Contributors: 32
| Author |
Tokens |
Token Proportion |
Commits |
Commit Proportion |
| Patrick McHardy |
2610 |
72.22% |
6 |
8.11% |
| John Fastabend |
234 |
6.47% |
1 |
1.35% |
| Eric Dumazet |
231 |
6.39% |
8 |
10.81% |
| Américo Wang |
170 |
4.70% |
13 |
17.57% |
| Jiri Pirko |
94 |
2.60% |
10 |
13.51% |
| Eric W. Biedermann |
61 |
1.69% |
2 |
2.70% |
| David S. Miller |
48 |
1.33% |
1 |
1.35% |
| Changli Gao |
31 |
0.86% |
3 |
4.05% |
| Tom Herbert |
19 |
0.53% |
3 |
4.05% |
| Kees Cook |
14 |
0.39% |
1 |
1.35% |
| Vlad Buslov |
14 |
0.39% |
2 |
2.70% |
| Toke Höiland-Jörgensen |
12 |
0.33% |
1 |
1.35% |
| Alexander Aring |
10 |
0.28% |
3 |
4.05% |
| Thomas Graf |
8 |
0.22% |
1 |
1.35% |
| David Howells |
6 |
0.17% |
1 |
1.35% |
| Jakub Kiciński |
5 |
0.14% |
1 |
1.35% |
| Rami Rosen |
5 |
0.14% |
1 |
1.35% |
| Benjamin LaHaise |
5 |
0.14% |
1 |
1.35% |
| Arnaldo Carvalho de Melo |
4 |
0.11% |
1 |
1.35% |
| Pedro Tammela |
4 |
0.11% |
1 |
1.35% |
| Geliang Tang |
4 |
0.11% |
1 |
1.35% |
| Zhengchao Shao |
4 |
0.11% |
1 |
1.35% |
| Johannes Berg |
3 |
0.08% |
2 |
2.70% |
| Florian Westphal |
3 |
0.08% |
1 |
1.35% |
| Javier Martinez Canillas |
3 |
0.08% |
1 |
1.35% |
| Paul Gortmaker |
3 |
0.08% |
1 |
1.35% |
| Thomas Gleixner |
2 |
0.06% |
1 |
1.35% |
| Daniel Borkmann |
2 |
0.06% |
1 |
1.35% |
| Linus Torvalds (pre-git) |
2 |
0.06% |
1 |
1.35% |
| Linus Torvalds |
1 |
0.03% |
1 |
1.35% |
| Steven Rostedt |
1 |
0.03% |
1 |
1.35% |
| Michal Kubeček |
1 |
0.03% |
1 |
1.35% |
| Total |
3614 |
|
74 |
|
// SPDX-License-Identifier: GPL-2.0-or-later
/*
* net/sched/cls_flow.c Generic flow classifier
*
* Copyright (c) 2007, 2008 Patrick McHardy <kaber@trash.net>
*/
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/jhash.h>
#include <linux/random.h>
#include <linux/pkt_cls.h>
#include <linux/skbuff.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/if_vlan.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <net/inet_sock.h>
#include <net/pkt_cls.h>
#include <net/ip.h>
#include <net/route.h>
#include <net/flow_dissector.h>
#include <net/tc_wrapper.h>
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#include <net/netfilter/nf_conntrack.h>
#endif
struct flow_head {
struct list_head filters;
struct rcu_head rcu;
};
struct flow_filter {
struct list_head list;
struct tcf_exts exts;
struct tcf_ematch_tree ematches;
struct tcf_proto *tp;
struct timer_list perturb_timer;
u32 perturb_period;
u32 handle;
u32 nkeys;
u32 keymask;
u32 mode;
u32 mask;
u32 xor;
u32 rshift;
u32 addend;
u32 divisor;
u32 baseclass;
u32 hashrnd;
struct rcu_work rwork;
};
static inline u32 addr_fold(void *addr)
{
unsigned long a = (unsigned long)addr;
return (a & 0xFFFFFFFF) ^ (BITS_PER_LONG > 32 ? a >> 32 : 0);
}
static u32 flow_get_src(const struct sk_buff *skb, const struct flow_keys *flow)
{
__be32 src = flow_get_u32_src(flow);
if (src)
