Merge #20119: BIP155 follow-ups

56f9dba015c592b8925795012e3061a710070a27 Only relay IPv4, IPv6, Tor addresses (Pieter Wuille)
79f3d9b932bf62b90995bce1cf4b0b1f0152d26d Mention BIP155 in doc/bips.md (Pieter Wuille)

Pull request description:

  This:
  * Documents BIP155 support in doc/bips.md
  * Restricts addrv2 relay to IPv4, IPv6, and Tor addresses. Relaying addresses in ranges that no network software has support for seems like a gratuitous spam vector.

ACKs for top commit:
  jonatack:
    ACK 56f9dba015c592b8925795012e3061a710070a27
  naumenkogs:
    ACK 56f9dba
  hebasto:
    ACK 56f9dba015c592b8925795012e3061a710070a27, verified both links.

Tree-SHA512: f0a2072b3d84a05cdbc7b961c18d7322a2e7260517f5306599ff52d8c728f9167de0a59a6d66cb95d84d69f3028680ce8bd05dab0db8c4f97938a287e5ce9631

doc/bips.md

@@ -1,5 +1,5 @@
 BIPs that are implemented by Bitcoin Core, some of them are relevant for Dash Core, some are just mentioned as a reference.
-Specified versions, PRs are relevant to Bitcoin's core.
+Versions and PRs are relevant to Bitcoin's core if not mentioned other.
 
 * [`BIP 9`](https://github.com/bitcoin/bips/blob/master/bip-0009.mediawiki): The changes allowing multiple soft-forks to be deployed in parallel have been implemented since **v0.12.1**  ([PR #7575](https://github.com/bitcoin/bitcoin/pull/7575))
 * [`BIP 11`](https://github.com/bitcoin/bips/blob/master/bip-0011.mediawiki): Multisig outputs are standard since **v0.6.0** ([PR #669](https://github.com/bitcoin/bitcoin/pull/669)).
@@ -38,7 +38,7 @@ Specified versions, PRs are relevant to Bitcoin's core.
 * [`BIP 147`](https://github.com/bitcoin/bips/blob/master/bip-0147.mediawiki): NULLDUMMY softfork as of **v0.13.1** ([PR 8636](https://github.com/bitcoin/bitcoin/pull/8636) and [PR 8937](https://github.com/bitcoin/bitcoin/pull/8937)), *buried* since **v0.19.0** ([PR #16060](https://github.com/bitcoin/bitcoin/pull/16060)).
 * [`BIP 152`](https://github.com/bitcoin/bips/blob/master/bip-0152.mediawiki): Compact block transfer and related optimizations are used as of **v0.13.0** ([PR 8068](https://github.com/bitcoin/bitcoin/pull/8068)).
 * [`BIP 155`](https://github.com/bitcoin/bips/blob/master/bip-0155.mediawiki): The 'addrv2' and 'sendaddrv2' messages which enable relay of Tor V3 addresses (and other networks) are supported as of **v18.0** ([PR 19954](https://github.com/bitcoin/bitcoin/pull/19954)).
-- [`BIP 158`](https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki): Compact Block Filters for Light Clients can be indexed as of **v18.0** ([PR #14121](https://github.com/bitcoin/bitcoin/pull/14121)).
+* [`BIP 158`](https://github.com/bitcoin/bips/blob/master/bip-0158.mediawiki): Compact Block Filters for Light Clients can be indexed as of **Dash Core v18.0** ([PR dash#4314](https://github.com/dashpay/dash/pull/4314), [PR #14121](https://github.com/bitcoin/bitcoin/pull/14121)).
 * [`BIP 159`](https://github.com/bitcoin/bips/blob/master/bip-0159.mediawiki): The `NODE_NETWORK_LIMITED` service bit is signalled as of **v0.16.0** ([PR 11740](https://github.com/bitcoin/bitcoin/pull/11740)), and such nodes are connected to as of **v0.17.0** ([PR 10387](https://github.com/bitcoin/bitcoin/pull/10387)).
 * [`BIP 174`](https://github.com/bitcoin/bips/blob/master/bip-0174.mediawiki): RPCs to operate on Partially Signed Bitcoin Transactions (PSBT) are present as of **v18.0** ([PR 13557](https://github.com/bitcoin/bitcoin/pull/13557)).
 * [`BIP 339`](https://github.com/bitcoin/bips/blob/master/bip-0339.mediawiki): Relay of transactions by wtxid is supported as of **v0.21.0** ([PR 18044](https://github.com/bitcoin/bitcoin/pull/18044)).

src/net_processing.cpp

@@ -1896,6 +1896,8 @@ void PeerManagerImpl::RelayTransaction(const uint256& txid)
 
 static void RelayAddress(const CAddress& addr, bool fReachable, const CConnman& connman)
 {
+    if (!fReachable && !addr.IsRelayable()) return;
+
     // Relay to a limited number of other nodes
     // Use deterministic randomness to send to the same nodes for 24 hours
     // at a time so the m_addr_knowns of the chosen nodes prevent repeats

src/netaddress.h

@@ -227,6 +227,14 @@ public:
     friend bool operator!=(const CNetAddr& a, const CNetAddr& b) { return !(a == b); }
     friend bool operator<(const CNetAddr& a, const CNetAddr& b);
 
+    /**
+     * Whether this address should be relayed to other peers even if we can't reach it ourselves.
+     */
+    bool IsRelayable() const
+    {
+        return IsIPv4() || IsIPv6() || IsTor();
+    }
+
     /**
      * Serialize to a stream.
      */