David Ahern <d...@cumulusnetworks.com> writes: > On 2/15/17 8:25 PM, Andy Lutomirski wrote: >> On Wed, Feb 15, 2017 at 7:18 PM, David Ahern <d...@cumulusnetworks.com> >> wrote: >>> On 2/15/17 8:08 PM, Eric W. Biederman wrote: >>>> David Ahern <d...@cumulusnetworks.com> writes: >>>> >>>>> On 2/14/17 12:21 AM, Eric W. Biederman wrote: >>>>>>> in cases where bpf programs are looking at sockets and packets >>>>>>> that belong to different netns, it could be useful to get an id >>>>>>> that uniquely identify a netns within the whole system. >>>>>> It could be useful but there is no unique namespace id. >>>>>> >>>>> >>>>> Have you given thought to a unique namespace id? Networking tracepoints >>>>> for example could really benefit from a unique id. >>>> >>>> An id from the perspective of a process in the initial instance of every >>>> namespace is certainly possible. >>>> >>>> A truly unique id is just not maintainable. Think of the question how >>>> do you assign every device in the world a rguaranteed unique ip address >>>> without coordination, that is routable. It is essentially the same >>>> problem. >>>> >>>> AKA it is theoretically possible and very expensive. It is much easier >>>> and much more maintainable for identifiers to have scope and only be >>>> unique within that scope. >>> >>> >>> I don't mean unique in the entire world, I mean unique within a single >>> system. >>> >>> Tracepoints are code based and have global scope. I would like to be >>> able to correlate, for example, FIB lookups within a single network >>> namespace. Having an id that I could filter on when collecting or match >>> when dumping them goes a long way. >> >> Why wouldn't an id relative to your logging program work? Global ids >> are problematic because they are incompatible with tools like CRIU. >> > > How would that work? > > To be specific with an example, I only want FIB lookups for network > namespace "foo". The name "foo" only has meaning for iproute2, so I need > something the kernel understands. Should that be a dev/inode match > meaning the tracepoints contain the netns dev and inode? > > From a perf perspective, the command line is like this: > perf record -e fib:fib_table_lookup --filter="netns_dev == 3 && > netns_ino == 4026531957" -a -g -- sleep 5 > > Cumbersome, but it would work if the tracepoints had netns_dev and > netns_ino as variables. A single id would be better.
A netns_dev_ino variable perhaps? Something that you could pass a netns file descriptor to perf and perf would just sort out the rest? I believe those are just tooling issues. The practical issue with one id that is global everywhere is that it has to work for checkpoint/restart. At which point it truly has to be globably unique or namespaced. Eric
