Comment that most dnsseeds only support some service bits combos

Github-Pull: #8940
Rebased-From: 504c72ad34

src/chainparams.cpp

@@ -114,12 +114,13 @@ public:
         assert(consensus.hashGenesisBlock == uint256S("0x000000000019d6689c085ae165831e934ff763ae46a2a6c172b3f1b60a8ce26f"));
         assert(genesis.hashMerkleRoot == uint256S("0x4a5e1e4baab89f3a32518a88c31bc87f618f76673e2cc77ab2127b7afdeda33b"));
 
-        vSeeds.push_back(CDNSSeedData("bitcoin.sipa.be", "seed.bitcoin.sipa.be", true)); // Pieter Wuille
+        // 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")); // Matt Corallo
         vSeeds.push_back(CDNSSeedData("dashjr.org", "dnsseed.bitcoin.dashjr.org")); // Luke Dashjr
         vSeeds.push_back(CDNSSeedData("bitcoinstats.com", "seed.bitcoinstats.com")); // Christian Decker
         vSeeds.push_back(CDNSSeedData("xf2.org", "bitseed.xf2.org")); // Jeff Garzik
-        vSeeds.push_back(CDNSSeedData("bitcoin.jonasschnelli.ch", "seed.bitcoin.jonasschnelli.ch", true)); // Jonas Schnelli
+        vSeeds.push_back(CDNSSeedData("bitcoin.jonasschnelli.ch", "seed.bitcoin.jonasschnelli.ch", true)); // Jonas Schnelli, 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);

src/net.cpp

@@ -1489,6 +1489,7 @@ static std::string GetDNSHost(const CDNSSeedData& data, ServiceFlags* requiredSe
         return data.host;
     }
 
+    // See chainparams.cpp, most dnsseeds only support one or two possible servicebits hostnames
     return strprintf("x%x.%s", *requiredServiceBits, data.host);
 }