linux-stable/net/sched/act_bpf.c
Martin KaFai Lau 7449197d60 bpf: Keep the (rcv) timestamp behavior for the existing tc-bpf@ingress
The current tc-bpf@ingress reads and writes the __sk_buff->tstamp
as a (rcv) timestamp which currently could either be 0 (not available)
or ktime_get_real().  This patch is to backward compatible with the
(rcv) timestamp expectation at ingress.  If the skb->tstamp has
the delivery_time, the bpf insn rewrite will read 0 for tc-bpf
running at ingress as it is not available.  When writing at ingress,
it will also clear the skb->mono_delivery_time bit.

/* BPF_READ: a = __sk_buff->tstamp */
if (!skb->tc_at_ingress || !skb->mono_delivery_time)
	a = skb->tstamp;
else
	a = 0

/* BPF_WRITE: __sk_buff->tstamp = a */
if (skb->tc_at_ingress)
	skb->mono_delivery_time = 0;
skb->tstamp = a;

[ A note on the BPF_CGROUP_INET_INGRESS which can also access
  skb->tstamp.  At that point, the skb is delivered locally
  and skb_clear_delivery_time() has already been done,
  so the skb->tstamp will only have the (rcv) timestamp. ]

If the tc-bpf@egress writes 0 to skb->tstamp, the skb->mono_delivery_time
has to be cleared also.  It could be done together during
convert_ctx_access().  However, the latter patch will also expose
the skb->mono_delivery_time bit as __sk_buff->delivery_time_type.
Changing the delivery_time_type in the background may surprise
the user, e.g. the 2nd read on __sk_buff->delivery_time_type
may need a READ_ONCE() to avoid compiler optimization.  Thus,
in expecting the needs in the latter patch, this patch does a
check on !skb->tstamp after running the tc-bpf and clears the
skb->mono_delivery_time bit if needed.  The earlier discussion
on v4 [0].

The bpf insn rewrite requires the skb's mono_delivery_time bit and
tc_at_ingress bit.  They are moved up in sk_buff so that bpf rewrite
can be done at a fixed offset.  tc_skip_classify is moved together with
tc_at_ingress.  To get one bit for mono_delivery_time, csum_not_inet is
moved down and this bit is currently used by sctp.

[0]: https://lore.kernel.org/bpf/20220217015043.khqwqklx45c4m4se@kafai-mbp.dhcp.thefacebook.com/

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2022-03-03 14:38:48 +00:00

457 lines
10 KiB
C

// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (c) 2015 Jiri Pirko <jiri@resnulli.us>
*/
#include <linux/module.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/skbuff.h>
#include <linux/rtnetlink.h>
#include <linux/filter.h>
#include <linux/bpf.h>
#include <net/netlink.h>
#include <net/sock.h>
#include <net/pkt_sched.h>
#include <net/pkt_cls.h>
#include <linux/tc_act/tc_bpf.h>
#include <net/tc_act/tc_bpf.h>
#define ACT_BPF_NAME_LEN 256
struct tcf_bpf_cfg {
struct bpf_prog *filter;
struct sock_filter *bpf_ops;
const char *bpf_name;
u16 bpf_num_ops;
bool is_ebpf;
};
static unsigned int bpf_net_id;
static struct tc_action_ops act_bpf_ops;
static int tcf_bpf_act(struct sk_buff *skb, const struct tc_action *act,
struct tcf_result *res)
{
bool at_ingress = skb_at_tc_ingress(skb);
struct tcf_bpf *prog = to_bpf(act);
struct bpf_prog *filter;
int action, filter_res;
tcf_lastuse_update(&prog->tcf_tm);
bstats_update(this_cpu_ptr(prog->common.cpu_bstats), skb);
filter = rcu_dereference(prog->filter);
if (at_ingress) {
__skb_push(skb, skb->mac_len);
bpf_compute_data_pointers(skb);
filter_res = bpf_prog_run(filter, skb);
__skb_pull(skb, skb->mac_len);
} else {
bpf_compute_data_pointers(skb);
filter_res = bpf_prog_run(filter, skb);
}
if (unlikely(!skb->tstamp && skb->mono_delivery_time))
skb->mono_delivery_time = 0;
if (skb_sk_is_prefetched(skb) && filter_res != TC_ACT_OK)
skb_orphan(skb);
/* A BPF program may overwrite the default action opcode.
* Similarly as in cls_bpf, if filter_res == -1 we use the
* default action specified from tc.
*
* In case a different well-known TC_ACT opcode has been
* returned, it will overwrite the default one.
*
* For everything else that is unknown, TC_ACT_UNSPEC is
* returned.
*/
switch (filter_res) {
case TC_ACT_PIPE:
case TC_ACT_RECLASSIFY:
case TC_ACT_OK:
case TC_ACT_REDIRECT:
action = filter_res;
break;
case TC_ACT_SHOT:
action = filter_res;
qstats_drop_inc(this_cpu_ptr(prog->common.cpu_qstats));
break;
case TC_ACT_UNSPEC:
action = prog->tcf_action;
break;
default:
action = TC_ACT_UNSPEC;
break;
}
return action;
}
static bool tcf_bpf_is_ebpf(const struct tcf_bpf *prog)
{
return !prog->bpf_ops;
}
static int tcf_bpf_dump_bpf_info(const struct tcf_bpf *prog,
struct sk_buff *skb)
{
struct nlattr *nla;
if (nla_put_u16(skb, TCA_ACT_BPF_OPS_LEN, prog->bpf_num_ops))
return -EMSGSIZE;
nla = nla_reserve(skb, TCA_ACT_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 tcf_bpf_dump_ebpf_info(const struct tcf_bpf *prog,
struct sk_buff *skb)
{
struct nlattr *nla;
if (prog->bpf_name &&
nla_put_string(skb, TCA_ACT_BPF_NAME, prog->bpf_name))
return -EMSGSIZE;
if (nla_put_u32(skb, TCA_ACT_BPF_ID, prog->filter->aux->id))
return -EMSGSIZE;
nla = nla_reserve(skb, TCA_ACT_BPF_TAG, sizeof(prog->filter->tag));
if (nla == NULL)
return -EMSGSIZE;
memcpy(nla_data(nla), prog->filter->tag, nla_len(nla));
return 0;
}
static int tcf_bpf_dump(struct sk_buff *skb, struct tc_action *act,
int bind, int ref)
{
unsigned char *tp = skb_tail_pointer(skb);
struct tcf_bpf *prog = to_bpf(act);
struct tc_act_bpf opt = {
.index = prog->tcf_index,
.refcnt = refcount_read(&prog->tcf_refcnt) - ref,
