Add getsockopt option to read network property

Add getsockopt options NSAPI_LATENCY and NSAPI_STAGGER to read
network specific timing constraints from socket.
-NS_LATENCY returns estimated latency to given address.
-NSAPI_STAGGER returns estimated initial delay that application
 should wait before transmitting data to network.

Application can use the new options to avoid network congestion by
adjusting transmission delays and retry timeouts.

Add wrappers to make API usage easier:
-get_rtt_estimate_to_address
-get_stagger_estimate_to_address

This is backport of the #12522

Author: Arto Kinnunen

UNITTESTS/features/netsocket/InternetSocket/test_InternetSocket.cpp

@@ -185,6 +185,18 @@ TEST_F(TestInternetSocket, modify_multicast_group)
     EXPECT_EQ(socket->leave_multicast_group(a), NSAPI_ERROR_UNSUPPORTED);
 }
 
+TEST_F(TestInternetSocket, network_property)
+{
+    SocketAddress a("fd00:db8::ff", 1024);
+    uint32_t rtt_estimate;
+    uint16_t stagger_min, stagger_max, stagger_rand;
+    stack.return_value = NSAPI_ERROR_OK;
+    socket->open(&stack);
+    EXPECT_EQ(socket->get_rtt_estimate_to_address(a, &rtt_estimate), NSAPI_ERROR_UNSUPPORTED);
+    EXPECT_EQ(socket->get_rtt_estimate_to_address(a, NULL), NSAPI_ERROR_PARAMETER);
+    EXPECT_EQ(socket->get_stagger_estimate_to_address(a, 1, &stagger_min, &stagger_max, &stagger_rand), NSAPI_ERROR_UNSUPPORTED);
+}
+
 // set_blocking and set_timeout are tested within TCPSocket.
 
 TEST_F(TestInternetSocket, bind_no_socket)

features/nanostack/nanostack-interface/Nanostack.cpp

@@ -840,18 +840,58 @@ nsapi_error_t Nanostack::setsockopt(void *handle, int level, int optname, const
 nsapi_error_t Nanostack::getsockopt(void *handle, int level, int optname, void *optval, unsigned *optlen)
 {
     NanostackSocket *socket = static_cast<NanostackSocket *>(handle);
+
     if (handle == NULL) {
         MBED_ASSERT(false);
         return NSAPI_ERROR_NO_SOCKET;
     }
 
     NanostackLockGuard lock;
+    // pointers to Mbed OS structures
+    nsapi_latency_req_t *ns_latency_r = static_cast<nsapi_latency_req_t *>(optval);
+    nsapi_stagger_req_t *ns_stagger_r = static_cast<nsapi_stagger_req_t *>(optval);
+    // Nanostack internal structures
+    ns_ipv6_latency_t nanostack_latency;
+    ns_ipv6_stagger_t nanostack_stagger;
+    int nanostack_optname = optname;
+
+    void *ns_option_value = optval;
+
+    if (level == NSAPI_SOCKET) {
+        if (optname == NSAPI_LATENCY) {
+            if (*optlen < sizeof(nsapi_latency_req_t)) {
+                return NSAPI_ERROR_PARAMETER;
+            }
+            // Adjust to Nanostack namespace
+            level = SOCKET_IPPROTO_IPV6;
+            nanostack_optname = SOCKET_LATENCY;
+            memcpy(nanostack_latency.dest_addr, ns_latency_r->addr, 16);
+            ns_option_value = &nanostack_latency;
+        } else if (optname == NSAPI_STAGGER) {
+            if (*optlen < sizeof(nsapi_stagger_req_t)) {
+                return NSAPI_ERROR_PARAMETER;
+            }
+            // Adjust to Nanostack namespace
+            level = SOCKET_IPPROTO_IPV6;
+            nanostack_optname = SOCKET_STAGGER;
+            memcpy(nanostack_stagger.dest_addr, ns_stagger_r->addr, 16);
+            nanostack_stagger.data_amount = ns_stagger_r->data_amount;
+            ns_option_value = &nanostack_stagger;
+        }
+    }
 
     uint16_t optlen16 = *optlen;
 
-    int retcode = ::socket_getsockopt(socket->socket_id, level, optname, optval, &optlen16);
+    int retcode = ::socket_getsockopt(socket->socket_id, level, nanostack_optname, ns_option_value, &optlen16);
     if (retcode == 0) {
         *optlen = optlen16;
+        if (optname == NSAPI_LATENCY) {
+            ns_latency_r->latency = nanostack_latency.latency;
+        } else if (optname == NSAPI_STAGGER) {
+            ns_stagger_r->stagger_min = nanostack_stagger.stagger_min;
+            ns_stagger_r->stagger_max = nanostack_stagger.stagger_max;
+            ns_stagger_r->stagger_rand = nanostack_stagger.stagger_rand;
+        }
         return NSAPI_ERROR_OK;
     } else if (retcode == -2) {
         return NSAPI_ERROR_UNSUPPORTED;

features/netsocket/InternetSocket.cpp

@@ -119,6 +119,54 @@ int InternetSocket::leave_multicast_group(const SocketAddress &address)
     return modify_multicast_group(address, NSAPI_DROP_MEMBERSHIP);
 }
 
