[PATCH] ipv6: add knob to send unsolicited ND on link-layer address change

[PATCH] ipv6: add knob to send unsolicited ND on link-layer address change

[Hannes Frederic Sowa]

This patch introduces a new knob ndisc_notify. If enabled, the kernel
will transmit an unsolicited neighbour advertisement on link-layer address
change to update the neighbour tables of the corresponding hosts more quickly.

This is the equivalent to arp_notify in ipv4 world.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
---
 include/linux/ipv6.h      | 1 +
 include/uapi/linux/ipv6.h | 1 +
 net/ipv6/addrconf.c       | 9 +++++++++
 net/ipv6/ndisc.c          | 7 +++++++
 4 files changed, 18 insertions(+)

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index bcba48a..5e11905 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -47,6 +47,7 @@ struct ipv6_devconf {
 	__s32		disable_ipv6;
 	__s32		accept_dad;
 	__s32		force_tllao;
+	__s32           ndisc_notify;
 	void		*sysctl;
 };
 
diff --git a/include/uapi/linux/ipv6.h b/include/uapi/linux/ipv6.h
index a6d7d1c..5a2991c 100644
--- a/include/uapi/linux/ipv6.h
+++ b/include/uapi/linux/ipv6.h
@@ -157,6 +157,7 @@ enum {
 	DEVCONF_DISABLE_IPV6,
 	DEVCONF_ACCEPT_DAD,
 	DEVCONF_FORCE_TLLAO,
+	DEVCONF_NDISC_NOTIFY,
 	DEVCONF_MAX
 };
 
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 0424e4e..e3df4fa 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3892,6 +3892,7 @@ static inline void ipv6_store_devconf(struct ipv6_devconf *cnf,
 	array[DEVCONF_DISABLE_IPV6] = cnf->disable_ipv6;
 	array[DEVCONF_ACCEPT_DAD] = cnf->accept_dad;
 	array[DEVCONF_FORCE_TLLAO] = cnf->force_tllao;
+	array[DEVCONF_NDISC_NOTIFY] = cnf->ndisc_notify;
 }
 
 static inline size_t inet6_ifla6_size(void)
@@ -4560,6 +4561,14 @@ static struct addrconf_sysctl_table
 			.proc_handler   = proc_dointvec
 		},
 		{
+			.procname       = "ndisc_notify",
+			.data           = &ipv6_devconf.ndisc_notify,
+			.maxlen         = sizeof(int),
+			.mode           = 0644,
+			.proc_handler   = proc_dointvec
+			
+		},
+		{
 			/* sentinel */
 		}
 	},
diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index ff36194..66d5401 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1575,11 +1575,18 @@ static int ndisc_netdev_event(struct notifier_block *this, unsigned long event,
 {
 	struct net_device *dev = ptr;
 	struct net *net = dev_net(dev);
+	struct inet6_dev *idev;
 
 	switch (event) {
 	case NETDEV_CHANGEADDR:
 		neigh_changeaddr(&nd_tbl, dev);
 		fib6_run_gc(~0UL, net);
+		idev = in6_dev_get(dev);
+		if (!idev)
+			break;
+		if (idev->cnf.ndisc_notify)
+			ndisc_send_unsol_na(dev);
+		in6_dev_put(idev);
 		break;
 	case NETDEV_DOWN:
 		neigh_ifdown(&nd_tbl, dev);

Re: [PATCH] ipv6: add knob to send unsolicited ND on link-layer address change

[Hannes Frederic Sowa]

On Wed, Nov 07, 2012 at 03:46:20AM +0100, Hannes Frederic Sowa wrote:
> This patch introduces a new knob ndisc_notify. If enabled, the kernel
> will transmit an unsolicited neighbour advertisement on link-layer address
> change to update the neighbour tables of the corresponding hosts more quickly.
> 
> This is the equivalent to arp_notify in ipv4 world.

