Add a function to check for support for "protocol X or later"

Also, add unit tests for this new function and for the regular
"does this list include support for protocol X" code.

src/or/protover.c

@@ -280,6 +280,42 @@ protocol_list_supports_protocol(const char *list, protocol_type_t tp,
   return contains;
 }
 
+/**
+ * Return true iff "list" encodes a protocol list that includes support for
+ * the indicated protocol and version, or some later version.
+ */
+int
+protocol_list_supports_protocol_or_later(const char *list,
+                                         protocol_type_t tp,
+                                         uint32_t version)
+{
+  /* NOTE: This is a pretty inefficient implementation. If it ever shows
+   * up in profiles, we should memoize it.
+   */
+  smartlist_t *protocols = parse_protocol_list(list);
+  if (!protocols) {
+    return 0;
+  }
+  const char *pr_name = protocol_type_to_str(tp);
+
+  int contains = 0;
+  SMARTLIST_FOREACH_BEGIN(protocols, proto_entry_t *, proto) {
+    if (strcasecmp(proto->name, pr_name))
+      continue;
+    SMARTLIST_FOREACH_BEGIN(proto->ranges, const proto_range_t *, range) {
+      if (range->high >= version) {
+        contains = 1;
+        goto found;
+      }
+    } SMARTLIST_FOREACH_END(range);
+  } SMARTLIST_FOREACH_END(proto);
+
+ found:
+  SMARTLIST_FOREACH(protocols, proto_entry_t *, ent, proto_entry_free(ent));
+  smartlist_free(protocols);
+  return contains;
+}
+
 /** Return the canonical string containing the list of protocols
  * that we support. */
 const char *

src/or/protover.h

@@ -47,6 +47,9 @@ char *protover_compute_vote(const smartlist_t *list_of_proto_strings,
 const char *protover_compute_for_old_tor(const char *version);
 int protocol_list_supports_protocol(const char *list, protocol_type_t tp,
                                     uint32_t version);
+int protocol_list_supports_protocol_or_later(const char *list,
+                                             protocol_type_t tp,
+                                             uint32_t version);
 
 void protover_free_all(void);
 

src/test/test_protover.c

@@ -182,6 +182,35 @@ test_protover_all_supported(void *arg)
   tor_free(msg);
 }
 
+static void
+test_protover_supports_version(void *arg)
+{
+  (void)arg;
+
+  tt_assert(protocol_list_supports_protocol("Link=3-6", PRT_LINK, 3));
+  tt_assert(protocol_list_supports_protocol("Link=3-6", PRT_LINK, 6));
+  tt_assert(!protocol_list_supports_protocol("Link=3-6", PRT_LINK, 7));
+  tt_assert(!protocol_list_supports_protocol("Link=3-6", PRT_LINKAUTH, 3));
+
+  tt_assert(!protocol_list_supports_protocol("Link=4-6 LinkAuth=3",
+                                            PRT_LINKAUTH, 2));
+  tt_assert(protocol_list_supports_protocol("Link=4-6 LinkAuth=3",
+                                            PRT_LINKAUTH, 3));
+  tt_assert(!protocol_list_supports_protocol("Link=4-6 LinkAuth=3",
+                                             PRT_LINKAUTH, 4));
+  tt_assert(!protocol_list_supports_protocol_or_later("Link=4-6 LinkAuth=3",
+                                             PRT_LINKAUTH, 4));
+  tt_assert(protocol_list_supports_protocol_or_later("Link=4-6 LinkAuth=3",
+                                             PRT_LINKAUTH, 3));
+  tt_assert(protocol_list_supports_protocol_or_later("Link=4-6 LinkAuth=3",
+                                             PRT_LINKAUTH, 2));
+
+  tt_assert(!protocol_list_supports_protocol_or_later("Link=4-6 LinkAuth=3",
+                                                      PRT_DESC, 2));
+ done:
+ ;
+}
+
 #define PV_TEST(name, flags)                       \
   { #name, test_protover_ ##name, (flags), NULL, NULL }
 
@@ -190,6 +219,7 @@ struct testcase_t protover_tests[] = {
   PV_TEST(parse_fail, 0),
   PV_TEST(vote, 0),
   PV_TEST(all_supported, 0),
+  PV_TEST(supports_version, 0),
   END_OF_TESTCASES
 };