return ntohl(src);
return addr_fold(skb->sk);
}
static u32 flow_get_dst(const struct sk_buff *skb, const struct flow_keys *flow)
{
__be32 dst = flow_get_u32_dst(flow);
if (dst)
return ntohl(dst);
return addr_fold(skb_dst(skb)) ^ (__force u16)skb_protocol(skb, true);
}
static u32 flow_get_proto(const struct sk_buff *skb,
const struct flow_keys *flow)
{
return flow->basic.ip_proto;
}
static u32 flow_get_proto_src(const struct sk_buff *skb,
const struct flow_keys *flow)
{
if (flow->ports.ports)
return ntohs(flow->ports.src);
return addr_fold(skb->sk);
}
static u32 flow_get_proto_dst(const struct sk_buff *skb,
const struct flow_keys *flow)
{
if (flow->ports.ports)
return ntohs(flow->ports.dst);
return addr_fold(skb_dst(skb)) ^ (__force u16)skb_protocol(skb, true);
}
static u32 flow_get_iif(const struct sk_buff *skb)
{
return skb->skb_iif;
}
static u32 flow_get_priority(const struct sk_buff *skb)
{
return skb->priority;
}
static u32 flow_get_mark(const struct sk_buff *skb)
{
return skb->mark;
}
static u32 flow_get_nfct(const struct sk_buff *skb)
{
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
return addr_fold(skb_nfct(skb));
#else
return 0;
#endif
}
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
#define CTTUPLE(skb, member) \
({ \
enum ip_conntrack_info ctinfo; \
const struct nf_conn *ct = nf_ct_get(skb, &ctinfo); \
if (ct == NULL) \
goto fallback; \
ct->tuplehash[CTINFO2DIR(ctinfo)].tuple.member; \
})
#else
#define CTTUPLE(skb, member) \
({ \
goto fallback; \
0; \
})
#endif
static u32 flow_get_nfct_src(const struct sk_buff *skb,
const struct flow_keys *flow)
{
switch (skb_protocol(skb, true)) {
case htons(ETH_P_IP):
return ntohl(CTTUPLE(skb, src.u3.ip));
case htons(ETH_P_IPV6):
return ntohl(CTTUPLE(skb, src.u3.ip6[3]));
}
fallback:
return flow_get_src(skb, flow);
}
static u32 flow_get_nfct_dst(const struct sk_buff *skb,
const struct flow_keys *flow)
{
switch (skb_protocol(skb, true)) {
case htons(ETH_P_IP):
return ntohl(CTTUPLE(skb, dst.u3.ip));
case htons(ETH_P_IPV6):
return ntohl(CTTUPLE(skb, dst.u3.ip6[3]));
}
fallback:
return flow_get_dst(skb, flow);
}
static u32 flow_get_nfct_proto_src(const struct sk_buff *skb,
const struct flow_keys *flow)
{
return ntohs(CTTUPLE(skb, src.u.all));
fallback:
return flow_get_proto_src(skb, flow);
}
static u32 flow_get_nfct_proto_dst(const struct sk_buff *skb,
const struct flow_keys *flow)
{
return ntohs(CTTUPLE(skb, dst.u.all));
fallback:
return flow_get_proto_dst(skb, flow);
}
static u32 flow_get_rtclassid(const struct sk_buff *skb)
{
#ifdef CONFIG_IP_ROUTE_CLASSID
if (skb_dst(skb))
return skb_dst(skb)->tclassid;
#endif
return 0;
}
static u32 flow_get_skuid(const struct sk_buff *skb)
{
struct sock *sk = skb_to_full_sk(skb);
if (sk && sk->sk_socket && sk->sk_socket->file) {
kuid_t skuid = sk->sk_socket->file->f_cred->fsuid;
return from_kuid(&init_user_ns, skuid);
}
return 0;
}
