Merge #20661: Only select from addrv2-capable peers for torv3 address relay

37fe80e Only consider addrv2 peers for relay of non-addrv1 addresses (Pieter Wuille)
83f8821 refactor: add IsAddrCompatible() to CNode (Pieter Wuille)

Pull request description:

  When selecting peers to relay an address to, only pick addrv2-capable ones if the address cannot be represented in addr(v1).

  Without this I expect that propagation of torv3 addresses over the cleartext network will be very hard for a while.

ACKs for top commit:
  jonatack:
    ACK 37fe80e
  vasild:
    ACK 37fe80e

Tree-SHA512: 18a854ea43ad473cf89b9c5193b524109d7af75c26f7aa7e26cd72ad0db52f19c8001d566c607a7e6772bc314f770f09b6c3e07282d110c5daea193edc592cd2

Author: laanwj

src/net.h

@@ -1177,18 +1177,23 @@ class CNode
         m_addr_known->insert(_addr.GetKey());
     }
 
-    void PushAddress(const CAddress& _addr, FastRandomContext &insecure_rand)
+    /**
+     * Whether the peer supports the address. For example, a peer that does not
+     * implement BIP155 cannot receive Tor v3 addresses because it requires
+     * ADDRv2 (BIP155) encoding.
+     */
+    bool IsAddrCompatible(const CAddress& addr) const
     {
-        // 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();
+        return m_wants_addrv2 || addr.IsAddrV1Compatible();
+    }
 
+    void PushAddress(const CAddress& _addr, FastRandomContext &insecure_rand)
+    {
         // 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()) && addr_format_supported) {
+        if (_addr.IsValid() && !m_addr_known->contains(_addr.GetKey()) && IsAddrCompatible(_addr)) {
             if (vAddrToSend.size() >= MAX_ADDR_TO_SEND) {
                 vAddrToSend[insecure_rand.randrange(vAddrToSend.size())] = _addr;
             } else {

src/net_processing.cpp

@@ -1443,8 +1443,8 @@ static void RelayAddress(const CNode& originator,
     std::array<std::pair<uint64_t, CNode*>,2> best{{{0, nullptr}, {0, nullptr}}};
     assert(nRelayNodes <= best.size());
 
-    auto sortfunc = [&best, &hasher, nRelayNodes, &originator](CNode* pnode) {
-        if (pnode->RelayAddrsWithConn() && pnode != &originator) {
+    auto sortfunc = [&best, &hasher, nRelayNodes, &originator, &addr](CNode* pnode) {
+        if (pnode->RelayAddrsWithConn() && pnode != &originator && pnode->IsAddrCompatible(addr)) {
             uint64_t hashKey = CSipHasher(hasher).Write(pnode->GetId()).Finalize();
             for (unsigned int i = 0; i < nRelayNodes; i++) {
                  if (hashKey > best[i].first) {