sk_psock_verdict_recv() clones the skb and uses the clone
afterward, so udp_read_sock() should free the skb after using
it, regardless of error or not.

This fixes a real kmemleak.

Fixes: d7f57118 ("udp: Implement ->read_sock() for sockmap")
Signed-off-by: NCong Wang <cong.wang@bytedance.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Acked-by: NJakub Sitnicki <jakub@cloudflare.com>
Link: https://lore.kernel.org/bpf/20210615021342.7416-4-xiyou.wangcong@gmail.com

Kaustubh reported and diagnosed a panic in udp_lib_lookup().
The root cause is udp_abort() racing with close(). Both
racing functions acquire the socket lock, but udp{v6}_destroy_sock()
release it before performing destructive actions.

We can't easily extend the socket lock scope to avoid the race,
instead use the SOCK_DEAD flag to prevent udp_abort from doing
any action when the critical race happens.
Diagnosed-and-tested-by: NKaustubh Pandey <kapandey@codeaurora.org>
Fixes: 5d77dca8 ("net: diag: support SOCK_DESTROY for UDP sockets")
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Support for UDP_GRO was added in the past but the implementation for
getsockopt was missed which did lead to an error when we tried to
retrieve the setting for UDP_GRO. This patch adds the missing switch
case for UDP_GRO

Fixes: e20cf8d3 ("udp: implement GRO for plain UDP sockets.")
Signed-off-by: NNorman Maurer <norman_maurer@apple.com>
Reviewed-by: NDavid Ahern <dsahern@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This is similar to tcp_read_sock(), except we do not need
to worry about connections, we just need to retrieve skb
from UDP receive queue.

Note, the return value of ->read_sock() is unused in
sk_psock_verdict_data_ready(), and UDP still does not
support splice() due to lack of ->splice_read(), so users
can not reach udp_read_sock() directly.
Signed-off-by: NCong Wang <cong.wang@bytedance.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20210331023237.41094-12-xiyou.wangcong@gmail.com

Currently sockmap calls into each protocol to update the struct
proto and replace it. This certainly won't work when the protocol
is implemented as a module, for example, AF_UNIX.

Introduce a new ops sk->sk_prot->psock_update_sk_prot(), so each
protocol can implement its own way to replace the struct proto.
This also helps get rid of symbol dependencies on CONFIG_INET.
Signed-off-by: NCong Wang <cong.wang@bytedance.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20210331023237.41094-11-xiyou.wangcong@gmail.com

Currently the UDP protocol delivers GSO_FRAGLIST packets to
the sockets without the expected segmentation.

This change addresses the issue introducing and maintaining
a couple of new fields to explicitly accept SKB_GSO_UDP_L4
or GSO_FRAGLIST packets. Additionally updates  udp_unexpected_gso()
accordingly.

UDP sockets enabling UDP_GRO stil keep accept_udp_fraglist
zeroed.

v1 -> v2:
 - use 2 bits instead of a whole GSO bitmask (Willem)

Fixes: 9fd1ff5d ("udp: Support UDP fraglist GRO/GSO.")
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Reviewed-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When UDP packets generated locally by a socket with UDP_SEGMENT
traverse the following path:

UDP tunnel(xmit) -> veth (segmentation) -> veth (gro) ->
	UDP tunnel (rx) -> UDP socket (no UDP_GRO)

ip_summed will be set to CHECKSUM_PARTIAL at creation time and
such checksum mode will be preserved in the above path up to the
UDP tunnel receive code where we have:

 __iptunnel_pull_header() -> skb_pull_rcsum() ->
skb_postpull_rcsum() -> __skb_postpull_rcsum()

The latter will convert the skb to CHECKSUM_NONE.

The UDP GSO packet will be later segmented as part of the rx socket
receive operation, and will present a CHECKSUM_NONE after segmentation.

Additionally the segmented packets UDP CB still refers to the original
GSO packet len. Overall that causes unexpected/wrong csum validation
errors later in the UDP receive path.

We could possibly address the issue with some additional checks and
csum mangling in the UDP tunnel code. Since the issue affects only
this UDP receive slow path, let's set a suitable csum status there.

