Updating patches.
[rsync-patches.git] / checksum-updating.diff
1 This builds on the checksum-reading patch and adds the ability to
2 create and/or update the .rsyncsums files using extended mode args to
3 the --sumfiles=MODE option and the "checksum files = MODE" daemon
4 parameter.
5
6 CAUTION:  This patch is only lightly tested.  If you're interested
7 in using it, please help out.
8
9 To use this patch, run these commands for a successful build:
10
11     patch -p1 <patches/checksum-reading.diff
12     patch -p1 <patches/checksum-updating.diff
13     ./configure                               (optional if already run)
14     make
15
16 TODO:
17
18  - Fix the code that removes .rsyncsums files when a dir becomes empty.
19
20 based-on: patch/master/checksum-reading
21 diff --git a/flist.c b/flist.c
22 --- a/flist.c
23 +++ b/flist.c
24 @@ -27,6 +27,7 @@
25  #include "inums.h"
26  #include "io.h"
27  
28 +extern int dry_run;
29  extern int am_root;
30  extern int am_server;
31  extern int am_daemon;
32 @@ -106,6 +107,9 @@ extern iconv_t ic_send, ic_recv;
33  
34  #define PTR_SIZE (sizeof (struct file_struct *))
35  
36 +#define FLAG_SUM_MISSING (1<<1) /* F_SUM() data is undefined */
37 +#define FLAG_SUM_KEEP (1<<2) /* keep entry when rewriting */
38 +
39  int io_error;
40  int checksum_len;
41  dev_t filesystem_dev; /* used to implement -x */
42 @@ -146,8 +150,13 @@ static char tmp_sum[MAX_DIGEST_LEN];
43  static char empty_sum[MAX_DIGEST_LEN];
44  static int flist_count_offset; /* for --delete --progress */
45  
46 +#define REGULAR_SKIPPED(flist) ((flist)->to_redo)
47 +
48  static struct csum_cache {
49         struct file_list *flist;
50 +       const char *dirname;
51 +       int checksum_matches;
52 +       int checksum_updates;
53  } *csum_cache = NULL;
54  
55  static void flist_sort_and_clean(struct file_list *flist, int flags);
56 @@ -365,7 +374,79 @@ static void flist_done_allocating(struct file_list *flist)
57                 flist->pool_boundary = ptr;
58  }
59  
60 -void reset_checksum_cache()
61 +static void checksum_filename(int slot, const char *dirname, char *fbuf)
62 +{
63 +       if (dirname && *dirname) {
64 +               unsigned int len;
65 +               if (slot) {
66 +                       len = strlcpy(fbuf, basis_dir[slot-1], MAXPATHLEN);
67 +                       if (len >= MAXPATHLEN)
68 +                               return;
69 +               } else
70 +                       len = 0;
71 +               if (pathjoin(fbuf+len, MAXPATHLEN-len, dirname, RSYNCSUMS_FILE) >= MAXPATHLEN-len)
72 +                       return;
73 +       } else
74 +               strlcpy(fbuf, RSYNCSUMS_FILE, MAXPATHLEN);
75 +}
76 +
77 +static void write_checksums(int slot, struct file_list *flist, int whole_dir)
78 +{
79 +       int i;
80 +       FILE *out_fp;
81 +       char fbuf[MAXPATHLEN];
82 +       int new_entries = csum_cache[slot].checksum_updates != 0;
83 +       int counts_match = flist->used == csum_cache[slot].checksum_matches;
84 +       int no_skipped = whole_dir && REGULAR_SKIPPED(flist) == 0;
85 +       const char *dirname = csum_cache[slot].dirname;
86 +
87 +       flist_sort_and_clean(flist, 0);
88 +
89 +       if (dry_run && !(checksum_files & CSF_AFFECT_DRYRUN))
90 +               return;
91 +
92 +       checksum_filename(slot, dirname, fbuf);
93 +
94 +       if (flist->high - flist->low < 0 && no_skipped) {
95 +               unlink(fbuf);
96 +               return;
97 +       }
98 +
99 +       if (!new_entries && (counts_match || !whole_dir))
100 +               return;
101 +
102 +       if (!(out_fp = fopen(fbuf, "w")))
103 +               return;
104 +
105 +       for (i = flist->low; i <= flist->high; i++) {
106 +               struct file_struct *file = flist->sorted[i];
107 +               const char *cp = F_SUM(file);
108 +               const char *end = cp + checksum_len;
109 +               const char *alt_sum = file->basename + strlen(file->basename) + 1;
110 +               if (whole_dir && !(file->flags & FLAG_SUM_KEEP))
111 +                       continue;
112 +               if (protocol_version >= 30)
113 +                       fprintf(out_fp, "%s ", alt_sum);
