lib: Manage multiple flows with a single CDAP instance

You can now add multiple flows to a CDAP instance. This will simplify
sending messages to different peers (e.g. for syncing the RIB). A
request will now return an array of keys terminated by
CDAP_KEY_INVALID. Removes the enum from the CDAP proto file to just
take the opcode as an integer.

6 files changed, 287 insertions, 139 deletions

diff --git a/include/ouroboros/cdap.h b/include/ouroboros/cdap.h
index 19ab39a8..32edb51c 100644
--- a/include/ouroboros/cdap.h
+++ b/include/ouroboros/cdap.h
@@ -46,12 +46,17 @@ struct cdap;
 
 typedef int32_t cdap_key_t;
 
-/* Assumes flow is blocking */
-struct cdap * cdap_create(int fd);
+struct cdap * cdap_create(void);
 
 int           cdap_destroy(struct cdap * instance);
 
-cdap_key_t    cdap_request_send(struct cdap *    instance,
+int           cdap_add_flow(struct cdap * instance,
+                            int           fd);
+
+int           cdap_del_flow(struct cdap * instance,
+                            int           fd);
+
+cdap_key_t *  cdap_request_send(struct cdap *    instance,
                                 enum cdap_opcode code,
                                 const char *     name,
                                 const void *     data,
diff --git a/src/ipcpd/normal/enroll.c b/src/ipcpd/normal/enroll.c
index 680cfbba..4e510038 100644
--- a/src/ipcpd/normal/enroll.c
+++ b/src/ipcpd/normal/enroll.c
@@ -78,13 +78,20 @@ static void * enroll_handle(void * o)
                         continue;
                 }
 
-                cdap = cdap_create(conn.flow_info.fd);
+                cdap = cdap_create();
                 if (cdap == NULL) {
                         log_err("Failed to instantiate CDAP.");
                         flow_dealloc(conn.flow_info.fd);
                         continue;
                 }
 
+                if (cdap_add_flow(cdap, conn.flow_info.fd)) {
+                        log_warn("Failed to add flow to CDAP.");
+                        cdap_destroy(cdap);
+                        flow_dealloc(conn.flow_info.fd);
+                        continue;
+                }
+
                 while (!(boot_r && members_r && dif_name_r)) {
                         key = cdap_request_wait(cdap, &oc, &name, &data,
                                                 (size_t *) &len , &flags);
@@ -167,7 +174,7 @@ static void * enroll_handle(void * o)
 int enroll_boot(char * dst_name)
 {
         struct cdap * cdap;
-        cdap_key_t    key;
+        cdap_key_t *  key;
         uint8_t *     data;
         size_t        len;
         struct conn   conn;
@@ -186,31 +193,41 @@ int enroll_boot(char * dst_name)
                 return -1;
         }
 
-        cdap = cdap_create(conn.flow_info.fd);
+        cdap = cdap_create();
         if (cdap == NULL) {
                 log_err("Failed to instantiate CDAP.");
                 return -1;
         }
 
+        if (cdap_add_flow(cdap, conn.flow_info.fd)) {
+                log_warn("Failed to add flow to CDAP.");
+                cdap_destroy(cdap);
+                flow_dealloc(conn.flow_info.fd);
+                return -1;
+        }
+
         log_dbg("Getting boot information from %s.", dst_name);
 
         clock_gettime(CLOCK_REALTIME, &t0);
 
         key = cdap_request_send(cdap, CDAP_READ, TIME_PATH, NULL, 0, 0);
-        if (key < 0) {
+        if (key == NULL) {
                 log_err("Failed to send CDAP request.");
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
-        if (cdap_reply_wait(cdap, key, &data, &len)) {
+        if (cdap_reply_wait(cdap, key[0], &data, &len)) {
                 log_err("Failed to get CDAP reply.");
+                free(key);
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
+        free(key);
+
         clock_gettime(CLOCK_REALTIME, &rtt);
 
         delta_t = ts_diff_ms(&t0, &rtt);
@@ -226,20 +243,23 @@ int enroll_boot(char * dst_name)
         free(data);
 
         key = cdap_request_send(cdap, CDAP_READ, boot_ro, NULL, 0, 0);
-        if (key < 0) {
+        if (key == NULL) {
                 log_err("Failed to send CDAP request.");
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
-        if (cdap_reply_wait(cdap, key, &data, &len)) {
+        if (cdap_reply_wait(cdap, key[0], &data, &len)) {
                 log_err("Failed to get CDAP reply.");
+                free(key);
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
+        free(key);
+
         log_dbg("Packed information received (%zu bytes).", len);
 
