Minor cleanup

os/frisbee.redux/decls.h

@@ -12,22 +12,28 @@
 #include "log.h"
 
 /*
- * We operate in terms of this blocksize (in bytes). 
+ * Ethernet MTU (1514) - eth header (14) - min UDP/IP (28) - BLOCK msg
+ * header (24).
  */
-#define BLOCKSIZE	1024
+#define MAXBLOCKSIZE	1448
 
 /*
- * Each chunk is this many blocks.
+ * Images are broken into chunks which are the standalone unit of decompression
+ * Chunks are broken into blocks which are the unit of transmission
  */
 #define CHUNKSIZE	1024
+#define BLOCKSIZE	1024
 
 /*
- * See if we can represent a bitmap of blocks in a single packet.
- * If so, then allow partial request messages.
+ * Make sure we can represent a bitmap of blocks in a single packet.
+ * Make sure we can fit a block in a single ethernet MTU.
  */
-#if (CHUNKSIZE%CHAR_BIT) != 0 || (CHUNKSIZE/CHAR_BIT) > 1450
+#if (CHUNKSIZE%CHAR_BIT) != 0 || (CHUNKSIZE/CHAR_BIT) > MAXBLOCKSIZE
 #error "Invalid chunk size"
 #endif
+#if BLOCKSIZE > MAXBLOCKSIZE
+#error "Invalid block size"
+#endif
 
 /*
  * Chunk buffers and output write buffers constitute most of the memory

os/frisbee.redux/server.c

@@ -1079,8 +1079,8 @@ calcburst(void)
 	bursts = 0;
 }
 
-#define LINK_OVERHEAD	(14 + 20)	/* ethernet (hdr + preamble + gap) */
-#define IP_OVERHEAD	(20 + 8)	/* UDP + IP hdrs */
+#define LINK_OVERHEAD	(14+4+8+12)	/* ethernet (hdr+CRC+preamble+gap) */
+#define IP_OVERHEAD	(20+8)		/* IP + UDP hdrs */
 
 /*
  * Compute the approximate send rate.  Due to typically coarse grained