Pre-compress consensus diffs with supported consensus methods.

src/or/consdiffmgr.c

@@ -74,6 +74,25 @@ typedef enum cdm_diff_status_t {
   CDM_DIFF_ERROR=3,
 } cdm_diff_status_t;
 
+/** Which methods do we use for precompressing diffs? */
+static const compress_method_t compress_diffs_with[] = {
+  NO_METHOD,
+  GZIP_METHOD,
+#ifdef HAVE_LZMA
+  LZMA_METHOD,
+#endif
+#ifdef HAVE_ZSTD
+  ZSTD_METHOD,
+#endif
+};
+
+/** How many different methods will we try to use for diff compression? */
+STATIC unsigned
+n_diff_compression_methods(void)
+{
+  return ARRAY_LENGTH(compress_diffs_with);
+}
+
 /** Hashtable node used to remember the current status of the diff
  * from a given sha3 digest to the current consensus.  */
 typedef struct cdm_diff_t {
@@ -84,12 +103,15 @@ typedef struct cdm_diff_t {
   /** SHA3-256 digest of the consensus that this diff is _from_. (part of the
    * ht key) */
   uint8_t from_sha3[DIGEST256_LEN];
+  /** Method by which the diff is compressed. (part of the ht key */
+  compress_method_t compress_method;
 
   /** One of the CDM_DIFF_* values, depending on whether this diff
    * is available, in progress, or impossible to compute. */
   cdm_diff_status_t cdm_diff_status;
   /** SHA3-256 digest of the consensus that this diff is _to. */
   uint8_t target_sha3[DIGEST256_LEN];
+
   /** Handle to the cache entry for this diff, if any.  We use a handle here
    * to avoid thinking too hard about cache entry lifetime issues. */
   consensus_cache_entry_handle_t *entry;
@@ -121,9 +143,10 @@ static void consdiffmgr_set_cache_flags(void);
 static unsigned
 cdm_diff_hash(const cdm_diff_t *diff)
 {
-  uint8_t tmp[DIGEST256_LEN + 1];
+  uint8_t tmp[DIGEST256_LEN + 2];
   memcpy(tmp, diff->from_sha3, DIGEST256_LEN);
   tmp[DIGEST256_LEN] = (uint8_t) diff->flavor;
+  tmp[DIGEST256_LEN+1] = (uint8_t) diff->compress_method;
   return (unsigned) siphash24g(tmp, sizeof(tmp));
 }
 /** Helper: compare two cdm_diff_t objects for key equality */
@@ -131,7 +154,8 @@ static int
 cdm_diff_eq(const cdm_diff_t *diff1, const cdm_diff_t *diff2)
 {
   return fast_memeq(diff1->from_sha3, diff2->from_sha3, DIGEST256_LEN) &&
-    diff1->flavor == diff2->flavor;
+    diff1->flavor == diff2->flavor &&
+    diff1->compress_method == diff2->compress_method;
 }
 
 HT_PROTOTYPE(cdm_diff_ht, cdm_diff_t, node, cdm_diff_hash, cdm_diff_eq)
@@ -153,13 +177,15 @@ cdm_diff_free(cdm_diff_t *diff)
 static cdm_diff_t *
 cdm_diff_new(consensus_flavor_t flav,
              const uint8_t *from_sha3,
-             const uint8_t *target_sha3)
+             const uint8_t *target_sha3,
+             compress_method_t method)
 {
   cdm_diff_t *ent;
   ent = tor_malloc_zero(sizeof(cdm_diff_t));
   ent->flavor = flav;
   memcpy(ent->from_sha3, from_sha3, DIGEST256_LEN);
   memcpy(ent->target_sha3, target_sha3, DIGEST256_LEN);
+  ent->compress_method = method;
   return ent;
 }
 
