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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 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 | ||
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"); |