Warn operators about upcoming unknown amendments:

* When an unknown amendment reaches majority, log an error-level
  message, and return a `warnings` array on all successful
  admin-level RPC calls to `server_info` and `server_state` with
  a message describing the problem, and the expected deadline.
* In addition to the `amendment_blocked` flag returned by
  `server_info` and `server_state`, return a warning with a more
  verbose description when the server is amendment blocked.
* Check on every flag ledger to see if the amendment(s) lose majority.
  Logs again if they don't, resumes normal operations if they did.

The intention is to give operators earlier warning that their
instances are in danger of being amendment blocked, which will
hopefully motivate them to update ahead of time.

src/test/rpc/AmendmentBlocked_test.cpp

@@ -20,6 +20,7 @@
 #include <test/jtx.h>
 #include <ripple/core/ConfigSections.h>
 #include <ripple/protocol/jss.h>
+#include <ripple/protocol/ErrorCodes.h>
 #include <ripple/app/misc/NetworkOPs.h>
 #include <test/jtx/WSClient.h>
 
@@ -39,7 +40,9 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         auto const USD = gw["USD"];
         auto const alice = Account {"alice"};
         auto const bob = Account {"bob"};
+        Account const ali {"ali", KeyType::secp256k1};
         env.fund (XRP(10000), alice, bob, gw);
+        env.memoize(ali);
         env.trust (USD(600), alice);
         env.trust (USD(700), bob);
         env(pay (gw, alice, USD(70)));
@@ -52,14 +55,17 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         // ledger_accept
         auto jr = env.rpc ("ledger_accept") [jss::result];
         BEAST_EXPECT (jr[jss::ledger_current_index] == current->seq ()+1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // ledger_current
         jr = env.rpc ("ledger_current") [jss::result];
         BEAST_EXPECT (jr[jss::ledger_current_index] == current->seq ()+1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // owner_info
         jr = env.rpc ("owner_info", alice.human()) [jss::result];
         BEAST_EXPECT (jr.isMember (jss::accepted) && jr.isMember (jss::current));
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // path_find
         Json::Value pf_req;
@@ -72,6 +78,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         BEAST_EXPECT (jr.isMember (jss::alternatives) &&
             jr[jss::alternatives].isArray() &&
             jr[jss::alternatives].size () == 1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // submit
         auto jt = env.jt (noop (alice));
@@ -80,10 +87,10 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         jr = env.rpc ("submit", strHex (s.slice ())) [jss::result];
         BEAST_EXPECT (jr.isMember (jss::engine_result) &&
             jr[jss::engine_result] == "tesSUCCESS");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // submit_multisigned
         env(signers(bob, 1, {{alice, 1}}), sig (bob));
-        Account const ali {"ali", KeyType::secp256k1};
         env(regkey (alice, ali));
         env.close();
 
@@ -101,6 +108,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         sign_for[jss::secret]  = ali.name();
         jr = env.rpc("json", "sign_for", to_string(sign_for)) [jss::result];
         BEAST_EXPECT(jr[jss::status] == "success");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         Json::Value ms_req;
         ms_req[jss::tx_json] = jr[jss::tx_json];
@@ -108,6 +116,74 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             [jss::result];
         BEAST_EXPECT (jr.isMember (jss::engine_result) &&
             jr[jss::engine_result] == "tesSUCCESS");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // set up an amendment warning. Nothing changes
+
+        env.app ().getOPs ().setAmendmentWarned ();
+
+        current = env.current ();
+        // ledger_accept
+        jr = env.rpc ("ledger_accept") [jss::result];
+        BEAST_EXPECT (jr[jss::ledger_current_index] == current->seq ()+1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // ledger_current
+        jr = env.rpc ("ledger_current") [jss::result];
+        BEAST_EXPECT (jr[jss::ledger_current_index] == current->seq ()+1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // owner_info
+        jr = env.rpc ("owner_info", alice.human()) [jss::result];
+        BEAST_EXPECT (jr.isMember (jss::accepted) && jr.isMember (jss::current));
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // path_find
+        pf_req[jss::subcommand] = "create";
+        pf_req[jss::source_account] = alice.human();
+        pf_req[jss::destination_account] = bob.human();
+        pf_req[jss::destination_amount] =
+            bob["USD"](20).value ().getJson (JsonOptions::none);
+        jr = wsc->invoke("path_find", pf_req) [jss::result];
+        BEAST_EXPECT (jr.isMember (jss::alternatives) &&
+            jr[jss::alternatives].isArray() &&
+            jr[jss::alternatives].size () == 1);
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // submit
+        jt = env.jt (noop (alice));
+        s.erase();
+        jt.stx->add (s);
+        jr = env.rpc ("submit", strHex (s.slice ())) [jss::result];
+        BEAST_EXPECT (jr.isMember (jss::engine_result) &&
+            jr[jss::engine_result] == "tesSUCCESS");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        // submit_multisigned
+        env(signers(bob, 1, {{alice, 1}}), sig (bob));
+        env(regkey (alice, ali));
+        env.close();
+
+        set_tx[jss::Account] = bob.human();
+        set_tx[jss::TransactionType] = jss::AccountSet;
+        set_tx[jss::Fee] =
+            (8 * env.current()->fees().base).jsonClipped();
+        set_tx[jss::Sequence] = env.seq(bob);
+        set_tx[jss::SigningPubKey] = "";
+
+        sign_for[jss::tx_json] = set_tx;
+        sign_for[jss::account] = alice.human();
+        sign_for[jss::secret]  = ali.name();
+        jr = env.rpc("json", "sign_for", to_string(sign_for)) [jss::result];
+        BEAST_EXPECT(jr[jss::status] == "success");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
+
+        ms_req[jss::tx_json] = jr[jss::tx_json];
+        jr = env.rpc("json", "submit_multisigned", to_string(ms_req))
+            [jss::result];
+        BEAST_EXPECT (jr.isMember (jss::engine_result) &&
+            jr[jss::engine_result] == "tesSUCCESS");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // make the network amendment blocked...now all the same
         // requests should fail
@@ -120,6 +196,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
         BEAST_EXPECT(jr[jss::status] == "error");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // ledger_current
         jr = env.rpc ("ledger_current") [jss::result];
@@ -127,6 +204,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
         BEAST_EXPECT(jr[jss::status] == "error");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // owner_info
         jr = env.rpc ("owner_info", alice.human()) [jss::result];
@@ -134,6 +212,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
         BEAST_EXPECT(jr[jss::status] == "error");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // path_find
         jr = wsc->invoke("path_find", pf_req) [jss::result];
@@ -141,6 +220,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
         BEAST_EXPECT(jr[jss::status] == "error");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // submit
         jr = env.rpc("submit", strHex(s.slice())) [jss::result];
@@ -148,6 +228,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
         BEAST_EXPECT(jr[jss::status] == "error");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
 
         // submit_multisigned
         set_tx[jss::Sequence] = env.seq(bob);
@@ -160,6 +241,7 @@ class AmendmentBlocked_test : public beast::unit_test::suite
         BEAST_EXPECT(
             jr.isMember (jss::error) &&
             jr[jss::error] == "amendmentBlocked");
+        BEAST_EXPECT(!jr.isMember(jss::warnings));
     }
 
 public: