xref: /openbmc/linux/lib/test_blackhole_dev.c (revision f91adad0)
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 
test_blackholedev_init(void)28 static 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 
test_blackholedev_exit(void)90 static void __exit test_blackholedev_exit(void)
91 {
92 	pr_warn("test_blackholedev module terminating.\n");
93 }
94 
95 module_init(test_blackholedev_init);
96 module_exit(test_blackholedev_exit);
97 
98 MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
99 MODULE_LICENSE("GPL");
100