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#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/pkt_cls.h>
#include <bpf/bpf_helpers.h>
#define META_SIZE 32
#define ctx_ptr(ctx, mem) (void *)(unsigned long)ctx->mem
/* Demonstrates how metadata can be passed from an XDP program to a TC program
* using bpf_xdp_adjust_meta.
* For the sake of testing the metadata support in drivers, the XDP program uses
* a fixed-size payload after the Ethernet header as metadata. The TC program
* copies the metadata it receives into a map so it can be checked from
* userspace.
*/
struct {
__uint(type, BPF_MAP_TYPE_ARRAY);
__uint(max_entries, 1);
__type(key, __u32);
__uint(value_size, META_SIZE);
} test_result SEC(".maps");
SEC("tc")
int ing_cls(struct __sk_buff *ctx)
{
__u8 *data, *data_meta;
__u32 key = 0;
data_meta = ctx_ptr(ctx, data_meta);
data = ctx_ptr(ctx, data);
if (data_meta + META_SIZE > data)
return TC_ACT_SHOT;
bpf_map_update_elem(&test_result, &key, data_meta, BPF_ANY);
return TC_ACT_SHOT;
}
SEC("xdp")
int ing_xdp(struct xdp_md *ctx)
{
__u8 *data, *data_meta, *data_end, *payload;
struct ethhdr *eth;
int ret;
ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
if (ret < 0)
return XDP_DROP;
data_meta = ctx_ptr(ctx, data_meta);
data_end = ctx_ptr(ctx, data_end);
data = ctx_ptr(ctx, data);
eth = (struct ethhdr *)data;
payload = data + sizeof(struct ethhdr);
if (payload + META_SIZE > data_end ||
data_meta + META_SIZE > data)
return XDP_DROP;
/* The Linux networking stack may send other packets on the test
* interface that interfere with the test. Just drop them.
* The test packets can be recognized by their ethertype of zero.
*/
if (eth->h_proto != 0)
return XDP_DROP;
__builtin_memcpy(data_meta, payload, META_SIZE);
return XDP_PASS;
}
char _license[] SEC("license") = "GPL";
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