commit bc91808c477ac05dc634ab10811b354b22da1ef5
Author: Nick Mathewson <nickm(a)torproject.org>
Date: Thu Apr 6 14:46:45 2017 -0400
Add a "Consensus diff manager" module.
This module's job is to remember old consensus documents, to
calculate their diffs on demand, and to .
There are some incomplete points in this code; I've marked them with
"XXXX". I intend to fix them in separate commits, since I believe
doing it in separate commits will make the branch easier to review.
---
src/or/consdiffmgr.c | 719 +++++++++++++++++++++++++++++++++++++++++++++++++++
src/or/consdiffmgr.h | 38 +++
src/or/include.am | 2 +
3 files changed, 759 insertions(+)
diff --git a/src/or/consdiffmgr.c b/src/or/consdiffmgr.c
new file mode 100644
index 0000000..7d26b0c
--- /dev/null
+++ b/src/or/consdiffmgr.c
@@ -0,0 +1,719 @@
+/* Copyright (c) 2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+/**
+ * \file consdiffmsr.c
+ *
+ * \brief consensus diff manager functions
+ *
+ * This module is run by directory authorities and caches in order
+ * to remember a number of past consensus documents, and to generate
+ * and serve the diffs from those documents to the latest consensus.
+ */
+
+#include "or.h"
+#include "conscache.h"
+#include "consdiff.h"
+#include "consdiffmgr.h"
+#include "cpuworker.h"
+#include "networkstatus.h"
+#include "workqueue.h"
+
+/* XXXX support compression */
+
+/**
+ * Labels to apply to items in the conscache object.
+ *
+ * @{
+ */
+/* One of DOCTYPE_CONSENSUS or DOCTYPE_CONSENSUS_DIFF */
+#define LABEL_DOCTYPE "document-type"
+/* The valid-after time for a consensus (or for the target consensus of a
+ * diff), encoded as ISO UTC. */
+#define LABEL_VALID_AFTER "consensus-valid-after"
+/* A hex encoded SHA3 digest of the object after decompression. */
+#define LABEL_SHA3_DIGEST "sha3-digest"
+/* The flavor of the consensus or consensuses diff */
+#define LABEL_FLAVOR "consensus-flavor"
+/* Diff only: the SHA3 digest of the source consensus. */
+#define LABEL_FROM_SHA3_DIGEST "from-sha3-digest"
+/* Diff only: the SHA3 digest of the target consensus. */
+#define LABEL_TARGET_SHA3_DIGEST "target-sha3-digest"
+/* Diff only: the valid-after date of the source consensus. */
+#define LABEL_FROM_VALID_AFTER "from-valid-after"
+/** @} */
+
+#define DOCTYPE_CONSENSUS "consensus"
+#define DOCTYPE_CONSENSUS_DIFF "consensus-diff"
+
+/**
+ * Underlying directory that stores consensuses and consensus diffs. Don't
+ * use this directly: use cdm_cache_get() instead.
+ */
+static consensus_cache_t *cons_diff_cache = NULL;
+/**
+ * If true, we have learned at least one new consensus since the
+ * consensus cache was last up-to-date.
+ */
+static int cdm_cache_dirty = 0;
+/**
+ * Configuration for this module
+ */
+static consdiff_cfg_t consdiff_cfg = {
+ /* .cache_max_age_hours = */ 24 * 90,
+ /* .cache_max_num = */ 1440
+};
+
+static int consensus_diff_queue_diff_work(consensus_cache_entry_t *diff_from,
+ consensus_cache_entry_t *diff_to);
+
+/**
+ * Helper: initialize <b>cons_diff_cache</b>.
+ */
+static void
+cdm_cache_init(void)
+{
+ unsigned n_entries = consdiff_cfg.cache_max_num * 2;
+
+ tor_assert(cons_diff_cache == NULL);
+ cons_diff_cache = consensus_cache_open("diff-cache", n_entries);
+ if (cons_diff_cache == NULL) {
+ log_err(LD_FS, "Error: Couldn't open storage for consensus diffs.");
+ tor_assert_unreached();
+ }
+ cdm_cache_dirty = 1;
+}
+
+/**
+ * Helper: return the consensus_cache_t * that backs this manager,
+ * initializing it if needed.
