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#include <stdbool.h>
#include <linux/bpf.h>
#include <linux/errno.h>
#include <linux/if_ether.h>
#include <linux/pkt_cls.h>
#include <bpf/bpf_helpers.h>
#include "bpf_kfuncs.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;
}
/* Read from metadata using bpf_dynptr_read helper */
SEC("tc")
int ing_cls_dynptr_read(struct __sk_buff *ctx)
{
struct bpf_dynptr meta;
const __u32 zero = 0;
__u8 *dst;
dst = bpf_map_lookup_elem(&test_result, &zero);
if (!dst)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
bpf_dynptr_read(dst, META_SIZE, &meta, 0, 0);
return TC_ACT_SHOT;
}
/* Write to metadata using bpf_dynptr_write helper */
SEC("tc")
int ing_cls_dynptr_write(struct __sk_buff *ctx)
{
struct bpf_dynptr data, meta;
__u8 *src;
bpf_dynptr_from_skb(ctx, 0, &data);
src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
if (!src)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
bpf_dynptr_write(&meta, 0, src, META_SIZE, 0);
return TC_ACT_UNSPEC; /* pass */
}
/* Read from metadata using read-only dynptr slice */
SEC("tc")
int ing_cls_dynptr_slice(struct __sk_buff *ctx)
{
struct bpf_dynptr meta;
const __u32 zero = 0;
__u8 *dst, *src;
dst = bpf_map_lookup_elem(&test_result, &zero);
if (!dst)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
src = bpf_dynptr_slice(&meta, 0, NULL, META_SIZE);
if (!src)
return TC_ACT_SHOT;
__builtin_memcpy(dst, src, META_SIZE);
return TC_ACT_SHOT;
}
/* Write to metadata using writeable dynptr slice */
SEC("tc")
int ing_cls_dynptr_slice_rdwr(struct __sk_buff *ctx)
{
struct bpf_dynptr data, meta;
__u8 *src, *dst;
bpf_dynptr_from_skb(ctx, 0, &data);
src = bpf_dynptr_slice(&data, sizeof(struct ethhdr), NULL, META_SIZE);
if (!src)
return TC_ACT_SHOT;
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
dst = bpf_dynptr_slice_rdwr(&meta, 0, NULL, META_SIZE);
if (!dst)
return TC_ACT_SHOT;
__builtin_memcpy(dst, src, META_SIZE);
return TC_ACT_UNSPEC; /* pass */
}
/* Read skb metadata in chunks from various offsets in different ways. */
SEC("tc")
int ing_cls_dynptr_offset_rd(struct __sk_buff *ctx)
{
struct bpf_dynptr meta;
const __u32 chunk_len = META_SIZE / 4;
const __u32 zero = 0;
__u8 *dst, *src;
dst = bpf_map_lookup_elem(&test_result, &zero);
if (!dst)
return TC_ACT_SHOT;
/* 1. Regular read */
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
bpf_dynptr_read(dst, chunk_len, &meta, 0, 0);
dst += chunk_len;
/* 2. Read from an offset-adjusted dynptr */
bpf_dynptr_adjust(&meta, chunk_len, bpf_dynptr_size(&meta));
bpf_dynptr_read(dst, chunk_len, &meta, 0, 0);
dst += chunk_len;
/* 3. Read at an offset */
bpf_dynptr_read(dst, chunk_len, &meta, chunk_len, 0);
dst += chunk_len;
/* 4. Read from a slice starting at an offset */
src = bpf_dynptr_slice(&meta, 2 * chunk_len, NULL, chunk_len);
if (!src)
return TC_ACT_SHOT;
__builtin_memcpy(dst, src, chunk_len);
return TC_ACT_SHOT;
}
/* Write skb metadata in chunks at various offsets in different ways. */
SEC("tc")
int ing_cls_dynptr_offset_wr(struct __sk_buff *ctx)
{
const __u32 chunk_len = META_SIZE / 4;
__u8 payload[META_SIZE];
struct bpf_dynptr meta;
__u8 *dst, *src;
bpf_skb_load_bytes(ctx, sizeof(struct ethhdr), payload, sizeof(payload));
src = payload;
/* 1. Regular write */
bpf_dynptr_from_skb_meta(ctx, 0, &meta);
bpf_dynptr_write(&meta, 0, src, chunk_len, 0);
src += chunk_len;
/* 2. Write to an offset-adjusted dynptr */
bpf_dynptr_adjust(&meta, chunk_len, bpf_dynptr_size(&meta));
bpf_dynptr_write(&meta, 0, src, chunk_len, 0);
src += chunk_len;
/* 3. Write at an offset */
bpf_dynptr_write(&meta, chunk_len, src, chunk_len, 0);
src += chunk_len;
/* 4. Write to a slice starting at an offset */
dst = bpf_dynptr_slice_rdwr(&meta, 2 * chunk_len, NULL, chunk_len);
if (!dst)
return TC_ACT_SHOT;
__builtin_memcpy(dst, src, chunk_len);
return TC_ACT_UNSPEC; /* pass */
}
/* Pass an OOB offset to dynptr read, write, adjust, slice. */
SEC("tc")
int ing_cls_dynptr_offset_oob(struct __sk_buff *ctx)
{
struct bpf_dynptr meta;
__u8 md, *p;
int err;
err = bpf_dynptr_from_skb_meta(ctx, 0, &meta);
if (err)
goto fail;
/* read offset OOB */
err = bpf_dynptr_read(&md, sizeof(md), &meta, META_SIZE, 0);
if (err != -E2BIG)
goto fail;
/* write offset OOB */
err = bpf_dynptr_write(&meta, META_SIZE, &md, sizeof(md), 0);
if (err != -E2BIG)
goto fail;
/* adjust end offset OOB */
err = bpf_dynptr_adjust(&meta, 0, META_SIZE + 1);
if (err != -ERANGE)
goto fail;
/* adjust start offset OOB */
err = bpf_dynptr_adjust(&meta, META_SIZE + 1, META_SIZE + 1);
if (err != -ERANGE)
goto fail;
/* slice offset OOB */
p = bpf_dynptr_slice(&meta, META_SIZE, NULL, sizeof(*p));
if (p)
goto fail;
/* slice rdwr offset OOB */
p = bpf_dynptr_slice_rdwr(&meta, META_SIZE, NULL, sizeof(*p));
if (p)
goto fail;
return TC_ACT_UNSPEC;
fail:
return TC_ACT_SHOT;
}
/* Reserve and clear space for metadata but don't populate it */
SEC("xdp")
int ing_xdp_zalloc_meta(struct xdp_md *ctx)
{
struct ethhdr *eth = ctx_ptr(ctx, data);
__u8 *meta;
int ret;
/* Drop any non-test packets */
if (eth + 1 > ctx_ptr(ctx, data_end))
return XDP_DROP;
if (eth->h_proto != 0)
return XDP_DROP;
ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
if (ret < 0)
return XDP_DROP;
meta = ctx_ptr(ctx, data_meta);
if (meta + META_SIZE > ctx_ptr(ctx, data))
return XDP_DROP;
__builtin_memset(meta, 0, META_SIZE);
return XDP_PASS;
}
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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