1 // SPDX-License-Identifier: GPL-2.0
2 // Copyright (c) 2019 Facebook
3 #include <linux/bpf.h>
4 #include <stdbool.h>
5 #include <bpf/bpf_helpers.h>
6 #include <bpf/bpf_endian.h>
7 #include <bpf/bpf_tracing.h>
8
9 char _license[] SEC("license") = "GPL";
10 struct {
11 __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
12 __type(key, int);
13 __type(value, int);
14 } perf_buf_map SEC(".maps");
15
16 #define _(P) (__builtin_preserve_access_index(P))
17
18 /* define few struct-s that bpf program needs to access */
19 struct callback_head {
20 struct callback_head *next;
21 void (*func)(struct callback_head *head);
22 };
23 struct dev_ifalias {
24 struct callback_head rcuhead;
25 };
26
27 struct net_device /* same as kernel's struct net_device */ {
28 int ifindex;
29 struct dev_ifalias *ifalias;
30 };
31
32 typedef struct {
33 int counter;
34 } atomic_t;
35 typedef struct refcount_struct {
36 atomic_t refs;
37 } refcount_t;
38
39 struct sk_buff {
40 /* field names and sizes should match to those in the kernel */
41 unsigned int len, data_len;
42 __u16 mac_len, hdr_len, queue_mapping;
43 struct net_device *dev;
44 /* order of the fields doesn't matter */
45 refcount_t users;
46 unsigned char *data;
47 char __pkt_type_offset[0];
48 char cb[48];
49 };
50
51 struct meta {
52 int ifindex;
53 __u32 cb32_0;
54 __u8 cb8_0;
55 };
56
57 /* TRACE_EVENT(kfree_skb,
58 * TP_PROTO(struct sk_buff *skb, void *location),
59 */
60 SEC("tp_btf/kfree_skb")
61 int BPF_PROG(trace_kfree_skb, struct sk_buff *skb, void *location)
62 {
63 struct net_device *dev;
64 struct callback_head *ptr;
65 void *func;
66 int users;
67 unsigned char *data;
68 unsigned short pkt_data;
69 struct meta meta = {};
70 char pkt_type;
71 __u32 *cb32;
72 __u8 *cb8;
73
74 __builtin_preserve_access_index(({
75 users = skb->users.refs.counter;
76 data = skb->data;
77 dev = skb->dev;
78 ptr = dev->ifalias->rcuhead.next;
79 func = ptr->func;
80 cb8 = (__u8 *)&skb->cb;
81 cb32 = (__u32 *)&skb->cb;
82 }));
83
84 meta.ifindex = _(dev->ifindex);
85 meta.cb8_0 = cb8[8];
86 meta.cb32_0 = cb32[2];
87
88 bpf_probe_read_kernel(&pkt_type, sizeof(pkt_type), _(&skb->__pkt_type_offset));
89 pkt_type &= 7;
90
91 /* read eth proto */
92 bpf_probe_read_kernel(&pkt_data, sizeof(pkt_data), data + 12);
93
94 bpf_printk("rcuhead.next %llx func %llx\n", ptr, func);
95 bpf_printk("skb->len %d users %d pkt_type %x\n",
96 _(skb->len), users, pkt_type);
97 bpf_printk("skb->queue_mapping %d\n", _(skb->queue_mapping));
98 bpf_printk("dev->ifindex %d data %llx pkt_data %x\n",
99 meta.ifindex, data, pkt_data);
100 bpf_printk("cb8_0:%x cb32_0:%x\n", meta.cb8_0, meta.cb32_0);
101
102 if (users != 1 || pkt_data != bpf_htons(0x86dd) || meta.ifindex != 1)
103 /* raw tp ignores return value */
104 return 0;
105
106 /* send first 72 byte of the packet to user space */
107 bpf_skb_output(skb, &perf_buf_map, (72ull << 32) | BPF_F_CURRENT_CPU,
108 &meta, sizeof(meta));
109 return 0;
110 }
111
112 struct {
113 bool fentry_test_ok;
114 bool fexit_test_ok;
115 } result = {};
116
117 SEC("fentry/eth_type_trans")
118 int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
119 unsigned short protocol)
120 {
121 int len, ifindex;
122
123 __builtin_preserve_access_index(({
124 len = skb->len;
125 ifindex = dev->ifindex;
126 }));
127
128 /* fentry sees full packet including L2 header */
129 if (len != 74 || ifindex != 1)
130 return 0;
131 result.fentry_test_ok = true;
132 return 0;
133 }
134
135 SEC("fexit/eth_type_trans")
136 int BPF_PROG(fexit_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
137 unsigned short protocol)
138 {
139 int len, ifindex;
140
141 __builtin_preserve_access_index(({
142 len = skb->len;
143 ifindex = dev->ifindex;
144 }));
145
146 /* fexit sees packet without L2 header that eth_type_trans should have
147 * consumed.
148 */
149 if (len != 60 || protocol != bpf_htons(0x86dd) || ifindex != 1)
150 return 0;
151 result.fexit_test_ok = true;
152 return 0;
153 }
154
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