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
 28static 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
 90static void __exit test_blackholedev_exit(void)
 91{
 92	pr_warn("test_blackholedev module terminating.\n");
 93}
 94
 95module_init(test_blackholedev_init);
 96module_exit(test_blackholedev_exit);
 97
 98MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
 99MODULE_DESCRIPTION("module test of the blackhole_dev");
100MODULE_LICENSE("GPL");