92 lines · 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/bpf_helpers.h>11#include "bpf_legacy.h"12 13/* compiler workaround */14#define _htonl __builtin_bswap3215 16static 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 24static 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 0x1036 37static 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))47static 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 55SEC("classifier")56int 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}69SEC("redirect_xmit")70int _redirect_xmit(struct __sk_buff *skb)71{72 return bpf_redirect(skb->ifindex + 1, 0);73}74SEC("redirect_recv")75int _redirect_recv(struct __sk_buff *skb)76{77 return bpf_redirect(skb->ifindex + 1, 1);78}79SEC("clone_redirect_xmit")80int _clone_redirect_xmit(struct __sk_buff *skb)81{82 bpf_clone_redirect(skb, skb->ifindex + 1, 0);83 return TC_ACT_SHOT;84}85SEC("clone_redirect_recv")86int _clone_redirect_recv(struct __sk_buff *skb)87{88 bpf_clone_redirect(skb, skb->ifindex + 1, 1);89 return TC_ACT_SHOT;90}91char _license[] SEC("license") = "GPL";92