tools/testing/selftests/bpf/progs/kfree_skb.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 // Copyright (c) 2019 Facebook
   3 #include <linux/bpf.h>
   4 #include <stdbool.h>
   5 #include <bpf/bpf_helpers.h>
   6 #include <bpf/bpf_endian.h>
   7 #include "bpf_trace_helpers.h"
   8
   9 char _license[] SEC("license") = "GPL";
  10 struct {
  11         __uint(type, BPF_MAP_TYPE_PERF_EVENT_ARRAY);
  12         __uint(key_size, sizeof(int));
  13         __uint(value_size, sizeof(int));
  14 } perf_buf_map SEC(".maps");
  15
  16 #define _(P) (__builtin_preserve_access_index(P))
  17
  18 /* define few struct-s that bpf program needs to access */
  19 struct callback_head {
  20         struct callback_head *next;
  21         void (*func)(struct callback_head *head);
  22 };
  23 struct dev_ifalias {
  24         struct callback_head rcuhead;
  25 };
  26
  27 struct net_device /* same as kernel's struct net_device */ {
  28         int ifindex;
  29         struct dev_ifalias *ifalias;
  30 };
  31
  32 typedef struct {
  33         int counter;
  34 } atomic_t;
  35 typedef struct refcount_struct {
  36         atomic_t refs;
  37 } refcount_t;
  38
  39 struct sk_buff {
  40         /* field names and sizes should match to those in the kernel */
  41         unsigned int len, data_len;
  42         __u16 mac_len, hdr_len, queue_mapping;
  43         struct net_device *dev;
  44         /* order of the fields doesn't matter */
  45         refcount_t users;
  46         unsigned char *data;
  47         char __pkt_type_offset[0];
  48         char cb[48];
  49 };
  50
  51 struct meta {
  52         int ifindex;
  53         __u32 cb32_0;
  54         __u8 cb8_0;
  55 };
  56
  57 /* TRACE_EVENT(kfree_skb,
  58  *         TP_PROTO(struct sk_buff *skb, void *location),
  59  */
  60 SEC("tp_btf/kfree_skb")
  61 int BPF_PROG(trace_kfree_skb, struct sk_buff *skb, void *location)
  62 {
  63         struct net_device *dev;
  64         struct callback_head *ptr;
  65         void *func;
  66         int users;
  67         unsigned char *data;
  68         unsigned short pkt_data;
  69         struct meta meta = {};
  70         char pkt_type;
  71         __u32 *cb32;
  72         __u8 *cb8;
  73
  74         __builtin_preserve_access_index(({
  75                 users = skb->users.refs.counter;
  76                 data = skb->data;
  77                 dev = skb->dev;
  78                 ptr = dev->ifalias->rcuhead.next;
  79                 func = ptr->func;
  80                 cb8 = (__u8 *)&skb->cb;
  81                 cb32 = (__u32 *)&skb->cb;
  82         }));
  83
  84         meta.ifindex = _(dev->ifindex);
  85         meta.cb8_0 = cb8[8];
  86         meta.cb32_0 = cb32[2];
  87
  88         bpf_probe_read_kernel(&pkt_type, sizeof(pkt_type), _(&skb->__pkt_type_offset));
  89         pkt_type &= 7;
  90
  91         /* read eth proto */
  92         bpf_probe_read_kernel(&pkt_data, sizeof(pkt_data), data + 12);
  93
  94         bpf_printk("rcuhead.next %llx func %llx\n", ptr, func);
  95         bpf_printk("skb->len %d users %d pkt_type %x\n",
  96                    _(skb->len), users, pkt_type);
  97         bpf_printk("skb->queue_mapping %d\n", _(skb->queue_mapping));
  98         bpf_printk("dev->ifindex %d data %llx pkt_data %x\n",
  99                    meta.ifindex, data, pkt_data);
 100         bpf_printk("cb8_0:%x cb32_0:%x\n", meta.cb8_0, meta.cb32_0);
 101
 102         if (users != 1 || pkt_data != bpf_htons(0x86dd) || meta.ifindex != 1)
 103                 /* raw tp ignores return value */
 104                 return 0;
 105
 106         /* send first 72 byte of the packet to user space */
 107         bpf_skb_output(skb, &perf_buf_map, (72ull << 32) | BPF_F_CURRENT_CPU,
 108                        &meta, sizeof(meta));
 109         return 0;
 110 }
 111
 112 static volatile struct {
 113         bool fentry_test_ok;
 114         bool fexit_test_ok;
 115 } result;
 116
 117 SEC("fentry/eth_type_trans")
 118 int BPF_PROG(fentry_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
 119              unsigned short protocol)
 120 {
 121         int len, ifindex;
 122
 123         __builtin_preserve_access_index(({
 124                 len = skb->len;
 125                 ifindex = dev->ifindex;
 126         }));
 127
 128         /* fentry sees full packet including L2 header */
 129         if (len != 74 || ifindex != 1)
 130                 return 0;
 131         result.fentry_test_ok = true;
 132         return 0;
 133 }
 134
 135 SEC("fexit/eth_type_trans")
 136 int BPF_PROG(fexit_eth_type_trans, struct sk_buff *skb, struct net_device *dev,
 137              unsigned short protocol)
 138 {
 139         int len, ifindex;
 140
 141         __builtin_preserve_access_index(({
 142                 len = skb->len;
 143                 ifindex = dev->ifindex;
 144         }));
 145
 146         /* fexit sees packet without L2 header that eth_type_trans should have
 147          * consumed.
 148          */
 149         if (len != 60 || protocol != bpf_htons(0x86dd) || ifindex != 1)
 150                 return 0;
 151         result.fexit_test_ok = true;
 152         return 0;
 153 }