[PATCH bpf-next 0/3] bpftool: Switch to independent versioning scheme

[PATCH bpf-next 0/3] bpftool: Switch to independent versioning scheme

[Quentin Monnet]

Hi, this set aims at updating the way bpftool versions are numbered.
Instead of copying the version from the kernel (given that the sources for
the kernel and bpftool are shipped together), introduce an independent
versioning scheme. We start at v6.0.0 - incrementing the major version
number - and the idea is to update this number from time to time, as new
features or bug fixes make their way into bpftool. Please refer to the
description of the third commit for details on the motivations.

The patchset also adds the number of the version of libbpf that was used to
compile to the output of "bpftool version".

Quentin Monnet (3):
  libbpf: Add "libbpversion" make target to print version
  bpftool: Add libbpf's version number to "bpftool version" output
  bpftool: Update versioning scheme

 tools/bpf/bpftool/Documentation/common_options.rst | 3 ++-
 tools/bpf/bpftool/Makefile                         | 7 ++++---
 tools/bpf/bpftool/main.c                           | 3 +++
 tools/lib/bpf/Makefile                             | 3 +++
 4 files changed, 12 insertions(+), 4 deletions(-)

-- 
2.32.0

[PATCH bpf-next 1/3] libbpf: Add "libbpversion" make target to print version

[Quentin Monnet]

Add a target to libbpf's Makefile to print its version number, in a
similar way to what running "make kernelversion" at the root of the
repository does.

This is to avoid re-implementing the parsing of the libbpf.map file in
case some other tools want to extract the version of the libbpf sources
they are using.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/lib/bpf/Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/tools/lib/bpf/Makefile b/tools/lib/bpf/Makefile
index f947b61b2107..e3a1ae7efa33 100644
--- a/tools/lib/bpf/Makefile
+++ b/tools/lib/bpf/Makefile
@@ -108,6 +108,9 @@ MAKEOVERRIDES=
 
 all:
 
+libbpfversion:
+	@echo $(LIBBPF_VERSION)
+
 export srctree OUTPUT CC LD CFLAGS V
 include $(srctree)/tools/build/Makefile.include
 
-- 
2.32.0

[PATCH bpf-next 2/3] bpftool: Add libbpf's version number to "bpftool version" output

[Quentin Monnet]

To help users check what version of libbpf has been used to compile
bpftool, embed the version number and print it along with bpftool's own
version number.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/bpf/bpftool/Documentation/common_options.rst | 3 ++-
 tools/bpf/bpftool/Makefile                         | 2 ++
 tools/bpf/bpftool/main.c                           | 3 +++
 3 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/tools/bpf/bpftool/Documentation/common_options.rst b/tools/bpf/bpftool/Documentation/common_options.rst
index 908487b9c2ad..24166733d3ae 100644
--- a/tools/bpf/bpftool/Documentation/common_options.rst
+++ b/tools/bpf/bpftool/Documentation/common_options.rst
@@ -4,7 +4,8 @@
 	  Print short help message (similar to **bpftool help**).
 
 -V, --version
-	  Print version number (similar to **bpftool version**), and optional
+	  Print bpftool's version number (similar to **bpftool version**), the
+	  version of libbpf that was used to compile the binary, and optional
 	  features that were included when bpftool was compiled. Optional
 	  features include linking against libbfd to provide the disassembler
 	  for JIT-ted programs (**bpftool prog dump jited**) and usage of BPF
diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index 83369f55df61..bd5a8cafac49 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -42,6 +42,7 @@ LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hash
 ifeq ($(BPFTOOL_VERSION),)
 BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
 endif
+LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
 
 $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
 	$(QUIET_MKDIR)mkdir -p $@
@@ -84,6 +85,7 @@ CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
 	-I$(srctree)/tools/include \
 	-I$(srctree)/tools/include/uapi
 CFLAGS += -DBPFTOOL_VERSION='"$(BPFTOOL_VERSION)"'
+CFLAGS += -DLIBBPF_VERSION='"$(LIBBPF_VERSION)"'
 ifneq ($(EXTRA_CFLAGS),)
 CFLAGS += $(EXTRA_CFLAGS)
 endif
diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
index 9d01fa9de033..4bda73057980 100644
--- a/tools/bpf/bpftool/main.c
+++ b/tools/bpf/bpftool/main.c
@@ -89,6 +89,8 @@ static int do_version(int argc, char **argv)
 
 		jsonw_name(json_wtr, "version");
 		jsonw_printf(json_wtr, "\"%s\"", BPFTOOL_VERSION);
+		jsonw_name(json_wtr, "libbpf_version");
+		jsonw_printf(json_wtr, "\"%s\"", LIBBPF_VERSION);
 
 		jsonw_name(json_wtr, "features");
 		jsonw_start_object(json_wtr);	/* features */
@@ -102,6 +104,7 @@ static int do_version(int argc, char **argv)
 		unsigned int nb_features = 0;
 
 		printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
+		printf("using libbpf v%s\n", LIBBPF_VERSION);
 		printf("features:");
 		if (has_libbfd) {
 			printf(" libbfd");
-- 
2.32.0

