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// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2019 Facebook */
#include <linux/stddef.h>
#include <linux/if_ether.h>
#include <linux/ipv6.h>
#include <linux/bpf.h>
#include <linux/tcp.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_tracing.h>
struct sk_buff {
unsigned int len;
};
__u64 test_result = 0;
SEC("fexit/test_pkt_access")
int BPF_PROG(test_main, struct sk_buff *skb, int ret)
{
int len;
__builtin_preserve_access_index(({
len = skb->len;
}));
if (len != 74 || ret != 0)
return 0;
test_result = 1;
return 0;
}
__u64 test_result_subprog1 = 0;
SEC("fexit/test_pkt_access_subprog1")
int BPF_PROG(test_subprog1, struct sk_buff *skb, int ret)
{
int len;
__builtin_preserve_access_index(({
len = skb->len;
}));
if (len != 74 || ret != 148)
return 0;
test_result_subprog1 = 1;
return 0;
}
/* Though test_pkt_access_subprog2() is defined in C as:
* static __attribute__ ((noinline))
* int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
* {
* return skb->len * val;
* }
* llvm optimizations remove 'int val' argument and generate BPF assembly:
* r0 = *(u32 *)(r1 + 0)
* w0 <<= 1
* exit
* In such case the verifier falls back to conservative and
* tracing program can access arguments and return value as u64
* instead of accurate types.
*/
struct args_subprog2 {
__u64 args[5];
__u64 ret;
};
__u64 test_result_subprog2 = 0;
SEC("fexit/test_pkt_access_subprog2")
int test_subprog2(struct args_subprog2 *ctx)
{
struct sk_buff *skb = (void *)ctx->args[0];
__u64 ret;
int len;
bpf_probe_read_kernel(&len, sizeof(len),
__builtin_preserve_access_index(&skb->len));
ret = ctx->ret;
/* bpf_prog_test_load() loads "test_pkt_access.o" with BPF_F_TEST_RND_HI32
* which randomizes upper 32 bits after BPF_ALU32 insns.
* Hence after 'w0 <<= 1' upper bits of $rax are random.
* That is expected and correct. Trim them.
*/
ret = (__u32) ret;
if (len != 74 || ret != 148)
return 0;
test_result_subprog2 = 1;
return 0;
}
__u64 test_result_subprog3 = 0;
SEC("fexit/test_pkt_access_subprog3")
int BPF_PROG(test_subprog3, int val, struct sk_buff *skb, int ret)
{
int len;
__builtin_preserve_access_index(({
len = skb->len;
}));
if (len != 74 || ret != 74 * val || val != 3)
return 0;
test_result_subprog3 = 1;
return 0;
}
__u64 test_get_skb_len = 0;
SEC("freplace/get_skb_len")
int new_get_skb_len(struct __sk_buff *skb)
{
int len = skb->len;
if (len != 74)
return 0;
test_get_skb_len = 1;
return 74; /* original get_skb_len() returns skb->len */
}
__u64 test_get_skb_ifindex = 0;
SEC("freplace/get_skb_ifindex")
int new_get_skb_ifindex(int val, struct __sk_buff *skb, int var)
{
void *data_end = (void *)(long)skb->data_end;
void *data = (void *)(long)skb->data;
struct ipv6hdr ip6, *ip6p;
int ifindex = skb->ifindex;
__u32 eth_proto;
__u32 nh_off;
/* check that BPF extension can read packet via direct packet access */
if (data + 14 + sizeof(ip6) > data_end)
return 0;
ip6p = data + 14;
if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123))
return 0;
/* check that legacy packet access helper works too */
if (bpf_skb_load_bytes(skb, 14, &ip6, sizeof(ip6)) < 0)
return 0;
ip6p = &ip6;
if (ip6p->nexthdr != 6 || ip6p->payload_len != __bpf_constant_htons(123))
return 0;
if (ifindex != 1 || val != 3 || var != 1)
return 0;
test_get_skb_ifindex = 1;
return 3; /* original get_skb_ifindex() returns val * ifindex * var */
}
volatile __u64 test_get_constant = 0;
SEC("freplace/get_constant")
int new_get_constant(long val)
{
if (val != 123)
return 0;
test_get_constant = 1;
return test_get_constant; /* original get_constant() returns val - 122 */
}
__u64 test_pkt_write_access_subprog = 0;
SEC("freplace/test_pkt_write_access_subprog")
int new_test_pkt_write_access_subprog(struct __sk_buff *skb, __u32 off)
{
void *data = (void *)(long)skb->data;
void *data_end = (void *)(long)skb->data_end;
struct tcphdr *tcp;
if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
return -1;
tcp = data + off;
if (tcp + 1 > data_end)
return -1;
/* make modifications to the packet data */
tcp->check++;
tcp->syn = 0;
test_pkt_write_access_subprog = 1;
return 0;
}
char _license[] SEC("license") = "GPL";
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