On Thu, Jul 9, 2020 at 5:49 AM Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> wrote: > > On Thu, Jul 09, 2020 at 05:44 AM CEST, Andrii Nakryiko wrote: > > On Thu, Jul 2, 2020 at 2:24 AM Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> wrote: > >> > >> Extend the BPF netns link callbacks to rebuild (grow/shrink) or update the > >> prog_array at given position when link gets attached/updated/released. > >> > >> This let's us lift the limit of having just one link attached for the new > >> attach type introduced by subsequent patch. > >> > >> No functional changes intended. > >> > >> Signed-off-by: Jakub Sitnicki <jakub@xxxxxxxxxxxxxx> > >> --- > >> > >> Notes: > >> v3: > >> - New in v3 to support multi-prog attachments. (Alexei) > >> > >> include/linux/bpf.h | 4 ++ > >> kernel/bpf/core.c | 22 ++++++++++ > >> kernel/bpf/net_namespace.c | 88 +++++++++++++++++++++++++++++++++++--- > >> 3 files changed, 107 insertions(+), 7 deletions(-) > >> > >> diff --git a/include/linux/bpf.h b/include/linux/bpf.h > >> index 3d2ade703a35..26bc70533db0 100644 > >> --- a/include/linux/bpf.h > >> +++ b/include/linux/bpf.h > >> @@ -928,6 +928,10 @@ int bpf_prog_array_copy_to_user(struct bpf_prog_array *progs, > >> > >> void bpf_prog_array_delete_safe(struct bpf_prog_array *progs, > >> struct bpf_prog *old_prog); > >> +void bpf_prog_array_delete_safe_at(struct bpf_prog_array *array, > >> + unsigned int index); > >> +void bpf_prog_array_update_at(struct bpf_prog_array *array, unsigned int index, > >> + struct bpf_prog *prog); > >> int bpf_prog_array_copy_info(struct bpf_prog_array *array, > >> u32 *prog_ids, u32 request_cnt, > >> u32 *prog_cnt); > >> diff --git a/kernel/bpf/core.c b/kernel/bpf/core.c > >> index 9df4cc9a2907..d4b3b9ee6bf1 100644 > >> --- a/kernel/bpf/core.c > >> +++ b/kernel/bpf/core.c > >> @@ -1958,6 +1958,28 @@ void bpf_prog_array_delete_safe(struct bpf_prog_array *array, > >> } > >> } > >> > >> +void bpf_prog_array_delete_safe_at(struct bpf_prog_array *array, > >> + unsigned int index) > >> +{ > >> + bpf_prog_array_update_at(array, index, &dummy_bpf_prog.prog); > >> +} > >> + > >> +void bpf_prog_array_update_at(struct bpf_prog_array *array, unsigned int index, > >> + struct bpf_prog *prog) > > > > it's a good idea to mention it in a comment for both delete_safe_at > > and update_at that slots with dummy entries are ignored. > > I agree. These two need doc comments. update_at doesn't event hint that > this is not a regular update operation. Will add in v4. > > > > > Also, given that index can be out of bounds, should these functions > > actually return error if the slot is not found? > > That won't hurt. I mean, from bpf-netns PoV getting such an error would > indicate that there is a bug in the code that manages prog_array. But > perhaps other future users of this new prog_array API can benefit. > > > > >> +{ > >> + struct bpf_prog_array_item *item; > >> + > >> + for (item = array->items; item->prog; item++) { > >> + if (item->prog == &dummy_bpf_prog.prog) > >> + continue; > >> + if (!index) { > >> + WRITE_ONCE(item->prog, prog); > >> + break; > >> + } > >> + index--; > >> + } > >> +} > >> + > >> int bpf_prog_array_copy(struct bpf_prog_array *old_array, > >> struct bpf_prog *exclude_prog, > >> struct bpf_prog *include_prog, > >> diff --git a/kernel/bpf/net_namespace.c b/kernel/bpf/net_namespace.c > >> index 247543380fa6..6011122c35b6 100644 > >> --- a/kernel/bpf/net_namespace.c > >> +++ b/kernel/bpf/net_namespace.c > >> @@ -36,11 +36,51 @@ static void netns_bpf_run_array_detach(struct net *net, > >> bpf_prog_array_free(run_array); > >> } > >> > >> +static unsigned int link_index(struct net *net, > >> + enum netns_bpf_attach_type type, > >> + struct bpf_netns_link *link) > >> +{ > >> + struct bpf_netns_link *pos; > >> + unsigned int i = 0; > >> + > >> + list_for_each_entry(pos, &net->bpf.links[type], node) { > >> + if (pos == link) > >> + return i; > >> + i++; > >> + } > >> + return UINT_MAX; > > > > Why not return a negative error, if the slot is not found? Feels a bit > > unusual as far as error reporting goes. > > Returning uint played well with the consumer of link_index() return > value, that is bpf_prog_array_update_at(). update at takes an index into > the array, which must not be negative. Yeah, it did, but it's also quite implicit. I think just doing BUG_ON() for update_at or delete_at would be good enough there. > > But I don't have strong feelings toward it. Will switch to -ENOENT in > v4. > > > > >> +} > >> + > > > > [...]