[PATCH net-next 03/11] ipvs: add conn_lfactor and svc_lfactor sysctl vars

Florian Westphal
2026-04-10T11:24:10Z

From: Julian Anastasov <ja@ssi.bg>

Allow the default load factor for the connection and service tables
to be configured.

Signed-off-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Florian Westphal <fw@strlen.de>
---
Documentation/networking/ipvs-sysctl.rst | 37 ++++++++++++
net/netfilter/ipvs/ip_vs_ctl.c | 76 ++++++++++++++++++++++++
2 files changed, 113 insertions(+)

diff --git a/Documentation/networking/ipvs-sysctl.rst b/Documentation/networking/ipvs-sysctl.rst
index 3fb5fa142eef..a556439f8be7 100644
--- a/Documentation/networking/ipvs-sysctl.rst
+++ b/Documentation/networking/ipvs-sysctl.rst
@@ -29,6 +29,33 @@ backup_only - BOOLEAN
If set, disable the director function while the server is
in backup mode to avoid packet loops for DR/TUN methods.

+conn_lfactor - INTEGER
+ Possible values: -8 (larger table) .. 8 (smaller table)
+
+ Default: -4
+
+ Controls the sizing of the connection hash table based on the
+ load factor (number of connections per table buckets):
+
+ 2^conn_lfactor = nodes / buckets
+
+ As result, the table grows if load increases and shrinks when
+ load decreases in the range of 2^8 - 2^conn_tab_bits (module
+ parameter).
+ The value is a shift count where negative values select
+ buckets = (connection hash nodes << -value) while positive
+ values select buckets = (connection hash nodes >> value). The
+ negative values reduce the collisions and reduce the time for
+ lookups but increase the table size. Positive values will
+ tolerate load above 100% when using smaller table is
+ preferred with the cost of more collisions. If using NAT
+ connections consider decreasing the value with one because
+ they add two nodes in the hash table.
+
+ Example:
+ -4: grow if load goes above 6% (buckets = nodes * 16)
+ 2: grow if load goes above 400% (buckets = nodes / 4)
+
conn_reuse_mode - INTEGER
1 - default

@@ -219,6 +246,16 @@ secure_tcp - INTEGER
The value definition is the same as that of drop_entry and
drop_packet.

+svc_lfactor - INTEGER
+ Possible values: -8 (larger table) .. 8 (smaller table)
+
+ Default: -3
+
+ Controls the sizing of the service hash table based on the
+ load factor (number of services per table buckets). The table
+ will grow and shrink in the range of 2^4 - 2^20.
+ See conn_lfactor for explanation.
+
sync_threshold - vector of 2 INTEGERs: sync_threshold, sync_period
default 3 50

diff --git a/net/netfilter/ipvs/ip_vs_ctl.c b/net/netfilter/ipvs/ip_vs_ctl.c
index fb1df61edfdd..6632daa87ded 100644
--- a/net/netfilter/ipvs/ip_vs_ctl.c
+++ b/net/netfilter/ipvs/ip_vs_ctl.c
@@ -2445,6 +2445,60 @@ static int ipvs_proc_run_estimation(const struct ctl_table *table, int write,
return ret;
}

+static int ipvs_proc_conn_lfactor(const struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct netns_ipvs *ipvs = table->extra2;
+ int *valp = table->data;
+ int val = *valp;
+ int ret;
+
+ struct ctl_table tmp_table = {
+ .data = &val,
+ .maxlen = sizeof(int),
+ };
+
+ ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
+ if (write && ret >= 0) {
+ if (val < -8 || val > 8) {
+ ret = -EINVAL;
+ } else {
+ *valp = val;
+ if (rcu_access_pointer(ipvs->conn_tab))
+ mod_delayed_work(system_unbound_wq,
+ &ipvs->conn_resize_work, 0);
+ }
+ }
+ return ret;
+}
+
+static int ipvs_proc_svc_lfactor(const struct ctl_table *table, int write,
+ void *buffer, size_t *lenp, loff_t *ppos)
+{
+ struct netns_ipvs *ipvs = table->extra2;
+ int *valp = table->data;
+ int val = *valp;
+ int ret;
+
+ struct ctl_table tmp_table = {
+ .data = &val,
+ .maxlen = sizeof(int),
+ };
+
+ ret = proc_dointvec(&tmp_table, write, buffer, lenp, ppos);
+ if (write && ret >= 0) {
+ if (val < -8 || val > 8) {
+ ret = -EINVAL;
+ } else {
+ *valp = val;
+ if (rcu_access_pointer(ipvs->svc_table))
+ mod_delayed_work(system_unbound_wq,
+ &ipvs->svc_resize_work, 0);
+ }
+ }
+ return ret;
+}
+
/*
* IPVS sysctl table (under the /proc/sys/net/ipv4/vs/)
* Do not change order or insert new entries without
@@ -2633,6 +2687,18 @@ static struct ctl_table vs_vars[] = {
.mode = 0644,
.proc_handler = ipvs_proc_est_nice,
},
+ {
+ .procname = "conn_lfactor",
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = ipvs_proc_conn_lfactor,
+ },
+ {
+ .procname = "svc_lfactor",
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = ipvs_proc_svc_lfactor,
+ },
#ifdef CONFIG_IP_VS_DEBUG
{
.procname = "debug_level",
@@ -4853,6 +4919,16 @@ static int __net_init ip_vs_control_net_init_sysctl(struct netns_ipvs *ipvs)
tbl[idx].extra2 = ipvs;
tbl[idx++].data = &ipvs->sysctl_est_nice;

+ if (unpriv)
+ tbl[idx].mode = 0444;
+ tbl[idx].extra2 = ipvs;
+ tbl[idx++].data = &ipvs->sysctl_conn_lfactor;
+
+ if (unpriv)
+ tbl[idx].mode = 0444;
+ tbl[idx].extra2 = ipvs;
+ tbl[idx++].data = &ipvs->sysctl_svc_lfactor;
+
#ifdef CONFIG_IP_VS_DEBUG
/* Global sysctls must be ro in non-init netns */
if (!net_eq(net, &init_net))
--
2.52.0