bonding: send IPv6 neighbor advertisement on failover

This patch adds better IPv6 failover support for bonding devices,
especially when in active-backup mode and there are only IPv6 addresses
configured, as reported by Alex Sidorenko.

- Creates a new file, net/drivers/bonding/bond_ipv6.c, for the
   IPv6-specific routines.  Both regular bonds and VLANs over bonds
   are supported.

- Adds a new tunable, num_unsol_na, to limit the number of unsolicited
   IPv6 Neighbor Advertisements that are sent on a failover event.
   Default is 1.

- Creates two new IPv6 neighbor discovery functions:

   ndisc_build_skb()
   ndisc_send_skb()

   These were required to support VLANs since we have to be able to
   add the VLAN id to the skb since ndisc_send_na() and friends
   shouldn't be asked to do this.  These two routines are basically
   __ndisc_send() split into two pieces, in a slightly different order.

- Updates Documentation/networking/bonding.txt and bumps the rev of bond
   support to 3.4.0.

On failover, this new code will generate one packet:

- An unsolicited IPv6 Neighbor Advertisement, which helps the switch
   learn that the address has moved to the new slave.

Testing has shown that sending just the NA results in pretty good
behavior when in active-back mode, I saw no lost ping packets for example.

Signed-off-by: Brian Haley <brian.haley@hp.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@redhat.com>

1 files changed, 65 insertions, 27 deletions

diff --git a/net/ipv6/ndisc.c b/net/ipv6/ndisc.c
index 2a6752dae09d..fbf451c0d77a 100644
--- a/net/ipv6/ndisc.c
+++ b/net/ipv6/ndisc.c
@@ -437,38 +437,20 @@ static void pndisc_destructor(struct pneigh_entry *n)
         ipv6_dev_mc_dec(dev, &maddr);
 }
 
-/*
- *      Send a Neighbour Advertisement
- */
-static void __ndisc_send(struct net_device *dev,
-                         struct neighbour *neigh,
-                         const struct in6_addr *daddr,
-                         const struct in6_addr *saddr,
-                         struct icmp6hdr *icmp6h, const struct in6_addr *target,
-                         int llinfo)
+struct sk_buff *ndisc_build_skb(struct net_device *dev,
+                                const struct in6_addr *daddr,
+                                const struct in6_addr *saddr,
+                                struct icmp6hdr *icmp6h,
+                                const struct in6_addr *target,
+                                int llinfo)
 {
-        struct flowi fl;
-        struct dst_entry *dst;
         struct net *net = dev_net(dev);
         struct sock *sk = net->ipv6.ndisc_sk;
         struct sk_buff *skb;
         struct icmp6hdr *hdr;
-        struct inet6_dev *idev;
         int len;
         int err;
-        u8 *opt, type;
-
-        type = icmp6h->icmp6_type;
-
-        icmpv6_flow_init(sk, &fl, type, saddr, daddr, dev->ifindex);
-
-        dst = icmp6_dst_alloc(dev, neigh, daddr);
-        if (!dst)
-                return;
-
-        err = xfrm_lookup(&dst, &fl, NULL, 0);
-        if (err < 0)
-                return;
+        u8 *opt;
 
         if (!dev->addr_len)
                 llinfo = 0;
@@ -485,8 +467,7 @@ static void __ndisc_send(struct net_device *dev,
                 ND_PRINTK0(KERN_ERR
                            "ICMPv6 ND: %s() failed to allocate an skb.\n",
                            __func__);
-                dst_release(dst);
-                return;
+                return NULL;
         }
 
         skb_reserve(skb, LL_RESERVED_SPACE(dev));
@@ -513,6 +494,42 @@ static void __ndisc_send(struct net_device *dev,
                                            csum_partial((__u8 *) hdr,
                                                         len, 0));
 
+        return skb;
+}
+
+EXPORT_SYMBOL(ndisc_build_skb);
+
+void ndisc_send_skb(struct sk_buff *skb,
+                    struct net_device *dev,
+                    struct neighbour *neigh,
+                    const struct in6_addr *daddr,
+                    const struct in6_addr *saddr,
+                    struct icmp6hdr *icmp6h)
+{
+        struct flowi fl;
+        struct dst_entry *dst;
+        struct net *net = dev_net(dev);
+        struct sock *sk = net->ipv6.ndisc_sk;
+        struct inet6_dev *idev;
+        int err;
+        u8 type;
+
+        type = icmp6h->icmp6_type;
+
+        icmpv6_flow_init(sk, &fl, type, saddr, daddr, dev->ifindex);
+
+        dst = icmp6_dst_alloc(dev, neigh, daddr);
+        if (!dst) {
+                kfree_skb(skb);
+                return;
+        }
+
+        err = xfrm_lookup(&dst, &fl, NULL, 0);
+        if (err < 0) {
+                kfree_skb(skb);
+                return;
+        }
+
         skb->dst = dst;
 
         idev = in6_dev_get(dst->dev);
@@ -529,6 +546,27 @@ static void __ndisc_send(struct net_device *dev,
                 in6_dev_put(idev);
 }
 
+EXPORT_SYMBOL(ndisc_send_skb);
+
+/*
+ *      Send a Neighbour Discover packet
+ */
+static void __ndisc_send(struct net_device *dev,
+                         struct neighbour *neigh,
+                         const struct in6_addr *daddr,
+                         const struct in6_addr *saddr,
+                         struct icmp6hdr *icmp6h, const struct in6_addr *target,
+                         int llinfo)
+{
+        struct sk_buff *skb;
+
+        skb = ndisc_build_skb(dev, daddr, saddr, icmp6h, target, llinfo);
+        if (!skb)
+                return;
+
+        ndisc_send_skb(skb, dev, neigh, daddr, saddr, icmp6h);
+}
+
 static void ndisc_send_na(struct net_device *dev, struct neighbour *neigh,
                           const struct in6_addr *daddr,
                           const struct in6_addr *solicited_addr,