Note that SKB_GSO_UDP_L4 or SKB_GSO_FRAGLIST packets lacking an UDP
encapsulation present a valid checksum when landing to udp_queue_rcv_skb(),
as the UDP checksum has been validated by the GRO engine.

v2 -> v3:
 - even more verbose commit message and comments

v1 -> v2:
 - restrict the csum update to the packets strictly needing them
 - hopefully clarify the commit message and code comments
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Reviewed-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When enabling encap for a ipv6 socket without udp_encap_needed_key
increased, UDP GRO won't work for v4 mapped v6 address packets as
sk will be NULL in udp4_gro_receive().

This patch is to enable it by increasing udp_encap_needed_key for
v6 sockets in udp_tunnel_encap_enable(), and correspondingly
decrease udp_encap_needed_key in udpv6_destroy_sock().

v1->v2:
  - add udp_encap_disable() and export it.
v2->v3:
  - add the change for rxrpc and bareudp into one patch, as Alex
    suggested.
v3->v4:
  - move rxrpc part to another patch.
Acked-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

When we attach any cgroup hook, the rest (even if unused/unattached) start
to contribute small overhead. In particular, the one we want to avoid is
__cgroup_bpf_run_filter_skb which does two redirections to get to
the cgroup and pushes/pulls skb.

Let's split cgroup_bpf_enabled to be per-attach to make sure
only used attach types trigger.

I've dropped some existing high-level cgroup_bpf_enabled in some
places because BPF_PROG_CGROUP_XXX_RUN macros usually have another
cgroup_bpf_enabled check.

I also had to copy-paste BPF_CGROUP_RUN_SA_PROG_LOCK for
GETPEERNAME/GETSOCKNAME because type for cgroup_bpf_enabled[type]
has to be constant and known at compile time.
Signed-off-by: NStanislav Fomichev <sdf@google.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NSong Liu <songliubraving@fb.com>
Link: https://lore.kernel.org/bpf/20210115163501.805133-4-sdf@google.com

udp_v4_early_demux() is the only function that calls
ip_mc_validate_source() with a TOS that hasn't been masked with
IPTOS_RT_MASK.

This results in different behaviours for incoming multicast UDPv4
packets, depending on if ip_mc_validate_source() is called from the
early-demux path (udp_v4_early_demux) or from the regular input path
(ip_route_input_noref).

ECN would normally not be used with UDP multicast packets, so the
practical consequences should be limited on that side. However,
IPTOS_RT_MASK is used to also masks the TOS' high order bits, to align
with the non-early-demux path behaviour.

Reproducer:

  Setup two netns, connected with veth:
  $ ip netns add ns0
  $ ip netns add ns1
  $ ip -netns ns0 link set dev lo up
  $ ip -netns ns1 link set dev lo up
  $ ip link add name veth01 netns ns0 type veth peer name veth10 netns ns1
  $ ip -netns ns0 link set dev veth01 up
  $ ip -netns ns1 link set dev veth10 up
  $ ip -netns ns0 address add 192.0.2.10 peer 192.0.2.11/32 dev veth01
  $ ip -netns ns1 address add 192.0.2.11 peer 192.0.2.10/32 dev veth10

  In ns0, add route to multicast address 224.0.2.0/24 using source
  address 198.51.100.10:
  $ ip -netns ns0 address add 198.51.100.10/32 dev lo
  $ ip -netns ns0 route add 224.0.2.0/24 dev veth01 src 198.51.100.10

  In ns1, define route to 198.51.100.10, only for packets with TOS 4:
  $ ip -netns ns1 route add 198.51.100.10/32 tos 4 dev veth10

  Also activate rp_filter in ns1, so that incoming packets not matching
  the above route get dropped:
  $ ip netns exec ns1 sysctl -wq net.ipv4.conf.veth10.rp_filter=1

  Now try to receive packets on 224.0.2.11:
  $ ip netns exec ns1 socat UDP-RECVFROM:1111,ip-add-membership=224.0.2.11:veth10,ignoreeof -

  In ns0, send packet to 224.0.2.11 with TOS 4 and ECT(0) (that is,
  tos 6 for socat):
  $ echo test0 | ip netns exec ns0 socat - UDP-DATAGRAM:224.0.2.11:1111,bind=:1111,tos=6

  The "test0" message is properly received by socat in ns1, because
  early-demux has no cached dst to use, so source address validation
  is done by ip_route_input_mc(), which receives a TOS that has the
  ECN bits masked.

  Now send another packet to 224.0.2.11, still with TOS 4 and ECT(0):
  $ echo test1 | ip netns exec ns0 socat - UDP-DATAGRAM:224.0.2.11:1111,bind=:1111,tos=6

  The "test1" message isn't received by socat in ns1, because, now,
  early-demux has a cached dst to use and calls ip_mc_validate_source()
  immediately, without masking the ECN bits.