+ */
+static consensus_cache_t *
+cdm_cache_get(void)
+{
+ if (PREDICT_UNLIKELY(cons_diff_cache == NULL)) {
+ cdm_cache_init();
+ }
+ return cons_diff_cache;
+}
+
+/**
+ * Helper: given a list of labels, prepend the hex-encoded SHA3 digest
+ * of the <b>bodylen</b>-byte object at <b>body</b> to those labels,
+ * with LABEL_SHA3_DIGEST as its label.
+ */
+static void
+cdm_labels_prepend_sha3(config_line_t **labels,
+ const uint8_t *body,
+ size_t bodylen)
+{
+ uint8_t sha3_digest[DIGEST256_LEN];
+ char hexdigest[HEX_DIGEST256_LEN+1];
+ crypto_digest256((char *)sha3_digest,
+ (const char *)body, bodylen, DIGEST_SHA3_256);
+ base16_encode(hexdigest, sizeof(hexdigest),
+ (const char *)sha3_digest, sizeof(sha3_digest));
+
+ config_line_prepend(labels, LABEL_SHA3_DIGEST, hexdigest);
+}
+
+/**
+ * Helper: look for a consensus with the given <b>flavor</b> and
+ * <b>valid_after</b> time in the cache. Return that consensus if it's
+ * present, or NULL if it's missing.
+ */
+static consensus_cache_entry_t *
+cdm_cache_lookup_consensus(consensus_flavor_t flavor, time_t valid_after)
+{
+ char formatted_time[ISO_TIME_LEN+1];
+ format_iso_time_nospace(formatted_time, valid_after);
+ const char *flavname = networkstatus_get_flavor_name(flavor);
+
+ /* We'll filter by valid-after time first, since that should
+ * match the fewest documents. */
+ // XXXX This is stupid and it should be a hash table.
+ smartlist_t *matches = smartlist_new();
+ consensus_cache_find_all(matches, cdm_cache_get(),
+ LABEL_VALID_AFTER, formatted_time);
+ consensus_cache_filter_list(matches, LABEL_FLAVOR, flavname);
+ consensus_cache_filter_list(matches, LABEL_DOCTYPE, DOCTYPE_CONSENSUS);
+
+ consensus_cache_entry_t *result = NULL;
+ if (smartlist_len(matches) > 1) {
+ log_warn(LD_BUG, "How odd; there appear to be two matching consensuses "
+ "with flavor %s published at %s.",
+ flavname, formatted_time);
+ }
+ if (smartlist_len(matches)) {
+ result = smartlist_get(matches, 0);
+ }
+ smartlist_free(matches);
+
+ return result;
+}
+
+/**
+ * Given a string containing a networkstatus consensus, and the results of
+ * having parsed that consensus, add that consensus to the cache if it is not
+ * already present and not too old. Create new consensus diffs from or to
+ * that consensus as appropriate.
+ *
+ * Return 0 on success and -1 on failure.
+ */
+int
+consdiffmgr_add_consensus(const char *consensus,
+ const networkstatus_t *as_parsed)
+{
+ if (BUG(consensus == NULL) || BUG(as_parsed == NULL))
+ return -1; // LCOV_EXCL_LINE
+ if (BUG(as_parsed->type != NS_TYPE_CONSENSUS))
+ return -1; // LCOV_EXCL_LINE
+
+ const consensus_flavor_t flavor = as_parsed->flavor;
+ const time_t valid_after = as_parsed->valid_after;
+
+ if (valid_after < approx_time() - 3600 * consdiff_cfg.cache_max_age_hours) {
+ log_info(LD_DIRSERV, "We don't care about this consensus document; it's "
+ "too old.");
+ return -1;
+ }
+
+ /* Do we already have this one? */
+ consensus_cache_entry_t *entry =
+ cdm_cache_lookup_consensus(flavor, valid_after);
+ if (entry) {
+ log_info(LD_DIRSERV, "We already have a copy of that consensus");
+ return -1;
+ }
+
+ /* We don't have it. Add it to the cache. */
+ {
+ size_t bodylen = strlen(consensus);
+ config_line_t *labels = NULL;
+ char formatted_time[ISO_TIME_LEN+1];
+ format_iso_time_nospace(formatted_time, valid_after);
+ const char *flavname = networkstatus_get_flavor_name(flavor);
+
+ cdm_labels_prepend_sha3(&labels, (const uint8_t *)consensus, bodylen);
+ config_line_prepend(&labels, LABEL_FLAVOR, flavname);
+ config_line_prepend(&labels, LABEL_VALID_AFTER, formatted_time);
+ config_line_prepend(&labels, LABEL_DOCTYPE, DOCTYPE_CONSENSUS);
+
+ entry = consensus_cache_add(cdm_cache_get(),
+ labels,
+ (const uint8_t *)consensus,
+ bodylen);
+ config_free_lines(labels);
+ }
+
+ if (entry)
+ consensus_cache_entry_decref(entry);
+
+ cdm_cache_dirty = 1;
+ return entry ? 0 : -1;
+}
+
+/**
+ * Helper: used to sort two smartlists of consensus_cache_entry_t by their
+ * LABEL_VALID_AFTER labels.
+ */
+static int
+compare_by_valid_after_(const void **a, const void **b)
+{
+ const consensus_cache_entry_t *e1 = *a;
+ const consensus_cache_entry_t *e2 = *b;
+ /* We're in luck here: sorting UTC iso-encoded values lexically will work
+ * fine (until 9999). */
+ return strcmp_opt(consensus_cache_entry_get_value(e1, LABEL_VALID_AFTER),
+ consensus_cache_entry_get_value(e2, LABEL_VALID_AFTER));
+}
+
+/**
+ * Helper: Sort <b>lst</b> by LABEL_VALID_AFTER and return the most recent
+ * entry.
+ */
+static consensus_cache_entry_t *
+sort_and_find_most_recent(smartlist_t *lst)
+{
+ smartlist_sort(lst, compare_by_valid_after_);
+ if (smartlist_len(lst)) {
+ return smartlist_get(lst, smartlist_len(lst) - 1);
+ } else {
+ return NULL;
+ }
+}
+
+/**
+ * Look up consensus_cache_entry_t for the consensus of type <b>flavor</b>,
+ * from the source consensus with the specified digest (which must be SHA3).
+ *
+ * If the diff is present, store it into *<b>entry_out</b> and return
+ * CONSDIFF_AVAILABLE. Otherwise return CONSDIFF_NOT_FOUND or
+ * CONSDIFF_IN_PROGRESS.
+ */
+consdiff_status_t
+consdiffmgr_find_diff_from(consensus_cache_entry_t **entry_out,
+ consensus_flavor_t flavor,
+ int digest_type,
+ const uint8_t *digest,
+ size_t digestlen)
+{
+ // XXXX actually return IN_PROGRESS some times?
+ if (BUG(digest_type != DIGEST_SHA3_256) ||
+ BUG(digestlen != DIGEST256_LEN)) {
+ return CONSDIFF_NOT_FOUND; // LCOV_EXCL_LINE
+ }
+
+ char hex[HEX_DIGEST256_LEN+1];
+ base16_encode(hex, sizeof(hex), (const char *)digest, digestlen);
+ const char *flavname = networkstatus_get_flavor_name(flavor);
+
+ smartlist_t *matches = smartlist_new();
+ consensus_cache_find_all(matches, cdm_cache_get(),
+ LABEL_FROM_SHA3_DIGEST, hex);
+ consensus_cache_filter_list(matches, LABEL_FLAVOR, flavname);
+ consensus_cache_filter_list(matches, LABEL_DOCTYPE, DOCTYPE_CONSENSUS_DIFF);
+
+ *entry_out = sort_and_find_most_recent(matches);
+ consdiff_status_t result =
+ (*entry_out) ? CONSDIFF_AVAILABLE : CONSDIFF_NOT_FOUND;
+ smartlist_free(matches);
+
+ return result;
+}
+
+/**
+ * Perform periodic cleanup tasks on the consensus diff cache. Return
+ * the number of objects marked for deletion.
+ */
+int
+consdiffmgr_cleanup(void)
+{
+ smartlist_t *objects = smartlist_new();
+ smartlist_t *consensuses = smartlist_new();
+ smartlist_t *diffs = smartlist_new();
+ int n_to_delete = 0;
+
+ log_debug(LD_DIRSERV, "Looking for consdiffmgr entries to remove");
+
+ // 1. Delete any consensus or diff or anything whose valid_after is too old.
+ const time_t valid_after_cutoff =
+ approx_time() - 3600 * consdiff_cfg.cache_max_age_hours;
+
+ consensus_cache_find_all(objects, cdm_cache_get(),
+ NULL, NULL);
+ SMARTLIST_FOREACH_BEGIN(objects, consensus_cache_entry_t *, ent) {
+ const char *lv_valid_after =
+ consensus_cache_entry_get_value(ent, LABEL_VALID_AFTER);
+ if (! lv_valid_after) {
+ log_debug(LD_DIRSERV, "Ignoring entry because it had no %s label",
+ LABEL_VALID_AFTER);
+ continue;
+ }
+ time_t valid_after = 0;
+ if (parse_iso_time_nospace(lv_valid_after, &valid_after) < 0) {
+ log_debug(LD_DIRSERV, "Ignoring entry because its %s value (%s) was "
+ "unparseable", LABEL_VALID_AFTER, escaped(lv_valid_after));
+ continue;
+ }
+ if (valid_after < valid_after_cutoff) {
+ log_debug(LD_DIRSERV, "Deleting entry because its %s value (%s) was "
+ "too old", LABEL_VALID_AFTER, lv_valid_after);
+ consensus_cache_entry_mark_for_removal(ent);
+ ++n_to_delete;
+ }
+ } SMARTLIST_FOREACH_END(ent);
+
+ // 2. Delete all diffs that lead to a consensus whose valid-after is not the
+ // latest.
+ for (int flav = 0; flav < N_CONSENSUS_FLAVORS; ++flav) {
+ const char *flavname = networkstatus_get_flavor_name(flav);
+ /* Determine the most recent consensus of this flavor */
+ consensus_cache_find_all(consensuses, cdm_cache_get(),
+ LABEL_DOCTYPE, DOCTYPE_CONSENSUS);
+ consensus_cache_filter_list(consensuses, LABEL_FLAVOR, flavname);
+ consensus_cache_entry_t *most_recent =
+ sort_and_find_most_recent(consensuses);
+ if (most_recent == NULL)
+ continue;
+ const char *most_recent_sha3 =
+ consensus_cache_entry_get_value(most_recent, LABEL_SHA3_DIGEST);
+ if (BUG(most_recent_sha3 == NULL))
+ continue; // LCOV_EXCL_LINE
+
+ /* consider all such-flavored diffs, and look to see if they match. */
+ consensus_cache_find_all(diffs, cdm_cache_get(),
+ LABEL_DOCTYPE, DOCTYPE_CONSENSUS_DIFF);
+ consensus_cache_filter_list(diffs, LABEL_FLAVOR, flavname);
+ SMARTLIST_FOREACH_BEGIN(diffs, consensus_cache_entry_t *, diff) {
+ const char *this_diff_target_sha3 =
+ consensus_cache_entry_get_value(diff, LABEL_TARGET_SHA3_DIGEST);
+ if (!this_diff_target_sha3)
+ continue;
+ if (strcmp(this_diff_target_sha3, most_recent_sha3)) {
+ consensus_cache_entry_mark_for_removal(diff);
+ ++n_to_delete;
+ }
+ } SMARTLIST_FOREACH_END(diff);
+ smartlist_clear(consensuses);
+ smartlist_clear(diffs);
+ }
+
+ smartlist_free(objects);
+ smartlist_free(consensuses);
+ smartlist_free(diffs);
+ // XXXX for anything where the sha3 doesn't match -- delete it. But not
+ // XXXX here. Somewhere else?
+
+ // Actually remove files, if they're not used.
+ consensus_cache_delete_pending(cdm_cache_get());
+ return n_to_delete;
+}
+
+/**
+ * Initialize the consensus diff manager and its cache, and configure
+ * its parameters based on the latest torrc and networkstatus parameters.
+ */
+void
+consdiffmgr_configure(const consdiff_cfg_t *cfg)
+{
+ memcpy(&consdiff_cfg, cfg, sizeof(consdiff_cfg));
+
+ (void) cdm_cache_get();
+}
+
+/**
+ * Helper: build new diffs of <b>flavor</b> as needed
+ */
+static void
+consdiffmgr_rescan_flavor_(consensus_flavor_t flavor)
+{
+ smartlist_t *matches = NULL;
+ smartlist_t *diffs = NULL;
+ smartlist_t *compute_diffs_from = NULL;
+ strmap_t *have_diff_from = NULL;
+
+ // look for the most recent consensus, and for all previous in-range
+ // consensuses. Do they all have diffs to it?
+ const char *flavname = networkstatus_get_flavor_name(flavor);
+
+ // 1. find the most recent consensus, and the ones that we might want
+ // to diff to it.
+ matches = smartlist_new();
+ consensus_cache_find_all(matches, cdm_cache_get(),
+ LABEL_FLAVOR, flavname);
+ consensus_cache_filter_list(matches, LABEL_DOCTYPE, DOCTYPE_CONSENSUS);
+ consensus_cache_entry_t *most_recent = sort_and_find_most_recent(matches);
+ if (!most_recent) {
+ log_info(LD_DIRSERV, "No 'most recent' %s consensus found; "
+ "not making diffs", flavname);
+ goto done;
+ }
+ tor_assert(smartlist_len(matches));
+ smartlist_del(matches, smartlist_len(matches) - 1);
+
+ const char *most_recent_valid_after =
+ consensus_cache_entry_get_value(most_recent, LABEL_VALID_AFTER);
+ if (BUG(most_recent_valid_after == NULL))
+ goto done; //LCOV_EXCL_LINE
+
+ // 2. Find all the relevant diffs _to_ this consensus. These are ones
+ // that we don't need to compute.
+ diffs = smartlist_new();
+ consensus_cache_find_all(diffs, cdm_cache_get(),
+ LABEL_VALID_AFTER, most_recent_valid_after);
+ consensus_cache_filter_list(diffs, LABEL_DOCTYPE, DOCTYPE_CONSENSUS_DIFF);
+ consensus_cache_filter_list(diffs, LABEL_FLAVOR, flavname);
+ have_diff_from = strmap_new();
+ SMARTLIST_FOREACH_BEGIN(diffs, consensus_cache_entry_t *, diff) {
+ const char *va = consensus_cache_entry_get_value(diff,
+ LABEL_FROM_VALID_AFTER);
+ if (BUG(va == NULL))
+ continue; // LCOV_EXCL_LINE
+ strmap_set(have_diff_from, va, diff);
+ } SMARTLIST_FOREACH_END(diff);
+
+ // 3. See which consensuses in 'matches' don't have diffs yet.
+ smartlist_reverse(matches); // from newest to oldest.
+ compute_diffs_from = smartlist_new();
+ SMARTLIST_FOREACH_BEGIN(matches, consensus_cache_entry_t *, ent) {
+ const char *va = consensus_cache_entry_get_value(ent, LABEL_VALID_AFTER);
+ if (BUG(va == NULL))
+ continue; // LCOV_EXCL_LINE
+ if (strmap_get(have_diff_from, va) != NULL)
+ continue; /* we already have this one. */
+ smartlist_add(compute_diffs_from, ent);
+ } SMARTLIST_FOREACH_END(ent);
+
+ log_info(LD_DIRSERV,
+ "The most recent %s consensus is valid-after %s. We have diffs to "
+ "this consensus for %d/%d older %s consensuses. Generating diffs "
+ "for the other %d.",
+ flavname,
+ most_recent_valid_after,
+ smartlist_len(matches) - smartlist_len(compute_diffs_from),
+ smartlist_len(matches),
+ flavname,
+ smartlist_len(compute_diffs_from));
+
+ // 4. Actually launch the requests.