114 +               if (file->flags & FLAG_SUM_MISSING) {
115 +                       do {
116 +                               fputs("==", out_fp);
117 +                       } while (++cp != end);
118 +               } else {
119 +                       do {
120 +                               fprintf(out_fp, "%02x", (int)CVAL(cp, 0));
121 +                       } while (++cp != end);
122 +               }
123 +               if (protocol_version < 30)
124 +                       fprintf(out_fp, " %s", alt_sum);
125 +               fprintf(out_fp, " %10.0f %10.0f %10lu %10lu %s\n",
126 +                       (double)F_LENGTH(file), (double)file->modtime,
127 +                       (long)F_CTIME(file), (long)F_INODE(file), file->basename);
128 +       }
129 +
130 +       fclose(out_fp);
131 +}
132 +
133 +void reset_checksum_cache(int whole_dir)
134  {
135         int slot, slots = am_sender ? 1 : basis_dir_cnt + 1;
136  
137 @@ -379,6 +460,9 @@ void reset_checksum_cache()
138                 struct file_list *flist = csum_cache[slot].flist;
139  
140                 if (flist) {
141 +                       if (checksum_files & CSF_UPDATE && flist->next)
142 +                               write_checksums(slot, flist, whole_dir);
143 +
144                         /* Reset the pool memory and empty the file-list array. */
145                         pool_free_old(flist->file_pool,
146                                       pool_boundary(flist->file_pool, 0));
147 @@ -389,6 +473,10 @@ void reset_checksum_cache()
148                 flist->low = 0;
149                 flist->high = -1;
150                 flist->next = NULL;
151 +
152 +               csum_cache[slot].checksum_matches = 0;
153 +               csum_cache[slot].checksum_updates = 0;
154 +               REGULAR_SKIPPED(flist) = 0;
155         }
156  }
157  
158 @@ -396,7 +484,7 @@ void reset_checksum_cache()
159  static int add_checksum(struct file_list *flist, const char *dirname,
160                         const char *basename, int basename_len, OFF_T file_length,
161                         time_t mtime, uint32 ctime, uint32 inode,
162 -                       const char *sum)
163 +                       const char *sum, const char *alt_sum, int flags)
164  {
165         struct file_struct *file;
166         int alloc_len, extra_len;
167 @@ -413,7 +501,7 @@ static int add_checksum(struct file_list *flist, const char *dirname,
168         if (extra_len & (EXTRA_ROUNDING * EXTRA_LEN))
169                 extra_len = (extra_len | (EXTRA_ROUNDING * EXTRA_LEN)) + EXTRA_LEN;
170  #endif
171 -       alloc_len = FILE_STRUCT_LEN + extra_len + basename_len;
172 +       alloc_len = FILE_STRUCT_LEN + extra_len + basename_len + checksum_len*2 + 1;
173         bp = pool_alloc(flist->file_pool, alloc_len, "add_checksum");
174  
175         memset(bp, 0, extra_len + FILE_STRUCT_LEN);
176 @@ -422,7 +510,14 @@ static int add_checksum(struct file_list *flist, const char *dirname,
177         bp += FILE_STRUCT_LEN;
178  
179         memcpy(bp, basename, basename_len);
180 +       if (alt_sum)
181 +               strlcpy(bp+basename_len, alt_sum, checksum_len*2 + 1);
182 +       else {
183 +               memset(bp+basename_len, '=', checksum_len*2);
184 +               bp[basename_len+checksum_len*2] = '\0';
185 +       }
186  
187 +       file->flags = flags;
188         file->mode = S_IFREG;
189         file->modtime = mtime;
190         file->len32 = (uint32)file_length;
191 @@ -451,10 +546,11 @@ static void read_checksums(int slot, struct file_list *flist, const char *dirnam
192         char line[MAXPATHLEN+1024], fbuf[MAXPATHLEN], sum[MAX_DIGEST_LEN];
193         FILE *fp;
194         char *cp;
195 -       int len, i;
196         time_t mtime;
197 +       int len, i, flags;
198         OFF_T file_length;
199         uint32 ctime, inode;
200 +       const char *alt_sum = NULL;
201         int dlen = dirname ? strlcpy(fbuf, dirname, sizeof fbuf) : 0;
202  
203         if (dlen >= (int)(sizeof fbuf - 1 - RSYNCSUMS_LEN))
204 @@ -475,7 +571,7 @@ static void read_checksums(int slot, struct file_list *flist, const char *dirnam
205         while (fgets(line, sizeof line, fp)) {
206                 cp = line;