@@ -177,18 +203,25 @@ cdm_diff_ht_check_and_note_pending(consensus_flavor_t flav,
                                    const uint8_t *target_sha3)
 {
   struct cdm_diff_t search, *ent;
+  unsigned u;
+  int result = 0;
+  for (u = 0; u < n_diff_compression_methods(); ++u) {
+    compress_method_t method = compress_diffs_with[u];
     memset(&search, 0, sizeof(cdm_diff_t));
     search.flavor = flav;
+    search.compress_method = method;
     memcpy(search.from_sha3, from_sha3, DIGEST256_LEN);
     ent = HT_FIND(cdm_diff_ht, &cdm_diff_ht, &search);
     if (ent) {
       tor_assert_nonfatal(ent->cdm_diff_status != CDM_DIFF_PRESENT);
-    return 1;
+      result = 1;
+      continue;
     }
-  ent = cdm_diff_new(flav, from_sha3, target_sha3);
+    ent = cdm_diff_new(flav, from_sha3, target_sha3, method);
     ent->cdm_diff_status = CDM_DIFF_IN_PROGRESS;
     HT_INSERT(cdm_diff_ht, &cdm_diff_ht, ent);
-  return 0;
+  }
+  return result;
 }
 
 /**
@@ -201,16 +234,18 @@ static void
 cdm_diff_ht_set_status(consensus_flavor_t flav,
                        const uint8_t *from_sha3,
                        const uint8_t *to_sha3,
+                       compress_method_t method,
                        int status,
                        consensus_cache_entry_handle_t *handle)
 {
   struct cdm_diff_t search, *ent;
   memset(&search, 0, sizeof(cdm_diff_t));
   search.flavor = flav;
+  search.compress_method = method,
   memcpy(search.from_sha3, from_sha3, DIGEST256_LEN);
   ent = HT_FIND(cdm_diff_ht, &cdm_diff_ht, &search);
   if (!ent) {
-    ent = cdm_diff_new(flav, from_sha3, to_sha3);
+    ent = cdm_diff_new(flav, from_sha3, to_sha3, method);
     ent->cdm_diff_status = CDM_DIFF_IN_PROGRESS;
     HT_INSERT(cdm_diff_ht, &cdm_diff_ht, ent);
   } else if (fast_memneq(ent->target_sha3, to_sha3, DIGEST256_LEN)) {
@@ -500,7 +535,8 @@ consdiffmgr_find_diff_from(consensus_cache_entry_t **entry_out,
                            consensus_flavor_t flavor,
                            int digest_type,
                            const uint8_t *digest,
-                           size_t digestlen)
+                           size_t digestlen,
+                           compress_method_t method)
 {
   if (BUG(digest_type != DIGEST_SHA3_256) ||
       BUG(digestlen != DIGEST256_LEN)) {
@@ -511,6 +547,7 @@ consdiffmgr_find_diff_from(consensus_cache_entry_t **entry_out,
   cdm_diff_t search, *ent;
   memset(&search, 0, sizeof(search));
   search.flavor = flavor;
+  search.compress_method = method;
   memcpy(search.from_sha3, digest, DIGEST256_LEN);
   ent = HT_FIND(cdm_diff_ht, &cdm_diff_ht, &search);
 
@@ -820,6 +857,16 @@ consdiffmgr_diffs_load(void)
     int flavor = networkstatus_parse_flavor_name(lv_flavor);
     if (flavor < 0)
       continue;
+    const char *lv_compression =
+      consensus_cache_entry_get_value(diff, LABEL_COMPRESSION_TYPE);
+    compress_method_t method = NO_METHOD;
+    if (lv_compression) {
+      method = compression_method_get_by_name(lv_compression);
+      if (method == UNKNOWN_METHOD) {
+        continue;
+      }
+    }
+
     uint8_t from_sha3[DIGEST256_LEN];
     uint8_t to_sha3[DIGEST256_LEN];
     if (cdm_entry_get_sha3_value(from_sha3, diff, LABEL_FROM_SHA3_DIGEST)<0)
@@ -828,6 +875,7 @@ consdiffmgr_diffs_load(void)
       continue;
 
     cdm_diff_ht_set_status(flavor, from_sha3, to_sha3,
+                           method,
                            CDM_DIFF_PRESENT,
                            consensus_cache_entry_handle_new(diff));
   } SMARTLIST_FOREACH_END(diff);
@@ -896,6 +944,18 @@ consdiffmgr_free_all(void)
    Thread workers
    =====*/
 
