There is an old fix of SB_MAX, increasing it to 2MB (instead of 256k) makes
TCP scaling factor 6 (instead of 3).
But the comment in the shifting remained with the old values.
Although it's just a comment, it might be very confusing.
diff --git a/sys/netinet/tcp_input.c b/sys/netinet/tcp_input.c
index cd0c12dcd3ba..74ce2621f762 100644
--- a/sys/netinet/tcp_input.c
+++ b/sys/netinet/tcp_input.c
@@ -3832,8 +3832,8 @@ syn_cache_add(struct sockaddr *src, struct sockaddr
*dst, struct tcphdr *th,
* leading to serious problems when traversing these
* broken firewalls.
*
- * With the default sbmax of 256K, a scale factor
- * of 3 will be chosen by this algorithm. Those who
+ * With the default sbmax of 2MB, a scale factor
+ * of 6 will be chosen by this algorithm. Those who
* choose a larger sbmax should watch out
* for the compatibility problems mentioned above.
*
