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![Kuniyuki Iwashima](/assets/img/avatar_default.png)
The maximum hash table size is 64K due to the nature of the protocol. [0] It's smaller than TCP, and fewer sockets can cause a performance drop. On an EC2 c5.24xlarge instance (192 GiB memory), after running iperf3 in different netns, creating 32Mi sockets without data transfer in the root netns causes regression for the iperf3's connection. uhash_entries sockets length Gbps 64K 1 1 5.69 1Mi 16 5.27 2Mi 32 4.90 4Mi 64 4.09 8Mi 128 2.96 16Mi 256 2.06 32Mi 512 1.12 The per-netns hash table breaks the lengthy lists into shorter ones. It is useful on a multi-tenant system with thousands of netns. With smaller hash tables, we can look up sockets faster, isolate noisy neighbours, and reduce lock contention. The max size of the per-netns table is 64K as well. This is because the possible hash range by udp_hashfn() always fits in 64K within the same netns and we cannot make full use of the whole buckets larger than 64K. /* 0 < num < 64K -> X < hash < X + 64K */ (num + net_hash_mix(net)) & mask; Also, the min size is 128. We use a bitmap to search for an available port in udp_lib_get_port(). To keep the bitmap on the stack and not fire the CONFIG_FRAME_WARN error at build time, we round up the table size to 128. The sysctl usage is the same with TCP: $ dmesg | cut -d ' ' -f 6- | grep "UDP hash" UDP hash table entries: 65536 (order: 9, 2097152 bytes, vmalloc) # sysctl net.ipv4.udp_hash_entries net.ipv4.udp_hash_entries = 65536 # can be changed by uhash_entries # sysctl net.ipv4.udp_child_hash_entries net.ipv4.udp_child_hash_entries = 0 # disabled by default # ip netns add test1 # ip netns exec test1 sysctl net.ipv4.udp_hash_entries net.ipv4.udp_hash_entries = -65536 # share the global table # sysctl -w net.ipv4.udp_child_hash_entries=100 net.ipv4.udp_child_hash_entries = 100 # ip netns add test2 # ip netns exec test2 sysctl net.ipv4.udp_hash_entries net.ipv4.udp_hash_entries = 128 # own a per-netns table with 2^n buckets We could optimise the hash table lookup/iteration further by removing the netns comparison for the per-netns one in the future. Also, we could optimise the sparse udp_hslot layout by putting it in udp_table. [0]: https://lore.kernel.org/netdev/4ACC2815.7010101@gmail.com/ Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com> Signed-off-by: David S. Miller <davem@davemloft.net>
241 lines
6 KiB
C
241 lines
6 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* ipv4 in net namespaces
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*/
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#ifndef __NETNS_IPV4_H__
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#define __NETNS_IPV4_H__
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#include <linux/uidgid.h>
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#include <net/inet_frag.h>
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#include <linux/rcupdate.h>
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#include <linux/seqlock.h>
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#include <linux/siphash.h>
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struct ctl_table_header;
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struct ipv4_devconf;
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struct fib_rules_ops;
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struct hlist_head;
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struct fib_table;
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struct sock;
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struct local_ports {
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seqlock_t lock;
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int range[2];
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bool warned;
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};
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struct ping_group_range {
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seqlock_t lock;
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kgid_t range[2];
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};
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struct inet_hashinfo;
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struct inet_timewait_death_row {
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refcount_t tw_refcount;
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/* Padding to avoid false sharing, tw_refcount can be often written */
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struct inet_hashinfo *hashinfo ____cacheline_aligned_in_smp;
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int sysctl_max_tw_buckets;
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};
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struct tcp_fastopen_context;
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struct netns_ipv4 {
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struct inet_timewait_death_row tcp_death_row;
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struct udp_table *udp_table;
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#ifdef CONFIG_SYSCTL
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struct ctl_table_header *forw_hdr;
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struct ctl_table_header *frags_hdr;
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struct ctl_table_header *ipv4_hdr;
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struct ctl_table_header *route_hdr;
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struct ctl_table_header *xfrm4_hdr;
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#endif
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struct ipv4_devconf *devconf_all;
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struct ipv4_devconf *devconf_dflt;
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struct ip_ra_chain __rcu *ra_chain;
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struct mutex ra_mutex;
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#ifdef CONFIG_IP_MULTIPLE_TABLES
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struct fib_rules_ops *rules_ops;
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struct fib_table __rcu *fib_main;
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struct fib_table __rcu *fib_default;
