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net: sched: cls_bpf: add BPF-based classifier

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This work contains a lightweight BPF-based traffic classifier that can
serve as a flexible alternative to ematch-based tree classification, i.e.
now that BPF filter engine can also be JITed in the kernel. Naturally, tc
actions and policies are supported as well with cls_bpf. Multiple BPF
programs/filter can be attached for a class, or they can just as well be
written within a single BPF program, that's really up to the user how he
wishes to run/optimize the code, e.g. also for inversion of verdicts etc.
The notion of a BPF program's return/exit codes is being kept as follows:

     0: No match
    -1: Select classid given in "tc filter ..." command
  else: flowid, overwrite the default one

As a minimal usage example with iproute2, we use a 3 band prio root qdisc
on a router with sfq each as leave, and assign ssh and icmp bpf-based
filters to band 1, http traffic to band 2 and the rest to band 3. For the
first two bands we load the bytecode from a file, in the 2nd we load it
inline as an example:

echo 1 > /proc/sys/net/core/bpf_jit_enable

tc qdisc del dev em1 root
tc qdisc add dev em1 root handle 1: prio bands 3 priomap 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1

tc qdisc add dev em1 parent 1:1 sfq perturb 16
tc qdisc add dev em1 parent 1:2 sfq perturb 16
tc qdisc add dev em1 parent 1:3 sfq perturb 16

tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/ssh.bpf flowid 1:1
tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/icmp.bpf flowid 1:1
tc filter add dev em1 parent 1: bpf run bytecode-file /etc/tc/http.bpf flowid 1:2
tc filter add dev em1 parent 1: bpf run bytecode "`bpfc -f tc -i misc.ops`" flowid 1:3

BPF programs can be easily created and passed to tc, either as inline
'bytecode' or 'bytecode-file'. There are a couple of front-ends that can
compile opcodes, for example:

1) People familiar with tcpdump-like filters:

   tcpdump -iem1 -ddd port 22 | tr '\n' ',' > /etc/tc/ssh.bpf

2) People that want to low-level program their filters or use BPF
   extensions that lack support by libpcap's compiler:

   bpfc -f tc -i ssh.ops > /etc/tc/ssh.bpf

   ssh.ops example code:
   ldh [12]
   jne #0x800, drop
   ldb [23]
   jneq #6, drop
   ldh [20]
   jset #0x1fff, drop
   ldxb 4 * ([14] & 0xf)
   ldh [%x + 14]
   jeq #0x16, pass
   ldh [%x + 16]
   jne #0x16, drop
   pass: ret #-1
   drop: ret #0

It was chosen to load bytecode into tc, since the reverse operation,
tc filter list dev em1, is then able to show the exact commands again.
Possible follow-up work could also include a small expression compiler
for iproute2. Tested with the help of bmon. This idea came up during
the Netfilter Workshop 2013 in Copenhagen. Also thanks to feedback from
Eric Dumazet!

Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Daniel Borkmann 2013-10-28 16:43:02 +01:00 committed by David S. Miller
parent d549c76bcc
commit 7d1d65cb84
4 changed files with 410 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

14
include/uapi/linux/pkt_cls.h
View File

@ -388,6 +388,20 @@ enum {
#define TCA_CGROUP_MAX (__TCA_CGROUP_MAX - 1)
/* BPF classifier */
enum {
TCA_BPF_UNSPEC,
TCA_BPF_ACT,
TCA_BPF_POLICE,
TCA_BPF_CLASSID,
TCA_BPF_OPS_LEN,
TCA_BPF_OPS,
__TCA_BPF_MAX,
};
#define TCA_BPF_MAX (__TCA_BPF_MAX - 1)
/* Extended Matches */
struct tcf_ematch_tree_hdr {

10
net/sched/Kconfig
View File

@ -443,6 +443,16 @@ config NET_CLS_CGROUP
To compile this code as a module, choose M here: the
module will be called cls_cgroup.
config NET_CLS_BPF
tristate "BPF-based classifier"
select NET_CLS
---help---
If you say Y here, you will be able to classify packets based on
programmable BPF (JIT'ed) filters as an alternative to ematches.
To compile this code as a module, choose M here: the module will
be called cls_bpf.
config NET_EMATCH
bool "Extended Matches"
select NET_CLS

1
net/sched/Makefile
View File

@ -50,6 +50,7 @@ obj-$(CONFIG_NET_CLS_RSVP6) += cls_rsvp6.o
obj-$(CONFIG_NET_CLS_BASIC) += cls_basic.o
obj-$(CONFIG_NET_CLS_FLOW) += cls_flow.o
obj-$(CONFIG_NET_CLS_CGROUP) += cls_cgroup.o
obj-$(CONFIG_NET_CLS_BPF) += cls_bpf.o
obj-$(CONFIG_NET_EMATCH) += ematch.o
obj-$(CONFIG_NET_EMATCH_CMP) += em_cmp.o
obj-$(CONFIG_NET_EMATCH_NBYTE) += em_nbyte.o

