Diff: uamqp/src/link.c

Revision:

0:f7f1f0d76dd6

diff -r 000000000000 -r f7f1f0d76dd6 uamqp/src/link.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/uamqp/src/link.c	Thu Aug 23 06:52:14 2018 +0000
@@ -0,0 +1,1655 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+#include <stdlib.h>
+#include <string.h>
+#include <stdint.h>
+#include <stdbool.h>
+#include "azure_c_shared_utility/gballoc.h"
+#include "azure_c_shared_utility/optimize_size.h"
+#include "azure_c_shared_utility/xlogging.h"
+#include "azure_c_shared_utility/singlylinkedlist.h"
+#include "azure_c_shared_utility/tickcounter.h"
+#include "azure_uamqp_c/link.h"
+#include "azure_uamqp_c/session.h"
+#include "azure_uamqp_c/amqpvalue.h"
+#include "azure_uamqp_c/amqp_definitions.h"
+#include "azure_uamqp_c/amqp_frame_codec.h"
+#include "azure_uamqp_c/async_operation.h"
+
+#define DEFAULT_LINK_CREDIT 10000
+
+typedef struct DELIVERY_INSTANCE_TAG
+{
+    delivery_number delivery_id;
+    ON_DELIVERY_SETTLED on_delivery_settled;
+    void* callback_context;
+    void* link;
+    tickcounter_ms_t start_tick;
+    tickcounter_ms_t timeout;
+} DELIVERY_INSTANCE;
+
+typedef struct ON_LINK_DETACH_EVENT_SUBSCRIPTION_TAG
+{
+    ON_LINK_DETACH_RECEIVED on_link_detach_received;
+    void* context;
+} ON_LINK_DETACH_EVENT_SUBSCRIPTION;
+
+typedef struct LINK_INSTANCE_TAG
+{
+    SESSION_HANDLE session;
+    LINK_STATE link_state;
+    LINK_STATE previous_link_state;
+    AMQP_VALUE source;
+    AMQP_VALUE target;
+    handle handle;
+    LINK_ENDPOINT_HANDLE link_endpoint;
+    char* name;
+    SINGLYLINKEDLIST_HANDLE pending_deliveries;
+    sequence_no delivery_count;
+    role role;
+    ON_LINK_STATE_CHANGED on_link_state_changed;
+    ON_LINK_FLOW_ON on_link_flow_on;
+    ON_TRANSFER_RECEIVED on_transfer_received;
+    void* callback_context;
+    sender_settle_mode snd_settle_mode;
+    receiver_settle_mode rcv_settle_mode;
+    sequence_no initial_delivery_count;
+    uint64_t max_message_size;
+    uint64_t peer_max_message_size;
+    uint32_t current_link_credit;
+    uint32_t max_link_credit;
+    uint32_t available;
+    fields attach_properties;
+    bool is_underlying_session_begun;
+    bool is_closed;
+    unsigned char* received_payload;
+    uint32_t received_payload_size;
+    delivery_number received_delivery_id;
+    TICK_COUNTER_HANDLE tick_counter;
+    ON_LINK_DETACH_EVENT_SUBSCRIPTION on_link_detach_received_event_subscription;
+} LINK_INSTANCE;
+
+DEFINE_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE);
+
+static void set_link_state(LINK_INSTANCE* link_instance, LINK_STATE link_state)
+{
+    link_instance->previous_link_state = link_instance->link_state;
+    link_instance->link_state = link_state;
+
+    if (link_instance->on_link_state_changed != NULL)
+    {
+        link_instance->on_link_state_changed(link_instance->callback_context, link_state, link_instance->previous_link_state);
+    }
+}
+
+static void remove_all_pending_deliveries(LINK_INSTANCE* link, bool indicate_settled)
+{
+    if (link->pending_deliveries != NULL)
+    {
+        LIST_ITEM_HANDLE item = singlylinkedlist_get_head_item(link->pending_deliveries);
+        while (item != NULL)
+        {
+            LIST_ITEM_HANDLE next_item = singlylinkedlist_get_next_item(item);
+            ASYNC_OPERATION_HANDLE pending_delivery_operation = (ASYNC_OPERATION_HANDLE)singlylinkedlist_item_get_value(item);
+            if (pending_delivery_operation != NULL)
+            {
+                DELIVERY_INSTANCE* delivery_instance = (DELIVERY_INSTANCE*)GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, pending_delivery_operation);
+                if (indicate_settled && (delivery_instance->on_delivery_settled != NULL))
+                {
+                    delivery_instance->on_delivery_settled(delivery_instance->callback_context, delivery_instance->delivery_id, LINK_DELIVERY_SETTLE_REASON_NOT_DELIVERED, NULL);
+                }
+
+                async_operation_destroy(pending_delivery_operation);
+            }
+
+            item = next_item;
+        }
+
+        singlylinkedlist_destroy(link->pending_deliveries);
+        link->pending_deliveries = NULL;
+    }
+}
+
+static int send_flow(LINK_INSTANCE* link)
+{
+    int result;
+    FLOW_HANDLE flow = flow_create(0, 0, 0);
+
+    if (flow == NULL)
+    {
+        LogError("NULL flow performative");
+        result = __FAILURE__;
+    }
+    else
+    {
+        if (flow_set_link_credit(flow, link->current_link_credit) != 0)
+        {
+            LogError("Cannot set link credit on flow performative");
+            result = __FAILURE__;
+        }
+        else if (flow_set_handle(flow, link->handle) != 0)
+        {
+            LogError("Cannot set handle on flow performative");
+            result = __FAILURE__;
+        }
+        else if (flow_set_delivery_count(flow, link->delivery_count) != 0)
+        {
+            LogError("Cannot set delivery count on flow performative");
+            result = __FAILURE__;
+        }
+        else
+        {
+            if (session_send_flow(link->link_endpoint, flow) != 0)
+            {
+                LogError("Sending flow frame failed in session send");
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+
+        flow_destroy(flow);
+    }
+
+    return result;
+}
+
+static int send_disposition(LINK_INSTANCE* link_instance, delivery_number delivery_number, AMQP_VALUE delivery_state)
+{
+    int result;
+
+    DISPOSITION_HANDLE disposition = disposition_create(link_instance->role, delivery_number);
+    if (disposition == NULL)
+    {
+        LogError("NULL disposition performative");
+        result = __FAILURE__;
+    }
+    else
+    {
+        if (disposition_set_last(disposition, delivery_number) != 0)
+        {
+            LogError("Failed setting last on disposition performative");
+            result = __FAILURE__;
+        }
+        else if (disposition_set_settled(disposition, true) != 0)
+        {
+            LogError("Failed setting settled on disposition performative");
+            result = __FAILURE__;
+        }
+        else if ((delivery_state != NULL) && (disposition_set_state(disposition, delivery_state) != 0))
+        {
+            LogError("Failed setting state on disposition performative");
+            result = __FAILURE__;
+        }
+        else
+        {
+            if (session_send_disposition(link_instance->link_endpoint, disposition) != 0)
+            {
+                LogError("Sending disposition failed in session send");
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+
+        disposition_destroy(disposition);
+    }
+
+    return result;
+}
+
+static int send_detach(LINK_INSTANCE* link_instance, bool close, ERROR_HANDLE error_handle)
+{
+    int result;
+    DETACH_HANDLE detach_performative;
+
+    detach_performative = detach_create(0);
+    if (detach_performative == NULL)
+    {
+        LogError("NULL detach performative");
+        result = __FAILURE__;
+    }
+    else
+    {
+        if ((error_handle != NULL) &&
