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"; 91