Alexei Starovoitov <alexei.starovoitov@xxxxxxxxx> writes: > On Wed, Nov 18, 2020 at 06:07:38PM +0100, Toke Høiland-Jørgensen wrote: >> As a response to patches adding libbpf support to iproute2, an extensive >> discussion ensued about libbpf version visibility and enforcement in tools >> using the library[0]. In particular, two problems came to light: >> >> 1. If a tool is statically linked against libbpf, there is no way for a user >> to discover which version of libbpf the tool is using, unless the tool >> takes particular care to embed the library version at build time and print >> it. >> >> 2. If a tool is dynamically linked against libbpf, but doesn't use any >> symbols from the latest library version, the library version used at >> runtime can be older than the one used at compile time, and the >> application has no way to verify the version at runtime. >> >> To make progress on resolving this, let's add a libbpf_version() function that >> will simply return a version string which is embedded into the library at >> compile time. This makes it possible for applications to unambiguously get the >> library version at runtime, resolving (2.) above, and as an added bonus makes it >> easy for applications to print the library version, which should help with (1.). >> >> [0] https://lore.kernel.org/bpf/20201109070802.3638167-1-haliu@xxxxxxxxxx/T/#t >> >> Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx> > > Unless iproute2 adopts scrict libbpf.so.version == iproute2.version policy > and removes legacy bpf loader no iproute2 driven changes to libbpf will be accepted. > Just like the kernel doesn't add features for out-of-tree modules > libbpf doesn't add features for projects where libbpf is optional. This is not a iproute2-specific feature, though. It came out of the iproute2 discussion, sure, but it's a generic helper to get the library version for any application that wants to use it. In particular, I am planning to use this in the xdp-tools binaries: $ ./xdpdump --version xdpdump version 1.0.1 using libbpf version 0.3.0 -Toke
