forked from Minki/linux
72 lines
2.0 KiB
C
72 lines
2.0 KiB
C
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#include <uapi/linux/bpf.h>
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#include <uapi/linux/if_ether.h>
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#include <uapi/linux/if_packet.h>
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#include <uapi/linux/ip.h>
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#include <uapi/linux/in.h>
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#include <uapi/linux/tcp.h>
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#include "bpf_helpers.h"
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/* compiler workaround */
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#define _htonl __builtin_bswap32
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static inline void set_dst_mac(struct __sk_buff *skb, char *mac)
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{
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bpf_skb_store_bytes(skb, 0, mac, ETH_ALEN, 1);
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}
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/* use 1 below for ingress qdisc and 0 for egress */
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#if 0
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#undef ETH_HLEN
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#define ETH_HLEN 0
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#endif
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#define IP_CSUM_OFF (ETH_HLEN + offsetof(struct iphdr, check))
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#define TOS_OFF (ETH_HLEN + offsetof(struct iphdr, tos))
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static inline void set_ip_tos(struct __sk_buff *skb, __u8 new_tos)
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{
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__u8 old_tos = load_byte(skb, TOS_OFF);
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, htons(old_tos), htons(new_tos), 2);
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bpf_skb_store_bytes(skb, TOS_OFF, &new_tos, sizeof(new_tos), 0);
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}
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#define TCP_CSUM_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, check))
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#define IP_SRC_OFF (ETH_HLEN + offsetof(struct iphdr, saddr))
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#define IS_PSEUDO 0x10
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static inline void set_tcp_ip_src(struct __sk_buff *skb, __u32 new_ip)
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{
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__u32 old_ip = _htonl(load_word(skb, IP_SRC_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_ip, new_ip, IS_PSEUDO | sizeof(new_ip));
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bpf_l3_csum_replace(skb, IP_CSUM_OFF, old_ip, new_ip, sizeof(new_ip));
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bpf_skb_store_bytes(skb, IP_SRC_OFF, &new_ip, sizeof(new_ip), 0);
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}
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#define TCP_DPORT_OFF (ETH_HLEN + sizeof(struct iphdr) + offsetof(struct tcphdr, dest))
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static inline void set_tcp_dest_port(struct __sk_buff *skb, __u16 new_port)
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{
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__u16 old_port = htons(load_half(skb, TCP_DPORT_OFF));
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bpf_l4_csum_replace(skb, TCP_CSUM_OFF, old_port, new_port, sizeof(new_port));
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bpf_skb_store_bytes(skb, TCP_DPORT_OFF, &new_port, sizeof(new_port), 0);
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}
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SEC("classifier")
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int bpf_prog1(struct __sk_buff *skb)
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{
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__u8 proto = load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol));
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long *value;
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if (proto == IPPROTO_TCP) {
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set_ip_tos(skb, 8);
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set_tcp_ip_src(skb, 0xA010101);
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set_tcp_dest_port(skb, 5001);
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}
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return 0;
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}
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char _license[] SEC("license") = "GPL";
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