207                 if (protocol_version >= 30) {
208 -                       char *alt_sum = cp;
209 +                       alt_sum = cp;
210                         if (*cp == '=')
211                                 while (*++cp == '=') {}
212                         else
213 @@ -486,7 +582,14 @@ static void read_checksums(int slot, struct file_list *flist, const char *dirnam
214                 }
215  
216                 if (*cp == '=') {
217 -                       continue;
218 +                       for (i = 0; i < checksum_len*2; i++, cp++) {
219 +                               if (*cp != '=') {
220 +                                       cp = "";
221 +                                       break;
222 +                               }
223 +                       }
224 +                       memset(sum, 0, checksum_len);
225 +                       flags = FLAG_SUM_MISSING;
226                 } else {
227                         for (i = 0; i < checksum_len*2; i++, cp++) {
228                                 int x;
229 @@ -504,13 +607,14 @@ static void read_checksums(int slot, struct file_list *flist, const char *dirnam
230                                 else
231                                         sum[i/2] = x << 4;
232                         }
233 +                       flags = 0;
234                 }
235                 if (*cp != ' ')
236                         break;
237                 while (*++cp == ' ') {}
238  
239                 if (protocol_version < 30) {
240 -                       char *alt_sum = cp;
241 +                       alt_sum = cp;
242                         if (*cp == '=')
243                                 while (*++cp == '=') {}
244                         else
245 @@ -560,24 +664,112 @@ static void read_checksums(int slot, struct file_list *flist, const char *dirnam
246                         continue;
247  
248                 strlcpy(fbuf+dlen, cp, sizeof fbuf - dlen);
249 +               if (is_excluded(fbuf, 0, ALL_FILTERS)) {
250 +                       flags |= FLAG_SUM_KEEP;
251 +                       csum_cache[slot].checksum_matches++;
252 +               }
253  
254                 add_checksum(flist, dirname, cp, len, file_length,
255                              mtime, ctime, inode,
256 -                            sum);
257 +                            sum, alt_sum, flags);
258         }
259         fclose(fp);
260  
261         flist_sort_and_clean(flist, CLEAN_KEEP_LAST);
262  }
263  
264 +void set_cached_checksum(struct file_list *file_flist, struct file_struct *file)
265 +{
266 +       int j;
267 +       FILE *out_fp;
268 +       STRUCT_STAT st;
269 +       char fbuf[MAXPATHLEN];
270 +       const char *fn = f_name(file, NULL);
271 +       struct file_list *flist = csum_cache[0].flist;
272 +
273 +       if (dry_run && !(checksum_files & CSF_AFFECT_DRYRUN))
274 +               return;
275 +
276 +       if (stat(fn, &st) < 0)
277 +               return;
278 +
279 +       checksum_filename(0, file->dirname, fbuf);
280 +
281 +       if (file_flist != flist->next) {
282 +               const char *cp = F_SUM(file);
283 +               const char *end = cp + checksum_len;
284 +
285 +               if (!(out_fp = fopen(fbuf, "a")))
286 +                       return;
287 +
288 +               if (protocol_version >= 30) {
289 +                       for (j = 0; j < checksum_len; j++)
290 +                               fputs("==", out_fp);
291 +                       fputc(' ', out_fp);
292 +               }
293 +               do {
294 +                       fprintf(out_fp, "%02x", (int)CVAL(cp, 0));
295 +               } while (++cp != end);
296 +               if (protocol_version < 30) {
297 +                       fputc(' ', out_fp);
298 +                       for (j = 0; j < checksum_len; j++)
299 +                               fputs("==", out_fp);
300 +               }
301 +               fprintf(out_fp, " %10.0f %10.0f %10lu %10lu %s\n",
302 +                       (double)st.st_size, (double)st.st_mtime,
303 +                       (long)(uint32)st.st_ctime, (long)(uint32)st.st_ino,
304 +                       file->basename);
305 +
