LXR linux/samples/bpf/tcbpf1

   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>
   7#include <uapi/linux/filter.h>
   8#include <uapi/linux/pkt_cls.h>
   9#include "bpf_helpers.h"
  10
  11/* compiler workaround */
  12#define _htonl __builtin_bswap32
  13
  14static 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
  19#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
  20#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
  21
  22static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
  23{
  24        __u8 old_tos = load_byte(skb, TOS_OFF);
  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
  35static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
  36{
  37        __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
  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))
  45static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
  46{
  47        __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
  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
  53SEC("classifier")
  54int bpf_prog1(struct __sk_buff *skb)
  55{
  56        __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
  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}
  67SEC("redirect_xmit")
  68int _redirect_xmit(struct __sk_buff *skb)
  69{
  70        return bpf_redirect(skb->ifindex + 1, 0);
  71}
  72SEC("redirect_recv")
  73int _redirect_recv(struct __sk_buff *skb)
  74{
  75        return bpf_redirect(skb->ifindex + 1, 1);
  76}
  77SEC("clone_redirect_xmit")
  78int _clone_redirect_xmit(struct __sk_buff *skb)
  79{
  80        bpf_clone_redirect(skb, skb->ifindex + 1, 0);
  81        return TC_ACT_SHOT;
  82}
  83SEC("clone_redirect_recv")
  84int _clone_redirect_recv(struct __sk_buff *skb)
  85{
  86        bpf_clone_redirect(skb, skb->ifindex + 1, 1);
  87        return TC_ACT_SHOT;
  88}
  89char _license[] SEC("license") = "GPL";
  90