Fixes: bc044e8d ("udp: perform source validation for mcast early demux")
Signed-off-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

Guillaume noticed that: for segments udp_queue_rcv_one_skb() returns the
proto, and it should pass "ret" unmodified to ip_protocol_deliver_rcu().
Otherwize, with a negtive value passed, it will underflow inet_protos.

This can be reproduced with IPIP FOU:

  # ip fou add port 5555 ipproto 4
  # ethtool -K eth1 rx-gro-list on

Fixes: cf329aa4 ("udp: cope with UDP GRO packet misdirection")
Reported-by: NGuillaume Nault <gnault@redhat.com>
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As pointed out by Herbert in a recent related patch, the LSM hooks do
not have the necessary address family information to use the flowi
struct safely.  As none of the LSMs currently use any of the protocol
specific flowi information, replace the flowi pointers with pointers
to the address family independent flowi_common struct.
Reported-by: NHerbert Xu <herbert@gondor.apana.org.au>
Acked-by: NJames Morris <jamorris@linux.microsoft.com>
Signed-off-by: NPaul Moore <paul@paul-moore.com>

These functions do not need to be exported.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/20201113113553.3411756-1-eric.dumazet@gmail.comSigned-off-by: NJakub Kicinski <kuba@kernel.org>

The skb is needed only to fetch the keys for the lookup.

Both functions are used from GRO stack, we do not want
accidental modification of the skb.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Acked-by: NAlexander Lobakin <alobakin@pm.me>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

The initialization for 'err' with 0 is redundant and can be removed,
as it is updated by ip_send_skb and not used before that.
Signed-off-by: NMenglong Dong <dong.menglong@zte.com.cn>
Link: https://lore.kernel.org/r/1604644960-48378-4-git-send-email-dong.menglong@zte.com.cnSigned-off-by: NJakub Kicinski <kuba@kernel.org>

When udp_memory_allocated is at the limit, __udp_enqueue_schedule_skb
will return a -ENOBUFS, and skb will be dropped in __udp_queue_rcv_skb
without any counters being done. It's hard to find out what happened
once this happen.

So we introduce a UDP_MIB_MEMERRORS to do this job. Well, this change
looks friendly to the existing users, such as netstat:

$ netstat -u -s
Udp:
    0 packets received
    639 packets to unknown port received.
    158689 packet receive errors
    180022 packets sent
    RcvbufErrors: 20930
    MemErrors: 137759
UdpLite:
IpExt:
    InOctets: 257426235
    OutOctets: 257460598
    InNoECTPkts: 181177

v2:
- Fix some alignment problems
Signed-off-by: NMenglong Dong <dong.menglong@zte.com.cn>
Link: https://lore.kernel.org/r/1604627354-43207-1-git-send-email-dong.menglong@zte.com.cnSigned-off-by: NJakub Kicinski <kuba@kernel.org>

There is a chance that __udp4/6_lib_lookup() returns a udp encap
sock in __udp_lib_err(), like the udp encap listening sock may
use the same port as remote encap port, in which case it should
go to __udp4/6_lib_err_encap() for more validation before
processing the icmp packet.

This patch is to check encap_type in __udp_lib_err() for the
further validation for a encap sock.
Signed-off-by: NXin Long <lucien.xin@gmail.com>
Acked-by: NMarcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: NJakub Kicinski <kuba@kernel.org>

Drop duplicate words in comments in net/ipv4/.
Signed-off-by: NRandy Dunlap <rdunlap@infradead.org>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

When BPF sk lookup invokes reuseport handling for the selected socket, it
should ignore the fact that reuseport group can contain connected UDP
sockets. With BPF sk lookup this is not relevant as we are not scoring
sockets to find the best match, which might be a connected UDP socket.

Fix it by unconditionally accepting the socket selected by reuseport.

This fixes the following two failures reported by test_progs.

  # ./test_progs -t sk_lookup
  ...
  #73/14 UDP IPv4 redir and reuseport with conns:FAIL
  ...
  #73/20 UDP IPv6 redir and reuseport with conns:FAIL
  ...

