[PATCH v9 net-next 14/15] net: Reference bpf_redirect_info via task_struct on PREEMPT_RT.

Sebastian Andrzej Siewior
2024-06-20T13:27:38Z

The XDP redirect process is two staged:
- bpf_prog_run_xdp() is invoked to run a eBPF program which inspects the
packet and makes decisions. While doing that, the per-CPU variable
bpf_redirect_info is used.

- Afterwards xdp_do_redirect() is invoked and accesses bpf_redirect_info
and it may also access other per-CPU variables like xskmap_flush_list.

At the very end of the NAPI callback, xdp_do_flush() is invoked which
does not access bpf_redirect_info but will touch the individual per-CPU
lists.

The per-CPU variables are only used in the NAPI callback hence disabling
bottom halves is the only protection mechanism. Users from preemptible
context (like cpu_map_kthread_run()) explicitly disable bottom halves
for protections reasons.
Without locking in local_bh_disable() on PREEMPT_RT this data structure
requires explicit locking.

PREEMPT_RT has forced-threaded interrupts enabled and every
NAPI-callback runs in a thread. If each thread has its own data
structure then locking can be avoided.

Create a struct bpf_net_context which contains struct bpf_redirect_info.
Define the variable on stack, use bpf_net_ctx_set() to save a pointer to
it, bpf_net_ctx_clear() removes it again.
The bpf_net_ctx_set() may nest. For instance a function can be used from
within NET_RX_SOFTIRQ/ net_rx_action which uses bpf_net_ctx_set() and
NET_TX_SOFTIRQ which does not. Therefore only the first invocations
updates the pointer.
Use bpf_net_ctx_get_ri() as a wrapper to retrieve the current struct
bpf_redirect_info. The returned data structure is zero initialized to
ensure nothing is leaked from stack. This is done on first usage of the
struct. bpf_net_ctx_set() sets bpf_redirect_info::kern_flags to 0 to
note that initialisation is required. First invocation of
bpf_net_ctx_get_ri() will memset() the data structure and update
bpf_redirect_info::kern_flags.
bpf_redirect_info::nh is excluded from memset because it is only used
once BPF_F_NEIGH is set which also sets the nh member. The kern_flags is
moved past nh to exclude it from memset.

The pointer to bpf_net_context is saved task's task_struct. Using
always the bpf_net_context approach has the advantage that there is
almost zero differences between PREEMPT_RT and non-PREEMPT_RT builds.

Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Eduard Zingerman <eddyz87@gmail.com>
Cc: Hao Luo <haoluo@google.com>
Cc: Jesper Dangaard Brouer <hawk@kernel.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: John Fastabend <john.fastabend@gmail.com>
Cc: KP Singh <kpsingh@kernel.org>
Cc: Martin KaFai Lau <martin.lau@linux.dev>
Cc: Song Liu <song@kernel.org>
Cc: Stanislav Fomichev <sdf@google.com>
Cc: Toke Høiland-Jørgensen <toke@redhat.com>
Cc: Yonghong Song <yonghong.song@linux.dev>
Cc: bpf@vger.kernel.org
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Jesper Dangaard Brouer <hawk@kernel.org>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
include/linux/filter.h | 56 ++++++++++++++++++++++++++++++++++--------
include/linux/sched.h | 3 +++
kernel/bpf/cpumap.c | 3 +++
kernel/bpf/devmap.c | 9 ++++++-
kernel/fork.c | 1 +
net/bpf/test_run.c | 11 ++++++++-
net/core/dev.c | 29 +++++++++++++++++++++-
net/core/filter.c | 44 +++++++++------------------------
net/core/lwt_bpf.c | 3 +++
9 files changed, 114 insertions(+), 45 deletions(-)

diff --git a/include/linux/filter.h b/include/linux/filter.h
index b02aea291b7e8..0a7f6e4a00b60 100644
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -733,21 +733,59 @@ struct bpf_nh_params {
};
};

