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 | |
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, len: sizeof(struct udphdr)); |
50 | skb_set_transport_header(skb, offset: 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, len: sizeof(struct ipv6hdr)); |
56 | skb_set_network_header(skb, offset: 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, len: sizeof(struct ethhdr)); |
64 | skb_set_mac_header(skb, offset: 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 | |
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 | |