On Thu, 2019-06-27 at 08:29 -0700, Stephen Hemminger wrote: > On Thu, 27 Jun 2019 11:43:27 +0200 > Jiri Pirko <j...@resnulli.us> wrote: > > > Hi all. > > > > In the past, there was repeatedly discussed the IFNAMSIZ (16) limit > > for > > netdevice name length. Now when we have PF and VF representors > > with port names like "pfXvfY", it became quite common to hit this > > limit: > > 0123456789012345 > > enp131s0f1npf0vf6 > > enp131s0f1npf0vf22 > > > > Since IFLA_NAME is just a string, I though it might be possible to > > use > > it to carry longer names as it is. However, the userspace tools, > > like > > iproute2, are doing checks before print out. So for example in > > output of > > "ip addr" when IFLA_NAME is longer than IFNAMSIZE, the netdevice is > > completely avoided. > > > > So here is a proposal that might work: > > 1) Add a new attribute IFLA_NAME_EXT that could carry names longer > > than > > IFNAMSIZE, say 64 bytes. The max size should be only defined in > > kernel, > > user should be prepared for any string size. > > 2) Add a file in sysfs that would indicate that NAME_EXT is > > supported by > > the kernel. > > 3) Udev is going to look for the sysfs indication file. In case > > when > > kernel supports long names, it will do rename to longer name, > > setting > > IFLA_NAME_EXT. If not, it does what it does now - fail. > > 4) There are two cases that can happen during rename: > > A) The name is shorter than IFNAMSIZ > > -> both IFLA_NAME and IFLA_NAME_EXT would contain the same > > string: > > original IFLA_NAME = eth0 > > original IFLA_NAME_EXT = eth0 > > renamed IFLA_NAME = enp5s0f1npf0vf1 > > renamed IFLA_NAME_EXT = enp5s0f1npf0vf1 > > B) The name is longer tha IFNAMSIZ > > -> IFLA_NAME would contain the original one, IFLA_NAME_EXT > > would > > contain the new one: > > original IFLA_NAME = eth0 > > original IFLA_NAME_EXT = eth0 > > renamed IFLA_NAME = eth0 > > renamed IFLA_NAME_EXT = enp131s0f1npf0vf22
It makes me a bit uncomfortable to allow IFLA_NAME and IFLA_NAME_EXT to be completely different. That sounds like a big source of confusion and debugging problems in production. Dan > > This would allow the old tools to work with "eth0" and the new > > tools would work with "enp131s0f1npf0vf22". In sysfs, there would > > be symlink from one name to another. > > > > Also, there might be a warning added to kernel if someone works > > with IFLA_NAME that the userspace tool should be upgraded. > > > > Eventually, only IFLA_NAME_EXT is going to be used by everyone. > > > > I'm aware there are other places where similar new attribute > > would have to be introduced too (ip rule for example). > > I'm not saying this is a simple work. > > > > Question is what to do with the ioctl api (get ifindex etc). I > > would > > probably leave it as is and push tools to use rtnetlink instead. > > > > Any ideas why this would not work? Any ideas how to solve this > > differently? > > > > Thanks! > > > > Jiri > > > > I looked into this in the past, but then rejected it because > there are so many tools that use names, not just iproute2. > Plus long names are very user unfriendly.