+            (detach_set_error(detach_performative, error_handle) != 0))
+        {
+            LogError("Failed setting error on detach frame");
+            result = __FAILURE__;
+        }
+        else if (close &&
+            (detach_set_closed(detach_performative, true) != 0))
+        {
+            LogError("Failed setting closed field on detach frame");
+            result = __FAILURE__;
+        }
+        else
+        {
+            if (session_send_detach(link_instance->link_endpoint, detach_performative) != 0)
+            {
+                LogError("Sending detach frame failed in session send");
+                result = __FAILURE__;
+            }
+            else
+            {
+                if (close)
+                {
+                    /* Declare link to be closed */
+                    link_instance->is_closed = true;
+                }
+
+                result = 0;
+            }
+        }
+
+        detach_destroy(detach_performative);
+    }
+
+    return result;
+}
+
+static int send_attach(LINK_INSTANCE* link, const char* name, handle handle, role role)
+{
+    int result;
+    ATTACH_HANDLE attach = attach_create(name, handle, role);
+
+    if (attach == NULL)
+    {
+        LogError("NULL attach performative");
+        result = __FAILURE__;
+    }
+    else
+    {
+        result = 0;
+
+        link->delivery_count = link->initial_delivery_count;
+
+        attach_set_snd_settle_mode(attach, link->snd_settle_mode);
+        attach_set_rcv_settle_mode(attach, link->rcv_settle_mode);
+        attach_set_role(attach, role);
+        attach_set_source(attach, link->source);
+        attach_set_target(attach, link->target);
+        if (link->attach_properties != NULL)
+        {
+            (void)attach_set_properties(attach, link->attach_properties);
+        }
+
+        if (role == role_sender)
+        {
+            if (attach_set_initial_delivery_count(attach, link->delivery_count) != 0)
+            {
+                LogError("Cannot set attach initial delivery count");
+                result = __FAILURE__;
+            }
+        }
+
+        if (result == 0)
+        {
+            if (attach_set_max_message_size(attach, link->max_message_size) != 0)
+            {
+                LogError("Cannot set max message size");
+                result = __FAILURE__;
+            }
+            else if (session_send_attach(link->link_endpoint, attach) != 0)
+            {
+                LogError("Sending attach failed in session send");
+                result = __FAILURE__;
+            }
+            else
+            {
+                result = 0;
+            }
+        }
+
+        attach_destroy(attach);
+    }
+
+    return result;
+}
+
+static void link_frame_received(void* context, AMQP_VALUE performative, uint32_t payload_size, const unsigned char* payload_bytes)
+{
+    LINK_INSTANCE* link_instance = (LINK_INSTANCE*)context;
+    AMQP_VALUE descriptor = amqpvalue_get_inplace_descriptor(performative);
+
+    if (is_attach_type_by_descriptor(descriptor))
+    {
+        ATTACH_HANDLE attach_handle;
+
+        if (amqpvalue_get_attach(performative, &attach_handle) != 0)
+        {
+            LogError("Cannot get attach performative");
+        }
+        else
+        {
+            if ((link_instance->role == role_receiver) &&
+                (attach_get_initial_delivery_count(attach_handle, &link_instance->delivery_count) != 0))
+            {
+                LogError("Cannot get initial delivery count");
+                remove_all_pending_deliveries(link_instance, true);
+                set_link_state(link_instance, LINK_STATE_DETACHED);
+            }
+            else
+            {
+                if (attach_get_max_message_size(attach_handle, &link_instance->peer_max_message_size) != 0)
+                {
+                    LogError("Could not retrieve peer_max_message_size from attach frame");
+                }
+
+                if ((link_instance->link_state == LINK_STATE_DETACHED) ||
+                    (link_instance->link_state == LINK_STATE_HALF_ATTACHED_ATTACH_SENT))
+                {
+                    if (link_instance->role == role_receiver)
+                    {
+                        link_instance->current_link_credit = link_instance->max_link_credit;
+                        send_flow(link_instance);
+                    }
+                    else
+                    {
+                        link_instance->current_link_credit = 0;
+                    }
+
+                    if (link_instance->link_state == LINK_STATE_DETACHED)
+                    {
+                        set_link_state(link_instance, LINK_STATE_HALF_ATTACHED_ATTACH_RECEIVED);
+                    }
+                    else
+                    {
+                        set_link_state(link_instance, LINK_STATE_ATTACHED);
+                    }
+                }
+            }
+
+            attach_destroy(attach_handle);
+        }
+    }
+    else if (is_flow_type_by_descriptor(descriptor))
+    {
+        FLOW_HANDLE flow_handle;
+        if (amqpvalue_get_flow(performative, &flow_handle) != 0)
+        {
+            LogError("Cannot get flow performative");
+        }
+        else
+        {
+            if (link_instance->role == role_sender)
+            {
+                delivery_number rcv_delivery_count;
+                uint32_t rcv_link_credit;
+
+                if (flow_get_link_credit(flow_handle, &rcv_link_credit) != 0)
+                {
+                    LogError("Cannot get link credit");
+                    remove_all_pending_deliveries(link_instance, true);
+                    set_link_state(link_instance, LINK_STATE_DETACHED);
+                }
+                else if (flow_get_delivery_count(flow_handle, &rcv_delivery_count) != 0)
+                {
+                    LogError("Cannot get delivery count");
+                    remove_all_pending_deliveries(link_instance, true);
+                    set_link_state(link_instance, LINK_STATE_DETACHED);
+                }
+                else
+                {
+                    link_instance->current_link_credit = rcv_delivery_count + rcv_link_credit - link_instance->delivery_count;
+                    if (link_instance->current_link_credit > 0)
+                    {
+                        link_instance->on_link_flow_on(link_instance->callback_context);
+                    }
+                }
+            }
+        }
+
+        flow_destroy(flow_handle);
+    }
+    else if (is_transfer_type_by_descriptor(descriptor))
+    {
+        if (link_instance->on_transfer_received != NULL)
+        {
+            TRANSFER_HANDLE transfer_handle;
+            if (amqpvalue_get_transfer(performative, &transfer_handle) != 0)
+            {
+                LogError("Cannot get transfer performative");
+            }
+            else
+            {
+                AMQP_VALUE delivery_state;
+                bool more;
+                bool is_error;
+
