Re: [PATCH 12/13 net-next] net: ipv4: disable IPv4-only sysctls when CONFIG_IPV4=n

To avoid noise and unexpected problems, let's hide all the sysctls that
are related to IPv4 only when the kernel is compiled without IPv4
support.

Signed-off-by: Fernando Fernandez Mancera <redacted>
---
 net/ipv4/sysctl_net_ipv4.c | 30 +++++++++++++++++++++++++++---
 1 file changed, 27 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index f6c7b755fa7e..f86883ea0c20 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c

@@ -31,8 +31,8 @@ static int tcp_min_snd_mss_max = 65535;
 static int tcp_rto_max_max = TCP_RTO_MAX_SEC * MSEC_PER_SEC;
 static int ip_privileged_port_min;
 static int ip_privileged_port_max = 65535;
-static int ip_ttl_min = 1;
-static int ip_ttl_max = 255;
+static int ip_ttl_min __maybe_unused = 1;
+static int ip_ttl_max __maybe_unused = 255;
 static int tcp_syn_retries_min = 1;
 static int tcp_syn_retries_max = MAX_TCP_SYNCNT;
 static int tcp_syn_linear_timeouts_max = MAX_TCP_SYNCNT;

@@ -48,7 +48,7 @@ static int tcp_plb_max_rounds = 31;
 static int tcp_plb_max_cong_thresh = 256;
 static unsigned int tcp_tw_reuse_delay_max = TCP_PAWS_MSL * MSEC_PER_SEC;
 static int tcp_ecn_mode_max = 5;
-static u32 icmp_errors_extension_mask_all =
+static u32 icmp_errors_extension_mask_all __maybe_unused =
 	GENMASK_U8(ICMP_ERR_EXT_COUNT - 1, 0);
 
 /* obsolete */

@@ -199,6 +199,7 @@ static int ipv4_ping_group_range(const struct ctl_table *table, int write,
 	return ret;
 }
 
+#if IS_ENABLED(CONFIG_IPV4)
 static int ipv4_fwd_update_priority(const struct ctl_table *table, int write,
 				    void *buffer, size_t *lenp, loff_t *ppos)
 {

@@ -214,6 +215,7 @@ static int ipv4_fwd_update_priority(const struct ctl_table *table, int write,
 
 	return ret;
 }
+#endif
 
 static int proc_tcp_congestion_control(const struct ctl_table *ctl, int write,
 				       void *buffer, size_t *lenp, loff_t *ppos)

@@ -439,6 +441,7 @@ static int proc_udp_hash_entries(const struct ctl_table *table, int write,
 }
 
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
+#if IS_ENABLED(CONFIG_IPV4)
 static int proc_fib_multipath_hash_policy(const struct ctl_table *table, int write,
 					  void *buffer, size_t *lenp,
 					  loff_t *ppos)

@@ -469,6 +472,7 @@ static int proc_fib_multipath_hash_fields(const struct ctl_table *table, int wri
 
 	return ret;
 }
+#endif
 
 static u32 proc_fib_multipath_hash_rand_seed __ro_after_init;
 

@@ -490,6 +494,7 @@ static void proc_fib_multipath_hash_set_seed(struct net *net, u32 user_seed)
 	WRITE_ONCE(net->ipv4.sysctl_fib_multipath_hash_seed.mp_seed, new.mp_seed);
 }
 
+#if IS_ENABLED(CONFIG_IPV4)
 static int proc_fib_multipath_hash_seed(const struct ctl_table *table, int write,
 					void *buffer, size_t *lenp,
 					loff_t *ppos)

@@ -515,6 +520,7 @@ static int proc_fib_multipath_hash_seed(const struct ctl_table *table, int write
 
 	return ret;
 }
+#endif
 #else
 
 static void proc_fib_multipath_hash_init_rand_seed(void)

@@ -634,6 +640,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "icmp_echo_ignore_all",
 		.data		= &init_net.ipv4.sysctl_icmp_echo_ignore_all,

