diff --git a/WireGuard/Shared/RingLogger/ringlogger.c b/WireGuard/Shared/RingLogger/ringlogger.c
new file mode 100644
index 0000000..d39b9d7
--- /dev/null
+++ b/WireGuard/Shared/RingLogger/ringlogger.c
@@ -0,0 +1,125 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018 WireGuard LLC. All Rights Reserved.
+ */
+
+#include <string.h>
+#include <stdio.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <stdbool.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 = 1024,
+	MAGIC = 0xdeadbeefU
+};
+
+struct log_line {
+	struct timeval tv;
+	char line[MAX_LOG_LINE_LENGTH];
+};
+
+struct log {
+	struct { uint32_t first, len; } header;
+	struct log_line lines[MAX_LINES];
+	uint32_t magic;
+};
+
+void write_msg_to_log(struct log *log, const char *msg)
+{
+	struct log_line *line = &log->lines[(log->header.first + log->header.len) % MAX_LINES];
+
+	if (log->header.len == MAX_LINES)
+		log->header.first = (log->header.first + 1) % MAX_LINES;
+	else
+		++log->header.len;
+
+	gettimeofday(&line->tv, NULL);
+	strncpy(line->line, msg, MAX_LOG_LINE_LENGTH - 1);
+	line->line[MAX_LOG_LINE_LENGTH - 1] = '\0';
+
+	msync(&log->header, sizeof(log->header), MS_ASYNC);
+	msync(line, sizeof(*line), MS_ASYNC);
+}
+
+static bool first_before_second(const struct log_line *line1, const struct log_line *line2)
+{
+	if (line1->tv.tv_sec <= line2->tv.tv_sec)
+		return true;
+	else if (line1->tv.tv_sec == line2->tv.tv_sec)
+		return line1->tv.tv_usec <= line2->tv.tv_usec;
+	return false;
+}
+
+int write_logs_to_file(const char *file_name, const struct log *log1, const struct log *log2)
+{
+	uint32_t i1, i2, len1 = log1->header.len, len2 = log2->header.len;
+	char buf[MAX_LOG_LINE_LENGTH];
+	FILE *file;
+
+	if (len1 > MAX_LINES)
+		len1 = MAX_LINES;
+	if (len2 > MAX_LINES)
+		len2 = MAX_LINES;
+
+	file = fopen(file_name, "w");
+	if (!file)
+		return -errno;
+
+	for (i1 = 0, i2 = 0;;) {
+		const struct log_line *line1 = &log1->lines[(log1->header.first + i1) % MAX_LINES];
+		const struct log_line *line2 = &log2->lines[(log2->header.first + i2) % MAX_LINES];
+		const struct log_line *line;
+
+		if (i1 < len1 && (i2 >= len2 || first_before_second(line1, line2))) {
+			line = line1;
+			++i1;
+		} else if (i2 < len2 && (i1 >= len1 || first_before_second(line2, line1))) {
+			line = line2;
+			++i2;
+		} else {
+			break;
+		}
+		memcpy(buf, line->line, MAX_LOG_LINE_LENGTH);
+		buf[MAX_LOG_LINE_LENGTH - 1] = '\0';
+		if (fprintf(file, "%lu.%06d: %s\n", line->tv.tv_sec, line->tv.tv_usec, buf) < 0) {
+			int ret = -errno;
+			fclose(file);
+			return ret;
+		}
+	}
+	fclose(file);
+	return 0;
+}
+
+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)))
+		return NULL;
+	log = mmap(NULL, sizeof(*log), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
+	if (log == MAP_FAILED)
+		return NULL;
+	close(fd);
+
+	if (log->magic != MAGIC) {
+		memset(log, 0, sizeof(*log));
+		log->magic = MAGIC;
+		msync(log, sizeof(*log), MS_ASYNC);
+	}
+
+	return log;
+}
diff --git a/WireGuard/Shared/RingLogger/ringlogger.h b/WireGuard/Shared/RingLogger/ringlogger.h
new file mode 100644
index 0000000..d90e0c5
--- /dev/null
+++ b/WireGuard/Shared/RingLogger/ringlogger.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: MIT
+ *
+ * Copyright © 2018 WireGuard LLC. All Rights Reserved.
+ */
+
+#ifndef RINGLOGGER_H
+#define RINGLOGGER_H
+
+struct log;
+void write_msg_to_log(struct log *log, const char *msg);
+int write_logs_to_file(const char *file_name, const struct log *log1, const struct log *log2);
+struct log *open_log(const char *file_name);
+
+#endif