Manage pending per-NAPI GRO packets via list_head.

Return an SKB pointer from the GRO receive handlers.  When GRO receive
handlers return non-NULL, it means that this SKB needs to be completed
at this time and removed from the NAPI queue.

Several operations are greatly simplified by this transformation,
especially timing out the oldest SKB in the list when gro_count
exceeds MAX_GRO_SKBS, and napi_gro_flush() which walks the queue
in reverse order.

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

This patch adds support for a software provided checksum and GSO_PARTIAL
segmentation support. With this we can offload UDP segmentation on devices
that only have partial support for tunnels.

Since we are no longer needing the hardware checksum we can drop the checks
in the segmentation code that were verifying if it was present.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

This patch is meant to allow us to avoid having to recompute the checksum
from scratch and have it passed as a parameter.

Instead of taking that approach we can take advantage of the fact that the
length that was used to compute the existing checksum is included in the
UDP header.

Finally to avoid the need to invert the result we can just call csum16_add
and csum16_sub directly. By doing this we can avoid a number of
instructions in the loop that is handling segmentation.

Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

There is no point in passing MSS as a parameter for for the GSO
segmentation call as it is already available via the shared info for the
skb itself.

Reviewed-by: Eric Dumazet <edumazet@google.com>
Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Alexander Duyck <alexander.h.duyck@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Implement generic segmentation offload support for udp datagrams. A
follow-up patch adds support to the protocol stack to generate such
packets.

UDP GSO is not UFO. UFO fragments a single large datagram. GSO splits
a large payload into a number of discrete UDP datagrams.

The implementation adds a GSO type SKB_UDP_GSO_L4 to differentiate it
from UFO (SKB_UDP_GSO).

IPPROTO_UDPLITE is excluded, as that protocol has no gso handler
registered.

[ Export __udp_gso_segment for ipv6. -DaveM ]

Signed-off-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Validate gso_type during segmentation as SKB_GSO_DODGY sources
may pass packets where the gso_type does not match the contents.

Syzkaller was able to enter the SCTP gso handler with a packet of
gso_type SKB_GSO_TCPV4.

On entry of transport layer gso handlers, verify that the gso_type
matches the transport protocol.

Fixes: 90017accff61 ("sctp: Add GSO support")
Link: http://lkml.kernel.org/r/<001a1137452496ffc305617e5fe0@google.com>
Reported-by: syzbot+fee64147a25aecd48055@syzkaller.appspotmail.com
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Tuntap and similar devices can inject GSO packets. Accept type
VIRTIO_NET_HDR_GSO_UDP, even though not generating UFO natively.

Processes are expected to use feature negotiation such as TUNSETOFFLOAD
to detect supported offload types and refrain from injecting other
packets. This process breaks down with live migration: guest kernels
do not renegotiate flags, so destination hosts need to expose all
features that the source host does.

Partially revert the UFO removal from 182e0b6b5846~1..d9d30adf5677.
This patch introduces nearly(*) no new code to simplify verification.
It brings back verbatim tuntap UFO negotiation, VIRTIO_NET_HDR_GSO_UDP
insertion and software UFO segmentation.

It does not reinstate protocol stack support, hardware offload
(NETIF_F_UFO), SKB_GSO_UDP tunneling in SKB_GSO_SOFTWARE or reception
of VIRTIO_NET_HDR_GSO_UDP packets in tuntap.

To support SKB_GSO_UDP reappearing in the stack, also reinstate
logic in act_csum and openvswitch. Achieve equivalence with v4.13 HEAD
by squashing in commit 939912216fa8 ("net: skb_needs_check() removes
CHECKSUM_UNNECESSARY check for tx.") and reverting commit 8d63bee643f1
("net: avoid skb_warn_bad_offload false positives on UFO").

(*) To avoid having to bring back skb_shinfo(skb)->ip6_frag_id,
ipv6_proxy_select_ident is changed to return a __be32 and this is
assigned directly to the frag_hdr. Also, SKB_GSO_UDP is inserted
at the end of the enum to minimize code churn.

Tested
  Booted a v4.13 guest kernel with QEMU. On a host kernel before this
  patch `ethtool -k eth0` shows UFO disabled. After the patch, it is
  enabled, same as on a v4.13 host kernel.

