ipv6: introduce per-interface counter for dad-completed ipv6 addresses

To reduce the number of unnecessary router solicitations, MLDv2 and IGMPv3
messages we need to track the number of valid (as in non-optimistic,
no-dad-failed and non-tentative) link-local addresses. Therefore, this
patch implements a valid_ll_addr_cnt in struct inet6_dev.

We now only emit router solicitations if the first link-local address
finishes duplicate address detection.

The changes for MLDv2 and IGMPv3 are in a follow-up patch.

While there, also simplify one if statement(one minor nit I made in one
of my previous patches):

if (!...)
	do();
else
	return;

<<into>>

if (...)
	return;
do();

Cc: Flavio Leitner <fbl@redhat.com>
Cc: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Cc: David Stevens <dlstevens@us.ibm.com>
Suggested-by: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Acked-by: Flavio Leitner <fbl@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 32 insertions, 8 deletions

diff --git a/include/net/if_inet6.h b/include/net/if_inet6.h
index e4c5a2d2ba34..1628b8f5fb26 100644
--- a/include/net/if_inet6.h
+++ b/include/net/if_inet6.h
@@ -166,6 +166,7 @@ struct inet6_dev {
         struct net_device       *dev;
 
         struct list_head        addr_list;
+        int                     valid_ll_addr_cnt;
 
         struct ifmcaddr6        *mc_list;
         struct ifmcaddr6        *mc_tomb;
diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 4e4cc1fc26d1..20d92ff2d690 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -3277,6 +3277,7 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
 {
         struct net_device *dev = ifp->idev->dev;
         struct in6_addr lladdr;
+        bool send_rs;
 
         addrconf_del_dad_timer(ifp);
 
@@ -3290,20 +3291,25 @@ static void addrconf_dad_completed(struct inet6_ifaddr *ifp)
            router advertisements, start sending router solicitations.
          */
 
-        if (ipv6_accept_ra(ifp->idev) &&
-            ifp->idev->cnf.rtr_solicits > 0 &&
-            (dev->flags&IFF_LOOPBACK) == 0 &&
-            (ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL)) {
+        read_lock_bh(&ifp->idev->lock);
+        spin_lock(&ifp->lock);
+        send_rs = ipv6_accept_ra(ifp->idev) &&
+                  ifp->idev->cnf.rtr_solicits > 0 &&
+                  (dev->flags&IFF_LOOPBACK) == 0 &&
+                  ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL &&
+                  ifp->idev->valid_ll_addr_cnt == 1;
+        spin_unlock(&ifp->lock);
+        read_unlock_bh(&ifp->idev->lock);
+
+        if (send_rs) {
                 /*
                  *      If a host as already performed a random delay
                  *      [...] as part of DAD [...] there is no need
                  *      to delay again before sending the first RS
                  */
-                if (!ipv6_get_lladdr(dev, &lladdr, IFA_F_TENTATIVE))
-                        ndisc_send_rs(dev, &lladdr,
-                                      &in6addr_linklocal_allrouters);
-                else
+                if (ipv6_get_lladdr(dev, &lladdr, IFA_F_TENTATIVE))
                         return;
+                ndisc_send_rs(dev, &lladdr, &in6addr_linklocal_allrouters);
 
                 write_lock_bh(&ifp->idev->lock);
                 spin_lock(&ifp->lock);
@@ -4576,6 +4582,19 @@ errout:
                 rtnl_set_sk_err(net, RTNLGRP_IPV6_PREFIX, err);
 }
 
+static void update_valid_ll_addr_cnt(struct inet6_ifaddr *ifp, int count)
+{
+        write_lock_bh(&ifp->idev->lock);
+        spin_lock(&ifp->lock);
+        if (((ifp->flags & (IFA_F_PERMANENT|IFA_F_TENTATIVE|IFA_F_OPTIMISTIC|
+                            IFA_F_DADFAILED)) == IFA_F_PERMANENT) &&
+            (ipv6_addr_type(&ifp->addr) & IPV6_ADDR_LINKLOCAL))
+                ifp->idev->valid_ll_addr_cnt += count;
+        WARN_ON(ifp->idev->valid_ll_addr_cnt < 0);
+        spin_unlock(&ifp->lock);
+        write_unlock_bh(&ifp->idev->lock);
+}
+
 static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 {
         struct net *net = dev_net(ifp->idev->dev);
@@ -4584,6 +4603,8 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
 
         switch (event) {
         case RTM_NEWADDR:
+                update_valid_ll_addr_cnt(ifp, 1);
+
                 /*
                  * If the address was optimistic
                  * we inserted the route at the start of
@@ -4599,6 +4620,8 @@ static void __ipv6_ifa_notify(int event, struct inet6_ifaddr *ifp)
                                               ifp->idev->dev, 0, 0);
                 break;
         case RTM_DELADDR:
+                update_valid_ll_addr_cnt(ifp, -1);
+
                 if (ifp->idev->cnf.forwarding)
                         addrconf_leave_anycast(ifp);
                 addrconf_leave_solict(ifp->idev, &ifp->addr);