net: ipv6: Add IPv6 support to the ping socket.

[backport of net-next 6d0bfe22611602f36617bc7aa2ffa1bbb2f54c67]

This adds the ability to send ICMPv6 echo requests without a
raw socket. The equivalent ability for ICMPv4 was added in
2011.

Instead of having separate code paths for IPv4 and IPv6, make
most of the code in net/ipv4/ping.c dual-stack and only add a
few IPv6-specific bits (like the protocol definition) to a new
net/ipv6/ping.c. Hopefully this will reduce divergence and/or
duplication of bugs in the future.

Caveats:

- Setting options via ancillary data (e.g., using IPV6_PKTINFO
  to specify the outgoing interface) is not yet supported.
- There are no separate security settings for IPv4 and IPv6;
  everything is controlled by /proc/net/ipv4/ping_group_range.
- The proc interface does not yet display IPv6 ping sockets
  properly.

Tested with a patched copy of ping6 and using raw socket calls.
Compiles and works with all of CONFIG_IPV6={n,m,y}.

Change-Id: Ia359af556021344fc7f890c21383aadf950b6498
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
[lorenzo@google.com: backported to 3.0]
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
ping: always initialize ->sin6_scope_id and ->sin6_flowinfo

[net-next commit c26d6b46da3ee86fa8a864347331e5513ca84c2b]

If we don't need scope id, we should initialize it to zero.
Same for ->sin6_flowinfo.

Change-Id: I28e4bc9593e76fc3434052182466fab4bb8ccf3a
Cc: Lorenzo Colitti <lorenzo@google.com>
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Acked-by: Lorenzo Colitti <lorenzo@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
ping: prevent NULL pointer dereference on write to msg_name

A plain read() on a socket does set msg->msg_name to NULL. So check for
NULL pointer first.

[Backport of net-next cf970c002d270c36202bd5b9c2804d3097a52da0]

Bug: 12780426
Change-Id: I29d9cb95ef05ec76d37517e01317f4a29e60931c
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Lorenzo Colitti <lorenzo@google.com>
tcp: add a sysctl to config the tcp_default_init_rwnd

The default initial rwnd was hardcoded to 10.

Now we allow it to be controlled via
  /proc/sys/net/ipv4/tcp_default_init_rwnd
which limits the values from 3 to 100

This is somewhat needed because ipv6 routes are
autoconfigured by the kernel.

See "An Argument for Increasing TCP's Initial Congestion Window"
in https://developers.google.com/speed/articles/tcp_initcwnd_paper.pdf

Change-Id: I7eac8a0a5133371aea9ecb9aec0b608bd7f2cc57
Signed-off-by: JP Abgrall <jpa@google.com>
defconfig: update with recommended config

Change-Id: I0e34630792dbaccec5572f5a2f685192fd63db3a