static u32 flow_get_skgid(const struct sk_buff *skb)
{
struct sock *sk = skb_to_full_sk(skb);
if (sk && sk->sk_socket && sk->sk_socket->file) {
kgid_t skgid = sk->sk_socket->file->f_cred->fsgid;
return from_kgid(&init_user_ns, skgid);
}
return 0;
}
static u32 flow_get_vlan_tag(const struct sk_buff *skb)
{
u16 tag;
if (vlan_get_tag(skb, &tag) < 0)
return 0;
return tag & VLAN_VID_MASK;
}
static u32 flow_get_rxhash(struct sk_buff *skb)
{
return skb_get_hash(skb);
}
static u32 flow_key_get(struct sk_buff *skb, int key, struct flow_keys *flow)
{
switch (key) {
case FLOW_KEY_SRC:
return flow_get_src(skb, flow);
case FLOW_KEY_DST:
return flow_get_dst(skb, flow);
case FLOW_KEY_PROTO:
return flow_get_proto(skb, flow);
case FLOW_KEY_PROTO_SRC:
return flow_get_proto_src(skb, flow);
case FLOW_KEY_PROTO_DST:
return flow_get_proto_dst(skb, flow);
case FLOW_KEY_IIF:
return flow_get_iif(skb);
case FLOW_KEY_PRIORITY:
return flow_get_priority(skb);
case FLOW_KEY_MARK:
return flow_get_mark(skb);
case FLOW_KEY_NFCT:
return flow_get_nfct(skb);
case FLOW_KEY_NFCT_SRC:
return flow_get_nfct_src(skb, flow);
case FLOW_KEY_NFCT_DST:
return flow_get_nfct_dst(skb, flow);
case FLOW_KEY_NFCT_PROTO_SRC:
return flow_get_nfct_proto_src(skb, flow);
case FLOW_KEY_NFCT_PROTO_DST:
return flow_get_nfct_proto_dst(skb, flow);
case FLOW_KEY_RTCLASSID:
return flow_get_rtclassid(skb);
case FLOW_KEY_SKUID:
return flow_get_skuid(skb);
case FLOW_KEY_SKGID:
return flow_get_skgid(skb);
case FLOW_KEY_VLAN_TAG:
return flow_get_vlan_tag(skb);
case FLOW_KEY_RXHASH:
return flow_get_rxhash(skb);
default:
WARN_ON(1);
return 0;
}
}
#define FLOW_KEYS_NEEDED ((1 << FLOW_KEY_SRC) | \
(1 << FLOW_KEY_DST) | \
(1 << FLOW_KEY_PROTO) | \
(1 << FLOW_KEY_PROTO_SRC) | \
(1 << FLOW_KEY_PROTO_DST) | \
(1 << FLOW_KEY_NFCT_SRC) | \
(1 << FLOW_KEY_NFCT_DST) | \
(1 << FLOW_KEY_NFCT_PROTO_SRC) | \
(1 << FLOW_KEY_NFCT_PROTO_DST))
TC_INDIRECT_SCOPE int flow_classify(struct sk_buff *skb,
const struct tcf_proto *tp,
struct tcf_result *res)
{
struct flow_head *head = rcu_dereference_bh(tp->root);
struct flow_filter *f;
u32 keymask;
u32 classid;
unsigned int n, key;
int r;
list_for_each_entry_rcu(f, &head->filters, list) {
u32 keys[FLOW_KEY_MAX + 1];
struct flow_keys flow_keys;
if (!tcf_em_tree_match(skb, &f->ematches, NULL))
continue;
keymask = f->keymask;
if (keymask & FLOW_KEYS_NEEDED)
skb_flow_dissect_flow_keys(skb, &flow_keys, 0);
for (n = 0; n < f->nkeys; n++) {
key = ffs(keymask) - 1;
keymask &= ~(1 << key);
keys[n] = flow_key_get(skb, key, &flow_keys);
}
if (f->mode == FLOW_MODE_HASH)
classid = jhash2(keys, f->nkeys, f->hashrnd);
else {
classid = keys[0];
classid = (classid & f->mask) ^ f->xor;
classid = (classid >> f->rshift) + f->addend;
}
if (f->divisor)
classid %= f->divisor;
res->class = 0;
res->classid = TC_H_MAKE(f->baseclass, f->baseclass + classid);
r = tcf_exts_exec(skb, &f->exts, res);
if (r < 0)
continue;
return r;
}
return -1;
}
static void flow_perturbation(struct timer_list *t)
{
struct flow_filter *f = from_timer(f, t, perturb_timer);
get_random_bytes(&f->hashrnd, 4);
if (f->perturb_period)
mod_timer(&f->perturb_timer, jiffies + f->perturb_period);
}
static const struct nla_policy flow_policy[TCA_FLOW_MAX + 1] = {
[TCA_FLOW_KEYS] = { .type = NLA_U32 },
[TCA_FLOW_MODE] = { .type = NLA_U32 },
[TCA_FLOW_BASECLASS] = { .type = NLA_U32 },
[TCA_FLOW_RSHIFT] = { .type = NLA_U32 },
[TCA_FLOW_ADDEND] = { .type = NLA_U32 },
[TCA_FLOW_MASK] = { .type = NLA_U32 },
[TCA_FLOW_XOR] = { .type = NLA_U32 },
[TCA_FLOW_DIVISOR] = { .type = NLA_U32 },
[TCA_FLOW_ACT] = { .type = NLA_NESTED },
[TCA_FLOW_POLICE] = { .type = NLA_NESTED },
[TCA_FLOW_EMATCHES] = { .type = NLA_NESTED },
[TCA_FLOW_PERTURB] = { .type = NLA_U32 },
};
static void __flow_destroy_filter(struct flow_filter *f)
{
timer_shutdown_sync(&f->perturb_timer);
tcf_exts_destroy(&f->exts);
tcf_em_tree_destroy(&f->ematches);
tcf_exts_put_net(&f->exts);
kfree(f);
}
static void flow_destroy_filter_work(struct work_struct *work)
{
struct flow_filter *f = container_of(to_rcu_work(work),
struct flow_filter,
rwork);
rtnl_lock();
__flow_destroy_filter(f);
rtnl_unlock();
}
static int flow_change(struct net *net, struct sk_buff *in_skb,
struct tcf_proto *tp, unsigned long base,
u32 handle, struct nlattr **tca,
void **arg, u32 flags,
struct netlink_ext_ack *extack)
{
struct flow_head *head = rtnl_dereference(tp->root);
struct flow_filter *fold, *fnew;
struct nlattr *opt = tca[TCA_OPTIONS];
struct nlattr *tb[TCA_FLOW_MAX + 1];
unsigned int nkeys = 0;
unsigned int perturb_period = 0;
u32 baseclass = 0;
u32 keymask = 0;
u32 mode;
int err;
if (opt == NULL)
return -EINVAL;
err = nla_parse_nested_deprecated(tb, TCA_FLOW_MAX, opt, flow_policy,
NULL);
if (err < 0)
return err;
if (tb[TCA_FLOW_BASECLASS]) {
baseclass = nla_get_u32(tb[TCA_FLOW_BASECLASS]);
if (TC_H_MIN(baseclass) == 0)
return -EINVAL;
}
if (tb[TCA_FLOW_KEYS]) {
keymask = nla_get_u32(tb[TCA_FLOW_KEYS]);
nkeys = hweight32(keymask);
if (nkeys == 0)
return -EINVAL;
if (fls(keymask) - 1 > FLOW_KEY_MAX)
return -EOPNOTSUPP;
if ((keymask & (FLOW_KEY_SKUID|FLOW_KEY_SKGID)) &&
sk_user_ns(NETLINK_CB(in_skb).sk) != &init_user_ns)
return -EOPNOTSUPP;
}
fnew = kzalloc(sizeof(*fnew), GFP_KERNEL);
if (!fnew)
return -ENOBUFS;
err = tcf_em_tree_validate(tp, tb[TCA_FLOW_EMATCHES], &fnew->ematches);
if (err < 0)
goto err1;
err = tcf_exts_init(&fnew->exts, net, TCA_FLOW_ACT, TCA_FLOW_POLICE);
if (err < 0)
goto err2;
err = tcf_exts_validate(net, tp, tb, tca[TCA_RATE], &fnew->exts, flags,
extack);
if (err < 0)
goto err2;
fold = *arg;
if (fold) {
err = -EINVAL;
if (fold->handle != handle && handle)
goto err2;
/* Copy fold into fnew */
fnew->tp = fold->tp;
fnew->handle = fold->handle;
fnew->nkeys = fold->nkeys;
fnew->keymask = fold->keymask;
