));
+}
diff --git a/Sources/Shared/Logging/ringlogger.h b/Sources/Shared/Logging/ringlogger.h
new file mode 100644
index 0000000..0e28c93
--- /dev/null
+++ b/Sources/Shared/Logging/ringlogger.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018-2023 WireGuard LLC. All Rights Reserved.
+ */
+
+#ifndef RINGLOGGER_H
+#define RINGLOGGER_H
+
+#include <stdint.h>
+
+struct log;
+void write_msg_to_log(struct log *log, const char *tag, const char *msg);
+int write_log_to_file(const char *file_name, const struct log *input_log);
+uint32_t view_lines_from_cursor(const struct log *input_log, uint32_t cursor, void *ctx, void(*)(const char *, uint64_t, void *));
+struct log *open_log(const char *file_name);
+void close_log(struct log *log);
+
+#endif
diff --git a/Sources/Shared/Logging/test_ringlogger.c b/Sources/Shared/Logging/test_ringlogger.c
new file mode 100644
index 0000000..ae3f4a9
--- /dev/null
+++ b/Sources/Shared/Logging/test_ringlogger.c
@@ -0,0 +1,63 @@
+#include "ringlogger.h"
+#include <stdio.h>
+#include <stdbool.h>
+#include <string.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include <sys/wait.h>
+
+static void forkwrite(void)
+{
+	struct log *log = open_log("/tmp/test_log");
+	char c[512];
+	int i, base;
+	bool in_fork = !fork();
+
+	base = 10000 * in_fork;
+	for (i = 0; i < 1024; ++i) {
+		snprintf(c, 512, "bla bla bla %d", base + i);
+		write_msg_to_log(log, "HMM", c);
+	}
+
+
+	if (in_fork)
+		_exit(0);
+	wait(NULL);
+
+	write_log_to_file("/dev/stdout", log);
+	close_log(log);
+}
+
+static void writetext(const char *text)
+{
+	struct log *log = open_log("/tmp/test_log");
+	write_msg_to_log(log, "TXT", text);
+	close_log(log);
+}
+
+static void show_line(const char *line, uint64_t time_ns)
+{
+	printf("%" PRIu64 ": %s\n", time_ns, line);
+}
+
+static void follow(void)
+{
+	uint32_t cursor = -1;
+	struct log *log = open_log("/tmp/test_log");
+
+	for (;;) {
+		cursor = view_lines_from_cursor(log, cursor, show_line);
+		usleep(1000 * 300);
+	}
+}
+
+int main(int argc, char *argv[])
+{
+	if (!strcmp(argv[1], "fork"))
+		forkwrite();
+	else if (!strcmp(argv[1], "write"))
+		writetext(argv[2]);
+	else if (!strcmp(argv[1], "follow"))
+		follow();
+	return 0;
+}