linux/net/sched/cls_bpf.c
Alexei Starovoitov a166151cbe bpf: fix bpf helpers to use skb->mac_header relative offsets
For the short-term solution, lets fix bpf helper functions to use
skb->mac_header relative offsets instead of skb->data in order to
get the same eBPF programs with cls_bpf and act_bpf work on ingress
and egress qdisc path. We need to ensure that mac_header is set
before calling into programs. This is effectively the first option
from below referenced discussion.

More long term solution for LD_ABS|LD_IND instructions will be more
intrusive but also more beneficial than this, and implemented later
as it's too risky at this point in time.

I.e., we plan to look into the option of moving skb_pull() out of
eth_type_trans() and into netif_receive_skb() as has been suggested
as second option. Meanwhile, this solution ensures ingress can be
used with eBPF, too, and that we won't run into ABI troubles later.
For dealing with negative offsets inside eBPF helper functions,
we've implemented bpf_skb_clone_unwritable() to test for unwriteable
headers.

Reference: http://thread.gmane.org/gmane.linux.network/359129/focus=359694
Fixes: 608cd71a9c ("tc: bpf: generalize pedit action")
Fixes: 91bc4822c3 ("tc: bpf: add checksum helpers")
Signed-off-by: Alexei Starovoitov <ast@plumgrid.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
2015-04-16 14:08:49 -04:00

496 lines
10 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;
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_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_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;
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 = BPF_PROG_RUN(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;
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, u32 classid)
{
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;
prog->res.classid = classid;
return 0;
}
static int cls_bpf_prog_from_efd(struct nlattr **tb,
struct cls_bpf_prog *prog, u32 classid)
{
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;
prog->res.classid = classid;
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)
{
struct tcf_exts exts;
bool is_bpf, is_ebpf;
u32 classid;
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) ||
!tb[TCA_BPF_CLASSID])
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;
classid = nla_get_u32(tb[TCA_BPF_CLASSID]);
ret = is_bpf ? cls_bpf_prog_from_ops(tb, prog, classid) :
cls_bpf_prog_from_efd(tb, prog, classid);
if (ret < 0) {
tcf_exts_destroy(&exts);
return ret;
}
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(&prog->link, &oldprog->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;
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 (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;
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);