306 +               fclose(out_fp);
307 +               return;
308 +       }
309 +
310 +       if ((j = flist_find(flist, file)) >= 0) {
311 +               struct file_struct *fp = flist->sorted[j];
312 +               int inc = 0;
313 +               if (F_LENGTH(fp) != st.st_size) {
314 +                       fp->len32 = (uint32)st.st_size;
315 +                       if (st.st_size > 0xFFFFFFFFu) {
316 +                               OPT_EXTRA(fp, 0)->unum = (uint32)(st.st_size >> 32);
317 +                               fp->flags |= FLAG_LENGTH64;
318 +                       } else
319 +                               fp->flags &= FLAG_LENGTH64;
320 +                       inc = 1;
321 +               }
322 +               if (fp->modtime != st.st_mtime) {
323 +                       fp->modtime = st.st_mtime;
324 +                       inc = 1;
325 +               }
326 +               if (F_CTIME(fp) != (uint32)st.st_ctime) {
327 +                       F_CTIME(fp) = (uint32)st.st_ctime;
328 +                       inc = 1;
329 +               }
330 +               if (F_INODE(fp) != (uint32)st.st_ino) {
331 +                       F_INODE(fp) = (uint32)st.st_ino;
332 +                       inc = 1;
333 +               }
334 +               memcpy(F_SUM(fp), F_SUM(file), MAX_DIGEST_LEN);
335 +               csum_cache[0].checksum_updates += inc;
336 +               fp->flags &= ~FLAG_SUM_MISSING;
337 +               fp->flags |= FLAG_SUM_KEEP;
338 +               return;
339 +       }
340 +
341 +       csum_cache[0].checksum_updates +=
342 +           add_checksum(flist, file->dirname, file->basename, strlen(file->basename) + 1,
343 +                        st.st_size, (uint32)st.st_mtime, (uint32)st.st_ctime,
344 +                        st.st_ino, F_SUM(file), NULL, FLAG_SUM_KEEP);
345 +}
346 +
347  void get_cached_checksum(int slot, const char *fname, struct file_struct *file,
348 -                        STRUCT_STAT *stp, char *sum_buf)
349 +                        int basename_len, STRUCT_STAT *stp, char *sum_buf)
350  {
351         struct file_list *flist = csum_cache[slot].flist;
352         int j;
353  
354         if (!flist->next) {
355                 flist->next = cur_flist; /* next points from checksum flist to file flist */
356 +               csum_cache[slot].dirname = file->dirname;
357                 read_checksums(slot, flist, file->dirname);
358         }
359  
360 @@ -589,12 +781,31 @@ void get_cached_checksum(int slot, const char *fname, struct file_struct *file,
361                  && (checksum_files & CSF_LAX
362                   || (F_CTIME(fp) == (uint32)stp->st_ctime
363                    && F_INODE(fp) == (uint32)stp->st_ino))) {
364 -                       memcpy(sum_buf, F_SUM(fp), MAX_DIGEST_LEN);
365 +                       if (fp->flags & FLAG_SUM_MISSING) {
366 +                               fp->flags &= ~FLAG_SUM_MISSING;
367 +                               csum_cache[slot].checksum_updates++;
368 +                               file_checksum(fname, stp, sum_buf);
369 +                               memcpy(F_SUM(fp), sum_buf, MAX_DIGEST_LEN);
370 +                       } else {
371 +                               csum_cache[slot].checksum_matches++;
372 +                               memcpy(sum_buf, F_SUM(fp), MAX_DIGEST_LEN);
373 +                       }
374 +                       fp->flags |= FLAG_SUM_KEEP;
375                         return;
376                 }
377 +               clear_file(fp);
378         }
379  
380         file_checksum(fname, stp, sum_buf);
381 +
382 +       if (checksum_files & CSF_UPDATE) {
383 +               if (basename_len < 0)
384 +                       basename_len = strlen(file->basename) + 1;
385 +               csum_cache[slot].checksum_updates +=
386 +                   add_checksum(flist, file->dirname, file->basename, basename_len,
387 +                                stp->st_size, stp->st_mtime, (uint32)stp->st_ctime,
388 +                                (uint32)stp->st_ino, sum_buf, NULL, FLAG_SUM_KEEP);
389 +       }
390  }
391  
392  /* Call this with EITHER (1) "file, NULL, 0" to chdir() to the file's
