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'''Multi-Channel'''
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==== ====[plain]

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<<<point-cut-1280.jpg,height=.8\textheight>>>
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==== Multi-Channel - General ====

+<2->{
<[block]{multiple transport connections in one SMB(3) session}
* '''channel''': transport connection bound to a session
* client decides which connections to bind and to use
* session is valid as long as at least one channel is intact
[block]>
}

+<3->{
<[block]{two purposes}
# increase throughput:
#* use multiple connections of same type
# improve fault tolerance:
#* channel failure: replay/retry detection
%%#* session is valid as long as one channel is still intact
[block]>
}

==== Multi-Channel - General ====

<[block]{use case: channels of different type/quality}
* use only the channels of best quality
* fall back to inferior channels if superior ones fail
* e.g.: laptop switching between WiFi and LAN (?)
[block]>

==== Multi-Channel - Windows/Protocol ====

# establish initial session on TCP connection
# find interfaces with interface discovery: \\ %
@FSCTL\_QUERY\_NETWORK\_INTERFACE\_INFO@
# bind additional TCP (or later RDMA) connection (channel) to established SMB3 session (''session bind'')
# Windows: uses connections of same (and best) quality
# Windows: binds only to a single node
# replay / retry mechanisms, sequence numbers


==== ====[plain]

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<<<samba-kisses-better-selection.jpg,height=.8\textheight>>>
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==== Multi-Channel $\in$ Samba ====

<[block]{samba/smbd: multi-process}
* '''Originally:''' process $\Leftrightarrow$ TCP connection
*<0> '''Idea:''' transfer new TCP connection to existing smbd
*<0> '''How?''' ==> use fd-passing (sendmsg/recvmsg)
*<0> '''When?'''
** ''Natural choice'': at SessionSetup (Bind)
** !Idea!: as early as possible, based on ClientGUID \\ %
==> per ClientGUID single process model
%%*<0> !But!: This may not work! \frownie
[block]>

==== Multi-Channel $\in$ Samba ====

<[center]
<<<smb3-mc-daemons-n1.png,width=.9\textwidth>>>
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==== Multi-Channel $\in$ Samba ====

<[block]{samba/smbd: multi-process}
* '''Originally:''' process $\Leftrightarrow$ TCP connection
* '''Idea:''' transfer new TCP connection to existing smbd
*<0> '''How?''' ==> use fd-passing (sendmsg/recvmsg)
*<0> '''When?'''
** ''Natural choice'': at SessionSetup (Bind)
** !Idea!: as early as possible, based on ClientGUID \\ %
==> per ClientGUID single process model
%%*<0> !But!: There may be problems! ... \frownie
[block]>


==== Multi-Channel $\in$ Samba ====

-<1>{
<[center]
<<<smb3-mc-daemons-n1a.png,width=.9\textwidth>>>
[center]>
}

-<2>{
<[center]
<<<smb3-mc-daemons-n2.png,width=.9\textwidth>>>
[center]>
}

-<3>{
<[center]
<<<smb3-mc-daemons-n3.png,width=.9\textwidth>>>
[center]>
}


==== Multi-Channel $\in$ Samba ====

<[block]{samba/smbd: multi-process}
* '''Originally:''' process $\Leftrightarrow$ TCP connection
* '''Idea:''' transfer new TCP connection to existing smbd
* '''How?''' ==> use fd-passing (sendmsg/recvmsg)
*<2-> '''When?'''
** ''Natural choice'': at SessionSetup (Bind)
** !Idea!: as early as possible, based on ClientGUID \\ %
==> per ClientGUID single process model
%%*<0> !But!: There may be problems! ... \frownie
[block]>


==== Multi-Channel $\in$ Samba : pass by ClientGUID ====

<[center]
%%<<<smb3-mc-samba_exp.png,height=.9\textheight>>>
<<<smb3-mc-samba.png,height=.9\textheight>>>
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==== Multi-Channel $\in$ Samba : pass by ClientGUID ====

