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/bpf_helpers.h>
  11#include "bpf_legacy.h"
  12
  13/* compiler workaround */
  14#define _htonl __builtin_bswap32
  15
  16static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
  17{
  18        bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
  19}
  20
  21#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
  22#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
  23
  24static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
  25{
  26        __u8 old_tos = load_byte(skb, TOS_OFF);
  27
  28        bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
  29        bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
  30}
  31
  32#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
  33#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))
  34
  35#define IS_PSEUDO 0x10
  36
  37static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
  38{
  39        __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
  40
  41        bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
  42        bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
  43        bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
  44}
  45
  46#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
  47static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
  48{
  49        __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
  50
  51        bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
  52        bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
  53}
  54
  55SEC("classifier")
  56int bpf_prog1(struct __sk_buff *skb)
  57{
  58        __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
  59        long *value;
  60
  61        if (proto == IPPROTO_TCP) {
  62                set_ip_tos(skb, 8);
  63                set_tcp_ip_src(skb, 0xA010101);
  64                set_tcp_dest_port(skb, 5001);
  65        }
  66
  67        return 0;
  68}
  69SEC("redirect_xmit")
  70int _redirect_xmit(struct __sk_buff *skb)
  71{
  72        return bpf_redirect(skb->ifindex + 1, 0);
  73}
  74SEC("redirect_recv")
  75int _redirect_recv(struct __sk_buff *skb)
  76{
  77        return bpf_redirect(skb->ifindex + 1, 1);
  78}
  79SEC("clone_redirect_xmit")
  80int _clone_redirect_xmit(struct __sk_buff *skb)
  81{
  82        bpf_clone_redirect(skb, skb->ifindex + 1, 0);
  83        return TC_ACT_SHOT;
  84}
  85SEC("clone_redirect_recv")
  86int _clone_redirect_recv(struct __sk_buff *skb)
  87{
  88        bpf_clone_redirect(skb, skb->ifindex + 1, 1);
  89        return TC_ACT_SHOT;
  90}
  91char _license[] SEC("license") = "GPL";
  92