+                link_instance->current_link_credit--;
+                link_instance->delivery_count++;
+                if (link_instance->current_link_credit == 0)
+                {
+                    link_instance->current_link_credit = link_instance->max_link_credit;
+                    send_flow(link_instance);
+                }
+
+                more = false;
+                /* Attempt to get more flag, default to false */
+                (void)transfer_get_more(transfer_handle, &more);
+                is_error = false;
+
+                if (transfer_get_delivery_id(transfer_handle, &link_instance->received_delivery_id) != 0)
+                {
+                    /* is this not a continuation transfer? */
+                    if (link_instance->received_payload_size == 0)
+                    {
+                        LogError("Could not get the delivery Id from the transfer performative");
+                        is_error = true;
+                    }
+                }
+                    
+                if (!is_error)
+                {
+                    /* If this is a continuation transfer or if this is the first chunk of a multi frame transfer */
+                    if ((link_instance->received_payload_size > 0) || more)
+                    {
+                        unsigned char* new_received_payload = (unsigned char*)realloc(link_instance->received_payload, link_instance->received_payload_size + payload_size);
+                        if (new_received_payload == NULL)
+                        {
+                            LogError("Could not allocate memory for the received payload");
+                        }
+                        else
+                        {
+                            link_instance->received_payload = new_received_payload;
+                            (void)memcpy(link_instance->received_payload + link_instance->received_payload_size, payload_bytes, payload_size);
+                            link_instance->received_payload_size += payload_size;
+                        }
+                    }
+
+                    if (!more)
+                    {
+                        const unsigned char* indicate_payload_bytes;
+                        uint32_t indicate_payload_size;
+
+                        /* if no previously stored chunks then simply report the current payload */
+                        if (link_instance->received_payload_size > 0)
+                        {
+                            indicate_payload_size = link_instance->received_payload_size;
+                            indicate_payload_bytes = link_instance->received_payload;
+                        }
+                        else
+                        {
+                            indicate_payload_size = payload_size;
+                            indicate_payload_bytes = payload_bytes;
+                        }
+
+                        delivery_state = link_instance->on_transfer_received(link_instance->callback_context, transfer_handle, indicate_payload_size, indicate_payload_bytes);
+
+                        if (link_instance->received_payload_size > 0)
+                        {
+                            free(link_instance->received_payload);
+                            link_instance->received_payload = NULL;
+                            link_instance->received_payload_size = 0;
+                        }
+
+                        if (delivery_state != NULL)
+                        {
+                            if (send_disposition(link_instance, link_instance->received_delivery_id, delivery_state) != 0)
+                            {
+                                LogError("Cannot send disposition frame");
+                            }
+
+                            amqpvalue_destroy(delivery_state);
+                        }
+                    }
+                }
+
+                transfer_destroy(transfer_handle);
+            }
+        }
+    }
+    else if (is_disposition_type_by_descriptor(descriptor))
+    {
+        DISPOSITION_HANDLE disposition;
+        if (amqpvalue_get_disposition(performative, &disposition) != 0)
+        {
+            LogError("Cannot get disposition performative");
+        }
+        else
+        {
+            delivery_number first;
+            delivery_number last;
+
+            if (disposition_get_first(disposition, &first) != 0)
+            {
+                LogError("Cannot get first field");
+            }
+            else
+            {
+                bool settled;
+
+                if (disposition_get_last(disposition, &last) != 0)
+                {
+                    last = first;
+                }
+
+                if (disposition_get_settled(disposition, &settled) != 0)
+                {
+                    settled = false;
+                }
+
+                if (settled)
+                {
+                    LIST_ITEM_HANDLE pending_delivery = singlylinkedlist_get_head_item(link_instance->pending_deliveries);
+                    while (pending_delivery != NULL)
+                    {
+                        LIST_ITEM_HANDLE next_pending_delivery = singlylinkedlist_get_next_item(pending_delivery);
+                        ASYNC_OPERATION_HANDLE pending_delivery_operation = (ASYNC_OPERATION_HANDLE)singlylinkedlist_item_get_value(pending_delivery);
+                        if (pending_delivery_operation == NULL)
+                        {
+                            LogError("Cannot obtain pending delivery");
+                            break;
+                        }
+                        else
+                        {
+                            DELIVERY_INSTANCE* delivery_instance = (DELIVERY_INSTANCE*)GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, pending_delivery_operation);
+
+                            if ((delivery_instance->delivery_id >= first) && (delivery_instance->delivery_id <= last))
+                            {
+                                AMQP_VALUE delivery_state;
+                                if (disposition_get_state(disposition, &delivery_state) == 0)
+                                {
+                                    delivery_instance->on_delivery_settled(delivery_instance->callback_context, delivery_instance->delivery_id, LINK_DELIVERY_SETTLE_REASON_DISPOSITION_RECEIVED, delivery_state);
+                                    async_operation_destroy(pending_delivery_operation);
+                                    if (singlylinkedlist_remove(link_instance->pending_deliveries, pending_delivery) != 0)
+                                    {
+                                        LogError("Cannot remove pending delivery");
+                                        break;
+                                    }
+
+                                    pending_delivery = next_pending_delivery;
+                                }
+                            }
+                            else
+                            {