<[block]{Wait a minute - what about performance?}
* Single process...
* But we use short-lived worker-pthreads for I/O ops! \\ %
==> using multiple CPUs
* Benchmarks and tunings in progress
[block]>

%%%% ==== Multi-Channel $\in$ Samba ====
%%%% 
%%%% <[block]{samba/smbd: multi-process}
%%%% * '''Orignally:''' process $\Leftrightarrow$ TCP connection
%%%% * '''Idea:''' transfer new TCP connection to existing smbd
%%%% * '''How?''' ==> use fd-passing (sendmsg/recvmsg)
%%%% * '''When?'''
%%%% ** ''Natural choice'': at SessionSetup (Bind)
%%%% ** ''Idea'': as early as possible, based on ClientGUID \\ %
%%%% ==> per ClientGUID single process model
%%%% * !But!: There may be problems! ... \frownie
%%%% [block]>
%%%% 
%%%% 
%%%% ==== The Relevance of the ClientGUID ====
%%%% 
%%%% +<1->{
%%%% <[block]{Assumption was:}
%%%% * All channels in a session have the same ClientGUID
%%%% * The server enforces this
%%%% [block]>
%%%% }
%%%% 
%%%% +<2->{
%%%% <[block]{Evidence from [MS-SMB2]:}
%%%% * 3.3.5.9 Receiving an SMB2 CREATE Request:
%%%% ** sets Open.ClientGuid to Connection.ClientGuid
%%%% ** replay detection checks \\ %
%%%% Open.ClientGuid == Connection.ClientGuid
%%%% * 3.3.5.9.7/12 Durable (v2) Reconnect Create Context:
%%%% ** check Open.ClientGuid == Connection.ClientGuid
%%%% [block]>
%%%% }
%%%% 
%%%% +<3->{
%%%% <[block]{The truth is...}
%%%% The Windows server does not enforce it!
%%%% [block]>
%%%% }
%%%% 
%%%% 
%%%% ==== The Relevance of the ClientGUID ====
%%%% 
%%%% <[block]{Windows behaviour according to MS}
%%%% * The server does NOT enforce same ClientGUID in a session.
%%%% * But clients can be expected to do it.
%%%% * But it is not explicitly documented like this.
%%%% [block]>
%%%% 
%%%% +<2->{
%%%% <[block]{The good news:}
%%%% There will be documentation notes:
%%%% * Things will not work as expected when clients behave differently.
%%%% * It is OK for a server to enforce equality of ClientGUID within session.
%%%% [block]>
%%%% }
%%%% 
%%%% ==== More digression on ClientGUID : Leases ====
%%%% 
%%%% <[block]{According to [MS-SMB2]}
%%%% * Server Global data Structures:
%%%% ** GlobalLeaseTableList indexed by ClientGuid (3.3.1.5)
%%%% *** LeaseTable indexed by LeaseKey (3.3.1.11)
%%%% * Requesting a lease (3.3.1.4):
%%%% ** Object store takes an abstract ClientLeaseId
%%%% *** Win7: combination of ClientGuid and LeaseKey
%%%% *** Win8+: LeaseKey
%%%% * Object store indicates a lease break (3.3.4.7):
%%%% ** smb server uses ClientGuid and LeaseKey given by ObjectStore
%%%% 
%%%%  ==> !Inconsistent\! -- What to do?!
%%%% [block]>
%%%% 
%%%% 
%%%% ==== Multi-Channel $\in$ Samba : pass by SessionID (plan B) ====
%%%% 
%%%% <[center]
%%%% <<<smb3-mc-samba-v2.png,height=.9\textheight>>>
%%%% [center]>


