addrman: reset I2P ports to 0 when loading from disk

This is a temporary change to convert I2P addresses that have propagated
with port 8333 to ones with port 0.

It would cause a problem some day if indeed some bitcoin software is
listening on port 8333 only and rejects connections to port 0 and we are
still using SAM 3.1 which only supports port 0. In this case we would
replace 8333 with 0 and try to connect to such nodes.

This commit should be included in 22.0 and be reverted before 23.0 is
released.

3 files changed, 225 insertions, 0 deletions

diff --git a/src/addrman.cpp b/src/addrman.cpp
index 8192b4eba6..389d106164 100644
--- a/src/addrman.cpp
+++ b/src/addrman.cpp
@@ -6,6 +6,7 @@
 #include <addrman.h>
 
 #include <hash.h>
+#include <i2p.h>
 #include <logging.h>
 #include <netaddress.h>
 #include <serialize.h>
@@ -731,3 +732,100 @@ std::vector<bool> CAddrMan::DecodeAsmap(fs::path path)
     }
     return bits;
 }
+
+void CAddrMan::ResetI2PPorts()
+{
+    for (int bucket = 0; bucket < ADDRMAN_NEW_BUCKET_COUNT; ++bucket) {
+        for (int i = 0; i < ADDRMAN_BUCKET_SIZE; ++i) {
+            const auto id = vvNew[bucket][i];
+            if (id == -1) {
+                continue;
+            }
+            auto it = mapInfo.find(id);
+            if (it == mapInfo.end()) {
+                return;
+            }
+            auto& addr_info = it->second;
+            if (!addr_info.IsI2P() || addr_info.GetPort() == I2P_SAM31_PORT) {
+                continue;
+            }
+
+            auto addr_info_newport = addr_info;
+            // The below changes addr_info_newport.GetKey(), which is used in finding a
+            // bucket and a position within that bucket. So a re-bucketing may be necessary.
+            addr_info_newport.port = I2P_SAM31_PORT;
+
+            // Reposition entries of vvNew within the same bucket because we don't know the source
+            // address which led to the decision to store the entry in vvNew[bucket] so we can't
+            // re-evaluate that decision, but even if we could, CAddrInfo::GetNewBucket() does not
+            // use CAddrInfo::GetKey() so it would end up in the same bucket as before the port
+            // change.
+            const auto i_target = addr_info_newport.GetBucketPosition(nKey, true, bucket);
+
+            if (i_target == i) { // No need to re-position.
+                addr_info = addr_info_newport;
+                continue;
+            }
+
+            // Reposition from i to i_target, removing the entry from i_target (if any).
+            ClearNew(bucket, i_target);
+            vvNew[bucket][i_target] = id;
+            vvNew[bucket][i] = -1;
+            addr_info = addr_info_newport;
+        }
+    }
+
+    for (int bucket = 0; bucket < ADDRMAN_TRIED_BUCKET_COUNT; ++bucket) {
+        for (int i = 0; i < ADDRMAN_BUCKET_SIZE; ++i) {
+            const auto id = vvTried[bucket][i];
+            if (id == -1) {
+                continue;
+            }
+            auto it = mapInfo.find(id);
+            if (it == mapInfo.end()) {
+                return;
+            }
+            auto& addr_info = it->second;
+            if (!addr_info.IsI2P() || addr_info.GetPort() == I2P_SAM31_PORT) {
+                continue;
+            }
+
+            auto addr_info_newport = addr_info;
+            // The below changes addr_info_newport.GetKey(), which is used in finding a
+            // bucket and a position within that bucket. So a re-bucketing may be necessary.
+            addr_info_newport.port = I2P_SAM31_PORT;
+
+            const auto bucket_target = addr_info_newport.GetTriedBucket(nKey, m_asmap);
+            const auto i_target = addr_info_newport.GetBucketPosition(nKey, false, bucket_target);
+
+            if (bucket_target == bucket && i_target == i) { // No need to re-position.
+                addr_info = addr_info_newport;
+                continue;
+            }
+
+            // Reposition from (bucket, i) to (bucket_target, i_target). If the latter is
+            // occupied, then move the entry from there to vvNew.
+
+            const auto old_target_id = vvTried[bucket_target][i_target];
+            if (old_target_id != -1) {
+                CAddrInfo& old_target_info = mapInfo[old_target_id];
+
+                old_target_info.fInTried = false;
+                vvTried[bucket_target][i_target] = -1;
+                --nTried;
+
+                const auto new_bucket = old_target_info.GetNewBucket(nKey, m_asmap);
+                const auto new_bucket_i = old_target_info.GetBucketPosition(nKey, true, new_bucket);
+                ClearNew(new_bucket, new_bucket_i);
+
+                old_target_info.nRefCount = 1;
+                vvNew[new_bucket][new_bucket_i] = old_target_id;
+                ++nNew;
+            }
+
+            vvTried[bucket_target][i_target] = id;
+            vvTried[bucket][i] = -1;
+            addr_info = addr_info_newport;
+        }
+    }
+}
diff --git a/src/addrman.h b/src/addrman.h
index c2f425f2fa..2a5c6c06b4 100644
--- a/src/addrman.h
+++ b/src/addrman.h
@@ -452,6 +452,8 @@ public:
 
