We just had our 25th (\o/) meeting with Mat, Peter and Ossama (Intel
OTC), Christoph (Apple) and myself (Tessares).
Thanks again for this new good meeting!
Here are the minutes of the meeting:
Review of Mat & Peter's patches:
- IPPROTO_MPTCP vs AF_MULTIPATH:
- We should document the advantages/disadvantages of each (*Mat*
will try to have a look at that)
- Not an issue to switch from one to another if needed later.
- get rid of SKB's priv_copy()
- we can remove it, it depends who will need it
- difficult what other might need. Maybe better to start simple
with not too much flexibility.
- we will then remove the priv_copy() but we need to keep the
- receiving part: DSS mapping: error_queue → dedicated queue? or
only for the signalling?
- Christoph: maybe difficult to manage that in queue.
- maybe using tcp_read_sock()
- we will always need an ofo_queue
- DSS ACK not driven by the app in theory (like TCP) but we
could ignore that for the moment?
- we can manage optimisation later
- what is important is something easy to maintain and understand
for the moment, keep it simple by using the right available structures.
- we can read data from one subflow as long as it is in order
and then switch to the other subflows.
- we need to be careful with the windows: the new window is
checked at every ACK but we need to know when to increase it. First
solution could be to stall the window, close it, then increase it.
- MPTCP: windows are shared between SF, if we share the memory
equally between subflows, that's not the best when a SF contains crap.
- decision: take the error_queue out
- receiving part: bypass coalesce/collapse for MPTCP OR do
coalescing that takes DSS-mappings into account → priv_used is the
perfect infrastructure for that.
- linked to the previous point.
- smart coalesce can be useful for kTLS
- trigger the closing in the right sequence → First, we need to
close the MPTCP-layer and then the subflows.
- optimisation can be done later to close both at the same time
- it is for the last data that need to be sent if you close the
subflows first but still some data coming.
- Christoph will try to find an article to give more details
about that →
"Essentially, a host MUST NOT close all functioning subflows
unless it is safe to do so, i.e., until all outstanding data has been
DATA_ACKed, or until the segment with the DATA_FIN flag set is the only
- prepend MPTCP_ / mptcp_ everywhere → subflow, token, crypto, etc.?
- everything visible should be prepended.
- subflow socket type:
- we could keep a TCP proto but modify the pointers where
needed. We should check how it is done with kTLS.
- we don't want to have the userspace creating a subflow
directly → by using IPPROTO_SUBFLOW
- So overriding pointers would make sense. It is a special proto
for MPTCP, kernel side only.
- packetdrill: no more news from Neil (see the discussions we had
- Seems oriented for drivers devs:
- we need to check if it can be useful for us → Matt will do that
tools: start using TopGit?
- maybe too soon for our repo
- would be nice to already do some experiments with that:
- once Mat and Peter's patches are accepted maybe
- we can do that later
tools: use Gerrit for the reviews?
- can be helpful, easier to keep track on stuff than with a ML
because there might be a lot of discussions around patches for this project.
- Matth will have a look at this
- (still possible to keep both, we can quickly experiment)
- We propose to have it on Thursday, the 18th of October. Usual
time: 9am PDT - 16:00 UTC (9am PDT, 6pm CEST)
- Still open to everyone!
Feel free to comment on these points and propose new ones for the next
Talk to you next week,
Matthieu Baerts | R&D Engineer
Tessares SA | Hybrid Access Solutions
1 Avenue Jean Monnet, 1348 Louvain-la-Neuve, Belgium