This patch allows to switch the netns when packet is encapsulated or
decapsulated. In other word, the encapsulated packet is received in a netns,
where the lookup is done to find the tunnel. Once the tunnel is found, the
packet is decapsulated and injecting into the corresponding interface which
stands to another netns.

When one of the two netns is removed, the tunnel is destroyed.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When testing GRE tunnel, I got:

 # ip tunnel show
 get tunnel gre0 failed: Invalid argument
 get tunnel gre1 failed: Invalid argument

This is a regression introduced by commit c5441932
("GRE: Refactor GRE tunneling code.") because previously we
only check the parameters for SIOCADDTUNNEL and SIOCCHGTUNNEL,
after that commit, the check is moved for all commands.

So, just check for SIOCADDTUNNEL and SIOCCHGTUNNEL.

After this patch I got:

 # ip tunnel show
 gre0: gre/ip  remote any  local any  ttl inherit  nopmtudisc
 gre1: gre/ip  remote 192.168.122.101  local 192.168.122.45  ttl inherit

Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This is required for OVS GRE offloading.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This is required for ovs gre module.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Currently there is only one user is allowed to register for gre
protocol.  Following patch adds de-multiplexer.  So that multiple
modules can listen on gre protocol e.g. kernel gre devices and ovs.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Before this patch, ip_tunnel_xmit() was using the field protocol from the IP
header passed into argument.
There is no functional change, this patch prepares the support of IPv4 over
IPv4 for module sit.
Signed-off-by: NNicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Another fix needed in ipgre_err(), as parse_gre_header() might change
skb->head.

Bug added in commit c5441932 (GRE: Refactor GRE tunneling code.)
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Need remove erroneous semicolon, which is found by EXTRA_CFLAGS=-W,
the related commit number: c5441932
("GRE: Refactor GRE tunneling code")
Signed-off-by: NChen Gang <gang.chen@asianux.com>
Acked-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

pskb_may_pull() can change skb->head, so we must init iph/greh after
calling it.

Bug added in commit c5441932 (GRE: Refactor GRE tunneling code.)
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

iflink is currently set to 0 in __gre_tunnel_init(). This
function is invoked in gre_tap_init() and
ipgre_tunnel_init() which are both used to initialise the
ndo_init field of the respective net_device_ops structs
(ipgre.. and gre_tap..) used by GRE interfaces.

However, in netdevice_register() iflink is first set to -1,
then ndo_init is invoked and then iflink is assigned to a
proper value if and only if it still was -1.

Assigning 0 to iflink in ndo_init is therefore first
preventing netdev_register() to correctly assign it a proper
value and then breaking iflink at all since 0 has not
correct meaning.

Fix this by removing the iflink assignment in
__gre_tunnel_init().

Introduced by c5441932
("GRE: Refactor GRE tunneling code.")
Reported-by: NFengguang Wu <fengguang.wu@intel.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NAntonio Quartulli <ordex@autistici.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Following patch refactors GRE code into ip tunneling code and GRE
specific code. Common tunneling code is moved to ip_tunnel module.
ip_tunnel module is written as generic library which can be used
by different tunneling implementations.

ip_tunnel module contains following components:
 - packet xmit and rcv generic code. xmit flow looks like
   (gre_xmit/ipip_xmit)->ip_tunnel_xmit->ip_local_out.
 - hash table of all devices.
 - lookup for tunnel devices.
 - control plane operations like device create, destroy, ioctl, netlink
   operations code.
 - registration for tunneling modules, like gre, ipip etc.
 - define single pcpu_tstats dev->tstats.
 - struct tnl_ptk_info added to pass parsed tunnel packet parameters.

ipip.h header is renamed to ip_tunnel.h
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This reverts commit 412ed947.

The commit is wrong as tiph points to the outer IPv4 header which is
installed at ipgre_header() and not the inner one which is protocol dependant.

