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/if_ether.h>
  9#include <linux/if_vlan.h>
 10#include <linux/ip.h>
 11#include <linux/ipv6.h>
 12#include <linux/in.h>
 13#include <linux/tcp.h>
 14#include <linux/udp.h>
 15#include <uapi/linux/bpf.h>
 16#include <net/ip.h>
 17#include <bpf/bpf_helpers.h>
 18
 19#define DEFAULT_PKTGEN_UDP_PORT 9
 20#define DEBUG 0
 21
 22static int tcp(void *data, uint64_t tp_off, void *data_end)
 23{
 24	struct tcphdr *tcp = data + tp_off;
 25
 26	if (tcp + 1 > data_end)
 27		return 0;
 28	if (tcp->dest == htons(80) || tcp->source == htons(80))
 29		return TC_ACT_SHOT;
 30	return 0;
 31}
 32
 33static int udp(void *data, uint64_t tp_off, void *data_end)
 34{
 35	struct udphdr *udp = data + tp_off;
 36
 37	if (udp + 1 > data_end)
 38		return 0;
 39	if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT) ||
 40	    udp->source == htons(DEFAULT_PKTGEN_UDP_PORT)) {
 41		if (DEBUG) {
 42			char fmt[] = "udp port 9 indeed\n";
 43
 44			bpf_trace_printk(fmt, sizeof(fmt));
 45		}
 46		return TC_ACT_SHOT;
 47	}
 48	return 0;
 49}
 50
 51static int parse_ipv4(void *data, uint64_t nh_off, void *data_end)
 52{
 53	struct iphdr *iph;
 54	uint64_t ihl_len;
 55
 56	iph = data + nh_off;
 57	if (iph + 1 > data_end)
 58		return 0;
 59
 60	if (ip_is_fragment(iph))
 61		return 0;
 62	ihl_len = iph->ihl * 4;
 63
 64	if (iph->protocol == IPPROTO_IPIP) {
 65		iph = data + nh_off + ihl_len;
 66		if (iph + 1 > data_end)
 67			return 0;
 68		ihl_len += iph->ihl * 4;
 69	}
 70
 71	if (iph->protocol == IPPROTO_TCP)
 72		return tcp(data, nh_off + ihl_len, data_end);
 73	else if (iph->protocol == IPPROTO_UDP)
 74		return udp(data, nh_off + ihl_len, data_end);
 75	return 0;
 76}
 77
 78static int parse_ipv6(void *data, uint64_t nh_off, void *data_end)
 79{
 80	struct ipv6hdr *ip6h;
 81	struct iphdr *iph;
 82	uint64_t ihl_len = sizeof(struct ipv6hdr);
 83	uint64_t nexthdr;
 84
 85	ip6h = data + nh_off;
 86	if (ip6h + 1 > data_end)
 87		return 0;
 88
 89	nexthdr = ip6h->nexthdr;
 90
 91	if (nexthdr == IPPROTO_IPIP) {
 92		iph = data + nh_off + ihl_len;
 93		if (iph + 1 > data_end)
 94			return 0;
 95		ihl_len += iph->ihl * 4;
 96		nexthdr = iph->protocol;
 97	} else if (nexthdr == IPPROTO_IPV6) {
 98		ip6h = data + nh_off + ihl_len;
 99		if (ip6h + 1 > data_end)
100			return 0;
101		ihl_len += sizeof(struct ipv6hdr);
102		nexthdr = ip6h->nexthdr;
103	}
104
105	if (nexthdr == IPPROTO_TCP)
106		return tcp(data, nh_off + ihl_len, data_end);
107	else if (nexthdr == IPPROTO_UDP)
108		return udp(data, nh_off + ihl_len, data_end);
109	return 0;
110}
111
112SEC("varlen")
113int handle_ingress(struct __sk_buff *skb)
114{
115	void *data = (void *)(long)skb->data;
116	struct ethhdr *eth = data;
117	void *data_end = (void *)(long)skb->data_end;
118	uint64_t h_proto, nh_off;
119
120	nh_off = sizeof(*eth);
121	if (data + nh_off > data_end)
122		return 0;
123
124	h_proto = eth->h_proto;
125
126	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
127		struct vlan_hdr *vhdr;
128
129		vhdr = data + nh_off;
130		nh_off += sizeof(struct vlan_hdr);
131		if (data + nh_off > data_end)
132			return 0;
133		h_proto = vhdr->h_vlan_encapsulated_proto;
134	}
135	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
136		struct vlan_hdr *vhdr;
137
138		vhdr = data + nh_off;
139		nh_off += sizeof(struct vlan_hdr);
140		if (data + nh_off > data_end)
141			return 0;
142		h_proto = vhdr->h_vlan_encapsulated_proto;
143	}
144	if (h_proto == htons(ETH_P_IP))
145		return parse_ipv4(data, nh_off, data_end);
146	else if (h_proto == htons(ETH_P_IPV6))
147		return parse_ipv6(data, nh_off, data_end);
148	return 0;
149}
150char _license[] SEC("license") = "GPL";