Merge bitcoin/bitcoin#30594: docs: doc update for mempoolfullrbf default + log deprecation

1f93e3c360 add deprecation warning for mempoolfullrbf (glozow)
4400c979a3 [doc] update documentation for new mempoolfullrbf default (glozow)

Pull request description:

  Followup to #30493. Update bips.md and policy/*.md to reflect new default rules around signaling requirements in RBF.
  Also, log a warning when `-mempoolfullrbf=0` that this config option is deprecated and will be removed in a future release.

ACKs for top commit:
  petertodd:
    ACK 1f93e3c360
  instagibbs:
    ACK 1f93e3c360
  tdb3:
    ACK 1f93e3c360

Tree-SHA512: f60a9524f15cfaa4c10c40b6f62b787d3f9865aac48ca883def30efac4f8a118f1359532f1b209ea34e201f0b1c92398abc8bc1e439e6b60910cc7f75c51e9ae

doc/bips.md

@@ -33,7 +33,7 @@ BIPs that are implemented by Bitcoin Core:
 * [`BIP 111`](https://github.com/bitcoin/bips/blob/master/bip-0111.mediawiki): `NODE_BLOOM` service bit added, and enforced for all peer versions as of **v0.13.0** ([PR #6579](https://github.com/bitcoin/bitcoin/pull/6579) and [PR #6641](https://github.com/bitcoin/bitcoin/pull/6641)).
 * [`BIP 112`](https://github.com/bitcoin/bips/blob/master/bip-0112.mediawiki): The CHECKSEQUENCEVERIFY opcode has been implemented since **v0.12.1** ([PR #7524](https://github.com/bitcoin/bitcoin/pull/7524)), and has been *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).
 * [`BIP 113`](https://github.com/bitcoin/bips/blob/master/bip-0113.mediawiki): Median time past lock-time calculations have been implemented since **v0.12.1** ([PR #6566](https://github.com/bitcoin/bitcoin/pull/6566)), and has been *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).
-* [`BIP 125`](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki): Opt-in full replace-by-fee signaling partially implemented. See doc/policy/mempool-replacements.md.
+* [`BIP 125`](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki): Opt-in full replace-by-fee partially implemented: signaling is enforced if configured. For other replacement rules, see doc/policy/mempool-replacements.md.
 * [`BIP 130`](https://github.com/bitcoin/bips/blob/master/bip-0130.mediawiki): direct headers announcement is negotiated with peer versions `>=70012` as of **v0.12.0** ([PR 6494](https://github.com/bitcoin/bitcoin/pull/6494)).
 * [`BIP 133`](https://github.com/bitcoin/bips/blob/master/bip-0133.mediawiki): feefilter messages are respected and sent for peer versions `>=70013` as of **v0.13.0** ([PR 7542](https://github.com/bitcoin/bitcoin/pull/7542)).
 * [`BIP 141`](https://github.com/bitcoin/bips/blob/master/bip-0141.mediawiki): Segregated Witness (Consensus Layer) as of **v0.13.0** ([PR 8149](https://github.com/bitcoin/bitcoin/pull/8149)), defined for mainnet as of **v0.13.1** ([PR 8937](https://github.com/bitcoin/bitcoin/pull/8937)), and *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).

doc/policy/mempool-replacements.md

@@ -10,14 +10,12 @@ A transaction ("replacement transaction") may replace its directly conflicting t
 their in-mempool descendants (together, "original transactions") if, in addition to passing all
 other consensus and policy rules, each of the following conditions are met:
 
-1. The directly conflicting transactions all signal replaceability explicitly. A transaction is
+1. If `-mempoolfullrbf=0` (the value is 1 by default), the directly conflicting transactions all signal replaceability explicitly. A transaction is
    signaling BIP125 replaceability if any of its inputs have an nSequence number less than (0xffffffff - 1).
    A transaction also signals replaceability if its version field is set to 3.
 
    *Rationale*: See [BIP125
    explanation](https://github.com/bitcoin/bips/blob/master/bip-0125.mediawiki#motivation).
-   Use the (`-mempoolfullrbf`) configuration option to allow transaction replacement without enforcement of the
-   opt-in signaling rule.
 
 2. The replacement transaction only include an unconfirmed input if that input was included in
    one of the directly conflicting transactions. An unconfirmed input spends an output from a
@@ -80,3 +78,5 @@ This set of rules is similar but distinct from BIP125.
 
 * Full replace-by-fee enabled as a configurable mempool policy as of **v24.0** ([PR
   #25353](https://github.com/bitcoin/bitcoin/pull/25353)).
+
+* Full replace-by-fee is the default policy as of **v28.0** ([PR #30493](https://github.com/bitcoin/bitcoin/pull/30493)).

doc/policy/packages.md

@@ -38,7 +38,7 @@ The following rules are enforced for all packages:
 
 * Only limited package replacements are currently considered. (#28984)
 
-   - All direct conflicts must signal replacement (or the node must have `-mempoolfullrbf=1` set).
+   - If `-mempoolfullrbf=0` (the value is 1 by default), all direct conflicts must signal replacement.
 
    - Packages are 1-parent-1-child, with no in-mempool ancestors of the package.
 

src/init.cpp

@@ -645,7 +645,7 @@ void SetupServerArgs(ArgsManager& argsman)
                              "is of this size or less (default: %u)",
                              MAX_OP_RETURN_RELAY),
                    ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
-    argsman.AddArg("-mempoolfullrbf", strprintf("Accept transaction replace-by-fee without requiring replaceability signaling (default: %u)", DEFAULT_MEMPOOL_FULL_RBF), ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
+    argsman.AddArg("-mempoolfullrbf", strprintf("(DEPRECATED) Accept transaction replace-by-fee without requiring replaceability signaling (default: %u)", DEFAULT_MEMPOOL_FULL_RBF), ArgsManager::ALLOW_ANY, OptionsCategory::NODE_RELAY);
     argsman.AddArg("-permitbaremultisig", strprintf("Relay transactions creating non-P2SH multisig outputs (default: %u)", DEFAULT_PERMIT_BAREMULTISIG), ArgsManager::ALLOW_ANY,
                    OptionsCategory::NODE_RELAY);
     argsman.AddArg("-minrelaytxfee=<amt>", strprintf("Fees (in %s/kvB) smaller than this are considered zero fee for relaying, mining and transaction creation (default: %s)",

src/node/mempool_args.cpp

@@ -93,6 +93,9 @@ util::Result<void> ApplyArgsManOptions(const ArgsManager& argsman, const CChainP
     }
 
     mempool_opts.full_rbf = argsman.GetBoolArg("-mempoolfullrbf", mempool_opts.full_rbf);
+    if (!mempool_opts.full_rbf) {
+        LogInfo("Warning: mempoolfullrbf=0 set but deprecated and will be removed in a future release\n");
+    }
 
     mempool_opts.persist_v1_dat = argsman.GetBoolArg("-persistmempoolv1", mempool_opts.persist_v1_dat);