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: Erik Kline <ek@google.com>
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 54410a1d4065b19f5b9aeca8edcb08bf53914632..d8676dda7fa69be9dd1e2e37fe5f12e6c6699e2a 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -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.

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ea04ca024f0d2ad21fa3840b4baf4a397517b421..cb18c6290ca87290996e636f3eda14eb03d26316 100644 (file)
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -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;
 };

diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index b22a9c4e1b1248d73938fb271e83b516292130a1..9c0f4a92bcffb5a86f9f1fed0e177ce4974ab27f 100644 (file)
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -186,6 +186,7 @@ enum {
        DEVCONF_ADDR_GEN_MODE,
        DEVCONF_DISABLE_POLICY,
        DEVCONF_ACCEPT_RA_RT_INFO_MIN_PLEN,
+       DEVCONF_NDISC_TCLASS,
        DEVCONF_MAX
 };
 

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 6233e06fa35cf2030ac7d7575b9a51f336f2bea4..a6dffd65eb9db8d0832acdb8463c1497564c6340 100644 (file)
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -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 */
        }

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index f9c3ffe04382977773628a5b7e8111f437c3ae92..b3cea200c85e232829b8b64f38e000ef896462b8 100644 (file)
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -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;