LXR linux/samples/bpf/tcbpf1

   1#define KBUILD_MODNAME "foo"
   2#include <uapi/linux/bpf.h>
   3#include <uapi/linux/if_ether.h>
   4#include <uapi/linux/if_packet.h>
   5#include <uapi/linux/ip.h>
   6#include <uapi/linux/in.h>
   7#include <uapi/linux/tcp.h>
   8#include <uapi/linux/filter.h>
   9#include <uapi/linux/pkt_cls.h>
  10#include "bpf_helpers.h"
  11
  12/* compiler workaround */
  13#define _htonl __builtin_bswap32
  14
  15static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
  16{
  17        bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
  18}
  19
  20#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
  21#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
  22
  23static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
  24{
  25        __u8 old_tos = load_byte(skb, TOS_OFF);
  26
  27        bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
  28        bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
  29}
  30
  31#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
  32#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))
  33
  34#define IS_PSEUDO 0x10
  35
  36static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
  37{
  38        __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
  39
  40        bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
  41        bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
  42        bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
  43}
  44
  45#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
  46static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
  47{
  48        __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
  49
  50        bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
  51        bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
  52}
  53
  54SEC("classifier")
  55int bpf_prog1(struct __sk_buff *skb)
  56{
  57        __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
  58        long *value;
  59
  60        if (proto == IPPROTO_TCP) {
  61                set_ip_tos(skb, 8);
  62                set_tcp_ip_src(skb, 0xA010101);
  63                set_tcp_dest_port(skb, 5001);
  64        }
  65
  66        return 0;
  67}
  68SEC("redirect_xmit")
  69int _redirect_xmit(struct __sk_buff *skb)
  70{
  71        return bpf_redirect(skb->ifindex + 1, 0);
  72}
  73SEC("redirect_recv")
  74int _redirect_recv(struct __sk_buff *skb)
  75{
  76        return bpf_redirect(skb->ifindex + 1, 1);
  77}
  78SEC("clone_redirect_xmit")
  79int _clone_redirect_xmit(struct __sk_buff *skb)
  80{
  81        bpf_clone_redirect(skb, skb->ifindex + 1, 0);
  82        return TC_ACT_SHOT;
  83}
  84SEC("clone_redirect_recv")
  85int _clone_redirect_recv(struct __sk_buff *skb)
  86{
  87        bpf_clone_redirect(skb, skb->ifindex + 1, 1);
  88        return TC_ACT_SHOT;
  89}
  90char _license[] SEC("license") = "GPL";
  91