[bpf-next] bpftool: specify XDP Hints ifname when loading program

  Add ability to specify a network interface used to resolve
XDP Hints kfuncs when loading program through bpftool.

Usage:
bpftool prog load <bpf_obj_path> <pin_path> dev xdpmeta <ifname>

Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
---
 tools/bpf/bpftool/prog.c | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)
  

2023-05-11 17:13 UTC+0200 ~ Larysa Zaremba <larysa.zaremba@intel.com>
> Add ability to specify a network interface used to resolve
> XDP Hints kfuncs when loading program through bpftool.
> 
> Usage:
> bpftool prog load <bpf_obj_path> <pin_path> dev xdpmeta <ifname>

Thanks for this patch!

Regarding the command-line syntax, I'm not a big fan of the optional
sub-keyword for the device for XDP hints. I must admit I had not
anticipated other another use for the "dev" keyword. Instead, have you
considered one of the following:

1) Adding a different keyword ("xdpmeta_dev"?) and making it
incompatible with "dev"

2) Another alternative would be adding a sub-keyword for offload too:

    bpftool p l [...] dev <[offload <ifname> | xdpmeta <ifname>]>

If the ifname is provided with no sub-keyword, we would consider it for
offload for legacy support, possibly warn that the syntax is deprecated.

What do you think?

> 
> Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> ---
>  tools/bpf/bpftool/prog.c | 28 +++++++++++++++++++++-------
>  1 file changed, 21 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> index 91b6075b2db3..a9cb96d99277 100644
> --- a/tools/bpf/bpftool/prog.c
> +++ b/tools/bpf/bpftool/prog.c
> @@ -1517,12 +1517,13 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  	struct bpf_program *prog = NULL, *pos;
>  	unsigned int old_map_fds = 0;
>  	const char *pinmaps = NULL;
> +	__u32 offload_ifindex = 0;
>  	bool auto_attach = false;
> +	__u32 meta_ifindex = 0;
>  	struct bpf_object *obj;
>  	struct bpf_map *map;
>  	const char *pinfile;
>  	unsigned int i, j;
> -	__u32 ifindex = 0;
>  	const char *file;
>  	int idx, err;
>  
> @@ -1614,17 +1615,25 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  			map_replace[old_map_fds].fd = fd;
>  			old_map_fds++;
>  		} else if (is_prefix(*argv, "dev")) {
> +			__u32 *cur_ifindex;
> +
>  			NEXT_ARG();
>  
> -			if (ifindex) {
> -				p_err("offload device already specified");
> +			if (offload_ifindex || meta_ifindex) {
> +				p_err("device already specified");

I'd add a note to tell somehow that offload and XDP hints are mutually
exclusive. I suspect not all users understand these well.

>  				goto err_free_reuse_maps;
>  			}
> +			if (is_prefix(*argv, "xdpmeta")) {
> +				cur_ifindex = &meta_ifindex;
> +				NEXT_ARG();
> +			} else {
> +				cur_ifindex = &offload_ifindex;
> +			}
>  			if (!REQ_ARGS(1))
>  				goto err_free_reuse_maps;
>  
> -			ifindex = if_nametoindex(*argv);
> -			if (!ifindex) {
> +			*cur_ifindex = if_nametoindex(*argv);
> +			if (!(*cur_ifindex)) {
>  				p_err("unrecognized netdevice '%s': %s",
>  				      *argv, strerror(errno));
>  				goto err_free_reuse_maps;
> @@ -1671,7 +1680,12 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  				goto err_close_obj;
>  		}
>  
> -		bpf_program__set_ifindex(pos, ifindex);
> +		if (prog_type == BPF_PROG_TYPE_XDP && meta_ifindex) {
> +			bpf_program__set_flags(pos, BPF_F_XDP_DEV_BOUND_ONLY);
> +			bpf_program__set_ifindex(pos, meta_ifindex);
> +		} else {
> +			bpf_program__set_ifindex(pos, offload_ifindex);
> +		}
>  		if (bpf_program__type(pos) != prog_type)
>  			bpf_program__set_type(pos, prog_type);
>  		bpf_program__set_expected_attach_type(pos, expected_attach_type);
> @@ -1709,7 +1723,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
>  	idx = 0;
>  	bpf_object__for_each_map(map, obj) {
>  		if (bpf_map__type(map) != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
> -			bpf_map__set_ifindex(map, ifindex);
> +			bpf_map__set_ifindex(map, offload_ifindex);
>  
>  		if (j < old_map_fds && idx == map_replace[j].idx) {
>  			err = bpf_map__reuse_fd(map, map_replace[j++].fd);