+typedef struct compressed_result_t {
+  config_line_t *labels;
+  /**
+   * Output: Body of the diff, as compressed.
+   */
+  uint8_t *body;
+  /**
+   * Output: length of body_out
+   */
+  size_t bodylen;
+} compressed_result_t;
+
 /**
  * An object passed to a worker thread that will try to produce a consensus
  * diff.
@@ -914,18 +974,8 @@ typedef struct consensus_diff_worker_job_t {
    */
   consensus_cache_entry_t *diff_to;
 
-  /**
+  /** Output: labels and bodies */
-   * Output: Labels to store in the cache associated with this diff.
+  compressed_result_t out[ARRAY_LENGTH(compress_diffs_with)];
-   */
-  config_line_t *labels_out;
-  /**
-   * Output: Body of the diff
-   */
-  uint8_t *body_out;
-  /**
-   * Output: length of body_out
-   */
-  size_t bodylen_out;
 } consensus_diff_worker_job_t;
 
 /** Given a consensus_cache_entry_t, check whether it has a label claiming
@@ -1040,23 +1090,55 @@ consensus_diff_worker_threadfn(void *state_, void *work_)
     return WQ_RPL_REPLY;
   }
 
-  /* Send the reply */
+  /* Compress the results and send the reply */
-  job->body_out = (uint8_t *) consensus_diff;
+  tor_assert(compress_diffs_with[0] == NO_METHOD);
-  job->bodylen_out = strlen(consensus_diff);
+  size_t difflen = strlen(consensus_diff);
+  job->out[0].body = (uint8_t *) consensus_diff;
+  job->out[0].bodylen = difflen;
 
-  cdm_labels_prepend_sha3(&job->labels_out, LABEL_SHA3_DIGEST,
+  config_line_t *common_labels = NULL;
-                          job->body_out, job->bodylen_out);
+  cdm_labels_prepend_sha3(&common_labels,
-  cdm_labels_prepend_sha3(&job->labels_out, LABEL_SHA3_DIGEST_UNCOMPRESSED,
+                          LABEL_SHA3_DIGEST_UNCOMPRESSED,
-                          job->body_out, job->bodylen_out);
+                          job->out[0].body,
-  config_line_prepend(&job->labels_out, LABEL_FROM_VALID_AFTER,
+                          job->out[0].bodylen);
+  config_line_prepend(&common_labels, LABEL_FROM_VALID_AFTER,
                       lv_from_valid_after);
-  config_line_prepend(&job->labels_out, LABEL_VALID_AFTER, lv_to_valid_after);
+  config_line_prepend(&common_labels, LABEL_VALID_AFTER,
-  config_line_prepend(&job->labels_out, LABEL_FLAVOR, lv_from_flavor);
+                      lv_to_valid_after);
-  config_line_prepend(&job->labels_out, LABEL_FROM_SHA3_DIGEST,
+  config_line_prepend(&common_labels, LABEL_FLAVOR, lv_from_flavor);
+  config_line_prepend(&common_labels, LABEL_FROM_SHA3_DIGEST,
                       lv_from_digest);
-  config_line_prepend(&job->labels_out, LABEL_TARGET_SHA3_DIGEST,
+  config_line_prepend(&common_labels, LABEL_TARGET_SHA3_DIGEST,
                       lv_to_digest);
-  config_line_prepend(&job->labels_out, LABEL_DOCTYPE, DOCTYPE_CONSENSUS_DIFF);
+  config_line_prepend(&common_labels, LABEL_DOCTYPE,
+                      DOCTYPE_CONSENSUS_DIFF);
+
+  job->out[0].labels = config_lines_dup(common_labels);
+  cdm_labels_prepend_sha3(&job->out[0].labels,
+                          LABEL_SHA3_DIGEST,
+                          job->out[0].body,
+                          job->out[0].bodylen);
+
+  unsigned u;
+  for (u = 1; u < n_diff_compression_methods(); ++u) {
+    compress_method_t method = compress_diffs_with[u];
+    const char *methodname = compression_method_get_name(method);
+    char *result;
+    size_t sz;
+    if (0 == tor_compress(&result, &sz, consensus_diff, difflen, method)) {
+      job->out[u].body = (uint8_t*)result;
+      job->out[u].bodylen = sz;
+      job->out[u].labels = config_lines_dup(common_labels);
+      cdm_labels_prepend_sha3(&job->out[u].labels, LABEL_SHA3_DIGEST,
+                              job->out[u].body,
+                              job->out[u].bodylen);
+      config_line_prepend(&job->out[u].labels,
+                          LABEL_COMPRESSION_TYPE,
+                          methodname);
+    }
+  }
+
+  config_free_lines(common_labels);
   return WQ_RPL_REPLY;
 }
 
