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
/*
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