net: sockets: tls: Add helper function to verify protocol

This commit adds helper function to verify protocol, which was done in
two different places in the code. The function returns the underlying
protocol information on success.

Signed-off-by: Robert Lubos <robert.lubos@nordicsemi.no>

subsys/net/lib/sockets/sockets_tls.c

@@ -1117,9 +1117,38 @@ static int tls_opt_dtls_role_set(struct net_context *context,
 	return 0;
 }
 
+static int protocol_check(int family, int type, int *proto)
+{
+	if (family != AF_INET && family != AF_INET6) {
+		return -EAFNOSUPPORT;
+	}
+
+	if (*proto >= IPPROTO_TLS_1_0 && *proto <= IPPROTO_TLS_1_2) {
+		if (type != SOCK_STREAM) {
+			return -EPROTOTYPE;
+		}
+
+		*proto = IPPROTO_TCP;
+	} else if (*proto >= IPPROTO_DTLS_1_0 && *proto <= IPPROTO_DTLS_1_2) {
+		if (!IS_ENABLED(CONFIG_NET_SOCKETS_ENABLE_DTLS)) {
+			return -EPROTONOSUPPORT;
+		}
+
+		if (type != SOCK_DGRAM) {
+			return -EPROTOTYPE;
+		}
+
+		*proto = IPPROTO_UDP;
+	} else {
+		return -EPROTONOSUPPORT;
+	}
+
+	return 0;
+}
+
 static int ztls_socket(int family, int type, int proto)
 {
-	enum net_ip_protocol_secure tls_proto = 0;
+	enum net_ip_protocol_secure tls_proto = proto;
 	int fd = z_reserve_fd();
 	int ret;
 	struct net_context *ctx;
@@ -1128,27 +1157,10 @@ static int ztls_socket(int family, int type, int proto)
 		return -1;
 	}
 
-	if (proto >= IPPROTO_TLS_1_0 && proto <= IPPROTO_TLS_1_2) {
-		if (type != SOCK_STREAM) {
-			errno = EPROTOTYPE;
-			return -1;
-		}
-
-		tls_proto = proto;
-		proto = IPPROTO_TCP;
-	} else if (proto >= IPPROTO_DTLS_1_0 && proto <= IPPROTO_DTLS_1_2) {
-#if !defined(CONFIG_NET_SOCKETS_ENABLE_DTLS)
-		errno = EPROTONOSUPPORT;
+	ret = protocol_check(family, type, &proto);
+	if (ret < 0) {
+		errno = -ret;
 		return -1;
-#else
-		if (type != SOCK_DGRAM) {
-			errno = EPROTOTYPE;
-			return -1;
-		}
-
-		tls_proto = proto;
-		proto = IPPROTO_UDP;
-#endif
 	}
 
 	ret = net_context_get(family, type, proto, &ctx);
@@ -1164,19 +1176,16 @@ static int ztls_socket(int family, int type, int proto)
 	/* recv_q and accept_q are in union */
 	k_fifo_init(&ctx->recv_q);
 
-	if (tls_proto != 0) {
-		/* If TLS protocol is used, allocate TLS context */
-		ctx->tls = tls_alloc();
-		if (ctx->tls == NULL) {
-			z_free_fd(fd);
-			(void)net_context_put(ctx);
-			errno = ENOMEM;
-			return -1;
-		}
-
-		ctx->tls->tls_version = tls_proto;
+	ctx->tls = tls_alloc();
+	if (ctx->tls == NULL) {
+		z_free_fd(fd);
+		(void)net_context_put(ctx);
+		errno = ENOMEM;
+		return -1;
 	}
 
+	ctx->tls->tls_version = tls_proto;
+
 	if (proto == IPPROTO_TCP) {
 		net_context_ref(ctx);
 	}
@@ -2077,9 +2086,7 @@ static const struct socket_op_vtable tls_sock_fd_op_vtable = {
 
 static bool tls_is_supported(int family, int type, int proto)
 {
-	if ((family == AF_INET || family == AF_INET6) &&
-	    (((proto >= IPPROTO_TLS_1_0) && (proto <= IPPROTO_TLS_1_2)) ||
-	     (proto >= IPPROTO_DTLS_1_0 && proto <= IPPROTO_DTLS_1_2))) {
+	if (protocol_check(family, type, &proto) == 0) {
 		return true;
 	}