@@ -1068,8 +1150,11 @@ consensus_diff_worker_job_free(consensus_diff_worker_job_t *job)
 {
   if (!job)
     return;
-  tor_free(job->body_out);
+  unsigned u;
-  config_free_lines(job->labels_out);
+  for (u = 0; u < n_diff_compression_methods(); ++u) {
+    config_free_lines(job->out[u].labels);
+    tor_free(job->out[u].body);
+  }
   consensus_cache_entry_decref(job->diff_from);
   consensus_cache_entry_decref(job->diff_to);
   tor_free(job);
@@ -1117,20 +1202,35 @@ consensus_diff_worker_replyfn(void *work_)
     cache = 0;
   }
 
-  int status;
+  int status = CDM_DIFF_ERROR;
-  consensus_cache_entry_handle_t *handle = NULL;
+  consensus_cache_entry_handle_t *handles[ARRAY_LENGTH(compress_diffs_with)];
-  if (job->body_out && job->bodylen_out && job->labels_out) {
+  memset(handles, 0, sizeof(handles));
+
+  unsigned u;
+  for (u = 0; u < n_diff_compression_methods(); ++u) {
+    compress_method_t method = compress_diffs_with[u];
+    uint8_t *body_out = job->out[u].body;
+    size_t bodylen_out = job->out[u].bodylen;
+    config_line_t *labels = job->out[u].labels;
+    const char *methodname = compression_method_get_name(method);
+    if (body_out && bodylen_out && labels) {
       /* Success! Store the results */
-    log_info(LD_DIRSERV, "Adding consensus diff from %s to %s",
+      log_info(LD_DIRSERV, "Adding consensus diff from %s to %s, "
-             lv_from_digest, lv_to_digest);
+               "compressed with %s",
+               lv_from_digest, lv_to_digest, methodname);
+
       consensus_cache_entry_t *ent =
-      consensus_cache_add(cdm_cache_get(), job->labels_out,
+        consensus_cache_add(cdm_cache_get(),
-                          job->body_out,
+                            labels,
-                          job->bodylen_out);
+                            body_out,
+                            bodylen_out);
+
       status = CDM_DIFF_PRESENT;
-    handle = consensus_cache_entry_handle_new(ent);
+      handles[u] = consensus_cache_entry_handle_new(ent);
       consensus_cache_entry_decref(ent);
-  } else {
+    }
+  }
+  if (status != CDM_DIFF_PRESENT) {
     /* Failure! Nothing to do but complain */
     log_warn(LD_DIRSERV,
              "Worker was unable to compute consensus diff "
@@ -1139,10 +1239,15 @@ consensus_diff_worker_replyfn(void *work_)
     status = CDM_DIFF_ERROR;
   }
 