+/* flags for bpf_redirect_info kern_flags */
+#define BPF_RI_F_RF_NO_DIRECT BIT(0) /* no napi_direct on return_frame */
+#define BPF_RI_F_RI_INIT BIT(1)
+
struct bpf_redirect_info {
u64 tgt_index;
void *tgt_value;
struct bpf_map *map;
u32 flags;
- u32 kern_flags;
u32 map_id;
enum bpf_map_type map_type;
struct bpf_nh_params nh;
+ u32 kern_flags;
};

-DECLARE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
+struct bpf_net_context {
+ struct bpf_redirect_info ri;
+};

-/* flags for bpf_redirect_info kern_flags */
-#define BPF_RI_F_RF_NO_DIRECT BIT(0) /* no napi_direct on return_frame */
+static inline struct bpf_net_context *bpf_net_ctx_set(struct bpf_net_context *bpf_net_ctx)
+{
+ struct task_struct *tsk = current;
+
+ if (tsk->bpf_net_context != NULL)
+ return NULL;
+ bpf_net_ctx->ri.kern_flags = 0;
+
+ tsk->bpf_net_context = bpf_net_ctx;
+ return bpf_net_ctx;
+}
+
+static inline void bpf_net_ctx_clear(struct bpf_net_context *bpf_net_ctx)
+{
+ if (bpf_net_ctx)
+ current->bpf_net_context = NULL;
+}
+
+static inline struct bpf_net_context *bpf_net_ctx_get(void)
+{
+ return current->bpf_net_context;
+}
+
+static inline struct bpf_redirect_info *bpf_net_ctx_get_ri(void)
+{
+ struct bpf_net_context *bpf_net_ctx = bpf_net_ctx_get();
+
+ if (!(bpf_net_ctx->ri.kern_flags & BPF_RI_F_RI_INIT)) {
+ memset(&bpf_net_ctx->ri, 0, offsetof(struct bpf_net_context, ri.nh));
+ bpf_net_ctx->ri.kern_flags |= BPF_RI_F_RI_INIT;
+ }
+
+ return &bpf_net_ctx->ri;
+}

/* Compute the linear packet data range [data, data_end) which
* will be accessed by various program types (cls_bpf, act_bpf,
@@ -1018,25 +1056,23 @@ struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
const struct bpf_insn *patch, u32 len);
int bpf_remove_insns(struct bpf_prog *prog, u32 off, u32 cnt);

-void bpf_clear_redirect_map(struct bpf_map *map);
-
static inline bool xdp_return_frame_no_direct(void)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

return ri->kern_flags & BPF_RI_F_RF_NO_DIRECT;
}

static inline void xdp_set_return_frame_no_direct(void)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

ri->kern_flags |= BPF_RI_F_RF_NO_DIRECT;
}

static inline void xdp_clear_return_frame_no_direct(void)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

ri->kern_flags &= ~BPF_RI_F_RF_NO_DIRECT;
}
@@ -1592,7 +1628,7 @@ static __always_inline long __bpf_xdp_redirect_map(struct bpf_map *map, u64 inde
u64 flags, const u64 flag_mask,
void *lookup_elem(struct bpf_map *map, u32 key))
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
const u64 action_mask = XDP_ABORTED | XDP_DROP | XDP_PASS | XDP_TX;

/* Lower bits of the flags are used as return code on lookup failure */
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5187486c25222..5ff5e65a46277 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -54,6 +54,7 @@ struct bio_list;
struct blk_plug;
struct bpf_local_storage;
struct bpf_run_ctx;
+struct bpf_net_context;
struct capture_control;
struct cfs_rq;
struct fs_struct;
@@ -1509,6 +1510,8 @@ struct task_struct {
/* Used for BPF run context */
struct bpf_run_ctx *bpf_ctx;
#endif
+ /* Used by BPF for per-TASK xdp storage */
+ struct bpf_net_context *bpf_net_context;