+                                pending_delivery = next_pending_delivery;
+                            }
+                        }
+                    }
+                }
+            }
+
+            disposition_destroy(disposition);
+        }
+    }
+    else if (is_detach_type_by_descriptor(descriptor))
+    {
+        DETACH_HANDLE detach;
+
+        /* Set link state appropriately based on whether we received detach condition */
+        if (amqpvalue_get_detach(performative, &detach) != 0)
+        {
+            LogError("Cannot get detach performative");
+        }
+        else
+        {
+            bool closed = false;
+            ERROR_HANDLE error;
+
+            (void)detach_get_closed(detach, &closed);
+
+            /* Received a detach while attached */
+            if (link_instance->link_state == LINK_STATE_ATTACHED)
+            {
+                /* Respond with ack */
+                if (send_detach(link_instance, closed, NULL) != 0)
+                {
+                    LogError("Failed sending detach frame");
+                }
+            }
+            /* Received a closing detach after we sent a non-closing detach. */
+            else if (closed &&
+                ((link_instance->link_state == LINK_STATE_HALF_ATTACHED_ATTACH_SENT) || (link_instance->link_state == LINK_STATE_HALF_ATTACHED_ATTACH_RECEIVED)) &&
+                !link_instance->is_closed)
+            {
+
+                /* In this case, we MUST signal that we closed by reattaching and then sending a closing detach.*/
+                if (send_attach(link_instance, link_instance->name, 0, link_instance->role) != 0)
+                {
+                    LogError("Failed sending attach frame");
+                }
+
+                if (send_detach(link_instance, true, NULL) != 0)
+                {
+                    LogError("Failed sending detach frame");
+                }
+            }
+
+            if (detach_get_error(detach, &error) != 0)
+            {
+                error = NULL;
+            }
+            remove_all_pending_deliveries(link_instance, true);
+            // signal link detach received in order to handle cases like redirect
+            if (link_instance->on_link_detach_received_event_subscription.on_link_detach_received != NULL)
+            {
+                link_instance->on_link_detach_received_event_subscription.on_link_detach_received(link_instance->on_link_detach_received_event_subscription.context, error);
+            }
+
+            if (error != NULL)
+            {
+                set_link_state(link_instance, LINK_STATE_ERROR);
+                error_destroy(error);
+            }
+            else 
+            {
+                set_link_state(link_instance, LINK_STATE_DETACHED);
+            }
+
+            detach_destroy(detach);
+        }
+    }
+}
+
+static void on_session_state_changed(void* context, SESSION_STATE new_session_state, SESSION_STATE previous_session_state)
+{
+    LINK_INSTANCE* link_instance = (LINK_INSTANCE*)context;
+    (void)previous_session_state;
+
+    if (new_session_state == SESSION_STATE_MAPPED)
+    {
+        if ((link_instance->link_state == LINK_STATE_DETACHED) && (!link_instance->is_closed))
+        {
+            if (send_attach(link_instance, link_instance->name, 0, link_instance->role) == 0)
+            {
+                set_link_state(link_instance, LINK_STATE_HALF_ATTACHED_ATTACH_SENT);
+            }
+        }
+    }
+    else if (new_session_state == SESSION_STATE_DISCARDING)
+    {
+        remove_all_pending_deliveries(link_instance, true);
+        set_link_state(link_instance, LINK_STATE_DETACHED);
+    }
+    else if (new_session_state == SESSION_STATE_ERROR)
+    {
+        remove_all_pending_deliveries(link_instance, true);
+        set_link_state(link_instance, LINK_STATE_ERROR);
+    }
+}
+
+static void on_session_flow_on(void* context)
+{
+    LINK_INSTANCE* link_instance = (LINK_INSTANCE*)context;
+    if (link_instance->role == role_sender)
+    {
+        link_instance->on_link_flow_on(link_instance->callback_context);
+    }
+}
+
+static void on_send_complete(void* context, IO_SEND_RESULT send_result)
+{
+    LIST_ITEM_HANDLE delivery_instance_list_item = (LIST_ITEM_HANDLE)context;
+    ASYNC_OPERATION_HANDLE pending_delivery_operation = (ASYNC_OPERATION_HANDLE)singlylinkedlist_item_get_value(delivery_instance_list_item);
+    DELIVERY_INSTANCE* delivery_instance = (DELIVERY_INSTANCE*)GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, pending_delivery_operation);
+    LINK_HANDLE link = (LINK_HANDLE)delivery_instance->link;
+    (void)send_result;
+    if (link->snd_settle_mode == sender_settle_mode_settled)
+    {
+        delivery_instance->on_delivery_settled(delivery_instance->callback_context, delivery_instance->delivery_id, LINK_DELIVERY_SETTLE_REASON_SETTLED, NULL);
+        async_operation_destroy(pending_delivery_operation);
+        (void)singlylinkedlist_remove(link->pending_deliveries, delivery_instance_list_item);
+    }
+}
+
+LINK_HANDLE link_create(SESSION_HANDLE session, const char* name, role role, AMQP_VALUE source, AMQP_VALUE target)
+{
+    LINK_INSTANCE* result = (LINK_INSTANCE*)malloc(sizeof(LINK_INSTANCE));
+    if (result == NULL)
+    {
+        LogError("Cannot create link");
+    }
+    else
+    {
+        result->link_state = LINK_STATE_DETACHED;
+        result->previous_link_state = LINK_STATE_DETACHED;
+        result->role = role;
+        result->source = amqpvalue_clone(source);
+        result->target = amqpvalue_clone(target);
+        result->session = session;
+        result->handle = 0;
+        result->snd_settle_mode = sender_settle_mode_unsettled;
+        result->rcv_settle_mode = receiver_settle_mode_first;
+        result->delivery_count = 0;
+        result->initial_delivery_count = 0;
+        result->max_message_size = 0;
+        result->max_link_credit = DEFAULT_LINK_CREDIT;
+        result->peer_max_message_size = 0;
+        result->is_underlying_session_begun = false;
+        result->is_closed = false;
+        result->attach_properties = NULL;
+        result->received_payload = NULL;
+        result->received_payload_size = 0;
+        result->received_delivery_id = 0;
+        result->on_link_detach_received_event_subscription.on_link_detach_received = NULL;
+        result->on_link_detach_received_event_subscription.context = NULL;
+
+        result->tick_counter = tickcounter_create();
+        if (result->tick_counter == NULL)
+        {
+            LogError("Cannot create tick counter for link");
+            free(result);
+            result = NULL;
+        }
+        else
+        {
+            result->pending_deliveries = singlylinkedlist_create();
+            if (result->pending_deliveries == NULL)
+            {
+                LogError("Cannot create pending deliveries list");
+                tickcounter_destroy(result->tick_counter);
+                free(result);
+                result = NULL;
+            }
+            else
+            {