[PATCH bpf-next 3/3] bpftool: Update versioning scheme

[Quentin Monnet]

Since the notion of versions was introduced for bpftool, it has been
following the version number of the kernel (using the version number
corresponding to the tree in which bpftool's sources are located). The
rationale was that bpftool's features are loosely tied to BPF features
in the kernel, and that we could defer versioning to the kernel
repository itself.

But this versioning scheme is confusing today, because a bpftool binary
should be able to work with both older and newer kernels, even if some
of its recent features won't be available on older systems. Furthermore,
if bpftool is ported to other systems in the future, keeping a
Linux-based version number is not a good option.

It would make more sense to align bpftool's number on libbpf, maybe.
When versioning was introduced in bpftool, libbpf was in its initial
phase at v0.0.1. Now it moves faster, with regular version bumps. But
there are two issues if we want to pick the same numbers. First, that
would mean going backward on the numbering, and will be a huge pain for
every script trying to determine which bpftool binary is the most
recent (not to mention some possible overlap of the numbers in a distant
future). Then, bpftool could get new features or bug fixes between two
versions libbpf, so maybe we should not completely tie its versions to
libbpf, either.

Therefore, this commit introduces an independent versioning scheme for
bpftool. The new version is v6.0.0, with its major number incremented
over the current 5.16.* returned from the kernel's Makefile. The plan is
to update this new number from time to time when bpftool gets new
features or new bug fixes. These updates could possibly lead to new
releases being tagged on the recently created out-of-tree mirror, at
https://github.com/libbpf/bpftool.

Version number is moved higher in the Makefile, to make it more visible.

Suggested-by: Andrii Nakryiko <andrii@kernel.org>
Signed-off-by: Quentin Monnet <quentin@isovalent.com>
---
 tools/bpf/bpftool/Makefile | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
index bd5a8cafac49..b7dbdea112d3 100644
--- a/tools/bpf/bpftool/Makefile
+++ b/tools/bpf/bpftool/Makefile
@@ -1,6 +1,8 @@
 # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
 include ../../scripts/Makefile.include
 
+BPFTOOL_VERSION := 6.0.0
+
 ifeq ($(srctree),)
 srctree := $(patsubst %/,%,$(dir $(CURDIR)))
 srctree := $(patsubst %/,%,$(dir $(srctree)))
@@ -39,9 +41,6 @@ LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
 LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h)
 LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hashmap.h)
 
-ifeq ($(BPFTOOL_VERSION),)
-BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
-endif
 LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
 
 $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
-- 
2.32.0

Re: [PATCH bpf-next 2/3] bpftool: Add libbpf's version number to "bpftool version" output

[Andrii Nakryiko]

On Mon, Jan 31, 2022 at 1:11 PM Quentin Monnet <quentin@isovalent.com> wrote:
>
> To help users check what version of libbpf has been used to compile
> bpftool, embed the version number and print it along with bpftool's own
> version number.
>
> Signed-off-by: Quentin Monnet <quentin@isovalent.com>
> ---
>  tools/bpf/bpftool/Documentation/common_options.rst | 3 ++-
>  tools/bpf/bpftool/Makefile                         | 2 ++
>  tools/bpf/bpftool/main.c                           | 3 +++
>  3 files changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/tools/bpf/bpftool/Documentation/common_options.rst b/tools/bpf/bpftool/Documentation/common_options.rst
> index 908487b9c2ad..24166733d3ae 100644
> --- a/tools/bpf/bpftool/Documentation/common_options.rst
> +++ b/tools/bpf/bpftool/Documentation/common_options.rst
> @@ -4,7 +4,8 @@
>           Print short help message (similar to **bpftool help**).
>
>  -V, --version
> -         Print version number (similar to **bpftool version**), and optional
> +         Print bpftool's version number (similar to **bpftool version**), the
> +         version of libbpf that was used to compile the binary, and optional
>           features that were included when bpftool was compiled. Optional
>           features include linking against libbfd to provide the disassembler
>           for JIT-ted programs (**bpftool prog dump jited**) and usage of BPF
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index 83369f55df61..bd5a8cafac49 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -42,6 +42,7 @@ LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hash
>  ifeq ($(BPFTOOL_VERSION),)
>  BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
>  endif
> +LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
>

why can't you use libbpf_version_string() API instead?



>  $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
>         $(QUIET_MKDIR)mkdir -p $@
> @@ -84,6 +85,7 @@ CFLAGS += -DPACKAGE='"bpftool"' -D__EXPORTED_HEADERS__ \
>         -I$(srctree)/tools/include \
>         -I$(srctree)/tools/include/uapi
>  CFLAGS += -DBPFTOOL_VERSION='"$(BPFTOOL_VERSION)"'
> +CFLAGS += -DLIBBPF_VERSION='"$(LIBBPF_VERSION)"'
>  ifneq ($(EXTRA_CFLAGS),)
>  CFLAGS += $(EXTRA_CFLAGS)
>  endif
> diff --git a/tools/bpf/bpftool/main.c b/tools/bpf/bpftool/main.c
> index 9d01fa9de033..4bda73057980 100644
> --- a/tools/bpf/bpftool/main.c
> +++ b/tools/bpf/bpftool/main.c
> @@ -89,6 +89,8 @@ static int do_version(int argc, char **argv)
>
>                 jsonw_name(json_wtr, "version");
>                 jsonw_printf(json_wtr, "\"%s\"", BPFTOOL_VERSION);
> +               jsonw_name(json_wtr, "libbpf_version");
> +               jsonw_printf(json_wtr, "\"%s\"", LIBBPF_VERSION);
>
>                 jsonw_name(json_wtr, "features");
>                 jsonw_start_object(json_wtr);   /* features */
> @@ -102,6 +104,7 @@ static int do_version(int argc, char **argv)
>                 unsigned int nb_features = 0;
>
>                 printf("%s v%s\n", bin_name, BPFTOOL_VERSION);
> +               printf("using libbpf v%s\n", LIBBPF_VERSION);
>                 printf("features:");
>                 if (has_libbfd) {
>                         printf(" libbfd");
> --
> 2.32.0
>

Re: [PATCH bpf-next 3/3] bpftool: Update versioning scheme

[Andrii Nakryiko]

On Mon, Jan 31, 2022 at 1:11 PM Quentin Monnet <quentin@isovalent.com> wrote:
>
> Since the notion of versions was introduced for bpftool, it has been
> following the version number of the kernel (using the version number
> corresponding to the tree in which bpftool's sources are located). The
> rationale was that bpftool's features are loosely tied to BPF features
> in the kernel, and that we could defer versioning to the kernel
> repository itself.
>
> But this versioning scheme is confusing today, because a bpftool binary
> should be able to work with both older and newer kernels, even if some
> of its recent features won't be available on older systems. Furthermore,
> if bpftool is ported to other systems in the future, keeping a
> Linux-based version number is not a good option.
>
> It would make more sense to align bpftool's number on libbpf, maybe.
> When versioning was introduced in bpftool, libbpf was in its initial
> phase at v0.0.1. Now it moves faster, with regular version bumps. But
> there are two issues if we want to pick the same numbers. First, that
> would mean going backward on the numbering, and will be a huge pain for
> every script trying to determine which bpftool binary is the most
> recent (not to mention some possible overlap of the numbers in a distant
> future). Then, bpftool could get new features or bug fixes between two
> versions libbpf, so maybe we should not completely tie its versions to
> libbpf, either.
>
> Therefore, this commit introduces an independent versioning scheme for
> bpftool. The new version is v6.0.0, with its major number incremented
> over the current 5.16.* returned from the kernel's Makefile. The plan is
> to update this new number from time to time when bpftool gets new
> features or new bug fixes. These updates could possibly lead to new
> releases being tagged on the recently created out-of-tree mirror, at
> https://github.com/libbpf/bpftool.
>
> Version number is moved higher in the Makefile, to make it more visible.
>
> Suggested-by: Andrii Nakryiko <andrii@kernel.org>
> Signed-off-by: Quentin Monnet <quentin@isovalent.com>
> ---
>  tools/bpf/bpftool/Makefile | 5 ++---
>  1 file changed, 2 insertions(+), 3 deletions(-)
>
> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
> index bd5a8cafac49..b7dbdea112d3 100644
> --- a/tools/bpf/bpftool/Makefile
> +++ b/tools/bpf/bpftool/Makefile
> @@ -1,6 +1,8 @@
>  # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>  include ../../scripts/Makefile.include
>
> +BPFTOOL_VERSION := 6.0.0
> +

It's going to be a PITA to not forget to update this :( As discussed,
I'm fine with this, but I also recalled the versioning approach that
libbpf-sys library is using (see [0]). Maybe we could steal some of
those ideas. As in, base bpftool version on libbpf (with major version
+ 6 as you do here), but also have "-1", "-2", etc suffixes for
bpftool releases for when libbpf version didn't change. Don't know,
just throwing out the idea for your consideration.

  [0] https://github.com/libbpf/libbpf-sys#versioning


>  ifeq ($(srctree),)
>  srctree := $(patsubst %/,%,$(dir $(CURDIR)))
>  srctree := $(patsubst %/,%,$(dir $(srctree)))
> @@ -39,9 +41,6 @@ LIBBPF_BOOTSTRAP := $(LIBBPF_BOOTSTRAP_OUTPUT)libbpf.a
>  LIBBPF_INTERNAL_HDRS := $(addprefix $(LIBBPF_HDRS_DIR)/,hashmap.h nlattr.h)
>  LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hashmap.h)
>
> -ifeq ($(BPFTOOL_VERSION),)
> -BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
> -endif
>  LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
>
>  $(LIBBPF_OUTPUT) $(BOOTSTRAP_OUTPUT) $(LIBBPF_BOOTSTRAP_OUTPUT) $(LIBBPF_HDRS_DIR) $(LIBBPF_BOOTSTRAP_HDRS_DIR):
> --
> 2.32.0
>

Re: [PATCH bpf-next 2/3] bpftool: Add libbpf's version number to "bpftool version" output

[Quentin Monnet]

2022-02-01 22:59 UTC-0800 ~ Andrii Nakryiko <andrii.nakryiko@gmail.com>
> On Mon, Jan 31, 2022 at 1:11 PM Quentin Monnet <quentin@isovalent.com> wrote:
>>
>> To help users check what version of libbpf has been used to compile
>> bpftool, embed the version number and print it along with bpftool's own
>> version number.
>>
>> Signed-off-by: Quentin Monnet <quentin@isovalent.com>
>> ---
>>  tools/bpf/bpftool/Documentation/common_options.rst | 3 ++-
>>  tools/bpf/bpftool/Makefile                         | 2 ++
>>  tools/bpf/bpftool/main.c                           | 3 +++
>>  3 files changed, 7 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/bpf/bpftool/Documentation/common_options.rst b/tools/bpf/bpftool/Documentation/common_options.rst
>> index 908487b9c2ad..24166733d3ae 100644
>> --- a/tools/bpf/bpftool/Documentation/common_options.rst
>> +++ b/tools/bpf/bpftool/Documentation/common_options.rst
>> @@ -4,7 +4,8 @@
>>           Print short help message (similar to **bpftool help**).
>>
>>  -V, --version
>> -         Print version number (similar to **bpftool version**), and optional
>> +         Print bpftool's version number (similar to **bpftool version**), the
>> +         version of libbpf that was used to compile the binary, and optional
>>           features that were included when bpftool was compiled. Optional
>>           features include linking against libbfd to provide the disassembler
>>           for JIT-ted programs (**bpftool prog dump jited**) and usage of BPF
>> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
>> index 83369f55df61..bd5a8cafac49 100644
>> --- a/tools/bpf/bpftool/Makefile
>> +++ b/tools/bpf/bpftool/Makefile
>> @@ -42,6 +42,7 @@ LIBBPF_BOOTSTRAP_INTERNAL_HDRS := $(addprefix $(LIBBPF_BOOTSTRAP_HDRS_DIR)/,hash
>>  ifeq ($(BPFTOOL_VERSION),)
>>  BPFTOOL_VERSION := $(shell make -rR --no-print-directory -sC ../../.. kernelversion)
>>  endif
>> +LIBBPF_VERSION := $(shell make -r --no-print-directory -sC $(BPF_DIR) libbpfversion)
>>
> 
> why can't you use libbpf_version_string() API instead?

I missed it somehow, thanks for the pointer. It seems to be a recent
addition to libbpf, and it was probably not present last time I checked
for such an API. I'll use it.