If this eases review, I have a test script to demonstrate the behaviour
(this needs the patch to change the mac address of a running veth, which was
merged into net-next some time ago and does only work correctly if unsolicited
neighbour advertisments are send to all-nodes):

#!/bin/bash
set -ex
set -o pipefail
declare -r NETNS=2337 R=$RANDOM
declare -r ULAM="fd8b:abf9:283d:1::/64" ULAM_ADDR="fd8b:abf9:283d:1::1/64"
declare -r ULAS="fd8b:abf9:283d:2::/64" ULAS_ADDR="fd8b:abf9:283d:2::1/64"
declare -r NS="ip netns exec $NETNS"
declare -r NMACM=00:00:6c:55:56:9e NMACS=00:00:6c:55:56:9e
function enable_forward {
    declare -r F="sysctl -w net.ipv6.conf.all.forwarding=1"
    $F
    $NS $F
}
function fetch_gw {
    echo "ip -6 -o a l group $NETNS dev $1 scope link 
	                     | awk '{print \$4}'"
}
case $1 in
    clean)
	ip netns delete $NETNS || true # ignore errors
	# seems to be racy here because deconstruction happens in a workqueue
	sleep 1
	for i in $(ip -o l l group $NETNS|cut -f2 -d:|egrep 'vmeth|dummy'); do
	    ip l d $i || true
	done
	;;
    '')
	declare -r vmeth=vmeth$R vseth=vseth$R
	echo 'file net/ipv6/ndisc.c +pflmt' > /sys/kernel/debug/dynamic_debug/control
	ip netns add $NETNS
	enable_forward
	ip link add name $vmeth type veth peer name $vseth
	ip link set dev $vmeth group $NETNS up
	ip link set dev $vseth netns $NETNS
	$NS ip link set dev $vseth group $NETNS up
	$NS ip l a name dummy$R up type dummy
	$NS ip l set dev dummy$R group $NETNS up
	ip a a $ULAM_ADDR dev $vmeth
	$NS ip a a $ULAS_ADDR dev dummy$R
	declare -r GWS=$(eval $NS $(fetch_gw $vseth))
	declare -r GWM=$(eval $(fetch_gw $vmeth))
	ip -6 r a $ULAS via ${GWS%/64} dev $vmeth
	$NS ip -6 r a $ULAM via ${GWM%/64} dev $vseth
	sleep 5
	time ping6 -w 100 -c 1 ${ULAS_ADDR%/64}
	# perf probes
	$0 internal $vmeth
	;;
    internal)
	sleep 5
	ip l set dev $2 addr $NMACM
	sleep 5
	time ping6 -w 100 -c 1 ${ULAS_ADDR%/64}
	;;
esac

David, if you intend to merge this patch, could you please remove the empty
line I accidently added in the addrconf_sysctl_table, directly following
.proc_handler? As usual, I noticed it just after sending the patch.

Re: [PATCH] ipv6: add knob to send unsolicited ND on link-layer address change

[David Miller]

From: Hannes Frederic Sowa <hannes@stressinduktion.org>
Date: Fri, 9 Nov 2012 14:01:41 +0100

> David, if you intend to merge this patch, could you please remove the empty
> line I accidently added in the addrconf_sysctl_table, directly following
> .proc_handler? As usual, I noticed it just after sending the patch.

I intend to eventually apply this to net-next, and I'll take care
of the empty line when I do so, thanks.

Re: [PATCH] ipv6: add knob to send unsolicited ND on link-layer address change

[David Miller]

From: Hannes Frederic Sowa <hannes@stressinduktion.org>
Date: Wed, 7 Nov 2012 03:46:20 +0100

> This patch introduces a new knob ndisc_notify. If enabled, the kernel
> will transmit an unsolicited neighbour advertisement on link-layer address
> change to update the neighbour tables of the corresponding hosts more quickly.
> 
> This is the equivalent to arp_notify in ipv4 world.
> 
> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>

Applied to net-next, with the empty line removed.

Thanks.