  A UFO packet sent from the guest appears on the tap device:
    host:
      nc -l -p -u 8000 &
      tcpdump -n -i tap0

    guest:
      dd if=/dev/zero of=payload.txt bs=1 count=2000
      nc -u 192.16.1.1 8000 < payload.txt

  Direct tap to tap transmission of VIRTIO_NET_HDR_GSO_UDP succeeds,
  packets arriving fragmented:

    ./with_tap_pair.sh ./tap_send_ufo tap0 tap1
    (from https://github.com/wdebruij/kerneltools/tree/master/tests)

Changes
  v1 -> v2
    - simplified set_offload change (review comment)
    - documented test procedure

Link: http://lkml.kernel.org/r/<CAF=yD-LuUeDuL9YWPJD9ykOZ0QCjNeznPDr6whqZ9NGMNF12Mw@mail.gmail.com>
Fixes: fb652fdfe837 ("macvlan/macvtap: Remove NETIF_F_UFO advertisement.")
Reported-by: Michal Kubecek <mkubecek@suse.cz>
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

Rename udp{4,6}_ufo_fragment() to udp{4,6}_tunnel_segment() and only
handle tunnel segmentation.

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

Do not use unsigned variables to see if it returns a negative
error or not.

Fixes: 2423496af35d ("ipv6: Prevent overrun when parsing v6 header options")
Reported-by: Julia Lawall <julia.lawall@lip6.fr>
Signed-off-by: David S. Miller <davem@davemloft.net>

The KASAN warning repoted below was discovered with a syzkaller
program.  The reproducer is basically:
  int s = socket(AF_INET6, SOCK_RAW, NEXTHDR_HOP);
  send(s, &one_byte_of_data, 1, MSG_MORE);
  send(s, &more_than_mtu_bytes_data, 2000, 0);

The socket() call sets the nexthdr field of the v6 header to
NEXTHDR_HOP, the first send call primes the payload with a non zero
byte of data, and the second send call triggers the fragmentation path.

The fragmentation code tries to parse the header options in order
to figure out where to insert the fragment option.  Since nexthdr points
to an invalid option, the calculation of the size of the network header
can made to be much larger than the linear section of the skb and data
is read outside of it.

This fix makes ip6_find_1stfrag return an error if it detects
running out-of-bounds.

[   42.361487] ==================================================================
[   42.364412] BUG: KASAN: slab-out-of-bounds in ip6_fragment+0x11c8/0x3730
[   42.365471] Read of size 840 at addr ffff88000969e798 by task ip6_fragment-oo/3789
[   42.366469]
[   42.366696] CPU: 1 PID: 3789 Comm: ip6_fragment-oo Not tainted 4.11.0+ #41
[   42.367628] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.1-1ubuntu1 04/01/2014
[   42.368824] Call Trace:
[   42.369183]  dump_stack+0xb3/0x10b
[   42.369664]  print_address_description+0x73/0x290
[   42.370325]  kasan_report+0x252/0x370
[   42.370839]  ? ip6_fragment+0x11c8/0x3730
[   42.371396]  check_memory_region+0x13c/0x1a0
[   42.371978]  memcpy+0x23/0x50
[   42.372395]  ip6_fragment+0x11c8/0x3730
[   42.372920]  ? nf_ct_expect_unregister_notifier+0x110/0x110
[   42.373681]  ? ip6_copy_metadata+0x7f0/0x7f0
[   42.374263]  ? ip6_forward+0x2e30/0x2e30
[   42.374803]  ip6_finish_output+0x584/0x990
[   42.375350]  ip6_output+0x1b7/0x690
[   42.375836]  ? ip6_finish_output+0x990/0x990
[   42.376411]  ? ip6_fragment+0x3730/0x3730
[   42.376968]  ip6_local_out+0x95/0x160
[   42.377471]  ip6_send_skb+0xa1/0x330
[   42.377969]  ip6_push_pending_frames+0xb3/0xe0
[   42.378589]  rawv6_sendmsg+0x2051/0x2db0
[   42.379129]  ? rawv6_bind+0x8b0/0x8b0
[   42.379633]  ? _copy_from_user+0x84/0xe0
[   42.380193]  ? debug_check_no_locks_freed+0x290/0x290
[   42.380878]  ? ___sys_sendmsg+0x162/0x930
[   42.381427]  ? rcu_read_lock_sched_held+0xa3/0x120
[   42.382074]  ? sock_has_perm+0x1f6/0x290
[   42.382614]  ? ___sys_sendmsg+0x167/0x930
[   42.383173]  ? lock_downgrade+0x660/0x660
[   42.383727]  inet_sendmsg+0x123/0x500
[   42.384226]  ? inet_sendmsg+0x123/0x500
[   42.384748]  ? inet_recvmsg+0x540/0x540
[   42.385263]  sock_sendmsg+0xca/0x110
[   42.385758]  SYSC_sendto+0x217/0x380
[   42.386249]  ? SYSC_connect+0x310/0x310
[   42.386783]  ? __might_fault+0x110/0x1d0
[   42.387324]  ? lock_downgrade+0x660/0x660
[   42.387880]  ? __fget_light+0xa1/0x1f0
[   42.388403]  ? __fdget+0x18/0x20
[   42.388851]  ? sock_common_setsockopt+0x95/0xd0
[   42.389472]  ? SyS_setsockopt+0x17f/0x260
[   42.390021]  ? entry_SYSCALL_64_fastpath+0x5/0xbe
[   42.390650]  SyS_sendto+0x40/0x50
[   42.391103]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[   42.391731] RIP: 0033:0x7fbbb711e383
[   42.392217] RSP: 002b:00007ffff4d34f28 EFLAGS: 00000246 ORIG_RAX: 000000000000002c
[   42.393235] RAX: ffffffffffffffda RBX: 0000000000000000 RCX: 00007fbbb711e383
[   42.394195] RDX: 0000000000001000 RSI: 00007ffff4d34f60 RDI: 0000000000000003
[   42.395145] RBP: 0000000000000046 R08: 00007ffff4d34f40 R09: 0000000000000018
[   42.396056] R10: 0000000000000000 R11: 0000000000000246 R12: 0000000000400aad
[   42.396598] R13: 0000000000000066 R14: 00007ffff4d34ee0 R15: 00007fbbb717af00
[   42.397257]
[   42.397411] Allocated by task 3789:
[   42.397702]  save_stack_trace+0x16/0x20
[   42.398005]  save_stack+0x46/0xd0
[   42.398267]  kasan_kmalloc+0xad/0xe0
[   42.398548]  kasan_slab_alloc+0x12/0x20
[   42.398848]  __kmalloc_node_track_caller+0xcb/0x380
[   42.399224]  __kmalloc_reserve.isra.32+0x41/0xe0
[   42.399654]  __alloc_skb+0xf8/0x580
[   42.400003]  sock_wmalloc+0xab/0xf0
[   42.400346]  __ip6_append_data.isra.41+0x2472/0x33d0
[   42.400813]  ip6_append_data+0x1a8/0x2f0
[   42.401122]  rawv6_sendmsg+0x11ee/0x2db0
[   42.401505]  inet_sendmsg+0x123/0x500
[   42.401860]  sock_sendmsg+0xca/0x110
[   42.402209]  ___sys_sendmsg+0x7cb/0x930
[   42.402582]  __sys_sendmsg+0xd9/0x190
[   42.402941]  SyS_sendmsg+0x2d/0x50
[   42.403273]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[   42.403718]
[   42.403871] Freed by task 1794:
[   42.404146]  save_stack_trace+0x16/0x20
[   42.404515]  save_stack+0x46/0xd0
[   42.404827]  kasan_slab_free+0x72/0xc0
[   42.405167]  kfree+0xe8/0x2b0
[   42.405462]  skb_free_head+0x74/0xb0
[   42.405806]  skb_release_data+0x30e/0x3a0
[   42.406198]  skb_release_all+0x4a/0x60
[   42.406563]  consume_skb+0x113/0x2e0
[   42.406910]  skb_free_datagram+0x1a/0xe0
[   42.407288]  netlink_recvmsg+0x60d/0xe40
[   42.407667]  sock_recvmsg+0xd7/0x110
[   42.408022]  ___sys_recvmsg+0x25c/0x580
[   42.408395]  __sys_recvmsg+0xd6/0x190
[   42.408753]  SyS_recvmsg+0x2d/0x50
[   42.409086]  entry_SYSCALL_64_fastpath+0x1f/0xbe
[   42.409513]
[   42.409665] The buggy address belongs to the object at ffff88000969e780
[   42.409665]  which belongs to the cache kmalloc-512 of size 512
[   42.410846] The buggy address is located 24 bytes inside of
[   42.410846]  512-byte region [ffff88000969e780, ffff88000969e980)
[   42.411941] The buggy address belongs to the page:
[   42.412405] page:ffffea000025a780 count:1 mapcount:0 mapping:          (null) index:0x0 compound_mapcount: 0
[   42.413298] flags: 0x100000000008100(slab|head)
[   42.413729] raw: 0100000000008100 0000000000000000 0000000000000000 00000001800c000c
[   42.414387] raw: ffffea00002a9500 0000000900000007 ffff88000c401280 0000000000000000
[   42.415074] page dumped because: kasan: bad access detected
[   42.415604]
[   42.415757] Memory state around the buggy address:
[   42.416222]  ffff88000969e880: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   42.416904]  ffff88000969e900: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
[   42.417591] >ffff88000969e980: fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc fc
[   42.418273]                    ^
[   42.418588]  ffff88000969ea00: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[   42.419273]  ffff88000969ea80: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
[   42.419882] ==================================================================

Reported-by: Andrey Konovalov <andreyknvl@google.com>
Signed-off-by: Craig Gallek <kraig@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>