diff --git a/bin/tests/system/ifconfig.sh b/bin/tests/system/ifconfig.sh
index aab6eb534b..fe410ecd5a 100755
--- a/bin/tests/system/ifconfig.sh
+++ b/bin/tests/system/ifconfig.sh
@@ -92,13 +92,7 @@ case "$1" in
 				[ "$ipv6" ] && ifconfig lo0 inet6 \
 					fd92:7065:b8e:${ipv6}ff::$ns alias
 				;;
-			    *-unknown-netbsd*)
-				ifconfig lo0 10.53.$i.$ns alias \
-					netmask 255.255.255.0
-				[ "$ipv6" ] && ifconfig lo0 inet6 \
-					fd92:7065:b8e:${ipv6}ff::$ns alias
-				;;
-			    *-unknown-openbsd*)
+			    *-unknown-dragonfly*|*-unknown-netbsd*|*-unknown-openbsd*)
 				ifconfig lo0 10.53.$i.$ns alias \
 					netmask 255.255.255.0
 				[ "$ipv6" ] && ifconfig lo0 inet6 \
diff --git a/lib/isc/include/isc/endian.h b/lib/isc/include/isc/endian.h
index 35ea578b33..54421d55d4 100644
--- a/lib/isc/include/isc/endian.h
+++ b/lib/isc/include/isc/endian.h
@@ -11,51 +11,33 @@
 
 #pragma once
 
-#if defined(__linux__) || defined(__CYGWIN__)
-
-#include <endian.h>
-
-#elif defined __APPLE__
-
-#include <libkern/OSByteOrder.h>
-
-# define htobe16(x) OSSwapHostToBigInt16(x)
-# define htole16(x) OSSwapHostToLittleInt16(x)
-# define be16toh(x) OSSwapBigToHostInt16(x)
-# define le16toh(x) OSSwapLittleToHostInt16(x)
-
-# define htobe32(x) OSSwapHostToBigInt32(x)
-# define htole32(x) OSSwapHostToLittleInt32(x)
-# define be32toh(x) OSSwapBigToHostInt32(x)
-# define le32toh(x) OSSwapLittleToHostInt32(x)
-
-# define htobe64(x) OSSwapHostToBigInt64(x)
-# define htole64(x) OSSwapHostToLittleInt64(x)
-# define be64toh(x) OSSwapBigToHostInt64(x)
-# define le64toh(x) OSSwapLittleToHostInt64(x)
-
-# define __BYTE_ORDER    BYTE_ORDER
-# define __BIG_ENDIAN    BIG_ENDIAN
-# define __LITTLE_ENDIAN LITTLE_ENDIAN
-# define __PDP_ENDIAN    PDP_ENDIAN
-
-#elif defined(__NetBSD__) || defined(__FreeBSD__) || defined(__DragonFly__)
+#if defined(__DragonFly__) || defined(__FreeBSD__) || \
+    defined(__NetBSD__) || defined (__OpenBSD__) || defined(__bsdi__)
 
 # include <sys/endian.h>
 
-# define be16toh(x) betoh16(x)
-# define le16toh(x) letoh16(x)
-
-# define be32toh(x) betoh32(x)
-# define le32toh(x) letoh32(x)
-
-# define be64toh(x) betoh64(x)
-# define le64toh(x) letoh64(x)
+/*
+ * Recent BSDs should have [bl]e{16,32,64}toh() defined in <sys/endian.h>.
+ * Older ones might not, but these should have the alternatively named
+ * [bl]etoh{16,32,64}() functions defined.
+ */
+# ifndef be16toh
+#  define be16toh(x) betoh16(x)
+#  define le16toh(x) letoh16(x)
+#  define be32toh(x) betoh32(x)
+#  define le32toh(x) letoh32(x)
+#  define be64toh(x) betoh64(x)
+#  define le64toh(x) letoh64(x)
+# endif /* !be16toh */
 
 #elif defined(_WIN32)
-/* Windows is always little endian */
 
-#include <stdlib.h>
+/*
+ * Windows is always little-endian and has its own byte-swapping routines, so
+ * use these.
+ */
+
+# include <stdlib.h>
 
 # define htobe16(x) _byteswap_ushort(x)
 # define htole16(x) (x)
@@ -72,13 +54,134 @@
 # define be64toh(x) _byteswap_uint64(x)
 # define le64toh(x) (x)
 