+                size_t name_length = strlen(name);
+                result->name = (char*)malloc(name_length + 1);
+                if (result->name == NULL)
+                {
+                    LogError("Cannot allocate memory for link name");
+                    tickcounter_destroy(result->tick_counter);
+                    singlylinkedlist_destroy(result->pending_deliveries);
+                    free(result);
+                    result = NULL;
+                }
+                else
+                {
+                    result->on_link_state_changed = NULL;
+                    result->callback_context = NULL;
+                    set_link_state(result, LINK_STATE_DETACHED);
+
+                    (void)memcpy(result->name, name, name_length + 1);
+                    result->link_endpoint = session_create_link_endpoint(session, name);
+                    if (result->link_endpoint == NULL)
+                    {
+                        LogError("Cannot create link endpoint");
+                        tickcounter_destroy(result->tick_counter);
+                        singlylinkedlist_destroy(result->pending_deliveries);
+                        free(result->name);
+                        free(result);
+                        result = NULL;
+                    }
+                }
+            }
+        }
+    }
+
+    return result;
+}
+
+LINK_HANDLE link_create_from_endpoint(SESSION_HANDLE session, LINK_ENDPOINT_HANDLE link_endpoint, const char* name, role role, AMQP_VALUE source, AMQP_VALUE target)
+{
+    LINK_INSTANCE* result = (LINK_INSTANCE*)malloc(sizeof(LINK_INSTANCE));
+    if (result == NULL)
+    {
+        LogError("Cannot create link");
+    }
+    else
+    {
+        result->link_state = LINK_STATE_DETACHED;
+        result->previous_link_state = LINK_STATE_DETACHED;
+        result->session = session;
+        result->handle = 0;
+        result->snd_settle_mode = sender_settle_mode_unsettled;
+        result->rcv_settle_mode = receiver_settle_mode_first;
+        result->delivery_count = 0;
+        result->initial_delivery_count = 0;
+        result->max_message_size = 0;
+        result->max_link_credit = DEFAULT_LINK_CREDIT;
+        result->peer_max_message_size = 0;
+        result->is_underlying_session_begun = false;
+        result->is_closed = false;
+        result->attach_properties = NULL;
+        result->received_payload = NULL;
+        result->received_payload_size = 0;
+        result->received_delivery_id = 0;
+        result->source = amqpvalue_clone(target);
+        result->target = amqpvalue_clone(source);
+        result->on_link_detach_received_event_subscription.on_link_detach_received = NULL;
+        result->on_link_detach_received_event_subscription.context = NULL;
+
+        if (role == role_sender)
+        {
+            result->role = role_receiver;
+        }
+        else
+        {
+            result->role = role_sender;
+        }
+
+        result->tick_counter = tickcounter_create();
+        if (result->tick_counter == NULL)
+        {
+            LogError("Cannot create tick counter for link");
+            free(result);
+            result = NULL;
+        }
+        else
+        {
+            result->pending_deliveries = singlylinkedlist_create();
+            if (result->pending_deliveries == NULL)
+            {
+                LogError("Cannot create pending deliveries list");
+                tickcounter_destroy(result->tick_counter);
+                free(result);
+                result = NULL;
+            }
+            else
+            {
+                size_t name_length = strlen(name);
+                result->name = (char*)malloc(name_length + 1);
+                if (result->name == NULL)
+                {
+                    LogError("Cannot allocate memory for link name");
+                    tickcounter_destroy(result->tick_counter);
+                    singlylinkedlist_destroy(result->pending_deliveries);
+                    free(result);
+                    result = NULL;
+                }
+                else
+                {
+                    (void)memcpy(result->name, name, name_length + 1);
+                    result->on_link_state_changed = NULL;
+                    result->callback_context = NULL;
+                    result->link_endpoint = link_endpoint;
+                }
+            }
+        }
+    }
+
+    return result;
+}
+
+void link_destroy(LINK_HANDLE link)
+{
+    if (link == NULL)
+    {
+        LogError("NULL link");
+    }
+    else
+    {
+        remove_all_pending_deliveries((LINK_INSTANCE*)link, false);
+        tickcounter_destroy(link->tick_counter);
+
+        link->on_link_state_changed = NULL;
+        (void)link_detach(link, true, NULL, NULL, NULL);
+        session_destroy_link_endpoint(link->link_endpoint);
+        amqpvalue_destroy(link->source);
+        amqpvalue_destroy(link->target);
+
+        if (link->name != NULL)
+        {
+            free(link->name);
+        }
+
+        if (link->attach_properties != NULL)
+        {
+            amqpvalue_destroy(link->attach_properties);
+        }
+
+        if (link->received_payload != NULL)
+        {
+            free(link->received_payload);
+        }
+
+        free(link);
+    }
+}
+
+int link_set_snd_settle_mode(LINK_HANDLE link, sender_settle_mode snd_settle_mode)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->snd_settle_mode = snd_settle_mode;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_snd_settle_mode(LINK_HANDLE link, sender_settle_mode* snd_settle_mode)
+{
+    int result;
+
+    if ((link == NULL) ||
+        (snd_settle_mode == NULL))
+    {
+        LogError("Bad arguments: link = %p, snd_settle_mode = %p",
+            link, snd_settle_mode);
+        result = __FAILURE__;
+    }
+    else
+    {
+        *snd_settle_mode = link->snd_settle_mode;
+
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_set_rcv_settle_mode(LINK_HANDLE link, receiver_settle_mode rcv_settle_mode)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->rcv_settle_mode = rcv_settle_mode;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_rcv_settle_mode(LINK_HANDLE link, receiver_settle_mode* rcv_settle_mode)
+{
+    int result;
+
+    if ((link == NULL) ||
+        (rcv_settle_mode == NULL))
+    {
+        LogError("Bad arguments: link = %p, rcv_settle_mode = %p",
+            link, rcv_settle_mode);
+        result = __FAILURE__;
+    }
+    else
+    {
+        *rcv_settle_mode = link->rcv_settle_mode;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_set_initial_delivery_count(LINK_HANDLE link, sequence_no initial_delivery_count)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->initial_delivery_count = initial_delivery_count;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_initial_delivery_count(LINK_HANDLE link, sequence_no* initial_delivery_count)
+{
+    int result;
+
+    if ((link == NULL) ||
+        (initial_delivery_count == NULL))
+    {
+        LogError("Bad arguments: link = %p, initial_delivery_count = %p",
