bpf: Disable non stream socket for strparser

Currently, only TCP supports strparser, but sockmap doesn't intercept
non-TCP connections to attach strparser. For example, with UDP, although
the read/write handlers are replaced, strparser is not executed due to
the lack of a read_sock operation.

Furthermore, in udp_bpf_recvmsg(), it checks whether the psock has data,
and if not, it falls back to the native UDP read interface, making
UDP + strparser appear to read correctly. According to its commit history,
this behavior is unexpected.

Moreover, since UDP lacks the concept of streams, we intercept it directly.

Fixes: 1fa1fe8 ("bpf, sockmap: Test shutdown() correctly exits epoll and recv()=0")
Signed-off-by: Jiayuan Chen <mrpre@163.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Acked-by: Jakub Sitnicki <jakub@cloudflare.com>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://patch.msgid.link/20250122100917.49845-4-mrpre@163.com

Author: mrpre

net/core/sock_map.c

@@ -303,7 +303,10 @@ static int sock_map_link(struct bpf_map *map, struct sock *sk)
 
 	write_lock_bh(&sk->sk_callback_lock);
 	if (stream_parser && stream_verdict && !psock->saved_data_ready) {
-		ret = sk_psock_init_strp(sk, psock);
+		if (sk_is_tcp(sk))
+			ret = sk_psock_init_strp(sk, psock);
+		else
+			ret = -EOPNOTSUPP;
 		if (ret) {
 			write_unlock_bh(&sk->sk_callback_lock);
 			sk_psock_put(sk, psock);