-# define __BYTE_ORDER    BYTE_ORDER
-# define __BIG_ENDIAN    BIG_ENDIAN
-# define __LITTLE_ENDIAN LITTLE_ENDIAN
-# define __PDP_ENDIAN    PDP_ENDIAN
+#elif defined __APPLE__
+
+/*
+ * macOS has its own byte-swapping routines, so use these.
+ */
+
+# include <libkern/OSByteOrder.h>
+
+# define htobe16(x) OSSwapHostToBigInt16(x)
+# define htole16(x) OSSwapHostToLittleInt16(x)
+# define be16toh(x) OSSwapBigToHostInt16(x)
+# define le16toh(x) OSSwapLittleToHostInt16(x)
+
+# define htobe32(x) OSSwapHostToBigInt32(x)
+# define htole32(x) OSSwapHostToLittleInt32(x)
+# define be32toh(x) OSSwapBigToHostInt32(x)
+# define le32toh(x) OSSwapLittleToHostInt32(x)
+
+# define htobe64(x) OSSwapHostToBigInt64(x)
+# define htole64(x) OSSwapHostToLittleInt64(x)
+# define be64toh(x) OSSwapBigToHostInt64(x)
+# define le64toh(x) OSSwapLittleToHostInt64(x)
+
+#elif defined(sun) || defined(__sun) || defined(__SVR4)
+
+/*
+ * For Solaris, rely on the fallback definitions below, though use
+ * Solaris-specific versions of bswap_{16,32,64}().
+ */
+
+# include <sys/byteorder.h>
+
+# define bswap_16(x) BSWAP_16(x)
+# define bswap_32(x) BSWAP_32(x)
+# define bswap_64(x) BSWAP_64(x)
+
+#elif defined(__ANDROID__) || defined(__CYGWIN__) || \
+      defined(__GNUC__) || defined(__GNU__)
+
+# include <byteswap.h>
+# include <endian.h>
 
 #else
 
-#error Platform not supported
+#endif /* Specific platform support */
 
-#endif
+/*
+ * Fallback definitions.
+ */
+
+#include <inttypes.h>
+
+#ifndef bswap_16
+# define bswap_16(x) \
+	((uint16_t)((((uint16_t) (x) & 0xff00) >> 8) |			\
+		    (((uint16_t) (x) & 0x00ff) << 8)))
+#endif /* !bswap_16 */
+
+#ifndef bswap_32
+# define bswap_32(x) \
+	((uint32_t)((((uint32_t) (x) & 0xff000000) >> 24) |		\
+		    (((uint32_t) (x) & 0x00ff0000) >> 8)  |		\
+		    (((uint32_t) (x) & 0x0000ff00) << 8)  |		\
+		    (((uint32_t) (x) & 0x000000ff) << 24)))
+#endif /* !bswap_32 */
+
+#ifndef bswap_64
+# define bswap_64(x) \
+	((uint64_t)((((uint64_t) (x) & 0xff00000000000000ULL) >> 56) |	\
+		    (((uint64_t) (x) & 0x00ff000000000000ULL) >> 40) |	\
+		    (((uint64_t) (x) & 0x0000ff0000000000ULL) >> 24) |	\
+		    (((uint64_t) (x) & 0x000000ff00000000ULL) >> 8)  |	\
+		    (((uint64_t) (x) & 0x00000000ff000000ULL) << 8)  |	\
+		    (((uint64_t) (x) & 0x0000000000ff0000ULL) << 24) |	\
+		    (((uint64_t) (x) & 0x000000000000ff00ULL) << 40) |	\
+		    (((uint64_t) (x) & 0x00000000000000ffULL) << 56)))
+#endif /* !bswap_64 */
+
+#ifndef htobe16
+# if WORDS_BIGENDIAN
+
+#  define htobe16(x) (x)
+#  define htole16(x) bswap_16(x)
+#  define be16toh(x) (x)
+#  define le16toh(x) bswap_16(x)
+
+# else /* WORDS_BIGENDIAN */
+
+#  define htobe16(x) bswap_16(x)
+#  define htole16(x) (x)
+#  define be16toh(x) bswap_16(x)
+#  define le16toh(x) (x)
+
+# endif /* WORDS_BIGENDIAN */
+#endif /* !htobe16 */
+
+#ifndef htobe32
+# if WORDS_BIGENDIAN
+
+#  define htobe32(x) (x)
+#  define htole32(x) bswap_32(x)
+#  define be32toh(x) (x)
+#  define le32toh(x) bswap_32(x)
+
+# else /* WORDS_BIGENDIAN */
+
+#  define htobe32(x) bswap_32(x)
+#  define htole32(x) (x)
+#  define be32toh(x) bswap_32(x)
+#  define le32toh(x) (x)
+
+# endif /* WORDS_BIGENDIAN */
+#endif /* !htobe32 */
+
+#ifndef htobe64
+# if WORDS_BIGENDIAN
+
+#  define htobe64(x) (x)
+#  define htole64(x) bswap_64(x)
+#  define be64toh(x) (x)
+#  define le64toh(x) bswap_64(x)
+
+#else /* WORDS_BIGENDIAN */
+
+#  define htobe64(x) bswap_64(x)
+#  define htole64(x) (x)
+#  define be64toh(x) bswap_64(x)
+#  define le64toh(x) (x)
+
+# endif /* WORDS_BIGENDIAN */
+#endif /* !htobe64 */