Could you please also update the following items:

- The usage message for "bpftool prog load" near the end of prog.c

- The related doc in Documentation/bpftool-prog.rst (command summary
near the top, and detailed description later in the doc)

- Bash completion (for keyword "dev", look for "_sysfs_get_netdevs" in
bash-completion/bpftool). I'm happy to help with this one if necessary.

Thanks,
Quentin
  

On Fri, May 12, 2023 at 11:23:00AM +0100, Quentin Monnet wrote:
> 2023-05-11 17:13 UTC+0200 ~ Larysa Zaremba <larysa.zaremba@intel.com>
> > Add ability to specify a network interface used to resolve
> > XDP Hints kfuncs when loading program through bpftool.
> > 
> > Usage:
> > bpftool prog load <bpf_obj_path> <pin_path> dev xdpmeta <ifname>
> 
> Thanks for this patch!
> 
> Regarding the command-line syntax, I'm not a big fan of the optional
> sub-keyword for the device for XDP hints. I must admit I had not
> anticipated other another use for the "dev" keyword. Instead, have you
> considered one of the following:
> 
> 1) Adding a different keyword ("xdpmeta_dev"?) and making it
> incompatible with "dev"
> 
> 2) Another alternative would be adding a sub-keyword for offload too:
> 
>     bpftool p l [...] dev <[offload <ifname> | xdpmeta <ifname>]>
> 
> If the ifname is provided with no sub-keyword, we would consider it for
> offload for legacy support, possibly warn that the syntax is deprecated.
> 
> What do you think?
> 

I think first option would look a little bit nicer, but I like the idea to 
deprecate "dev <ifname>". In my current version, forgetting to add "xdpmeta" 
resulted in not very descriptive errors, this may confuse new users. So what 
about:

bpftool prog load [...] xdpmeta_dev/offload_dev <ifname>

"dev <ifname>" syntax would still work, but with a big warning, like this:

  'bpftool prog [...] dev <ifname>' syntax is deprecated. Going further, please 
  use 'offload_dev <ifname>' to offload program to device. For XDP hints 
  applications, use 'xdpmeta_dev <ifname>'.

> > 
> > Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> > ---
> >  tools/bpf/bpftool/prog.c | 28 +++++++++++++++++++++-------
> >  1 file changed, 21 insertions(+), 7 deletions(-)
> > 
> > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > index 91b6075b2db3..a9cb96d99277 100644
> > --- a/tools/bpf/bpftool/prog.c
> > +++ b/tools/bpf/bpftool/prog.c
> > @@ -1517,12 +1517,13 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >  	struct bpf_program *prog = NULL, *pos;
> >  	unsigned int old_map_fds = 0;
> >  	const char *pinmaps = NULL;
> > +	__u32 offload_ifindex = 0;
> >  	bool auto_attach = false;
> > +	__u32 meta_ifindex = 0;
> >  	struct bpf_object *obj;
> >  	struct bpf_map *map;
> >  	const char *pinfile;
> >  	unsigned int i, j;
> > -	__u32 ifindex = 0;
> >  	const char *file;
> >  	int idx, err;
> >  
> > @@ -1614,17 +1615,25 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >  			map_replace[old_map_fds].fd = fd;
> >  			old_map_fds++;
> >  		} else if (is_prefix(*argv, "dev")) {
> > +			__u32 *cur_ifindex;
> > +
> >  			NEXT_ARG();
> >  
> > -			if (ifindex) {
> > -				p_err("offload device already specified");
> > +			if (offload_ifindex || meta_ifindex) {
> > +				p_err("device already specified");
> 
> I'd add a note to tell somehow that offload and XDP hints are mutually
> exclusive. I suspect not all users understand these well.