#ifdef CONFIG_GCC_PLUGIN_STACKLEAK
unsigned long lowest_stack;
diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index a8e34416e960f..66974bd027109 100644
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -240,12 +240,14 @@ static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
int xdp_n, struct xdp_cpumap_stats *stats,
struct list_head *list)
{
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int nframes;

if (!rcpu->prog)
return xdp_n;

rcu_read_lock_bh();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);

nframes = cpu_map_bpf_prog_run_xdp(rcpu, frames, xdp_n, stats);

@@ -255,6 +257,7 @@ static int cpu_map_bpf_prog_run(struct bpf_cpu_map_entry *rcpu, void **frames,
if (unlikely(!list_empty(list)))
cpu_map_bpf_prog_run_skb(rcpu, list, stats);

+ bpf_net_ctx_clear(bpf_net_ctx);
rcu_read_unlock_bh(); /* resched point, may call do_softirq() */

return nframes;
diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 7f3b34452243c..fbfdfb60db8d7 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -196,7 +196,14 @@ static void dev_map_free(struct bpf_map *map)
list_del_rcu(&dtab->list);
spin_unlock(&dev_map_lock);

- bpf_clear_redirect_map(map);
+ /* bpf_redirect_info->map is assigned in __bpf_xdp_redirect_map()
+ * during NAPI callback and cleared after the XDP redirect. There is no
+ * explicit RCU read section which protects bpf_redirect_info->map but
+ * local_bh_disable() also marks the beginning an RCU section. This
+ * makes the complete softirq callback RCU protected. Thus after
+ * following synchronize_rcu() there no bpf_redirect_info->map == map
+ * assignment.
+ */
synchronize_rcu();

/* Make sure prior __dev_map_entry_free() have completed. */
diff --git a/kernel/fork.c b/kernel/fork.c
index 99076dbe27d83..f314bdd7e6108 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2355,6 +2355,7 @@ __latent_entropy struct task_struct *copy_process(
RCU_INIT_POINTER(p->bpf_storage, NULL);
p->bpf_ctx = NULL;
#endif
+ p->bpf_net_context = NULL;

/* Perform scheduler related setup. Assign this task to a CPU. */
retval = sched_fork(clone_flags, p);
diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
index 36ae54f57bf57..a6d7f790cdda8 100644
--- a/net/bpf/test_run.c
+++ b/net/bpf/test_run.c
@@ -283,9 +283,10 @@ static int xdp_recv_frames(struct xdp_frame **frames, int nframes,
static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog,
u32 repeat)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int err = 0, act, ret, i, nframes = 0, batch_sz;
struct xdp_frame **frames = xdp->frames;
+ struct bpf_redirect_info *ri;
struct xdp_page_head *head;
struct xdp_frame *frm;
bool redirect = false;
@@ -295,6 +296,8 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog,
batch_sz = min_t(u32, repeat, xdp->batch_size);

local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
+ ri = bpf_net_ctx_get_ri();
xdp_set_return_frame_no_direct();

for (i = 0; i < batch_sz; i++) {
@@ -359,6 +362,7 @@ static int xdp_test_run_batch(struct xdp_test_data *xdp, struct bpf_prog *prog,
}

xdp_clear_return_frame_no_direct();
+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();
return err;
}
@@ -394,6 +398,7 @@ static int bpf_test_run_xdp_live(struct bpf_prog *prog, struct xdp_buff *ctx,
static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
u32 *retval, u32 *time, bool xdp)
{
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
struct bpf_prog_array_item item = {.prog = prog};
struct bpf_run_ctx *old_ctx;
struct bpf_cg_run_ctx run_ctx;
@@ -419,10 +424,14 @@ static int bpf_test_run(struct bpf_prog *prog, void *ctx, u32 repeat,
do {
run_ctx.prog_item = &item;
local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
+
if (xdp)
*retval = bpf_prog_run_xdp(prog, ctx);
else
*retval = bpf_prog_run(prog, ctx);
+
+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();
} while (bpf_test_timer_continue(&t, 1, repeat, &ret, time));
bpf_reset_run_ctx(old_ctx);
diff --git a/net/core/dev.c b/net/core/dev.c
index 8ef727c2ae2be..b94fb4e63a289 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4045,10 +4045,13 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
{
struct bpf_mprog_entry *entry = rcu_dereference_bh(skb->dev->tcx_ingress);
enum skb_drop_reason drop_reason = SKB_DROP_REASON_TC_INGRESS;
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int sch_ret;