This commit broke succesfully opennhrp which use PF_PACKET socket with
ETH_P_NHRP protocol. Additionally ssl_addr is set to the link-layer
IPv4 address. This address is written by ipgre_header() to the skb
earlier, and this is the IPv4 header tiph should point to - regardless
of the inner protocol payload.
Signed-off-by: NTimo Teräs <timo.teras@iki.fi>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With recent patches from Pravin, most tunnels can't use iptunnel_xmit()
any more, due to ip_select_ident() and skb->ip_summed. But we can just
move these operations out of iptunnel_xmit(), so that tunnels can
use it again.

This by the way fixes a bug in vxlan (missing nf_reset()) for net-next.

Cc: Pravin B Shelar <pshelar@nicira.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: "David S. Miller" <davem@davemloft.net>
Signed-off-by: NCong Wang <xiyou.wangcong@gmail.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This reverts commit eb6b9a8c.

Above commit limits GSO capability of gre device to just TSO, but
software GRE-GSO is capable of handling all GSO capabilities.

This patch also fixes following panic which reverted commit introduced:-

BUG: unable to handle kernel NULL pointer dereference at 00000000000000a2
IP: [<ffffffffa0680fd1>] ipgre_tunnel_bind_dev+0x161/0x1f0 [ip_gre]
PGD 42bc19067 PUD 42bca9067 PMD 0
Oops: 0000 [#1] SMP
Pid: 2636, comm: ip Tainted: GF            3.8.0+ #83 Dell Inc. PowerEdge R620/0KCKR5
RIP: 0010:[<ffffffffa0680fd1>]  [<ffffffffa0680fd1>] ipgre_tunnel_bind_dev+0x161/0x1f0 [ip_gre]
RSP: 0018:ffff88042bfcb708  EFLAGS: 00010246
RAX: 00000000000005b6 RBX: ffff88042d2fa000 RCX: 0000000000000044
RDX: 0000000000000018 RSI: 0000000000000078 RDI: 0000000000000060
RBP: ffff88042bfcb748 R08: 0000000000000018 R09: 000000000000000c
R10: 0000000000000020 R11: 000000000101010a R12: ffff88042d2fa800
R13: 0000000000000000 R14: ffff88042d2fa800 R15: ffff88042cd7f650
FS:  00007fa784f55700(0000) GS:ffff88043fd20000(0000) knlGS:0000000000000000
CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00000000000000a2 CR3: 000000042d8b9000 CR4: 00000000000407e0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000ffff0ff0 DR7: 0000000000000400
Process ip (pid: 2636, threadinfo ffff88042bfca000, task ffff88042d142a80)
Stack:
 0000000100000000 002f000000000000 0a01010100000000 000000000b010101
 ffff88042d2fa800 ffff88042d2fa000 ffff88042bfcb858 ffff88042f418c00
 ffff88042bfcb798 ffffffffa068199a ffff88042bfcb798 ffff88042d2fa830
Call Trace:
 [<ffffffffa068199a>] ipgre_newlink+0xca/0x160 [ip_gre]
 [<ffffffff8143b692>] rtnl_newlink+0x532/0x5f0
 [<ffffffff8143b2fc>] ? rtnl_newlink+0x19c/0x5f0
 [<ffffffff81438978>] rtnetlink_rcv_msg+0x2c8/0x340
 [<ffffffff814386b0>] ? rtnetlink_rcv+0x40/0x40
 [<ffffffff814560f9>] netlink_rcv_skb+0xa9/0xd0
 [<ffffffff81438695>] rtnetlink_rcv+0x25/0x40
 [<ffffffff81455ddc>] netlink_unicast+0x1ac/0x230
 [<ffffffff81456a45>] netlink_sendmsg+0x265/0x380
 [<ffffffff814138c0>] sock_sendmsg+0xb0/0xe0
 [<ffffffff8141141e>] ? move_addr_to_kernel+0x4e/0x90
 [<ffffffff81420445>] ? verify_iovec+0x85/0xf0
 [<ffffffff81414ffd>] __sys_sendmsg+0x3fd/0x420
 [<ffffffff8114b701>] ? handle_mm_fault+0x251/0x3b0
 [<ffffffff8114f39f>] ? vma_link+0xcf/0xe0
 [<ffffffff81415239>] sys_sendmsg+0x49/0x90
 [<ffffffff814ffd19>] system_call_fastpath+0x16/0x1b

CC: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Acked-by: NDmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

commit "ip_gre: allow CSUM capable devices to handle packets"
aa0e51cd, broke GRE_CSUM case.
GRE_CSUM needs checksum computed for inner packet. Therefore
csum-calculation can not be offloaded if tunnel device requires
GRE_CSUM.  Following patch fixes it by computing inner packet checksum
for GRE_CSUM type, for all other type of GRE devices csum is offloaded.