         if (rib_unpack(data, len, UNPACK_CREATE)) {
@@ -254,20 +274,23 @@ int enroll_boot(char * dst_name)
         log_dbg("Packed information inserted into RIB.");
 
         key = cdap_request_send(cdap, CDAP_READ, members_ro, NULL, 0, 0);
-        if (key < 0) {
+        if (key == NULL) {
                 log_err("Failed to send CDAP request.");
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
-        if (cdap_reply_wait(cdap, key, &data, &len)) {
+        if (cdap_reply_wait(cdap, key[0], &data, &len)) {
                 log_err("Failed to get CDAP reply.");
+                free(key);
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
+        free(key);
+
         log_dbg("Packed information received (%zu bytes).", len);
 
         if (rib_unpack(data, len, UNPACK_CREATE)) {
@@ -282,20 +305,23 @@ int enroll_boot(char * dst_name)
         log_dbg("Packed information inserted into RIB.");
 
         key = cdap_request_send(cdap, CDAP_READ, dif_ro, NULL, 0, 0);
-        if (key < 0) {
+        if (key == NULL) {
                 log_err("Failed to send CDAP request.");
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
-        if (cdap_reply_wait(cdap, key, &data, &len)) {
+        if (cdap_reply_wait(cdap, key[0], &data, &len)) {
                 log_err("Failed to get CDAP reply.");
+                free(key);
                 cdap_destroy(cdap);
                 flow_dealloc(conn.flow_info.fd);
                 return -1;
         }
 
+        free(key);
+
         log_dbg("Packed information received (%zu bytes).", len);
 
         if (rib_unpack(data, len, UNPACK_CREATE)) {
diff --git a/src/lib/cdap.c b/src/lib/cdap.c
index ba4a2a21..86554dd2 100644
--- a/src/lib/cdap.c
+++ b/src/lib/cdap.c
@@ -25,6 +25,7 @@
 #include <ouroboros/cdap.h>
 #include <ouroboros/bitmap.h>
 #include <ouroboros/dev.h>
+#include <ouroboros/fqueue.h>
 #include <ouroboros/fcntl.h>
 #include <ouroboros/errno.h>
 
@@ -37,28 +38,39 @@
 
 #include "cdap.pb-c.h"
 typedef Cdap cdap_t;
-typedef Opcode opcode_t;
 
 typedef int32_t invoke_id_t;
 
+#define CDAP_REPLY (CDAP_DELETE + 1)
+
 #define INVALID_INVOKE_ID -1
 #define IDS_SIZE 256
 #define BUF_SIZE 2048
 
-struct cdap {
+struct fd_el {
+        struct list_head next;
+
         int              fd;
+};
+
+struct cdap {
+        flow_set_t *     set;
+
+        size_t           n_flows;
+        struct list_head flows;
+        pthread_rwlock_t flows_lock;
 
         struct bmp *     ids;
         pthread_mutex_t  ids_lock;
 
-        pthread_t        reader;
-
         struct list_head sent;
         pthread_rwlock_t sent_lock;
 
         struct list_head rcvd;
         pthread_cond_t   rcvd_cond;
         pthread_mutex_t  rcvd_lock;
+
+        pthread_t        reader;
 };
 
 struct cdap_rcvd {
@@ -133,6 +145,7 @@ static struct cdap_req * cdap_sent_get_by_key(struct cdap * instance,
 }
 
 static struct cdap_req * cdap_sent_add(struct cdap * instance,
+                                       int           fd,
                                        cdap_key_t    key)
 {
         struct cdap_req * req;
@@ -141,7 +154,7 @@ static struct cdap_req * cdap_sent_add(struct cdap * instance,
         assert(key >= 0);
         assert(!cdap_sent_has_key(instance, key));
 
-        req = cdap_req_create(key);
+        req = cdap_req_create(fd, key);
         if (req == NULL)
                 return NULL;
 
@@ -220,9 +233,14 @@ static void * sdu_reader(void * o)
         uint8_t buf[BUF_SIZE];
         ssize_t len;
         buffer_t data;
+        fqueue_t * fq;
 
