[RFC,0/3] net: Drop size arg from ->sendmsg() and pass msghdr into __ip{,6}_append_data()

  Hi Willem,

Here's another option to passing MSG_SPLICE_PAGES into sendmsg()[1] without
polluting the flags in msg->msg_flags.  The idea here is to put the flag
into a new field in msghdr, msg_kflags, that holds internal kernel flags
that aren't available to userspace.

What I've done here is:

 (1) Pass msg down to __ip_append_data() and __ip6_append_data() so that
     they can access the extra flags.

 (2) In order to avoid adding extra arguments to these functions and the
     functions in their call chains (such as ip_make_skb()), remove the
     size and flags arguments as these values are redundant if msg is
     passed in.

 (3) msg is then passed into getfrag().  I would like to get rid of the
     "from" argument also in favour of using something in msghdr, but I'm
     not sure how best to do that.

 (4) The size parameter to ->sendmsg() seems to be redundant; indeed
     sock_sendmsg() doesn't actually take it, but rather gets the count
     from msg_iter - so remove this parameter.

     kernel_sendmsg() will still take a size, but it sets it on the
     iterator and then calls sock_sendmsg().

 (5) Protocol sendmsg implementations then extract the length and the flags
     from the iterator.

 (6) Illustrate the addition of msg_kflags and MSG_SPLICE_PAGES.  I think
     that, at some point in the future, some of the other flags could be
     moved from msg_flags to msg_kflags.

David

Link: https://lore.kernel.org/r/20230316152618.711970-1-dhowells@redhat.com/ [1]

David Howells (3):
  net: Drop the size argument from ->sendmsg()
  ip: Make __ip{,6}_append_data() and co. take a msghdr*
  net: Declare MSG_SPLICE_PAGES internal sendmsg() flag

 crypto/af_alg.c                               | 12 +--
 crypto/algif_aead.c                           |  9 +--
 crypto/algif_hash.c                           |  8 +-
 crypto/algif_rng.c                            |  3 +-
 crypto/algif_skcipher.c                       | 10 +--
 drivers/isdn/mISDN/socket.c                   |  3 +-
 .../chelsio/inline_crypto/chtls/chtls.h       |  2 +-
 .../chelsio/inline_crypto/chtls/chtls_io.c    | 15 ++--
 drivers/net/ppp/pppoe.c                       |  4 +-
 drivers/net/tap.c                             |  3 +-
 drivers/net/tun.c                             |  3 +-
 drivers/vhost/net.c                           |  6 +-
 drivers/xen/pvcalls-back.c                    |  2 +-
 drivers/xen/pvcalls-front.c                   |  4 +-
 drivers/xen/pvcalls-front.h                   |  3 +-
 fs/afs/rxrpc.c                                |  8 +-
 include/crypto/if_alg.h                       |  3 +-
 include/linux/lsm_hook_defs.h                 |  3 +-
 include/linux/lsm_hooks.h                     |  1 -
 include/linux/net.h                           |  6 +-
 include/linux/security.h                      |  4 +-
 include/linux/socket.h                        |  3 +
 include/net/af_rxrpc.h                        |  3 +-
 include/net/inet_common.h                     |  2 +-
 include/net/ip.h                              | 24 +++---
 include/net/ipv6.h                            | 22 +++---
 include/net/ping.h                            |  7 +-
 include/net/sock.h                            |  7 +-
 include/net/tcp.h                             |  8 +-
 include/net/udp.h                             |  2 +-
 include/net/udplite.h                         |  4 +-
 net/appletalk/ddp.c                           |  3 +-
 net/atm/common.c                              |  3 +-
 net/atm/common.h                              |  2 +-
 net/ax25/af_ax25.c                            |  4 +-
 net/bluetooth/hci_sock.c                      |  4 +-
 net/bluetooth/iso.c                           |  4 +-
 net/bluetooth/l2cap_sock.c                    |  5 +-
 net/bluetooth/rfcomm/sock.c                   |  7 +-
 net/bluetooth/sco.c                           |  4 +-
 net/caif/caif_socket.c                        | 13 ++--
 net/can/bcm.c                                 |  3 +-
 net/can/isotp.c                               |  3 +-
 net/can/j1939/socket.c                        |  4 +-
 net/can/raw.c                                 |  3 +-
 net/core/sock.c                               |  4 +-
 net/dccp/dccp.h                               |  2 +-
 net/dccp/proto.c                              |  3 +-
 net/ieee802154/socket.c                       | 11 +--
 net/ipv4/af_inet.c                            |  4 +-
 net/ipv4/icmp.c                               | 14 ++--
 net/ipv4/ip_output.c                          | 73 ++++++++++---------
 net/ipv4/ping.c                               | 18 ++---
 net/ipv4/raw.c                                | 23 +++---
 net/ipv4/tcp.c                                | 17 +++--
 net/ipv4/tcp_bpf.c                            |  5 +-
 net/ipv4/tcp_input.c                          |  3 +-
 net/ipv4/udp.c                                | 24 +++---
 net/ipv6/af_inet6.c                           |  7 +-
 net/ipv6/icmp.c                               | 21 ++++--
 net/ipv6/ip6_output.c                         | 57 +++++++--------
 net/ipv6/ping.c                               | 12 +--
 net/ipv6/raw.c                                | 25 +++----
 net/ipv6/udp.c                                | 26 ++++---
 net/ipv6/udp_impl.h                           |  2 +-
 net/iucv/af_iucv.c                            |  4 +-
 net/kcm/kcmsock.c                             |  2 +-
 net/key/af_key.c                              |  3 +-
 net/l2tp/l2tp_ip.c                            |  3 +-
 net/l2tp/l2tp_ip6.c                           |  3 +-
 net/l2tp/l2tp_ppp.c                           |  4 +-
 net/llc/af_llc.c                              |  5 +-
 net/mctp/af_mctp.c                            |  3 +-
 net/mptcp/protocol.c                          |  8 +-
 net/netlink/af_netlink.c                      | 11 +--
 net/netrom/af_netrom.c                        |  3 +-
 net/nfc/llcp_sock.c                           |  7 +-
 net/nfc/rawsock.c                             |  3 +-
 net/packet/af_packet.c                        | 11 +--
 net/phonet/datagram.c                         |  3 +-
 net/phonet/pep.c                              |  3 +-
 net/phonet/socket.c                           |  5 +-
 net/qrtr/af_qrtr.c                            |  4 +-
 net/rds/rds.h                                 |  2 +-
 net/rds/send.c                                |  3 +-
 net/rose/af_rose.c                            |  3 +-
 net/rxrpc/af_rxrpc.c                          |  6 +-
 net/rxrpc/ar-internal.h                       |  2 +-
 net/rxrpc/output.c                            | 22 +++---
 net/rxrpc/rxperf.c                            |  4 +-
 net/rxrpc/sendmsg.c                           | 15 ++--
 net/sctp/socket.c                             |  3 +-
 net/smc/af_smc.c                              |  5 +-
 net/socket.c                                  | 16 ++--
 net/tipc/socket.c                             | 34 ++++-----
 net/tls/tls.h                                 |  4 +-
 net/tls/tls_device.c                          |  5 +-
 net/tls/tls_sw.c                              |  2 +-
 net/unix/af_unix.c                            | 19 +++--
 net/vmw_vsock/af_vsock.c                      | 16 ++--
 net/x25/af_x25.c                              |  3 +-
 net/xdp/xsk.c                                 |  6 +-
 net/xfrm/espintcp.c                           |  8 +-
 security/apparmor/lsm.c                       |  6 +-
 security/security.c                           |  4 +-
 security/selinux/hooks.c                      |  3 +-
 security/smack/smack_lsm.c                    |  4 +-
 security/tomoyo/common.h                      |  3 +-
 security/tomoyo/network.c                     |  4 +-
 security/tomoyo/tomoyo.c                      |  6 +-
 110 files changed, 444 insertions(+), 456 deletions(-)