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