On 3/3/25 2:14 AM, Mahe Tardy wrote:
On Thu, Feb 27, 2025 at 12:32:43PM -0800, Martin KaFai Lau wrote:
On 2/27/25 10:28 AM, Mahe Tardy wrote:
This is needed in the context of Cilium and Tetragon to retrieve netns
cookie from hostns when traffic leaves Pod, so that we can correlate
skb->sk's netns cookie.
Signed-off-by: Mahe Tardy <mahe.tardy@xxxxxxxxx>
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This is a follow-up of c221d3744ad3 ("bpf: add get_netns_cookie helper
to cgroup_skb programs") and eb62f49de7ec ("bpf: add get_netns_cookie
helper to tc programs"), adding this helper respectively to cgroup_skb
and tcx programs.
I looked up a patch doing a similar thing c5dbb89fc2ac ("bpf: Expose
bpf_get_socket_cookie to tracing programs") and there was an item about
"sleepable context". It seems it indeed concerns tracing and LSM progs
from reading 1e6c62a88215 ("bpf: Introduce sleepable BPF programs"). Is
this needed here?
Regarding sleepable, I think the bpf_get_netns_cookie_sock is only reading,
should be fine.
Ok thank you.
The immediate question is whether sock_net(sk) must be non-NULL for tracing.
We discussed this offline with Daniel Borkmann and we think that it
might not be the question. The get_netns_cookie(NULL) call allows us to
compare against get_netns_cookie(sock) to see whether the sock's netns
is equal to the init netns and thus dispatch different logic.
bpf_get_netns_cookie(NULL) should be fine.
I meant to ask if sock_net(sk) may return NULL for a non NULL sk. Please check.
Given we (in Tetragon) historically used tracing programs when no
appropriate network hook was available on older kernels I can foresee
how it can still be useful in such programs.