Fixes: a57066b1 ("Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net")
Reported-by: NAlexei Starovoitov <alexei.starovoitov@gmail.com>
Signed-off-by: NJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: NDaniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200726120228.1414348-1-jakub@cloudflare.com

This patch refactored target bpf_iter_init_seq_priv_t callback
function to accept additional information. This will be needed
in later patches for map element targets since a particular
map should be passed to traverse elements for that particular
map. In the future, other information may be passed to target
as well, e.g., pid, cgroup id, etc. to customize the iterator.
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184110.590156-1-yhs@fb.com

There is no functionality change for this patch.
Struct bpf_iter_reg is used to register a bpf_iter target,
which includes information for both prog_load, link_create
and seq_file creation.

This patch puts fields related seq_file creation into
a different structure. This will be useful for map
elements iterator where one iterator covers different
map types and different map types may have different
seq_ops, init/fini private_data function and
private_data size.
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200723184109.590030-1-yhs@fb.com

Rework the remaining setsockopt code to pass a sockptr_t instead of a
plain user pointer.  This removes the last remaining set_fs(KERNEL_DS)
outside of architecture specific code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Acked-by: Stefan Schmidt <stefan@datenfreihafen.org> [ieee802154]
Acked-by: NMatthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Pass a sockptr_t to prepare for set_fs-less handling of the kernel
pointer from bpf-cgroup.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

We can't use IS_UDPLITE to replace udp_sk->pcflag when UDPLITE_RECV_CC is
checked.

Fixes: b2bf1e26 ("[UDP]: Clean up for IS_UDPLITE macro")
Signed-off-by: NMiaohe Lin <linmiaohe@huawei.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Currently, SO_REUSEPORT does not work well if connected sockets are in a
UDP reuseport group.

Then reuseport_has_conns() returns true and the result of
reuseport_select_sock() is discarded. Also, unconnected sockets have the
same score, hence only does the first unconnected socket in udp_hslot
always receive all packets sent to unconnected sockets.

So, the result of reuseport_select_sock() should be used for load
balancing.

The noteworthy point is that the unconnected sockets placed after
connected sockets in sock_reuseport.socks will receive more packets than
others because of the algorithm in reuseport_select_sock().

    index | connected | reciprocal_scale | result
    ---------------------------------------------
    0     | no        | 20%              | 40%
    1     | no        | 20%              | 20%
    2     | yes       | 20%              | 0%
    3     | no        | 20%              | 40%
    4     | yes       | 20%              | 0%

If most of the sockets are connected, this can be a problem, but it still
works better than now.

Fixes: acdcecc6 ("udp: correct reuseport selection with connected sockets")
CC: Willem de Bruijn <willemb@google.com>
Reviewed-by: NBenjamin Herrenschmidt <benh@amazon.com>
Signed-off-by: NKuniyuki Iwashima <kuniyu@amazon.co.jp>
Acked-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

One additional field btf_id is added to struct
bpf_ctx_arg_aux to store the precomputed btf_ids.
The btf_id is computed at build time with
BTF_ID_LIST or BTF_ID_LIST_GLOBAL macro definitions.
All existing bpf iterators are changed to used
pre-compute btf_ids.
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200720163403.1393551-1-yhs@fb.com

Handle the few cases that need special treatment in-line using
in_compat_syscall().
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Following INET/TCP socket lookup changes, modify UDP socket lookup to let
BPF program select a receiving socket before searching for a socket by
destination address and port as usual.

Lookup of connected sockets that match packet 4-tuple is unaffected by this
change. BPF program runs, and potentially overrides the lookup result, only
if a 4-tuple match was not found.
Suggested-by: NMarek Majkowski <marek@cloudflare.com>
Signed-off-by: NJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-9-jakub@cloudflare.com

Prepare for calling into reuseport from __udp4_lib_lookup as well.
Signed-off-by: NJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NAndrii Nakryiko <andriin@fb.com>
Link: https://lore.kernel.org/bpf/20200717103536.397595-8-jakub@cloudflare.com

Simple fixes which require no deep knowledge of the code.

Cc: Paul Moore <paul@paul-moore.com>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
Cc: Eric Dumazet <edumazet@google.com>
Signed-off-by: NAndrew Lunn <andrew@lunn.ch>
Acked-by: NPaul Moore <paul@paul-moore.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The bpf iterator for udp is implemented. Both udp4 and udp6
sockets will be traversed. It is up to bpf program to
filter for udp4 or udp6 only, or both families of sockets.
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230813.3988404-1-yhs@fb.com

Similar to tcp_iter_state, a new field bpf_seq_afinfo is
added to udp_iter_state to provide bpf udp iterator
afinfo.