385
net/sched/cls_bpf.c Normal file
View File

@ -0,0 +1,385 @@
/*
* Berkeley Packet Filter based traffic classifier
*
* Might be used to classify traffic through flexible, user-defined and
* possibly JIT-ed BPF filters for traffic control as an alternative to
* ematches.
*
* (C) 2013 Daniel Borkmann <dborkman@redhat.com>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/module.h>
#include <linux/types.h>
#include <linux/skbuff.h>
#include <linux/filter.h>
#include <net/rtnetlink.h>
#include <net/pkt_cls.h>
#include <net/sock.h>
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Daniel Borkmann <dborkman@redhat.com>");
MODULE_DESCRIPTION("TC BPF based classifier");
struct cls_bpf_head {
struct list_head plist;
u32 hgen;
};
struct cls_bpf_prog {
struct sk_filter *filter;
struct sock_filter *bpf_ops;
struct tcf_exts exts;
struct tcf_result res;
struct list_head link;
u32 handle;
u16 bpf_len;
};
static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
[TCA_BPF_CLASSID] = { .type = NLA_U32 },
[TCA_BPF_OPS_LEN] = { .type = NLA_U16 },
[TCA_BPF_OPS] = { .type = NLA_BINARY,
.len = sizeof(struct sock_filter) * BPF_MAXINSNS },
};
static const struct tcf_ext_map bpf_ext_map = {
.action = TCA_BPF_ACT,
.police = TCA_BPF_POLICE,
};
static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog;
int ret;
list_for_each_entry(prog, &head->plist, link) {
int filter_res = SK_RUN_FILTER(prog->filter, skb);
if (filter_res == 0)
continue;
*res = prog->res;
if (filter_res != -1)
res->classid = filter_res;
ret = tcf_exts_exec(skb, &prog->exts, res);
if (ret < 0)
continue;
return ret;
}
return -1;
}
static int cls_bpf_init(struct tcf_proto *tp)
{
struct cls_bpf_head *head;
head = kzalloc(sizeof(*head), GFP_KERNEL);
if (head == NULL)
return -ENOBUFS;
INIT_LIST_HEAD(&head->plist);
tp->root = head;
return 0;
}
static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
{
tcf_unbind_filter(tp, &prog->res);
tcf_exts_destroy(tp, &prog->exts);
sk_unattached_filter_destroy(prog->filter);
kfree(prog->bpf_ops);
kfree(prog);
}
static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog, *todel = (struct cls_bpf_prog *) arg;
list_for_each_entry(prog, &head->plist, link) {
if (prog == todel) {
tcf_tree_lock(tp);
list_del(&prog->link);
tcf_tree_unlock(tp);
cls_bpf_delete_prog(tp, prog);
return 0;
}
}
return -ENOENT;
}
static void cls_bpf_destroy(struct tcf_proto *tp)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog, *tmp;
list_for_each_entry_safe(prog, tmp, &head->plist, link) {
list_del(&prog->link);
cls_bpf_delete_prog(tp, prog);
}
kfree(head);
}
static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog;
unsigned long ret = 0UL;
if (head == NULL)
return 0UL;
list_for_each_entry(prog, &head->plist, link) {
if (prog->handle == handle) {
ret = (unsigned long) prog;
break;
}
}
return ret;
}
static void cls_bpf_put(struct tcf_proto *tp, unsigned long f)
{
}
static int cls_bpf_modify_existing(struct net *net, struct tcf_proto *tp,
struct cls_bpf_prog *prog,
unsigned long base, struct nlattr **tb,
struct nlattr *est)
{
struct sock_filter *bpf_ops, *bpf_old;
struct tcf_exts exts;
struct sock_fprog tmp;
struct sk_filter *fp, *fp_old;
u16 bpf_size, bpf_len;
u32 classid;
int ret;
if (!tb[TCA_BPF_OPS_LEN] || !tb[TCA_BPF_OPS] || !tb[TCA_BPF_CLASSID])
return -EINVAL;
ret = tcf_exts_validate(net, tp, tb, est, &exts, &bpf_ext_map);
if (ret < 0)
return ret;
classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
bpf_len = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
if (bpf_len > BPF_MAXINSNS || bpf_len == 0) {
ret = -EINVAL;
goto errout;
}
bpf_size = bpf_len * sizeof(*bpf_ops);
bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
if (bpf_ops == NULL) {
ret = -ENOMEM;
goto errout;
}
memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
