lib/test_blackhole_dev.c

   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, 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
  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");