net: ipv6: Add a sysctl to make optimistic addresses useful candidates

Add a sysctl that causes an interface's optimistic addresses
to be considered equivalent to other non-deprecated addresses
for source address selection purposes.  Preferred addresses
will still take precedence over optimistic addresses, subject
to other ranking in the source address selection algorithm.

This is useful where different interfaces are connected to
different networks from different ISPs (e.g., a cell network
and a home wifi network).

The current behaviour complies with RFC 3484/6724, and it
makes sense if the host has only one interface, or has
multiple interfaces on the same network (same or cooperating
administrative domain(s), but not in the multiple distinct
networks case.

For example, if a mobile device has an IPv6 address on an LTE
network and then connects to IPv6-enabled wifi, while the wifi
IPv6 address is undergoing DAD, IPv6 connections will try use
the wifi default route with the LTE IPv6 address, and will get
stuck until they time out.

Also, because optimistic nodes can receive frames, issue
an RTM_NEWADDR as soon as DAD starts (with the IFA_F_OPTIMSTIC
flag appropriately set).  A second RTM_NEWADDR is sent if DAD
completes (the address flags have changed), otherwise an
RTM_DELADDR is sent.

Also: add an entry in ip-sysctl.txt for optimistic_dad.

[backport of net-next 7fd2561e4ebdd070ebba6d3326c4c5b13942323f]

Signed-off-by: Erik Kline <ek@google.com>
Acked-by: Lorenzo Colitti <lorenzo@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Bug: 17769720
Change-Id: I440a9b8c788db6767d191bbebfd2dff481aa9e0d
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>
net/ping: handle protocol mismatching scenario

ping_lookup() may return a wrong sock if sk_buff's and sock's protocols
dont' match. For example, sk_buff's protocol is ETH_P_IPV6, but sock's
sk_family is AF_INET, in that case, if sk->sk_bound_dev_if is zero, a wrong
sock will be returned.
the fix is to "continue" the searching, if no matching, return NULL.

[cherry-pick of net 91a0b603469069cdcce4d572b7525ffc9fd352a6]

Bug: 18512516
Change-Id: I520223ce53c0d4e155c37d6b65a03489cc7fd494
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: James Morris <jmorris@namei.org>
Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
Cc: Patrick McHardy <kaber@trash.net>
Cc: netdev@vger.kernel.org
Cc: stable@vger.kernel.org
Signed-off-by: Jane Zhou <a17711@motorola.com>
Signed-off-by: Yiwei Zhao <gbjc64@motorola.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>
net: ipv6: allow choosing optimistic addresses with use_optimistic

The use_optimistic sysctl makes optimistic IPv6 addresses
equivalent to preferred addresses for source address selection
(e.g., when calling connect()), but it does not allow an
application to bind to optimistic addresses. This behaviour is
inconsistent - for example, it doesn't make sense for bind() to
an optimistic address fail with EADDRNOTAVAIL, but connect() to
choose that address outgoing address on the same socket.

Bug: 17769720
Bug: 18609055
Change-Id: I9de0d6c92ac45e29d28e318ac626c71806666f13
Signed-off-by: Erik Kline <ek@google.com>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: Chet Kener <Cl3Kener@gmail.com>