Re: [PATCH bpf-next 3/3] bpftool: Update versioning scheme

[Quentin Monnet]

2022-02-01 22:59 UTC-0800 ~ Andrii Nakryiko <andrii.nakryiko@gmail.com>
> On Mon, Jan 31, 2022 at 1:11 PM Quentin Monnet <quentin@isovalent.com> wrote:
>>
>> Since the notion of versions was introduced for bpftool, it has been
>> following the version number of the kernel (using the version number
>> corresponding to the tree in which bpftool's sources are located). The
>> rationale was that bpftool's features are loosely tied to BPF features
>> in the kernel, and that we could defer versioning to the kernel
>> repository itself.
>>
>> But this versioning scheme is confusing today, because a bpftool binary
>> should be able to work with both older and newer kernels, even if some
>> of its recent features won't be available on older systems. Furthermore,
>> if bpftool is ported to other systems in the future, keeping a
>> Linux-based version number is not a good option.
>>
>> It would make more sense to align bpftool's number on libbpf, maybe.
>> When versioning was introduced in bpftool, libbpf was in its initial
>> phase at v0.0.1. Now it moves faster, with regular version bumps. But
>> there are two issues if we want to pick the same numbers. First, that
>> would mean going backward on the numbering, and will be a huge pain for
>> every script trying to determine which bpftool binary is the most
>> recent (not to mention some possible overlap of the numbers in a distant
>> future). Then, bpftool could get new features or bug fixes between two
>> versions libbpf, so maybe we should not completely tie its versions to
>> libbpf, either.
>>
>> Therefore, this commit introduces an independent versioning scheme for
>> bpftool. The new version is v6.0.0, with its major number incremented
>> over the current 5.16.* returned from the kernel's Makefile. The plan is
>> to update this new number from time to time when bpftool gets new
>> features or new bug fixes. These updates could possibly lead to new
>> releases being tagged on the recently created out-of-tree mirror, at
>> https://github.com/libbpf/bpftool.
>>
>> Version number is moved higher in the Makefile, to make it more visible.
>>
>> Suggested-by: Andrii Nakryiko <andrii@kernel.org>
>> Signed-off-by: Quentin Monnet <quentin@isovalent.com>
>> ---
>>  tools/bpf/bpftool/Makefile | 5 ++---
>>  1 file changed, 2 insertions(+), 3 deletions(-)
>>
>> diff --git a/tools/bpf/bpftool/Makefile b/tools/bpf/bpftool/Makefile
>> index bd5a8cafac49..b7dbdea112d3 100644
>> --- a/tools/bpf/bpftool/Makefile
>> +++ b/tools/bpf/bpftool/Makefile
>> @@ -1,6 +1,8 @@
>>  # SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
>>  include ../../scripts/Makefile.include
>>
>> +BPFTOOL_VERSION := 6.0.0
>> +
> 
> It's going to be a PITA to not forget to update this :( As discussed,
> I'm fine with this, but I also recalled the versioning approach that
> libbpf-sys library is using (see [0]). Maybe we could steal some of
> those ideas. As in, base bpftool version on libbpf (with major version
> + 6 as you do here), but also have "-1", "-2", etc suffixes for
> bpftool releases for when libbpf version didn't change. Don't know,
> just throwing out the idea for your consideration.
> 
>   [0] https://github.com/libbpf/libbpf-sys#versioning

I've been somewhat torn between having a separate versioning scheme and
getting as much flexibility as we want, and aligning on libbpf and
having “automatic” version updates. My reasoning is the following.

If aligning on libbpf:

- We may want bpftool releases in-between two libbpf versions. Using
pre-release numbers for tagging them is a good idea, although I don't
know if something marked as a pre-release will look “official” enough
(users may not pick it, thinking it's a beta release?). On the other
hand, having bpftool with version numbers that look “official” haven't
really been an issue so far.

- If no new feature lands in bpftool for some time, we may move from
e.g. 6.7.0 to 6.8.0 when libbpf levels up and have two different
versions which are in fact the same.

- Following libbpf's versioning scheme sounds better than kernel's, but
ultimately it doesn't make too much sense either, because even though
bpftool uses the lib a lot, its behaviour is not that much conditioned
by the internal evolution of the library (or by new APIs that it may not
use).

Having an independent versioning scheme solves the above, but as you
say, it's gonna be painful to update the numbers. Developers will miss
it most of the time, and I'm not even exactly sure myself of when to tag
a new minor release. I suppose it would be a bit like for docs and
completion, with occasional “catch-up” patches to update the version
number - not great.

Based on all the above, I think your suggestion is good, and I'll switch
back to aligning on libbpf's version. It may not be perfect, but 1) it's
certainly an improvement over the current scheme, 2) the issues raised
above are minor at the moment, and 3) we can still move to an
independent scheme in the future if we realise we need it. Sounds more
important to save on the maintenance burden at the moment. I'll send a
new version shortly.

Thanks,
Quentin