.bindcnt = atomic_read(&prog->tcf_bindcnt) - bind,
};
struct tcf_t tm;
int ret;
spin_lock_bh(&prog->tcf_lock);
opt.action = prog->tcf_action;
if (nla_put(skb, TCA_ACT_BPF_PARMS, sizeof(opt), &opt))
goto nla_put_failure;
if (tcf_bpf_is_ebpf(prog))
ret = tcf_bpf_dump_ebpf_info(prog, skb);
else
ret = tcf_bpf_dump_bpf_info(prog, skb);
if (ret)
goto nla_put_failure;
tcf_tm_dump(&tm, &prog->tcf_tm);
if (nla_put_64bit(skb, TCA_ACT_BPF_TM, sizeof(tm), &tm,
TCA_ACT_BPF_PAD))
goto nla_put_failure;
spin_unlock_bh(&prog->tcf_lock);
return skb->len;
nla_put_failure:
spin_unlock_bh(&prog->tcf_lock);
nlmsg_trim(skb, tp);
return -1;
}
static const struct nla_policy act_bpf_policy[TCA_ACT_BPF_MAX + 1] = {
[TCA_ACT_BPF_PARMS] = { .len = sizeof(struct tc_act_bpf) },
[TCA_ACT_BPF_FD] = { .type = NLA_U32 },
[TCA_ACT_BPF_NAME] = { .type = NLA_NUL_STRING,
.len = ACT_BPF_NAME_LEN },
[TCA_ACT_BPF_OPS_LEN] = { .type = NLA_U16 },
[TCA_ACT_BPF_OPS] = { .type = NLA_BINARY,
.len = sizeof(struct sock_filter) * BPF_MAXINSNS },
};
static int tcf_bpf_init_from_ops(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
{
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_ACT_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_ACT_BPF_OPS]))
return -EINVAL;
bpf_ops = kmemdup(nla_data(tb[TCA_ACT_BPF_OPS]), bpf_size, GFP_KERNEL);
if (bpf_ops == NULL)
return -ENOMEM;
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;
}
cfg->bpf_ops = bpf_ops;
cfg->bpf_num_ops = bpf_num_ops;
cfg->filter = fp;
cfg->is_ebpf = false;
return 0;
}
static int tcf_bpf_init_from_efd(struct nlattr **tb, struct tcf_bpf_cfg *cfg)
{
struct bpf_prog *fp;
char *name = NULL;
u32 bpf_fd;
bpf_fd = nla_get_u32(tb[TCA_ACT_BPF_FD]);
fp = bpf_prog_get_type(bpf_fd, BPF_PROG_TYPE_SCHED_ACT);
if (IS_ERR(fp))
return PTR_ERR(fp);
if (tb[TCA_ACT_BPF_NAME]) {
name = nla_memdup(tb[TCA_ACT_BPF_NAME], GFP_KERNEL);
if (!name) {
bpf_prog_put(fp);
return -ENOMEM;
}
}
cfg->bpf_name = name;
cfg->filter = fp;
cfg->is_ebpf = true;
return 0;
}
static void tcf_bpf_cfg_cleanup(const struct tcf_bpf_cfg *cfg)
{
struct bpf_prog *filter = cfg->filter;
if (filter) {
if (cfg->is_ebpf)
bpf_prog_put(filter);
else
bpf_prog_destroy(filter);
}
kfree(cfg->bpf_ops);
kfree(cfg->bpf_name);
}
static void tcf_bpf_prog_fill_cfg(const struct tcf_bpf *prog,
struct tcf_bpf_cfg *cfg)
{
cfg->is_ebpf = tcf_bpf_is_ebpf(prog);
/* updates to prog->filter are prevented, since it's called either
* with tcf lock or during final cleanup in rcu callback
*/
cfg->filter = rcu_dereference_protected(prog->filter, 1);
cfg->bpf_ops = prog->bpf_ops;
cfg->bpf_name = prog->bpf_name;
}
static int tcf_bpf_init(struct net *net, struct nlattr *nla,
struct nlattr *est, struct tc_action **act,
struct tcf_proto *tp, u32 flags,
struct netlink_ext_ack *extack)
{
struct tc_action_net *tn = net_generic(net, bpf_net_id);
bool bind = flags & TCA_ACT_FLAGS_BIND;
struct nlattr *tb[TCA_ACT_BPF_MAX + 1];
struct tcf_chain *goto_ch = NULL;
struct tcf_bpf_cfg cfg, old;
struct tc_act_bpf *parm;
struct tcf_bpf *prog;
bool is_bpf, is_ebpf;
int ret, res = 0;
u32 index;
if (!nla)
return -EINVAL;
ret = nla_parse_nested_deprecated(tb, TCA_ACT_BPF_MAX, nla,
act_bpf_policy, NULL);
if (ret < 0)
return ret;
if (!tb[TCA_ACT_BPF_PARMS])
return -EINVAL;