Ok, will do.

> 
> >  				goto err_free_reuse_maps;
> >  			}
> > +			if (is_prefix(*argv, "xdpmeta")) {
> > +				cur_ifindex = &meta_ifindex;
> > +				NEXT_ARG();
> > +			} else {
> > +				cur_ifindex = &offload_ifindex;
> > +			}
> >  			if (!REQ_ARGS(1))
> >  				goto err_free_reuse_maps;
> >  
> > -			ifindex = if_nametoindex(*argv);
> > -			if (!ifindex) {
> > +			*cur_ifindex = if_nametoindex(*argv);
> > +			if (!(*cur_ifindex)) {
> >  				p_err("unrecognized netdevice '%s': %s",
> >  				      *argv, strerror(errno));
> >  				goto err_free_reuse_maps;
> > @@ -1671,7 +1680,12 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >  				goto err_close_obj;
> >  		}
> >  
> > -		bpf_program__set_ifindex(pos, ifindex);
> > +		if (prog_type == BPF_PROG_TYPE_XDP && meta_ifindex) {
> > +			bpf_program__set_flags(pos, BPF_F_XDP_DEV_BOUND_ONLY);
> > +			bpf_program__set_ifindex(pos, meta_ifindex);
> > +		} else {
> > +			bpf_program__set_ifindex(pos, offload_ifindex);
> > +		}
> >  		if (bpf_program__type(pos) != prog_type)
> >  			bpf_program__set_type(pos, prog_type);
> >  		bpf_program__set_expected_attach_type(pos, expected_attach_type);
> > @@ -1709,7 +1723,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> >  	idx = 0;
> >  	bpf_object__for_each_map(map, obj) {
> >  		if (bpf_map__type(map) != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
> > -			bpf_map__set_ifindex(map, ifindex);
> > +			bpf_map__set_ifindex(map, offload_ifindex);
> >  
> >  		if (j < old_map_fds && idx == map_replace[j].idx) {
> >  			err = bpf_map__reuse_fd(map, map_replace[j++].fd);
> 
> Could you please also update the following items:
> 
> - The usage message for "bpftool prog load" near the end of prog.c
> 
> - The related doc in Documentation/bpftool-prog.rst (command summary
> near the top, and detailed description later in the doc)
> 
> - Bash completion (for keyword "dev", look for "_sysfs_get_netdevs" in
> bash-completion/bpftool). I'm happy to help with this one if necessary.

Will do all the above in v2.

> 
> Thanks,
> Quentin
  

On 2023-05-12 15:36:47 +0200, Larysa Zaremba wrote:
> [You don't often get email from larysa.zaremba@intel.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
> 
> On Fri, May 12, 2023 at 11:23:00AM +0100, Quentin Monnet wrote:
> > 2023-05-11 17:13 UTC+0200 ~ Larysa Zaremba <larysa.zaremba@intel.com>
> > > Add ability to specify a network interface used to resolve
> > > XDP Hints kfuncs when loading program through bpftool.
> > >
> > > Usage:
> > > bpftool prog load <bpf_obj_path> <pin_path> dev xdpmeta <ifname>
> >
> > Thanks for this patch!
> >
> > Regarding the command-line syntax, I'm not a big fan of the optional
> > sub-keyword for the device for XDP hints. I must admit I had not
> > anticipated other another use for the "dev" keyword. Instead, have you
> > considered one of the following:
> >
> > 1) Adding a different keyword ("xdpmeta_dev"?) and making it
> > incompatible with "dev"
> >
> > 2) Another alternative would be adding a sub-keyword for offload too:
> >
> >     bpftool p l [...] dev <[offload <ifname> | xdpmeta <ifname>]>
> >
> > If the ifname is provided with no sub-keyword, we would consider it for
> > offload for legacy support, possibly warn that the syntax is deprecated.
> >
> > What do you think?
> >
> 
> I think first option would look a little bit nicer, but I like the idea to
> deprecate "dev <ifname>". In my current version, forgetting to add "xdpmeta"
> resulted in not very descriptive errors, this may confuse new users. So what
> about:

