From: David Miller <davem@davemloft.net>
To: sowmini.varadhan@oracle.com
Cc: willemdebruijn.kernel@gmail.com, sridhar.samudrala@intel.com,
netdev@vger.kernel.org, willemb@google.com
Subject: Re: [PATCH RFC net-next 00/11] udp gso
Date: Wed, 18 Apr 2018 13:28:08 -0400 (EDT) [thread overview]
Message-ID: <20180418.132808.1710130437020293308.davem@davemloft.net> (raw)
In-Reply-To: <20180418123103.GC19633@oracle.com>
From: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Date: Wed, 18 Apr 2018 08:31:03 -0400
> However, I share Sridhar's concerns about the very fundamental change
> to UDP message boundary semantics here. There is actually no such thing
> as a "segment" in udp, so in general this feature makes me a little
> uneasy. Well behaved udp applications should already be sending mtu
> sized datagrams. And the not-so-well-behaved ones are probably relying
> on IP fragmentation/reassembly to take care of datagram boundary semantics
> for them?
>
> As Sridhar points out, the feature is not really "negotiated" - one side
> unilaterally sets the option. If the receiver is a classic/POSIX UDP
> implementation, it will have no way of knowing that message boundaries
> have been re-adjusted at the sender.
There are no "semantics".
What ends up on the wire is the same before the kernel/app changes as
afterwards.
The only difference is that instead of the application doing N - 1
sendmsg() calls with mtu sized writes, it's giving everything all at
once and asking the kernel to segment.
It even gives the application control over the size of the packets,
which I think is completely prudent in this situation.
next prev parent reply other threads:[~2018-04-18 17:28 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-17 20:00 [PATCH RFC net-next 00/11] udp gso Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 01/11] udp: expose inet cork to udp Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 02/11] udp: add gso Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 03/11] udp: better wmem accounting on gso Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 04/11] udp: paged allocation with gso Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 05/11] udp: add gso segment cmsg Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 06/11] udp: add gso support to virtual devices Willem de Bruijn
2018-04-18 0:43 ` Dimitris Michailidis
2018-04-18 3:27 ` Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 07/11] udp: zerocopy Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 08/11] selftests: udp gso Willem de Bruijn
2018-04-17 20:00 ` [PATCH RFC net-next 09/11] selftests: udp gso with connected sockets Willem de Bruijn
2018-04-17 20:15 ` [PATCH RFC net-next 00/11] udp gso Sowmini Varadhan
2018-04-17 20:23 ` Willem de Bruijn
2018-04-17 20:48 ` Sowmini Varadhan
2018-04-17 21:07 ` Willem de Bruijn
2018-04-18 2:25 ` Samudrala, Sridhar
2018-04-18 3:33 ` Willem de Bruijn
2018-04-18 12:31 ` Sowmini Varadhan
2018-04-18 13:35 ` Eric Dumazet
2018-04-18 13:47 ` Sowmini Varadhan
2018-04-18 13:51 ` Willem de Bruijn
2018-04-18 15:08 ` Samudrala, Sridhar
2018-04-18 17:40 ` David Miller
2018-04-18 17:34 ` David Miller
2018-04-18 13:59 ` Willem de Bruijn
2018-04-18 14:28 ` Willem de Bruijn
2018-04-18 17:28 ` David Miller [this message]
2018-04-18 18:12 ` Alexander Duyck
2018-04-18 18:22 ` Willem de Bruijn
2018-04-20 17:38 ` Alexander Duyck
2018-04-20 21:58 ` Willem de Bruijn
2018-04-21 2:08 ` Alexander Duyck
2018-04-18 19:33 ` David Miller
2018-04-20 18:27 ` Tushar Dave
2018-04-20 20:08 ` Alexander Duyck
2018-04-21 3:11 ` Tushar Dave
2018-08-31 9:09 ` Paolo Abeni
2018-08-31 10:09 ` Eric Dumazet
2018-08-31 13:08 ` Willem de Bruijn
2018-08-31 13:44 ` Paolo Abeni
2018-08-31 15:11 ` Willem de Bruijn
2018-09-03 8:02 ` Steffen Klassert
2018-09-03 11:45 ` Sowmini Varadhan
2018-04-18 11:17 ` Paolo Abeni
2018-04-18 13:49 ` Willem de Bruijn
2018-05-24 0:02 ` Marcelo Ricardo Leitner
2018-05-24 1:15 ` Willem de Bruijn
2018-04-18 17:24 ` David Miller
2018-04-18 17:50 ` David Miller
2018-04-18 18:12 ` Willem de Bruijn
2018-04-19 17:45 ` David Miller
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