Finish moving things from conclusion to results
This commit is contained in:
Nico Schottelius
parent
2533ad653f
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3848ef2b96
2 changed files with 168 additions and 191 deletions
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@ -1,191 +1,20 @@
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\chapter{\label{summary}Conclusion}
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\chapter{\label{summary}Conclusion and Outlook}
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%** Summary.tex: What have you achieved, what have you presented in this
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% document. What are the highlights of your work.
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% It should conclude by a conclusion.
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Sum up what you have done and recapitulate your key findings.
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%\section{\label{conclusion:overall}Overall}
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\section{\label{conclusion:softwarenat64}Software based NAT64}
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\section{\label{conclusion:general}General}
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\section{\label{conclusion:bmv2}BMV2}
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\section{\label{conclusion:P4}P4}
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NDP parsing problem
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checksumming a frequent problem and helper
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p4 potential
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Many possibilities
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Protocol independent
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Easy architecture
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Limitations in
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NDP parsing support
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if in action limitations
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Limits if in actions
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python2 only - unicode errors
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IPv6: NDP: not easy to parse, as unknown number of following fields
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No support for multiple LPM keys in a table, can be solved with
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ternary matching.
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switch cannot be used in actions
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if things don't work, often a checksum problem.
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if frame checksum, then length of packet is broken
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\begin{verbatim}
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p4c --target bmv2 --arch v1model --std p4-16 "../p4src/static-mapping.p4" -o "/home/p4/master-thesis/p4src"
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../p4src/static-mapping.p4(366): error: Program is not supported by this target, because table MyIngress.v6_networks has multiple successors
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table v6_networks {
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^^^^^^^^^^^
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\end{verbatim}
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\begin{verbatim}
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ipaddress.ip_network("2001:db8:61::/64")
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IPv6Network(u'3230:3031:3a64:6238:3a36:313a:3a2f:3634/128')
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Fix:
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from __future__ import unicode_literals
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\end{verbatim}
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The tooling around P4 is still fragile, encountered many bugs
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in the development.\cite{schottelius:github1675}
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or missing features (\cite{schottelius:github745},
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\cite{theojepsen:_get})
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Hitting expression bug
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retrieving information from tables
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\begin{verbatim}
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Key and mask for matching destination is in table. We need this
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information in the action. However this information is not exposed, so
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we need to specify another parameter with the same information as in
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the key(s).
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Log from slack: (2019-03-14)
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nico [1:55 PM]
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If I use LPM for matching, can I easily get the network address from P4 or do I have to use a bitmask myself? In the latter case it is not exactly clear how to get the mask from the table
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Nate Foster [1:58 PM]
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You want to retrieve the address in the packet? In a table?
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And do you want to do the retrieving from the data plane or the control plane? (edited)
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nico [2:00 PM]
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If I have a match in a table that matches on LPM, it can be any IP address in a network
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For calculating the NAT64/NAT46 translation, I will need the base address, i.e. network address to do subtractions/additions
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So it is fully data plane, what I would like to do
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I'll commit sample code to show the use case more clearly
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https://gitlab.ethz.ch/nicosc/master-thesis/blob/master/p4src/static-mapping.p4#L73
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GitLab
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p4src/static-mapping.p4 · master · nicosc / master-thesis
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gitlab.ethz.ch
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So the action nat64_static() is used in the table v6_networks.
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In v6_networks I use a match on `hdr.ipv6.dst_addr: lpm;`
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What I would like to be able is to get the network address ; I can do that manually, if I have the mask
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I can also re-inject this parameter by another action argument, but I'd assume that I can somewhere read this out from the table / match
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Nate Foster [2:15 PM]
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To make sure I understand, in the data plane, you want to retrieve the address in the lpm pattern? (edited)
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nico [2:16 PM]
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I want to retrieve the key
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Nate Foster [2:16 PM]
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Wait. The value `hdr.ipv6.dst_addr` is the thing used in the match.
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So you have that.
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What you don’t have is the IPv6 address and mask put into the table by the control plane.
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I assume you want the latter, right?
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nico [2:17 PM]
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For example, if my matching key is 2001:db8::/32 and the real address is 2001:db8::f00, then I would like to retrieve 2001:db8:: and 32 from the table
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exactly :slightly_smiling_face:
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I can "fix" this by adding another argument, but it feels somewhat wrong to do that
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Because the table already knows this information
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Nate Foster [2:26 PM]
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I can’t think of a way other than the action parameter hack.
