1 /*
2  * Copyright (C) 2019 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 #pragma once
18 
19 #include <linux/bpf.h>
20 #include <linux/if_packet.h>
21 #include <stdbool.h>
22 #include <stdint.h>
23 
24 // this returns 0 iff skb->sk is NULL
25 static uint64_t (*bpf_get_socket_cookie)(struct __sk_buff* skb) = (void*)BPF_FUNC_get_socket_cookie;
26 
27 static uint32_t (*bpf_get_socket_uid)(struct __sk_buff* skb) = (void*)BPF_FUNC_get_socket_uid;
28 
29 static int (*bpf_skb_pull_data)(struct __sk_buff* skb, __u32 len) = (void*)BPF_FUNC_skb_pull_data;
30 
31 static int (*bpf_skb_load_bytes)(struct __sk_buff* skb, int off, void* to,
32                                  int len) = (void*)BPF_FUNC_skb_load_bytes;
33 
34 static int (*bpf_skb_store_bytes)(struct __sk_buff* skb, __u32 offset, const void* from, __u32 len,
35                                   __u64 flags) = (void*)BPF_FUNC_skb_store_bytes;
36 
37 static int64_t (*bpf_csum_diff)(__be32* from, __u32 from_size, __be32* to, __u32 to_size,
38                                 __wsum seed) = (void*)BPF_FUNC_csum_diff;
39 
40 static int64_t (*bpf_csum_update)(struct __sk_buff* skb, __wsum csum) = (void*)BPF_FUNC_csum_update;
41 
42 static int (*bpf_skb_change_proto)(struct __sk_buff* skb, __be16 proto,
43                                    __u64 flags) = (void*)BPF_FUNC_skb_change_proto;
44 static int (*bpf_l3_csum_replace)(struct __sk_buff* skb, __u32 offset, __u64 from, __u64 to,
45                                   __u64 flags) = (void*)BPF_FUNC_l3_csum_replace;
46 static int (*bpf_l4_csum_replace)(struct __sk_buff* skb, __u32 offset, __u64 from, __u64 to,
47                                   __u64 flags) = (void*)BPF_FUNC_l4_csum_replace;
48 static int (*bpf_redirect)(__u32 ifindex, __u64 flags) = (void*)BPF_FUNC_redirect;
49 static int (*bpf_redirect_map)(const struct bpf_map_def* map, __u32 key,
50                                __u64 flags) = (void*)BPF_FUNC_redirect_map;
51 
52 static int (*bpf_skb_change_head)(struct __sk_buff* skb, __u32 head_room,
53                                   __u64 flags) = (void*)BPF_FUNC_skb_change_head;
54 static int (*bpf_skb_adjust_room)(struct __sk_buff* skb, __s32 len_diff, __u32 mode,
55                                   __u64 flags) = (void*)BPF_FUNC_skb_adjust_room;
56 
57 // Android only supports little endian architectures
58 #define htons(x) (__builtin_constant_p(x) ? ___constant_swab16(x) : __builtin_bswap16(x))
59 #define htonl(x) (__builtin_constant_p(x) ? ___constant_swab32(x) : __builtin_bswap32(x))
60 #define ntohs(x) htons(x)
61 #define ntohl(x) htonl(x)
62 
63 static inline __always_inline __unused bool is_received_skb(struct __sk_buff* skb) {
64     return skb->pkt_type == PACKET_HOST || skb->pkt_type == PACKET_BROADCAST ||
65            skb->pkt_type == PACKET_MULTICAST;
66 }
67 
68 // try to make the first 'len' header bytes readable via direct packet access
69 static inline __always_inline void try_make_readable(struct __sk_buff* skb, int len) {
70     if (len > skb->len) len = skb->len;
71     if (skb->data_end - skb->data < len) bpf_skb_pull_data(skb, len);
72 }
73