Use BIO_TYPE_* constants for flags

Also remove some of the comments that, with the constants, don't provide
any real value.

Change-Id: Ie73d840ac5613a6750796e21a9ab1d644edfe5b1
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/66448
Reviewed-by: Bob Beck <bbe@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Commit-Queue: Bob Beck <bbe@google.com>

include/openssl/bio.h

diff --git a/include/openssl/bio.h b/include/openssl/bio.h
index 4700799..33b020b 100644
--- a/include/openssl/bio.h
+++ b/include/openssl/bio.h
@@ -824,37 +824,37 @@
 // or change the data in any way.
 #define BIO_FLAGS_MEM_RDONLY 0x200
 
-// These are the 'types' of BIOs
-#define BIO_TYPE_NONE 0
-#define BIO_TYPE_MEM (1 | 0x0400)
-#define BIO_TYPE_FILE (2 | 0x0400)
-#define BIO_TYPE_FD (4 | 0x0400 | 0x0100)
-#define BIO_TYPE_SOCKET (5 | 0x0400 | 0x0100)
-#define BIO_TYPE_NULL (6 | 0x0400)
-#define BIO_TYPE_SSL (7 | 0x0200)
-#define BIO_TYPE_MD (8 | 0x0200)                 // passive filter
-#define BIO_TYPE_BUFFER (9 | 0x0200)             // filter
-#define BIO_TYPE_CIPHER (10 | 0x0200)            // filter
-#define BIO_TYPE_BASE64 (11 | 0x0200)            // filter
-#define BIO_TYPE_CONNECT (12 | 0x0400 | 0x0100)  // socket - connect
-#define BIO_TYPE_ACCEPT (13 | 0x0400 | 0x0100)   // socket for accept
-#define BIO_TYPE_PROXY_CLIENT (14 | 0x0200)      // client proxy BIO
-#define BIO_TYPE_PROXY_SERVER (15 | 0x0200)      // server proxy BIO
-#define BIO_TYPE_NBIO_TEST (16 | 0x0200)         // server proxy BIO
-#define BIO_TYPE_NULL_FILTER (17 | 0x0200)
-#define BIO_TYPE_BER (18 | 0x0200)         // BER -> bin filter
-#define BIO_TYPE_BIO (19 | 0x0400)         // (half a) BIO pair
-#define BIO_TYPE_LINEBUFFER (20 | 0x0200)  // filter
-#define BIO_TYPE_DGRAM (21 | 0x0400 | 0x0100)
-#define BIO_TYPE_ASN1 (22 | 0x0200)  // filter
-#define BIO_TYPE_COMP (23 | 0x0200)  // filter
-
 // BIO_TYPE_DESCRIPTOR denotes that the |BIO| responds to the |BIO_C_SET_FD|
 // (|BIO_set_fd|) and |BIO_C_GET_FD| (|BIO_get_fd|) control hooks.
 #define BIO_TYPE_DESCRIPTOR 0x0100  // socket, fd, connect or accept
 #define BIO_TYPE_FILTER 0x0200
 #define BIO_TYPE_SOURCE_SINK 0x0400
 
+// These are the 'types' of BIOs
+#define BIO_TYPE_NONE 0
+#define BIO_TYPE_MEM (1 | BIO_TYPE_SOURCE_SINK)
+#define BIO_TYPE_FILE (2 | BIO_TYPE_SOURCE_SINK)
+#define BIO_TYPE_FD (4 | BIO_TYPE_SOURCE_SINK | BIO_TYPE_DESCRIPTOR)
+#define BIO_TYPE_SOCKET (5 | BIO_TYPE_SOURCE_SINK | BIO_TYPE_DESCRIPTOR)
+#define BIO_TYPE_NULL (6 | BIO_TYPE_SOURCE_SINK)
+#define BIO_TYPE_SSL (7 | BIO_TYPE_FILTER)
+#define BIO_TYPE_MD (8 | BIO_TYPE_FILTER)
+#define BIO_TYPE_BUFFER (9 | BIO_TYPE_FILTER)
+#define BIO_TYPE_CIPHER (10 | BIO_TYPE_FILTER)
+#define BIO_TYPE_BASE64 (11 | BIO_TYPE_FILTER)
+#define BIO_TYPE_CONNECT (12 | BIO_TYPE_SOURCE_SINK | BIO_TYPE_DESCRIPTOR)
+#define BIO_TYPE_ACCEPT (13 | BIO_TYPE_SOURCE_SINK | BIO_TYPE_DESCRIPTOR)
+#define BIO_TYPE_PROXY_CLIENT (14 | BIO_TYPE_FILTER)
+#define BIO_TYPE_PROXY_SERVER (15 | BIO_TYPE_FILTER)
+#define BIO_TYPE_NBIO_TEST (16 | BIO_TYPE_FILTER)
+#define BIO_TYPE_NULL_FILTER (17 | BIO_TYPE_FILTER)
+#define BIO_TYPE_BER (18 | BIO_TYPE_FILTER)       // BER -> bin filter
+#define BIO_TYPE_BIO (19 | BIO_TYPE_SOURCE_SINK)  // (half a) BIO pair
+#define BIO_TYPE_LINEBUFFER (20 | BIO_TYPE_FILTER)
+#define BIO_TYPE_DGRAM (21 | BIO_TYPE_SOURCE_SINK | BIO_TYPE_DESCRIPTOR)
+#define BIO_TYPE_ASN1 (22 | BIO_TYPE_FILTER)
+#define BIO_TYPE_COMP (23 | BIO_TYPE_FILTER)
+
 // BIO_TYPE_START is the first user-allocated |BIO| type. No pre-defined type,
 // flag bits aside, may exceed this value.
 #define BIO_TYPE_START 128