bpf: add get_netns_cookie helper to tc programs

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

commit eb62f49
Author: Mahe Tardy <mahe.tardy@gmail.com>
Date:   Mon Oct 7 09:59:57 2024 +0000

    bpf: add get_netns_cookie helper to tc 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/20241007095958.97442-1-mahe.tardy@gmail.com
    Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>

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

Author: jeromemarchand

net/core/filter.c

@@ -5103,6 +5103,17 @@ static u64 __bpf_get_netns_cookie(struct sock *sk)
 	return net->net_cookie;
 }
 
+BPF_CALL_1(bpf_get_netns_cookie, struct sk_buff *, skb)
+{
+	return __bpf_get_netns_cookie(skb && skb->sk ? skb->sk : NULL);
+}
+
+static const struct bpf_func_proto bpf_get_netns_cookie_proto = {
+	.func           = bpf_get_netns_cookie,
+	.ret_type       = RET_INTEGER,
+	.arg1_type      = ARG_PTR_TO_CTX_OR_NULL,
+};
+
 BPF_CALL_1(bpf_get_netns_cookie_sock, struct sock *, ctx)
 {
 	return __bpf_get_netns_cookie(ctx);
@@ -8116,6 +8127,8 @@ tc_cls_act_func_proto(enum bpf_func_id func_id, const struct bpf_prog *prog)
 		return &bpf_skb_under_cgroup_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_fib_lookup: