mptcp: rework mptcp_sendmsg_frag to accept optional dfrag

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This will simplify mptcp-level retransmission implementation
in the next patch. If dfrag is provided by the caller, skip
kernel space memory allocation and use data and metadata
provided by the dfrag itself.

Because a peer could ack data at TCP level but refrain from
sending mptcp-level ACKs, we could grow the mptcp socket
backlog indefinitely.

We should thus block mptcp_sendmsg until the peer has acked some of the
sent data.

In order to be able to do so, increment the mptcp socket wmem_queued
counter on memory allocation and decrement it when releasing the memory
on mptcp-level ack reception.

Because TCP performns sndbuf auto-tuning up to tcp_wmem_max[2], make
this the mptcp sk_sndbuf limit.

In the future we could add experiment with autotuning as TCP does in
tcp_sndbuf_expand().

v2 -> v3:
 - remove 'inline' in foo.c files (David S. Miller)

Co-developed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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This commit is contained in:

Paolo Abeni 2020-03-27 14:48:47 -07:00 • committed by David S. Miller

parent 7948f6cc99

commit 3f8e0aae17

1 changed files with 74 additions and 49 deletions

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net/mptcp/protocol.c

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