+This is used to modify the IPv4 TTL header field. The TTL field determines
+how many hops (routers) a packet can traverse until it's time to live is
+exceeded.
+.TP
+Setting or incrementing the TTL field can potentially be very dangerous,
+so it should be avoided at any cost.
+.TP
+.B Don't ever set or increment the value on packets that leave your local network!
+.B mangle
+table.
+.TP
+.BI "--ttl-set " "value"
+Set the TTL value to `value'.
+.TP
+.BI "--ttl-dec " "value"
+Decrement the TTL value `value' times.
+.TP
+.BI "--ttl-inc " "value"
+Increment the TTL value `value' times.