+            link, initial_delivery_count);
+        result = __FAILURE__;
+    }
+    else
+    {
+        *initial_delivery_count = link->initial_delivery_count;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_set_max_message_size(LINK_HANDLE link, uint64_t max_message_size)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->max_message_size = max_message_size;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_max_message_size(LINK_HANDLE link, uint64_t* max_message_size)
+{
+    int result;
+
+    if ((link == NULL) ||
+        (max_message_size == NULL))
+    {
+        LogError("Bad arguments: link = %p, max_message_size = %p",
+            link, max_message_size);
+        result = __FAILURE__;
+    }
+    else
+    {
+        *max_message_size = link->max_message_size;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_peer_max_message_size(LINK_HANDLE link, uint64_t* peer_max_message_size)
+{
+    int result;
+
+    if ((link == NULL) ||
+        (peer_max_message_size == NULL))
+    {
+        LogError("Bad arguments: link = %p, peer_max_message_size = %p",
+            link, peer_max_message_size);
+        result = __FAILURE__;
+    }
+    else if ((link->link_state != LINK_STATE_ATTACHED) &&
+        (link->link_state != LINK_STATE_HALF_ATTACHED_ATTACH_RECEIVED))
+    {
+        LogError("Attempting to read peer max message size before it was received");
+        result = __FAILURE__;
+    }
+    else
+    {
+        *peer_max_message_size = link->peer_max_message_size;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_set_attach_properties(LINK_HANDLE link, fields attach_properties)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->attach_properties = amqpvalue_clone(attach_properties);
+        if (link->attach_properties == NULL)
+        {
+            LogError("Failed cloning attach properties");
+            result = __FAILURE__;
+        }
+        else
+        {
+            result = 0;
+        }
+    }
+
+    return result;
+}
+
+int link_set_max_link_credit(LINK_HANDLE link, uint32_t max_link_credit)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        result = __FAILURE__;
+    }
+    else
+    {
+        link->max_link_credit = max_link_credit;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_attach(LINK_HANDLE link, ON_TRANSFER_RECEIVED on_transfer_received, ON_LINK_STATE_CHANGED on_link_state_changed, ON_LINK_FLOW_ON on_link_flow_on, void* callback_context)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else if (link->is_closed)
+    {
+        LogError("Already attached");
+        result = __FAILURE__;
+    }
+    else
+    {
+        if (!link->is_underlying_session_begun)
+        {
+            link->on_link_state_changed = on_link_state_changed;
+            link->on_transfer_received = on_transfer_received;
+            link->on_link_flow_on = on_link_flow_on;
+            link->callback_context = callback_context;
+
+            if (session_begin(link->session) != 0)
+            {
+                LogError("Begin session failed");
+                result = __FAILURE__;
+            }
+            else
+            {
+                link->is_underlying_session_begun = true;
+
+                if (session_start_link_endpoint(link->link_endpoint, link_frame_received, on_session_state_changed, on_session_flow_on, link) != 0)
+                {
+                    LogError("Binding link endpoint to session failed");
+                    result = __FAILURE__;
+                }
+                else
+                {
+                    link->received_payload_size = 0;
+
+                    result = 0;
+                }
+            }
+        }
+        else
+        {
+            result = 0;
+        }
+    }
+
+    return result;
+}
+
+int link_detach(LINK_HANDLE link, bool close, const char* error_condition, const char* error_description, AMQP_VALUE info)
+{
+    int result;
+
+    (void)error_condition;
+    (void)error_description;
+    (void)info;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else if (link->is_closed)
+    {
+        result = 0;
+    }
+    else
+    {
+        ERROR_HANDLE error;
+
+        if (error_condition != NULL)
+        {
+            error = error_create(error_condition);
+            if (error == NULL)
+            {
+                LogInfo("Cannot create error for detach, detaching without error anyhow");
+            }
+            else
+            {
+                if (error_description != NULL)
+                {
+                    if (error_set_description(error, error_description) != 0)
+                    {
+                        LogInfo("Cannot set error description on detach error, detaching anyhow");
+                    }
+                }
+
+                if (info != NULL)
+                {
+                    if (error_set_info(error, info) != 0)
+                    {
+                        LogInfo("Cannot set info map on detach error, detaching anyhow");
+                    }
+                }
+            }
+        }
+        else
+        {
+            error = NULL;
+        }
+
+        switch (link->link_state)
+        {
+        case LINK_STATE_HALF_ATTACHED_ATTACH_SENT:
+        case LINK_STATE_HALF_ATTACHED_ATTACH_RECEIVED:
+            /* Sending detach when remote is not yet attached */
+            if (send_detach(link, close, error) != 0)
+            {
+                LogError("Sending detach frame failed");
+                result = __FAILURE__;
+            }
+            else
+            {
+                set_link_state(link, LINK_STATE_DETACHED);
+                result = 0;
+            }
+            break;
+
+        case LINK_STATE_ATTACHED:
+            /* Send detach and wait for remote to respond */
+            if (send_detach(link, close, error) != 0)
+            {
+                LogError("Sending detach frame failed");
+                result = __FAILURE__;
+            }
+            else
+            {
+                set_link_state(link, LINK_STATE_HALF_ATTACHED_ATTACH_SENT);
+                result = 0;
+            }
+            break;
+
+        case LINK_STATE_DETACHED:
+            /* Already detached */
+            result = 0;
+            break;
+
+        default:
+        case LINK_STATE_ERROR:
+            /* Already detached and in error state */
+            result = __FAILURE__;
+            break;
+        }
+
+        if (error != NULL)
+        {
+            error_destroy(error);
+        }
+    }
+
+    return result;
+}
+
+static bool remove_pending_delivery_condition_function(const void* item, const void* match_context, bool* continue_processing)
+{
+    bool result;
+
+    if (item == match_context)
+    {
+        result = true;
+        *continue_processing = false;
+    }
+    else
+    {
+        result = false;
+        *continue_processing = true;
+    }
+
+    return result;
+}
+
+static void link_transfer_cancel_handler(ASYNC_OPERATION_HANDLE link_transfer_operation)
+{
