/* -*- linux-c -*-
 * sysctl_net.c: sysctl interface to net subsystem.
 *
 * Begun April 1, 1996, Mike Shaver.
 * Added /proc/sys/net directories for each protocol family. [MS]
 *
 * Revision 1.2  1996/05/08  20:24:40  shaver
 * Added bits for NET_BRIDGE and the NET_IPV4_ARP stuff and
 * NET_IPV4_IP_FORWARD.
 *
 *
 */

#include <linux/mm.h>
#include <linux/export.h>
#include <linux/sysctl.h>
#include <linux/nsproxy.h>

#include <net/sock.h>

#ifdef CONFIG_INET
#include <net/ip.h>
#endif

#ifdef CONFIG_NET
#include <linux/if_ether.h>
#endif

static struct ctl_table_set *
net_ctl_header_lookup(struct ctl_table_root *root)
{
	return &current->nsproxy->net_ns->sysctls;
}

static int is_seen(struct ctl_table_set *set)
{
	return &current->nsproxy->net_ns->sysctls == set;
}

/* Return standard mode bits for table entry. */
static int net_ctl_permissions(struct ctl_table_header *head,
			       struct ctl_table *table)
{
	struct net *net = container_of(head->set, struct net, sysctls);

	/* Allow network administrator to have same access as root. */
	if (ns_capable_noaudit(net->user_ns, CAP_NET_ADMIN)) {
		int mode = (table->mode >> 6) & 7;
		return (mode << 6) | (mode << 3) | mode;
	}

	return table->mode;
}

static void net_ctl_set_ownership(struct ctl_table_header *head,
				  struct ctl_table *table,
				  kuid_t *uid, kgid_t *gid)
{
	struct net *net = container_of(head->set, struct net, sysctls);
	kuid_t ns_root_uid;
	kgid_t ns_root_gid;

	ns_root_uid = make_kuid(net->user_ns, 0);
	if (uid_valid(ns_root_uid))
		*uid = ns_root_uid;

	ns_root_gid = make_kgid(net->user_ns, 0);
	if (gid_valid(ns_root_gid))
		*gid = ns_root_gid;
}

static struct ctl_table_root net_sysctl_root = {
	.lookup = net_ctl_header_lookup,
	.permissions = net_ctl_permissions,
	.set_ownership = net_ctl_set_ownership,
};

static int __net_init sysctl_net_init(struct net *net)
{
	setup_sysctl_set(&net->sysctls, &net_sysctl_root, is_seen);
	return 0;
}

static void __net_exit sysctl_net_exit(struct net *net)
{
	retire_sysctl_set(&net->sysctls);
}

static struct pernet_operations sysctl_pernet_ops = {
	.init = sysctl_net_init,
	.exit = sysctl_net_exit,
};

static struct ctl_table_header *net_header;
__init int net_sysctl_init(void)
{
	static struct ctl_table empty[1];
	int ret = -ENOMEM;
	/* Avoid limitations in the sysctl implementation by
	 * registering "/proc/sys/net" as an empty directory not in a
	 * network namespace.
	 */
	net_header = register_sysctl("net", empty);
	if (!net_header)
		goto out;
	ret = register_pernet_subsys(&sysctl_pernet_ops);
	if (ret)
		goto out1;
	register_sysctl_root(&net_sysctl_root);
out:
	return ret;
out1:
	unregister_sysctl_table(net_header);
	net_header = NULL;
	goto out;
}

struct ctl_table_header *register_net_sysctl(struct net *net,
	const char *path, struct ctl_table *table)
{
	return __register_sysctl_table(&net->sysctls, path, table);
}
EXPORT_SYMBOL_GPL(register_net_sysctl);

void unregister_net_sysctl_table(struct ctl_table_header *header)
{
	unregister_sysctl_table(header);
}
EXPORT_SYMBOL_GPL(unregister_net_sysctl_table);
it.cgi/linux/net-next.git/log/include/net/ipv6.h?id=beb1afac518dec5a15dc92ba8f0ca016dcf457b4&amp;showmsg=1'>ipv6.h</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/ipv6.h?id=beb1afac518dec5a15dc92ba8f0ca016dcf457b4'>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/ipv6.h?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>