-        while (true) {
-                len = flow_read(instance->fd, buf, BUF_SIZE);
+        fq = fqueue_create();
+        if (fq == NULL)
+                return (void *) -1;
+
+        while (flow_event_wait(instance->set, fq, NULL)) {
+                len = flow_read(fqueue_next(fq), buf, BUF_SIZE);
                 if (len < 0)
                         continue;
 
@@ -230,41 +248,17 @@ static void * sdu_reader(void * o)
                 if (msg == NULL)
                         continue;
 
-                if (msg->opcode != OPCODE__REPLY) {
+                if (msg->opcode != CDAP_REPLY) {
                         rcvd = malloc(sizeof(*rcvd));
                         if (rcvd == NULL) {
                                 cdap__free_unpacked(msg, NULL);
                                 continue;
                         }
 
-                        switch (msg->opcode) {
-                        case OPCODE__START:
-                                rcvd->opcode = CDAP_START;
-                                break;
-                        case OPCODE__STOP:
-                                rcvd->opcode = CDAP_STOP;
-                                break;
-                        case OPCODE__READ:
-                                rcvd->opcode = CDAP_READ;
-                                break;
-                        case OPCODE__WRITE:
-                                rcvd->opcode = CDAP_WRITE;
-                                break;
-                        case OPCODE__CREATE:
-                                rcvd->opcode = CDAP_CREATE;
-                                break;
-                        case OPCODE__DELETE:
-                                rcvd->opcode = CDAP_DELETE;
-                                break;
-                        default:
-                                cdap__free_unpacked(msg, NULL);
-                                free(rcvd);
-                                continue;
-                        }
-
-                        rcvd->iid   = msg->invoke_id;
-                        rcvd->flags = msg->flags;
-                        rcvd->name  = strdup(msg->name);
+                        rcvd->opcode = msg->opcode;
+                        rcvd->iid    = msg->invoke_id;
+                        rcvd->flags  = msg->flags;
+                        rcvd->name   = strdup(msg->name);
                         if (rcvd->name == NULL) {
                                 cdap__free_unpacked(msg, NULL);
                                 free(rcvd);
@@ -303,7 +297,7 @@ static void * sdu_reader(void * o)
                                         cdap__free_unpacked(msg, NULL);
                                         continue;
                                 }
-                                memcpy(data.data, msg->value.data, data.len);
+                                memcpy(data.data, msg->value.data Iata.len);
                         } else {
                                 data.len = 0;
                                 data.data = NULL;
@@ -311,36 +305,32 @@ static void * sdu_reader(void * o)
 
                         cdap_req_respond(req, msg->result, data);
                 }
-
-                cdap__free_unpacked(msg, NULL);
         }
-
         return (void *) 0;
 }
 
-struct cdap * cdap_create(int fd)
+struct cdap * cdap_create()
 {
         struct cdap * instance = NULL;
-        int flags;
-
-        if (fd < 0)
-                return NULL;
-
-        flags = flow_get_flags(fd);
-        if (flags & FLOW_O_NONBLOCK)
-                return NULL;
 
         instance = malloc(sizeof(*instance));
         if (instance == NULL)
                 return NULL;
 
+        if (pthread_rwlock_init(&instance->flows_lock, NULL)) {
+                free(instance);
+                return NULL;
+        }
+
         if (pthread_mutex_init(&instance->ids_lock, NULL)) {
+                pthread_rwlock_destroy(&instance->flows_lock);
                 free(instance);
                 return NULL;
         }
 
         if (pthread_mutex_init(&instance->rcvd_lock, NULL)) {
                 pthread_mutex_destroy(&instance->ids_lock);
+                pthread_rwlock_destroy(&instance->flows_lock);
                 free(instance);
                 return NULL;
         }
@@ -348,6 +338,7 @@ struct cdap * cdap_create(int fd)
         if (pthread_rwlock_init(&instance->sent_lock, NULL)) {
                 pthread_mutex_destroy(&instance->rcvd_lock);
                 pthread_mutex_destroy(&instance->ids_lock);
+                pthread_rwlock_destroy(&instance->flows_lock);
                 free(instance);
                 return NULL;
         }
@@ -356,6 +347,7 @@ struct cdap * cdap_create(int fd)
                 pthread_rwlock_destroy(&instance->sent_lock);
                 pthread_mutex_destroy(&instance->rcvd_lock);
                 pthread_mutex_destroy(&instance->ids_lock);
+                pthread_rwlock_destroy(&instance->flows_lock);
                 free(instance);
                 return NULL;
         }
@@ -366,15 +358,29 @@ struct cdap * cdap_create(int fd)
                 pthread_rwlock_destroy(&instance->sent_lock);
                 pthread_mutex_destroy(&instance->rcvd_lock);
                 pthread_mutex_destroy(&instance->ids_lock);
+                pthread_rwlock_destroy(&instance->flows_lock);
                 free(instance);
                 return NULL;
         }
 
