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blackhole_dev: add a selftest

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Since this is not really a device with all capabilities, this test
ensures that it has *enough* to make it through the data path
without causing unwanted side-effects (read crash!).

Signed-off-by: Mahesh Bandewar <maheshb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Mahesh Bandewar
2019-07-01 14:39:01 -07:00
committed by David S. Miller
parent 8d7017fd62
commit 509e56b37c
6 changed files with 123 additions and 1 deletions
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100
lib/test_blackhole_dev.c Normal file
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// 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");