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 ethhdr *ethh;
33 struct udphdr *uh;
34 int data_len;
35 int ret;
36
37 skb = alloc_skb(SKB_SIZE, GFP_KERNEL);
38 if (!skb)
39 return -ENOMEM;
40
41 /* Reserve head-room for the headers */
42 skb_reserve(skb, HEAD_SIZE);
43
44 /* Add data to the skb */
45 data_len = SKB_SIZE - (HEAD_SIZE + TAIL_SIZE);
46 memset(__skb_put(skb, data_len), 0xf, data_len);
47
48 /* Add protocol data */
49 /* (Transport) UDP */
50 uh = (struct udphdr *)skb_push(skb, sizeof(struct udphdr));
51 skb_set_transport_header(skb, 0);
52 uh->source = uh->dest = htons(UDP_PORT);
53 uh->len = htons(data_len);
54 uh->check = 0;
55 /* (Network) IPv6 */
56 ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));
57 skb_set_network_header(skb, 0);
58 ip6h->hop_limit = 32;
59 ip6h->payload_len = data_len + sizeof(struct udphdr);
60 ip6h->nexthdr = IPPROTO_UDP;
61 ip6h->saddr = in6addr_loopback;
62 ip6h->daddr = in6addr_loopback;
63 /* Ether */
64 ethh = (struct ethhdr *)skb_push(skb, sizeof(struct ethhdr));
65 skb_set_mac_header(skb, 0);
66
67 skb->protocol = htons(ETH_P_IPV6);
68 skb->pkt_type = PACKET_HOST;
69 skb->dev = blackhole_netdev;
70
71 /* Now attempt to send the packet */
72 ret = dev_queue_xmit(skb);
73
74 switch (ret) {
75 case NET_XMIT_SUCCESS:
76 pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");
77 break;
78 case NET_XMIT_DROP:
79 pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");
80 break;
81 case NET_XMIT_CN:
82 pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");
83 break;
84 default:
85 pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);
86 }
87
88 return 0;
89 }
90
test_blackholedev_exit(void)91 static void __exit test_blackholedev_exit(void)
92 {
93 pr_warn("test_blackholedev module terminating.\n");
94 }
95
96 module_init(test_blackholedev_init);
97 module_exit(test_blackholedev_exit);
98
99 MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
100 MODULE_LICENSE("GPL");
101