bpf, sockmap: Allow inserting listening TCP sockets into sockmap

In order for sockmap/sockhash types to become generic collections for
storing TCP sockets we need to loosen the checks during map update, while
tightening the checks in redirect helpers.

Currently sock{map,hash} require the TCP socket to be in established state,
which prevents inserting listening sockets.

Change the update pre-checks so the socket can also be in listening state.

Since it doesn't make sense to redirect with sock{map,hash} to listening
sockets, add appropriate socket state checks to BPF redirect helpers too.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20200218171023.844439-5-jakub@cloudflare.com

tools/testing/selftests/bpf/test_maps.c

@@ -756,11 +756,7 @@ static void test_sockmap(unsigned int tasks, void *data)
 	/* Test update without programs */
 	for (i = 0; i < 6; i++) {
 		err = bpf_map_update_elem(fd, &i, &sfd[i], BPF_ANY);
-		if (i < 2 && !err) {
-			printf("Allowed update sockmap '%i:%i' not in ESTABLISHED\n",
-			       i, sfd[i]);
-			goto out_sockmap;
-		} else if (i >= 2 && err) {
+		if (err) {
 			printf("Failed noprog update sockmap '%i:%i'\n",
 			       i, sfd[i]);
 			goto out_sockmap;