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[tor-commits] [tor/master] Basic backend for the protocol-versions voting algorithm.
commit c1be8f9d574dace9941c532ce5d612c315bc74c7
Author: Nick Mathewson <nickm@xxxxxxxxxxxxxx>
Date: Fri Aug 19 18:04:02 2016 -0400
Basic backend for the protocol-versions voting algorithm.
[This is a brute-force method that potentially uses way too much
RAM. Need to rethink this a little. Right now you can DOS an
authority by saying "Foo=1-4294967295".]
---
src/or/protover.c | 217 +++++++++++++++++++++++++++++++++++++++++++++++
src/or/protover.h | 3 +
src/test/test_protover.c | 31 +++++++
3 files changed, 251 insertions(+)
diff --git a/src/or/protover.c b/src/or/protover.c
index b78978e..3a2d401 100644
--- a/src/or/protover.c
+++ b/src/or/protover.c
@@ -309,6 +309,223 @@ encode_protocol_list(const smartlist_t *sl)
return result;
}
+/** Voting helper: Given a list of proto_entry_t, return a newly allocated
+ * smartlist of newly allocated strings, one for each included protocol
+ * version. (So 'Foo=3,5-7' expands to a list of 'Foo=3', 'Foo=5', 'Foo=6',
+ * 'Foo=7'.)
+ *
+ * Do not list any protocol version more than once. */
+static smartlist_t *
+expand_protocol_list(const smartlist_t *protos)
+{
+ // XXXX This can make really huge lists from small inputs; that's a DoS
+ // problem.
+
+ smartlist_t *expanded = smartlist_new();
+ if (!protos)
+ return expanded;
+
+ SMARTLIST_FOREACH_BEGIN(protos, const proto_entry_t *, ent) {
+ const char *name = ent->name;
+ SMARTLIST_FOREACH_BEGIN(ent->ranges, const proto_range_t *, range) {
+ uint32_t u;
+ for (u = range->low; u <= range->high; ++u) {
+ smartlist_add_asprintf(expanded, "%s=%lu", name, (unsigned long)u);
+ }
+ } SMARTLIST_FOREACH_END(range);
+ } SMARTLIST_FOREACH_END(ent);
+
+ smartlist_sort_strings(expanded);
+ smartlist_uniq_strings(expanded); // This makes voting work. do not remove
+ return expanded;
+}
+
+/** Voting helper: compare two singleton proto_entry_t items by version
+ * alone. (A singleton item is one with a single range entry where
+ * low==high.) */
+static int
+cmp_single_ent_by_version(const void **a_, const void **b_)
+{
+ const proto_entry_t *ent_a = *a_;
+ const proto_entry_t *ent_b = *b_;
+
+ tor_assert(smartlist_len(ent_a->ranges) == 1);
+ tor_assert(smartlist_len(ent_b->ranges) == 1);
+
+ const proto_range_t *a = smartlist_get(ent_a->ranges, 0);
+ const proto_range_t *b = smartlist_get(ent_b->ranges, 0);
+
+ tor_assert(a->low == a->high);
+ tor_assert(b->low == b->high);
+
+ if (a->low < b->low) {
+ return -1;
+ } else if (a->low == b->low) {
+ return 0;
+ } else {
+ return 1;
+ }
+}
+
+/** Voting helper: Given a list of singleton protocol strings (of the form
+ * Foo=7), return a canonical listing of all the protocol versions listed,
+ * with as few ranges as possible, with protocol versions sorted lexically and
+ * versions sorted in numerically increasing order, using as few range entries
+ * as possible.
+ **/
+static char *
+contract_protocol_list(const smartlist_t *proto_strings)
+{
+ // map from name to list of single-version entries
+ strmap_t *entry_lists_by_name = strmap_new();
+ // list of protocol names
+ smartlist_t *all_names = smartlist_new();
+ // list of strings for the output we're building
+ smartlist_t *chunks = smartlist_new();
+
+ // Parse each item and stick it entry_lists_by_name. Build
+ // 'all_names' at the same time.
+ SMARTLIST_FOREACH_BEGIN(proto_strings, const char *, s) {
+ proto_entry_t *ent = parse_single_entry(s, s+strlen(s));
+ if (BUG(!ent))
+ continue;
+ smartlist_t *lst = strmap_get(entry_lists_by_name, ent->name);
+ if (!lst) {
+ smartlist_add(all_names, ent->name);
+ lst = smartlist_new();
+ strmap_set(entry_lists_by_name, ent->name, lst);
+ }
+ smartlist_add(lst, ent);
+ } SMARTLIST_FOREACH_END(s);
+
+ // We want to output the protocols sorted by their name.
+ smartlist_sort_strings(all_names);
+
+ SMARTLIST_FOREACH_BEGIN(all_names, const char *, name) {
+ const int first_entry = (name_sl_idx == 0);
+ smartlist_t *lst = strmap_get(entry_lists_by_name, name);
+ tor_assert(lst);
+ // Sort every entry with this name by version. They are
+ // singletons, so there can't be overlap.
+ smartlist_sort(lst, cmp_single_ent_by_version);
+
+ if (! first_entry)
+ smartlist_add(chunks, tor_strdup(" "));
+
+ /* We're going to construct this entry from the ranges. */
+ proto_entry_t *entry = tor_malloc_zero(sizeof(proto_entry_t));
+ entry->ranges = smartlist_new();
+ entry->name = tor_strdup(name);
+
+ // Now, find all the ranges of versions start..end where
+ // all of start, start+1, start+2, ..end are included.
+ int start_of_cur_series = 0;
+ while (start_of_cur_series < smartlist_len(lst)) {
+ const proto_entry_t *ent = smartlist_get(lst, start_of_cur_series);
+ const proto_range_t *range = smartlist_get(ent->ranges, 0);
+ const uint32_t ver_low = range->low;
+ uint32_t ver_high = ver_low;
+
+ int idx;
+ for (idx = start_of_cur_series+1; idx < smartlist_len(lst); ++idx) {
+ ent = smartlist_get(lst, idx);
+ range = smartlist_get(ent->ranges, 0);
+ if (range->low != ver_high + 1)
+ break;
+ ver_high += 1;
+ }
+
+ // Now idx is either off the end of the list, or the first sequence
+ // break in the list.
+ start_of_cur_series = idx;
+
+ proto_range_t *new_range = tor_malloc_zero(sizeof(proto_range_t));
+ new_range->low = ver_low;
+ new_range->high = ver_high;
+ smartlist_add(entry->ranges, new_range);
+ }
+ proto_entry_encode_into(chunks, entry);
+ proto_entry_free(entry);
+
+ } SMARTLIST_FOREACH_END(name);
+
+ // Build the result...
+ char *result = smartlist_join_strings(chunks, "", 0, NULL);
+
+ // And free all the stuff we allocated.
+ SMARTLIST_FOREACH_BEGIN(all_names, const char *, name) {
+ smartlist_t *lst = strmap_get(entry_lists_by_name, name);
+ tor_assert(lst);
+ SMARTLIST_FOREACH(lst, proto_entry_t *, e, proto_entry_free(e));
+ smartlist_free(lst);
+ } SMARTLIST_FOREACH_END(name);
+
+ strmap_free(entry_lists_by_name, NULL);
+ smartlist_free(all_names);
+ SMARTLIST_FOREACH(chunks, char *, cp, tor_free(cp));
+ smartlist_free(chunks);
+
+ return result;
+}
+
+/**
+ * Protocol voting implementation.
+ *
+ * Given a list of strings describing protocol versions, return a newly
+ * allocated string encoding all of the protocols that are listed by at
+ * least <b>threshold</b> of the inputs.
+ *
+ * The string is minimal and sorted according to the rules of
+ * contract_protocol_list above.
+ */
+char *
+compute_protover_vote(const smartlist_t *list_of_proto_strings,
+ int threshold)
+{
+ // XXXX This algorithm can be made to use too much RAM. Fix that.
+
+ smartlist_t *all_entries = smartlist_new();
+
+ // First, parse the inputs and break them into singleton entries.