393 @@ -1501,6 +1712,8 @@ struct file_struct *make_file(const char *fname, struct file_list *flist,
394         if (is_excluded(thisname, S_ISDIR(st.st_mode) != 0, filter_level)) {
395                 if (ignore_perishable)
396                         non_perishable_cnt++;
397 +               if (S_ISREG(st.st_mode))
398 +                       REGULAR_SKIPPED(flist)++;
399                 return NULL;
400         }
401  
402 @@ -1547,13 +1760,13 @@ struct file_struct *make_file(const char *fname, struct file_list *flist,
403                         lastdir[len] = '\0';
404                         lastdir_len = len;
405                         if (checksum_files && am_sender && flist)
406 -                               reset_checksum_cache();
407 +                               reset_checksum_cache(0);
408                 }
409         } else {
410                 basename = thisname;
411                 if (checksum_files && am_sender && flist && lastdir_len == -2) {
412                         lastdir_len = -1;
413 -                       reset_checksum_cache();
414 +                       reset_checksum_cache(0);
415                 }
416         }
417         basename_len = strlen(basename) + 1; /* count the '\0' */
418 @@ -1661,7 +1874,7 @@ struct file_struct *make_file(const char *fname, struct file_list *flist,
419  
420         if (always_checksum && am_sender && S_ISREG(st.st_mode)) {
421                 if (flist && checksum_files)
422 -                       get_cached_checksum(0, thisname, file, &st, tmp_sum);
423 +                       get_cached_checksum(0, thisname, file, basename_len, &st, tmp_sum);
424                 else
425                         file_checksum(thisname, &st, tmp_sum);
426                 if (sender_keeps_checksum)
427 @@ -2037,6 +2250,9 @@ static void send_directory(int f, struct file_list *flist, char *fbuf, int len,
428  
429         closedir(d);
430  
431 +       if (checksum_files & CSF_UPDATE && am_sender && f >= 0)
432 +               reset_checksum_cache(1);
433 +
434         if (f >= 0 && recurse && !divert_dirs) {
435                 int i, end = flist->used - 1;
436                 /* send_if_directory() bumps flist->used, so use "end". */
437 @@ -2696,6 +2912,9 @@ struct file_list *send_file_list(int f, int argc, char *argv[])
438                         rprintf(FINFO, "[%s] flist_eof=1\n", who_am_i());
439         }
440  
441 +       if (checksum_files & CSF_UPDATE && flist_eof)
442 +               reset_checksum_cache(0); /* writes any last updates */
443 +
444         return flist;
445  }
446  
447 diff --git a/generator.c b/generator.c
448 --- a/generator.c
449 +++ b/generator.c
450 @@ -110,6 +110,7 @@ static int dir_tweaking;
451  static int symlink_timeset_failed_flags;
452  static int need_retouch_dir_times;
453  static int need_retouch_dir_perms;
454 +static int started_whole_dir, upcoming_whole_dir;
455  static const char *solo_file = NULL;
456  
457  enum nonregtype {
458 @@ -580,7 +581,7 @@ int unchanged_file(char *fn, struct file_struct *file, STRUCT_STAT *st, int slot
459         if (always_checksum > 0 && S_ISREG(st->st_mode)) {
460                 char sum[MAX_DIGEST_LEN];
461                 if (checksum_files && slot >= 0)
462 -                       get_cached_checksum(slot, fn, file, st, sum);
463 +                       get_cached_checksum(slot, fn, file, -1, st, sum);
464                 else
465                         file_checksum(fn, st, sum);
466                 return memcmp(sum, F_SUM(file), checksum_len) == 0;
467 @@ -1301,7 +1302,8 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
468                                 }
469                         }
470                         if (checksum_files) {
471 -                               reset_checksum_cache();
472 +                               reset_checksum_cache(started_whole_dir);
473 +                               started_whole_dir = upcoming_whole_dir;
474                         }
475                         need_new_dirscan = 0;
476                 }
477 @@ -1475,6 +1477,7 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
478                         else
