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

[Alfred Perlstein]

Wouldn't a comment over the code suffice?

Something like your email as a header would actually work very nicely!

I think just using decimal would be more confusing than explicitly 
calling it out like:

/* begin enumerated (not bitmask) socket option specifiers */
#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) */
/* end enumerated socket option specifiers */


On 1/14/13 3:50 PM, John Baldwin wrote:
> 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
>   
>   
>   /*
>