test_blackhole_dev.c 2.5 KB

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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. #include <linux/init.h>
  12. #include <linux/module.h>
  13. #include <linux/printk.h>
  14. #include <linux/skbuff.h>
  15. #include <linux/netdevice.h>
  16. #include <linux/udp.h>
  17. #include <linux/ipv6.h>
  18. #include <net/dst.h>
  19. #define SKB_SIZE 256
  20. #define HEAD_SIZE (14+40+8) /* Ether + IPv6 + UDP */
  21. #define TAIL_SIZE 32 /* random tail-room */
  22. #define UDP_PORT 1234
  23. static int __init test_blackholedev_init(void)
  24. {
  25. struct ipv6hdr *ip6h;
  26. struct sk_buff *skb;
  27. struct ethhdr *ethh;
  28. struct udphdr *uh;
  29. int data_len;
  30. int ret;
  31. skb = alloc_skb(SKB_SIZE, GFP_KERNEL);
  32. if (!skb)
  33. return -ENOMEM;
  34. /* Reserve head-room for the headers */
  35. skb_reserve(skb, HEAD_SIZE);
  36. /* Add data to the skb */
  37. data_len = SKB_SIZE - (HEAD_SIZE + TAIL_SIZE);
  38. memset(__skb_put(skb, data_len), 0xf, data_len);
  39. /* Add protocol data */
  40. /* (Transport) UDP */
  41. uh = (struct udphdr *)skb_push(skb, sizeof(struct udphdr));
  42. skb_set_transport_header(skb, 0);
  43. uh->source = uh->dest = htons(UDP_PORT);
  44. uh->len = htons(data_len);
  45. uh->check = 0;
  46. /* (Network) IPv6 */
  47. ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));
  48. skb_set_network_header(skb, 0);
  49. ip6h->hop_limit = 32;
  50. ip6h->payload_len = data_len + sizeof(struct udphdr);
  51. ip6h->nexthdr = IPPROTO_UDP;
  52. ip6h->saddr = in6addr_loopback;
  53. ip6h->daddr = in6addr_loopback;
  54. /* Ether */
  55. ethh = (struct ethhdr *)skb_push(skb, sizeof(struct ethhdr));
  56. skb_set_mac_header(skb, 0);
  57. skb->protocol = htons(ETH_P_IPV6);
  58. skb->pkt_type = PACKET_HOST;
  59. skb->dev = blackhole_netdev;
  60. /* Now attempt to send the packet */
  61. ret = dev_queue_xmit(skb);
  62. switch (ret) {
  63. case NET_XMIT_SUCCESS:
  64. pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");
  65. break;
  66. case NET_XMIT_DROP:
  67. pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");
  68. break;
  69. case NET_XMIT_CN:
  70. pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");
  71. break;
  72. default:
  73. pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);
  74. }
  75. return 0;
  76. }
  77. static void __exit test_blackholedev_exit(void)
  78. {
  79. pr_warn("test_blackholedev module terminating.\n");
  80. }
  81. module_init(test_blackholedev_init);
  82. module_exit(test_blackholedev_exit);
  83. MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");
  84. MODULE_LICENSE("GPL");