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, 11 insertions, 1 deletions

diff --git a/src/net.h b/src/net.h
index 2b99d3bd9d..a72017f768 100644
--- a/src/net.h
+++ b/src/net.h
@@ -867,6 +867,11 @@ public:
     bool m_legacyWhitelisted{false};
     bool fClient{false}; // set by version message
     bool m_limited_node{false}; //after BIP159, set by version message
+    /**
+     * Whether the peer has signaled support for receiving ADDRv2 (BIP155)
+     * messages, implying a preference to receive ADDRv2 instead of ADDR ones.
+     */
+    std::atomic_bool m_wants_addrv2{false};
     std::atomic_bool fSuccessfullyConnected{false};
     // Setting fDisconnect to true will cause the node to be disconnected the
     // next time DisconnectNodes() runs
@@ -1114,11 +1119,16 @@ public:
 
     void PushAddress(const CAddress& _addr, FastRandomContext &insecure_rand)
     {
+        // Whether the peer supports the address in `_addr`. For example,
+        // nodes that do not implement BIP155 cannot receive Tor v3 addresses
+        // because they require ADDRv2 (BIP155) encoding.
+        const bool addr_format_supported = m_wants_addrv2 || _addr.IsAddrV1Compatible();
+
         // Known checking here is only to save space from duplicates.
         // SendMessages will filter it again for knowns that were added
         // after addresses were pushed.
         assert(m_addr_known);
-        if (_addr.IsValid() && !m_addr_known->contains(_addr.GetKey())) {
+        if (_addr.IsValid() && !m_addr_known->contains(_addr.GetKey()) && addr_format_supported) {
             if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
                 vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = _addr;
             } else {