[PATCH] Don't imply TCP and UDP socket options are bitmasks

[John Baldwin]

The constants used for TCP and UDP socket options (TCP_NODELAY, etc.) are 
currently defined as hex values that are individual bits.  However, socket 
options are never masked together, they are used as a simple enumeration of 
discrete values.  Using a bitmask forces us to run out of bits and makes it 
harder for vendors to try to use a high range of values for local custom 
options (hoping that they never conflict with a new option value added in 
stock FreeBSD).

The socket options in <sys/socket.h> do use bitmasks for the low bits because 
they map directly to bits so_options, but then they start a simple enumeration 
at 0x1000.  TCP and UDP socket options do not directly map to bits in a flags 
field in the PCB (e.g. TF_NODELAY != TCP_NODELAY).  I would like to change the 
representation of the constants to be decimal instead of hex and encourage new 
options to fill in the gaps between the existing values.  This would preserve 
the existing ABI but keep things more sane in the future (I believe).  The 
diff is this:

Index: netinet/tcp.h
===================================================================
--- netinet/tcp.h	(revision 245225)
+++ netinet/tcp.h	(working copy)
@@ -151,18 +151,18 @@
 /*
  * User-settable options (used with setsockopt).
  */
-#define	TCP_NODELAY	0x01	/* don't delay send to coalesce packets */
+#define	TCP_NODELAY	1	/* don't delay send to coalesce packets */
 #if __BSD_VISIBLE
-#define	TCP_MAXSEG	0x02	/* set maximum segment size */
-#define TCP_NOPUSH	0x04	/* don't push last block of write */
-#define TCP_NOOPT	0x08	/* don't use TCP options */
-#define TCP_MD5SIG	0x10	/* use MD5 digests (RFC2385) */
-#define	TCP_INFO	0x20	/* retrieve tcp_info structure */
-#define	TCP_CONGESTION	0x40	/* get/set congestion control algorithm */
-#define	TCP_KEEPINIT	0x80	/* N, time to establish connection */
-#define	TCP_KEEPIDLE	0x100	/* L,N,X start keeplives after this period */
-#define	TCP_KEEPINTVL	0x200	/* L,N interval between keepalives */
-#define	TCP_KEEPCNT	0x400	/* L,N number of keepalives before close */
+#define	TCP_MAXSEG	2	/* set maximum segment size */
+#define TCP_NOPUSH	4	/* don't push last block of write */
+#define TCP_NOOPT	8	/* don't use TCP options */
+#define TCP_MD5SIG	16	/* use MD5 digests (RFC2385) */
+#define	TCP_INFO	32	/* retrieve tcp_info structure */
+#define	TCP_CONGESTION	64	/* get/set congestion control algorithm */
+#define	TCP_KEEPINIT	128	/* N, time to establish connection */
+#define	TCP_KEEPIDLE	256	/* L,N,X start keeplives after this period */
+#define	TCP_KEEPINTVL	512	/* L,N interval between keepalives */
+#define	TCP_KEEPCNT	1024	/* L,N number of keepalives before close */
 
 #define	TCP_CA_NAME_MAX	16	/* max congestion control name length */
 
Index: netinet/udp.h
===================================================================
--- netinet/udp.h	(revision 245225)
+++ netinet/udp.h	(working copy)
@@ -48,7 +48,7 @@
 /* 
  * User-settable options (used with setsockopt).
  */
-#define	UDP_ENCAP			0x01
+#define	UDP_ENCAP			1
 
 
 /*

-- 
John Baldwin