+ SMARTLIST_FOREACH_BEGIN(list_of_proto_strings, const char *, vote) {
+ smartlist_t *unexpanded = parse_protocol_list(vote);
+ smartlist_t *this_vote = expand_protocol_list(unexpanded);
+ smartlist_add_all(all_entries, this_vote);
+ smartlist_free(this_vote);
+ SMARTLIST_FOREACH(unexpanded, proto_entry_t *, e, proto_entry_free(e));
+ smartlist_free(unexpanded);
+ } SMARTLIST_FOREACH_END(vote);
+
+ // Now sort the singleton entries
+ smartlist_sort_strings(all_entries);
+
+ // Now find all the strings that appear at least 'threshold' times.
+ smartlist_t *include_entries = smartlist_new();
+ const char *cur_entry = smartlist_get(all_entries, 0);
+ int n_times = 0;
+ SMARTLIST_FOREACH_BEGIN(all_entries, const char *, ent) {
+ if (!strcmp(ent, cur_entry)) {
+ n_times++;
+ } else {
+ if (n_times >= threshold)
+ smartlist_add(include_entries, (void*)cur_entry);
+ cur_entry = ent;
+ n_times = 1 ;
+ }
+ } SMARTLIST_FOREACH_END(ent);
+
+ if (n_times >= threshold)
+ smartlist_add(include_entries, (void*)cur_entry);
+
+ // Finally, compress that list.
+ char *result = contract_protocol_list(include_entries);
+ smartlist_free(include_entries);
+ SMARTLIST_FOREACH(all_entries, char *, cp, tor_free(cp));
+ smartlist_free(all_entries);
+
+ return result;
+}
+
/** Return true if every protocol version described in the string <b>s</b> is
* one that we support, and false otherwise. If <b>missing_out</b> is
* provided, set it to the list of protocols we do not support.
diff --git a/src/or/protover.h b/src/or/protover.h
index d12a067..f809a8d 100644
--- a/src/or/protover.h
+++ b/src/or/protover.h
@@ -27,6 +27,9 @@ int protover_all_supported(const char *s, char **missing);
int protover_is_supported_here(protocol_type_t pr, uint32_t ver);
const char *get_supported_protocols(void);
+char * compute_protover_vote(const smartlist_t *list_of_proto_strings,
+ int threshold);
+
void protover_free_all(void);
#ifdef PROTOVER_PRIVATE
diff --git a/src/test/test_protover.c b/src/test/test_protover.c
index 606ca57..2c72282 100644
--- a/src/test/test_protover.c
+++ b/src/test/test_protover.c
@@ -80,12 +80,43 @@ test_protover_parse(void *arg)
tor_free(re_encoded);
}
+static void
+test_protover_vote(void *arg)
+{
+ (void) arg;
+
+ smartlist_t *lst = smartlist_new();
+ char *result = compute_protover_vote(lst, 1);
+
+ tt_str_op(result, OP_EQ, "");
+ tor_free(result);
+
+ smartlist_add(lst, (void*) "Foo=1-10,500 Bar=1,3-7,8");
+ result = compute_protover_vote(lst, 1);
+ tt_str_op(result, OP_EQ, "Bar=1,3-8 Foo=1-10,500");
+ tor_free(result);
+
+ smartlist_add(lst, (void*) "Quux=123-456,78 Bar=2-6,8 Foo=9");
+ result = compute_protover_vote(lst, 1);
+ tt_str_op(result, OP_EQ, "Bar=1-8 Foo=1-10,500 Quux=78,123-456");
+ tor_free(result);
+
+ result = compute_protover_vote(lst, 2);
+ tt_str_op(result, OP_EQ, "Bar=3-6,8 Foo=9");
+ tor_free(result);
+
+ done:
+ tor_free(result);
+ smartlist_free(lst);
+}
+
#define PV_TEST(name, flags) \
{ #name, test_protover_ ##name, (flags), NULL, NULL }
struct testcase_t protover_tests[] = {
PV_TEST(parse, 0),
+ PV_TEST(vote, 0),
END_OF_TESTCASES
};
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