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xdp: Helpers for disabling napi_direct of xdp_return_frame

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We need some mechanism to disable napi_direct on calling
xdp_return_frame_rx_napi() from some context.
When veth gets support of XDP_REDIRECT, it will redirects packets which
are redirected from other devices. On redirection veth will reuse
xdp_mem_info of the redirection source device to make return_frame work.
But in this case .ndo_xdp_xmit() called from veth redirection uses
xdp_mem_info which is not guarded by NAPI, because the .ndo_xdp_xmit()
is not called directly from the rxq which owns the xdp_mem_info.

This approach introduces a flag in bpf_redirect_info to indicate that
napi_direct should be disabled even when _rx_napi variant is used as
well as helper functions to use it.

A NAPI handler who wants to use this flag needs to call
xdp_set_return_frame_no_direct() before processing packets, and call
xdp_clear_return_frame_no_direct() after xdp_do_flush_map() before
exiting NAPI.

v4:
- Use bpf_redirect_info for storing the flag instead of xdp_mem_info to
  avoid per-frame copy cost.

Signed-off-by: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Toshiaki Makita 2018-08-03 16:58:16 +09:00 committed by Daniel Borkmann
parent 0b19cc0a86
commit 2539650fad
2 changed files with 29 additions and 2 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

25
include/linux/filter.h
View file

@ -543,10 +543,14 @@ struct bpf_redirect_info {
struct bpf_map *map;
struct bpf_map *map_to_flush;
unsigned long map_owner;
u32 kern_flags;
};
DECLARE_PER_CPU(struct bpf_redirect_info, bpf_redirect_info);
/* flags for bpf_redirect_info kern_flags */
#define BPF_RI_F_RF_NO_DIRECT BIT(0) /* no napi_direct on return_frame */
/* Compute the linear packet data range [data, data_end) which
* will be accessed by various program types (cls_bpf, act_bpf,
* lwt, ...). Subsystems allowing direct data access must (!)
@ -775,6 +779,27 @@ static inline bool bpf_dump_raw_ok(void)
struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
const struct bpf_insn *patch, u32 len);
static inline bool xdp_return_frame_no_direct(void)
{
struct bpf_redirect_info *ri = this_cpu_ptr(&bpf_redirect_info);
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);
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);
ri->kern_flags &= ~BPF_RI_F_RF_NO_DIRECT;
}
static inline int xdp_ok_fwd_dev(const struct net_device *fwd,
unsigned int pktlen)
{

6
net/core/xdp.c
View file

@ -330,10 +330,12 @@ static void __xdp_return(void *data, struct xdp_mem_info *mem, bool napi_direct,
/* mem->id is valid, checked in xdp_rxq_info_reg_mem_model() */
xa = rhashtable_lookup(mem_id_ht, &mem->id, mem_id_rht_params);
page = virt_to_head_page(data);
if (xa)
if (xa) {
napi_direct &= !xdp_return_frame_no_direct();
page_pool_put_page(xa->page_pool, page, napi_direct);
else
} else {
put_page(page);
}
rcu_read_unlock();
break;
case MEM_TYPE_PAGE_SHARED: