/*
 * kernel/configs.c
 * Echo the kernel .config file used to build the kernel
 *
 * Copyright (C) 2002 Khalid Aziz <khalid_aziz@hp.com>
 * Copyright (C) 2002 Randy Dunlap <rdunlap@xenotime.net>
 * Copyright (C) 2002 Al Stone <ahs3@fc.hp.com>
 * Copyright (C) 2002 Hewlett-Packard Company
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 * NON INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/uaccess.h>

/**************************************************/
/* the actual current config file                 */

/*
 * Define kernel_config_data and kernel_config_data_size, which contains the
 * wrapped and compressed configuration file.  The file is first compressed
 * with gzip and then bounded by two eight byte magic numbers to allow
 * extraction from a binary kernel image:
 *
 *   IKCFG_ST
 *   <image>
 *   IKCFG_ED
 */
#define MAGIC_START	"IKCFG_ST"
#define MAGIC_END	"IKCFG_ED"
#include "config_data.h"


#define MAGIC_SIZE (sizeof(MAGIC_START) - 1)
#define kernel_config_data_size \
	(sizeof(kernel_config_data) - 1 - MAGIC_SIZE * 2)

#ifdef CONFIG_IKCONFIG_PROC

static ssize_t
ikconfig_read_current(struct file *file, char __user *buf,
		      size_t len, loff_t * offset)
{
	return simple_read_from_buffer(buf, len, offset,
				       kernel_config_data + MAGIC_SIZE,
				       kernel_config_data_size);
}

static const struct file_operations ikconfig_file_ops = {
	.owner = THIS_MODULE,
	.read = ikconfig_read_current,
	.llseek = default_llseek,
};

static int __init ikconfig_init(void)
{
	struct proc_dir_entry *entry;

	/* create the current config file */
	entry = proc_create("config.gz", S_IFREG | S_IRUGO, NULL,
			    &ikconfig_file_ops);
	if (!entry)
		return -ENOMEM;

	proc_set_size(entry, kernel_config_data_size);

	return 0;
}

static void __exit ikconfig_cleanup(void)
{
	remove_proc_entry("config.gz", NULL);
}

module_init(ikconfig_init);
module_exit(ikconfig_cleanup);

#endif /* CONFIG_IKCONFIG_PROC */

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Randy Dunlap");
MODULE_DESCRIPTION("Echo the kernel .config file used to build the kernel");
&amp;showmsg=1'>include</a>/<a href='/cgit.cgi/linux/net-next.git/log/include/net?id=1a2a14444d32b89b28116daea86f63ced1716668&amp;showmsg=1'>net</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/cgit.cgi/linux/net-next.git/log/include/net?id=1a2a14444d32b89b28116daea86f63ced1716668'>Collapse</a>)</th><th class='left'>Author</th><th class='left'>Files</th><th class='left'>Lines</th></tr>
<tr class='logheader'><td><span title='2017-01-31 13:16:59 -0500'>2017-01-31</span></td><td class='logsubject'><a href='/cgit.cgi/linux/net-next.git/commit/include/net?id=90427ef5d2a4b9a24079889bf16afdcdaebc4240'>ipv6: fix flow labels when the traffic class is non-0</a></td><td>Dimitris Michailidis</td><td>1</td><td><span class='deletions'>-0</span>/<span class='insertions'>+5</span></td></tr>
<tr class='nohover-highlight'><td/><td colspan='5' class='logmsg'>
ip6_make_flowlabel() determines the flow label for IPv6 packets. It's
supposed to be passed a flow label, which it returns as is if non-0 and
in some other cases, otherwise it calculates a new value.

The problem is callers often pass a flowi6.flowlabel, which may also
contain traffic class bits. If the traffic class is non-0
ip6_make_flowlabel() mistakes the non-0 it gets as a flow label and
returns the whole thing. Thus it can return a 'flow label' longer than
20b and the low 20b of that is typically 0 resulting in packets with 0
label. Moreover, different packets of a flow may be labeled differently.
For a TCP flow with ECN non-payload and payload packets get different
labels as exemplified by this pair of consecutive packets:

(pure ACK)
Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... .... .... 0001 1100 1110 0100 1001 = Flow Label: 0x1ce49
    Payload Length: 32
    Next Header: TCP (6)

(payload)
Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0))
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2)
    .... .... .... 0000 0000 0000 0000 0000 = Flow Label: 0x00000
    Payload Length: 688
    Next Header: TCP (6)

This patch allows ip6_make_flowlabel() to be passed more than just a
flow label and has it extract the part it really wants. This was simpler
than modifying the callers. With this patch packets like the above become

Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0000 .... .... .... .... .... = Traffic Class: 0x00 (DSCP: CS0, ECN: Not-ECT)
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..00 .... .... .... .... .... = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e
    Payload Length: 32
    Next Header: TCP (6)

Internet Protocol Version 6, Src: 2002:af5:11a3::, Dst: 2002:af5:11a2::
    0110 .... = Version: 6
    .... 0000 0010 .... .... .... .... .... = Traffic Class: 0x02 (DSCP: CS0, ECN: ECT(0))
        .... 0000 00.. .... .... .... .... .... = Differentiated Services Codepoint: Default (0)
        .... .... ..10 .... .... .... .... .... = Explicit Congestion Notification: ECN-Capable Transport codepoint '10' (2)
    .... .... .... 1010 1111 1010 0101 1110 = Flow Label: 0xafa5e
    Payload Length: 688
    Next Header: TCP (6)

Signed-off-by: Dimitris Michailidis &lt;dmichail@google.com&gt;
Acked-by: Eric Dumazet &lt;edumazet@google.com&gt;
Signed-off-by: David S. Miller &lt;davem@davemloft.net&gt;


</td></tr>