         RemoveInvalid();
 
+        ResetI2PPorts();
+
         Check();
     }
 
@@ -767,6 +769,14 @@ private:
     //! Remove invalid addresses.
     void RemoveInvalid() EXCLUSIVE_LOCKS_REQUIRED(cs);
 
+    /**
+     * Reset the ports of I2P peers to 0.
+     * This is needed as a temporary measure because now we enforce port 0 and
+     * only connect to I2P hosts if the port is 0, but in the early days some
+     * I2P addresses with port 8333 were rumoured and persisted into addrmans.
+     */
+    void ResetI2PPorts() EXCLUSIVE_LOCKS_REQUIRED(cs);
+
     friend class CAddrManTest;
 };
 
diff --git a/src/test/addrman_tests.cpp b/src/test/addrman_tests.cpp
index 1103292c1a..f2eed956cd 100644
--- a/src/test/addrman_tests.cpp
+++ b/src/test/addrman_tests.cpp
@@ -2,6 +2,7 @@
 // Distributed under the MIT software license, see the accompanying
 // file COPYING or http://www.opensource.org/licenses/mit-license.php.
 #include <addrman.h>
+#include <i2p.h>
 #include <test/data/asmap.raw.h>
 #include <test/util/setup_common.h>
 #include <util/asmap.h>
@@ -966,5 +967,121 @@ BOOST_AUTO_TEST_CASE(addrman_evictionworks)
     BOOST_CHECK(addrman.SelectTriedCollision().ToString() == "[::]:0");
 }
 
