--- a/include/mptcpd/private/sockaddr.h	2022-07-24 18:29:37.995613204 +0200
+++ b/include/mptcpd/private/sockaddr.h	2022-07-24 18:30:53.802312010 +0200
@@ -24,6 +24,16 @@
  * These macros may be used in place of @c htons() or @c htonl() when
  * initializing an IPv4 address or IP port constant at compile-time.
  */
+#ifndef __bswap_constant_16
+#define __bswap_constant_16(x) \
+	((((x) >> 8) & 0xff) | (((x) & 0xff) << 8))
+#endif
+#ifndef __bswap_constant_32
+#define __bswap_constant_32(x) \
+	((((x) & 0xff000000u) >> 24) | (((x) & 0x00ff0000u) >> 8) \
+	| (((x) & 0x0000ff00u) << 8) | (((x) & 0x000000ffu) << 24))
+#endif
+
 ///@{
 #if __BYTE_ORDER == __LITTLE_ENDIAN
 # define MPTCPD_CONSTANT_HTONS(hs) __bswap_constant_16(hs)