[PATCH net-next v2] net: sched: cls_bpf: add BPF-based classifier
From: Daniel Borkmann <hidden>
Date: 2013-10-28 15:43:39
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 <redacted>
Cc: Thomas Graf <tgraf@suug.ch>
---
v1->v2:
- Ok, applied Eric Dumazet's feedback with possibility to overwrite
default flowid
iproute2 part: http://patchwork.ozlabs.org/patch/286496/
include/uapi/linux/pkt_cls.h | 14 ++
net/sched/Kconfig | 10 ++
net/sched/Makefile | 1 +
net/sched/cls_bpf.c | 385 +++++++++++++++++++++++++++++++++++++++++++
4 files changed, 410 insertions(+)
create mode 100644 net/sched/cls_bpf.c
diff --git a/include/uapi/linux/pkt_cls.h b/include/uapi/linux/pkt_cls.h
index 082eafa..25731df 100644
--- a/include/uapi/linux/pkt_cls.h
+++ b/include/uapi/linux/pkt_cls.h@@ -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 {
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index c03a32a..ad1f1d8 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig@@ -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
diff --git a/net/sched/Makefile b/net/sched/Makefile
index e5f9abe..35fa47a 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile@@ -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
diff --git a/net/sched/cls_bpf.c b/net/sched/cls_bpf.c
new file mode 100644
index 0000000..1002a82
--- /dev/null
+++ b/net/sched/cls_bpf.c@@ -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);
--
1.8.3.1