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nico [2:26 PM]
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Oh, ok
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Is it because the information is "lost in hardware"?
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Nate Foster [2:31 PM]
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No you’re right that most implementations have the value in memory. And one can imagine a different table API that allowed one to retrieve it in the data plane.
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But unless I am missing something obvious, P4 hides it…
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\end{verbatim}
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no meta information
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\begin{verbatim}
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Is there any meta information for "from which table was the action
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called" available? My use case is having a debug action that sends
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packets to the controller and I use it as a default_action in various
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tables; however know I don't know anymore from which table the action
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was called. Is there any kind of meta information which table called
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me available?
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I could work around this by using if(! .. .hit) { my_action(table_id)
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}, but it would not work with using default_action = ...
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\end{verbatim}
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type definitions separate
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Code sharing (controller, switch)
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\begin{verbatim}
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*** DONE Synchronisation with the controller
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- Double data type definition -> might differ
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- TYPE_CPU for ethernet
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- Port ingress offset (9 vs. 16 bit)
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\end{verbatim}
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No switch in actions, No conditional execution in actions
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P4os - reusable code
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\begin{verbatim}
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Not addressed so far: how to create re-usable code fragments that can
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be plugged in easily. There could be a hypothetical "P4OS" that
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manages code fragments. This might include, but not limited to
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downloading (signed?) source code, managing dependencies similar to
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Linux package management, handling updates, etc.
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\end{verbatim}
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idomatic problem: Security issue: not checking checksums before
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% ----------------------------------------------------------------------
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\section{\label{conclusion:netpfga}NetFGPA - all HERE}
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Needed to debug internal parsing errors
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debugging generated tcl code to debug impl1 error
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\section{\label{conclusion:realworld}Real world applications}
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Can be deployed using the netpfga. Or Barefoot or Arista.
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\section{\label{conclusion:outlook}Outlook}
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%** Outlook.tex: What needs to be done further, what is planed
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%
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What are the consequences of your work for future work?
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OUTLOOK What are the consequences of your work for future work?
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Different HW
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@ -205,28 +34,19 @@ No address / mac learning
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**** No DNS64
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has already been solved in a different domain - could even do
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transparent / in network modification
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transparent / in network modification. DNSSEC.
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**** Incomplete NDP
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Very limited option support
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No resolution of hardware addresses
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\section{\label{conclusion:closing}Closing words (NAME?)}
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While the port to NetPFGA was significantly more effort then expected,
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the learnings of the different layers were very much appreciated / liked
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It was a
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% ----------------------------------------------------------------------
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\section{\label{conclusion:netpfga2}NetFGPA2 - conclusion here}
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NetFGPA - conclusion here}
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Very time intensive development due to usability problems and
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uncertainty of functionality (compare sections
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\ref{results:netpfga:usability} and \ref{results:netpfga:stability}).
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\section{todo - FIXME: remove}
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\begin{verbatim}
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***** Summary eher kurz
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***** Outlook als subsection!
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\end{verbatim}
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157
doc/Results.tex
157
doc/Results.tex
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@ -471,6 +471,12 @@ General result: limited NAT64 is working, however
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No NDP, no ARP - focused on key factors of NAT64 translation,
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other features can be supported by controller
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Needed to debug internal parsing errors
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debugging generated tcl code to debug impl1 error
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% ----------------------------------------------------------------------
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\section{\label{results:tayga}Tayga}
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During the benchmark cpu bound, single thread
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@ -481,3 +487,154 @@ tayga: Single threaded
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kernel module
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high cpu usage for udp connetcinos
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Integration with iptables
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% ----------------------------------------------------------------------
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\section{\label{results:p4}P4}
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NDP parsing problem
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checksumming a frequent problem and helper
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if in action limitations
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switch cannot be used in actions
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python2 only - unicode errors
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IPv6: NDP: not easy to parse, as unknown number of following fields
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No support for multiple LPM keys in a table, can be solved with
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ternary matching.
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if things don't work, often a checksum problem.
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if frame checksum, then length of packet is broken
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\begin{verbatim}
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p4c --target bmv2 --arch v1model --std p4-16 "../p4src/static-mapping.p4" -o "/home/p4/master-thesis/p4src"
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../p4src/static-mapping.p4(366): error: Program is not supported by this target, because table MyIngress.v6_networks has multiple successors
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table v6_networks {
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^^^^^^^^^^^
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\end{verbatim}
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\begin{verbatim}
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ipaddress.ip_network("2001:db8:61::/64")
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IPv6Network(u'3230:3031:3a64:6238:3a36:313a:3a2f:3634/128')
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Fix:
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from __future__ import unicode_literals
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\end{verbatim}
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The tooling around P4 is still fragile, encountered many bugs
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in the development.\cite{schottelius:github1675}
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or missing features (\cite{schottelius:github745},
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\cite{theojepsen:_get})
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Hitting expression bug
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retrieving information from tables
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\begin{verbatim}
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Key and mask for matching destination is in table. We need this
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information in the action. However this information is not exposed, so
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we need to specify another parameter with the same information as in
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the key(s).
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Log from slack: (2019-03-14)
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nico [1:55 PM]
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If I use LPM for matching, can I easily get the network address from P4 or do I have to use a bitmask myself? In the latter case it is not exactly clear how to get the mask from the table
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Nate Foster [1:58 PM]
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You want to retrieve the address in the packet? In a table?
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And do you want to do the retrieving from the data plane or the control plane? (edited)
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nico [2:00 PM]
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If I have a match in a table that matches on LPM, it can be any IP address in a network
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For calculating the NAT64/NAT46 translation, I will need the base address, i.e. network address to do subtractions/additions
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So it is fully data plane, what I would like to do
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I'll commit sample code to show the use case more clearly
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https://gitlab.ethz.ch/nicosc/master-thesis/blob/master/p4src/static-mapping.p4#L73
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GitLab
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p4src/static-mapping.p4 · master · nicosc / master-thesis
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gitlab.ethz.ch
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So the action nat64_static() is used in the table v6_networks.
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In v6_networks I use a match on `hdr.ipv6.dst_addr: lpm;`
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What I would like to be able is to get the network address ; I can do that manually, if I have the mask
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I can also re-inject this parameter by another action argument, but I'd assume that I can somewhere read this out from the table / match
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Nate Foster [2:15 PM]
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To make sure I understand, in the data plane, you want to retrieve the address in the lpm pattern? (edited)
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nico [2:16 PM]
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I want to retrieve the key
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Nate Foster [2:16 PM]
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Wait. The value `hdr.ipv6.dst_addr` is the thing used in the match.
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So you have that.
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What you don’t have is the IPv6 address and mask put into the table by the control plane.
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I assume you want the latter, right?
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nico [2:17 PM]
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For example, if my matching key is 2001:db8::/32 and the real address is 2001:db8::f00, then I would like to retrieve 2001:db8:: and 32 from the table
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exactly :slightly_smiling_face:
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I can "fix" this by adding another argument, but it feels somewhat wrong to do that
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Because the table already knows this information
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Nate Foster [2:26 PM]
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I can’t think of a way other than the action parameter hack.
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nico [2:26 PM]
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Oh, ok
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Is it because the information is "lost in hardware"?
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Nate Foster [2:31 PM]
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No you’re right that most implementations have the value in memory. And one can imagine a different table API that allowed one to retrieve it in the data plane.
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But unless I am missing something obvious, P4 hides it…
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\end{verbatim}
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no meta information
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\begin{verbatim}
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Is there any meta information for "from which table was the action
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called" available? My use case is having a debug action that sends
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packets to the controller and I use it as a default_action in various
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tables; however know I don't know anymore from which table the action
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was called. Is there any kind of meta information which table called
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me available?
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I could work around this by using if(! .. .hit) { my_action(table_id)
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}, but it would not work with using default_action = ...
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\end{verbatim}
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type definitions separate
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Code sharing (controller, switch)
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\begin{verbatim}
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*** DONE Synchronisation with the controller
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- Double data type definition -> might differ
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- TYPE_CPU for ethernet
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- Port ingress offset (9 vs. 16 bit)
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\end{verbatim}
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No switch in actions, No conditional execution in actions
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P4os - reusable code
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\begin{verbatim}
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Not addressed so far: how to create re-usable code fragments that can
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be plugged in easily. There could be a hypothetical "P4OS" that
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manages code fragments. This might include, but not limited to
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downloading (signed?) source code, managing dependencies similar to
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Linux package management, handling updates, etc.
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\end{verbatim}
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idomatic problem: Security issue: not checking checksums before
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