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Commit 2210d6b2 authored by Maciej Żenczykowski's avatar Maciej Żenczykowski Committed by David S. Miller
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net: ipv6: sysctl to specify IPv6 ND traffic class 

Add a per-device sysctl to specify the default traffic class to use for
kernel originated IPv6 Neighbour Discovery packets.

Currently this includes:

  - Router Solicitation (ICMPv6 type 133)
    ndisc_send_rs() -> ndisc_send_skb() -> ip6_nd_hdr()

  - Neighbour Solicitation (ICMPv6 type 135)
    ndisc_send_ns() -> ndisc_send_skb() -> ip6_nd_hdr()

  - Neighbour Advertisement (ICMPv6 type 136)
    ndisc_send_na() -> ndisc_send_skb() -> ip6_nd_hdr()

  - Redirect (ICMPv6 type 137)
    ndisc_send_redirect() -> ndisc_send_skb() -> ip6_nd_hdr()

and if the kernel ever gets around to generating RA's,
it would presumably also include:

  - Router Advertisement (ICMPv6 type 134)
    (radvd daemon could pick up on the kernel setting and use it)

Interface drivers may examine the Traffic Class value and translate
the DiffServ Code Point into a link-layer appropriate traffic
prioritization scheme.  An example of mapping IETF DSCP values to
IEEE 802.11 User Priority values can be found here:

    https://tools.ietf.org/html/draft-ietf-tsvwg-ieee-802-11



The expected primary use case is to properly prioritize ND over wifi.

Testing:
  jzem22:~# cat /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  0
  jzem22:~# echo -1 > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  -bash: echo: write error: Invalid argument
  jzem22:~# echo 256 > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  -bash: echo: write error: Invalid argument
  jzem22:~# echo 0 > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  jzem22:~# echo 255 > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  jzem22:~# cat /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  255
  jzem22:~# echo 34 > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  jzem22:~# cat /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  34

  jzem22:~# echo $[0xDC] > /proc/sys/net/ipv6/conf/eth0/ndisc_tclass
  jzem22:~# tcpdump -v -i eth0 icmp6 and src host jzem22.pgc and dst host fe80::1
  tcpdump: listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes
  IP6 (class 0xdc, hlim 255, next-header ICMPv6 (58) payload length: 24)
  jzem22.pgc > fe80::1: [icmp6 sum ok] ICMP6, neighbor advertisement,
  length 24, tgt is jzem22.pgc, Flags [solicited]

(based on original change written by Erik Kline, with minor changes)

v2: fix 'suspicious rcu_dereference_check() usage'
    by explicitly grabbing the rcu_read_lock.

Cc: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: default avatarErik Kline <ek@google.com>
Signed-off-by: default avatarMaciej Żenczykowski <maze@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 04bad8bd

Documentation/networking/ip-sysctl.txt

+9 −0
Original line number Diff line number Diff line
@@ -1732,6 +1732,15 @@ ndisc_notify - BOOLEAN 
	1 - Generate unsolicited neighbour advertisements when device is brought

	    up or hardware address changes.



ndisc_tclass - INTEGER

	The IPv6 Traffic Class to use by default when sending IPv6 Neighbor

	Discovery (Router Solicitation, Router Advertisement, Neighbor

	Solicitation, Neighbor Advertisement, Redirect) messages.

	These 8 bits can be interpreted as 6 high order bits holding the DSCP

	value and 2 low order bits representing ECN (which you probably want

	to leave cleared).

	0 - (default)



mldv1_unsolicited_report_interval - INTEGER

	The interval in milliseconds in which the next unsolicited

	MLDv1 report retransmit will take place.

include/linux/ipv6.h

+1 −0
Original line number Diff line number Diff line
@@ -73,6 +73,7 @@ struct ipv6_devconf { 
	__u32		enhanced_dad;

	__u32		addr_gen_mode;

	__s32		disable_policy;

	__s32           ndisc_tclass;



	struct ctl_table_header *sysctl_header;

};

include/uapi/linux/ipv6.h

+1 −0
Original line number Diff line number Diff line
@@ -186,6 +186,7 @@ enum { 
	DEVCONF_ADDR_GEN_MODE,

	DEVCONF_DISABLE_POLICY,

	DEVCONF_ACCEPT_RA_RT_INFO_MIN_PLEN,

	DEVCONF_NDISC_TCLASS,

	DEVCONF_MAX

};

net/ipv6/addrconf.c

+11 −0
Original line number Diff line number Diff line
@@ -5059,6 +5059,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf, 
	array[DEVCONF_ENHANCED_DAD] = cnf->enhanced_dad;

	array[DEVCONF_ADDR_GEN_MODE] = cnf->addr_gen_mode;

	array[DEVCONF_DISABLE_POLICY] = cnf->disable_policy;

	array[DEVCONF_NDISC_TCLASS] = cnf->ndisc_tclass;

}



static inline size_t inet6_ifla6_size(void)
@@ -5986,6 +5987,7 @@ int addrconf_sysctl_disable_policy(struct ctl_table *ctl, int write, 
}



static int minus_one = -1;

static const int zero = 0;

static const int one = 1;

static const int two_five_five = 255;
@@ -6356,6 +6358,15 @@ static const struct ctl_table addrconf_sysctl[] = { 
		.mode           = 0644,

		.proc_handler   = addrconf_sysctl_disable_policy,

	},

	{

		.procname	= "ndisc_tclass",

		.data		= &ipv6_devconf.ndisc_tclass,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec_minmax,

		.extra1		= (void *)&zero,

		.extra2		= (void *)&two_five_five,

	},

	{

		/* sentinel */

	}

net/ipv6/ndisc.c

+8 −1
Original line number Diff line number Diff line
@@ -427,12 +427,19 @@ static void ip6_nd_hdr(struct sk_buff *skb, 
		       int hop_limit, int len)

{

	struct ipv6hdr *hdr;

	struct inet6_dev *idev;

	unsigned tclass;



	rcu_read_lock();

	idev = __in6_dev_get(skb->dev);

	tclass = idev ? idev->cnf.ndisc_tclass : 0;

	rcu_read_unlock();



	skb_push(skb, sizeof(*hdr));

	skb_reset_network_header(skb);

	hdr = ipv6_hdr(skb);



	ip6_flow_hdr(hdr, 0, 0);

	ip6_flow_hdr(hdr, tclass, 0);



	hdr->payload_len = htons(len);

	hdr->nexthdr = IPPROTO_ICMPV6;