bpf: add get_netns_cookie helper to cgroup_skb programs

JIRA: https://issues.redhat.com/browse/RHEL-110279

commit c221d37
Author: Mahe Tardy <mahe.tardy@gmail.com>
Date:   Tue Feb 25 12:50:30 2025 +0000

    bpf: add get_netns_cookie helper to cgroup_skb programs

    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@gmail.com>
    Link: https://lore.kernel.org/r/20250225125031.258740-1-mahe.tardy@gmail.com
    Signed-off-by: Alexei Starovoitov <ast@kernel.org>

Signed-off-by: Jerome Marchand <jmarchan@redhat.com>

Author: jeromemarchand

net/core/filter.c

@@ -7996,6 +7996,8 @@ sk_filter_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_skb_load_bytes_relative_proto;
 	case BPF_FUNC_get_socket_cookie:
 		return &bpf_get_socket_cookie_proto;
+	case BPF_FUNC_get_netns_cookie:
+		return &bpf_get_netns_cookie_proto;
 	case BPF_FUNC_get_socket_uid:
 		return &bpf_get_socket_uid_proto;
 	case BPF_FUNC_perf_event_output: