On 8/22/19 3:38 PM, Toke Høiland-Jørgensen wrote:
Daniel Borkmann <daniel@xxxxxxxxxxxxx> writes:
On 8/22/19 2:04 PM, Toke Høiland-Jørgensen wrote:
Daniel Borkmann <daniel@xxxxxxxxxxxxx> writes:
On 8/22/19 12:43 PM, Toke Høiland-Jørgensen wrote:
Daniel Borkmann <daniel@xxxxxxxxxxxxx> writes:
On 8/20/19 1:47 PM, Toke Høiland-Jørgensen wrote:
This adds a configure check for libbpf and renames functions to allow
lib/bpf.c to be compiled with it present. This makes it possible to
port functionality piecemeal to use libbpf.
Signed-off-by: Toke Høiland-Jørgensen <toke@xxxxxxxxxx>
---
configure | 16 ++++++++++++++++
include/bpf_util.h | 6 +++---
ip/ipvrf.c | 4 ++--
lib/bpf.c | 33 +++++++++++++++++++--------------
4 files changed, 40 insertions(+), 19 deletions(-)
diff --git a/configure b/configure
index 45fcffb6..5a89ee9f 100755
--- a/configure
+++ b/configure
@@ -238,6 +238,19 @@ check_elf()
fi
}
+check_libbpf()
+{
+ if ${PKG_CONFIG} libbpf --exists; then
+ echo "HAVE_LIBBPF:=y" >>$CONFIG
+ echo "yes"
+
+ echo 'CFLAGS += -DHAVE_LIBBPF' `${PKG_CONFIG} libbpf --cflags` >> $CONFIG
+ echo 'LDLIBS += ' `${PKG_CONFIG} libbpf --libs` >>$CONFIG
+ else
+ echo "no"
+ fi
+}
+
check_selinux()
More of an implementation detail at this point in time, but want to
make sure this doesn't get missed along the way: as discussed at
bpfconf [0] best for iproute2 to handle libbpf support would be the
same way of integration as pahole does, that is, to integrate it via
submodule [1] to allow kernel and libbpf features to be in sync with
iproute2 releases and therefore easily consume extensions we're adding
to libbpf to aide iproute2 integration.
I can sorta see the point wrt keeping in sync with kernel features. But
how will this work with distros that package libbpf as a regular
library? Have you guys given up on regular library symbol versioning for
libbpf?
Not at all, and I hope you know that. ;-)
Good! Didn't really expect you had, just checking ;)
The reason I added lib/bpf.c integration into iproute2 directly back
then was exactly such that users can start consuming BPF for tc and
XDP via iproute2 /everywhere/ with only a simple libelf dependency
which is also available on all distros since pretty much forever. If
it was an external library, we could have waited till hell freezes
over and initial distro adoption would have pretty much taken forever:
to pick one random example here wrt the pace of some downstream
distros [0]. The main rationale is pretty much the same as with added
kernel features that land complementary iproute2 patches for that
kernel release and as libbpf is developed alongside it is reasonable
to guarantee user expectations that iproute2 released for kernel
version x can make use of BPF features added to kernel x with same
loader support from x.
Well, for iproute2 I would expect this to be solved by version
dependencies. I.e. iproute2 version X would depend on libbpf version Y+
(like, I dunno, the version of libbpf included in the same kernel source
tree as the kernel version iproute2 is targeting? :)).
This sounds nice in theory, but from what I've seen major (!) distros
already seem to have a hard time releasing kernel x along with iproute2
package x, concrete example was that distro kernel was on 4.13 and its
official iproute2 package on 4.9,
If the iproute2 package is not being updated at all I don't really see
how it would make any difference whether libbpf is vendored or not? :)
adding yet another variable that needs to be in sync with kernel is
simply impractical especially for a _core_ package like iproute2 that
should have as little dependencies as possible. I also don't want to
make a bet on whether libbpf will be available on every distro that
also ships iproute2. Hence approach that pahole (and also bcc by the
way) takes is most reasonable to have the best user experience.
Most users are going to get iproute2 from their distro packages anyway,
so if distros are incompetent at packaging, my bet is that you're going
to run into issues one way or another.
But OK, if you think it is easier to work around bad distros by
vendoring, you guys are the maintainers, so that's up to you. But can we
at least put in the version dependency and let the build system pick up
a system libbpf if it exists and is compatible? That way distros that
*are* competent can still link it dynamically...
Yeah that would be fine by me to use this as a fallback, and I think that
iproute2's configure script should be able to easily handle this situation.
That way we don't compromise on user experience.
Thanks,
Daniel
