Re: [PATCH] bpf: Replace bpf_lpm_trie_key 0-length array with flexible array

[Kees Cook]

On Thu, Feb 09, 2023 at 08:55:23AM -0800, Alexei Starovoitov wrote:
> On Thu, Feb 9, 2023 at 8:36 AM Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> > This approach is, perhaps, the best way to go? Besides the selftest,
> > what things in userspace consumes struct bpf_lpm_trie_key?
> 
> Plenty of bpf progs use it:
> https://github.com/cilium/cilium/blob/master/bpf/lib/common.h#L352

Thanks for the pointer! Yeah, it seems the "data" member is not
directly used, but is expected to be there for static initializers and
offsetof() use. For example:

cilium:
        struct egress_gw_policy_key in_key = {
                .lpm_key = { 32 + 24, {} },
                .saddr   = CLIENT_IP,
                .daddr   = EXTERNAL_SVC_IP & 0Xffffff,
        };

systemd:
	ipv6_map_fd = bpf_map_new(
			BPF_MAP_TYPE_LPM_TRIE,
			offsetof(struct bpf_lpm_trie_key, data) + sizeof(uint32_t)*4,
			sizeof(uint64_t),
			...

All the others searches in Debian I could find were just copies of UAPI
headers:
https://codesearch.debian.net/search?q=struct+bpf_lpm_trie_key&literal=1&perpkg=1

-- 
Kees Cook