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unsigned int fib_rules_require_fldissect;
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bool fib_has_custom_rules;
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#endif
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bool fib_has_custom_local_routes;
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bool fib_offload_disabled;
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#ifdef CONFIG_IP_ROUTE_CLASSID
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atomic_t fib_num_tclassid_users;
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#endif
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struct hlist_head *fib_table_hash;
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struct sock *fibnl;
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struct sock *mc_autojoin_sk;
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struct inet_peer_base *peers;
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struct fqdir *fqdir;
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u8 sysctl_icmp_echo_ignore_all;
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u8 sysctl_icmp_echo_enable_probe;
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u8 sysctl_icmp_echo_ignore_broadcasts;
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u8 sysctl_icmp_ignore_bogus_error_responses;
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u8 sysctl_icmp_errors_use_inbound_ifaddr;
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int sysctl_icmp_ratelimit;
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int sysctl_icmp_ratemask;
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u32 ip_rt_min_pmtu;
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int ip_rt_mtu_expires;
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int ip_rt_min_advmss;
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struct local_ports ip_local_ports;
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u8 sysctl_tcp_ecn;
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u8 sysctl_tcp_ecn_fallback;
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u8 sysctl_ip_default_ttl;
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u8 sysctl_ip_no_pmtu_disc;
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u8 sysctl_ip_fwd_use_pmtu;
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u8 sysctl_ip_fwd_update_priority;
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u8 sysctl_ip_nonlocal_bind;
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u8 sysctl_ip_autobind_reuse;
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/* Shall we try to damage output packets if routing dev changes? */
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u8 sysctl_ip_dynaddr;
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u8 sysctl_ip_early_demux;
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#ifdef CONFIG_NET_L3_MASTER_DEV
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u8 sysctl_raw_l3mdev_accept;
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#endif
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u8 sysctl_tcp_early_demux;
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u8 sysctl_udp_early_demux;
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u8 sysctl_nexthop_compat_mode;
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u8 sysctl_fwmark_reflect;
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u8 sysctl_tcp_fwmark_accept;
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#ifdef CONFIG_NET_L3_MASTER_DEV
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u8 sysctl_tcp_l3mdev_accept;
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#endif
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u8 sysctl_tcp_mtu_probing;
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int sysctl_tcp_mtu_probe_floor;
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int sysctl_tcp_base_mss;
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int sysctl_tcp_min_snd_mss;
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int sysctl_tcp_probe_threshold;
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u32 sysctl_tcp_probe_interval;
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int sysctl_tcp_keepalive_time;
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int sysctl_tcp_keepalive_intvl;
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u8 sysctl_tcp_keepalive_probes;
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u8 sysctl_tcp_syn_retries;
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u8 sysctl_tcp_synack_retries;
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u8 sysctl_tcp_syncookies;
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u8 sysctl_tcp_migrate_req;
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u8 sysctl_tcp_comp_sack_nr;
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int sysctl_tcp_reordering;
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u8 sysctl_tcp_retries1;
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u8 sysctl_tcp_retries2;
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u8 sysctl_tcp_orphan_retries;
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u8 sysctl_tcp_tw_reuse;
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int sysctl_tcp_fin_timeout;
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unsigned int sysctl_tcp_notsent_lowat;
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u8 sysctl_tcp_sack;
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u8 sysctl_tcp_window_scaling;
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u8 sysctl_tcp_timestamps;
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u8 sysctl_tcp_early_retrans;
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u8 sysctl_tcp_recovery;
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u8 sysctl_tcp_thin_linear_timeouts;
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u8 sysctl_tcp_slow_start_after_idle;
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u8 sysctl_tcp_retrans_collapse;
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u8 sysctl_tcp_stdurg;
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u8 sysctl_tcp_rfc1337;
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u8 sysctl_tcp_abort_on_overflow;
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u8 sysctl_tcp_fack; /* obsolete */
