[IPV6] ADDRCONF: Optimistic Duplicate Address Detection (RFC 4429) Support.

Nominally an autoconfigured IPv6 address is added to an interface in the
Tentative state (as per RFC 2462).  Addresses in this state remain in this
state while the Duplicate Address Detection process operates on them to
determine their uniqueness on the network.  During this period, these
tentative addresses may not be used for communication, increasing the time
before a node may be able to communicate on a network.  Using Optimistic
Duplicate Address Detection, autoconfigured addresses may be used
immediately for communication on the network, as long as certain rules are
followed to avoid conflicts with other nodes during the Duplicate Address
Detection process.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 35 insertions, 0 deletions

diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 0d60fbc59d8f..7e25043d826c 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -863,6 +863,41 @@ static int ip6_dst_lookup_tail(struct sock *sk,
                         goto out_err_release;
         }
 
+#ifdef CONFIG_IPV6_OPTIMISTIC_DAD
+                /*
+                 * Here if the dst entry we've looked up
+                 * has a neighbour entry that is in the INCOMPLETE
+                 * state and the src address from the flow is
+                 * marked as OPTIMISTIC, we release the found
+                 * dst entry and replace it instead with the
+                 * dst entry of the nexthop router
+                 */
+                if (!((*dst)->neighbour->nud_state & NUD_VALID)) {
+                        struct inet6_ifaddr *ifp;
+                        struct flowi fl_gw;
+                        int redirect;
+
+                        ifp = ipv6_get_ifaddr(&fl->fl6_src, (*dst)->dev, 1);
+
+                        redirect = (ifp && ifp->flags & IFA_F_OPTIMISTIC);
+                        if (ifp)
+                                in6_ifa_put(ifp);
+
+                        if (redirect) {
+                                /*
+                                 * We need to get the dst entry for the
+                                 * default router instead
+                                 */
+                                dst_release(*dst);
+                                memcpy(&fl_gw, fl, sizeof(struct flowi));
+                                memset(&fl_gw.fl6_dst, 0, sizeof(struct in6_addr));
+                                *dst = ip6_route_output(sk, &fl_gw);
+                                if ((err = (*dst)->error))
+                                        goto out_err_release;
+                        }
+                }
+#endif
+
         return 0;
 
 out_err_release: