Merge bitcoin/bitcoin#27071: Handle CJDNS from LookupSubNet()

0e6f6ebc064c5fb425fc3699efe760ec6cd4b6af net: remove unused CConnman::FindNode(const CSubNet&) (Vasil Dimov)
9482cb780fe04c1f1d9050edd1b8e549e52c86ce netbase: possibly change the result of LookupSubNet() to CJDNS (Vasil Dimov)
53afa68026ffa1313ae4aba3664de7791d23b1c8 net: move MaybeFlipIPv6toCJDNS() from net to netbase (Vasil Dimov)
6e308651c441cbf8763c67cc099c538c333c2872 net: move IsReachable() code to netbase and encapsulate it (Vasil Dimov)
c42ded3d9bda8b273780a4a81490bbf1b9e9c261 fuzz: ConsumeNetAddr(): avoid IPv6 addresses that look like CJDNS (Vasil Dimov)
64d6f77907afd461d9b14ee10ab32335f4454734 net: put CJDNS prefix byte in a constant (Vasil Dimov)

Pull request description:

  `LookupSubNet()` would treat addresses that start with `fc` as IPv6 even if `-cjdnsreachable` is set. This creates the following problems where it is called:

  * `NetWhitelistPermissions::TryParse()`: otherwise `-whitelist=` fails to white list CJDNS addresses: when a CJDNS peer connects to us, it will be matched against IPv6 `fc...` subnet and the match will never succeed.

  * `BanMapFromJson()`: CJDNS bans are stored as just IPv6 addresses in `banlist.json`. Upon reading from disk they have to be converted back to CJDNS, otherwise, after restart, a ban entry like (`fc00::1`, IPv6) would not match a peer (`fc00::1`, CJDNS).

  * `RPCConsole::unbanSelectedNode()`: in the GUI the ban entries go through `CSubNet::ToString()` and back via `LookupSubNet()`. Then it must match whatever is stored in `BanMan`, otherwise it is impossible to unban via the GUI.

  These were uncovered by https://github.com/bitcoin/bitcoin/pull/26859.

  Thus, flip the result of `LookupSubNet()` to CJDNS if the network base address starts with `fc` and `-cjdnsreachable` is set. Since subnetting/masking does not make sense for CJDNS (the address is "random" bytes, like Tor and I2P, there is no hierarchy) treat `fc.../mask` as an invalid `CSubNet`.

  To achieve that, `MaybeFlipIPv6toCJDNS()` has to be moved from `net` to `netbase` and thus also `IsReachable()`. In the process of moving `IsReachable()`, `SetReachable()` and `vfLimited[]` encapsulate those in a class.

ACKs for top commit:
  jonatack:
    Code review ACK 0e6f6ebc064c5fb425fc3699efe760ec6cd4b6af
  achow101:
    ACK 0e6f6ebc064c5fb425fc3699efe760ec6cd4b6af
  mzumsande:
    re-ACK 0e6f6ebc064c5fb425fc3699efe760ec6cd4b6af

Tree-SHA512: 4767a60dc882916de4c8b110ce8de208ff3f58daaa0b560e6547d72e604d07c4157e72cf98b237228310fc05c0a3922f446674492e2ba02e990a272d288bd566

1 files changed, 10 insertions, 16 deletions

diff --git a/src/init.cpp b/src/init.cpp
index 22100dfbf9..42331d37e8 100644
--- a/src/init.cpp
+++ b/src/init.cpp
@@ -1314,30 +1314,24 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     }
 
     if (args.IsArgSet("-onlynet")) {
-        std::set<enum Network> nets;
+        g_reachable_nets.RemoveAll();
         for (const std::string& snet : args.GetArgs("-onlynet")) {
             enum Network net = ParseNetwork(snet);
             if (net == NET_UNROUTABLE)
                 return InitError(strprintf(_("Unknown network specified in -onlynet: '%s'"), snet));
-            nets.insert(net);
-        }
-        for (int n = 0; n < NET_MAX; n++) {
-            enum Network net = (enum Network)n;
-            assert(IsReachable(net));
-            if (!nets.count(net))
-                SetReachable(net, false);
+            g_reachable_nets.Add(net);
         }
     }
 
     if (!args.IsArgSet("-cjdnsreachable")) {
-        if (args.IsArgSet("-onlynet") && IsReachable(NET_CJDNS)) {
+        if (args.IsArgSet("-onlynet") && g_reachable_nets.Contains(NET_CJDNS)) {
             return InitError(
                 _("Outbound connections restricted to CJDNS (-onlynet=cjdns) but "
                   "-cjdnsreachable is not provided"));
         }
-        SetReachable(NET_CJDNS, false);
+        g_reachable_nets.Remove(NET_CJDNS);
     }
-    // Now IsReachable(NET_CJDNS) is true if:
+    // Now g_reachable_nets.Contains(NET_CJDNS) is true if:
     // 1. -cjdnsreachable is given and
     // 2.1. -onlynet is not given or
     // 2.2. -onlynet=cjdns is given
@@ -1345,7 +1339,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
     // Requesting DNS seeds entails connecting to IPv4/IPv6, which -onlynet options may prohibit:
     // If -dnsseed=1 is explicitly specified, abort. If it's left unspecified by the user, we skip
     // the DNS seeds by adjusting -dnsseed in InitParameterInteraction.
-    if (args.GetBoolArg("-dnsseed") == true && !IsReachable(NET_IPV4) && !IsReachable(NET_IPV6)) {
+    if (args.GetBoolArg("-dnsseed") == true && !g_reachable_nets.Contains(NET_IPV4) && !g_reachable_nets.Contains(NET_IPV6)) {
         return InitError(strprintf(_("Incompatible options: -dnsseed=1 was explicitly specified, but -onlynet forbids connections to IPv4/IPv6")));
     };
 
@@ -1375,7 +1369,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         onion_proxy = addrProxy;
     }
 
-    const bool onlynet_used_with_onion{args.IsArgSet("-onlynet") && IsReachable(NET_ONION)};
+    const bool onlynet_used_with_onion{args.IsArgSet("-onlynet") && g_reachable_nets.Contains(NET_ONION)};
 
     // -onion can be used to set only a proxy for .onion, or override normal proxy for .onion addresses
     // -noonion (or -onion=0) disables connecting to .onion entirely
@@ -1410,7 +1404,7 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
                   "reaching the Tor network is not provided: none of -proxy, -onion or "
                   "-listenonion is given"));
         }
-        SetReachable(NET_ONION, false);
+        g_reachable_nets.Remove(NET_ONION);
     }
 
     for (const std::string& strAddr : args.GetArgs("-externalip")) {
@@ -1885,12 +1879,12 @@ bool AppInitMain(NodeContext& node, interfaces::BlockAndHeaderTipInfo* tip_info)
         }
         SetProxy(NET_I2P, Proxy{addr.value()});
     } else {
-        if (args.IsArgSet("-onlynet") && IsReachable(NET_I2P)) {
+        if (args.IsArgSet("-onlynet") && g_reachable_nets.Contains(NET_I2P)) {
             return InitError(
                 _("Outbound connections restricted to i2p (-onlynet=i2p) but "
                   "-i2psam is not provided"));
         }
-        SetReachable(NET_I2P, false);
+        g_reachable_nets.Remove(NET_I2P);
     }
 
     connOptions.m_i2p_accept_incoming = args.GetBoolArg("-i2pacceptincoming", DEFAULT_I2P_ACCEPT_INCOMING);