net: switch to dummy internal ip for dns seed source

This addresss the TODO to avoid resolving twice.

Author: theuni

src/chainparams.cpp

@@ -124,12 +124,12 @@ class CMainParams : public CChainParams {
         assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));
 
         // Note that of those with the service bits flag, most only support a subset of possible options
-        vSeeds.push_back(CDNSSeedData("bitcoin.sipa.be", "seed.bitcoin.sipa.be", true)); // Pieter Wuille, only supports x1, x5, x9, and xd
-        vSeeds.push_back(CDNSSeedData("bluematt.me", "dnsseed.bluematt.me", true)); // Matt Corallo, only supports x9
-        vSeeds.push_back(CDNSSeedData("dashjr.org", "dnsseed.bitcoin.dashjr.org")); // Luke Dashjr
-        vSeeds.push_back(CDNSSeedData("bitcoinstats.com", "seed.bitcoinstats.com", true)); // Christian Decker, supports x1 - xf
-        vSeeds.push_back(CDNSSeedData("bitcoin.jonasschnelli.ch", "seed.bitcoin.jonasschnelli.ch", true)); // Jonas Schnelli, only supports x1, x5, x9, and xd
-        vSeeds.push_back(CDNSSeedData("petertodd.org", "seed.btc.petertodd.org", true)); // Peter Todd, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("seed.bitcoin.sipa.be", true); // Pieter Wuille, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("dnsseed.bluematt.me", true); // Matt Corallo, only supports x9
+        vSeeds.emplace_back("dnsseed.bitcoin.dashjr.org"); // Luke Dashjr
+        vSeeds.emplace_back("seed.bitcoinstats.com", true); // Christian Decker, supports x1 - xf
+        vSeeds.emplace_back("seed.bitcoin.jonasschnelli.ch", true); // Jonas Schnelli, only supports x1, x5, x9, and xd
+        vSeeds.emplace_back("seed.btc.petertodd.org", true); // Peter Todd, only supports x1, x5, x9, and xd
 
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,0);
         base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,5);
@@ -225,10 +225,10 @@ class CTestNetParams : public CChainParams {
         vFixedSeeds.clear();
         vSeeds.clear();
         // nodes with support for servicebits filtering should be at the top
-        vSeeds.push_back(CDNSSeedData("testnetbitcoin.jonasschnelli.ch", "testnet-seed.bitcoin.jonasschnelli.ch", true));
-        vSeeds.push_back(CDNSSeedData("petertodd.org", "seed.tbtc.petertodd.org", true));
-        vSeeds.push_back(CDNSSeedData("bluematt.me", "testnet-seed.bluematt.me"));
-        vSeeds.push_back(CDNSSeedData("bitcoin.schildbach.de", "testnet-seed.bitcoin.schildbach.de"));
+        vSeeds.emplace_back("testnet-seed.bitcoin.jonasschnelli.ch", true);
+        vSeeds.emplace_back("seed.tbtc.petertodd.org", true);
+        vSeeds.emplace_back("testnet-seed.bluematt.me");
+        vSeeds.emplace_back("testnet-seed.bitcoin.schildbach.de");
 
         base58Prefixes[PUBKEY_ADDRESS] = std::vector<unsigned char>(1,111);
         base58Prefixes[SCRIPT_ADDRESS] = std::vector<unsigned char>(1,196);

src/chainparams.h

@@ -15,9 +15,9 @@
 #include <vector>
 
 struct CDNSSeedData {
-    std::string name, host;
+    std::string host;
     bool supportsServiceBitsFiltering;
-    CDNSSeedData(const std::string &strName, const std::string &strHost, bool supportsServiceBitsFilteringIn = false) : name(strName), host(strHost), supportsServiceBitsFiltering(supportsServiceBitsFilteringIn) {}
+    CDNSSeedData(const std::string &strHost, bool supportsServiceBitsFilteringIn = false) : host(strHost), supportsServiceBitsFiltering(supportsServiceBitsFilteringIn) {}
 };
 
 struct SeedSpec6 {

src/net.cpp

@@ -1604,7 +1604,12 @@ void CConnman::ThreadDNSAddressSeed()
             std::vector<CNetAddr> vIPs;
             std::vector<CAddress> vAdd;
             ServiceFlags requiredServiceBits = nRelevantServices;
-            if (LookupHost(GetDNSHost(seed, &requiredServiceBits).c_str(), vIPs, 0, true))
+            std::string host = GetDNSHost(seed, &requiredServiceBits);
+            CNetAddr resolveSource;
+            if (!resolveSource.SetInternal(host)) {
+                continue;
+            }
+            if (LookupHost(host.c_str(), vIPs, 0, true))
             {
                 BOOST_FOREACH(const CNetAddr& ip, vIPs)
                 {
@@ -1614,18 +1619,7 @@ void CConnman::ThreadDNSAddressSeed()
                     vAdd.push_back(addr);
                     found++;
                 }
-            }
-            if (interruptNet) {
-                return;
-            }
-            // TODO: The seed name resolve may fail, yielding an IP of [::], which results in
-            // addrman assigning the same source to results from different seeds.
-            // This should switch to a hard-coded stable dummy IP for each seed name, so that the
-            // resolve is not required at all.
-            if (!vIPs.empty()) {
-                CService seedSource;
-                Lookup(seed.name.c_str(), seedSource, 0, true);
-                addrman.Add(vAdd, seedSource);
+                addrman.Add(vAdd, resolveSource);
             }
         }
     }