net: advertise support for ADDRv2 via new message

Introduce a new message `sendaddrv2` to signal support for ADDRv2.
Send the new message immediately after sending the `VERACK` message.

Add support for receiving and parsing ADDRv2 messages.

Send ADDRv2 messages (instead of ADDR) to a peer if he has
advertised support for it.

Co-authored-by: Carl Dong <contact@carldong.me>

7 files changed, 114 insertions, 11 deletions

diff --git a/src/net.h b/src/net.h
index ca65c1dc19..def30b4778 100644
--- a/src/net.h
+++ b/src/net.h
@@ -868,6 +868,11 @@ 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
@@ -1115,11 +1120,16 @@ 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 {
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index f784a9b754..2b3b4767c5 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -23,6 +23,7 @@
 #include <random.h>
 #include <reverse_iterator.h>
 #include <scheduler.h>
+#include <streams.h>
 #include <tinyformat.h>
 #include <txmempool.h>
 #include <util/check.h> // For NDEBUG compile time check
@@ -2408,11 +2409,16 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
         pfrom.SetCommonVersion(greatest_common_version);
         pfrom.nVersion = nVersion;
 
+        const CNetMsgMaker msg_maker(greatest_common_version);
+
         if (greatest_common_version >= WTXID_RELAY_VERSION) {
-            m_connman.PushMessage(&pfrom, CNetMsgMaker(greatest_common_version).Make(NetMsgType::WTXIDRELAY));
+            m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::WTXIDRELAY));
         }
 
-        m_connman.PushMessage(&pfrom, CNetMsgMaker(greatest_common_version).Make(NetMsgType::VERACK));
+        m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::VERACK));
+
+        // Signal ADDRv2 support (BIP155).
+        m_connman.PushMessage(&pfrom, msg_maker.Make(NetMsgType::SENDADDRV2));
 
         pfrom.nServices = nServices;
         pfrom.SetAddrLocal(addrMe);
@@ -2582,16 +2588,25 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
         return;
     }
 
-    if (msg_type == NetMsgType::ADDR) {
+    if (msg_type == NetMsgType::ADDR || msg_type == NetMsgType::ADDRV2) {
+        int stream_version = vRecv.GetVersion();
+        if (msg_type == NetMsgType::ADDRV2) {
+            // Add ADDRV2_FORMAT to the version so that the CNetAddr and CAddress
+            // unserialize methods know that an address in v2 format is coming.
+            stream_version |= ADDRV2_FORMAT;
+        }
+
+        OverrideStream<CDataStream> s(&vRecv, vRecv.GetType(), stream_version);
         std::vector<CAddress> vAddr;
-        vRecv >> vAddr;
+
+        s >> vAddr;
 
         if (!pfrom.RelayAddrsWithConn()) {
             return;
         }
         if (vAddr.size() > MAX_ADDR_TO_SEND)
         {
-            Misbehaving(pfrom.GetId(), 20, strprintf("addr message size = %u", vAddr.size()));
+            Misbehaving(pfrom.GetId(), 20, strprintf("%s message size = %u", msg_type, vAddr.size()));
             return;
         }
 
@@ -2635,6 +2650,11 @@ void PeerManager::ProcessMessage(CNode& pfrom, const std::string& msg_type, CDat
         return;
     }
 
+    if (msg_type == NetMsgType::SENDADDRV2) {
+        pfrom.m_wants_addrv2 = true;
+        return;
+    }
+
     if (msg_type == NetMsgType::SENDHEADERS) {
         LOCK(cs_main);
         State(pfrom.GetId())->fPreferHeaders = true;
@@ -4095,6 +4115,17 @@ bool PeerManager::SendMessages(CNode* pto)
             std::vector<CAddress> vAddr;
             vAddr.reserve(pto->vAddrToSend.size());
             assert(pto->m_addr_known);
+
+            const char* msg_type;
+            int make_flags;
+            if (pto->m_wants_addrv2) {
+                msg_type = NetMsgType::ADDRV2;
+                make_flags = ADDRV2_FORMAT;
+            } else {
+                msg_type = NetMsgType::ADDR;
+                make_flags = 0;
+            }
+
             for (const CAddress& addr : pto->vAddrToSend)
             {
                 if (!pto->m_addr_known->contains(addr.GetKey()))
@@ -4104,14 +4135,14 @@ bool PeerManager::SendMessages(CNode* pto)
                     // receiver rejects addr messages larger than MAX_ADDR_TO_SEND
                     if (vAddr.size() >= MAX_ADDR_TO_SEND)
                     {
-                        m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
+                        m_connman.PushMessage(pto, msgMaker.Make(make_flags, msg_type, vAddr));
                         vAddr.clear();
                     }
                 }
             }
             pto->vAddrToSend.clear();
             if (!vAddr.empty())
-                m_connman.PushMessage(pto, msgMaker.Make(NetMsgType::ADDR, vAddr));
+                m_connman.PushMessage(pto, msgMaker.Make(make_flags, msg_type, vAddr));
             // we only send the big addr message once
             if (pto->vAddrToSend.capacity() > 40)
                 pto->vAddrToSend.shrink_to_fit();
diff --git a/src/netaddress.cpp b/src/netaddress.cpp
index 08714dc2ec..eece0190b5 100644
--- a/src/netaddress.cpp
+++ b/src/netaddress.cpp
@@ -474,6 +474,26 @@ bool CNetAddr::IsInternal() const
    return m_net == NET_INTERNAL;
 }
 
+bool CNetAddr::IsAddrV1Compatible() const
+{
+    switch (m_net) {
+    case NET_IPV4:
+    case NET_IPV6:
+    case NET_INTERNAL:
+        return true;
+    case NET_ONION:
+        return m_addr.size() == ADDR_TORV2_SIZE;
+    case NET_I2P:
+    case NET_CJDNS:
+        return false;
+    case NET_UNROUTABLE: // m_net is never and should not be set to NET_UNROUTABLE
+    case NET_MAX:        // m_net is never and should not be set to NET_MAX
+        assert(false);
+    } // no default case, so the compiler can warn about missing cases
+
+    assert(false);
+}
+
 enum Network CNetAddr::GetNetwork() const
 {
     if (IsInternal())
@@ -744,9 +764,12 @@ std::vector<unsigned char> CNetAddr::GetGroup(const std::vector<bool> &asmap) co
 
 std::vector<unsigned char> CNetAddr::GetAddrBytes() const
 {
-    uint8_t serialized[V1_SERIALIZATION_SIZE];
-    SerializeV1Array(serialized);
-    return {std::begin(serialized), std::end(serialized)};
+    if (IsAddrV1Compatible()) {
+        uint8_t serialized[V1_SERIALIZATION_SIZE];
+        SerializeV1Array(serialized);
+        return {std::begin(serialized), std::end(serialized)};
+    }
+    return std::vector<unsigned char>(m_addr.begin(), m_addr.end());
 }
 
 uint64_t CNetAddr::GetHash() const
diff --git a/src/netaddress.h b/src/netaddress.h
index 59f1b87ad3..a0992e70c4 100644
--- a/src/netaddress.h
+++ b/src/netaddress.h
@@ -173,6 +173,12 @@ class CNetAddr
         bool IsRoutable() const;
         bool IsInternal() const;
         bool IsValid() const;
+
+        /**
+         * Check if the current object can be serialized in pre-ADDRv2/BIP155 format.
+         */
+        bool IsAddrV1Compatible() const;
+
         enum Network GetNetwork() const;
         std::string ToString() const;
         std::string ToStringIP() const;
diff --git a/src/protocol.cpp b/src/protocol.cpp
index 84b6e96aee..dc8f795a0c 100644
--- a/src/protocol.cpp
+++ b/src/protocol.cpp
@@ -14,6 +14,8 @@ namespace NetMsgType {
 const char *VERSION="version";
 const char *VERACK="verack";
 const char *ADDR="addr";
+const char *ADDRV2="addrv2";
+const char *SENDADDRV2="sendaddrv2";
 const char *INV="inv";
 const char *GETDATA="getdata";
 const char *MERKLEBLOCK="merkleblock";
@@ -52,6 +54,8 @@ const static std::string allNetMessageTypes[] = {
     NetMsgType::VERSION,
     NetMsgType::VERACK,
     NetMsgType::ADDR,
+    NetMsgType::ADDRV2,
+    NetMsgType::SENDADDRV2,
     NetMsgType::INV,
     NetMsgType::GETDATA,
     NetMsgType::MERKLEBLOCK,
diff --git a/src/protocol.h b/src/protocol.h
index e2d3602792..309fac621c 100644
--- a/src/protocol.h
+++ b/src/protocol.h
@@ -77,6 +77,18 @@ extern const char* VERACK;
  */
 extern const char* ADDR;
 /**
+ * The addrv2 message relays connection information for peers on the network just
+ * like the addr message, but is extended to allow gossiping of longer node
+ * addresses (see BIP155).
+ */
+extern const char *ADDRV2;
+/**
+ * The sendaddrv2 message signals support for receiving ADDRV2 messages (BIP155).
+ * It also implies that its sender can encode as ADDRV2 and would send ADDRV2
+ * instead of ADDR to a peer that has signaled ADDRV2 support by sending SENDADDRV2.
+ */
+extern const char *SENDADDRV2;
+/**
  * The inv message (inventory message) transmits one or more inventories of
  * objects known to the transmitting peer.
  */
diff --git a/src/test/net_tests.cpp b/src/test/net_tests.cpp
index 261396cd0c..fe03c1ece4 100644
--- a/src/test/net_tests.cpp
+++ b/src/test/net_tests.cpp
@@ -212,6 +212,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsIPv4());
 
     BOOST_CHECK(addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "0.0.0.0");
 
     // IPv4, INADDR_NONE
@@ -220,6 +221,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsIPv4());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "255.255.255.255");
 
     // IPv4, casual
@@ -228,6 +230,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsIPv4());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "12.34.56.78");
 
     // IPv6, in6addr_any
@@ -236,6 +239,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsIPv6());
 
     BOOST_CHECK(addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "::");
 
     // IPv6, casual
@@ -244,6 +248,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsIPv6());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "1122:3344:5566:7788:9900:aabb:ccdd:eeff");
 
     // TORv2
@@ -252,6 +257,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsTor());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "6hzph5hv6337r6p2.onion");
 
     // TORv3
@@ -261,6 +267,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsTor());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(!addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), torv3_addr);
 
     // TORv3, broken, with wrong checksum
@@ -285,6 +292,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_basic)
     BOOST_REQUIRE(addr.IsInternal());
 
     BOOST_CHECK(!addr.IsBindAny());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "esffpvrt3wpeaygy.internal");
 
     // Totally bogus
@@ -379,6 +387,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsIPv4());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "1.2.3.4");
     BOOST_REQUIRE(s.empty());
 
@@ -415,6 +424,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsIPv6());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "102:304:506:708:90a:b0c:d0e:f10");
     BOOST_REQUIRE(s.empty());
 
@@ -426,6 +436,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
                                               // sha256(name)[0:10]
     s >> addr;
     BOOST_CHECK(addr.IsInternal());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "zklycewkdo64v6wc.internal");
     BOOST_REQUIRE(s.empty());
 
@@ -461,6 +472,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsTor());
+    BOOST_CHECK(addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "6hzph5hv6337r6p2.onion");
     BOOST_REQUIRE(s.empty());
 
@@ -482,6 +494,7 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
     s >> addr;
     BOOST_CHECK(addr.IsValid());
     BOOST_CHECK(addr.IsTor());
+    BOOST_CHECK(!addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(),
                       "pg6mmjiyjmcrsslvykfwnntlaru7p5svn6y2ymmju6nubxndf4pscryd.onion");
     BOOST_REQUIRE(s.empty());
@@ -503,6 +516,8 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
                            "f98232ae42d4b6fd2fa81952dfe36a87"));
     s >> addr;
     BOOST_CHECK(addr.IsValid());
+    BOOST_CHECK(addr.IsI2P());
+    BOOST_CHECK(!addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(),
                       "ukeu3k5oycgaauneqgtnvselmt4yemvoilkln7jpvamvfx7dnkdq.b32.i2p");
     BOOST_REQUIRE(s.empty());
@@ -524,6 +539,8 @@ BOOST_AUTO_TEST_CASE(cnetaddr_unserialize_v2)
                            ));
     s >> addr;
     BOOST_CHECK(addr.IsValid());
+    BOOST_CHECK(addr.IsCJDNS());
+    BOOST_CHECK(!addr.IsAddrV1Compatible());
     BOOST_CHECK_EQUAL(addr.ToString(), "fc00:1:2:3:4:5:6:7");
     BOOST_REQUIRE(s.empty());