bpf: Support bpf_(get|set)sockopt() in bpf unix iter.

This patch makes bpf_(get|set)sockopt() available when iterating AF_UNIX
sockets.
Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
Link: https://lore.kernel.org/r/20220113002849.4384-4-kuniyu@amazon.co.jpSigned-off-by: Alexei Starovoitov <ast@kernel.org>

net/unix/af_unix.c

@@ -3633,6 +3633,20 @@ static const struct bpf_iter_seq_info unix_seq_info = {
 	.seq_priv_size		= sizeof(struct bpf_unix_iter_state),
 };
 
+static const struct bpf_func_proto *
+bpf_iter_unix_get_func_proto(enum bpf_func_id func_id,
+			     const struct bpf_prog *prog)
+{
+	switch (func_id) {
+	case BPF_FUNC_setsockopt:
+		return &bpf_sk_setsockopt_proto;
+	case BPF_FUNC_getsockopt:
+		return &bpf_sk_getsockopt_proto;
+	default:
+		return NULL;
+	}
+}
+
 static struct bpf_iter_reg unix_reg_info = {
 	.target			= "unix",
 	.ctx_arg_info_size	= 1,
@@ -3640,6 +3654,7 @@ static struct bpf_iter_reg unix_reg_info = {
 		{ offsetof(struct bpf_iter__unix, unix_sk),
 		  PTR_TO_BTF_ID_OR_NULL },
 	},
+	.get_func_proto         = bpf_iter_unix_get_func_proto,
 	.seq_info		= &unix_seq_info,
 };