tmp.len = bpf_len;
tmp.filter = (struct sock_filter __user *) bpf_ops;
ret = sk_unattached_filter_create(&fp, &tmp);
if (ret)
goto errout_free;
tcf_tree_lock(tp);
fp_old = prog->filter;
bpf_old = prog->bpf_ops;
prog->bpf_len = bpf_len;
prog->bpf_ops = bpf_ops;
prog->filter = fp;
prog->res.classid = classid;
tcf_tree_unlock(tp);
tcf_bind_filter(tp, &prog->res, base);
tcf_exts_change(tp, &prog->exts, &exts);
if (fp_old)
sk_unattached_filter_destroy(fp_old);
if (bpf_old)
kfree(bpf_old);
return 0;
errout_free:
kfree(bpf_ops);
errout:
tcf_exts_destroy(tp, &exts);
return ret;
}
static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
struct cls_bpf_head *head)
{
unsigned int i = 0x80000000;
do {
if (++head->hgen == 0x7FFFFFFF)
head->hgen = 1;
} while (--i > 0 && cls_bpf_get(tp, head->hgen));
if (i == 0)
pr_err("Insufficient number of handles\n");
return i;
}
static int cls_bpf_change(struct net *net, struct sk_buff *in_skb,
struct tcf_proto *tp, unsigned long base,
u32 handle, struct nlattr **tca,
unsigned long *arg)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog = (struct cls_bpf_prog *) *arg;
struct nlattr *tb[TCA_BPF_MAX + 1];
int ret;
if (tca[TCA_OPTIONS] == NULL)
return -EINVAL;
ret = nla_parse_nested(tb, TCA_BPF_MAX, tca[TCA_OPTIONS], bpf_policy);
if (ret < 0)
return ret;
if (prog != NULL) {
if (handle && prog->handle != handle)
return -EINVAL;
return cls_bpf_modify_existing(net, tp, prog, base, tb,
tca[TCA_RATE]);
}
prog = kzalloc(sizeof(*prog), GFP_KERNEL);
if (prog == NULL)
return -ENOBUFS;
if (handle == 0)
prog->handle = cls_bpf_grab_new_handle(tp, head);
else
prog->handle = handle;
if (prog->handle == 0) {
ret = -EINVAL;
goto errout;
}
ret = cls_bpf_modify_existing(net, tp, prog, base, tb, tca[TCA_RATE]);
if (ret < 0)
goto errout;
tcf_tree_lock(tp);
list_add(&prog->link, &head->plist);
tcf_tree_unlock(tp);
*arg = (unsigned long) prog;
return 0;
errout:
if (*arg == 0UL && prog)
kfree(prog);
return ret;
}
static int cls_bpf_dump(struct tcf_proto *tp, unsigned long fh,
struct sk_buff *skb, struct tcmsg *tm)
{
struct cls_bpf_prog *prog = (struct cls_bpf_prog *) fh;
struct nlattr *nest, *nla;
if (prog == NULL)
return skb->len;
tm->tcm_handle = prog->handle;
nest = nla_nest_start(skb, TCA_OPTIONS);
if (nest == NULL)
goto nla_put_failure;
if (nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
goto nla_put_failure;
if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_len))
goto nla_put_failure;
nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_len *
sizeof(struct sock_filter));
if (nla == NULL)
goto nla_put_failure;
memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
if (tcf_exts_dump(skb, &prog->exts, &bpf_ext_map) < 0)
goto nla_put_failure;
nla_nest_end(skb, nest);
if (tcf_exts_dump_stats(skb, &prog->exts, &bpf_ext_map) < 0)
goto nla_put_failure;
return skb->len;
nla_put_failure:
nla_nest_cancel(skb, nest);
return -1;
}
static void cls_bpf_walk(struct tcf_proto *tp, struct tcf_walker *arg)
{
struct cls_bpf_head *head = tp->root;
struct cls_bpf_prog *prog;
list_for_each_entry(prog, &head->plist, link) {
if (arg->count < arg->skip)
goto skip;
if (arg->fn(tp, (unsigned long) prog, arg) < 0) {
arg->stop = 1;
break;
}
skip:
arg->count++;
}
}
static struct tcf_proto_ops cls_bpf_ops __read_mostly = {
.kind = "bpf",
.owner = THIS_MODULE,
.classify = cls_bpf_classify,
.init = cls_bpf_init,
.destroy = cls_bpf_destroy,
.get = cls_bpf_get,
.put = cls_bpf_put,
.change = cls_bpf_change,
.delete = cls_bpf_delete,
.walk = cls_bpf_walk,
.dump = cls_bpf_dump,
};
static int __init cls_bpf_init_mod(void)
{
return register_tcf_proto_ops(&cls_bpf_ops);
}
static void __exit cls_bpf_exit_mod(void)
{
unregister_tcf_proto_ops(&cls_bpf_ops);
}
module_init(cls_bpf_init_mod);
module_exit(cls_bpf_exit_mod);