Merge #19954: Complete the BIP155 implementation and upgrade to TORv3

dcf0cb477699d11afd0ff37c8bfb2b1b4f7f1ee5 tor: make a TORv3 hidden service instead of TORv2 (Vasil Dimov)
353a3fdaad055eea42a0baf7326bdd591f541170 net: advertise support for ADDRv2 via new message (Vasil Dimov)
201a4596d92d640d5eb7e76cc8d959228fa09dbb net: CAddress & CAddrMan: (un)serialize as ADDRv2 (Vasil Dimov)
1d3ec2a1fda7446323786a52da1fd109c01aa6fb Support bypassing range check in ReadCompactSize (Pieter Wuille)

Pull request description:

  This PR contains the two remaining commits from #19031 to complete the [BIP155](https://github.com/bitcoin/bips/blob/master/bip-0155.mediawiki) implementation:

  `net: CAddress & CAddrMan: (un)serialize as ADDRv2`
  `net: advertise support for ADDRv2 via new message`

  plus one more commit:

  `tor: make a TORv3 hidden service instead of TORv2`

ACKs for top commit:
  jonatack:
    re-ACK dcf0cb477699d11afd0ff37c8bfb2b1b4f7f1ee5 per `git diff 9b56a68 dcf0cb4` only change since last review is an update to the release notes which partially picked up the suggested text. Running a node on this branch and addnode-ing to 6 other Tor v3 nodes, I see "addrv2" and "sendaddrv2" messages in getpeerinfo in both the "bytesrecv_per_msg" and "bytessent_per_msg" JSON objects.
  sipa:
    ACK dcf0cb477699d11afd0ff37c8bfb2b1b4f7f1ee5
  hebasto:
    re-ACK dcf0cb477699d11afd0ff37c8bfb2b1b4f7f1ee5, the node works flawlessly in all of the modes: Tor-only, clearnet-only, mixed.
  laanwj:
    Edit: I have to retract this ACK for now, I'm having some problems with this PR on a FreeBSD node. It drops all outgoing connections with this dcf0cb477699d11afd0ff37c8bfb2b1b4f7f1ee5 merged on master (12a1c3ad1a43634d2a98717e49e3f02c4acea2fe).
  ariard:
    Code Review ACK dcf0cb4

Tree-SHA512: 28d4d0d817b8664d2f4b18c0e0f31579b2f0f2d23310ed213f1f436a4242afea14dfbf99e07e15889bc5c5c71ad50056797e9307ff8a90e96704f588a6171308

1 files changed, 19 insertions, 0 deletions

diff --git a/doc/release-notes.md b/doc/release-notes.md
index ba5c3c2c1b..aef021a29d 100644
--- a/doc/release-notes.md
+++ b/doc/release-notes.md
@@ -60,6 +60,14 @@ From Bitcoin Core 0.20.0 onwards, macOS versions earlier than 10.12 are no
 longer supported. Additionally, Bitcoin Core does not yet change appearance
 when macOS "dark mode" is activated.
 
+The node's known peers are persisted to disk in a file called `peers.dat`. The
+format of this file has been changed in a backwards-incompatible way in order to
+accommodate the storage of Tor v3 and other BIP155 addresses. This means that if
+the file is modified by 0.21.0 or newer then older versions will not be able to
+read it. Those old versions, in the event of a downgrade, will log an error
+message that deserialization has failed and will continue normal operation
+as if the file was missing, creating a new empty one. (#19954)
+
 Notable changes
 ===============
 
@@ -74,6 +82,17 @@ P2P and network changes
   node using P2P relay. This version reduces the initial broadcast guarantees
   for wallet transactions submitted via P2P to a node running the wallet. (#18038)
 
+- The Tor onion service that is automatically created by setting the
+  `-listenonion` configuration parameter will now be created as a Tor v3 service
+  instead of Tor v2. The private key that was used for Tor v2 (if any) will be
+  left untouched in the `onion_private_key` file in the data directory (see
+  `-datadir`) and can be removed if not needed. Bitcoin Core will no longer
+  attempt to read it. The private key for the Tor v3 service will be saved in a
+  file named `onion_v3_private_key`. To use the deprecated Tor v2 service (not
+  recommended), then `onion_private_key` can be copied over
+  `onion_v3_private_key`, e.g.
+  `cp -f onion_private_key onion_v3_private_key`. (#19954)
+
 Updated RPCs
 ------------