+int InternetSocket::get_rtt_estimate_to_address(const SocketAddress &address, uint32_t *rtt_estimate)
+{
+    nsapi_error_t ret;
+    nsapi_latency_req_t ns_api_latency_req;
+    unsigned opt_len = sizeof(nsapi_latency_req_t);
+
+    if (!rtt_estimate) {
+        return NSAPI_ERROR_PARAMETER;
+    }
+
+    // Set up address
+    memcpy(ns_api_latency_req.addr, address.get_ip_bytes(), 16);
+
+    ret = this->getsockopt(NSAPI_SOCKET, NSAPI_LATENCY, &ns_api_latency_req, &opt_len);
+    if (ret == NSAPI_ERROR_OK) {
+        // success, latency found. Convert to RTT.
+        *rtt_estimate = ns_api_latency_req.latency * 2;
+    }
+
+    return ret;
+}
+
+int InternetSocket::get_stagger_estimate_to_address(const SocketAddress &address, uint16_t data_amount, uint16_t *stagger_min, uint16_t *stagger_max, uint16_t *stagger_rand)
+{
+    nsapi_error_t ret;
+    nsapi_stagger_req_t nsapi_stagger;
+    unsigned opt_len = sizeof(nsapi_stagger_req_t);
+
+    // Set up address
+    memcpy(nsapi_stagger.addr, address.get_ip_bytes(), 16);
+    nsapi_stagger.data_amount = data_amount;
+
+    ret = this->getsockopt(NSAPI_SOCKET, NSAPI_STAGGER, &nsapi_stagger, &opt_len);
+    if (ret == NSAPI_ERROR_OK) {
+        // success, stagger found
+        if (stagger_min) {
+            *stagger_min = nsapi_stagger.stagger_min;
+        }
+        if (stagger_max) {
+            *stagger_max = nsapi_stagger.stagger_max;
+        }
+        if (stagger_rand) {
+            *stagger_rand = nsapi_stagger.stagger_rand;
+        }
+    }
+
+    return ret;
+}
 
 nsapi_error_t InternetSocket::bind(uint16_t port)
 {

features/netsocket/InternetSocket.h

@@ -86,6 +86,35 @@ class InternetSocket : public Socket {
      */
     int leave_multicast_group(const SocketAddress &address);
 
+    /** Get estimated round trip time to destination address.
+     *
+     * Use estimated round trip time to adjust application retry timers to work in networks
+     * that have low data rate and high latency.
+     *
+     * @param address   Destination address to use in rtt estimate.
+     * @param rtt_estimate   Returned round trip time value in milliseconds.
+     *  @return         NSAPI_ERROR_OK on success.
+     *  @return         NSAPI_ERROR_PARAMETER if the provided pointer is invalid.
+     *  @return         negative error code on other failures (@see InternetSocket::getsockopt).
+     */
+    int get_rtt_estimate_to_address(const SocketAddress &address, uint32_t *rtt_estimate);
+
+    /** Get estimated stagger value.
+     *
+     * Stagger value is a time that application should wait before using heavy network operations after connecting to network.
+     * Purpose of staggering is to avoid network congestion that may happen in low bandwith networks if multiple
+     * applications simultaneously start heavy network usage after joining to the network.
+     *
+     * @param address       Destination added used to estimate stagger value.
+     * @param data_amount   Amount of bytes to transfer in kilobytes.
+     * @param stagger_min   Minimum stagger value in seconds.
+     * @param stagger_max   Maximum stagger value in seconds.
+     * @param stagger_rand  Randomized stagger value between stagger_min and stagger_max in seconds.
+     * @return              NSAPI_ERROR_OK on success.
+     * @return              negative error code on other failures (@see InternetSocket::getsockopt).
+     */
+    int get_stagger_estimate_to_address(const SocketAddress &address, uint16_t data_amount, uint16_t *stagger_min, uint16_t *stagger_max, uint16_t *stagger_rand);
+
     /** Bind the socket to a port on which to receive data.
      *
      *  @param port     Local port to bind.

features/netsocket/nsapi_types.h

@@ -267,7 +267,9 @@ typedef enum nsapi_socket_option {
     NSAPI_RCVBUF,            /*!< Sets recv buffer size */
     NSAPI_ADD_MEMBERSHIP,    /*!< Add membership to multicast address */
     NSAPI_DROP_MEMBERSHIP,   /*!< Drop membership to multicast address */
-    NSAPI_BIND_TO_DEVICE,        /*!< Bind socket network interface name*/
+    NSAPI_BIND_TO_DEVICE,    /*!< Bind socket network interface name*/
+    NSAPI_LATENCY,           /*!< Read estimated latency to destination */
+    NSAPI_STAGGER,           /*!< Read estimated stagger value to destination */
 } nsapi_socket_option_t;
 
 typedef enum nsapi_tlssocket_level {
@@ -338,6 +340,23 @@ typedef struct nsapi_ip_mreq {
     nsapi_addr_t imr_interface; /* local IP address of interface */
 } nsapi_ip_mreq_t;
 
+/** nsapi_latency_req structure
+ */
+typedef struct nsapi_latency_req {
+    uint8_t addr[16];   /* [IN] Destination address to estimate latency */
+    uint32_t latency;   /* [OUT] Latency value */
+} nsapi_latency_req_t;
+
+/** nsapi_stagger_req structure
+ */
+typedef struct nsapi_stagger_req {
+    uint8_t addr[16];       /* [IN] Destination address to estimate stagger */
+    uint16_t data_amount;   /* [IN] Amount of data to be sent in kilobytes */
+    uint16_t stagger_min;   /* [OUT] Minimum stagger value in seconds */
+    uint16_t stagger_max;   /* [OUT] Maximum stagger value in seconds */
+    uint16_t stagger_rand;  /* [OUT] Randomized stagger value in seconds */
+} nsapi_stagger_req_t;
+
 /** nsapi_stack_api structure
  *
  *  Common api structure for network stack operations. A network stack