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Jakub Sitnicki 035ff358f2 net: Generate reuseport group ID on group creation 
Commit 736b46027e ("net: Add ID (if needed) to sock_reuseport and expose
reuseport_lock") has introduced lazy generation of reuseport group IDs that
survive group resize.

By comparing the identifier we check if BPF reuseport program is not trying
to select a socket from a BPF map that belongs to a different reuseport
group than the one the packet is for.

Because SOCKARRAY used to be the only BPF map type that can be used with
reuseport BPF, it was possible to delay the generation of reuseport group
ID until a socket from the group was inserted into BPF map for the first
time.

Now that SOCK{MAP,HASH} can be used with reuseport BPF we have two options,
either generate the reuseport ID on map update, like SOCKARRAY does, or
allocate an ID from the start when reuseport group gets created.

This patch takes the latter approach to keep sockmap free of calls into
reuseport code. This streamlines the reuseport_id access as its lifetime
now matches the longevity of reuseport object.

The cost of this simplification, however, is that we allocate reuseport IDs
for all SO_REUSEPORT users. Even those that don't use SOCKARRAY in their
setups. With the way identifiers are currently generated, we can have at
most S32_MAX reuseport groups, which hopefully is sufficient. If we ever
get close to the limit, we can switch an u64 counter like sk_cookie.

Another change is that we now always call into SOCKARRAY logic to unlink
the socket from the map when unhashing or closing the socket. Previously we
did it only when at least one socket from the group was in a BPF map.

It is worth noting that this doesn't conflict with sockmap tear-down in
case a socket is in a SOCK{MAP,HASH} and belongs to a reuseport
group. sockmap tear-down happens first:

  prot->unhash
  `- tcp_bpf_unhash
     |- tcp_bpf_remove
     |  `- while (sk_psock_link_pop(psock))
     |     `- sk_psock_unlink
     |        `- sock_map_delete_from_link
     |           `- __sock_map_delete
     |              `- sock_map_unref
     |                 `- sk_psock_put
     |                    `- sk_psock_drop
     |                       `- rcu_assign_sk_user_data(sk, NULL)
     `- inet_unhash
        `- reuseport_detach_sock
           `- bpf_sk_reuseport_detach
              `- WRITE_ONCE(sk->sk_user_data, NULL)

Suggested-by: Martin Lau <kafai@fb.com>
Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200218171023.844439-10-jakub@cloudflare.com
2020-02-21 22:29:45 +01:00
arch arm64: time: Replace <linux/clk-provider.h> by <linux/of_clk.h> 2020-02-12 17:26:38 +00:00
block block-5.6-2020-02-05 2020-02-06 06:15:23 +00:00
certs certs: Add wrapper function to check blacklisted binary hash 2019-11-12 12:25:50 +11:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2020-02-13 14:17:39 -08:00
Documentation docs/bpf: Update bpf development Q/A file 2020-02-20 18:05:37 -08:00
drivers net: ena: remove set but not used variable 'hash_key' 2020-02-17 22:32:50 -08:00
fs dax fixes 5.6-rc1 2020-02-11 16:52:08 -08:00
include net: Generate reuseport group ID on group creation 2020-02-21 22:29:45 +01:00
init Various fixes: 2020-02-11 16:39:18 -08:00
ipc proc: convert everything to "struct proc_ops" 2020-02-04 03:05:26 +00:00
kernel net: Generate reuseport group ID on group creation 2020-02-21 22:29:45 +01:00
lib lib: objagg: Replace zero-length arrays with flexible-array member 2020-02-16 18:33:00 -08:00
LICENSES
mm Merge branch 'merge.nfs-fs_parse.1' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2020-02-08 13:26:41 -08:00
net net: Generate reuseport group ID on group creation 2020-02-21 22:29:45 +01:00
samples Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
scripts kbuild: fix mismatch between .version and include/generated/compile.h 2020-02-11 05:18:40 +09:00
security selinux/stable-5.6 PR 20200210 2020-02-10 16:51:35 -08:00
sound ALSA: pcm: Fix double hw_free calls 2020-02-13 16:30:22 +01:00
tools bpf, sockmap: Allow inserting listening TCP sockets into sockmap 2020-02-21 22:29:45 +01:00
usr Kbuild updates for v5.6 (2nd) 2020-02-09 16:05:50 -08:00
virt KVM: fix overflow of zero page refcount with ksm running 2020-02-05 15:27:46 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2019-08-31 10:00:51 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore modpost: dump missing namespaces into a single modules.nsdeps file 2019-11-11 20:10:01 +09:00
.mailmap A handful of small documentation fixes that wandered in. 2020-02-07 13:03:10 -08:00
COPYING
CREDITS open: introduce openat2(2) syscall 2020-01-18 09:19:18 -05:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig docs: kbuild: convert docs to ReST and rename to *.rst 2019-06-14 14:21:21 -06:00
MAINTAINERS MAINTAINERS: Sort entries in database for GPIO 2020-02-10 10:55:18 +01:00
Makefile Linux 5.6-rc1 2020-02-09 16:08:48 -08:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.