+        instance->set = flow_set_create();
+        if (instance->set == NULL) {
+                bmp_destroy(instance->ids);
+                pthread_cond_destroy(&instance->rcvd_cond);
+                pthread_rwlock_destroy(&instance->sent_lock);
+                pthread_mutex_destroy(&instance->rcvd_lock);
+                pthread_mutex_destroy(&instance->ids_lock);
+                pthread_rwlock_destroy(&instance->flows_lock);
+                free(instance);
+                return NULL;
+        }
+
+        instance->n_flows = 0;
+
+        list_head_init(&instance->flows);
         list_head_init(&instance->sent);
         list_head_init(&instance->rcvd);
 
-        instance->fd = fd;
-
         pthread_create(&instance->reader, NULL, sdu_reader, instance);
 
         return instance;
@@ -382,12 +388,29 @@ struct cdap * cdap_create(int fd)
 
 int cdap_destroy(struct cdap * instance)
 {
+        struct list_head * p;
+        struct list_head * h;
+
         if (instance == NULL)
                 return 0;
 
         pthread_cancel(instance->reader);
         pthread_join(instance->reader, NULL);
 
+        flow_set_destroy(instance->set);
+
+        pthread_rwlock_wrlock(&instance->flows_lock);
+
+        list_for_each_safe(p,h, &instance->flows) {
+                struct fd_el * e = list_entry(p, struct fd_el, next);
+                list_del(&e->next);
+                free(e);
+        }
+
+        pthread_rwlock_unlock(&instance->flows_lock);
+
+        pthread_rwlock_destroy(&instance->flows_lock);
+
         pthread_mutex_lock(&instance->ids_lock);
 
         bmp_destroy(instance->ids);
@@ -409,14 +432,71 @@ int cdap_destroy(struct cdap * instance)
         return 0;
 }
 
-static int write_msg(struct cdap * instance,
+int cdap_add_flow(struct cdap * instance,
+                  int           fd)
+{
+        struct fd_el * e;
+
+        if (fd < 0)
+                return -EINVAL;
+
+        e = malloc(sizeof(*e));
+        if (e == NULL)
+                return -ENOMEM;
+
+        e->fd = fd;
+
+        pthread_rwlock_wrlock(&instance->flows_lock);
+
+        if (flow_set_add(instance->set, fd)) {
+                pthread_rwlock_unlock(&instance->flows_lock);
+                return -1;
+        }
+
+        list_add(&e->next, &instance->flows);
+
+        ++instance->n_flows;
+
+        pthread_rwlock_unlock(&instance->flows_lock);
+
+        return 0;
+}
+
+int cdap_del_flow(struct cdap * instance,
+                  int           fd)
+{
+        struct list_head * p;
+        struct list_head * h;
+
+        if (fd < 0)
+                return -EINVAL;
+
+        pthread_rwlock_wrlock(&instance->flows_lock);
+
+        flow_set_del(instance->set, fd);
+
+        list_for_each_safe(p, h, &instance->flows) {
+                struct fd_el * e = list_entry(p, struct fd_el, next);
+                if (e->fd == fd) {
+                        list_del(&e->next);
+                        free(e);
+                        break;
+                }
+        }
+
+        --instance->n_flows;
+
+        pthread_rwlock_unlock(&instance->flows_lock);
+
+        return 0;
+}
+
+static int write_msg(int           fd,
                      cdap_t *      msg)
 {
-        int ret;
         uint8_t * data;
         size_t len;
 
-        assert(instance);
         assert(msg);
 
         len = cdap__get_packed_size(msg);
@@ -429,11 +509,14 @@ static int write_msg(struct cdap * instance,
 
         cdap__pack(msg, data);
 
-        ret = flow_write(instance->fd, data, len);
+        if (flow_write(fd, data, len)) {
+                free(data);
+                return -1;
+        }
 
         free(data);
 