if (!entry)
return skb;
+
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
if (*pt_prev) {
*ret = deliver_skb(skb, *pt_prev, orig_dev);
*pt_prev = NULL;
@@ -4077,10 +4080,12 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
break;
}
*ret = NET_RX_SUCCESS;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
case TC_ACT_SHOT:
kfree_skb_reason(skb, drop_reason);
*ret = NET_RX_DROP;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
/* used by tc_run */
case TC_ACT_STOLEN:
@@ -4090,8 +4095,10 @@ sch_handle_ingress(struct sk_buff *skb, struct packet_type **pt_prev, int *ret,
fallthrough;
case TC_ACT_CONSUMED:
*ret = NET_RX_SUCCESS;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
}
+ bpf_net_ctx_clear(bpf_net_ctx);

return skb;
}
@@ -4101,11 +4108,14 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
{
struct bpf_mprog_entry *entry = rcu_dereference_bh(dev->tcx_egress);
enum skb_drop_reason drop_reason = SKB_DROP_REASON_TC_EGRESS;
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int sch_ret;

if (!entry)
return skb;

+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
+
/* qdisc_skb_cb(skb)->pkt_len & tcx_set_ingress() was
* already set by the caller.
*/
@@ -4121,10 +4131,12 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
/* No need to push/pop skb's mac_header here on egress! */
skb_do_redirect(skb);
*ret = NET_XMIT_SUCCESS;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
case TC_ACT_SHOT:
kfree_skb_reason(skb, drop_reason);
*ret = NET_XMIT_DROP;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
/* used by tc_run */
case TC_ACT_STOLEN:
@@ -4134,8 +4146,10 @@ sch_handle_egress(struct sk_buff *skb, int *ret, struct net_device *dev)
fallthrough;
case TC_ACT_CONSUMED:
*ret = NET_XMIT_SUCCESS;
+ bpf_net_ctx_clear(bpf_net_ctx);
return NULL;
}
+ bpf_net_ctx_clear(bpf_net_ctx);

return skb;
}
@@ -6325,6 +6339,7 @@ enum {
static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock,
unsigned flags, u16 budget)
{
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
bool skip_schedule = false;
unsigned long timeout;
int rc;
@@ -6342,6 +6357,7 @@ static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock,
clear_bit(NAPI_STATE_IN_BUSY_POLL, &napi->state);

local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);

if (flags & NAPI_F_PREFER_BUSY_POLL) {
napi->defer_hard_irqs_count = READ_ONCE(napi->dev->napi_defer_hard_irqs);
@@ -6364,6 +6380,7 @@ static void busy_poll_stop(struct napi_struct *napi, void *have_poll_lock,
netpoll_poll_unlock(have_poll_lock);
if (rc == budget)
__busy_poll_stop(napi, skip_schedule);
+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();
}

@@ -6373,6 +6390,7 @@ static void __napi_busy_loop(unsigned int napi_id,
{
unsigned long start_time = loop_end ? busy_loop_current_time() : 0;
int (*napi_poll)(struct napi_struct *napi, int budget);
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
void *have_poll_lock = NULL;
struct napi_struct *napi;

@@ -6391,6 +6409,7 @@ static void __napi_busy_loop(unsigned int napi_id,
int work = 0;

local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
if (!napi_poll) {
unsigned long val = READ_ONCE(napi->state);