I agree the first option looks a little bit nicer, but I think both 
options would work.

> 
> bpftool prog load [...] xdpmeta_dev/offload_dev <ifname>
> 
> "dev <ifname>" syntax would still work, but with a big warning, like this:
> 
>   'bpftool prog [...] dev <ifname>' syntax is deprecated. Going further, please
>   use 'offload_dev <ifname>' to offload program to device. For XDP hints
>   applications, use 'xdpmeta_dev <ifname>'.
> 
> > >
> > > Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
> > > ---
> > >  tools/bpf/bpftool/prog.c | 28 +++++++++++++++++++++-------
> > >  1 file changed, 21 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
> > > index 91b6075b2db3..a9cb96d99277 100644
> > > --- a/tools/bpf/bpftool/prog.c
> > > +++ b/tools/bpf/bpftool/prog.c
> > > @@ -1517,12 +1517,13 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > >     struct bpf_program *prog = NULL, *pos;
> > >     unsigned int old_map_fds = 0;
> > >     const char *pinmaps = NULL;
> > > +   __u32 offload_ifindex = 0;
> > >     bool auto_attach = false;
> > > +   __u32 meta_ifindex = 0;
> > >     struct bpf_object *obj;
> > >     struct bpf_map *map;
> > >     const char *pinfile;
> > >     unsigned int i, j;
> > > -   __u32 ifindex = 0;
> > >     const char *file;
> > >     int idx, err;
> > >
> > > @@ -1614,17 +1615,25 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > >                     map_replace[old_map_fds].fd = fd;
> > >                     old_map_fds++;
> > >             } else if (is_prefix(*argv, "dev")) {
> > > +                   __u32 *cur_ifindex;
> > > +
> > >                     NEXT_ARG();
> > >
> > > -                   if (ifindex) {
> > > -                           p_err("offload device already specified");
> > > +                   if (offload_ifindex || meta_ifindex) {
> > > +                           p_err("device already specified");
> >
> > I'd add a note to tell somehow that offload and XDP hints are mutually
> > exclusive. I suspect not all users understand these well.
> 
> Ok, will do.
> 
> >
> > >                             goto err_free_reuse_maps;
> > >                     }
> > > +                   if (is_prefix(*argv, "xdpmeta")) {
> > > +                           cur_ifindex = &meta_ifindex;
> > > +                           NEXT_ARG();
> > > +                   } else {
> > > +                           cur_ifindex = &offload_ifindex;
> > > +                   }
> > >                     if (!REQ_ARGS(1))
> > >                             goto err_free_reuse_maps;
> > >
> > > -                   ifindex = if_nametoindex(*argv);
> > > -                   if (!ifindex) {
> > > +                   *cur_ifindex = if_nametoindex(*argv);
> > > +                   if (!(*cur_ifindex)) {
> > >                             p_err("unrecognized netdevice '%s': %s",
> > >                                   *argv, strerror(errno));
> > >                             goto err_free_reuse_maps;
> > > @@ -1671,7 +1680,12 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > >                             goto err_close_obj;
> > >             }
> > >
> > > -           bpf_program__set_ifindex(pos, ifindex);
> > > +           if (prog_type == BPF_PROG_TYPE_XDP && meta_ifindex) {
> > > +                   bpf_program__set_flags(pos, BPF_F_XDP_DEV_BOUND_ONLY);
> > > +                   bpf_program__set_ifindex(pos, meta_ifindex);
> > > +           } else {
> > > +                   bpf_program__set_ifindex(pos, offload_ifindex);
> > > +           }
> > >             if (bpf_program__type(pos) != prog_type)
> > >                     bpf_program__set_type(pos, prog_type);
> > >             bpf_program__set_expected_attach_type(pos, expected_attach_type);
> > > @@ -1709,7 +1723,7 @@ static int load_with_options(int argc, char **argv, bool first_prog_only)
> > >     idx = 0;
> > >     bpf_object__for_each_map(map, obj) {
> > >             if (bpf_map__type(map) != BPF_MAP_TYPE_PERF_EVENT_ARRAY)
> > > -                   bpf_map__set_ifindex(map, ifindex);
> > > +                   bpf_map__set_ifindex(map, offload_ifindex);
> > >
> > >             if (j < old_map_fds && idx == map_replace[j].idx) {
> > >                     err = bpf_map__reuse_fd(map, map_replace[j++].fd);
> >
> > Could you please also update the following items:
> >
> > - The usage message for "bpftool prog load" near the end of prog.c
> >
> > - The related doc in Documentation/bpftool-prog.rst (command summary
> > near the top, and detailed description later in the doc)
> >
> > - Bash completion (for keyword "dev", look for "_sysfs_get_netdevs" in
> > bash-completion/bpftool). I'm happy to help with this one if necessary.
> 
> Will do all the above in v2.
> 
> >
> > Thanks,
> > Quentin
  

