samples/bpf/tcbpf1_kern.c

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