1*4882a593Smuzhiyun // SPDX-License-Identifier: GPL-2.0
2*4882a593Smuzhiyun /*
3*4882a593Smuzhiyun * This module tests the blackhole_dev that is created during the
4*4882a593Smuzhiyun * net subsystem initialization. The test this module performs is
5*4882a593Smuzhiyun * by injecting an skb into the stack with skb->dev as the
6*4882a593Smuzhiyun * blackhole_dev and expects kernel to behave in a sane manner
7*4882a593Smuzhiyun * (in other words, *not crash*)!
8*4882a593Smuzhiyun *
9*4882a593Smuzhiyun * Copyright (c) 2018, Mahesh Bandewar <maheshb@google.com>
10*4882a593Smuzhiyun */
11*4882a593Smuzhiyun
12*4882a593Smuzhiyun #include <linux/init.h>
13*4882a593Smuzhiyun #include <linux/module.h>
14*4882a593Smuzhiyun #include <linux/printk.h>
15*4882a593Smuzhiyun #include <linux/skbuff.h>
16*4882a593Smuzhiyun #include <linux/netdevice.h>
17*4882a593Smuzhiyun #include <linux/udp.h>
18*4882a593Smuzhiyun #include <linux/ipv6.h>
19*4882a593Smuzhiyun
20*4882a593Smuzhiyun #include <net/dst.h>
21*4882a593Smuzhiyun
22*4882a593Smuzhiyun #define SKB_SIZE 256
23*4882a593Smuzhiyun #define HEAD_SIZE (14+40+8) /* Ether + IPv6 + UDP */
24*4882a593Smuzhiyun #define TAIL_SIZE 32 /* random tail-room */
25*4882a593Smuzhiyun
26*4882a593Smuzhiyun #define UDP_PORT 1234
27*4882a593Smuzhiyun
test_blackholedev_init(void)28*4882a593Smuzhiyun static int __init test_blackholedev_init(void)
29*4882a593Smuzhiyun {
30*4882a593Smuzhiyun struct ipv6hdr *ip6h;
31*4882a593Smuzhiyun struct sk_buff *skb;
32*4882a593Smuzhiyun struct ethhdr *ethh;
33*4882a593Smuzhiyun struct udphdr *uh;
34*4882a593Smuzhiyun int data_len;
35*4882a593Smuzhiyun int ret;
36*4882a593Smuzhiyun
37*4882a593Smuzhiyun skb = alloc_skb(SKB_SIZE, GFP_KERNEL);
38*4882a593Smuzhiyun if (!skb)
39*4882a593Smuzhiyun return -ENOMEM;
40*4882a593Smuzhiyun
41*4882a593Smuzhiyun /* Reserve head-room for the headers */
42*4882a593Smuzhiyun skb_reserve(skb, HEAD_SIZE);
43*4882a593Smuzhiyun
44*4882a593Smuzhiyun /* Add data to the skb */
45*4882a593Smuzhiyun data_len = SKB_SIZE - (HEAD_SIZE + TAIL_SIZE);
46*4882a593Smuzhiyun memset(__skb_put(skb, data_len), 0xf, data_len);
47*4882a593Smuzhiyun
48*4882a593Smuzhiyun /* Add protocol data */
49*4882a593Smuzhiyun /* (Transport) UDP */
50*4882a593Smuzhiyun uh = (struct udphdr *)skb_push(skb, sizeof(struct udphdr));
51*4882a593Smuzhiyun skb_set_transport_header(skb, 0);
52*4882a593Smuzhiyun uh->source = uh->dest = htons(UDP_PORT);
53*4882a593Smuzhiyun uh->len = htons(data_len);
54*4882a593Smuzhiyun uh->check = 0;
55*4882a593Smuzhiyun /* (Network) IPv6 */
56*4882a593Smuzhiyun ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));
57*4882a593Smuzhiyun skb_set_network_header(skb, 0);
58*4882a593Smuzhiyun ip6h->hop_limit = 32;
59*4882a593Smuzhiyun ip6h->payload_len = data_len + sizeof(struct udphdr);
60*4882a593Smuzhiyun ip6h->nexthdr = IPPROTO_UDP;
61*4882a593Smuzhiyun ip6h->saddr = in6addr_loopback;
62*4882a593Smuzhiyun ip6h->daddr = in6addr_loopback;
63*4882a593Smuzhiyun /* Ether */
64*4882a593Smuzhiyun ethh = (struct ethhdr *)skb_push(skb, sizeof(struct ethhdr));
65*4882a593Smuzhiyun skb_set_mac_header(skb, 0);
66*4882a593Smuzhiyun
67*4882a593Smuzhiyun skb->protocol = htons(ETH_P_IPV6);
68*4882a593Smuzhiyun skb->pkt_type = PACKET_HOST;
69*4882a593Smuzhiyun skb->dev = blackhole_netdev;
70*4882a593Smuzhiyun
71*4882a593Smuzhiyun /* Now attempt to send the packet */
72*4882a593Smuzhiyun ret = dev_queue_xmit(skb);
73*4882a593Smuzhiyun
74*4882a593Smuzhiyun switch (ret) {
75*4882a593Smuzhiyun case NET_XMIT_SUCCESS:
76*4882a593Smuzhiyun pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");
77*4882a593Smuzhiyun break;
78*4882a593Smuzhiyun case NET_XMIT_DROP:
79*4882a593Smuzhiyun pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");
80*4882a593Smuzhiyun break;
81*4882a593Smuzhiyun case NET_XMIT_CN:
82*4882a593Smuzhiyun pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");
83*4882a593Smuzhiyun break;
84*4882a593Smuzhiyun default:
85*4882a593Smuzhiyun pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);
86*4882a593Smuzhiyun }
87*4882a593Smuzhiyun
88*4882a593Smuzhiyun return 0;
89*4882a593Smuzhiyun }
90*4882a593Smuzhiyun
test_blackholedev_exit(void)91*4882a593Smuzhiyun static void __exit test_blackholedev_exit(void)
92*4882a593Smuzhiyun {
93*4882a593Smuzhiyun pr_warn("test_blackholedev module terminating.\n");
94*4882a593Smuzhiyun }
95*4882a593Smuzhiyun
96*4882a593Smuzhiyun module_init(test_blackholedev_init);
97*4882a593Smuzhiyun module_exit(test_blackholedev_exit);
98*4882a593Smuzhiyun
99*4882a593Smuzhiyun MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
100*4882a593Smuzhiyun MODULE_LICENSE("GPL");
101