Index: sys/netinet/tcp.h
===================================================================
--- sys/netinet/tcp.h
+++ sys/netinet/tcp.h
@@ -278,9 +278,6 @@
  * left for growth.  In order to maximize potential future compatibility with
  * the Linux API, the same variable names and order have been adopted, and
  * padding left to make room for omitted fields in case they are added later.
- *
- * XXX: This is currently an unstable ABI/API, in that it is expected to
- * change.
  */
 struct tcp_info {
 	u_int8_t	tcpi_state;		/* TCP FSM state. */
@@ -335,6 +332,7 @@
 	/* Padding to grow without breaking ABI. */
 	u_int32_t	__tcpi_pad[26];		/* Padding. */
 };
+_Static_assert(sizeof(struct tcp_info) == 236, "tcp_info ABI mismatch");
 
 /*
  * If this structure is provided when setting the TCP_FASTOPEN socket