2023-05-15 18:30 UTC+0200 ~ Niklas Söderlund <niklas.soderlund@corigine.com>
> On 2023-05-12 15:36:47 +0200, Larysa Zaremba wrote:
>> [You don't often get email from larysa.zaremba@intel.com. Learn why this is important at https://aka.ms/LearnAboutSenderIdentification ]
>>
>> On Fri, May 12, 2023 at 11:23:00AM +0100, Quentin Monnet wrote:
>>> 2023-05-11 17:13 UTC+0200 ~ Larysa Zaremba <larysa.zaremba@intel.com>
>>>> Add ability to specify a network interface used to resolve
>>>> XDP Hints kfuncs when loading program through bpftool.
>>>>
>>>> Usage:
>>>> bpftool prog load <bpf_obj_path> <pin_path> dev xdpmeta <ifname>
>>>
>>> Thanks for this patch!
>>>
>>> Regarding the command-line syntax, I'm not a big fan of the optional
>>> sub-keyword for the device for XDP hints. I must admit I had not
>>> anticipated other another use for the "dev" keyword. Instead, have you
>>> considered one of the following:
>>>
>>> 1) Adding a different keyword ("xdpmeta_dev"?) and making it
>>> incompatible with "dev"
>>>
>>> 2) Another alternative would be adding a sub-keyword for offload too:
>>>
>>>     bpftool p l [...] dev <[offload <ifname> | xdpmeta <ifname>]>
>>>
>>> If the ifname is provided with no sub-keyword, we would consider it for
>>> offload for legacy support, possibly warn that the syntax is deprecated.
>>>
>>> What do you think?
>>>
>>
>> I think first option would look a little bit nicer, but I like the idea to
>> deprecate "dev <ifname>". In my current version, forgetting to add "xdpmeta"
>> resulted in not very descriptive errors, this may confuse new users. So what
>> about:
> 
> I agree the first option looks a little bit nicer, but I think both 
> options would work.
> 
>>
>> bpftool prog load [...] xdpmeta_dev/offload_dev <ifname>
>>
>> "dev <ifname>" syntax would still work, but with a big warning, like this:
>>
>>   'bpftool prog [...] dev <ifname>' syntax is deprecated. Going further, please
>>   use 'offload_dev <ifname>' to offload program to device. For XDP hints
>>   applications, use 'xdpmeta_dev <ifname>'.

OK let's go with this

Thanks,
Quentin