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_DESCRIPTION("module test of the blackhole_dev");
100 MODULE_LICENSE("GPL");
101