+ SMARTLIST_FOREACH_BEGIN(compute_diffs_from, consensus_cache_entry_t *, c) {
+ if (BUG(c == most_recent))
+ continue; // LCOV_EXCL_LINE
+
+ // XXXX how do we know that we are not already computing this?????
+ // XXXX DO NOT MERGE UNTIL THAT ISSUE IS SOLVED.
+ consensus_diff_queue_diff_work(c, most_recent);
+ } SMARTLIST_FOREACH_END(c);
+
+ done:
+ smartlist_free(matches);
+ smartlist_free(diffs);
+ smartlist_free(compute_diffs_from);
+ strmap_free(have_diff_from, NULL);
+}
+
+/**
+ * Build new diffs as needed.
+ */
+void
+consdiffmgr_rescan(void)
+{
+ if (cdm_cache_dirty == 0)
+ return;
+
+ // Clean up here to make room for new diffs, and to ensure that older
+ // consensuses do not have any entries.
+ consdiffmgr_cleanup();
+
+ for (int flav = 0; flav < N_CONSENSUS_FLAVORS; ++flav) {
+ consdiffmgr_rescan_flavor_((consensus_flavor_t) flav);
+ }
+
+ cdm_cache_dirty = 0;
+}
+
+/**
+ * Called before shutdown: drop all storage held by the consdiffmgr.c module.
+ */
+void
+consdiffmgr_free_all(void)
+{
+ consensus_cache_free(cons_diff_cache);
+ cons_diff_cache = NULL;
+}
+
+/* =====
+ Thread workers
+ =====*/
+
+/**
+ * An object passed to a worker thread that will try to produce a consensus
+ * diff.
+ */
+typedef struct consensus_diff_worker_job_t {
+ /**
+ * Input: The consensus to compute the diff from. Holds a reference to the
+ * cache entry, which must not be released until the job is passed back to
+ * the main thread. The body must be mapped into memory in the main thread.
+ */
+ consensus_cache_entry_t *diff_from;
+ /**
+ * Input: The consensus to compute the diff to. Holds a reference to the
+ * cache entry, which must not be released until the job is passed back to
+ * the main thread. The body must be mapped into memory in the main thread.
+ */
+ consensus_cache_entry_t *diff_to;
+
+ /**
+ * Output: Labels to store in the cache associated with this diff.
+ */
+ 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;
+
+/**
+ * Worker function. This function runs inside a worker thread and receives
+ * a consensus_diff_worker_job_t as its input.
+ */
+static workqueue_reply_t
+consensus_diff_worker_threadfn(void *state_, void *work_)
+{
+ (void)state_;
+ consensus_diff_worker_job_t *job = work_;
+ const uint8_t *diff_from, *diff_to;
+ size_t len_from, len_to;
+ int r;
+ /* We need to have the body already mapped into RAM here.
+ */
+ r = consensus_cache_entry_get_body(job->diff_from, &diff_from, &len_from);
+ if (BUG(r < 0))
+ return WQ_RPL_REPLY; // LCOV_EXCL_LINE
+ r = consensus_cache_entry_get_body(job->diff_to, &diff_to, &len_to);
+ if (BUG(r < 0))
+ return WQ_RPL_REPLY; // LCOV_EXCL_LINE
+
+ const char *lv_to_valid_after =
+ consensus_cache_entry_get_value(job->diff_to, LABEL_VALID_AFTER);
+ const char *lv_from_valid_after =
+ consensus_cache_entry_get_value(job->diff_from, LABEL_VALID_AFTER);
+ const char *lv_from_digest =
+ consensus_cache_entry_get_value(job->diff_from, LABEL_SHA3_DIGEST);
+ const char *lv_from_flavor =
+ consensus_cache_entry_get_value(job->diff_from, LABEL_FLAVOR);
+ const char *lv_to_flavor =
+ consensus_cache_entry_get_value(job->diff_to, LABEL_FLAVOR);
+ const char *lv_to_digest =
+ consensus_cache_entry_get_value(job->diff_to, LABEL_SHA3_DIGEST);
+
+ /* All these values are mandatory on the input */
+ if (BUG(!lv_to_valid_after) ||
+ BUG(!lv_from_valid_after) ||
+ BUG(!lv_from_digest) ||
+ BUG(!lv_from_flavor) ||
+ BUG(!lv_to_flavor)) {
+ return WQ_RPL_REPLY; // LCOV_EXCL_LINE
+ }
+ /* The flavors need to match */
+ if (BUG(strcmp(lv_from_flavor, lv_to_flavor))) {
+ return WQ_RPL_REPLY; // LCOV_EXCL_LINE
+ }
+
+ char *consensus_diff;
+ {
+ // XXXX the input might not be nul-terminated. And also we wanted to
+ // XXXX support compression later I guess. So, we need to copy here.
