66 lines
1.6 KiB
C
66 lines
1.6 KiB
C
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/* Copyright (c) 2017 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of version 2 of the GNU General Public
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* License as published by the Free Software Foundation.
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*/
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#include <stddef.h>
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#include <string.h>
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#include <linux/bpf.h>
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#include <linux/if_ether.h>
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#include <linux/if_packet.h>
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#include <linux/ip.h>
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#include <linux/ipv6.h>
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#include <linux/in.h>
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#include <linux/tcp.h>
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#include <linux/pkt_cls.h>
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#include "bpf_helpers.h"
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#include "bpf_endian.h"
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#define barrier() __asm__ __volatile__("": : :"memory")
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int _version SEC("version") = 1;
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SEC("test1")
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int process(struct __sk_buff *skb)
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{
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void *data_end = (void *)(long)skb->data_end;
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void *data = (void *)(long)skb->data;
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struct ethhdr *eth = (struct ethhdr *)(data);
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struct tcphdr *tcp = NULL;
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__u8 proto = 255;
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__u64 ihl_len;
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if (eth + 1 > data_end)
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return TC_ACT_SHOT;
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if (eth->h_proto == bpf_htons(ETH_P_IP)) {
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struct iphdr *iph = (struct iphdr *)(eth + 1);
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if (iph + 1 > data_end)
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return TC_ACT_SHOT;
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ihl_len = iph->ihl * 4;
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proto = iph->protocol;
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tcp = (struct tcphdr *)((void *)(iph) + ihl_len);
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} else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
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struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1);
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if (ip6h + 1 > data_end)
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return TC_ACT_SHOT;
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ihl_len = sizeof(*ip6h);
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proto = ip6h->nexthdr;
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tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len);
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}
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if (tcp) {
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if (((void *)(tcp) + 20) > data_end || proto != 6)
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return TC_ACT_SHOT;
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barrier(); /* to force ordering of checks */
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if (((void *)(tcp) + 18) > data_end)
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return TC_ACT_SHOT;
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if (tcp->urg_ptr == 123)
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return TC_ACT_OK;
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}
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return TC_ACT_UNSPEC;
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}
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