@@ -6421,6 +6440,7 @@ static void __napi_busy_loop(unsigned int napi_id,
__NET_ADD_STATS(dev_net(napi->dev),
LINUX_MIB_BUSYPOLLRXPACKETS, work);
skb_defer_free_flush(this_cpu_ptr(&softnet_data));
+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();

if (!loop_end || loop_end(loop_end_arg, start_time))
@@ -6848,6 +6868,7 @@ static int napi_thread_wait(struct napi_struct *napi)

static void napi_threaded_poll_loop(struct napi_struct *napi)
{
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
struct softnet_data *sd;
unsigned long last_qs = jiffies;

@@ -6856,6 +6877,8 @@ static void napi_threaded_poll_loop(struct napi_struct *napi)
void *have;

local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
+
sd = this_cpu_ptr(&softnet_data);
sd->in_napi_threaded_poll = true;

@@ -6871,6 +6894,7 @@ static void napi_threaded_poll_loop(struct napi_struct *napi)
net_rps_action_and_irq_enable(sd);
}
skb_defer_free_flush(sd);
+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();

if (!repoll)
@@ -6896,10 +6920,12 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
struct softnet_data *sd = this_cpu_ptr(&softnet_data);
unsigned long time_limit = jiffies +
usecs_to_jiffies(READ_ONCE(net_hotdata.netdev_budget_usecs));
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int budget = READ_ONCE(net_hotdata.netdev_budget);
LIST_HEAD(list);
LIST_HEAD(repoll);

+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
start:
sd->in_net_rx_action = true;
local_irq_disable();
@@ -6952,7 +6978,8 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
sd->in_net_rx_action = false;

net_rps_action_and_irq_enable(sd);
-end:;
+end:
+ bpf_net_ctx_clear(bpf_net_ctx);
}

struct netdev_adjacent {
diff --git a/net/core/filter.c b/net/core/filter.c
index fbcfd563dccfd..f40b8393dd58f 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2478,9 +2478,6 @@ static const struct bpf_func_proto bpf_clone_redirect_proto = {
.arg3_type = ARG_ANYTHING,
};

-DEFINE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
-EXPORT_PER_CPU_SYMBOL_GPL(bpf_redirect_info);
-
static struct net_device *skb_get_peer_dev(struct net_device *dev)
{
const struct net_device_ops *ops = dev->netdev_ops;
@@ -2493,7 +2490,7 @@ static struct net_device *skb_get_peer_dev(struct net_device *dev)

int skb_do_redirect(struct sk_buff *skb)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
struct net *net = dev_net(skb->dev);
struct net_device *dev;
u32 flags = ri->flags;
@@ -2526,7 +2523,7 @@ int skb_do_redirect(struct sk_buff *skb)

BPF_CALL_2(bpf_redirect, u32, ifindex, u64, flags)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

if (unlikely(flags & (~(BPF_F_INGRESS) | BPF_F_REDIRECT_INTERNAL)))
return TC_ACT_SHOT;
@@ -2547,7 +2544,7 @@ static const struct bpf_func_proto bpf_redirect_proto = {

BPF_CALL_2(bpf_redirect_peer, u32, ifindex, u64, flags)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

if (unlikely(flags))
return TC_ACT_SHOT;
@@ -2569,7 +2566,7 @@ static const struct bpf_func_proto bpf_redirect_peer_proto = {
BPF_CALL_4(bpf_redirect_neigh, u32, ifindex, struct bpf_redir_neigh *, params,
int, plen, u64, flags)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

if (unlikely((plen && plen < sizeof(*params)) || flags))
return TC_ACT_SHOT;
@@ -4295,30 +4292,13 @@ void xdp_do_check_flushed(struct napi_struct *napi)
}
#endif