479                                 change_local_filter_dir(fname, strlen(fname), F_DEPTH(file));
480                 }
481 +               upcoming_whole_dir = file->flags & FLAG_CONTENT_DIR && f_out != -1 ? 1 : 0;
482                 goto cleanup;
483         }
484  
485 @@ -1754,6 +1757,8 @@ static void recv_generator(char *fname, struct file_struct *file, int ndx,
486                         handle_partial_dir(partialptr, PDIR_DELETE);
487                 }
488                 set_file_attrs(fname, file, &sx, NULL, maybe_ATTRS_REPORT);
489 +               if (checksum_files & CSF_UPDATE)
490 +                       set_cached_checksum(cur_flist, file);
491                 if (itemizing)
492                         itemize(fnamecmp, file, ndx, statret, &sx, 0, 0, NULL);
493  #ifdef SUPPORT_HARD_LINKS
494 @@ -2248,6 +2253,7 @@ void generate_files(int f_out, const char *local_name)
495                                 } else
496                                         change_local_filter_dir(fbuf, strlen(fbuf), F_DEPTH(fp));
497                         }
498 +                       upcoming_whole_dir = fp->flags & FLAG_CONTENT_DIR ? 1 : 0;
499                 }
500                 for (i = cur_flist->low; i <= cur_flist->high; i++) {
501                         struct file_struct *file = cur_flist->sorted[i];
502 @@ -2342,6 +2348,9 @@ void generate_files(int f_out, const char *local_name)
503                         wait_for_receiver();
504         }
505  
506 +       if (checksum_files)
507 +               reset_checksum_cache(started_whole_dir);
508 +
509         info_levels[INFO_FLIST] = save_info_flist;
510         info_levels[INFO_PROGRESS] = save_info_progress;
511  
512 diff --git a/io.c b/io.c
513 --- a/io.c
514 +++ b/io.c
515 @@ -53,6 +53,7 @@ extern int read_batch;
516  extern int compat_flags;
517  extern int protect_args;
518  extern int checksum_seed;
519 +extern int checksum_files;
520  extern int protocol_version;
521  extern int remove_source_files;
522  extern int preserve_hard_links;
523 @@ -1050,6 +1051,9 @@ static void got_flist_entry_status(enum festatus status, int ndx)
524                                 if (inc_recurse)
525                                         flist->in_progress++;
526                         }
527 +               } else if (checksum_files & CSF_UPDATE) {
528 +                       struct file_struct *file = flist->files[ndx - flist->ndx_start];
529 +                       set_cached_checksum(flist, file);
530                 }
531  #endif
532                 break;
533 diff --git a/loadparm.c b/loadparm.c
534 --- a/loadparm.c
535 +++ b/loadparm.c
536 @@ -316,6 +316,10 @@ static struct enum_list enum_csum_modes[] = {
537         { CSF_IGNORE_FILES, "none" },
538         { CSF_LAX_MODE, "lax" },
539         { CSF_STRICT_MODE, "strict" },
540 +       { CSF_LAX_MODE|CSF_UPDATE, "+lax" },
541 +       { CSF_STRICT_MODE|CSF_UPDATE, "+strict" },
542 +       { CSF_LAX_MODE|CSF_UPDATE|CSF_AFFECT_DRYRUN, "++lax" },
543 +       { CSF_STRICT_MODE|CSF_UPDATE|CSF_AFFECT_DRYRUN, "++strict" },
544         { -1, NULL }
545  };
546  
547 diff --git a/options.c b/options.c
548 --- a/options.c
549 +++ b/options.c
550 @@ -1680,7 +1680,15 @@ int parse_arguments(int *argc_p, const char ***argv_p)
551  
552                 case OPT_SUMFILES:
553                         arg = poptGetOptArg(pc);
554 -                       checksum_files = 0;
555 +                       if (*arg == '+') {
556 +                               arg++;
557 +                               checksum_files = CSF_UPDATE;
558 +                               if (*arg == '+') {
559 +                                       arg++;
560 +                                       checksum_files |= CSF_AFFECT_DRYRUN;
561 +                               }
562 +                       } else
563 +                               checksum_files = 0;
564                         if (strcmp(arg, "lax") == 0)
565                                 checksum_files |= CSF_LAX_MODE;
566                         else if (strcmp(arg, "strict") == 0)
567 diff --git a/receiver.c b/receiver.c
568 --- a/receiver.c
569 +++ b/receiver.c
570 @@ -50,6 +50,7 @@ extern int preallocate_files;
571  extern int keep_partial;