-  if (cache)
+  for (u = 0; u < ARRAY_LENGTH(handles); ++u) {
-    cdm_diff_ht_set_status(flav, from_sha3, to_sha3, status, handle);
+    compress_method_t method = compress_diffs_with[u];
-  else
+    if (cache) {
-    consensus_cache_entry_handle_free(handle);
+      cdm_diff_ht_set_status(flav, from_sha3, to_sha3, method, status,
+                             handles[u]);
+    } else {
+      consensus_cache_entry_handle_free(handles[u]);
+    }
+  }
 
   consensus_diff_worker_job_free(job);
 }

src/or/consdiffmgr.h

@@ -28,7 +28,8 @@ consdiff_status_t consdiffmgr_find_diff_from(
                            consensus_flavor_t flavor,
                            int digest_type,
                            const uint8_t *digest,
-                           size_t digestlen);
+                           size_t digestlen,
+                           compress_method_t method);
 void consdiffmgr_rescan(void);
 int consdiffmgr_cleanup(void);
 void consdiffmgr_configure(const consdiff_cfg_t *cfg);
@@ -36,6 +37,7 @@ void consdiffmgr_free_all(void);
 int consdiffmgr_validate(void);
 
 #ifdef CONSDIFFMGR_PRIVATE
+STATIC unsigned n_diff_compression_methods(void);
 STATIC consensus_cache_t *cdm_cache_get(void);
 STATIC consensus_cache_entry_t *cdm_cache_lookup_consensus(
                           consensus_flavor_t flavor, time_t valid_after);

src/test/test_consdiffmgr.c

@@ -141,7 +141,8 @@ lookup_diff_from(consensus_cache_entry_t **out,
   uint8_t digest[DIGEST256_LEN];
   crypto_digest256((char*)digest, str1, strlen(str1), DIGEST_SHA3_256);
   return consdiffmgr_find_diff_from(out, flav,
-                                    DIGEST_SHA3_256, digest, sizeof(digest));
+                                    DIGEST_SHA3_256, digest, sizeof(digest),
+                                    NO_METHOD);
 }
 
 static int
@@ -373,7 +374,8 @@ test_consdiffmgr_make_diffs(void *arg)
   tt_int_op(1, OP_EQ, smartlist_len(fake_cpuworker_queue));
   diff_status = consdiffmgr_find_diff_from(&diff, FLAV_MICRODESC,
                                            DIGEST_SHA3_256,
-                                           md_ns_sha3, DIGEST256_LEN);
+                                           md_ns_sha3, DIGEST256_LEN,
+                                           NO_METHOD);
   tt_int_op(CONSDIFF_IN_PROGRESS, OP_EQ, diff_status);
 
   // Now run that process and get the diff.
@@ -384,7 +386,8 @@ test_consdiffmgr_make_diffs(void *arg)
   // At this point we should be able to get that diff.
   diff_status = consdiffmgr_find_diff_from(&diff, FLAV_MICRODESC,
                                            DIGEST_SHA3_256,
-                                           md_ns_sha3, DIGEST256_LEN);
+                                           md_ns_sha3, DIGEST256_LEN,
+                                           NO_METHOD);
   tt_int_op(CONSDIFF_AVAILABLE, OP_EQ, diff_status);
   tt_assert(diff);
 
@@ -757,7 +760,7 @@ test_consdiffmgr_cleanup_old_diffs(void *arg)
   /* Now add an even-more-recent consensus; this should make all previous
    * diffs deletable */
   tt_int_op(0, OP_EQ, consdiffmgr_add_consensus(md_body[3], md_ns[3]));
-  tt_int_op(2, OP_EQ, consdiffmgr_cleanup());
+  tt_int_op(2 * n_diff_compression_methods(), OP_EQ, consdiffmgr_cleanup());
 
   tt_int_op(CONSDIFF_NOT_FOUND, OP_EQ,
             lookup_diff_from(&ent, FLAV_MICRODESC, md_body[0]));