@@ -643,6 +650,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE
 	},
+#endif
 	{
 		.procname	= "icmp_echo_enable_probe",
 		.data		= &init_net.ipv4.sysctl_icmp_echo_enable_probe,

@@ -652,6 +660,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "icmp_echo_ignore_broadcasts",
 		.data		= &init_net.ipv4.sysctl_icmp_echo_ignore_broadcasts,

@@ -702,6 +711,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dointvec
 	},
+#endif
 	{
 		.procname	= "icmp_msgs_per_sec",
 		.data		= &init_net.ipv4.sysctl_icmp_msgs_per_sec,

@@ -772,6 +782,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "ip_dynaddr",
 		.data		= &init_net.ipv4.sysctl_ip_dynaddr,

@@ -779,6 +790,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dou8vec_minmax,
 	},
+#endif
 	{
 		.procname	= "ip_early_demux",
 		.data		= &init_net.ipv4.sysctl_ip_early_demux,

@@ -809,6 +821,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_ONE,
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "ip_default_ttl",
 		.data		= &init_net.ipv4.sysctl_ip_default_ttl,

@@ -818,6 +831,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= &ip_ttl_min,
 		.extra2		= &ip_ttl_max,
 	},
+#endif
 	{
 		.procname	= "ip_local_port_range",
 		.maxlen		= 0,

@@ -839,6 +853,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_do_large_bitmap,
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "ip_no_pmtu_disc",
 		.data		= &init_net.ipv4.sysctl_ip_no_pmtu_disc,

@@ -869,6 +884,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dou8vec_minmax,
 	},
+#endif
 	{
 		.procname	= "ip_autobind_reuse",
 		.data		= &init_net.ipv4.sysctl_ip_autobind_reuse,

@@ -878,6 +894,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1         = SYSCTL_ZERO,
 		.extra2         = SYSCTL_ONE,
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "fwmark_reflect",
 		.data		= &init_net.ipv4.sysctl_fwmark_reflect,

@@ -885,6 +902,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_dou8vec_minmax,
 	},
+#endif
 	{
 		.procname	= "tcp_fwmark_accept",
 		.data		= &init_net.ipv4.sysctl_tcp_fwmark_accept,

@@ -950,6 +968,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.proc_handler	= proc_douintvec_minmax,
 		.extra2		= &u32_max_div_HZ,
 	},
+#if IS_ENABLED(CONFIG_IPV4)

 	{
 		.procname	= "igmp_link_local_mcast_reports",
 		.data		= &init_net.ipv4.sysctl_igmp_llm_reports,

@@ -980,6 +999,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ONE
 	},
+#endif
 #endif
 	{
 		.procname	= "tcp_congestion_control",

@@ -1152,6 +1172,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.proc_handler	= proc_tfo_blackhole_detect_timeout,
 		.extra1		= SYSCTL_ZERO,
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 #ifdef CONFIG_IP_ROUTE_MULTIPATH
 	{
 		.procname	= "fib_multipath_use_neigh",

@@ -1187,6 +1208,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.mode		= 0644,
 		.proc_handler	= proc_fib_multipath_hash_seed,
 	},
+#endif
 #endif
 	{
 		.procname	= "ip_unprivileged_port_start",

@@ -1561,6 +1583,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.proc_handler	= proc_dointvec_minmax,
 		.extra1		= SYSCTL_ONE
 	},
+#if IS_ENABLED(CONFIG_IPV4)
 	{
 		.procname	= "fib_notify_on_flag_change",
 		.data		= &init_net.ipv4.sysctl_fib_notify_on_flag_change,

@@ -1570,6 +1593,7 @@ static const struct ctl_table ipv4_net_table[] = {
 		.extra1		= SYSCTL_ZERO,
 		.extra2		= SYSCTL_TWO,
 	},
+#endif
 	{
 		.procname       = "tcp_plb_enabled",
 		.data           = &init_net.ipv4.sysctl_tcp_plb_enabled,

-- 
2.55.0