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 #include <linux/ip.h> 8 #include <linux/ipv6.h> 9 #include <linux/in.h> 10 #include <linux/tcp.h> 11 #include <linux/udp.h> 12 #include <uapi/linux/bpf.h> 13 #include "bpf_helpers.h" 14 15 #define DEFAULT_PKTGEN_UDP_PORT 9 16 #define IP_MF 0x2000 17 #define IP_OFFSET 0x1FFF 18 19 static inline int ip_is_fragment(struct __sk_buff *ctx, __u64 nhoff) 20 { 21 return load_half(ctx, nhoff + offsetof(struct iphdr, frag_off)) 22 & (IP_MF | IP_OFFSET); 23 } 24 25 SEC("ldabs") 26 int handle_ingress(struct __sk_buff *skb) 27 { 28 __u64 troff = ETH_HLEN + sizeof(struct iphdr); 29 30 if (load_half(skb, offsetof(struct ethhdr, h_proto)) != ETH_P_IP) 31 return 0; 32 if (load_byte(skb, ETH_HLEN + offsetof(struct iphdr, protocol)) != IPPROTO_UDP || 33 load_byte(skb, ETH_HLEN) != 0x45) 34 return 0; 35 if (ip_is_fragment(skb, ETH_HLEN)) 36 return 0; 37 if (load_half(skb, troff + offsetof(struct udphdr, dest)) == DEFAULT_PKTGEN_UDP_PORT) 38 return TC_ACT_SHOT; 39 return 0; 40 } 41 char _license[] SEC("license") = "GPL"; 42