==== Multi-Channel $\in$ Samba : Status ====

+<2->{
# messaging rewrite using unix dgm sockets with sendmsg [DONE,4.2]
# add fd-passing to messaging [DONE,4.2]
# preparations in internal structures [DONE,4.2--4.4]
# prepare code to cope with multiple channels [DONE,4.4]
# implement smbd message to pass a tcp socket [DONE,4.4]
# transfer connection in Negotiate (by ClientGUID) [DONE,4.4]
# implement session bind [DONE,4.4]
# implement channel sequence numbers [DONE,4.4]
# implement interface discovery [DONE(linux/conf),4.4]
# implement test cases [WIP(isn't it always?... $\smiley$)]
# implement fd-passing in socket-wrapper [WIP]
# implement lease break replay [TODO]
}

==== Multi-Channel $\in$ Samba : How we got there ====

* Based on preparations in 4.2 and earlier (200+ patches)
** Patches by Stefan Metzmacher, Michael Adam, Volker Lendecke, Anubhav Rakshit
* Since Summer 2015:
** Polishing of large parts of massively WIP branch
** Added new code (create replay, interface detection)
** Result merged in units. Overall some ~130 patches.
** Patches by:
*** Michael Adam
*** Stefan Metzmacher
*** Günther Deschner
*** Anoop C S
*** Anubhav Rakshit
* Just made it as experimental feature into Samba 4.4


==== ====[plain]

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<<<instructions-1-1280.jpg,height=.8\textwidth>>>
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==== Multi-Channel $\in$ Samba : How to enable it ====

<[block]{smb.conf}
<[code]
\[global\]
...
server multi channel support = yes
...
[code]>
[block]>

%%==== Multi-Channel $\in$ Samba : Details from @smbXsrv.idl@ ====
%%%%==== @MSG\_SMBXSRV\_CONNECTION\_PASS@ ====
%%
%%<[block]{for @MSG\_SMBXSRV\_CONNECTION\_PASS@}
%%<[code]
%%typedef struct {
%%    NTTIME                 initial_connect_time;
%%    GUID                   client_guid;
%%    hyper                  seq_low;
%%    DATA_BLOB              negotiate_request;
%%} smbXsrv_connection_pass0;
%%[code]>
%%[block]>
%%
%%%%==== Internal Structures (@smbXsrv.idl@) ====
%%==== Multi-Channel $\in$ Samba : Details from @smbXsrv.idl@ ====
%%
%%
%%<[block]{layering before}
%%<[code]
%%smbXsrv_session
%%  ->smbXsrv_connection
%%[code]>
%%[block]>
%%
%%<[block]{layering now}
%%<[code]
%%smbXsrv_session
%%  ->smbXsrv_client
%%    ->smbXsrv_connections
%%[code]>
%%[block]>


%%% ==== Multi-Channel $\in$ Samba : Status ====
%%% 
%%% <[block]{WIP code}
%%% * @git://git.samba.org/obnox/samba/samba-obnox.git@
%%% * branch: @master-multi-channel-obnox@
%%% [block]>


==== Multi-Channel $\in$ Samba: TODOs ====

*<2-> teach socket\_wrapper fd-passing ( ==> selftest...)
*<3-> Replay lease breaks upon channel failure (server $\rightarrow$ client) \\ %
_red_DANGER!_
*<4-> clustering integration (CTDB) \\ %
_red_DANGER!_

==== Multi-Channel $\in$ Samba : Clustering/CTDB ====

+<2->{
<[block]{Special considerations}
* channels of one session only to one node !
* do not bind connections to CTDB public IPs (can move)!
* problem: CTDB clustering transparent to SMB clients...
[block]>
}

==== ====[plain]

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==== Multi-Channel $\in$ Samba : Clustering/CTDB ====

+<2->{
<[block]{Plan for integration}
* establish blacklist of addresses (e.g. CTDB public IPs)
* add static IPs to public interfaces
* optionally establish whitelist (interfaces ...)
* ==> list of allowed addresses
* only publish allowed addresses in interfaces info ioctl
* only give more than one address in interface info when asked via an allowed address
* deny session bind on non-allowed address
[block]>
}

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==== ====[plain]

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Multi-Channel Demo
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