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int sysctl_tcp_max_reordering;
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int sysctl_tcp_adv_win_scale;
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u8 sysctl_tcp_dsack;
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u8 sysctl_tcp_app_win;
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u8 sysctl_tcp_frto;
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u8 sysctl_tcp_nometrics_save;
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u8 sysctl_tcp_no_ssthresh_metrics_save;
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u8 sysctl_tcp_moderate_rcvbuf;
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u8 sysctl_tcp_tso_win_divisor;
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u8 sysctl_tcp_workaround_signed_windows;
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int sysctl_tcp_limit_output_bytes;
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int sysctl_tcp_challenge_ack_limit;
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int sysctl_tcp_min_rtt_wlen;
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u8 sysctl_tcp_min_tso_segs;
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u8 sysctl_tcp_tso_rtt_log;
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u8 sysctl_tcp_autocorking;
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u8 sysctl_tcp_reflect_tos;
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int sysctl_tcp_invalid_ratelimit;
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int sysctl_tcp_pacing_ss_ratio;
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int sysctl_tcp_pacing_ca_ratio;
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int sysctl_tcp_wmem[3];
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int sysctl_tcp_rmem[3];
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unsigned int sysctl_tcp_child_ehash_entries;
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unsigned long sysctl_tcp_comp_sack_delay_ns;
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unsigned long sysctl_tcp_comp_sack_slack_ns;
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int sysctl_max_syn_backlog;
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int sysctl_tcp_fastopen;
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const struct tcp_congestion_ops __rcu *tcp_congestion_control;
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struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
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unsigned int sysctl_tcp_fastopen_blackhole_timeout;
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atomic_t tfo_active_disable_times;
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unsigned long tfo_active_disable_stamp;
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u32 tcp_challenge_timestamp;
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u32 tcp_challenge_count;
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u8 sysctl_tcp_plb_enabled;
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u8 sysctl_tcp_plb_idle_rehash_rounds;
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u8 sysctl_tcp_plb_rehash_rounds;
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u8 sysctl_tcp_plb_suspend_rto_sec;
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int sysctl_tcp_plb_cong_thresh;
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int sysctl_udp_wmem_min;
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int sysctl_udp_rmem_min;
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u8 sysctl_fib_notify_on_flag_change;
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#ifdef CONFIG_NET_L3_MASTER_DEV
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u8 sysctl_udp_l3mdev_accept;
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#endif
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u8 sysctl_igmp_llm_reports;
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int sysctl_igmp_max_memberships;
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int sysctl_igmp_max_msf;
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int sysctl_igmp_qrv;
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struct ping_group_range ping_group_range;
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atomic_t dev_addr_genid;
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unsigned int sysctl_udp_child_hash_entries;
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#ifdef CONFIG_SYSCTL
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unsigned long *sysctl_local_reserved_ports;
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int sysctl_ip_prot_sock;
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#endif
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#ifdef CONFIG_IP_MROUTE
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#ifndef CONFIG_IP_MROUTE_MULTIPLE_TABLES
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struct mr_table *mrt;
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#else
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struct list_head mr_tables;
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struct fib_rules_ops *mr_rules_ops;
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#endif
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#endif
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#ifdef CONFIG_IP_ROUTE_MULTIPATH
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u32 sysctl_fib_multipath_hash_fields;
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u8 sysctl_fib_multipath_use_neigh;
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u8 sysctl_fib_multipath_hash_policy;
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#endif
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struct fib_notifier_ops *notifier_ops;
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unsigned int fib_seq; /* protected by rtnl_mutex */
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struct fib_notifier_ops *ipmr_notifier_ops;
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unsigned int ipmr_seq; /* protected by rtnl_mutex */
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atomic_t rt_genid;
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siphash_key_t ip_id_key;
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};
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#endif
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