parm = nla_data(tb[TCA_ACT_BPF_PARMS]);
index = parm->index;
ret = tcf_idr_check_alloc(tn, &index, act, bind);
if (!ret) {
ret = tcf_idr_create(tn, index, est, act,
&act_bpf_ops, bind, true, flags);
if (ret < 0) {
tcf_idr_cleanup(tn, index);
return ret;
}
res = ACT_P_CREATED;
} else if (ret > 0) {
/* Don't override defaults. */
if (bind)
return 0;
if (!(flags & TCA_ACT_FLAGS_REPLACE)) {
tcf_idr_release(*act, bind);
return -EEXIST;
}
} else {
return ret;
}
ret = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
if (ret < 0)
goto release_idr;
is_bpf = tb[TCA_ACT_BPF_OPS_LEN] && tb[TCA_ACT_BPF_OPS];
is_ebpf = tb[TCA_ACT_BPF_FD];
if ((!is_bpf && !is_ebpf) || (is_bpf && is_ebpf)) {
ret = -EINVAL;
goto put_chain;
}
memset(&cfg, 0, sizeof(cfg));
ret = is_bpf ? tcf_bpf_init_from_ops(tb, &cfg) :
tcf_bpf_init_from_efd(tb, &cfg);
if (ret < 0)
goto put_chain;
prog = to_bpf(*act);
spin_lock_bh(&prog->tcf_lock);
if (res != ACT_P_CREATED)
tcf_bpf_prog_fill_cfg(prog, &old);
prog->bpf_ops = cfg.bpf_ops;
prog->bpf_name = cfg.bpf_name;
if (cfg.bpf_num_ops)
prog->bpf_num_ops = cfg.bpf_num_ops;
goto_ch = tcf_action_set_ctrlact(*act, parm->action, goto_ch);
rcu_assign_pointer(prog->filter, cfg.filter);
spin_unlock_bh(&prog->tcf_lock);
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
if (res != ACT_P_CREATED) {
/* make sure the program being replaced is no longer executing */
synchronize_rcu();
tcf_bpf_cfg_cleanup(&old);
}
return res;
put_chain:
if (goto_ch)
tcf_chain_put_by_act(goto_ch);
release_idr:
tcf_idr_release(*act, bind);
return ret;
}
static void tcf_bpf_cleanup(struct tc_action *act)
{
struct tcf_bpf_cfg tmp;
tcf_bpf_prog_fill_cfg(to_bpf(act), &tmp);
tcf_bpf_cfg_cleanup(&tmp);
}
static int tcf_bpf_walker(struct net *net, struct sk_buff *skb,
struct netlink_callback *cb, int type,
const struct tc_action_ops *ops,
struct netlink_ext_ack *extack)
{
struct tc_action_net *tn = net_generic(net, bpf_net_id);
return tcf_generic_walker(tn, skb, cb, type, ops, extack);
}
static int tcf_bpf_search(struct net *net, struct tc_action **a, u32 index)
{
struct tc_action_net *tn = net_generic(net, bpf_net_id);
return tcf_idr_search(tn, a, index);
}
static struct tc_action_ops act_bpf_ops __read_mostly = {
.kind = "bpf",
.id = TCA_ID_BPF,
.owner = THIS_MODULE,
.act = tcf_bpf_act,
.dump = tcf_bpf_dump,
.cleanup = tcf_bpf_cleanup,
.init = tcf_bpf_init,
.walk = tcf_bpf_walker,
.lookup = tcf_bpf_search,
.size = sizeof(struct tcf_bpf),
};
static __net_init int bpf_init_net(struct net *net)
{
struct tc_action_net *tn = net_generic(net, bpf_net_id);
return tc_action_net_init(net, tn, &act_bpf_ops);
}
static void __net_exit bpf_exit_net(struct list_head *net_list)
{
tc_action_net_exit(net_list, bpf_net_id);
}
static struct pernet_operations bpf_net_ops = {
.init = bpf_init_net,
.exit_batch = bpf_exit_net,
.id = &bpf_net_id,
.size = sizeof(struct tc_action_net),
};
static int __init bpf_init_module(void)
{
return tcf_register_action(&act_bpf_ops, &bpf_net_ops);
}
static void __exit bpf_cleanup_module(void)
{
tcf_unregister_action(&act_bpf_ops, &bpf_net_ops);
}
module_init(bpf_init_module);
module_exit(bpf_cleanup_module);
MODULE_AUTHOR("Jiri Pirko <jiri@resnulli.us>");
MODULE_DESCRIPTION("TC BPF based action");
MODULE_LICENSE("GPL v2");