// SPDX-License-Identifier: GPL-2.0/* * This module tests the blackhole_dev that is created during the * net subsystem initialization. The test this module performs is * by injecting an skb into the stack with skb->dev as the * blackhole_dev and expects kernel to behave in a sane manner * (in other words, *not crash*)! * * Copyright (c) 2018, Mahesh Bandewar <maheshb@google.com> */ #include <linux/init.h>#include <linux/module.h>#include <linux/printk.h>#include <linux/skbuff.h>#include <linux/netdevice.h>#include <linux/udp.h>#include <linux/ipv6.h> #include <net/dst.h> #define SKB_SIZE  256#define HEAD_SIZE (14+40+8)	/* Ether + IPv6 + UDP */#define TAIL_SIZE 32		/* random tail-room */ #define UDP_PORT 1234 static int __init test_blackholedev_init(void){	struct ipv6hdr *ip6h;	struct sk_buff *skb;	struct ethhdr *ethh;	struct udphdr *uh;	int data_len;	int ret; 	skb = alloc_skb(SKB_SIZE, GFP_KERNEL);	if (!skb)		return -ENOMEM; 	/* Reserve head-room for the headers */	skb_reserve(skb, HEAD_SIZE); 	/* Add data to the skb */	data_len = SKB_SIZE - (HEAD_SIZE + TAIL_SIZE);	memset(__skb_put(skb, data_len), 0xf, data_len); 	/* Add protocol data */	/* (Transport) UDP */	uh = (struct udphdr *)skb_push(skb, sizeof(struct udphdr));	skb_set_transport_header(skb, 0);	uh->source = uh->dest = htons(UDP_PORT);	uh->len = htons(data_len);	uh->check = 0;	/* (Network) IPv6 */	ip6h = (struct ipv6hdr *)skb_push(skb, sizeof(struct ipv6hdr));	skb_set_network_header(skb, 0);	ip6h->hop_limit = 32;	ip6h->payload_len = data_len + sizeof(struct udphdr);	ip6h->nexthdr = IPPROTO_UDP;	ip6h->saddr = in6addr_loopback;	ip6h->daddr = in6addr_loopback;	/* Ether */	ethh = (struct ethhdr *)skb_push(skb, sizeof(struct ethhdr));	skb_set_mac_header(skb, 0); 	skb->protocol = htons(ETH_P_IPV6);	skb->pkt_type = PACKET_HOST;	skb->dev = blackhole_netdev; 	/* Now attempt to send the packet */	ret = dev_queue_xmit(skb); 	switch (ret) {	case NET_XMIT_SUCCESS:		pr_warn("dev_queue_xmit() returned NET_XMIT_SUCCESS\n");		break;	case NET_XMIT_DROP:		pr_warn("dev_queue_xmit() returned NET_XMIT_DROP\n");		break;	case NET_XMIT_CN:		pr_warn("dev_queue_xmit() returned NET_XMIT_CN\n");		break;	default:		pr_err("dev_queue_xmit() returned UNKNOWN(%d)\n", ret);	} 	return 0;} static void __exit test_blackholedev_exit(void){	pr_warn("test_blackholedev module terminating.\n");} module_init(test_blackholedev_init);module_exit(test_blackholedev_exit); MODULE_AUTHOR("Mahesh Bandewar <maheshb@google.com>");MODULE_LICENSE("GPL");