[PATCH net-next v4 00/11] splice, net: Rewrite splice-to-socket, fix SPLICE_F_MORE and handle MSG_SPLICE_PAGES in AF_TLS

[David Howells]

Here are patches to do the following:

 (1) Block MSG_SENDPAGE_* flags from leaking into ->sendmsg() from
     userspace, whilst allowing splice_to_socket() to pass them in.

 (2) Allow MSG_SPLICE_PAGES to be passed into tls_*_sendmsg().  Until
     support is added, it will be ignored and a splice-driven sendmsg()
     will be treated like a normal sendmsg().  TCP, UDP, AF_UNIX and
     Chelsio-TLS already handle the flag in net-next.

 (3) Replace a chain of functions to splice-to-sendpage with a single
     function to splice via sendmsg() with MSG_SPLICE_PAGES.  This allows a
     bunch of pages to be spliced from a pipe in a single call using a
     bio_vec[] and pushes the main processing loop down into the bowels of
     the protocol driver rather than repeatedly calling in with a page at a
     time.

 (4) Provide a ->splice_eof() op[2] that allows splice to signal to its
     output that the input observed a premature EOF and that the caller
     didn't flag SPLICE_F_MORE, thereby allowing a corked socket to be
     flushed.  This attempts to maintain the current behaviour.  It is also
     not called if we didn't manage to read any data and so didn't called
     the actor function.

     This needs routing though several layers to get it down to the network
     protocol.

     [!] Note that I chose not to pass in any flags - I'm not sure it's
     	 particularly useful to pass in the splice flags; I also elected
     	 not to return any error code - though we might actually want to do
     	 that.

 (5) Provide tls_{device,sw}_splice_eof() to flush a pending TLS record if
     there is one.

 (6) Alter the behaviour of sendfile() and fix SPLICE_F_MORE/MSG_MORE
     signalling[1] such SPLICE_F_MORE is always signalled until we have
     read sufficient data to finish the request.  If we get a zero-length
     before we've managed to splice sufficient data, we now leave the
     socket expecting more data and leave it to userspace to deal with it.

 (7) Make AF_TLS handle the MSG_SPLICE_PAGES internal sendmsg flag.
     MSG_SPLICE_PAGES is an internal hint that tells the protocol that it
     should splice the pages supplied if it can.  Its sendpage
     implementations are then turned into wrappers around that.


I've pushed the patches here also:

	https://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs.git/log/?h=sendpage-2-tls

David

Changes
=======
ver #4)
 - Switch to using ->splice_eof() to signal premature EOF to the splice
   output[2].

ver #3)
 - Include the splice-to-socket rewrite patch.
 - Fix SPLICE_F_MORE/MSG_MORE signalling.
 - Allow AF_TLS to accept sendmsg() with MSG_SPLICE_PAGES before it is
   handled.
 - Allow a zero-length send() to a TLS socket to flush an outstanding
   record.
 - Address TLS kselftest failure.

ver #2)
 - Dropped the slab data copying.
 - "rls_" should be "tls_".
 - Attempted to fix splice_direct_to_actor().
 - Blocked MSG_SENDPAGE_* from being set by userspace.

Link: https://lore.kernel.org/r/499791.1685485603@xxxxxxxxxxxxxxxxxxxxxx/ [1]
Link: https://lore.kernel.org/r/CAHk-=wh=V579PDYvkpnTobCLGczbgxpMgGmmhqiTyE34Cpi5Gg@xxxxxxxxxxxxxx/ [2]
Link: https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next.git/commit/?id=51c78a4d532efe9543a4df019ff405f05c6157f6 # part 1
Link: https://lore.kernel.org/r/20230524153311.3625329-1-dhowells@xxxxxxxxxx/ # v1

David Howells (11):
  net: Block MSG_SENDPAGE_* from being passed to sendmsg() by userspace
  tls: Allow MSG_SPLICE_PAGES but treat it as normal sendmsg
  splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather than ->sendpage()
  splice, net: Add a splice_eof op to file-ops and socket-ops
  tls/sw: Use splice_eof() to flush
  tls/device: Use splice_eof() to flush
  splice, net: Fix SPLICE_F_MORE signalling in splice_direct_to_actor()
  tls/sw: Support MSG_SPLICE_PAGES
  tls/sw: Convert tls_sw_sendpage() to use MSG_SPLICE_PAGES
  tls/device: Support MSG_SPLICE_PAGES
  tls/device: Convert tls_device_sendpage() to use MSG_SPLICE_PAGES

 fs/splice.c            | 207 ++++++++++++++++++++++++++-------
 include/linux/fs.h     |   3 +-
 include/linux/net.h    |   1 +
 include/linux/socket.h |   4 +-
 include/linux/splice.h |   3 +
 include/net/sock.h     |   1 +
 net/socket.c           |  36 ++----
 net/tls/tls.h          |   2 +
 net/tls/tls_device.c   | 110 +++++++++---------
 net/tls/tls_main.c     |   4 +
 net/tls/tls_sw.c       | 253 ++++++++++++++++++++++-------------------
 11 files changed, 385 insertions(+), 239 deletions(-)