-        return ret;
+        return 0;
 }
 
 static cdap_key_t invoke_id_to_key(invoke_id_t iid)
@@ -452,75 +535,114 @@ static invoke_id_t key_to_invoke_id(cdap_key_t key)
         return (invoke_id_t) key;
 }
 
-cdap_key_t cdap_request_send(struct cdap *    instance,
-                             enum cdap_opcode code,
-                             const char *     name,
-                             const void *     data,
-                             size_t           len,
-                             uint32_t         flags)
+cdap_key_t * cdap_request_send(struct cdap *    instance,
+                               enum cdap_opcode code,
+                               const char *     name,
+                               const void *     data,
+                               size_t           len,
+                               uint32_t         flags)
 {
-        cdap_t msg = CDAP__INIT;
-        struct cdap_req * req;
-        invoke_id_t iid;
-        cdap_key_t key;
+        cdap_key_t *       keys;
+        cdap_key_t *       key;
+        cdap_t             msg = CDAP__INIT;
+        struct list_head * p;
+        int                ret;
 
-        if (instance == NULL || name == NULL)
-                return -EINVAL;
+        if (instance == NULL || name == NULL || code > CDAP_DELETE)
+                return NULL;
 
+        pthread_rwlock_rdlock(&instance->flows_lock);
 
-        iid = next_invoke_id(instance);
-        if (iid == INVALID_INVOKE_ID)
-                return INVALID_CDAP_KEY;
+        keys = malloc(sizeof(*keys) * (instance->n_flows + 1));
+        if (keys == NULL)
+                return NULL;
 
-        switch (code) {
-        case CDAP_READ:
-                msg.opcode = OPCODE__READ;
-                break;
-        case CDAP_WRITE:
-                msg.opcode = OPCODE__WRITE;
-                break;
-        case CDAP_CREATE:
-                msg.opcode = OPCODE__CREATE;
-                break;
-        case CDAP_DELETE:
-                msg.opcode = OPCODE__DELETE;
-                break;
-        case CDAP_START:
-                msg.opcode = OPCODE__START;
-                break;
-        case CDAP_STOP:
-                msg.opcode = OPCODE__STOP;
-                break;
-        default:
-                release_invoke_id(instance, iid);
-                return -EINVAL;
-        }
+        memset(keys, INVALID_CDAP_KEY, sizeof(*keys) * (instance->n_flows + 1));
 
+        key = keys;
+
+        msg.opcode = code;
         msg.name = (char *) name;
         msg.has_flags = true;
         msg.flags = flags;
-        msg.invoke_id = iid;
+
         if (data != NULL) {
                 msg.has_value = true;
                 msg.value.data = (uint8_t *) data;
                 msg.value.len = len;
         }
 
-        key = invoke_id_to_key(iid);
+        list_for_each(p, &instance->flows) {
+                struct cdap_req * req;
+                invoke_id_t iid;
+                struct fd_el * e;
+                cdap__init(&msg);
+
+                iid = next_invoke_id(instance);
+                if (iid == INVALID_INVOKE_ID) {
+                        pthread_rwlock_unlock(&instance->flows_lock);
+                        while(key > keys) {
+                                struct cdap_req * r =
+                                        cdap_sent_get_by_key(instance,
+                                                             *(--key));
+                                cdap_sent_del(instance, r);
+                                cdap_req_destroy(r);
+                        }
 
-        req = cdap_sent_add(instance, key);
-        if (req == NULL) {
-                release_invoke_id(instance, iid);
-                return INVALID_CDAP_KEY;
-        }
+                        free(keys);
+                        return NULL;
+                }
 