This does not change /proc/net/{udp, udp6} behavior. But
it enables bpf iterator to avoid get afinfo from PDE_DATA
and iterate through all udp and udp6 sockets in one pass.
Signed-off-by: NYonghong Song <yhs@fb.com>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200623230812.3988347-1-yhs@fb.com

This patch adds support for encapsulation of ESP over UDPv6. The code
is very similar to the IPv4 encapsulation implementation, and allows
to easily add espintcp on IPv6 as a follow-up.
Signed-off-by: NSabrina Dubroca <sd@queasysnail.net>
Signed-off-by: NSteffen Klassert <steffen.klassert@secunet.com>

Refactor the UDP/TCP handlers slightly to allow skb_steal_sock() to make
the determination of whether the socket is reference counted in the case
where it is prefetched by earlier logic such as early_demux.
Signed-off-by: NJoe Stringer <joe@wand.net.nz>
Signed-off-by: NAlexei Starovoitov <ast@kernel.org>
Acked-by: NMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200329225342.16317-3-joe@wand.net.nz

The SKB_SGO_CB_OFFSET should be SKB_GSO_CB_OFFSET which means the
offset of the GSO in skb cb. This patch fixes the typo.

Fixes: 9207f9d4 ("net: preserve IP control block during GSO segmentation")
Signed-off-by: NCambda Zhu <cambda@linux.alibaba.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

Convert the various uses of fallthrough comments to fallthrough;

Done via script
Link: https://lore.kernel.org/lkml/b56602fcf79f849e733e7b521bb0e17895d390fa.1582230379.git.joe@perches.com/

And by hand:

net/ipv6/ip6_fib.c has a fallthrough comment outside of an #ifdef block
that causes gcc to emit a warning if converted in-place.

So move the new fallthrough; inside the containing #ifdef/#endif too.
Signed-off-by: NJoe Perches <joe@perches.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

The only users for such argument are the UDP protocol and the UNIX
socket family. We can safely reclaim the accounted memory directly
from the UDP code and, after the previous patch, we can do scm
stats accounting outside the datagram helpers.

Overall this cleans up a bit some datagram-related helpers, and
avoids an indirect call per packet in the UDP receive path.

v1 -> v2:
 - call scm_stat_del() only when not peeking - Kirill
 - fix build issue with CONFIG_INET_ESPINTCP
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Reviewed-by: NKirill Tkhai <ktkhai@virtuozzo.com>
Reviewed-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

As of the below commit, udp sockets bound to a specific address can
coexist with one bound to the any addr for the same port.

The commit also phased out the use of socket hashing based only on
port (hslot), in favor of always hashing on {addr, port} (hslot2).

The change broke the following behavior with disconnect (AF_UNSPEC):

    server binds to 0.0.0.0:1337
    server connects to 127.0.0.1:80
    server disconnects
    client connects to 127.0.0.1:1337
    client sends "hello"
    server reads "hello"	// times out, packet did not find sk

On connect the server acquires a specific source addr suitable for
routing to its destination. On disconnect it reverts to the any addr.

The connect call triggers a rehash to a different hslot2. On
disconnect, add the same to return to the original hslot2.

Skip this step if the socket is going to be unhashed completely.

Fixes: 4cdeeee9 ("net: udp: prefer listeners bound to an address")
Reported-by: NPavel Roskin <plroskin@gmail.com>
Signed-off-by: NWillem de Bruijn <willemb@google.com>
Reviewed-by: NEric Dumazet <edumazet@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This reverts commit 0d4a6608.

Williem reported that after commit 0d4a6608 ("udp: do rmem bulk
free even if the rx sk queue is empty") the memory allocated by
an almost idle system with many UDP sockets can grow a lot.

For stable kernel keep the solution as simple as possible and revert
the offending commit.
Reported-by: NWillem de Bruijn <willemdebruijn.kernel@gmail.com>
Diagnosed-by: NEric Dumazet <eric.dumazet@gmail.com>
Fixes: 0d4a6608 ("udp: do rmem bulk free even if the rx sk queue is empty")
Signed-off-by: NPaolo Abeni <pabeni@redhat.com>
Acked-by: NWillem de Bruijn <willemb@google.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

This is a straight-forward conversion case for the new function,
iterating over the return value from udp_rcv_segment, which actually is
a wrapper around skb_gso_segment.
Signed-off-by: NJason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>