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linux-next/net/sched/cls_bpf.c
Daniel Borkmann 5cf8ca0e47 cls_bpf: further limit exec opcodes subset
Jamal suggested to further limit the currently allowed subset of opcodes
that may be used by a direct action return code as the intention is not
to replace the full action engine, but rather to have a minimal set that
can be used in the fast-path on things like ingress for some features
that cls_bpf supports.

Classifiers can, of course, still be chained together that have direct
action mode with those that have a full exec pass. For more complex
scenarios that go beyond this minimal set here, the full tcf_exts_exec()
path must be used.

Suggested-by: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-09-23 14:29:02 -07:00

550 lines
12 KiB
C

/*
* 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 <linux/bpf.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");
#define CLS_BPF_NAME_LEN 256
struct cls_bpf_head {
struct list_head plist;
u32 hgen;
struct rcu_head rcu;
};
struct cls_bpf_prog {
struct bpf_prog *filter;
struct list_head link;
struct tcf_result res;
bool exts_integrated;
struct tcf_exts exts;
u32 handle;
union {
u32 bpf_fd;
u16 bpf_num_ops;
};
struct sock_filter *bpf_ops;
const char *bpf_name;
struct tcf_proto *tp;
struct rcu_head rcu;
};
static const struct nla_policy bpf_policy[TCA_BPF_MAX + 1] = {
[TCA_BPF_CLASSID] = { .type = NLA_U32 },
[TCA_BPF_FLAGS] = { .type = NLA_U32 },
[TCA_BPF_FD] = { .type = NLA_U32 },
[TCA_BPF_NAME] = { .type = NLA_NUL_STRING, .len = CLS_BPF_NAME_LEN },
[TCA_BPF_OPS_LEN] = { .type = NLA_U16 },
[TCA_BPF_OPS] = { .type = NLA_BINARY,
.len = sizeof(struct sock_filter) * BPF_MAXINSNS },
};
static int cls_bpf_exec_opcode(int code)
{
switch (code) {
case TC_ACT_OK:
case TC_ACT_SHOT:
case TC_ACT_STOLEN:
case TC_ACT_REDIRECT:
case TC_ACT_UNSPEC:
return code;
default:
return TC_ACT_UNSPEC;
}
}
static int cls_bpf_classify(struct sk_buff *skb, const struct tcf_proto *tp,
struct tcf_result *res)
{
struct cls_bpf_head *head = rcu_dereference_bh(tp->root);
struct cls_bpf_prog *prog;
#ifdef CONFIG_NET_CLS_ACT
bool at_ingress = G_TC_AT(skb->tc_verd) & AT_INGRESS;
#else
bool at_ingress = false;
#endif
int ret = -1;
if (unlikely(!skb_mac_header_was_set(skb)))
return -1;
/* Needed here for accessing maps. */
rcu_read_lock();
list_for_each_entry_rcu(prog, &head->plist, link) {
int filter_res;
qdisc_skb_cb(skb)->tc_classid = prog->res.classid;
if (at_ingress) {
/* It is safe to push/pull even if skb_shared() */
__skb_push(skb, skb->mac_len);
filter_res = BPF_PROG_RUN(prog->filter, skb);
__skb_pull(skb, skb->mac_len);
} else {
filter_res = BPF_PROG_RUN(prog->filter, skb);
}
if (prog->exts_integrated) {
res->class = prog->res.class;
res->classid = qdisc_skb_cb(skb)->tc_classid;
ret = cls_bpf_exec_opcode(filter_res);
if (ret == TC_ACT_UNSPEC)
continue;
break;
}
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;
break;
}
rcu_read_unlock();
return ret;
}
static bool cls_bpf_is_ebpf(const struct cls_bpf_prog *prog)
{
return !prog->bpf_ops;
}
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_RCU(&head->plist);
rcu_assign_pointer(tp->root, head);
return 0;
}
