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 <bpf/bpf_helpers.h> 15 #include "bpf_legacy.h" 16 17 #define DEFAULT_PKTGEN_UDP_PORT 9 18 #define IP_MF 0x2000 19 #define IP_OFFSET 0x1FFF 20 21 static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff) 22 { 23 return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off)) 24 & (IP_MF | IP_OFFSET); 25 } 26 27 SEC("ldabs") 28 int handle_ingress(struct __sk_buff *skb) 29 { 30 __u64 troff = ETH_HLEN + sizeof(struct iphdr); 31 32 if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP) 33 return 0; 34 if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP || 35 load_byte(skb, ETH_HLEN) != 0x45) 36 return 0; 37 if (ip_is_fragment(skb, ETH_HLEN)) 38 return 0; 39 if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT) 40 return TC_ACT_SHOT; 41 return 0; 42 } 43 char _license[] SEC("license") = "GPL"; 44