csp_if_zmqhub: Handle return value of csp_iflist_add for error checking

Update the code to capture the return value of `csp_iflist_add` in the
variable `ret`.
This allows for proper error handling by ensuring that the
result of `csp_iflist_add` is returned by the function.

Previously, the return value was ignored, which could lead to missing critical
error information.

The return value is now used to confirm successful interface addition, and if an
error occurs, it can be properly propagated.

Signed-off-by: Gaetan Perrot <[email protected]>

src/interfaces/csp_if_zmqhub.c

@@ -208,13 +208,13 @@ int csp_zmqhub_init_w_name_endpoints_rxfilter(const char * ifname, uint16_t addr
 	assert(ret == 0);
 
 	/* Register interface */
-	csp_iflist_add(&drv->iface);
+	ret = csp_iflist_add(&drv->iface);
 
 	if (return_interface) {
 		*return_interface = &drv->iface;
 	}
 
-	return CSP_ERR_NONE;
+	return ret;
 }
 
 int csp_zmqhub_init_filter2(const char * ifname, const char * host, uint16_t addr, uint16_t netmask, int promisc, csp_iface_t ** return_interface, char * sec_key, uint16_t subport, uint16_t pubport) {
@@ -310,13 +310,13 @@ int csp_zmqhub_init_filter2(const char * ifname, const char * host, uint16_t add
 	assert(ret == 0);
 
 	/* Register interface */
-	csp_iflist_add(&drv->iface);
+	ret = csp_iflist_add(&drv->iface);
 
 	if (return_interface) {
 		*return_interface = &drv->iface;
 	}
 
-	return CSP_ERR_NONE;
+	return ret;
 }