1 #include <uapi/linux/bpf.h> 2 #include <uapi/linux/if_ether.h> 3 #include <uapi/linux/if_packet.h> 4 #include <uapi/linux/ip.h> 5 #include <uapi/linux/in.h> 6 #include <uapi/linux/tcp.h> 7 #include "bpf_helpers.h" 8 9 /* compiler workaround */ 10 #define _htonl __builtin_bswap32 11 12 static inline void set_dst_mac(struct __sk_buff *skb, char *mac) 13 { 14 bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1); 15 } 16 17 /* use 1 below for ingress qdisc and 0 for egress */ 18 #if 0 19 #undef ETH_HLEN 20 #define ETH_HLEN 0 21 #endif 22 23 #define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check)) 24 #define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos)) 25 26 static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos) 27 { 28 __u8 old_tos = load_byte(skb, TOS_OFF); 29 30 bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2); 31 bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0); 32 } 33 34 #define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check)) 35 #define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr)) 36 37 #define IS_PSEUDO 0x10 38 39 static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip) 40 { 41 __u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF)); 42 43 bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip)); 44 bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip)); 45 bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0); 46 } 47 48 #define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest)) 49 static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port) 50 { 51 __u16 old_port = htons(load_half(skb, TCP_DPORT_OFF)); 52 53 bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port)); 54 bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0); 55 } 56 57 SEC("classifier") 58 int bpf_prog1(struct __sk_buff *skb) 59 { 60 __u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)); 61 long *value; 62 63 if (proto == IPPROTO_TCP) { 64 set_ip_tos(skb, 8); 65 set_tcp_ip_src(skb, 0xA010101); 66 set_tcp_dest_port(skb, 5001); 67 } 68 69 return 0; 70 } 71 char _license[] SEC("license") = "GPL"; 72