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

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>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 17 insertions, 0 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index bcba48a97868..5e11905a4f01 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 a6d7d1c536c3..5a2991cf0251 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 fab23db8ee73..cb803b7bb0d8 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -4037,6 +4037,7 @@ 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)
@@ -4705,6 +4706,13 @@ 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 6ba4b54a550a..f41853bca428 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -1572,11 +1572,18 @@ 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);