1 #include <linux/bpf.h>
2 #include "bpf_helpers.h"
3 #include "bpf_util.h"
4 #include "bpf_endian.h"
5 
6 int _version SEC("version") = 1;
7 
8 #define bpf_printk(fmt, ...)					\
9 ({								\
10 	       char ____fmt[] = fmt;				\
11 	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
12 				##__VA_ARGS__);			\
13 })
14 
15 SEC("sk_skb1")
16 int bpf_prog1(struct __sk_buff *skb)
17 {
18 	void *data_end = (void *)(long) skb->data_end;
19 	void *data = (void *)(long) skb->data;
20 	__u32 lport = skb->local_port;
21 	__u32 rport = skb->remote_port;
22 	__u8 *d = data;
23 	__u32 len = (__u32) data_end - (__u32) data;
24 	int err;
25 
26 	if (data + 10 > data_end) {
27 		err = bpf_skb_pull_data(skb, 10);
28 		if (err)
29 			return SK_DROP;
30 
31 		data_end = (void *)(long)skb->data_end;
32 		data = (void *)(long)skb->data;
33 		if (data + 10 > data_end)
34 			return SK_DROP;
35 	}
36 
37 	/* This write/read is a bit pointless but tests the verifier and
38 	 * strparser handler for read/write pkt data and access into sk
39 	 * fields.
40 	 */
41 	d = data;
42 	d[7] = 1;
43 	return skb->len;
44 }
45 
46 char _license[] SEC("license") = "GPL";
47