tcbpf1_kern.c 2.53 KB
Newer Older
1
#define KBUILD_MODNAME "foo"
2 3 4 5 6 7
#include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/if_packet.h>
#include <uapi/linux/ip.h>
#include <uapi/linux/in.h>
#include <uapi/linux/tcp.h>
8
#include <uapi/linux/filter.h>
9
#include <uapi/linux/pkt_cls.h>
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
#include "bpf_helpers.h"

/* compiler workaround */
#define _htonl __builtin_bswap32

static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
{
	bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
}

#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))

static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
{
25
	__u8 old_tos = load_byte(skb, TOS_OFF);
26 27 28 29 30 31 32 33 34 35 36 37

	bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
	bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
}

#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))

#define IS_PSEUDO 0x10

static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
{
38
	__u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
39 40 41 42 43 44 45 46 47

	bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
	bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
	bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
}

#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
{
48
	__u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
49 50 51 52 53 54 55 56

	bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
	bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
}

SEC("classifier")
int bpf_prog1(struct __sk_buff *skb)
{
57
	__u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
58 59 60 61 62 63 64 65 66 67
	long *value;

	if (proto == IPPROTO_TCP) {
		set_ip_tos(skb, 8);
		set_tcp_ip_src(skb, 0xA010101);
		set_tcp_dest_port(skb, 5001);
	}

	return 0;
}
68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89
SEC("redirect_xmit")
int _redirect_xmit(struct __sk_buff *skb)
{
	return bpf_redirect(skb->ifindex + 1, 0);
}
SEC("redirect_recv")
int _redirect_recv(struct __sk_buff *skb)
{
	return bpf_redirect(skb->ifindex + 1, 1);
}
SEC("clone_redirect_xmit")
int _clone_redirect_xmit(struct __sk_buff *skb)
{
	bpf_clone_redirect(skb, skb->ifindex + 1, 0);
	return TC_ACT_SHOT;
}
SEC("clone_redirect_recv")
int _clone_redirect_recv(struct __sk_buff *skb)
{
	bpf_clone_redirect(skb, skb->ifindex + 1, 1);
	return TC_ACT_SHOT;
}
90
char _license[] SEC("license") = "GPL";