+    DELIVERY_INSTANCE* pending_delivery = GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, link_transfer_operation);
+    if (pending_delivery->on_delivery_settled != NULL)
+    {
+        pending_delivery->on_delivery_settled(pending_delivery->callback_context, pending_delivery->delivery_id, LINK_DELIVERY_SETTLE_REASON_CANCELLED, NULL);
+    }
+    
+    (void)singlylinkedlist_remove_if(((LINK_HANDLE)pending_delivery->link)->pending_deliveries, remove_pending_delivery_condition_function, pending_delivery);
+
+    async_operation_destroy(link_transfer_operation);
+}
+
+ASYNC_OPERATION_HANDLE link_transfer_async(LINK_HANDLE link, message_format message_format, PAYLOAD* payloads, size_t payload_count, ON_DELIVERY_SETTLED on_delivery_settled, void* callback_context, LINK_TRANSFER_RESULT* link_transfer_error, tickcounter_ms_t timeout)
+{
+    ASYNC_OPERATION_HANDLE result;
+
+    if ((link == NULL) ||
+        (link_transfer_error == NULL))
+    {
+        if (link_transfer_error != NULL)
+        {
+            *link_transfer_error = LINK_TRANSFER_ERROR;
+        }
+
+        LogError("Invalid arguments: link = %p, link_transfer_error = %p",
+            link, link_transfer_error);
+        result = NULL;
+    }
+    else
+    {
+        if (link->role != role_sender)
+        {
+            LogError("Link is not a sender link");
+            *link_transfer_error = LINK_TRANSFER_ERROR;
+            result = NULL;
+        }
+        else if (link->link_state != LINK_STATE_ATTACHED)
+        {
+            LogError("Link is not attached");
+            *link_transfer_error = LINK_TRANSFER_ERROR;
+            result = NULL;
+        }
+        else if (link->current_link_credit == 0)
+        {
+            *link_transfer_error = LINK_TRANSFER_BUSY;
+            result = NULL;
+        }
+        else
+        {
+            result = CREATE_ASYNC_OPERATION(DELIVERY_INSTANCE, link_transfer_cancel_handler);
+            if (result == NULL)
+            {
+                LogError("Error creating async operation");
+                *link_transfer_error = LINK_TRANSFER_ERROR;
+            }
+            else
+            {
+                TRANSFER_HANDLE transfer = transfer_create(0);
+                if (transfer == NULL)
+                {
+                    LogError("Error creating transfer");
+                    *link_transfer_error = LINK_TRANSFER_ERROR;
+                    async_operation_destroy(result);
+                    result = NULL;
+                }
+                else
+                {
+                    sequence_no delivery_count = link->delivery_count + 1;
+                    unsigned char delivery_tag_bytes[sizeof(delivery_count)];
+                    delivery_tag delivery_tag;
+                    bool settled;
+
+                    (void)memcpy(delivery_tag_bytes, &delivery_count, sizeof(delivery_count));
+
+                    delivery_tag.bytes = &delivery_tag_bytes;
+                    delivery_tag.length = sizeof(delivery_tag_bytes);
+
+                    if (link->snd_settle_mode == sender_settle_mode_unsettled)
+                    {
+                        settled = false;
+                    }
+                    else
+                    {
+                        settled = true;
+                    }
+
+                    if (transfer_set_delivery_tag(transfer, delivery_tag) != 0)
+                    {
+                        LogError("Failed setting delivery tag");
+                        *link_transfer_error = LINK_TRANSFER_ERROR;
+                        async_operation_destroy(result);
+                        result = NULL;
+                    }
+                    else if (transfer_set_message_format(transfer, message_format) != 0)
+                    {
+                        LogError("Failed setting message format");
+                        *link_transfer_error = LINK_TRANSFER_ERROR;
+                        async_operation_destroy(result);
+                        result = NULL;
+                    }
+                    else if (transfer_set_settled(transfer, settled) != 0)
+                    {
+                        LogError("Failed setting settled flag");
+                        *link_transfer_error = LINK_TRANSFER_ERROR;
+                        async_operation_destroy(result);
+                        result = NULL;
+                    }
+                    else
+                    {
+                        AMQP_VALUE transfer_value = amqpvalue_create_transfer(transfer);
+                        if (transfer_value == NULL)
+                        {
+                            LogError("Failed creating transfer performative AMQP value");
+                            *link_transfer_error = LINK_TRANSFER_ERROR;
+                            async_operation_destroy(result);
+                            result = NULL;
+                        }
+                        else
+                        {
+                            DELIVERY_INSTANCE* pending_delivery = GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, result);
+                            if (pending_delivery == NULL)
+                            {
+                                LogError("Failed getting pending delivery");
+                                *link_transfer_error = LINK_TRANSFER_ERROR;
+                                async_operation_destroy(result);
+                                result = NULL;
+                            }
+                            else
+                            {
+                                if (tickcounter_get_current_ms(link->tick_counter, &pending_delivery->start_tick) != 0)
+                                {
+                                    LogError("Failed getting current tick");
+                                    *link_transfer_error = LINK_TRANSFER_ERROR;
+                                    async_operation_destroy(result);
+                                    result = NULL;
+                                }
+                                else
+                                {
+                                    LIST_ITEM_HANDLE delivery_instance_list_item;
+                                    pending_delivery->timeout = timeout;
+                                    pending_delivery->on_delivery_settled = on_delivery_settled;
+                                    pending_delivery->callback_context = callback_context;
+                                    pending_delivery->link = link;
+                                    delivery_instance_list_item = singlylinkedlist_add(link->pending_deliveries, result);
+
+                                    if (delivery_instance_list_item == NULL)
+                                    {
+                                        LogError("Failed adding delivery to list");
+                                        *link_transfer_error = LINK_TRANSFER_ERROR;
+                                        async_operation_destroy(result);
+                                        result = NULL;