+BOOST_AUTO_TEST_CASE(reset_i2p_ports)
+{
+    CAddrManTest addrman1;
+    CAddrManTest addrman2;
+    const uint32_t good_time{static_cast<uint32_t>(GetAdjustedTime())};
+    constexpr uint16_t port = 8333;
+
+    // Has its port changed, will be re-positioned within the same bucket in vvNew.
+    const CAddress i2p_new1{
+        ResolveService("72l3ucjkuscrbiiepoehuwqgknyzgo7zuix5ty4puwrkyhtmnsga.b32.i2p", port),
+        NODE_NONE,
+        good_time};
+
+    // Has its port changed, will not be re-positioned in vvNew because ports 0 and 10075 result in
+    // the same bucket position.
+    const CAddress i2p_new2{
+        ResolveService("gehtac45oaghz54ypyopim64mql7oad2bqclla74l6tfeolzmodq.b32.i2p", 10075),
+        NODE_NONE,
+        good_time};
+
+    // Remains unchanged, port is already as it should be.
+    const CAddress i2p_new3{
+        ResolveService("c4gfnttsuwqomiygupdqqqyy5y5emnk5c73hrfvatri67prd7vyq.b32.i2p",
+                       I2P_SAM31_PORT),
+        NODE_NONE,
+        good_time};
+
+    // Has its port changed, re-positioning in vvNew will cause i2p_new3 to be evicted.
+    const CAddress i2p_new4{
+        ResolveService("c4cbbkn46qxftwja53pxiykntegfyfjqtnzbm6iv6r5mungmqgmq.b32.i2p", port),
+        NODE_NONE,
+        good_time};
+
+    // Remains unchanged.
+    const CAddress ipv4_new{ResolveService("1.2.3.4", port), NODE_NONE, good_time};
+
+    // Has its port changed, will be re-positioned in vvTried.
+    const CAddress i2p_tried1{
+        ResolveService("h3r6bkn46qxftwja53pxiykntegfyfjqtnzbm6iv6r5mungmqgmq.b32.i2p", port),
+        NODE_NONE,
+        good_time};
+
+    // Has its port changed, will not be re-positioned in vvTried because ports 0 and 10537
+    // result in the same position (bucket, i).
+    const CAddress i2p_tried2{
+        ResolveService("pjs7or2ctvteeo5tu4bwyrtydeuhqhvdprtujn4daxr75jpebjxa.b32.i2p", 10537),
+        NODE_NONE,
+        good_time};
+
+    // Remains unchanged, port is already as it should be.
+    const CAddress i2p_tried3{
+        ResolveService("hnbbyjpxx54623l555sta7pocy3se4sdgmuebi5k6reesz5rjp6q.b32.i2p",
+                       I2P_SAM31_PORT),
+        NODE_NONE,
+        good_time};
+
+    // Has its port changed, re-positioning in vvTried will cause i2p_tried3 to be moved to vvNew.
+    const CAddress i2p_tried4{
+        ResolveService("hna37nqr3ahkqv62cuqfwgtneekvvpnuc4i4f6yo7tpoqjswvcwa.b32.i2p", port),
+        NODE_NONE,
+        good_time};
+
+    // Remains unchanged.
+    const CAddress ipv4_tried{ResolveService("2.3.4.5", port), NODE_NONE, good_time};
+
+    const CNetAddr source;
+
+    CDataStream stream(SER_NETWORK, PROTOCOL_VERSION);
+
+    addrman1.Add(i2p_new1, source);
+    addrman1.Add(i2p_new2, source);
+    addrman1.Add(i2p_new3, source);
+    addrman1.Add(i2p_new4, source);
+    addrman1.Add(ipv4_new, source);
+
+    addrman1.Add(i2p_tried1, source);
+    addrman1.Good(i2p_tried1);
+    addrman1.Add(i2p_tried2, source);
+    addrman1.Good(i2p_tried2);
+    addrman1.Add(i2p_tried3, source);
+    addrman1.Good(i2p_tried3);
+    addrman1.Add(i2p_tried4, source);
+    addrman1.Good(i2p_tried4);
+    addrman1.Add(ipv4_tried, source);
+    addrman1.Good(ipv4_tried);
+
+    stream << addrman1;
+    stream >> addrman2;
+
+    const size_t max_addresses{0};
+    const size_t max_pct{0};
+
+    auto addresses = addrman2.GetAddr(max_addresses, max_pct, NET_I2P);
+    BOOST_REQUIRE_EQUAL(addresses.size(), 7UL);
+    std::sort(addresses.begin(), addresses.end()); // Just some deterministic order.
+    BOOST_CHECK_EQUAL(addresses[0].ToStringIP(), i2p_new4.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[0].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[1].ToStringIP(), i2p_new2.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[1].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[2].ToStringIP(), i2p_tried4.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[2].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[3].ToStringIP(), i2p_tried3.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[3].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[4].ToStringIP(), i2p_tried1.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[4].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[5].ToStringIP(), i2p_tried2.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[5].GetPort(), I2P_SAM31_PORT);
+    BOOST_CHECK_EQUAL(addresses[6].ToStringIP(), i2p_new1.ToStringIP());
+    BOOST_CHECK_EQUAL(addresses[6].GetPort(), I2P_SAM31_PORT);
+
+    addresses = addrman2.GetAddr(max_addresses, max_pct, NET_IPV4);
+    BOOST_REQUIRE_EQUAL(addresses.size(), 2UL);
+    std::sort(addresses.begin(), addresses.end()); // Just some deterministic order.
+    BOOST_CHECK_EQUAL(addresses[0].ToStringIPPort(), ipv4_new.ToStringIPPort());
+    BOOST_CHECK_EQUAL(addresses[1].ToStringIPPort(), ipv4_tried.ToStringIPPort());
+}
 
 BOOST_AUTO_TEST_SUITE_END()