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-rw-r--r--src/net.cpp2
-rw-r--r--src/net.h17
2 files changed, 14 insertions, 5 deletions
diff --git a/src/net.cpp b/src/net.cpp
index 3eac2235a5..7dec4abfb9 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -1811,7 +1811,7 @@ void CConnman::SetTryNewOutboundPeer(bool flag)
// Return the number of peers we have over our outbound connection limit
// Exclude peers that are marked for disconnect, or are going to be
-// disconnected soon (eg one-shots and feelers)
+// disconnected soon (eg ADDR_FETCH and FEELER)
// Also exclude peers that haven't finished initial connection handshake yet
// (so that we don't decide we're over our desired connection limit, and then
// evict some peer that has finished the handshake)
diff --git a/src/net.h b/src/net.h
index ca65c1dc19..fb68827144 100644
--- a/src/net.h
+++ b/src/net.h
@@ -153,10 +153,19 @@ enum class ConnectionType {
MANUAL,
/**
- * Feeler connections are short lived connections used to increase the
- * number of connectable addresses in our AddrMan. Approximately every
- * FEELER_INTERVAL, we attempt to connect to a random address from the new
- * table. If successful, we add it to the tried table.
+ * Feeler connections are short-lived connections made to check that a node
+ * is alive. They can be useful for:
+ * - test-before-evict: if one of the peers is considered for eviction from
+ * our AddrMan because another peer is mapped to the same slot in the tried table,
+ * evict only if this longer-known peer is offline.
+ * - move node addresses from New to Tried table, so that we have more
+ * connectable addresses in our AddrMan.
+ * Note that in the literature ("Eclipse Attacks on Bitcoin’s Peer-to-Peer Network")
+ * only the latter feature is referred to as "feeler connections",
+ * although in our codebase feeler connections encompass test-before-evict as well.
+ * We make these connections approximately every FEELER_INTERVAL:
+ * first we resolve previously found collisions if they exist (test-before-evict),
+ * otherwise connect to a node from the new table.
*/
FEELER,