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![Eric Dumazet](/assets/img/avatar_default.png)
With RPS inclusion, skb timestamping is not consistent in RX path. If netif_receive_skb() is used, its deferred after RPS dispatch. If netif_rx() is used, its done before RPS dispatch. This can give strange tcpdump timestamps results. I think timestamping should be done as soon as possible in the receive path, to get meaningful values (ie timestamps taken at the time packet was delivered by NIC driver to our stack), even if NAPI already can defer timestamping a bit (RPS can help to reduce the gap) Tom Herbert prefer to sample timestamps after RPS dispatch. In case sampling is expensive (HPET/acpi_pm on x86), this makes sense. Let admins switch from one mode to another, using a new sysctl, /proc/sys/net/core/netdev_tstamp_prequeue Its default value (1), means timestamps are taken as soon as possible, before backlog queueing, giving accurate timestamps. Setting a 0 value permits to sample timestamps when processing backlog, after RPS dispatch, to lower the load of the pre-RPS cpu. Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
248 lines
5.2 KiB
C
248 lines
5.2 KiB
C
/* -*- linux-c -*-
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* sysctl_net_core.c: sysctl interface to net core subsystem.
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*
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* Begun April 1, 1996, Mike Shaver.
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* Added /proc/sys/net/core directory entry (empty =) ). [MS]
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*/
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#include <linux/mm.h>
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#include <linux/sysctl.h>
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#include <linux/module.h>
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#include <linux/socket.h>
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#include <linux/netdevice.h>
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#include <linux/ratelimit.h>
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#include <linux/vmalloc.h>
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#include <linux/init.h>
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#include <linux/slab.h>
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#include <net/ip.h>
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#include <net/sock.h>
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#ifdef CONFIG_RPS
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static int rps_sock_flow_sysctl(ctl_table *table, int write,
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void __user *buffer, size_t *lenp, loff_t *ppos)
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{
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unsigned int orig_size, size;
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int ret, i;
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ctl_table tmp = {
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.data = &size,
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.maxlen = sizeof(size),
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.mode = table->mode
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};
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struct rps_sock_flow_table *orig_sock_table, *sock_table;
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static DEFINE_MUTEX(sock_flow_mutex);
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mutex_lock(&sock_flow_mutex);
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orig_sock_table = rps_sock_flow_table;
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size = orig_size = orig_sock_table ? orig_sock_table->mask + 1 : 0;
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ret = proc_dointvec(&tmp, write, buffer, lenp, ppos);
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if (write) {
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if (size) {
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if (size > 1<<30) {
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/* Enforce limit to prevent overflow */
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mutex_unlock(&sock_flow_mutex);
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return -EINVAL;
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}
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size = roundup_pow_of_two(size);
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if (size != orig_size) {
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sock_table =
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vmalloc(RPS_SOCK_FLOW_TABLE_SIZE(size));
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if (!sock_table) {
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mutex_unlock(&sock_flow_mutex);
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return -ENOMEM;
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}
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sock_table->mask = size - 1;
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} else
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sock_table = orig_sock_table;
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for (i = 0; i < size; i++)
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sock_table->ents[i] = RPS_NO_CPU;
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} else
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sock_table = NULL;
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if (sock_table != orig_sock_table) {
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rcu_assign_pointer(rps_sock_flow_table, sock_table);
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synchronize_rcu();
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vfree(orig_sock_table);
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}
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}
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mutex_unlock(&sock_flow_mutex);
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return ret;
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}
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#endif /* CONFIG_RPS */
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static struct ctl_table net_core_table[] = {
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#ifdef CONFIG_NET
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{
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.procname = "wmem_max",
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.data = &sysctl_wmem_max,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "rmem_max",
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.data = &sysctl_rmem_max,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "wmem_default",
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.data = &sysctl_wmem_default,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "rmem_default",
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.data = &sysctl_rmem_default,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "dev_weight",
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.data = &weight_p,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "netdev_max_backlog",
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.data = &netdev_max_backlog,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "netdev_tstamp_prequeue",
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.data = &netdev_tstamp_prequeue,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "message_cost",
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.data = &net_ratelimit_state.interval,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec_jiffies,
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},
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{
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.procname = "message_burst",
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.data = &net_ratelimit_state.burst,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec,
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},
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{
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.procname = "optmem_max",
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.data = &sysctl_optmem_max,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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#ifdef CONFIG_RPS
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{
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.procname = "rps_sock_flow_entries",
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = rps_sock_flow_sysctl
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},
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#endif
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#endif /* CONFIG_NET */
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{
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.procname = "netdev_budget",
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.data = &netdev_budget,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{
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.procname = "warnings",
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.data = &net_msg_warn,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{ }
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};
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static struct ctl_table netns_core_table[] = {
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{
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.procname = "somaxconn",
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.data = &init_net.core.sysctl_somaxconn,
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.maxlen = sizeof(int),
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.mode = 0644,
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.proc_handler = proc_dointvec
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},
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{ }
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};
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__net_initdata struct ctl_path net_core_path[] = {
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{ .procname = "net", },
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{ .procname = "core", },
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{ },
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};
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static __net_init int sysctl_core_net_init(struct net *net)
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{
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struct ctl_table *tbl;
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net->core.sysctl_somaxconn = SOMAXCONN;
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tbl = netns_core_table;
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if (!net_eq(net, &init_net)) {
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tbl = kmemdup(tbl, sizeof(netns_core_table), GFP_KERNEL);
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if (tbl == NULL)
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goto err_dup;
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tbl[0].data = &net->core.sysctl_somaxconn;
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}
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net->core.sysctl_hdr = register_net_sysctl_table(net,
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net_core_path, tbl);
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if (net->core.sysctl_hdr == NULL)
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goto err_reg;
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return 0;
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err_reg:
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if (tbl != netns_core_table)
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kfree(tbl);
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err_dup:
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return -ENOMEM;
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}
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static __net_exit void sysctl_core_net_exit(struct net *net)
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{
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struct ctl_table *tbl;
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tbl = net->core.sysctl_hdr->ctl_table_arg;
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unregister_net_sysctl_table(net->core.sysctl_hdr);
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BUG_ON(tbl == netns_core_table);
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kfree(tbl);
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}
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static __net_initdata struct pernet_operations sysctl_core_ops = {
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.init = sysctl_core_net_init,
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.exit = sysctl_core_net_exit,
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};
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static __init int sysctl_core_init(void)
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{
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static struct ctl_table empty[1];
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register_sysctl_paths(net_core_path, empty);
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register_net_sysctl_rotable(net_core_path, net_core_table);
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return register_pernet_subsys(&sysctl_core_ops);
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}
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fs_initcall(sysctl_core_init);
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