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/ip.h>
 10#include <linux/ipv6.h>
 11#include <linux/in.h>
 12#include <linux/tcp.h>
 13#include <linux/udp.h>
 14#include <uapi/linux/bpf.h>
 15#include <net/ip.h>
 16#include "bpf_helpers.h"
 17
 18#define DEFAULT_PKTGEN_UDP_PORT 9
 19#define DEBUG 0
 20
 21static int tcp(void *data, uint64_t tp_off, void *data_end)
 22{
 23	struct tcphdr *tcp = data + tp_off;
 24
 25	if (tcp + 1 > data_end)
 26		return 0;
 27	if (tcp->dest == htons(80) || tcp->source == htons(80))
 28		return TC_ACT_SHOT;
 29	return 0;
 30}
 31
 32static int udp(void *data, uint64_t tp_off, void *data_end)
 33{
 34	struct udphdr *udp = data + tp_off;
 35
 36	if (udp + 1 > data_end)
 37		return 0;
 38	if (udp->dest == htons(DEFAULT_PKTGEN_UDP_PORT) ||
 39	    udp->source == htons(DEFAULT_PKTGEN_UDP_PORT)) {
 40		if (DEBUG) {
 41			char fmt[] = "udp port 9 indeed\n";
 42
 43			bpf_trace_printk(fmt, sizeof(fmt));
 44		}
 45		return TC_ACT_SHOT;
 46	}
 47	return 0;
 48}
 49
 50static int parse_ipv4(void *data, uint64_t nh_off, void *data_end)
 51{
 52	struct iphdr *iph;
 53	uint64_t ihl_len;
 54
 55	iph = data + nh_off;
 56	if (iph + 1 > data_end)
 57		return 0;
 58
 59	if (ip_is_fragment(iph))
 60		return 0;
 61	ihl_len = iph->ihl * 4;
 62
 63	if (iph->protocol == IPPROTO_IPIP) {
 64		iph = data + nh_off + ihl_len;
 65		if (iph + 1 > data_end)
 66			return 0;
 67		ihl_len += iph->ihl * 4;
 68	}
 69
 70	if (iph->protocol == IPPROTO_TCP)
 71		return tcp(data, nh_off + ihl_len, data_end);
 72	else if (iph->protocol == IPPROTO_UDP)
 73		return udp(data, nh_off + ihl_len, data_end);
 74	return 0;
 75}
 76
 77static int parse_ipv6(void *data, uint64_t nh_off, void *data_end)
 78{
 79	struct ipv6hdr *ip6h;
 80	struct iphdr *iph;
 81	uint64_t ihl_len = sizeof(struct ipv6hdr);
 82	uint64_t nexthdr;
 83
 84	ip6h = data + nh_off;
 85	if (ip6h + 1 > data_end)
 86		return 0;
 87
 88	nexthdr = ip6h->nexthdr;
 89
 90	if (nexthdr == IPPROTO_IPIP) {
 91		iph = data + nh_off + ihl_len;
 92		if (iph + 1 > data_end)
 93			return 0;
 94		ihl_len += iph->ihl * 4;
 95		nexthdr = iph->protocol;
 96	} else if (nexthdr == IPPROTO_IPV6) {
 97		ip6h = data + nh_off + ihl_len;
 98		if (ip6h + 1 > data_end)
 99			return 0;
100		ihl_len += sizeof(struct ipv6hdr);
101		nexthdr = ip6h->nexthdr;
102	}
103
104	if (nexthdr == IPPROTO_TCP)
105		return tcp(data, nh_off + ihl_len, data_end);
106	else if (nexthdr == IPPROTO_UDP)
107		return udp(data, nh_off + ihl_len, data_end);
108	return 0;
109}
110
111struct vlan_hdr {
112	uint16_t h_vlan_TCI;
113	uint16_t h_vlan_encapsulated_proto;
114};
115
116SEC("varlen")
117int handle_ingress(struct __sk_buff *skb)
118{
119	void *data = (void *)(long)skb->data;
120	struct ethhdr *eth = data;
121	void *data_end = (void *)(long)skb->data_end;
122	uint64_t h_proto, nh_off;
123
124	nh_off = sizeof(*eth);
125	if (data + nh_off > data_end)
126		return 0;
127
128	h_proto = eth->h_proto;
129
130	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
131		struct vlan_hdr *vhdr;
132
133		vhdr = data + nh_off;
134		nh_off += sizeof(struct vlan_hdr);
135		if (data + nh_off > data_end)
136			return 0;
137		h_proto = vhdr->h_vlan_encapsulated_proto;
138	}
139	if (h_proto == ETH_P_8021Q || h_proto == ETH_P_8021AD) {
140		struct vlan_hdr *vhdr;
141
142		vhdr = data + nh_off;
143		nh_off += sizeof(struct vlan_hdr);
144		if (data + nh_off > data_end)
145			return 0;
146		h_proto = vhdr->h_vlan_encapsulated_proto;
147	}
148	if (h_proto == htons(ETH_P_IP))
149		return parse_ipv4(data, nh_off, data_end);
150	else if (h_proto == htons(ETH_P_IPV6))
151		return parse_ipv6(data, nh_off, data_end);
152	return 0;
153}
154char _license[] SEC("license") = "GPL";