fnew->mode = fold->mode;
fnew->mask = fold->mask;
fnew->xor = fold->xor;
fnew->rshift = fold->rshift;
fnew->addend = fold->addend;
fnew->divisor = fold->divisor;
fnew->baseclass = fold->baseclass;
fnew->hashrnd = fold->hashrnd;
mode = fold->mode;
if (tb[TCA_FLOW_MODE])
mode = nla_get_u32(tb[TCA_FLOW_MODE]);
if (mode != FLOW_MODE_HASH && nkeys > 1)
goto err2;
if (mode == FLOW_MODE_HASH)
perturb_period = fold->perturb_period;
if (tb[TCA_FLOW_PERTURB]) {
if (mode != FLOW_MODE_HASH)
goto err2;
perturb_period = nla_get_u32(tb[TCA_FLOW_PERTURB]) * HZ;
}
} else {
err = -EINVAL;
if (!handle)
goto err2;
if (!tb[TCA_FLOW_KEYS])
goto err2;
mode = FLOW_MODE_MAP;
if (tb[TCA_FLOW_MODE])
mode = nla_get_u32(tb[TCA_FLOW_MODE]);
if (mode != FLOW_MODE_HASH && nkeys > 1)
goto err2;
if (tb[TCA_FLOW_PERTURB]) {
if (mode != FLOW_MODE_HASH)
goto err2;
perturb_period = nla_get_u32(tb[TCA_FLOW_PERTURB]) * HZ;
}
if (TC_H_MAJ(baseclass) == 0) {
struct Qdisc *q = tcf_block_q(tp->chain->block);
baseclass = TC_H_MAKE(q->handle, baseclass);
}
if (TC_H_MIN(baseclass) == 0)
baseclass = TC_H_MAKE(baseclass, 1);
fnew->handle = handle;
fnew->mask = ~0U;
fnew->tp = tp;
get_random_bytes(&fnew->hashrnd, 4);
}
timer_setup(&fnew->perturb_timer, flow_perturbation, TIMER_DEFERRABLE);
tcf_block_netif_keep_dst(tp->chain->block);
if (tb[TCA_FLOW_KEYS]) {
fnew->keymask = keymask;
fnew->nkeys = nkeys;
}
fnew->mode = mode;
if (tb[TCA_FLOW_MASK])
fnew->mask = nla_get_u32(tb[TCA_FLOW_MASK]);
if (tb[TCA_FLOW_XOR])
fnew->xor = nla_get_u32(tb[TCA_FLOW_XOR]);
if (tb[TCA_FLOW_RSHIFT])
fnew->rshift = nla_get_u32(tb[TCA_FLOW_RSHIFT]);
if (tb[TCA_FLOW_ADDEND])
fnew->addend = nla_get_u32(tb[TCA_FLOW_ADDEND]);
if (tb[TCA_FLOW_DIVISOR])
fnew->divisor = nla_get_u32(tb[TCA_FLOW_DIVISOR]);
if (baseclass)
fnew->baseclass = baseclass;
fnew->perturb_period = perturb_period;
if (perturb_period)
mod_timer(&fnew->perturb_timer, jiffies + perturb_period);
if (!*arg)
list_add_tail_rcu(&fnew->list, &head->filters);
else
list_replace_rcu(&fold->list, &fnew->list);
*arg = fnew;
if (fold) {
tcf_exts_get_net(&fold->exts);
tcf_queue_work(&fold->rwork, flow_destroy_filter_work);
}
return 0;
err2:
tcf_exts_destroy(&fnew->exts);
tcf_em_tree_destroy(&fnew->ematches);
err1:
kfree(fnew);
return err;
}
static int flow_delete(struct tcf_proto *tp, void *arg, bool *last,
bool rtnl_held, struct netlink_ext_ack *extack)
{
struct flow_head *head = rtnl_dereference(tp->root);
struct flow_filter *f = arg;
list_del_rcu(&f->list);
tcf_exts_get_net(&f->exts);
tcf_queue_work(&f->rwork, flow_destroy_filter_work);
*last = list_empty(&head->filters);
return 0;
}
static int flow_init(struct tcf_proto *tp)
{
struct flow_head *head;
head = kzalloc(sizeof(*head), GFP_KERNEL);
if (head == NULL)
return -ENOBUFS;
INIT_LIST_HEAD(&head->filters);
rcu_assign_pointer(tp->root, head);
return 0;
}
