app: Raw socket restrictions on PDN CID

app/src/sm_at_socket.c

@@ -17,6 +17,7 @@
 #include "sm_at_host.h"
 #include "sm_at_socket.h"
 #include "sm_sockopt.h"
+#include "sm_ppp.h"
 
 LOG_MODULE_REGISTER(sm_sock, CONFIG_SM_LOG_LEVEL);
 
@@ -155,7 +156,7 @@ static int bind_to_pdn(struct sm_socket *sock)
 		ret = nrf_setsockopt(sock->fd, NRF_SOL_SOCKET, NRF_SO_BINDTOPDN, &cid_int,
 				     sizeof(int));
 		if (ret < 0) {
-			LOG_ERR("nrf_setsockopt(%d) error: %d", NRF_SO_BINDTOPDN, -errno);
+			LOG_ERR("nrf_setsockopt(NRF_SO_BINDTOPDN) error: %d", -errno);
 			ret = -errno;
 		}
 	}
@@ -1104,6 +1105,41 @@ static int socket_datamode_callback(uint8_t op, const uint8_t *data, int len, ui
 	return ret;
 }
 
+/* Two RAW sockets cannot share the same CID. PPP is in practice a RAW socket.
+ * This function checks if a new socket can be created on the given CID.
+ * The CID cannot have a RAW sockets already, and if the new socket is RAW,
+ * the CID cannot have any other sockets already.
+ */
+static bool cid_validity_raw_socket_check(uint16_t cid, int type)
+{
+#if defined(CONFIG_SM_PPP)
+	/* PPP is raw socket so new socket cannot be created on the same CID */
+	if (sm_ppp_is_running_on_cid(cid)) {
+		LOG_ERR("Socket creation not allowed on PPP PDN (%d) when PPP is not stopped", cid);
+		return false;
+	}
+#endif
+	for (int i = 0; i < SM_MAX_SOCKET_COUNT; i++) {
+		if (socks[i].cid == cid) {
+			/* If the CID is used for RAW sockets*/
+			if (type == NRF_SOCK_RAW) {
+				LOG_ERR("Raw socket creation not allowed on PDN (%d) "
+					"which already has another socket", cid);
+				return false;
+			}
+
+			/* If the CID is used for a RAW socket */
+			if (socks[i].type == NRF_SOCK_RAW) {
+				LOG_ERR("Socket creation not allowed on PDN (%d) "
+					"which already has RAW socket", cid);
+				return false;
+			}
+		}
+	}
+
+	return true;
+}
+
 SM_AT_CMD_CUSTOM(xsocket, "AT#XSOCKET", handle_at_socket);
 static int handle_at_socket(enum at_parser_cmd_type cmd_type, struct at_parser *parser,
 			    uint32_t param_count)
@@ -1145,6 +1181,10 @@ static int handle_at_socket(enum at_parser_cmd_type cmd_type, struct at_parser *
 					goto error;
 				}
 			}
+			if (!cid_validity_raw_socket_check(sock->cid, sock->type)) {
+				err = -EFAULT;
+				goto error;
+			}
 			err = do_socket_open(sock);
 			if (err) {
 				LOG_ERR("do_socket_open() failed: %d", err);
@@ -1255,6 +1295,10 @@ static int handle_at_secure_socket(enum at_parser_cmd_type cmd_type,
 					goto error;
 				}
 			}
+			if (!cid_validity_raw_socket_check(sock->cid, sock->type)) {
+				err = -EINVAL;
+				goto error;
+			}
 			err = do_secure_socket_open(sock, peer_verify);
 			if (err) {
 				LOG_ERR("do_secure_socket_open() failed: %d", err);

app/src/sm_ppp.c

@@ -381,6 +381,14 @@ bool sm_ppp_is_stopped(void)
 	return (ppp_state == PPP_STATE_STOPPED);
 }
 
+bool sm_ppp_is_running_on_cid(uint16_t cid)
+{
+	if (!sm_ppp_is_stopped() && cid == ppp_pdn_cid) {
+		return true;
+	}
+	return false;
+}
+
 static int ppp_stop(enum ppp_reason reason)
 {
 	if (ppp_state == PPP_STATE_STOPPED) {

app/src/sm_ppp.h

@@ -7,6 +7,7 @@
 #define SM_PPP_
 
 #include <stdbool.h>
+#include <zephyr/kernel.h>
 
 /* Whether to forward CGEV notifications to the Serial Modem UART. */
 extern bool sm_fwd_cgev_notifs;
@@ -16,4 +17,6 @@ int sm_ppp_init(void);
 
 bool sm_ppp_is_stopped(void);
 
+bool sm_ppp_is_running_on_cid(uint16_t cid);
+
 #endif

doc/app/PPP_AT_commands.rst

@@ -34,6 +34,11 @@ The set command allows you to start and stop PPP, and optionally define the PDN
    When a PPP start has been issued, the PPP connection is automatically activated and deactivated when the PDN connection requested for PPP is established and lost, respectively.
    This will continue until a PPP stop is issued by either the user by the ``AT#XPPP=0`` command or by the remote peer disconnecting the PPP using LCP termination.
 
+.. note::
+
+   PPP cannot be started on a PDN connection that is already in use by another socket.
+   The reason is that PPP is a raw socket, which intercepts all downlink data intended for other sockets on the same PDN, which disrupts normal socket operations.
+
 Syntax
 ~~~~~~
 

doc/app/SOCKET_AT_commands.rst

@@ -17,6 +17,13 @@ Socket #XSOCKET
 
 The ``#XSOCKET`` command allows you to open a socket and to check the socket handle.
 
+.. note::
+
+   A socket cannot be created on a PDN connection that is already in use by a raw socket.
+   A raw socket cannot be created on a PDN connection that is already in use by another socket.
+   The reason is that a raw socket cannot keep its data separate from the data of another IP socket when both are operating on the same PDN.
+   When a raw socket is active, it intercepts all downlink data intended for other sockets on the same PDN, which disrupts normal socket operations.
+
 Set command
 -----------
 
@@ -182,6 +189,12 @@ The ``#XSSOCKET`` command allows you to open a secure socket and to check the so
 .. note::
    TLS and DTLS servers are currently not supported.
 
+.. note::
+
+   A secure socket cannot be created on a PDN connection that is already in use by a raw socket.
+   The reason is that a raw socket cannot keep its data separate from the data of another IP socket when both are operating on the same PDN.
+   When a raw socket is active, it intercepts all downlink data intended for other sockets on the same PDN, which disrupts normal socket operations.
+
 Set command
 -----------