1// SPDX-License-Identifier: GPL-2.0
2/*
3 * This module tests the blackhole_dev that is created during the
4 * net subsystem initialization. The test this module performs is
5 * by injecting an skb into the stack with skb->dev as the
6 * blackhole_dev and expects kernel to behave in a sane manner
7 * (in other words, *not crash*)!
8 *
9 * Copyright (c) 2018, Mahesh Bandewar <maheshb@google.com>
10 */
11
12#include <linux/init.h>
13#include <linux/module.h>
14#include <linux/printk.h>
15#include <linux/skbuff.h>
16#include <linux/netdevice.h>
17#include <linux/udp.h>
18#include <linux/ipv6.h>
19
20#include <net/dst.h>
21
22#define SKB_SIZE  256
23#define HEAD_SIZE (14+40+8)	/* Ether + IPv6 + UDP */
24#define TAIL_SIZE 32		/* random tail-room */
25
26#define UDP_PORT 1234
27
28static int __init test_blackholedev_init(void)
29{
30	struct ipv6hdr *ip6h;
31	struct sk_buff *skb;
32	struct udphdr *uh;
33	int data_len;
34	int ret;
35
36	skb = alloc_skb(SKB_SIZE, GFP_KERNEL);
37	if (!skb)
38		return -ENOMEM;
39
40	/* Reserve head-room for the headers */
41	skb_reserve(skb, HEAD_SIZE);
42
43	/* Add data to the skb */
44	data_len = SKB_SIZE - (HEAD_SIZE + TAIL_SIZE);
45	memset(__skb_put(skb, data_len), 0xf, data_len);
46
47	/* Add protocol data */
48	/* (Transport) UDP */
49	uh = (struct udphdr *)skb_push(skb, sizeof(struct udphdr));
50	skb_set_transport_header(skb, 0);
51	uh->source = uh->dest = htons(UDP_PORT);
52	uh->len = htons(data_len);
53	uh->check = 0;
54	/* (Network) IPv6 */
55	ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));
56	skb_set_network_header(skb, 0);
57	ip6h->hop_limit = 32;
58	ip6h->payload_len = data_len + sizeof(struct udphdr);
59	ip6h->nexthdr = IPPROTO_UDP;
60	ip6h->saddr = in6addr_loopback;
61	ip6h->daddr = in6addr_loopback;
62	/* Ether */
63	skb_push(skb, sizeof(struct ethhdr));
64	skb_set_mac_header(skb, 0);
65
66	skb->protocol = htons(ETH_P_IPV6);
67	skb->pkt_type = PACKET_HOST;
68	skb->dev = blackhole_netdev;
69
70	/* Now attempt to send the packet */
71	ret = dev_queue_xmit(skb);
72
73	switch (ret) {
74	case NET_XMIT_SUCCESS:
75		pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");
76		break;
77	case NET_XMIT_DROP:
78		pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");
79		break;
80	case NET_XMIT_CN:
81		pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");
82		break;
83	default:
84		pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);
85	}
86
87	return 0;
88}
89
90static void __exit test_blackholedev_exit(void)
91{
92	pr_warn("test_blackholedev module terminating.\n");
93}
94
95module_init(test_blackholedev_init);
96module_exit(test_blackholedev_exit);
97
98MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
99MODULE_LICENSE("GPL");
100