CC: Dmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Acked-by: NDmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

GRE-GSO generates ip fragments with id 0,2,3,4... for every
GSO packet, which is not correct. Following patch fixes it
by setting ip-header id unique id of fragments are allowed.
As Eric Dumazet suggested it is optimized by using inner ip-header
whenever inner packet is ipv4.
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

commit 68c33163 (v4 GRE: Add TCP segmentation offload for GRE)
introduced a bug in error path.

dst is attached to skb, so will be released when skb is freed.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Pravin B Shelar <pshelar@nicira.com>
Acked-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NDmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

If device is not able to handle checksumming it will
be handled in dev_xmit
Signed-off-by: NDmitry Kravkov <dmitry@broadcom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Following patch adds GRE protocol offload handler so that
skb_gso_segment() can segment GRE packets.
SKB GSO CB is added to keep track of total header length so that
skb_segment can push entire header. e.g. in case of GRE, skb_segment
need to push inner and outer headers to every segment.
New NETIF_F_GRE_GSO feature is added for devices which support HW
GRE TSO offload. Currently none of devices support it therefore GRE GSO
always fall backs to software GSO.

[ Compute pkt_len before ip_local_out() invocation. -DaveM ]
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

A GRE tunnel can be configured so that outgoing tunnel packets inherit
the value of the TOS field from the inner IP header. In doing so, when
a non-IP packet is transmitted through the tunnel, the TOS field will
always be set to 0.

Instead, the user should be able to configure a different TOS value as
the fallback to use for non-IP packets. This is helpful when the non-IP
packets are all control packets and should be handled by routers outside
the tunnel as having Internet Control precedence. One example of this is
the NHRP packets that control a DMVPN-compatible mGRE tunnel; they are
encapsulated directly by GRE and do not contain an inner IP header.

Under the existing behavior, the IFLA_GRE_TOS parameter must be set to
'1' for the TOS value to be inherited. Now, only the least significant
bit of this parameter must be set to '1', and when a non-IP packet is
sent through the tunnel, the upper 6 bits of this same parameter will be
copied into the TOS field. (The ECN bits get masked off as before.)

This behavior is backwards-compatible with existing configurations and
iproute2 versions.
Signed-off-by: NDavid Ward <david.ward@ll.mit.edu>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pravin Shelar mentioned that GSO could potentially generate
wrong TX checksum if skb has fragments that are overwritten
by the user between the checksum computation and transmit.

He suggested to linearize skbs but this extra copy can be
avoided for normal tcp skbs cooked by tcp_sendmsg().

This patch introduces a new SKB_GSO_SHARED_FRAG flag, set
in skb_shinfo(skb)->gso_type if at least one frag can be
modified by the user.

Typical sources of such possible overwrites are {vm}splice(),
sendfile(), and macvtap/tun/virtio_net drivers.

Tested:

$ netperf -H 7.7.8.84
MIGRATED TCP STREAM TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to
7.7.8.84 () port 0 AF_INET
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380  16384  16384    10.00    3959.52

$ netperf -H 7.7.8.84 -t TCP_SENDFILE
TCP SENDFILE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to 7.7.8.84 ()
port 0 AF_INET
Recv   Send    Send
Socket Socket  Message  Elapsed
Size   Size    Size     Time     Throughput
bytes  bytes   bytes    secs.    10^6bits/sec

 87380  16384  16384    10.00    3216.80

Performance of the SENDFILE is impacted by the extra allocation and
copy, and because we use order-0 pages, while the TCP_STREAM uses
bigger pages.
Reported-by: NPravin Shelar <pshelar@nicira.com>
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Due to IP_GRE GSO support, GRE can recieve non linear skb which
results in panic in case of GRE_CSUM.  Following patch fixes it by
using correct csum API.

