1 /* Copyright (c) 2016 Facebook 2 * 3 * This program is free software; you can redistribute it and/or 4 * modify it under the terms of version 2 of the GNU General Public 5 * License as published by the Free Software Foundation. 6 */ 7 #define KBUILD_MODNAME "foo" 8 #include <linux/ip.h> 9 #include <linux/ipv6.h> 10 #include <linux/in.h> 11 #include <linux/tcp.h> 12 #include <linux/udp.h> 13 #include <uapi/linux/bpf.h> 14 #include <net/ip.h> 15 #include <bpf/bpf_helpers.h> 16 17 #define DEFAULT_PKTGEN_UDP_PORT 9 18 19 /* copy of 'struct ethhdr' without __packed */ 20 struct eth_hdr { 21 unsigned char h_dest[ETH_ALEN]; 22 unsigned char h_source[ETH_ALEN]; 23 unsigned short h_proto; 24 }; 25 26 SEC("simple") 27 int handle_ingress(struct __sk_buff *skb) 28 { 29 void *data = (void *)(long)skb->data; 30 struct eth_hdr *eth = data; 31 struct iphdr *iph = data + sizeof(*eth); 32 struct udphdr *udp = data + sizeof(*eth) + sizeof(*iph); 33 void *data_end = (void *)(long)skb->data_end; 34 35 /* single length check */ 36 if (data + sizeof(*eth) + sizeof(*iph) + sizeof(*udp) > data_end) 37 return 0; 38 39 if (eth->h_proto != htons(ETH_P_IP)) 40 return 0; 41 if (iph->protocol != IPPROTO_UDP || iph->ihl != 5) 42 return 0; 43 if (ip_is_fragment(iph)) 44 return 0; 45 if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT)) 46 return TC_ACT_SHOT; 47 return 0; 48 } 49 char _license[] SEC("license") = "GPL"; 50