572  extern int checksum_len;
573  extern int checksum_seed;
574 +extern int checksum_files;
575  extern int inplace;
576  extern int allowed_lull;
577  extern int delay_updates;
578 @@ -435,7 +436,7 @@ static void handle_delayed_updates(char *local_name)
579                                         "rename failed for %s (from %s)",
580                                         full_fname(fname), partialptr);
581                         } else {
582 -                               if (remove_source_files
583 +                               if (remove_source_files || checksum_files & CSF_UPDATE
584                                  || (preserve_hard_links && F_IS_HLINKED(file)))
585                                         send_msg_int(MSG_SUCCESS, ndx);
586                                 handle_partial_dir(partialptr, PDIR_DELETE);
587 @@ -898,7 +899,7 @@ int recv_files(int f_in, int f_out, char *local_name)
588                 case 2:
589                         break;
590                 case 1:
591 -                       if (remove_source_files || inc_recurse
592 +                       if (remove_source_files || inc_recurse || checksum_files & CSF_UPDATE
593                          || (preserve_hard_links && F_IS_HLINKED(file)))
594                                 send_msg_int(MSG_SUCCESS, ndx);
595                         break;
596 diff --git a/rsync.h b/rsync.h
597 --- a/rsync.h
598 +++ b/rsync.h
599 @@ -976,6 +976,8 @@ typedef struct {
600  
601  #define CSF_ENABLE (1<<1)
602  #define CSF_LAX (1<<2)
603 +#define CSF_UPDATE (1<<3)
604 +#define CSF_AFFECT_DRYRUN (1<<4)
605  
606  #define CSF_IGNORE_FILES 0
607  #define CSF_LAX_MODE (CSF_ENABLE|CSF_LAX)
608 diff --git a/rsync.yo b/rsync.yo
609 --- a/rsync.yo
610 +++ b/rsync.yo
611 @@ -648,9 +648,13 @@ computed just as it would be if bf(--sumfiles) was not specified.
612  
613  The MODE value is either "lax", for relaxed checking (which compares size
614  and mtime), "strict" (which also compares ctime and inode), or "none" to
615 -ignore any .rsyncsums files ("none" is the default).  Rsync does not create
616 -or update these files, but there is a perl script in the support directory
617 -named "rsyncsums" that can be used for that.
618 +ignore any .rsyncsums files ("none" is the default).
619 +If you want rsync to create and/or update these files, specify a prefixed
620 +plus ("+lax" or "+strict").
621 +Adding a second prefixed '+' causes the checksum-file updates to happen
622 +even when the transfer is in bf(--dry-run) mode ("++lax" or "++strict").
623 +There is also a perl script in the support directory named "rsyncsums"
624 +that can be used to update the .rsyncsums files.
625  
626  This option has no effect unless bf(--checksum, -c) was also specified.  It
627  also only affects the current side of the transfer, so if you want the
628 diff --git a/rsyncd.conf.yo b/rsyncd.conf.yo
629 --- a/rsyncd.conf.yo
630 +++ b/rsyncd.conf.yo
631 @@ -334,13 +334,15 @@ The default is tt(/var/run/rsyncd.lock).
632  dit(bf(checksum files)) This parameter tells rsync to make use of any cached
633  checksum information it finds in per-directory .rsyncsums files when the
634  current transfer is using the bf(--checksum) option.  The value can be set
635 -to either "lax", "strict", or "none" -- see the client's bf(--sumfiles)
636 -option for what these choices do.
637 +to either "lax", "strict", "+lax", "+strict", "++lax", "++strict", or
638 +"none".  See the client's bf(--sumfiles) option for what these choices do.
639  
640  Note also that the client's command-line option, bf(--sumfiles), has no
641  effect on a daemon.  A daemon will only access checksum files if this
642 -config option tells it to.  See also the bf(exclude) directive for a way
643 -to hide the .rsyncsums files from the user.
644 +config option tells it to.  You can configure updating of the .rsyncsums
645 +files even if the module itself is configured to be read-only.  See also
646 +the bf(exclude) directive for a way to hide the .rsyncsums files from the
647 +user.
648  
649  dit(bf(read only)) This parameter determines whether clients
650  will be able to upload files or not. If "read only" is true then any