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* [PATCH v4 00/16] Simplify and correct handling of "spliced" UDP forwarding
@ 2022-11-30  4:13 David Gibson
  2022-11-30  4:13 ` [PATCH v4 01/16] udp: Also bind() connected ports for "splice" forwarding David Gibson
                   ` (16 more replies)
  0 siblings, 17 replies; 18+ messages in thread
From: David Gibson @ 2022-11-30  4:13 UTC (permalink / raw)
  To: Stefano Brivio, passt-dev; +Cc: David Gibson

The UDP "splicing" (forwarding packets from one L4 socket to another,
rather than via the tuntap device) code assumes that any given UDP
port in the init namespace will only communicate with a single port on
the ns side at a time, and vice versa.  This will often be the case,
but since UDP is a connectionless protocol, it need not be.  In fact
it is not the case in our existing UDP bandwidth checks, although the
specific configuration there means it's not harmful in that case.

The failure mode in this case can be quite bad: we don't just fall
back to an unoptimized oath, or drop packets, we will misdirect
packets to the wrong destination.

This series make some substantial simplifications to how we handle the
splice forwarding, then corrects it to handle the case of multiple
source ports sending to a single destination.

This does come at a performance cost.  It's not as large as I feared,
and shouldn't affect the most common case where there is a 1 to 1
mapping between source and destination ports.  I haven't yet been able
to confirm the latter because the iperf3 bandwidth test we use *does*
have interleaved streams with a common destination port.

Based on the earlier series for dual stack TCP sockets.

Changes since v3:
 * Changed interface of udp_splice_sendfrom() to slightly better
   separate concerns and to make some future cleanups simpler
 * Fixed a serious buffer overrun bug where we weren't bounds checking
   as we scanned for additional datagrams with the same source
   address.
Changes since v2:
 * Minor style and comment revisions
Changes since v1:
 * Added patches 12..16/16 fixing the delivery of packets, as well as
   just simplifying the mechanics

David Gibson (16):
  udp: Also bind() connected ports for "splice" forwarding
  udp: Separate tracking of inbound and outbound packet flows
  udp: Always use sendto() rather than send() for forwarding spliced
    packets
  udp: Don't connect "forward" sockets for spliced flows
  udp: Remove the @bound field from union udp_epoll_ref
  udp: Split splice field in udp_epoll_ref into (mostly) independent
    bits
  udp: Don't create double sockets for -U port
  udp: Re-use fixed bound sockets for packet forwarding when possible
  udp: Don't explicitly track originating socket for spliced
    "connections"
  udp: Update UDP "connection" timestamps in both directions
  udp: Simplify udp_sock_handler_splice
  udp: Make UDP_SPLICE_FRAMES and UDP_TAP_FRAMES_MEM the same thing
  udp: Add helper to extract port from a sockaddr_in or sockaddr_in6
  udp: Unify buffers for tap and splice paths
  udp: Split send half of udp_sock_handler_splice() from the receive
    half
  udp: Correct splice forwarding when receiving from multiple sources

 passt.h |   2 +
 udp.c   | 522 ++++++++++++++++++++++++++------------------------------
 udp.h   |  16 +-
 3 files changed, 248 insertions(+), 292 deletions(-)

-- 
2.38.1


^ permalink raw reply	[flat|nested] 18+ messages in thread

end of thread, other threads:[~2022-12-06  6:45 UTC | newest]

Thread overview: 18+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2022-11-30  4:13 [PATCH v4 00/16] Simplify and correct handling of "spliced" UDP forwarding David Gibson
2022-11-30  4:13 ` [PATCH v4 01/16] udp: Also bind() connected ports for "splice" forwarding David Gibson
2022-11-30  4:13 ` [PATCH v4 02/16] udp: Separate tracking of inbound and outbound packet flows David Gibson
2022-11-30  4:13 ` [PATCH v4 03/16] udp: Always use sendto() rather than send() for forwarding spliced packets David Gibson
2022-11-30  4:13 ` [PATCH v4 04/16] udp: Don't connect "forward" sockets for spliced flows David Gibson
2022-11-30  4:13 ` [PATCH v4 05/16] udp: Remove the @bound field from union udp_epoll_ref David Gibson
2022-11-30  4:13 ` [PATCH v4 06/16] udp: Split splice field in udp_epoll_ref into (mostly) independent bits David Gibson
2022-11-30  4:13 ` [PATCH v4 07/16] udp: Don't create double sockets for -U port David Gibson
2022-11-30  4:13 ` [PATCH v4 08/16] udp: Re-use fixed bound sockets for packet forwarding when possible David Gibson
2022-11-30  4:13 ` [PATCH v4 09/16] udp: Don't explicitly track originating socket for spliced "connections" David Gibson
2022-11-30  4:13 ` [PATCH v4 10/16] udp: Update UDP "connection" timestamps in both directions David Gibson
2022-11-30  4:13 ` [PATCH v4 11/16] udp: Simplify udp_sock_handler_splice David Gibson
2022-11-30  4:13 ` [PATCH v4 12/16] udp: Make UDP_SPLICE_FRAMES and UDP_TAP_FRAMES_MEM the same thing David Gibson
2022-11-30  4:13 ` [PATCH v4 13/16] udp: Add helper to extract port from a sockaddr_in or sockaddr_in6 David Gibson
2022-11-30  4:13 ` [PATCH v4 14/16] udp: Unify buffers for tap and splice paths David Gibson
2022-11-30  4:13 ` [PATCH v4 15/16] udp: Split send half of udp_sock_handler_splice() from the receive half David Gibson
2022-11-30  4:13 ` [PATCH v4 16/16] udp: Correct splice forwarding when receiving from multiple sources David Gibson
2022-12-06  6:45 ` [PATCH v4 00/16] Simplify and correct handling of "spliced" UDP forwarding Stefano Brivio

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