+ char *diff_from_nt, *diff_to_nt;
+ diff_from_nt = tor_memdup_nulterm(diff_from, len_from);
+ diff_to_nt = tor_memdup_nulterm(diff_to, len_to);
+
+ // XXXX ugh; this is going to calculate the SHA3 of both its
+ // XXXX inputs again, even though we already have that. Maybe it's time
+ // XXXX to change the API here?
+ consensus_diff = consensus_diff_generate(diff_from_nt, diff_to_nt);
+ tor_free(diff_from_nt);
+ tor_free(diff_to_nt);
+ }
+ if (!consensus_diff) {
+ /* Couldn't generate consensus; we'll leave the reply blank. */
+ return WQ_RPL_REPLY;
+ }
+
+ /* Send the reply */
+ job->body_out = (uint8_t *) consensus_diff;
+ job->bodylen_out = strlen(consensus_diff);
+
+ cdm_labels_prepend_sha3(&job->labels_out, job->body_out, job->bodylen_out);
+ config_line_prepend(&job->labels_out, LABEL_FROM_VALID_AFTER,
+ lv_from_valid_after);
+ config_line_prepend(&job->labels_out, LABEL_VALID_AFTER, lv_to_valid_after);
+ config_line_prepend(&job->labels_out, LABEL_FLAVOR, lv_from_flavor);
+ config_line_prepend(&job->labels_out, LABEL_FROM_SHA3_DIGEST,
+ lv_from_digest);
+ config_line_prepend(&job->labels_out, LABEL_TARGET_SHA3_DIGEST,
+ lv_to_digest);
+ config_line_prepend(&job->labels_out, LABEL_DOCTYPE, DOCTYPE_CONSENSUS_DIFF);
+ return WQ_RPL_REPLY;
+}
+
+/**
+ * Helper: release all storage held in <b>job</b>.
+ */
+static void
+consensus_diff_worker_job_free(consensus_diff_worker_job_t *job)
+{
+ if (!job)
+ return;
+ tor_free(job->body_out);
+ config_free_lines(job->labels_out);
+ consensus_cache_entry_decref(job->diff_from);
+ consensus_cache_entry_decref(job->diff_to);
+ tor_free(job);
+}
+
+/**
+ * Worker function: This function runs in the main thread, and receives
+ * a consensus_diff_worker_job_t that the worker thread has already
+ * processed.
+ */
+static void
+consensus_diff_worker_replyfn(void *work_)
+{
+ tor_assert(in_main_thread());
+ tor_assert(work_);
+
+ consensus_diff_worker_job_t *job = work_;
+
+ const char *lv_from_digest =
+ consensus_cache_entry_get_value(job->diff_from, LABEL_SHA3_DIGEST);
+ const char *lv_to_digest =
+ consensus_cache_entry_get_value(job->diff_to, LABEL_SHA3_DIGEST);
+ if (BUG(lv_from_digest == NULL))
+ lv_from_digest = "???"; // LCOV_EXCL_LINE
+ if (BUG(lv_to_digest == NULL))
+ lv_to_digest = "???"; // LCOV_EXCL_LINE
+
+ if (job->body_out && job->bodylen_out && job->labels_out) {
+ /* Success! Store the results */
+ log_info(LD_DIRSERV, "Adding consensus diff from %s to %s",
+ lv_from_digest, lv_to_digest);
+ consensus_cache_add(cdm_cache_get(), job->labels_out,
+ job->body_out,
+ job->bodylen_out);
+ } else {
+ /* Failure! Nothing to do but complain */
+ log_warn(LD_DIRSERV,
+ "Worker was unable to compute consensus diff "
+ "from %s to %s", lv_from_digest, lv_to_digest);
+ /* XXXX Actually, we should cache this failure and not repeat the
+ * attempt over and over */
+ }
+
+ consensus_diff_worker_job_free(job);
+}
+
+/**
+ * Queue the job of computing the diff from <b>diff_from</b> to <b>diff_to</b>
+ * in a worker thread.
