tjh.dev
Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
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linux
1/* SPDX-License-Identifier: GPL-2.0
2 * Copyright (c) 2017 Jesper Dangaard Brouer, Red Hat Inc.
3 *
4 * Example howto extract XDP RX-queue info
5 */
6#include <uapi/linux/bpf.h>
7#include <uapi/linux/if_ether.h>
8#include <uapi/linux/in.h>
9#include "bpf_helpers.h"
10
11/* Config setup from with userspace
12 *
13 * User-side setup ifindex in config_map, to verify that
14 * ctx->ingress_ifindex is correct (against configured ifindex)
15 */
16struct config {
17 __u32 action;
18 int ifindex;
19 __u32 options;
20};
21enum cfg_options_flags {
22 NO_TOUCH = 0x0U,
23 READ_MEM = 0x1U,
24 SWAP_MAC = 0x2U,
25};
26struct bpf_map_def SEC("maps") config_map = {
27 .type = BPF_MAP_TYPE_ARRAY,
28 .key_size = sizeof(int),
29 .value_size = sizeof(struct config),
30 .max_entries = 1,
31};
32
33/* Common stats data record (shared with userspace) */
34struct datarec {
35 __u64 processed;
36 __u64 issue;
37};
38
39struct bpf_map_def SEC("maps") stats_global_map = {
40 .type = BPF_MAP_TYPE_PERCPU_ARRAY,
41 .key_size = sizeof(u32),
42 .value_size = sizeof(struct datarec),
43 .max_entries = 1,
44};
45
46#define MAX_RXQs 64
47
48/* Stats per rx_queue_index (per CPU) */
49struct bpf_map_def SEC("maps") rx_queue_index_map = {
50 .type = BPF_MAP_TYPE_PERCPU_ARRAY,
51 .key_size = sizeof(u32),
52 .value_size = sizeof(struct datarec),
53 .max_entries = MAX_RXQs + 1,
54};
55
56static __always_inline
57void swap_src_dst_mac(void *data)
58{
59 unsigned short *p = data;
60 unsigned short dst[3];
61
62 dst[0] = p[0];
63 dst[1] = p[1];
64 dst[2] = p[2];
65 p[0] = p[3];
66 p[1] = p[4];
67 p[2] = p[5];
68 p[3] = dst[0];
69 p[4] = dst[1];
70 p[5] = dst[2];
71}
72
73SEC("xdp_prog0")
74int xdp_prognum0(struct xdp_md *ctx)
75{
76 void *data_end = (void *)(long)ctx->data_end;
77 void *data = (void *)(long)ctx->data;
78 struct datarec *rec, *rxq_rec;
79 int ingress_ifindex;
80 struct config *config;
81 u32 key = 0;
82
83 /* Global stats record */
84 rec = bpf_map_lookup_elem(&stats_global_map, &key);
85 if (!rec)
86 return XDP_ABORTED;
87 rec->processed++;
88
89 /* Accessing ctx->ingress_ifindex, cause BPF to rewrite BPF
90 * instructions inside kernel to access xdp_rxq->dev->ifindex
91 */
92 ingress_ifindex = ctx->ingress_ifindex;
93
94 config = bpf_map_lookup_elem(&config_map, &key);
95 if (!config)
96 return XDP_ABORTED;
97
98 /* Simple test: check ctx provided ifindex is as expected */
99 if (ingress_ifindex != config->ifindex) {
100 /* count this error case */
101 rec->issue++;
102 return XDP_ABORTED;
103 }
104
105 /* Update stats per rx_queue_index. Handle if rx_queue_index
106 * is larger than stats map can contain info for.
107 */
108 key = ctx->rx_queue_index;
109 if (key >= MAX_RXQs)
110 key = MAX_RXQs;
111 rxq_rec = bpf_map_lookup_elem(&rx_queue_index_map, &key);
112 if (!rxq_rec)
113 return XDP_ABORTED;
114 rxq_rec->processed++;
115 if (key == MAX_RXQs)
116 rxq_rec->issue++;
117
118 /* Default: Don't touch packet data, only count packets */
119 if (unlikely(config->options & (READ_MEM|SWAP_MAC))) {
120 struct ethhdr *eth = data;
121
122 if (eth + 1 > data_end)
123 return XDP_ABORTED;
124
125 /* Avoid compiler removing this: Drop non 802.3 Ethertypes */
126 if (ntohs(eth->h_proto) < ETH_P_802_3_MIN)
127 return XDP_ABORTED;
128
129 /* XDP_TX requires changing MAC-addrs, else HW may drop.
130 * Can also be enabled with --swapmac (for test purposes)
131 */
132 if (unlikely(config->options & SWAP_MAC))
133 swap_src_dst_mac(data);
134 }
135
136 return config->action;
137}
138
139char _license[] SEC("license") = "GPL";