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// SPDX-License-Identifier: GPL-2.0-only
/* Copyright (c) 2017 Facebook
*/
#include <stddef.h>
#include <string.h>
#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/if_packet.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/in.h>
#include <linux/tcp.h>
#include <linux/pkt_cls.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define barrier() __asm__ __volatile__("": : :"memory")
int _version SEC("version") = 1;
/* llvm will optimize both subprograms into exactly the same BPF assembly
*
* Disassembly of section .text:
*
* 0000000000000000 test_pkt_access_subprog1:
* ; return skb->len * 2;
* 0: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0)
* 1: 64 00 00 00 01 00 00 00 w0 <<= 1
* 2: 95 00 00 00 00 00 00 00 exit
*
* 0000000000000018 test_pkt_access_subprog2:
* ; return skb->len * val;
* 3: 61 10 00 00 00 00 00 00 r0 = *(u32 *)(r1 + 0)
* 4: 64 00 00 00 01 00 00 00 w0 <<= 1
* 5: 95 00 00 00 00 00 00 00 exit
*
* Which makes it an interesting test for BTF-enabled verifier.
*/
static __attribute__ ((noinline))
int test_pkt_access_subprog1(volatile struct __sk_buff *skb)
{
return skb->len * 2;
}
static __attribute__ ((noinline))
int test_pkt_access_subprog2(int val, volatile struct __sk_buff *skb)
{
return skb->len * val;
}
#define MAX_STACK (512 - 2 * 32)
__attribute__ ((noinline))
int get_skb_len(struct __sk_buff *skb)
{
volatile char buf[MAX_STACK] = {};
return skb->len;
}
__attribute__ ((noinline))
int get_constant(long val)
{
return val - 122;
}
int get_skb_ifindex(int, struct __sk_buff *skb, int);
__attribute__ ((noinline))
int test_pkt_access_subprog3(int val, struct __sk_buff *skb)
{
return get_skb_len(skb) * get_skb_ifindex(val, skb, get_constant(123));
}
__attribute__ ((noinline))
int get_skb_ifindex(int val, struct __sk_buff *skb, int var)
{
volatile char buf[MAX_STACK] = {};
return skb->ifindex * val * var;
}
__attribute__ ((noinline))
int 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 = NULL;
if (off > sizeof(struct ethhdr) + sizeof(struct ipv6hdr))
return -1;
tcp = data + off;
if (tcp + 1 > data_end)
return -1;
/* make modification to the packet data */
tcp->check++;
return 0;
}
SEC("classifier/test_pkt_access")
int test_pkt_access(struct __sk_buff *skb)
{
void *data_end = (void *)(long)skb->data_end;
void *data = (void *)(long)skb->data;
struct ethhdr *eth = (struct ethhdr *)(data);
struct tcphdr *tcp = NULL;
__u8 proto = 255;
__u64 ihl_len;
if (eth + 1 > data_end)
return TC_ACT_SHOT;
if (eth->h_proto == bpf_htons(ETH_P_IP)) {
struct iphdr *iph = (struct iphdr *)(eth + 1);
if (iph + 1 > data_end)
return TC_ACT_SHOT;
ihl_len = iph->ihl * 4;
proto = iph->protocol;
tcp = (struct tcphdr *)((void *)(iph) + ihl_len);
} else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1);
if (ip6h + 1 > data_end)
return TC_ACT_SHOT;
ihl_len = sizeof(*ip6h);
proto = ip6h->nexthdr;
tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len);
}
if (test_pkt_access_subprog1(skb) != skb->len * 2)
return TC_ACT_SHOT;
if (test_pkt_access_subprog2(2, skb) != skb->len * 2)
return TC_ACT_SHOT;
if (test_pkt_access_subprog3(3, skb) != skb->len * 3 * skb->ifindex)
return TC_ACT_SHOT;
if (tcp) {
if (test_pkt_write_access_subprog(skb, (void *)tcp - data))
return TC_ACT_SHOT;
if (((void *)(tcp) + 20) > data_end || proto != 6)
return TC_ACT_SHOT;
barrier(); /* to force ordering of checks */
if (((void *)(tcp) + 18) > data_end)
return TC_ACT_SHOT;
if (tcp->urg_ptr == 123)
return TC_ACT_OK;
}
return TC_ACT_UNSPEC;
}
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