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"; 92