[PATCH] ipvs: change ip_vs_conn_tab_bits range to [8,31]

[Abhijeet Rastogi via B4 Relay <devnull+abhijeet.1989.gmail.com@xxxxxxxxxx>]

From: Abhijeet Rastogi <abhijeet.1989@xxxxxxxxx>

Current range [8, 20] is set purely due to historical reasons
because at the time, ~1M (2^20) was considered sufficient.

Previous change regarding this limit is here.

Link: 
https://lore.kernel.org/all/86eabeb9dd62aebf1e2533926fdd13fed48bab1f.1631289960.git.aclaudi@xxxxxxxxxx/T/#u

Signed-off-by: Abhijeet Rastogi <abhijeet.1989@xxxxxxxxx>
---
The conversation for this started at: 

https://www.spinics.net/lists/netfilter/msg60995.html

The upper limit for algo is any bit size less than 32, so this
change will allow us to set bit size > 20. Today, it is common to have
RAM available to handle greater than 2^20 connections per-host.

Distros like RHEL already have higher limits set.
---
 net/netfilter/ipvs/Kconfig      | 4 ++--
 net/netfilter/ipvs/ip_vs_conn.c | 4 ++--
 2 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/netfilter/ipvs/Kconfig b/net/netfilter/ipvs/Kconfig
index 271da8447b29..3e3371f8c0f9 100644
--- a/net/netfilter/ipvs/Kconfig
+++ b/net/netfilter/ipvs/Kconfig
@@ -44,7 +44,7 @@ config        IP_VS_DEBUG
 
 config IP_VS_TAB_BITS
        int "IPVS connection table size (the Nth power of 2)"
-       range 8 20
+       range 8 31
        default 12
        help
          The IPVS connection hash table uses the chaining scheme to handle
@@ -54,7 +54,7 @@ config        IP_VS_TAB_BITS
 
          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
+         from 8 to 31, 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
diff --git a/net/netfilter/ipvs/ip_vs_conn.c b/net/netfilter/ipvs/ip_vs_conn.c
index 13534e02346c..bc0fe1a698d4 100644
--- a/net/netfilter/ipvs/ip_vs_conn.c
+++ b/net/netfilter/ipvs/ip_vs_conn.c
@@ -1484,8 +1484,8 @@ int __init ip_vs_conn_init(void)
        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 > 31) {
+               pr_info("conn_tab_bits not in [8, 31]. 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;

---
base-commit: 09a9639e56c01c7a00d6c0ca63f4c7c41abe075d
change-id: 20230412-increase_ipvs_conn_tab_bits-4322c90da216

Best regards,
-- 
Abhijeet Rastogi <abhijeet.1989@xxxxxxxxx>