Merge #10446: net: avoid extra dns query per seed

c1be285 chainparams: make supported service bits option explicit (Cory Fields)
d5c7c1c net: use an internal address for fixed seeds (Cory Fields)
6cdc488 net: switch to dummy internal ip for dns seed source (Cory Fields)
6d0bd5b net: do not allow resolving to an internal address (Cory Fields)
7f31762 net: add an internal subnet for representing unresolved hostnames (Cory Fields)

Tree-SHA512: 9bf1042bef546ac3ef0e0d3a9a5555eb21628ff2674a0cf8c6367194b22bfdab477adf452c0e7c56f44e0fb37debc5e14bdb623452e076fb9c492c7702601d7a

1 files changed, 9 insertions, 15 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 73f020273b..43bd0eb0d5 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -240,7 +240,7 @@ bool RemoveLocal(const CService& addr)
 /** Make a particular network entirely off-limits (no automatic connects to it) */
 void SetLimited(enum Network net, bool fLimited)
 {
-    if (net == NET_UNROUTABLE)
+    if (net == NET_UNROUTABLE || net == NET_INTERNAL)
         return;
     LOCK(cs_mapLocalHost);
     vfLimited[net] = fLimited;
@@ -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))
             {
                 for (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);
             }
         }
     }
@@ -1724,7 +1718,7 @@ void CConnman::ThreadOpenConnections()
             if (!done) {
                 LogPrintf("Adding fixed seed nodes as DNS doesn't seem to be available.\n");
                 CNetAddr local;
-                LookupHost("127.0.0.1", local, false);
+                local.SetInternal("fixedseeds");
                 addrman.Add(convertSeed6(Params().FixedSeeds()), local);
                 done = true;
             }