Bug introduced in commit 6b78f16e (gre: add GSO support)
Signed-off-by: NPravin B Shelar <pshelar@nicira.com>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

ipgre_tunnel_xmit() incorrectly sets transport header to inner payload
instead of GRE header. It seems copy-and-pasted from ipip.c.
So set transport header to gre header.
(In ipip case the transport header is the inner ip header, so that's
correct.)

Found by inspection. In practice the incorrect transport header
doesn't matter because the skb usually is sent to another net_device
or socket, so the transport header isn't referenced.
Signed-off-by: NIsaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Once skb_realloc_headroom() is called, tiph might point to freed memory.

Cache tiph->ttl value before the reallocation, to avoid unexpected
behavior.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Isaku Yamahata <yamahata@valinux.co.jp>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

ipgre_tunnel_xmit() parses network header as IP unconditionally.
But transmitting packets are not always IP packet. For example such packet
can be sent by packet socket with sockaddr_ll.sll_protocol set.
So make the function check if skb->protocol is IP.
Signed-off-by: NIsaku Yamahata <yamahata@valinux.co.jp>
Acked-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Allow an unpriviled user who has created a user namespace, and then
created a network namespace to effectively use the new network
namespace, by reducing capable(CAP_NET_ADMIN) and
capable(CAP_NET_RAW) calls to be ns_capable(net->user_ns,
CAP_NET_ADMIN), or capable(net->user_ns, CAP_NET_RAW) calls.

Settings that merely control a single network device are allowed.
Either the network device is a logical network device where
restrictions make no difference or the network device is hardware NIC
that has been explicity moved from the initial network namespace.

In general policy and network stack state changes are allowed
while resource control is left unchanged.

Allow creating raw sockets.
Allow the SIOCSARP ioctl to control the arp cache.
Allow the SIOCSIFFLAG ioctl to allow setting network device flags.
Allow the SIOCSIFADDR ioctl to allow setting a netdevice ipv4 address.
Allow the SIOCSIFBRDADDR ioctl to allow setting a netdevice ipv4 broadcast address.
Allow the SIOCSIFDSTADDR ioctl to allow setting a netdevice ipv4 destination address.
Allow the SIOCSIFNETMASK ioctl to allow setting a netdevice ipv4 netmask.
Allow the SIOCADDRT and SIOCDELRT ioctls to allow adding and deleting ipv4 routes.

Allow the SIOCADDTUNNEL, SIOCCHGTUNNEL and SIOCDELTUNNEL ioctls for
adding, changing and deleting gre tunnels.

Allow the SIOCADDTUNNEL, SIOCCHGTUNNEL and SIOCDELTUNNEL ioctls for
adding, changing and deleting ipip tunnels.

Allow the SIOCADDTUNNEL, SIOCCHGTUNNEL and SIOCDELTUNNEL ioctls for
adding, changing and deleting ipsec virtual tunnel interfaces.

Allow setting the MRT_INIT, MRT_DONE, MRT_ADD_VIF, MRT_DEL_VIF, MRT_ADD_MFC,
MRT_DEL_MFC, MRT_ASSERT, MRT_PIM, MRT_TABLE socket options on multicast routing
sockets.

Allow setting and receiving IPOPT_CIPSO, IP_OPT_SEC, IP_OPT_SID and
arbitrary ip options.

Allow setting IP_SEC_POLICY/IP_XFRM_POLICY ipv4 socket option.
Allow setting the IP_TRANSPARENT ipv4 socket option.
Allow setting the TCP_REPAIR socket option.
Allow setting the TCP_CONGESTION socket option.
Signed-off-by: N"Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The defitions of for_each_ip_tunnel_rcu() are same,
so unify it. Also, don't hide the parameter 't'.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

__IPTUNNEL_XMIT() is an ugly macro, convert it to a static
inline function, so make it more readable.

IPTUNNEL_XMIT() is unused, just remove it.

Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: NCong Wang <amwang@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Use be16 consistently when looking at flags.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add GRO capability to IPv4 GRE tunnels, using the gro_cells
infrastructure.

