Merge pull request #1723 from majestrate/rc-gossip-limiter-2021-08-30

limit RC gossip to 20 peers max

.drone.jsonnet

@@ -22,6 +22,7 @@ local debian_pipeline(name, image,
         cmake_extra='',
         extra_cmds=[],
         jobs=6,
+        tests=true,
         loki_repo=false,
         allow_fail=false) = {
     kind: 'pipeline',
@@ -55,10 +56,12 @@ local debian_pipeline(name, image,
                 'cmake .. -DWITH_SETCAP=OFF -DCMAKE_CXX_FLAGS=-fdiagnostics-color=always -DCMAKE_BUILD_TYPE='+build_type+' ' +
                     (if werror then '-DWARNINGS_AS_ERRORS=ON ' else '') +
                     '-DWITH_LTO=' + (if lto then 'ON ' else 'OFF ') +
+                    (if tests then '' else '-DWITH_TESTS=OFF ') +
                 cmake_extra,
                 'VERBOSE=1 make -j' + jobs,
-                '../contrib/ci/drone-gdb.sh ./test/testAll --use-colour yes',
-            ] + extra_cmds,
+            ]
+            + (if tests then ['../contrib/ci/drone-gdb.sh ./test/testAll --use-colour yes'] else [])
+            + extra_cmds,
         }
     ],
 };
@@ -253,7 +256,7 @@ local mac_builder(name,
     ]),
 
     // Static build (on bionic) which gets uploaded to builds.lokinet.dev:
-    debian_pipeline("Static (bionic amd64)", docker_base+'ubuntu-bionic', deps='g++-8 python3-dev automake libtool', lto=true,
+    debian_pipeline("Static (bionic amd64)", docker_base+'ubuntu-bionic', deps='g++-8 python3-dev automake libtool', lto=true, tests=false,
                     cmake_extra='-DBUILD_STATIC_DEPS=ON -DBUILD_SHARED_LIBS=OFF -DSTATIC_LINK=ON -DCMAKE_C_COMPILER=gcc-8 -DCMAKE_CXX_COMPILER=g++-8 ' +
                         '-DCMAKE_CXX_FLAGS="-march=x86-64 -mtune=haswell" -DCMAKE_C_FLAGS="-march=x86-64 -mtune=haswell" -DNATIVE_BUILD=OFF ' +
                         '-DWITH_SYSTEMD=OFF',

llarp/router/i_gossiper.hpp

@@ -3,6 +3,9 @@
 
 namespace llarp
 {
+  /// The maximum number of peers we will flood a gossiped RC to when propagating an RC
+  constexpr size_t MaxGossipPeers = 20;
+
   struct I_RCGossiper
   {
     virtual ~I_RCGossiper() = default;

llarp/router/rc_gossiper.cpp

@@ -76,17 +76,37 @@ namespace llarp
     DHTImmediateMessage gossip;
     gossip.msgs.emplace_back(new dht::GotRouterMessage(dht::Key_t{}, 0, {rc}, false));
 
-    // send it to everyone
+    std::vector<RouterID> gossipTo;
+
+    // select peers to gossip to
+    m_LinkManager->ForEachPeer(
+        [&](const ILinkSession* peerSession, bool) {
+          // ensure connected session
+          if (not(peerSession && peerSession->IsEstablished()))
+            return;
+          // check if public router
+          const auto other_rc = peerSession->GetRemoteRC();
+          if (not other_rc.IsPublicRouter())
+            return;
+          gossipTo.emplace_back(other_rc.pubkey);
+        },
+        true);
+
+    std::unordered_set<RouterID> keys;
+    // grab the keys we want to use
+    std::sample(
+        gossipTo.begin(), gossipTo.end(), std::inserter(keys, keys.end()), MaxGossipPeers, CSRNG{});
+
     m_LinkManager->ForEachPeer([&](ILinkSession* peerSession) {
-      // ensure connected session
       if (not(peerSession && peerSession->IsEstablished()))
         return;
-      // check if public router
-      const auto other_rc = peerSession->GetRemoteRC();
-      if (not other_rc.IsPublicRouter())
+
+      // exclude from gossip as we have not selected to use it
+      if (keys.count(peerSession->GetPubKey()) == 0)
         return;
+
       // encode message
-      ILinkSession::Message_t msg;
+      ILinkSession::Message_t msg{};
       msg.resize(MAX_LINK_MSG_SIZE / 2);
       llarp_buffer_t buf(msg);
       if (not gossip.BEncode(&buf))