static void flow_destroy(struct tcf_proto *tp, bool rtnl_held,
struct netlink_ext_ack *extack)
{
struct flow_head *head = rtnl_dereference(tp->root);
struct flow_filter *f, *next;
list_for_each_entry_safe(f, next, &head->filters, list) {
list_del_rcu(&f->list);
if (tcf_exts_get_net(&f->exts))
tcf_queue_work(&f->rwork, flow_destroy_filter_work);
else
__flow_destroy_filter(f);
}
kfree_rcu(head, rcu);
}
static void *flow_get(struct tcf_proto *tp, u32 handle)
{
struct flow_head *head = rtnl_dereference(tp->root);
struct flow_filter *f;
list_for_each_entry(f, &head->filters, list)
if (f->handle == handle)
return f;
return NULL;
}
static int flow_dump(struct net *net, struct tcf_proto *tp, void *fh,
struct sk_buff *skb, struct tcmsg *t, bool rtnl_held)
{
struct flow_filter *f = fh;
struct nlattr *nest;
if (f == NULL)
return skb->len;
t->tcm_handle = f->handle;
nest = nla_nest_start_noflag(skb, TCA_OPTIONS);
if (nest == NULL)
goto nla_put_failure;
if (nla_put_u32(skb, TCA_FLOW_KEYS, f->keymask) ||
nla_put_u32(skb, TCA_FLOW_MODE, f->mode))
goto nla_put_failure;
if (f->mask != ~0 || f->xor != 0) {
if (nla_put_u32(skb, TCA_FLOW_MASK, f->mask) ||
nla_put_u32(skb, TCA_FLOW_XOR, f->xor))
goto nla_put_failure;
}
if (f->rshift &&
nla_put_u32(skb, TCA_FLOW_RSHIFT, f->rshift))
goto nla_put_failure;
if (f->addend &&
nla_put_u32(skb, TCA_FLOW_ADDEND, f->addend))
goto nla_put_failure;
if (f->divisor &&
nla_put_u32(skb, TCA_FLOW_DIVISOR, f->divisor))
goto nla_put_failure;
if (f->baseclass &&
nla_put_u32(skb, TCA_FLOW_BASECLASS, f->baseclass))
goto nla_put_failure;
if (f->perturb_period &&
nla_put_u32(skb, TCA_FLOW_PERTURB, f->perturb_period / HZ))
goto nla_put_failure;
if (tcf_exts_dump(skb, &f->exts) < 0)
goto nla_put_failure;
#ifdef CONFIG_NET_EMATCH
if (f->ematches.hdr.nmatches &&
tcf_em_tree_dump(skb, &f->ematches, TCA_FLOW_EMATCHES) < 0)
goto nla_put_failure;
#endif
nla_nest_end(skb, nest);
if (tcf_exts_dump_stats(skb, &f->exts) < 0)
goto nla_put_failure;
return skb->len;
nla_put_failure:
nla_nest_cancel(skb, nest);
return -1;
}
static void flow_walk(struct tcf_proto *tp, struct tcf_walker *arg,
bool rtnl_held)
{
struct flow_head *head = rtnl_dereference(tp->root);
struct flow_filter *f;
list_for_each_entry(f, &head->filters, list) {
if (!tc_cls_stats_dump(tp, arg, f))
break;
}
}
static struct tcf_proto_ops cls_flow_ops __read_mostly = {
.kind = "flow",
.classify = flow_classify,
.init = flow_init,
.destroy = flow_destroy,
.change = flow_change,
.delete = flow_delete,
.get = flow_get,
.dump = flow_dump,
.walk = flow_walk,
.owner = THIS_MODULE,
};
static int __init cls_flow_init(void)
{
return register_tcf_proto_ops(&cls_flow_ops);
}
static void __exit cls_flow_exit(void)
{
unregister_tcf_proto_ops(&cls_flow_ops);
}
module_init(cls_flow_init);
module_exit(cls_flow_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>");
MODULE_DESCRIPTION("TC flow classifier");