v4.19.13 snapshot.
diff --git a/include/uapi/linux/tcp_metrics.h b/include/uapi/linux/tcp_metrics.h
new file mode 100644
index 0000000..7cb4a17
--- /dev/null
+++ b/include/uapi/linux/tcp_metrics.h
@@ -0,0 +1,61 @@
+/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
+/* tcp_metrics.h - TCP Metrics Interface */
+
+#ifndef _LINUX_TCP_METRICS_H
+#define _LINUX_TCP_METRICS_H
+
+#include <linux/types.h>
+
+/* NETLINK_GENERIC related info
+ */
+#define TCP_METRICS_GENL_NAME		"tcp_metrics"
+#define TCP_METRICS_GENL_VERSION	0x1
+
+enum tcp_metric_index {
+	TCP_METRIC_RTT,		/* in ms units */
+	TCP_METRIC_RTTVAR,	/* in ms units */
+	TCP_METRIC_SSTHRESH,
+	TCP_METRIC_CWND,
+	TCP_METRIC_REORDERING,
+
+	TCP_METRIC_RTT_US,	/* in usec units */
+	TCP_METRIC_RTTVAR_US,	/* in usec units */
+
+	/* Always last.  */
+	__TCP_METRIC_MAX,
+};
+
+#define TCP_METRIC_MAX	(__TCP_METRIC_MAX - 1)
+
+enum {
+	TCP_METRICS_ATTR_UNSPEC,
+	TCP_METRICS_ATTR_ADDR_IPV4,		/* u32 */
+	TCP_METRICS_ATTR_ADDR_IPV6,		/* binary */
+	TCP_METRICS_ATTR_AGE,			/* msecs */
+	TCP_METRICS_ATTR_TW_TSVAL,		/* u32, raw, rcv tsval */
+	TCP_METRICS_ATTR_TW_TS_STAMP,		/* s32, sec age */
+	TCP_METRICS_ATTR_VALS,			/* nested +1, u32 */
+	TCP_METRICS_ATTR_FOPEN_MSS,		/* u16 */
+	TCP_METRICS_ATTR_FOPEN_SYN_DROPS,	/* u16, count of drops */
+	TCP_METRICS_ATTR_FOPEN_SYN_DROP_TS,	/* msecs age */
+	TCP_METRICS_ATTR_FOPEN_COOKIE,		/* binary */
+	TCP_METRICS_ATTR_SADDR_IPV4,		/* u32 */
+	TCP_METRICS_ATTR_SADDR_IPV6,		/* binary */
+	TCP_METRICS_ATTR_PAD,
+
+	__TCP_METRICS_ATTR_MAX,
+};
+
+#define TCP_METRICS_ATTR_MAX	(__TCP_METRICS_ATTR_MAX - 1)
+
+enum {
+	TCP_METRICS_CMD_UNSPEC,
+	TCP_METRICS_CMD_GET,
+	TCP_METRICS_CMD_DEL,
+
+	__TCP_METRICS_CMD_MAX,
+};
+
+#define TCP_METRICS_CMD_MAX	(__TCP_METRICS_CMD_MAX - 1)
+
+#endif /* _LINUX_TCP_METRICS_H */