Add visitor-topic-creation-limit-* options

server/server.yml

@@ -358,6 +358,15 @@
 # visitor-email-limit-burst: 16
 # visitor-email-limit-replenish: "1h"
 
+# Rate limiting: Allowed new topic creations per visitor. A "creation" is when a request
+# causes a previously-unknown topic ID to be added to the in-memory topic map. Touches of
+# existing topics do not consume tokens. Mitigates topic-enumeration / squatting attacks.
+# - visitor-topic-creation-limit-burst is the initial bucket of new-topic tokens (0 = disabled)
+# - visitor-topic-creation-limit-replenish is the rate at which the bucket is refilled
+#
+# visitor-topic-creation-limit-burst: 100
+# visitor-topic-creation-limit-replenish: "1m"
+
 # Rate limiting: IPv4/IPv6 address prefix bits used for rate limiting
 # - visitor-prefix-bits-ipv4: number of bits of the IPv4 address to use for rate limiting (default: 32, full address)
 # - visitor-prefix-bits-ipv6: number of bits of the IPv6 address to use for rate limiting (default: 64, /64 subnet)