From 2d83013dc54320b3f0c978475517da6156f7b50d Mon Sep 17 00:00:00 2001
From: Jonas Schnelli <dev@jonasschnelli.ch>
Date: Sat, 21 May 2016 23:55:22 +0200
Subject: [PATCH] Add support for dnsseeds with option to filter by servicebits

---
 src/chainparams.cpp | 10 ++++++++++
 src/chainparams.h   |  7 +++++--
 src/net.cpp         |  5 +++--
 3 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/src/chainparams.cpp b/src/chainparams.cpp
index 5c7d190125..0005115671 100644
--- a/src/chainparams.cpp
+++ b/src/chainparams.cpp
@@ -16,6 +16,14 @@
 
 #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;
@@ -197,6 +205,8 @@ public:
 
         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("bitcoin.petertodd.org", "testnet-seed.bitcoin.petertodd.org"));
         vSeeds.push_back(CDNSSeedData("bluematt.me", "testnet-seed.bluematt.me"));
         vSeeds.push_back(CDNSSeedData("bitcoin.schildbach.de", "testnet-seed.bitcoin.schildbach.de"));
diff --git a/src/chainparams.h b/src/chainparams.h
index 59202f548a..7168daaf43 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 bbd23d292a..54d14a7234 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1466,12 +1466,13 @@ void ThreadDNSAddressSeed()
         } else {
             std::vector<CNetAddr> vIPs;
             std::vector<CAddress> vAdd;
-            if (LookupHost(seed.host.c_str(), vIPs, 0, true))
+            uint64_t 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()));
+                    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++;