-        if (write_msg(instance, &msg)) {
-                cdap_sent_del(instance, req);
-                release_invoke_id(instance, iid);
-                return INVALID_CDAP_KEY;
+                msg.invoke_id = iid;
+
+                *key = invoke_id_to_key(iid);
+
+                e = list_entry(p, struct fd_el, next);
+
+                req = cdap_sent_add(instance, e->fd, *key);
+                if (req == NULL) {
+                        pthread_rwlock_unlock(&instance->flows_lock);
+                        while(key > keys) {
+                                struct cdap_req * r =
+                                        cdap_sent_get_by_key(instance,
+                                                             *(--key));
+                                release_invoke_id(instance, iid);
+                                cdap_sent_del(instance, r);
+                                release_invoke_id(instance,
+                                                  key_to_invoke_id(r->key));
+                                cdap_req_destroy(r);
+                        }
+                        free(keys);
+                        return NULL;
+                }
+
+                ret = write_msg(e->fd, &msg);
+                if (ret == -ENOMEM) {
+                        pthread_rwlock_unlock(&instance->flows_lock);
+                        while(key >= keys) {
+                                struct cdap_req * r =
+                                        cdap_sent_get_by_key(instance, *key);
+                                cdap_sent_del(instance, r);
+                                release_invoke_id(instance,
+                                                  key_to_invoke_id(r->key));
+                                cdap_req_destroy(r);
+                        }
+
+                        free(keys);
+                        return NULL;
+                }
+
+                if (ret < 0) {
+                        release_invoke_id(instance, iid);
+                        cdap_sent_del(instance, req);
+                }
+
+                ++key;
         }
 
-        return key;
+        pthread_rwlock_unlock(&instance->flows_lock);
+
+        return keys;
 }
 
 int cdap_reply_wait(struct cdap * instance,
@@ -609,11 +731,14 @@ int cdap_reply_send(struct cdap * instance,
 {
         cdap_t msg = CDAP__INIT;
         invoke_id_t iid = key_to_invoke_id(key);
+        struct cdap_req * req = cdap_sent_get_by_key(instance, key);
+        if (req == NULL)
+                return -EINVAL;
 
         if (instance == NULL)
                 return -EINVAL;
 
-        msg.opcode = OPCODE__REPLY;
+        msg.opcode = CDAP_REPLY;
         msg.invoke_id = iid;
         msg.has_result = true;
         msg.result = result;
@@ -624,5 +749,5 @@ int cdap_reply_send(struct cdap * instance,
                 msg.value.len = len;
         }
 
-        return write_msg(instance, &msg);
+        return write_msg(req->fd, &msg);
 }
diff --git a/src/lib/cdap.proto b/src/lib/cdap.proto
index 5fde1658..120b2c97 100644
--- a/src/lib/cdap.proto
+++ b/src/lib/cdap.proto
@@ -23,18 +23,8 @@
 
 syntax = "proto2";
 
-enum opcode {
-        CREATE = 1;
-        DELETE = 2;
-        READ   = 3;
-        WRITE  = 4;
-        START  = 5;
-        STOP   = 6;
-        REPLY  = 7;
-}
-
 message cdap {
-        required opcode opcode    = 1;
+        required uint32 opcode    = 1;
         required uint32 invoke_id = 2;
         optional uint32 flags     = 3;
         optional string name      = 4;
diff --git a/src/lib/cdap_req.c b/src/lib/cdap_req.c
index a0348a14..b60e73ad 100644
--- a/src/lib/cdap_req.c
+++ b/src/lib/cdap_req.c
@@ -30,7 +30,8 @@
 #include <stdlib.h>
 #include <assert.h>
 
-struct cdap_req * cdap_req_create(cdap_key_t key)
+struct cdap_req * cdap_req_create(int        fd,
+                                  cdap_key_t key)
 {
         struct cdap_req * creq = malloc(sizeof(*creq));
         pthread_condattr_t cattr;
@@ -38,10 +39,10 @@ struct cdap_req * cdap_req_create(cdap_key_t key)
         if (creq == NULL)
                 return NULL;
 
-        creq->key = key;
+        creq->fd        = fd;
+        creq->key       = key;
         creq->state     = REQ_INIT;
-
-        creq->response = -1;
+        creq->response  = -1;
         creq->data.data = NULL;
         creq->data.len  = 0;
 
diff --git a/src/lib/cdap_req.h b/src/lib/cdap_req.h
index 9023357d..fe8e3613 100644
--- a/src/lib/cdap_req.h
+++ b/src/lib/cdap_req.h
@@ -43,8 +43,8 @@ enum creq_state {
 struct cdap_req {
         struct list_head next;
 
+        int              fd;
         struct timespec  birth;
-
         cdap_key_t       key;
 
         int              response;
@@ -55,7 +55,8 @@ struct cdap_req {
         pthread_mutex_t  lock;
 };
 
-struct cdap_req * cdap_req_create(cdap_key_t key);
+struct cdap_req * cdap_req_create(int        fd,
+                                  cdap_key_t key);
 
 void              cdap_req_destroy(struct cdap_req * creq);