1 // SPDX-License-Identifier: GPL-2.0-only 2 /* Copyright (c) 2017 Facebook 3 */ 4 #include <stddef.h> 5 #include <string.h> 6 #include <linux/bpf.h> 7 #include <linux/if_ether.h> 8 #include <linux/if_packet.h> 9 #include <linux/ip.h> 10 #include <linux/ipv6.h> 11 #include <linux/in.h> 12 #include <linux/tcp.h> 13 #include <linux/pkt_cls.h> 14 #include "bpf_helpers.h" 15 #include "bpf_endian.h" 16 17 #define barrier() __asm__ __volatile__("": : :"memory") 18 int _version SEC("version") = 1; 19 20 SEC("test1") 21 int process(struct __sk_buff *skb) 22 { 23 void *data_end = (void *)(long)skb->data_end; 24 void *data = (void *)(long)skb->data; 25 struct ethhdr *eth = (struct ethhdr *)(data); 26 struct tcphdr *tcp = NULL; 27 __u8 proto = 255; 28 __u64 ihl_len; 29 30 if (eth + 1 > data_end) 31 return TC_ACT_SHOT; 32 33 if (eth->h_proto == bpf_htons(ETH_P_IP)) { 34 struct iphdr *iph = (struct iphdr *)(eth + 1); 35 36 if (iph + 1 > data_end) 37 return TC_ACT_SHOT; 38 ihl_len = iph->ihl * 4; 39 proto = iph->protocol; 40 tcp = (struct tcphdr *)((void *)(iph) + ihl_len); 41 } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) { 42 struct ipv6hdr *ip6h = (struct ipv6hdr *)(eth + 1); 43 44 if (ip6h + 1 > data_end) 45 return TC_ACT_SHOT; 46 ihl_len = sizeof(*ip6h); 47 proto = ip6h->nexthdr; 48 tcp = (struct tcphdr *)((void *)(ip6h) + ihl_len); 49 } 50 51 if (tcp) { 52 if (((void *)(tcp) + 20) > data_end || proto != 6) 53 return TC_ACT_SHOT; 54 barrier(); /* to force ordering of checks */ 55 if (((void *)(tcp) + 18) > data_end) 56 return TC_ACT_SHOT; 57 if (tcp->urg_ptr == 123) 58 return TC_ACT_OK; 59 } 60 61 return TC_ACT_UNSPEC; 62 } 63