Merge #11456: Replace relevant services logic with a function suite.

15f5d3b17 Switch DNSSeed-needed metric to any-automatic-nodes, not services (Matt Corallo)
5ee88b4bd Clarify docs for requirements/handling of addnode/connect nodes (Matt Corallo)
57edc0b0c Rename fAddnode to a more-descriptive "manual_connection" (Matt Corallo)
44407100f Replace relevant services logic with a function suite. (Matt Corallo)

Pull request description:

  This was mostly written as a way to clean things up so that the NETWORK_LIMITED PR (#10387) can be simplified a ton, but its also a nice standalone cleanup that will also require a bit of review because it tweaks a lot of stuff across net. The new functions are fine in protocol.h right now since they're straight-forward, but after NETWORK_LIMITED will really want to move elsewhere after @theuni moves the nServices-based selection to addrman from connman.

  Adds HasAllRelevantServices and GetRelevantServices, which check
  for NETWORK|WITNESS.

  This changes the following:
   * Removes nRelevantServices from CConnman, disconnecting it a bit
     more from protocol-level logic.
   * Replaces our sometimes-connect-to-!WITNESS-nodes logic with
     simply always requiring WITNESS|NETWORK for outbound non-feeler
     connections (feelers still only require NETWORK).
   * This has the added benefit of removing nServicesExpected from
     CNode - instead letting net_processing's VERSION message
     handling simply check HasAllRelevantServices.
   * This implies we believe WITNESS nodes to continue to be a
     significant majority of nodes on the network, but also because
     we cannot sync properly from !WITNESS nodes, it is strange to
     continue using our valuable outbound slots on them.
   * In order to prevent this change from preventing connection to
     -connect= nodes which have !WITNESS, -connect nodes are now
     given the "addnode" flag. This also allows outbound connections
     to !NODE_NETWORK nodes for -connect nodes (which was already true
     of addnodes).
   * Has the (somewhat unintended) consequence of changing one of the
     eviction metrics from the same
     sometimes-connect-to-!WITNESS-nodes metric to requiring
     HasRelevantServices.

  This should make NODE_NETWORK_LIMITED much simpler to implement.

Tree-SHA512: 90606896c86cc5da14c77843b16674a6a012065e7b583d76d1c47a18215358abefcbab44ff4fab3fadcd39aa9a42d4740c6dc8874a58033bdfc8ad3fb5c649fc

src/rpc/net.cpp

@@ -92,7 +92,7 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
             "    \"version\": v,              (numeric) The peer version, such as 7001\n"
             "    \"subver\": \"/Satoshi:0.8.5/\",  (string) The string version\n"
             "    \"inbound\": true|false,     (boolean) Inbound (true) or Outbound (false)\n"
-            "    \"addnode\": true|false,     (boolean) Whether connection was due to addnode and is using an addnode slot\n"
+            "    \"addnode\": true|false,     (boolean) Whether connection was due to addnode/-connect or if it was an automatic/inbound connection\n"
             "    \"startingheight\": n,       (numeric) The starting height (block) of the peer\n"
             "    \"banscore\": n,             (numeric) The ban score\n"
             "    \"synced_headers\": n,       (numeric) The last header we have in common with this peer\n"
@@ -156,7 +156,7 @@ UniValue getpeerinfo(const JSONRPCRequest& request)
         // their ver message.
         obj.push_back(Pair("subver", stats.cleanSubVer));
         obj.push_back(Pair("inbound", stats.fInbound));
-        obj.push_back(Pair("addnode", stats.fAddnode));
+        obj.push_back(Pair("addnode", stats.m_manual_connection));
         obj.push_back(Pair("startingheight", stats.nStartingHeight));
         if (fStateStats) {
             obj.push_back(Pair("banscore", statestats.nMisbehavior));
@@ -201,6 +201,8 @@ UniValue addnode(const JSONRPCRequest& request)
             "addnode \"node\" \"add|remove|onetry\"\n"
             "\nAttempts to add or remove a node from the addnode list.\n"
             "Or try a connection to a node once.\n"
+            "Nodes added using addnode (or -connect) are protected from DoS disconnection and are not required to be\n"
+            "full nodes/support SegWit as other outbound peers are (though such peers will not be synced from).\n"
             "\nArguments:\n"
             "1. \"node\"     (string, required) The node (see getpeerinfo for nodes)\n"
             "2. \"command\"  (string, required) 'add' to add a node to the list, 'remove' to remove a node from the list, 'onetry' to try a connection to the node once\n"
@@ -217,7 +219,7 @@ UniValue addnode(const JSONRPCRequest& request)
     if (strCommand == "onetry")
     {
         CAddress addr;
-        g_connman->OpenNetworkConnection(addr, false, nullptr, strNode.c_str());
+        g_connman->OpenNetworkConnection(addr, false, nullptr, strNode.c_str(), false, false, true);
         return NullUniValue;
     }