+ */
+static int
+consensus_diff_queue_diff_work(consensus_cache_entry_t *diff_from,
+ consensus_cache_entry_t *diff_to)
+{
+ tor_assert(in_main_thread());
+
+ consensus_cache_entry_incref(diff_from);
+ consensus_cache_entry_incref(diff_to);
+
+ consensus_diff_worker_job_t *job = tor_malloc_zero(sizeof(*job));
+ job->diff_from = diff_from;
+ job->diff_to = diff_to;
+
+ /* Make sure body is mapped. */
+ const uint8_t *body;
+ size_t bodylen;
+ int r1 = consensus_cache_entry_get_body(diff_from, &body, &bodylen);
+ int r2 = consensus_cache_entry_get_body(diff_to, &body, &bodylen);
+ if (r1 < 0 || r2 < 0)
+ goto err;
+
+ workqueue_entry_t *work;
+ work = cpuworker_queue_work(consensus_diff_worker_threadfn,
+ consensus_diff_worker_replyfn,
+ job);
+ if (!work)
+ goto err;
+
+ return 0;
+ err:
+ consensus_diff_worker_job_free(job); // includes decrefs.
+ return -1;
+}
+
diff --git a/src/or/consdiffmgr.h b/src/or/consdiffmgr.h
new file mode 100644
index 0000000..860e055
--- /dev/null
+++ b/src/or/consdiffmgr.h
@@ -0,0 +1,38 @@
+/* Copyright (c) 2017, The Tor Project, Inc. */
+/* See LICENSE for licensing information */
+
+#ifndef TOR_CONSDIFFMGR_H
+#define TOR_CONSDIFFMGR_H
+
+/**
+ * Possible outcomes from trying to look up a given consensus diff.
+ */
+typedef enum consdiff_status_t {
+ CONSDIFF_AVAILABLE,
+ CONSDIFF_NOT_FOUND,
+ CONSDIFF_IN_PROGRESS,
+} consdiff_status_t;
+
+typedef struct consdiff_cfg_t {
+ uint32_t cache_max_age_hours;
+ uint32_t cache_max_num;
+} consdiff_cfg_t;
+
+struct consensus_cache_entry_t; // from conscache.h
+
+int consdiffmgr_add_consensus(const char *consensus,
+ const networkstatus_t *as_parsed);
+
+consdiff_status_t consdiffmgr_find_diff_from(
+ struct consensus_cache_entry_t **entry_out,
+ consensus_flavor_t flavor,
+ int digest_type,
+ const uint8_t *digest,
+ size_t digestlen);
+void consdiffmgr_rescan(void);
+int consdiffmgr_cleanup(void);
+void consdiffmgr_configure(const consdiff_cfg_t *cfg);
+void consdiffmgr_free_all(void);
+
+#endif
+
diff --git a/src/or/include.am b/src/or/include.am
index 1841bbf..dd27bc8 100644
--- a/src/or/include.am
+++ b/src/or/include.am
@@ -38,6 +38,7 @@ LIBTOR_A_SOURCES = \
src/or/connection_or.c \
src/or/conscache.c \
src/or/consdiff.c \
+ src/or/consdiffmgr.c \
src/or/control.c \
src/or/cpuworker.c \
src/or/dircollate.c \
@@ -156,6 +157,7 @@ ORHEADERS = \
src/or/connection_or.h \
src/or/conscache.h \
src/or/consdiff.h \
+ src/or/consdiffmgr.h \
src/or/control.h \
src/or/cpuworker.h \
src/or/dircollate.h \
