From b3e26cc757a2f6d96cda41c100e9607daab50c02 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Wed, 8 Jun 2016 17:33:21 +0200
Subject: [PATCH] Merge #8083: Add support for dnsseeds with option to filter
 by servicebits

2d83013d Add support for dnsseeds with option to filter by servicebits (Jonas Schnelli)
---
 src/chainparams.cpp | 9 +++++++++
 src/chainparams.h   | 7 +++++--
 src/net.cpp         | 5 +++--
 3 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 49d25760d..c289f4f26 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -19,6 +19,14 @@
 
 #include "chainparamsseeds.h"
 
+std::string CDNSSeedData::getHost(uint64_t requiredServiceBits) const {
+    //use default host for non-filter-capable seeds or if we use the default service bits (NODE_NETWORK)
+    if (!supportsServiceBitsFiltering || requiredServiceBits == NODE_NETWORK)
+        return host;
+    
+    return strprintf("x%x.%s", requiredServiceBits, host);
+}
+
 static CBlock CreateGenesisBlock(const char* pszTimestamp, const CScript& genesisOutputScript, uint32_t nTime, uint32_t nNonce, uint32_t nBits, int32_t nVersion, const CAmount& genesisReward)
 {
     CMutableTransaction txNew;
@@ -328,6 +336,7 @@ public:
 
         vFixedSeeds.clear();
         vSeeds.clear();
+        // nodes with support for servicebits filtering should be at the top
         vSeeds.push_back(CDNSSeedData("dashdot.io",  "testnet-seed.dashdot.io"));
         vSeeds.push_back(CDNSSeedData("masternode.io", "test.dnsseed.masternode.io"));
 
diff --git a/src/chainparams.h b/src/chainparams.h
index 973c7c9eb..ed1d1abca 100644
--- a/src/chainparams.h
+++ b/src/chainparams.h
@@ -13,9 +13,12 @@
 
 #include <vector>
 
-struct CDNSSeedData {
+class CDNSSeedData {
+public:
     std::string name, host;
-    CDNSSeedData(const std::string &strName, const std::string &strHost) : name(strName), host(strHost) {}
+    bool supportsServiceBitsFiltering;
+    std::string getHost(uint64_t requiredServiceBits) const;
+    CDNSSeedData(const std::string &strName, const std::string &strHost, bool supportsServiceBitsFilteringIn = false) : name(strName), host(strHost), supportsServiceBitsFiltering(supportsServiceBitsFilteringIn) {}
 };
 
 struct SeedSpec6 {
diff --git a/src/net.cpp b/src/net.cpp
index 5d78fb1d5..6bbb43937 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1528,12 +1528,13 @@ void CConnman::ThreadDNSAddressSeed()
         } else {
             std::vector<CNetAddr> vIPs;
             std::vector<CAddress> vAdd;
-            if (LookupHost(seed.host.c_str(), vIPs, 0, true))
+            ServiceFlags requiredServiceBits = NODE_NETWORK;
+            if (LookupHost(seed.getHost(requiredServiceBits).c_str(), vIPs, 0, true))
             {
                 BOOST_FOREACH(const CNetAddr& ip, vIPs)
                 {
                     int nOneDay = 24*3600;
-                    CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), NODE_NETWORK);
+                    CAddress addr = CAddress(CService(ip, Params().GetDefaultPort()), requiredServiceBits);
                     addr.nTime = GetTime() - 3*nOneDay - GetRand(4*nOneDay); // use a random age between 3 and 7 days old
                     vAdd.push_back(addr);
                     found++;