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26 results

parse_simple.c

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  • parse_simple.c 1.27 KiB
    /* Copyright (c) 2016 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.
     */
    #define KBUILD_MODNAME "foo"
    #include <linux/ip.h>
    #include <linux/ipv6.h>
    #include <linux/in.h>
    #include <linux/tcp.h>
    #include <linux/udp.h>
    #include <uapi/linux/bpf.h>
    #include <net/ip.h>
    #include "bpf_helpers.h"
    
    #define DEFAULT_PKTGEN_UDP_PORT 9
    
    /* copy of 'struct ethhdr' without __packed */
    struct eth_hdr {
    	unsigned char   h_dest[ETH_ALEN];
    	unsigned char   h_source[ETH_ALEN];
    	unsigned short  h_proto;
    };
    
    SEC("simple")
    int handle_ingress(struct __sk_buff *skb)
    {
    	void *data = (void *)(long)skb->data;
    	struct eth_hdr *eth = data;
    	struct iphdr *iph = data + sizeof(*eth);
    	struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph);
    	void *data_end = (void *)(long)skb->data_end;
    
    	/* single length check */
    	if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end)
    		return 0;
    
    	if (eth->h_proto != htons(ETH_P_IP))
    		return 0;
    	if (iph->protocol != IPPROTO_UDP || iph->ihl != 5)
    		return 0;
    	if (ip_is_fragment(iph))
    		return 0;
    	if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT))
    		return TC_ACT_SHOT;
    	return 0;
    }
    char _license[] SEC("license") = "GPL";