static void cls_bpf_delete_prog(struct tcf_proto *tp, struct cls_bpf_prog *prog)
{
tcf_exts_destroy(&prog->exts);
if (cls_bpf_is_ebpf(prog))
bpf_prog_put(prog->filter);
else
bpf_prog_destroy(prog->filter);
kfree(prog->bpf_name);
kfree(prog->bpf_ops);
kfree(prog);
}
static void __cls_bpf_delete_prog(struct rcu_head *rcu)
{
struct cls_bpf_prog *prog = container_of(rcu, struct cls_bpf_prog, rcu);
cls_bpf_delete_prog(prog->tp, prog);
}
static int cls_bpf_delete(struct tcf_proto *tp, unsigned long arg)
{
struct cls_bpf_prog *prog = (struct cls_bpf_prog *) arg;
list_del_rcu(&prog->link);
tcf_unbind_filter(tp, &prog->res);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
return 0;
}
static bool cls_bpf_destroy(struct tcf_proto *tp, bool force)
{
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *prog, *tmp;
if (!force && !list_empty(&head->plist))
return false;
list_for_each_entry_safe(prog, tmp, &head->plist, link) {
list_del_rcu(&prog->link);
tcf_unbind_filter(tp, &prog->res);
call_rcu(&prog->rcu, __cls_bpf_delete_prog);
}
RCU_INIT_POINTER(tp->root, NULL);
kfree_rcu(head, rcu);
return true;
}
static unsigned long cls_bpf_get(struct tcf_proto *tp, u32 handle)
{
struct cls_bpf_head *head = rtnl_dereference(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 int cls_bpf_prog_from_ops(struct nlattr **tb, struct cls_bpf_prog *prog)
{
struct sock_filter *bpf_ops;
struct sock_fprog_kern fprog_tmp;
struct bpf_prog *fp;
u16 bpf_size, bpf_num_ops;
int ret;
bpf_num_ops = nla_get_u16(tb[TCA_BPF_OPS_LEN]);
if (bpf_num_ops > BPF_MAXINSNS || bpf_num_ops == 0)
return -EINVAL;
bpf_size = bpf_num_ops * sizeof(*bpf_ops);
if (bpf_size != nla_len(tb[TCA_BPF_OPS]))
return -EINVAL;
bpf_ops = kzalloc(bpf_size, GFP_KERNEL);
if (bpf_ops == NULL)
return -ENOMEM;
memcpy(bpf_ops, nla_data(tb[TCA_BPF_OPS]), bpf_size);
fprog_tmp.len = bpf_num_ops;
fprog_tmp.filter = bpf_ops;
ret = bpf_prog_create(&fp, &fprog_tmp);
if (ret < 0) {
kfree(bpf_ops);
return ret;
}
prog->bpf_ops = bpf_ops;
prog->bpf_num_ops = bpf_num_ops;
prog->bpf_name = NULL;
prog->filter = fp;
return 0;
}
static int cls_bpf_prog_from_efd(struct nlattr **tb, struct cls_bpf_prog *prog)
{
struct bpf_prog *fp;
char *name = NULL;
u32 bpf_fd;
bpf_fd = nla_get_u32(tb[TCA_BPF_FD]);
fp = bpf_prog_get(bpf_fd);
if (IS_ERR(fp))
return PTR_ERR(fp);
if (fp->type != BPF_PROG_TYPE_SCHED_CLS) {
bpf_prog_put(fp);
return -EINVAL;
}
if (tb[TCA_BPF_NAME]) {
name = kmemdup(nla_data(tb[TCA_BPF_NAME]),
nla_len(tb[TCA_BPF_NAME]),
GFP_KERNEL);
if (!name) {
bpf_prog_put(fp);
return -ENOMEM;
}
}
prog->bpf_ops = NULL;
prog->bpf_fd = bpf_fd;
prog->bpf_name = name;
prog->filter = fp;
return 0;
}
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, bool ovr)
{
bool is_bpf, is_ebpf, have_exts = false;
struct tcf_exts exts;
int ret;
is_bpf = tb[TCA_BPF_OPS_LEN] && tb[TCA_BPF_OPS];
is_ebpf = tb[TCA_BPF_FD];
if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf))
return -EINVAL;
tcf_exts_init(&exts, TCA_BPF_ACT, TCA_BPF_POLICE);
ret = tcf_exts_validate(net, tp, tb, est, &exts, ovr);
if (ret < 0)
return ret;
if (tb[TCA_BPF_FLAGS]) {
u32 bpf_flags = nla_get_u32(tb[TCA_BPF_FLAGS]);
if (bpf_flags & ~TCA_BPF_FLAG_ACT_DIRECT) {
