Merge bitcoin/bitcoin#34197: rpc, net: deprecate startingheight field of getpeerinfo RPC

4ce3f4a265 rpc, net: deprecate `startingheight` field of `getpeerinfo` RPC (Sebastian Falbesoner)

Pull request description:

  This PR deprecates the "startingheight" result field of the `getpeerinfo` RPC, following the discussion in #33990.

  Rationale: the reported starting height of a peer in the VERSION message is untrusted, and it doesn't seem to be useful anymore (after #20624), so deprecating the corresponding field seems reasonable. After that, it can be removed, along with the `m_starting_height` field of the Peer / CNodeStats structs, as it is sufficient to show the reported height only once at connection in the debug log.

ACKs for top commit:
  optout21:
    crACK 4ce3f4a265
  achow101:
    ACK 4ce3f4a265
  fjahr:
    utACK 4ce3f4a265
  rkrux:
    crACK 4ce3f4a265
  janb84:
    cr ACK 4ce3f4a265

Tree-SHA512: b296a28d30084fd35c67a2162e85576e3365e5d6fffe5b1add500034c1850604ee8c37b61afe812bfab8a7cc20f6a9e22db445e3c371311a5f82a777e5700ebf

doc/release-notes-34197.md

@@ -0,0 +1,7 @@
+Updated RPCs
+------------
+
+- The `getpeerinfo` RPC no longer returns the `startingheight` field unless
+  the configuration option `-deprecatedrpc=startingheight` is used. The
+  `startingheight` field will be fully removed in the next major release.
+  (#34197)

src/net_processing.cpp

@@ -268,6 +268,7 @@ struct Peer {
     bool m_outbound_version_message_sent GUARDED_BY(NetEventsInterface::g_msgproc_mutex){false};
 
     /** This peer's reported block height when we connected */
+    // TODO: remove in v32.0, only show reported height once in "receive version message: ..." debug log
     std::atomic<int> m_starting_height{-1};
 
     /** The pong reply we're expecting, or 0 if no pong expected. */

src/rpc/net.cpp

@@ -160,7 +160,7 @@ static RPCHelpMan getpeerinfo()
                     {RPCResult::Type::BOOL, "inbound", "Inbound (true) or Outbound (false)"},
                     {RPCResult::Type::BOOL, "bip152_hb_to", "Whether we selected peer as (compact blocks) high-bandwidth peer"},
                     {RPCResult::Type::BOOL, "bip152_hb_from", "Whether peer selected us as (compact blocks) high-bandwidth peer"},
-                    {RPCResult::Type::NUM, "startingheight", "The starting height (block) of the peer"},
+                    {RPCResult::Type::NUM, "startingheight", /*optional=*/true, "(DEPRECATED, returned only if config option -deprecatedrpc=startingheight is passed) The starting height (block) of the peer"},
                     {RPCResult::Type::NUM, "presynced_headers", "The current height of header pre-synchronization with this peer, or -1 if no low-work sync is in progress"},
                     {RPCResult::Type::NUM, "synced_headers", "The last header we have in common with this peer"},
                     {RPCResult::Type::NUM, "synced_blocks", "The last block we have in common with this peer"},
@@ -267,7 +267,9 @@ static RPCHelpMan getpeerinfo()
         obj.pushKV("inbound", stats.fInbound);
         obj.pushKV("bip152_hb_to", stats.m_bip152_highbandwidth_to);
         obj.pushKV("bip152_hb_from", stats.m_bip152_highbandwidth_from);
-        obj.pushKV("startingheight", statestats.m_starting_height);
+        if (IsDeprecatedRPCEnabled("startingheight")) {
+            obj.pushKV("startingheight", statestats.m_starting_height);
+        }
         obj.pushKV("presynced_headers", statestats.presync_height);
         obj.pushKV("synced_headers", statestats.nSyncHeight);
         obj.pushKV("synced_blocks", statestats.nCommonHeight);

test/functional/rpc_net.py

@@ -62,7 +62,10 @@ def seed_addrman(node):
 class NetTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 2
-        self.extra_args = [["-minrelaytxfee=0.00001000"], ["-minrelaytxfee=0.00000500"]]
+        self.extra_args = [
+            ["-minrelaytxfee=0.00001000", "-deprecatedrpc=startingheight"],
+            ["-minrelaytxfee=0.00000500"],
+        ]
         # Specify a non-working proxy to make sure no actual connections to public IPs are attempted
         for args in self.extra_args:
             args.append("-proxy=127.0.0.1:1")