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 #include "bpf_legacy.h"
  12
  13 /* compiler workaround */
  14 #define _htonl __builtin_bswap32
  15
  16 static 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
  24 static 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
  37 static 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))
  47 static 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
  55 SEC("classifier")
  56 int 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 }
  69 SEC("redirect_xmit")
  70 int _redirect_xmit(struct __sk_buff *skb)
  71 {
  72         return bpf_redirect(skb->ifindex + 1, 0);
  73 }
  74 SEC("redirect_recv")
  75 int _redirect_recv(struct __sk_buff *skb)
  76 {
  77         return bpf_redirect(skb->ifindex + 1, 1);
  78 }
  79 SEC("clone_redirect_xmit")
  80 int _clone_redirect_xmit(struct __sk_buff *skb)
  81 {
  82         bpf_clone_redirect(skb, skb->ifindex + 1, 0);
  83         return TC_ACT_SHOT;
  84 }
  85 SEC("clone_redirect_recv")
  86 int _clone_redirect_recv(struct __sk_buff *skb)
  87 {
  88         bpf_clone_redirect(skb, skb->ifindex + 1, 1);
  89         return TC_ACT_SHOT;
  90 }
  91 char _license[] SEC("license") = "GPL";