tcf_exts_destroy(&exts);
return -EINVAL;
}
have_exts = bpf_flags & TCA_BPF_FLAG_ACT_DIRECT;
}
prog->exts_integrated = have_exts;
ret = is_bpf ? cls_bpf_prog_from_ops(tb, prog) :
cls_bpf_prog_from_efd(tb, prog);
if (ret < 0) {
tcf_exts_destroy(&exts);
return ret;
}
if (tb[TCA_BPF_CLASSID]) {
prog->res.classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
tcf_bind_filter(tp, &prog->res, base);
}
tcf_exts_change(tp, &prog->exts, &exts);
return 0;
}
static u32 cls_bpf_grab_new_handle(struct tcf_proto *tp,
struct cls_bpf_head *head)
{
unsigned int i = 0x80000000;
u32 handle;
do {
if (++head->hgen == 0x7FFFFFFF)
head->hgen = 1;
} while (--i > 0 && cls_bpf_get(tp, head->hgen));
if (unlikely(i == 0)) {
pr_err("Insufficient number of handles\n");
handle = 0;
} else {
handle = head->hgen;
}
return handle;
}
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, bool ovr)
{
struct cls_bpf_head *head = rtnl_dereference(tp->root);
struct cls_bpf_prog *oldprog = (struct cls_bpf_prog *) *arg;
struct nlattr *tb[TCA_BPF_MAX + 1];
struct cls_bpf_prog *prog;
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;
prog = kzalloc(sizeof(*prog), GFP_KERNEL);
if (!prog)
return -ENOBUFS;
tcf_exts_init(&prog->exts, TCA_BPF_ACT, TCA_BPF_POLICE);
if (oldprog) {
if (handle && oldprog->handle != handle) {
ret = -EINVAL;
goto errout;
}
}
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], ovr);
if (ret < 0)
goto errout;
if (oldprog) {
list_replace_rcu(&oldprog->link, &prog->link);
tcf_unbind_filter(tp, &oldprog->res);
call_rcu(&oldprog->rcu, __cls_bpf_delete_prog);
} else {
list_add_rcu(&prog->link, &head->plist);
}
*arg = (unsigned long) prog;
return 0;
errout:
kfree(prog);
return ret;
}
static int cls_bpf_dump_bpf_info(const struct cls_bpf_prog *prog,
struct sk_buff *skb)
{
struct nlattr *nla;
if (nla_put_u16(skb, TCA_BPF_OPS_LEN, prog->bpf_num_ops))
return -EMSGSIZE;
nla = nla_reserve(skb, TCA_BPF_OPS, prog->bpf_num_ops *
sizeof(struct sock_filter));
if (nla == NULL)
return -EMSGSIZE;
memcpy(nla_data(nla), prog->bpf_ops, nla_len(nla));
return 0;
}
static int cls_bpf_dump_ebpf_info(const struct cls_bpf_prog *prog,
struct sk_buff *skb)
{
if (nla_put_u32(skb, TCA_BPF_FD, prog->bpf_fd))
return -EMSGSIZE;
if (prog->bpf_name &&
nla_put_string(skb, TCA_BPF_NAME, prog->bpf_name))
return -EMSGSIZE;
return 0;
}
static int cls_bpf_dump(struct net *net, 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;
u32 bpf_flags = 0;
int ret;
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 (prog->res.classid &&
nla_put_u32(skb, TCA_BPF_CLASSID, prog->res.classid))
goto nla_put_failure;
if (cls_bpf_is_ebpf(prog))
ret = cls_bpf_dump_ebpf_info(prog, skb);
else
ret = cls_bpf_dump_bpf_info(prog, skb);
if (ret)
goto nla_put_failure;
if (tcf_exts_dump(skb, &prog->exts) < 0)
goto nla_put_failure;
if (prog->exts_integrated)
bpf_flags |= TCA_BPF_FLAG_ACT_DIRECT;
if (bpf_flags && nla_put_u32(skb, TCA_BPF_FLAGS, bpf_flags))
goto nla_put_failure;
nla_nest_end(skb, nest);
if (tcf_exts_dump_stats(skb, &prog->exts) < 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 = rtnl_dereference(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,
.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);