Tested using IPv4 and IPv6 TCP traffic inside this tunnel, and
checking GRO is building large packets.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Linux tunnels were written before RFC6040 and therefore never
implemented the corner case of ECN getting set in the outer header
and the inner header not being ready for it.

Section 4.2.  Default Tunnel Egress Behaviour.
 o If the inner ECN field is Not-ECT, the decapsulator MUST NOT
      propagate any other ECN codepoint onwards.  This is because the
      inner Not-ECT marking is set by transports that rely on dropped
      packets as an indication of congestion and would not understand or
      respond to any other ECN codepoint [RFC4774].  Specifically:

      *  If the inner ECN field is Not-ECT and the outer ECN field is
         CE, the decapsulator MUST drop the packet.

      *  If the inner ECN field is Not-ECT and the outer ECN field is
         Not-ECT, ECT(0), or ECT(1), the decapsulator MUST forward the
         outgoing packet with the ECN field cleared to Not-ECT.

This patch moves the ECN decap logic out of the individual tunnels
into a common place.

It also adds logging to allow detecting broken systems that
set ECN bits incorrectly when tunneling (or an intermediate
router might be changing the header).

Overloads rx_frame_error to keep track of ECN related error.

Thanks to Chris Wright who caught this while reviewing the new VXLAN
tunnel.

This code was tested by injecting faulty logic in other end GRE
to send incorrectly encapsulated packets.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The gre function pointers for receive and error handling are
always called (from gre.c) with rcu_read_lock already held.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

GRE driver incorrectly uses zero as a flag value. Zero is a perfectly
valid value for key, and the tunnel should match packets with no key only
with tunnels created without key, and vice versa.

This is a slightly visible  change since previously it might be possible to
construct a working tunnel that sent key 0 and received only because
of the key wildcard of zero.  I.e the sender sent key of zero, but tunnel
was defined without key.

Note: using gre key 0 requires iproute2 utilities v3.2 or later.
The original utility code was broken as well.
Signed-off-by: NStephen Hemminger <shemminger@vyatta.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Add GSO support to GRE tunnels.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Maciej Żenczykowski <maze@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

In order to allow prefixed routes, we have to adjust how rt_gateway
is set and interpreted.

The new interpretation is:

1) rt_gateway == 0, destination is on-link, nexthop is iph->daddr

2) rt_gateway != 0, destination requires a nexthop gateway

Abstract the fetching of the proper nexthop value using a new
inline helper, rt_nexthop(), as suggested by Joe Perches.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>
Tested-by: NVijay Subramanian <subramanian.vijay@gmail.com>

This will be used so that we can compose a full flow key.

Even though we have a route in this context, we need more.  In the
future the routes will be without destination address, source address,
etc. keying.  One ipv4 route will cover entire subnets, etc.

In this environment we have to have a way to possess persistent storage
for redirects and PMTU information.  This persistent storage will exist
in the FIB tables, and that's why we'll need to be able to rebuild a
full lookup flow key here.  Using that flow key will do a fib_lookup()
and create/update the persistent entry.
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Signed-off-by: NDavid S. Miller <davem@davemloft.net>

With ip_rt_frag_needed() removed, we have to explicitly update PMTU
information in every ICMP error handler.

Create two helper functions to facilitate this.

1) ipv4_sk_update_pmtu()

   This updates the PMTU when we have a socket context to
   work with.

2) ipv4_update_pmtu()

   Raw version, used when no socket context is available.  For this
   interface, we essentially just pass in explicit arguments for
   the flow identity information we would have extracted from the
   socket.

   And you'll notice that ipv4_sk_update_pmtu() is simply implemented
   in terms of ipv4_update_pmtu()

Note that __ip_route_output_key() is used, rather than something like
ip_route_output_flow() or ip_route_output_key().  This is because we
absolutely do not want to end up with a route that does IPSEC
encapsulation and the like.  Instead, we only want the route that
would get us to the node described by the outermost IP header.
Reported-by: NSteffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Fix checkpatch errors of the following type:
	* ERROR: "foo * bar" should be "foo *bar"
	* ERROR: "(foo*)" should be "(foo *)"
Signed-off-by: NDaniel Baluta <dbaluta@ixiacom.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>