ipvs: increase ip_vs_conn_tab_bits range for 64BIT

Current range [8, 20] is set purely due to historical reasons
because at the time, ~1M (2^20) was considered sufficient.
With this change, 27 is the upper limit for 64-bit, 20 otherwise.

Previous change regarding this limit is here.

Link: https://lore.kernel.org/all/[e-mail]/T/#u

Signed-off-by: Abhijeet Rastogi <[e-mail]>
Acked-by: Julian Anastasov <[e-mail]>
Acked-by: Simon Horman <[e-mail]>
Signed-off-by: Pablo Neira Ayuso <[e-mail]>

net/netfilter/ipvs/Kconfig

···
 
 config	IP_VS_TAB_BITS
 	int "IPVS connection table size (the Nth power of 2)"
-	range 8 20
+	range 8 20 if !64BIT
+	range 8 27 if 64BIT
 	default 12
 	help
 	  The IPVS connection hash table uses the chaining scheme to handle
···
 
 	  Note the table size must be power of 2. The table size will be the
 	  value of 2 to the your input number power. The number to choose is
-	  from 8 to 20, the default number is 12, which means the table size
-	  is 4096. Don't input the number too small, otherwise you will lose
-	  performance on it. You can adapt the table size yourself, according
-	  to your virtual server application. It is good to set the table size
-	  not far less than the number of connections per second multiplying
-	  average lasting time of connection in the table.  For example, your
-	  virtual server gets 200 connections per second, the connection lasts
-	  for 200 seconds in average in the connection table, the table size
-	  should be not far less than 200x200, it is good to set the table
-	  size 32768 (2**15).
+	  from 8 to 27 for 64BIT(20 otherwise), the default number is 12,
+	  which means the table size is 4096. Don't input the number too
+	  small, otherwise you will lose performance on it. You can adapt the
+	  table size yourself, according to your virtual server application.
+	  It is good to set the table size not far less than the number of
+	  connections per second multiplying average lasting time of
+	  connection in the table.  For example, your virtual server gets 200
+	  connections per second, the connection lasts for 200 seconds in
+	  average in the connection table, the table size should be not far
+	  less than 200x200, it is good to set the table size 32768 (2**15).
 
 	  Another note that each connection occupies 128 bytes effectively and
 	  each hash entry uses 8 bytes, so you can estimate how much memory is
 	  needed for your box.
 
 	  You can overwrite this number setting conn_tab_bits module parameter
-	  or by appending ip_vs.conn_tab_bits=? to the kernel command line
-	  if IP VS was compiled built-in.
+	  or by appending ip_vs.conn_tab_bits=? to the kernel command line if
+	  IP VS was compiled built-in.
 
 comment "IPVS transport protocol load balancing support"
 

net/netfilter/ipvs/ip_vs_conn.c

···
 	int idx;
 
 	/* Compute size and mask */
-	if (ip_vs_conn_tab_bits < 8 || ip_vs_conn_tab_bits > 20) {
-		pr_info("conn_tab_bits not in [8, 20]. Using default value\n");
+	if (ip_vs_conn_tab_bits < 8 || ip_vs_conn_tab_bits > 27) {
+		pr_info("conn_tab_bits not in [8, 27]. Using default value\n");
 		ip_vs_conn_tab_bits = CONFIG_IP_VS_TAB_BITS;
 	}
 	ip_vs_conn_tab_size = 1 << ip_vs_conn_tab_bits;