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91bc4822 AS |
1 | #include <uapi/linux/bpf.h> |
2 | #include <uapi/linux/if_ether.h> | |
3 | #include <uapi/linux/if_packet.h> | |
4 | #include <uapi/linux/ip.h> | |
5 | #include <uapi/linux/in.h> | |
6 | #include <uapi/linux/tcp.h> | |
a166151c AS |
7 | #include <uapi/linux/filter.h> |
8 | ||
91bc4822 AS |
9 | #include "bpf_helpers.h" |
10 | ||
11 | /* compiler workaround */ | |
12 | #define _htonl __builtin_bswap32 | |
13 | ||
14 | static inline void set_dst_mac(struct __sk_buff *skb, char *mac) | |
15 | { | |
16 | bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1); | |
17 | } | |
18 | ||
91bc4822 AS |
19 | #define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check)) |
20 | #define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos)) | |
21 | ||
22 | static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos) | |
23 | { | |
3431205e | 24 | __u8 old_tos = load_byte(skb, TOS_OFF); |
91bc4822 AS |
25 | |
26 | bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2); | |
27 | bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0); | |
28 | } | |
29 | ||
30 | #define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check)) | |
31 | #define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr)) | |
32 | ||
33 | #define IS_PSEUDO 0x10 | |
34 | ||
35 | static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip) | |
36 | { | |
3431205e | 37 | __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF)); |
91bc4822 AS |
38 | |
39 | bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip)); | |
40 | bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip)); | |
41 | bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0); | |
42 | } | |
43 | ||
44 | #define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest)) | |
45 | static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port) | |
46 | { | |
3431205e | 47 | __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF)); |
91bc4822 AS |
48 | |
49 | bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port)); | |
50 | bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0); | |
51 | } | |
52 | ||
53 | SEC("classifier") | |
54 | int bpf_prog1(struct __sk_buff *skb) | |
55 | { | |
3431205e | 56 | __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)); |
91bc4822 AS |
57 | long *value; |
58 | ||
59 | if (proto == IPPROTO_TCP) { | |
60 | set_ip_tos(skb, 8); | |
61 | set_tcp_ip_src(skb, 0xA010101); | |
62 | set_tcp_dest_port(skb, 5001); | |
63 | } | |
64 | ||
65 | return 0; | |
66 | } | |
67 | char _license[] SEC("license") = "GPL"; |