+                                    }
+                                    else
+                                    {
+                                        /* here we should feed data to the transfer frame */
+                                        switch (session_send_transfer(link->link_endpoint, transfer, payloads, payload_count, &pending_delivery->delivery_id, (settled) ? on_send_complete : NULL, delivery_instance_list_item))
+                                        {
+                                        default:
+                                        case SESSION_SEND_TRANSFER_ERROR:
+                                            LogError("Failed session send transfer");
+                                            if (singlylinkedlist_remove(link->pending_deliveries, delivery_instance_list_item) != 0)
+                                            {
+                                                LogError("Error removing pending delivery from the list");
+                                            }
+
+                                            *link_transfer_error = LINK_TRANSFER_ERROR;
+                                            async_operation_destroy(result);
+                                            result = NULL;
+                                            break;
+
+                                        case SESSION_SEND_TRANSFER_BUSY:
+                                            /* Ensure we remove from list again since sender will attempt to transfer again on flow on */
+                                            LogError("Failed session send transfer");
+                                            if (singlylinkedlist_remove(link->pending_deliveries, delivery_instance_list_item) != 0)
+                                            {
+                                                LogError("Error removing pending delivery from the list");
+                                            }
+
+                                            *link_transfer_error = LINK_TRANSFER_BUSY;
+                                            async_operation_destroy(result);
+                                            result = NULL;
+                                            break;
+
+                                        case SESSION_SEND_TRANSFER_OK:
+                                            link->delivery_count = delivery_count;
+                                            link->current_link_credit--;
+                                            break;
+                                        }
+                                    }
+                                }
+                            }
+
+                            amqpvalue_destroy(transfer_value);
+                        }
+                    }
+
+                    transfer_destroy(transfer);
+                }
+            }
+        }
+    }
+
+    return result;
+}
+
+int link_get_name(LINK_HANDLE link, const char** link_name)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        *link_name = link->name;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_get_received_message_id(LINK_HANDLE link, delivery_number* message_id)
+{
+    int result;
+
+    if (link == NULL)
+    {
+        LogError("NULL link");
+        result = __FAILURE__;
+    }
+    else
+    {
+        *message_id = link->received_delivery_id;
+        result = 0;
+    }
+
+    return result;
+}
+
+int link_send_disposition(LINK_HANDLE link, delivery_number message_id, AMQP_VALUE delivery_state)
+{
+    int result;
+
+    if (delivery_state == NULL)
+    {
+        result = 0;
+    }
+    else
+    {
+        result = send_disposition(link, message_id, delivery_state);
+        if (result != 0)
+        {
+            LogError("Cannot send disposition frame");
+            result = __FAILURE__;
+        }
+    }
+
+    return result;
+}
+
+void link_dowork(LINK_HANDLE link)
+{
+    if (link == NULL)
+    {
+        LogError("NULL link");
+    }
+    else
+    {
+        tickcounter_ms_t current_tick;
+
+        if (tickcounter_get_current_ms(link->tick_counter, &current_tick) != 0)
+        {
+            LogError("Cannot get tick counter value");
+        }
+        else
+        {
+            // go through all and find timed out deliveries
+            LIST_ITEM_HANDLE item = singlylinkedlist_get_head_item(link->pending_deliveries);
+            while (item != NULL)
+            {
+                LIST_ITEM_HANDLE next_item = singlylinkedlist_get_next_item(item);
+                ASYNC_OPERATION_HANDLE delivery_instance_async_operation = (ASYNC_OPERATION_HANDLE)singlylinkedlist_item_get_value(item);
+                DELIVERY_INSTANCE* delivery_instance = (DELIVERY_INSTANCE*)GET_ASYNC_OPERATION_CONTEXT(DELIVERY_INSTANCE, delivery_instance_async_operation);
+
+                if ((delivery_instance->timeout != 0) &&
+                    (current_tick - delivery_instance->start_tick >= delivery_instance->timeout))
+                {
+                    if (delivery_instance->on_delivery_settled != NULL)
+                    {
+                        delivery_instance->on_delivery_settled(delivery_instance->callback_context, delivery_instance->delivery_id, LINK_DELIVERY_SETTLE_REASON_TIMEOUT, NULL);
+                    }
+
+                    if (singlylinkedlist_remove(link->pending_deliveries, item) != 0)
+                    {
+                        LogError("Cannot remove item from list");
+                    }
+
+                    async_operation_destroy(delivery_instance_async_operation);
+                }
+
+                item = next_item;
+            }
+        }
+    }
+}
+
+ON_LINK_DETACH_EVENT_SUBSCRIPTION_HANDLE link_subscribe_on_link_detach_received(LINK_HANDLE link, ON_LINK_DETACH_RECEIVED on_link_detach_received, void* context)
+{
+    ON_LINK_DETACH_EVENT_SUBSCRIPTION_HANDLE result;
+
+    if ((link == NULL) ||
+        (on_link_detach_received == NULL))
+    {
+        LogError("Invalid arguments: link = %p, on_link_detach_received = %p, context = %p",
+            link, on_link_detach_received, context);
+        result = NULL;
+    }
+    else
+    {
+        if (link->on_link_detach_received_event_subscription.on_link_detach_received != NULL)
+        {
+            LogError("Already subscribed for on_link_detach_received events");
+            result = NULL;
+        }
+        else
+        {
+            link->on_link_detach_received_event_subscription.on_link_detach_received = on_link_detach_received;
+            link->on_link_detach_received_event_subscription.context = context;
+
+            result = &link->on_link_detach_received_event_subscription;
+        }
+    }
+
+    return result;
+}
+
+void link_unsubscribe_on_link_detach_received(ON_LINK_DETACH_EVENT_SUBSCRIPTION_HANDLE event_subscription)
+{
+    if (event_subscription == NULL)
+    {
+        LogError("NULL event_subscription");
+    }
+    else
+    {
+        event_subscription->on_link_detach_received = NULL;
+        event_subscription->context = NULL;
+    }
+}