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1// SPDX-License-Identifier: GPL-2.02/*3 * This module tests the blackhole_dev that is created during the4 * net subsystem initialization. The test this module performs is5 * by injecting an skb into the stack with skb->dev as the6 * blackhole_dev and expects kernel to behave in a sane manner7 * (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 25623#define HEAD_SIZE (14+40+8) /* Ether + IPv6 + UDP */24#define TAIL_SIZE 32 /* random tail-room */25 26#define UDP_PORT 123427 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");101