-void bpf_clear_redirect_map(struct bpf_map *map)
-{
- struct bpf_redirect_info *ri;
- int cpu;
-
- for_each_possible_cpu(cpu) {
- ri = per_cpu_ptr(&bpf_redirect_info, cpu);
- /* Avoid polluting remote cacheline due to writes if
- * not needed. Once we pass this test, we need the
- * cmpxchg() to make sure it hasn't been changed in
- * the meantime by remote CPU.
- */
- if (unlikely(READ_ONCE(ri->map) == map))
- cmpxchg(&ri->map, map, NULL);
- }
-}
-
DEFINE_STATIC_KEY_FALSE(bpf_master_redirect_enabled_key);
EXPORT_SYMBOL_GPL(bpf_master_redirect_enabled_key);

u32 xdp_master_redirect(struct xdp_buff *xdp)
{
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
struct net_device *master, *slave;
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);

master = netdev_master_upper_dev_get_rcu(xdp->rxq->dev);
slave = master->netdev_ops->ndo_xdp_get_xmit_slave(master, xdp);
@@ -4390,7 +4370,7 @@ static __always_inline int __xdp_do_redirect_frame(struct bpf_redirect_info *ri,
map = READ_ONCE(ri->map);

/* The map pointer is cleared when the map is being torn
- * down by bpf_clear_redirect_map()
+ * down by dev_map_free()
*/
if (unlikely(!map)) {
err = -ENOENT;
@@ -4435,7 +4415,7 @@ static __always_inline int __xdp_do_redirect_frame(struct bpf_redirect_info *ri,
int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp,
struct bpf_prog *xdp_prog)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
enum bpf_map_type map_type = ri->map_type;

if (map_type == BPF_MAP_TYPE_XSKMAP)
@@ -4449,7 +4429,7 @@ EXPORT_SYMBOL_GPL(xdp_do_redirect);
int xdp_do_redirect_frame(struct net_device *dev, struct xdp_buff *xdp,
struct xdp_frame *xdpf, struct bpf_prog *xdp_prog)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
enum bpf_map_type map_type = ri->map_type;

if (map_type == BPF_MAP_TYPE_XSKMAP)
@@ -4466,7 +4446,7 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
enum bpf_map_type map_type, u32 map_id,
u32 flags)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
struct bpf_map *map;
int err;

@@ -4478,7 +4458,7 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
map = READ_ONCE(ri->map);

/* The map pointer is cleared when the map is being torn
- * down by bpf_clear_redirect_map()
+ * down by dev_map_free()
*/
if (unlikely(!map)) {
err = -ENOENT;
@@ -4520,7 +4500,7 @@ static int xdp_do_generic_redirect_map(struct net_device *dev,
int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,
struct xdp_buff *xdp, struct bpf_prog *xdp_prog)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();
enum bpf_map_type map_type = ri->map_type;
void *fwd = ri->tgt_value;
u32 map_id = ri->map_id;
@@ -4556,7 +4536,7 @@ int xdp_do_generic_redirect(struct net_device *dev, struct sk_buff *skb,

BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags)
{
- struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
+ struct bpf_redirect_info *ri = bpf_net_ctx_get_ri();

if (unlikely(flags))
return XDP_ABORTED;
diff --git a/net/core/lwt_bpf.c b/net/core/lwt_bpf.c
index a94943681e5aa..afb05f58b64c5 100644
--- a/net/core/lwt_bpf.c
+++ b/net/core/lwt_bpf.c
@@ -38,12 +38,14 @@ static inline struct bpf_lwt *bpf_lwt_lwtunnel(struct lwtunnel_state *lwt)
static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
struct dst_entry *dst, bool can_redirect)
{
+ struct bpf_net_context __bpf_net_ctx, *bpf_net_ctx;
int ret;

/* Disabling BH is needed to protect per-CPU bpf_redirect_info between
* BPF prog and skb_do_redirect().
*/
local_bh_disable();
+ bpf_net_ctx = bpf_net_ctx_set(&__bpf_net_ctx);
bpf_compute_data_pointers(skb);
ret = bpf_prog_run_save_cb(lwt->prog, skb);

@@ -76,6 +78,7 @@ static int run_lwt_bpf(struct sk_buff *skb, struct bpf_lwt_prog *lwt,
break;
}

+ bpf_net_ctx_clear(bpf_net_ctx);
local_bh_enable();

return ret;
--
2.45.2