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