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Merge branch 'XDP-redirect-tracepoints'
Jesper Dangaard Brouer says: ==================== XDP redirect tracepoints I feel this is as far as I can take the tracepoint infrastructure to assist XDP monitoring. Tracepoints comes with a base overhead of 25 nanosec for an attached bpf_prog, and 48 nanosec for using a full perf record. This is problematic for the XDP use-case, but it is very convenient to use the existing perf infrastructure. From a performance perspective, the real solution would be to attach another bpf_prog (that understand xdp_buff), but I'm not sure we want to introduce yet another bpf attach API for this. One thing left is to standardize the possible err return codes, to a limited set, to allow easier (and faster) mapping into a bpf map. ==================== Signed-off-by: David S. Miller <davem@davemloft.net>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,88 @@ | ||
| /* XDP monitor tool, based on tracepoints | ||
| * | ||
| * Copyright(c) 2017 Jesper Dangaard Brouer, Red Hat Inc. | ||
| */ | ||
| #include <uapi/linux/bpf.h> | ||
| #include "bpf_helpers.h" | ||
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| struct bpf_map_def SEC("maps") redirect_err_cnt = { | ||
| .type = BPF_MAP_TYPE_PERCPU_ARRAY, | ||
| .key_size = sizeof(u32), | ||
| .value_size = sizeof(u64), | ||
| .max_entries = 2, | ||
| /* TODO: have entries for all possible errno's */ | ||
| }; | ||
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| /* Tracepoint format: /sys/kernel/debug/tracing/events/xdp/xdp_redirect/format | ||
| * Code in: kernel/include/trace/events/xdp.h | ||
| */ | ||
| struct xdp_redirect_ctx { | ||
| unsigned short common_type; // offset:0; size:2; signed:0; | ||
| unsigned char common_flags; // offset:2; size:1; signed:0; | ||
| unsigned char common_preempt_count;// offset:3; size:1; signed:0; | ||
| int common_pid; // offset:4; size:4; signed:1; | ||
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| int prog_id; // offset:8; size:4; signed:1; | ||
| u32 act; // offset:12 size:4; signed:0; | ||
| int ifindex; // offset:16 size:4; signed:1; | ||
| int err; // offset:20 size:4; signed:1; | ||
| int to_ifindex; // offset:24 size:4; signed:1; | ||
| u32 map_id; // offset:28 size:4; signed:0; | ||
| int map_index; // offset:32 size:4; signed:1; | ||
| }; // offset:36 | ||
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| enum { | ||
| XDP_REDIRECT_SUCCESS = 0, | ||
| XDP_REDIRECT_ERROR = 1 | ||
| }; | ||
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| static __always_inline | ||
| int xdp_redirect_collect_stat(struct xdp_redirect_ctx *ctx) | ||
| { | ||
| u32 key = XDP_REDIRECT_ERROR; | ||
| int err = ctx->err; | ||
| u64 *cnt; | ||
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| if (!err) | ||
| key = XDP_REDIRECT_SUCCESS; | ||
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| cnt = bpf_map_lookup_elem(&redirect_err_cnt, &key); | ||
| if (!cnt) | ||
| return 0; | ||
| *cnt += 1; | ||
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| return 0; /* Indicate event was filtered (no further processing)*/ | ||
| /* | ||
| * Returning 1 here would allow e.g. a perf-record tracepoint | ||
| * to see and record these events, but it doesn't work well | ||
| * in-practice as stopping perf-record also unload this | ||
| * bpf_prog. Plus, there is additional overhead of doing so. | ||
| */ | ||
| } | ||
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| SEC("tracepoint/xdp/xdp_redirect_err") | ||
| int trace_xdp_redirect_err(struct xdp_redirect_ctx *ctx) | ||
| { | ||
| return xdp_redirect_collect_stat(ctx); | ||
| } | ||
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| SEC("tracepoint/xdp/xdp_redirect_map_err") | ||
| int trace_xdp_redirect_map_err(struct xdp_redirect_ctx *ctx) | ||
| { | ||
| return xdp_redirect_collect_stat(ctx); | ||
| } | ||
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| /* Likely unloaded when prog starts */ | ||
| SEC("tracepoint/xdp/xdp_redirect") | ||
| int trace_xdp_redirect(struct xdp_redirect_ctx *ctx) | ||
| { | ||
| return xdp_redirect_collect_stat(ctx); | ||
| } | ||
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| /* Likely unloaded when prog starts */ | ||
| SEC("tracepoint/xdp/xdp_redirect_map") | ||
| int trace_xdp_redirect_map(struct xdp_redirect_ctx *ctx) | ||
| { | ||
| return xdp_redirect_collect_stat(ctx); | ||
| } |
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