![Dmytro Linkin](/assets/img/avatar_default.png)
Currently init call of all actions (except ipt) init their 'parm'
structure as a direct pointer to nla data in skb. This leads to race
condition when some of the filter actions were initialized successfully
(and were assigned with idr action index that was written directly
into nla data), but then were deleted and retried (due to following
action module missing or classifier-initiated retry), in which case
action init code tries to insert action to idr with index that was
assigned on previous iteration. During retry the index can be reused
by another action that was inserted concurrently, which causes
unintended action sharing between filters.
To fix described race condition, save action idr index to temporary
stack-allocated variable instead on nla data.
Fixes: 0190c1d452
("net: sched: atomically check-allocate action")
Signed-off-by: Dmytro Linkin <dmitrolin@mellanox.com>
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
299 lines
7.5 KiB
C
299 lines
7.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* net/sched/act_sample.c - Packet sampling tc action
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* Copyright (c) 2017 Yotam Gigi <yotamg@mellanox.com>
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/string.h>
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#include <linux/errno.h>
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#include <linux/skbuff.h>
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#include <linux/rtnetlink.h>
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/gfp.h>
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#include <net/net_namespace.h>
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#include <net/netlink.h>
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#include <net/pkt_sched.h>
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#include <linux/tc_act/tc_sample.h>
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#include <net/tc_act/tc_sample.h>
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#include <net/psample.h>
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#include <net/pkt_cls.h>
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#include <linux/if_arp.h>
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static unsigned int sample_net_id;
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static struct tc_action_ops act_sample_ops;
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static const struct nla_policy sample_policy[TCA_SAMPLE_MAX + 1] = {
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[TCA_SAMPLE_PARMS] = { .len = sizeof(struct tc_sample) },
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[TCA_SAMPLE_RATE] = { .type = NLA_U32 },
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[TCA_SAMPLE_TRUNC_SIZE] = { .type = NLA_U32 },
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[TCA_SAMPLE_PSAMPLE_GROUP] = { .type = NLA_U32 },
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};
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static int tcf_sample_init(struct net *net, struct nlattr *nla,
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struct nlattr *est, struct tc_action **a, int ovr,
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int bind, bool rtnl_held, struct tcf_proto *tp,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, sample_net_id);
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struct nlattr *tb[TCA_SAMPLE_MAX + 1];
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struct psample_group *psample_group;
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u32 psample_group_num, rate, index;
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struct tcf_chain *goto_ch = NULL;
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struct tc_sample *parm;
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struct tcf_sample *s;
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bool exists = false;
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int ret, err;
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if (!nla)
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return -EINVAL;
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ret = nla_parse_nested_deprecated(tb, TCA_SAMPLE_MAX, nla,
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sample_policy, NULL);
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if (ret < 0)
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return ret;
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if (!tb[TCA_SAMPLE_PARMS] || !tb[TCA_SAMPLE_RATE] ||
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!tb[TCA_SAMPLE_PSAMPLE_GROUP])
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return -EINVAL;
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parm = nla_data(tb[TCA_SAMPLE_PARMS]);
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index = parm->index;
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err = tcf_idr_check_alloc(tn, &index, a, bind);
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if (err < 0)
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return err;
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exists = err;
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if (exists && bind)
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return 0;
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if (!exists) {
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ret = tcf_idr_create(tn, index, est, a,
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&act_sample_ops, bind, true);
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if (ret) {
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tcf_idr_cleanup(tn, index);
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return ret;
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}
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ret = ACT_P_CREATED;
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} else if (!ovr) {
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tcf_idr_release(*a, bind);
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return -EEXIST;
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}
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err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
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if (err < 0)
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goto release_idr;
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rate = nla_get_u32(tb[TCA_SAMPLE_RATE]);
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if (!rate) {
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NL_SET_ERR_MSG(extack, "invalid sample rate");
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err = -EINVAL;
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goto put_chain;
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}
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psample_group_num = nla_get_u32(tb[TCA_SAMPLE_PSAMPLE_GROUP]);
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psample_group = psample_group_get(net, psample_group_num);
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if (!psample_group) {
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err = -ENOMEM;
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goto put_chain;
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}
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s = to_sample(*a);
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spin_lock_bh(&s->tcf_lock);
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goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
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s->rate = rate;
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s->psample_group_num = psample_group_num;
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RCU_INIT_POINTER(s->psample_group, psample_group);
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if (tb[TCA_SAMPLE_TRUNC_SIZE]) {
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s->truncate = true;
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s->trunc_size = nla_get_u32(tb[TCA_SAMPLE_TRUNC_SIZE]);
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}
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spin_unlock_bh(&s->tcf_lock);
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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if (ret == ACT_P_CREATED)
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tcf_idr_insert(tn, *a);
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return ret;
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put_chain:
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if (goto_ch)
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tcf_chain_put_by_act(goto_ch);
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release_idr:
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tcf_idr_release(*a, bind);
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return err;
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}
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static void tcf_sample_cleanup(struct tc_action *a)
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{
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struct tcf_sample *s = to_sample(a);
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struct psample_group *psample_group;
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/* last reference to action, no need to lock */
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psample_group = rcu_dereference_protected(s->psample_group, 1);
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RCU_INIT_POINTER(s->psample_group, NULL);
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if (psample_group)
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psample_group_put(psample_group);
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}
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static bool tcf_sample_dev_ok_push(struct net_device *dev)
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{
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switch (dev->type) {
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case ARPHRD_TUNNEL:
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case ARPHRD_TUNNEL6:
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case ARPHRD_SIT:
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case ARPHRD_IPGRE:
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case ARPHRD_VOID:
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case ARPHRD_NONE:
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return false;
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default:
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return true;
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}
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}
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static int tcf_sample_act(struct sk_buff *skb, const struct tc_action *a,
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struct tcf_result *res)
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{
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struct tcf_sample *s = to_sample(a);
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struct psample_group *psample_group;
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int retval;
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int size;
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int iif;
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int oif;
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tcf_lastuse_update(&s->tcf_tm);
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bstats_cpu_update(this_cpu_ptr(s->common.cpu_bstats), skb);
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retval = READ_ONCE(s->tcf_action);
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psample_group = rcu_dereference_bh(s->psample_group);
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/* randomly sample packets according to rate */
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if (psample_group && (prandom_u32() % s->rate == 0)) {
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if (!skb_at_tc_ingress(skb)) {
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iif = skb->skb_iif;
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oif = skb->dev->ifindex;
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} else {
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iif = skb->dev->ifindex;
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oif = 0;
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}
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/* on ingress, the mac header gets popped, so push it back */
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if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
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skb_push(skb, skb->mac_len);
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size = s->truncate ? s->trunc_size : skb->len;
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psample_sample_packet(psample_group, skb, size, iif, oif,
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s->rate);
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if (skb_at_tc_ingress(skb) && tcf_sample_dev_ok_push(skb->dev))
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skb_pull(skb, skb->mac_len);
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}
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return retval;
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}
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static int tcf_sample_dump(struct sk_buff *skb, struct tc_action *a,
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int bind, int ref)
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{
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unsigned char *b = skb_tail_pointer(skb);
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struct tcf_sample *s = to_sample(a);
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struct tc_sample opt = {
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.index = s->tcf_index,
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.refcnt = refcount_read(&s->tcf_refcnt) - ref,
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.bindcnt = atomic_read(&s->tcf_bindcnt) - bind,
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};
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struct tcf_t t;
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spin_lock_bh(&s->tcf_lock);
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opt.action = s->tcf_action;
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if (nla_put(skb, TCA_SAMPLE_PARMS, sizeof(opt), &opt))
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goto nla_put_failure;
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tcf_tm_dump(&t, &s->tcf_tm);
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if (nla_put_64bit(skb, TCA_SAMPLE_TM, sizeof(t), &t, TCA_SAMPLE_PAD))
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goto nla_put_failure;
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if (nla_put_u32(skb, TCA_SAMPLE_RATE, s->rate))
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goto nla_put_failure;
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if (s->truncate)
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if (nla_put_u32(skb, TCA_SAMPLE_TRUNC_SIZE, s->trunc_size))
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goto nla_put_failure;
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if (nla_put_u32(skb, TCA_SAMPLE_PSAMPLE_GROUP, s->psample_group_num))
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goto nla_put_failure;
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spin_unlock_bh(&s->tcf_lock);
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return skb->len;
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nla_put_failure:
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spin_unlock_bh(&s->tcf_lock);
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nlmsg_trim(skb, b);
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return -1;
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}
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static int tcf_sample_walker(struct net *net, struct sk_buff *skb,
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struct netlink_callback *cb, int type,
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const struct tc_action_ops *ops,
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struct netlink_ext_ack *extack)
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{
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struct tc_action_net *tn = net_generic(net, sample_net_id);
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return tcf_generic_walker(tn, skb, cb, type, ops, extack);
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}
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static int tcf_sample_search(struct net *net, struct tc_action **a, u32 index)
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{
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struct tc_action_net *tn = net_generic(net, sample_net_id);
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return tcf_idr_search(tn, a, index);
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}
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static struct tc_action_ops act_sample_ops = {
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.kind = "sample",
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.id = TCA_ID_SAMPLE,
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.owner = THIS_MODULE,
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.act = tcf_sample_act,
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.dump = tcf_sample_dump,
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.init = tcf_sample_init,
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.cleanup = tcf_sample_cleanup,
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.walk = tcf_sample_walker,
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.lookup = tcf_sample_search,
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.size = sizeof(struct tcf_sample),
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};
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static __net_init int sample_init_net(struct net *net)
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{
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struct tc_action_net *tn = net_generic(net, sample_net_id);
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return tc_action_net_init(tn, &act_sample_ops);
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}
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static void __net_exit sample_exit_net(struct list_head *net_list)
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{
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tc_action_net_exit(net_list, sample_net_id);
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}
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static struct pernet_operations sample_net_ops = {
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.init = sample_init_net,
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.exit_batch = sample_exit_net,
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.id = &sample_net_id,
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.size = sizeof(struct tc_action_net),
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};
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static int __init sample_init_module(void)
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{
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return tcf_register_action(&act_sample_ops, &sample_net_ops);
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}
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static void __exit sample_cleanup_module(void)
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{
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tcf_unregister_action(&act_sample_ops, &sample_net_ops);
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}
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module_init(sample_init_module);
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module_exit(sample_cleanup_module);
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MODULE_AUTHOR("Yotam Gigi <yotam.gi@gmail.com>");
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MODULE_DESCRIPTION("Packet sampling action");
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MODULE_LICENSE("GPL v2");
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