net: Give seednodes time before falling back to fixed seeds

Before, we'd remove a seednode from the list right after connecting
to it, leading to a race with loading the fixed seed and connecting
to them.

2 files changed, 7 insertions, 6 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 337cf60680..ed0b2d6ac8 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1641,6 +1641,7 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
     auto next_extra_block_relay = GetExponentialRand(start, EXTRA_BLOCK_RELAY_ONLY_PEER_INTERVAL);
     const bool dnsseed = gArgs.GetBoolArg("-dnsseed", DEFAULT_DNSSEED);
     bool add_fixed_seeds = gArgs.GetBoolArg("-fixedseeds", DEFAULT_FIXEDSEEDS);
+    const bool use_seednodes{gArgs.IsArgSet("-seednode")};
 
     if (!add_fixed_seeds) {
         LogPrintf("Fixed seeds are disabled\n");
@@ -1670,12 +1671,12 @@ void CConnman::ThreadOpenConnections(const std::vector<std::string> connect)
                 LogPrintf("Adding fixed seeds as 60 seconds have passed and addrman is empty for at least one reachable network\n");
             }
 
-            // Checking !dnsseed is cheaper before locking 2 mutexes.
-            if (!add_fixed_seeds_now && !dnsseed) {
-                LOCK2(m_addr_fetches_mutex, m_added_nodes_mutex);
-                if (m_addr_fetches.empty() && m_added_nodes.empty()) {
+            // Perform cheap checks before locking a mutex.
+            else if (!dnsseed && !use_seednodes) {
+                LOCK(m_added_nodes_mutex);
+                if (m_added_nodes.empty()) {
                     add_fixed_seeds_now = true;
-                    LogPrintf("Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet), -addnode is not provided and all -seednode(s) attempted\n");
+                    LogPrintf("Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet) and neither -addnode nor -seednode are provided\n");
                 }
             }
 
diff --git a/test/functional/feature_config_args.py b/test/functional/feature_config_args.py
index f9730b48c5..664f829fd3 100755
--- a/test/functional/feature_config_args.py
+++ b/test/functional/feature_config_args.py
@@ -213,7 +213,7 @@ class ConfArgsTest(BitcoinTestFramework):
         with self.nodes[0].assert_debug_log(expected_msgs=[
                 "Loaded 0 addresses from peers.dat",
                 "DNS seeding disabled",
-                "Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet), -addnode is not provided and all -seednode(s) attempted\n",
+                "Adding fixed seeds as -dnsseed=0 (or IPv4/IPv6 connections are disabled via -onlynet) and neither -addnode nor -seednode are provided\n",
         ]):
             self.start_node(0, extra_args=['-dnsseed=0', '-fixedseeds=1'])
         assert time.time() - start < 60