Index: head/lib/libc/sys/sendfile.2
===================================================================
--- head/lib/libc/sys/sendfile.2
+++ head/lib/libc/sys/sendfile.2
@@ -431,3 +431,12 @@
 .Er EFAULT ,
 if provided an invalid address for
 .Fa sbytes .
+The
+.Fn sendfile
+system call does not support SCTP sockets,
+it will return
+.Dv -1
+and set
+.Va errno
+to
+.Er EINVAL.
Index: head/sys/kern/kern_sendfile.c
===================================================================
--- head/sys/kern/kern_sendfile.c
+++ head/sys/kern/kern_sendfile.c
@@ -575,6 +575,12 @@
 	*so = (*sock_fp)->f_data;
 	if ((*so)->so_type != SOCK_STREAM)
 		return (EINVAL);
+	/*
+	 * SCTP one-to-one style sockets currently don't work with
+	 * sendfile(). So indicate EINVAL for now.
+	 */
+	if ((*so)->so_proto->pr_protocol == IPPROTO_SCTP)
+		return (EINVAL);
 	if (SOLISTENING(*so))
 		return (ENOTCONN);
 	return (0);