jw schultz writes:
> 1. Yes, you may contribute a patch. I favor the idea of
> being able to supply a checksum seed.
>
> 2. Lets get the option name down to a more reasonable
> length. --checksum-seed should be sufficient.
I submitted a patch against 2.5.6pre1 last January for --checksum-seed=NUM:
http://lists.samba.org/archive/rsync/2003-January/004845.html
but in that thread Dave Dykstra correctly pointed out there wasn't
much point in letting the user specify a particular value.
Therefore, I switched to just a flag that forces the fixed value of
32761 (same as batch mode). I picked the option named --fixed-csumseed,
which is long but hopefully informative.
Here's a patch against CVS using --fixed-csumseed. I also added it to
the usage and documentation, but it's not clear this option needs to be
exposed to the user.
Craig
diff -bur rsync/options.c rsync-fixedcsum/options.c
--- rsync/options.c Tue Feb 10 20:30:41 2004
+++ rsync-fixedcsum/options.c Mon Feb 16 12:32:23 2004
@@ -89,6 +89,7 @@
int modify_window = 0;
int blocking_io = -1;
int checksum_seed = 0;
+int fixed_csumseed = 0;
unsigned int block_size = 0;
@@ -288,6 +289,7 @@
rprintf(F," --bwlimit=KBPS limit I/O bandwidth, KBytes per second\n");
rprintf(F," --write-batch=PREFIX write batch fileset starting with
PREFIX\n");
rprintf(F," --read-batch=PREFIX read batch fileset starting with PREFIX\n");
+ rprintf(F," --fixed-csumseed use fixed MD4 block/file checksum seed\n");
rprintf(F," -h, --help show this help screen\n");
#ifdef INET6
rprintf(F," -4 prefer IPv4\n");
@@ -303,7 +305,7 @@
enum {OPT_VERSION = 1000, OPT_SENDER, OPT_EXCLUDE, OPT_EXCLUDE_FROM,
OPT_DELETE_AFTER, OPT_DELETE_EXCLUDED, OPT_LINK_DEST,
OPT_INCLUDE, OPT_INCLUDE_FROM, OPT_MODIFY_WINDOW,
- OPT_READ_BATCH, OPT_WRITE_BATCH};
+ OPT_READ_BATCH, OPT_WRITE_BATCH, OPT_FIXED_CSUMSEED};
static struct poptOption long_options[] = {
/* longName, shortName, argInfo, argPtr, value, descrip, argDesc */
@@ -379,6 +381,7 @@
{"hard-links", 'H', POPT_ARG_NONE, &preserve_hard_links, 0, 0, 0 },
{"read-batch", 0, POPT_ARG_STRING, &batch_prefix, OPT_READ_BATCH, 0, 0 },
{"write-batch", 0, POPT_ARG_STRING, &batch_prefix, OPT_WRITE_BATCH, 0, 0 },
+ {"fixed-csumseed", 0, POPT_ARG_NONE, 0, OPT_FIXED_CSUMSEED, 0, 0 },
{"files-from", 0, POPT_ARG_STRING, &files_from, 0, 0, 0 },
{"from0", '0', POPT_ARG_NONE, &eol_nulls, 0, 0, 0},
{"no-implied-dirs", 0, POPT_ARG_VAL, &implied_dirs, 0, 0, 0 },
@@ -564,6 +567,11 @@
checksum_seed = FIXED_CHECKSUM_SEED;
break;
+ case OPT_FIXED_CSUMSEED:
+ fixed_csumseed = 1;
+ checksum_seed = FIXED_CHECKSUM_SEED;
+ break;
+
case OPT_LINK_DEST:
#if HAVE_LINK
compare_dest = (char *)poptGetOptArg(pc);
@@ -931,6 +939,10 @@
args[ac++] = "--files-from=-";
args[ac++] = "--from0";
}
+ }
+
+ if (fixed_csumseed) {
+ args[ac++] = "--fixed-csumseed";
}
*argc = ac;
diff -bur rsync/rsync.yo rsync-fixedcsum/rsync.yo
--- rsync/rsync.yo Mon Feb 2 10:23:09 2004
+++ rsync-fixedcsum/rsync.yo Mon Feb 16 12:36:08 2004
@@ -348,6 +348,7 @@
--bwlimit=KBPS limit I/O bandwidth, KBytes per second
--write-batch=PREFIX write batch fileset starting with PREFIX
--read-batch=PREFIX read batch fileset starting with PREFIX
+ --fixed-csumseed use fixed MD4 block/file checksum seed
-h, --help show this help screen
@@ -879,6 +880,15 @@
dit(bf(--read-batch=PREFIX)) Apply a previously generated change batch,
using the fileset whose filenames start with PREFIX. See the "BATCH
MODE" section for details.
+
+dit(bf(--fixed-csumseed)) Set the MD4 checksum seed to the fixed
+value 32761. This 4 byte checksum seed is included in each block and
+file MD4 checksum calculation. By default the checksum seed is generated
+by the server and defaults to the current time(), or 32761 if
+bf(--write-batch) or bf(--read-batch) are specified. This default
+causes the MD4 block and file checksums to be different each time rsync
+is run. For applications that cache the block or file checksums the
+checksum seed needs to be fixed each time rsync runs using this option.
enddit()
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