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// SPDX-License-Identifier: GPL-2.0
// Copyright (c) 2019 Facebook
#include <linux/bpf.h>
#include <stdbool.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#include <bpf/bpf_tracing.h>
char _license[] SEC("license") = "GPL";
struct {
__uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
__type(key, int);
__type(value, int);
} perf_buf_map SEC(".maps");
#define _(P) (__builtin_preserve_access_index(P))
/* define few struct-s that bpf program needs to access */
struct callback_head {
struct callback_head *next;
void (*func)(struct callback_head *head);
};
struct dev_ifalias {
struct callback_head rcuhead;
};
struct net_device /* same as kernel's struct net_device */ {
int ifindex;
struct dev_ifalias *ifalias;
};
typedef struct {
int counter;
} atomic_t;
typedef struct refcount_struct {
atomic_t refs;
} refcount_t;
struct sk_buff {
/* field names and sizes should match to those in the kernel */
unsigned int len, data_len;
__u16 mac_len, hdr_len, queue_mapping;
struct net_device *dev;
/* order of the fields doesn't matter */
refcount_t users;
unsigned char *data;
char __pkt_type_offset[0];
char cb[48];
};
struct meta {
int ifindex;
__u32 cb32_0;
__u8 cb8_0;
};
/* TRACE_EVENT(kfree_skb,
* TP_PROTO(struct sk_buff *skb, void *location),
*/
SEC("tp_btf/kfree_skb")
int BPF_PROG(trace_kfree_skb, struct sk_buff *skb, void *location)
{
struct net_device *dev;
struct callback_head *ptr;
void *func;
int users;
unsigned char *data;
unsigned short pkt_data;
struct meta meta = {};
char pkt_type;
__u32 *cb32;
__u8 *cb8;
__builtin_preserve_access_index(({
users = skb->users.refs.counter;
data = skb->data;
dev = skb->dev;
ptr = dev->ifalias->rcuhead.next;
func = ptr->func;
cb8 = (__u8 *)&skb->cb;
cb32 = (__u32 *)&skb->cb;
}));
meta.ifindex = _(dev->ifindex);
meta.cb8_0 = cb8[8];
meta.cb32_0 = cb32[2];
bpf_probe_read_kernel(&pkt_type, sizeof(pkt_type), _(&skb->__pkt_type_offset));
pkt_type &= 7;
/* read eth proto */
bpf_probe_read_kernel(&pkt_data, sizeof(pkt_data), data + 12);
bpf_printk("rcuhead.next %llx func %llx\n", ptr, func);
bpf_printk("skb->len %d users %d pkt_type %x\n",
_(skb->len), users, pkt_type);
bpf_printk("skb->queue_mapping %d\n", _(skb->queue_mapping));
bpf_printk("dev->ifindex %d data %llx pkt_data %x\n",
meta.ifindex, data, pkt_data);
bpf_printk("cb8_0:%x cb32_0:%x\n", meta.cb8_0, meta.cb32_0);
if (users != 1 || pkt_data != bpf_htons(0x86dd) || meta.ifindex != 1)
/* raw tp ignores return value */
return 0;
/* send first 72 byte of the packet to user space */
bpf_skb_output(skb, &perf_buf_map, (72ull << 32) | BPF_F_CURRENT_CPU,
&meta, sizeof(meta));
return 0;
}
struct {
bool fentry_test_ok;
bool fexit_test_ok;
} result = {};
SEC("fentry/eth_type_trans")
int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
unsigned short protocol)
{
int len, ifindex;
__builtin_preserve_access_index(({
len = skb->len;
ifindex = dev->ifindex;
}));
/* fentry sees full packet including L2 header */
if (len != 74 || ifindex != 1)
return 0;
result.fentry_test_ok = true;
return 0;
}
SEC("fexit/eth_type_trans")
int BPF_PROG(fexit_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
unsigned short protocol)
{
int len, ifindex;
__builtin_preserve_access_index(({
len = skb->len;
ifindex = dev->ifindex;
}));
/* fexit sees packet without L2 header that eth_type_trans should have
* consumed.
*/
if (len != 60 || protocol != bpf_htons(0x86dd) || ifindex != 1)
return 0;
result.fexit_test_ok = true;
return 0;
}
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