ipcpd: Add threadpool manager to DHT

This adds a threadpool manager to the DHT. This was needed because the
detached thread could cause a data race on shutdown.

The threadpool manager is revised to allow multiple instances in a
single program.

The irmd and ipcp now store commands in a buffer (list) instead of a
single buffer before passing it to handler threads.

5 files changed, 404 insertions, 309 deletions

diff --git a/src/ipcpd/ipcp.c b/src/ipcpd/ipcp.c
index 85d543da..513c638a 100644
--- a/src/ipcpd/ipcp.c
+++ b/src/ipcpd/ipcp.c
@@ -36,7 +36,6 @@
 #include <ouroboros/dev.h>
 #include <ouroboros/bitmap.h>
 #include <ouroboros/np1_flow.h>
-#include <ouroboros/tpm.h>
 
 #include "ipcp.h"
 
@@ -44,6 +43,14 @@
 #include <sys/socket.h>
 #include <stdlib.h>
 
+struct cmd {
+        struct list_head next;
+
+        uint8_t          cbuf[IPCP_MSG_BUF_SIZE];
+        size_t           len;
+        int              fd;
+};
+
 void ipcp_sig_handler(int         sig,
                       siginfo_t * info,
                       void *      c)
@@ -107,7 +114,8 @@ static void * acceptloop(void * o)
 
         while (ipcp_get_state() != IPCP_SHUTDOWN &&
                ipcp_get_state() != IPCP_NULL) {
-                ssize_t count;
+                struct cmd * cmd;
+
 #if defined(__FreeBSD__) || defined(__APPLE__)
                 FD_ZERO(&fds);
                 FD_SET(ipcpi.sockfd, &fds);
@@ -122,25 +130,28 @@ static void * acceptloop(void * o)
                                (void *) &tv, sizeof(tv)))
                         log_warn("Failed to set timeout on socket.");
 
-                pthread_mutex_lock(&ipcpi.cmd_lock);
+                cmd = malloc(sizeof(*cmd));
+                if (cmd == NULL) {
+                        log_err("Out of memory");
+                        break;
+                }
 
-                assert(ipcpi.csockfd == -1);
+                pthread_mutex_lock(&ipcpi.cmd_lock);
 
-                count = read(csockfd, ipcpi.cbuf, IPCP_MSG_BUF_SIZE);
-                if (count <= 0) {
+                cmd->len = read(csockfd, cmd->cbuf, IPCP_MSG_BUF_SIZE);
+                if (cmd->len <= 0) {
                         pthread_mutex_unlock(&ipcpi.cmd_lock);
                         log_err("Failed to read from socket.");
                         close(csockfd);
+                        free(cmd);
                         continue;
                 }
 
-                ipcpi.cmd_len = count;
-                ipcpi.csockfd = csockfd;
+                cmd->fd = csockfd;
 
-                pthread_cond_signal(&ipcpi.cmd_cond);
+                list_add(&cmd->next, &ipcpi.cmds);
 
-                while (ipcpi.csockfd != -1)
-                        pthread_cond_wait(&ipcpi.acc_cond, &ipcpi.cmd_lock);
+                pthread_cond_signal(&ipcpi.cmd_cond);
 
                 pthread_mutex_unlock(&ipcpi.cmd_lock);
         }
@@ -159,13 +170,15 @@ static void * mainloop(void * o)
         struct timespec     dl;
         struct timespec     to  = {(IPCP_ACCEPT_TIMEOUT / 1000),
                                    (IPCP_ACCEPT_TIMEOUT % 1000) * MILLION};
-        (void)  o;
+
+        (void) o;
 
         while (true) {
                 int                 ret = 0;
                 ipcp_msg_t          ret_msg  = IPCP_MSG__INIT;
                 dif_info_msg_t      dif_info = DIF_INFO_MSG__INIT;
                 int                 fd       = -1;
+                struct cmd *        cmd;
 
                 ret_msg.code = IPCP_MSG_CODE__IPCP_REPLY;
 
@@ -174,33 +187,34 @@ static void * mainloop(void * o)
 
                 pthread_mutex_lock(&ipcpi.cmd_lock);
 
-                while (ipcpi.csockfd == -1 && ret != -ETIMEDOUT)
+                while (list_is_empty(&ipcpi.cmds) && ret != -ETIMEDOUT)
                         ret = -pthread_cond_timedwait(&ipcpi.cmd_cond,
                                                       &ipcpi.cmd_lock,
                                                       &dl);
 
-                sfd           = ipcpi.csockfd;
-                ipcpi.csockfd = -1;
-
-                if (sfd == -1) {
+                if (ret == -ETIMEDOUT) {
                         pthread_mutex_unlock(&ipcpi.cmd_lock);
-                        if (tpm_check())
+                        if (tpm_check(ipcpi.tpm))
                                 break;
                         continue;
                 }
 
-                pthread_cond_signal(&ipcpi.acc_cond);
+                cmd = list_last_entry(&ipcpi.cmds, struct cmd, next);
+                list_del(&cmd->next);
+
+                pthread_mutex_unlock(&ipcpi.cmd_lock);
+
+                msg = ipcp_msg__unpack(NULL, cmd->len, cmd->cbuf);
+                sfd = cmd->fd;
+
+                free(cmd);
 
-                msg = ipcp_msg__unpack(NULL, ipcpi.cmd_len, ipcpi.cbuf);
                 if (msg == NULL) {
-                        pthread_mutex_unlock(&ipcpi.cmd_lock);
                         close(sfd);
                         continue;
                 }
 
-                pthread_mutex_unlock(&ipcpi.cmd_lock);
-
-                tpm_dec();
+                tpm_dec(ipcpi.tpm);
 
                 switch (msg->code) {
                 case IPCP_MSG_CODE__IPCP_BOOTSTRAP:
@@ -474,7 +488,7 @@ static void * mainloop(void * o)
                 if (buffer.len == 0) {
                         log_err("Failed to pack reply message");
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(ipcpi.tpm);
                         continue;
                 }
 
@@ -482,7 +496,7 @@ static void * mainloop(void * o)
                 if (buffer.data == NULL) {
                         log_err("Failed to create reply buffer.");
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(ipcpi.tpm);
                         continue;
                 }
 
@@ -492,17 +506,17 @@ static void * mainloop(void * o)
                         log_err("Failed to send reply message");
                         free(buffer.data);
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(ipcpi.tpm);
                         continue;
                 }
 
                 free(buffer.data);
                 close(sfd);
 
-                tpm_inc();
+                tpm_inc(ipcpi.tpm);
         }
 
-        tpm_exit();
+        tpm_exit(ipcpi.tpm);
 
         return (void *) 0;
 }
@@ -617,20 +631,14 @@ int ipcp_init(int               argc,
                 goto fail_cmd_cond;
         }
 
-        if (pthread_cond_init(&ipcpi.acc_cond, &cattr)) {
-                log_err("Failed to init convar.");
-                goto fail_acc_cond;
-        }
+        list_head_init(&ipcpi.cmds);
 
         ipcpi.alloc_id = -1;
-        ipcpi.csockfd  = -1;
 
         pthread_condattr_destroy(&cattr);
 
         return 0;
 
- fail_acc_cond:
-        pthread_cond_destroy(&ipcpi.cmd_cond);
  fail_cmd_cond:
         pthread_mutex_destroy(&ipcpi.cmd_lock);
  fail_cmd_lock:
@@ -675,12 +683,14 @@ int ipcp_boot()
         sigaction(SIGHUP,  &sig_act, NULL);
         sigaction(SIGPIPE, &sig_act, NULL);
 
-        if (tpm_init(IPCP_MIN_THREADS, IPCP_ADD_THREADS, mainloop))
-                goto fail_tpm_init;
+        ipcpi.tpm = tpm_create(IPCP_MIN_THREADS, IPCP_ADD_THREADS,
+                               mainloop, NULL);
+        if (ipcpi.tpm == NULL)
+                goto fail_tpm_create;
 
         pthread_sigmask(SIG_BLOCK, &sigset, NULL);
 
-        if (tpm_start())
+        if (tpm_start(ipcpi.tpm))
                 goto fail_tpm_start;
 
         ipcp_set_state(IPCP_INIT);
@@ -696,18 +706,18 @@ int ipcp_boot()
         return 0;
 
  fail_acceptor:
-        tpm_stop();
+        tpm_stop(ipcpi.tpm);
  fail_tpm_start:
-        tpm_fini();
- fail_tpm_init:
+        tpm_destroy(ipcpi.tpm);
+ fail_tpm_create:
         return -1;
 }
 
 void ipcp_shutdown()
 {
         pthread_join(ipcpi.acceptor, NULL);
-        tpm_stop();
-        tpm_fini();
+        tpm_stop(ipcpi.tpm);
+        tpm_destroy(ipcpi.tpm);
 
         log_info("IPCP %d shutting down.", getpid());
 }
@@ -724,7 +734,6 @@ void ipcp_fini()
         pthread_mutex_destroy(&ipcpi.state_mtx);
         pthread_cond_destroy(&ipcpi.alloc_cond);
         pthread_mutex_destroy(&ipcpi.alloc_lock);
-        pthread_cond_destroy(&ipcpi.acc_cond);
         pthread_cond_destroy(&ipcpi.cmd_cond);
         pthread_mutex_destroy(&ipcpi.cmd_lock);
 
diff --git a/src/ipcpd/ipcp.h b/src/ipcpd/ipcp.h
index 1b2a0334..d47d224b 100644
--- a/src/ipcpd/ipcp.h
+++ b/src/ipcpd/ipcp.h
@@ -25,8 +25,10 @@
 
 #include <ouroboros/hash.h>
 #include <ouroboros/ipcp.h>
+#include <ouroboros/list.h>
 #include <ouroboros/qoscube.h>
 #include <ouroboros/sockets.h>
+#include <ouroboros/tpm.h>
 
 #include <pthread.h>
 #include <time.h>
@@ -92,10 +94,7 @@ struct ipcp {
         int                sockfd;
         char *             sock_path;
 
-        uint8_t            cbuf[IPCP_MSG_BUF_SIZE];
-        size_t             cmd_len;
-        int                csockfd;
-        pthread_cond_t     acc_cond;
+        struct list_head   cmds;
         pthread_cond_t     cmd_cond;
         pthread_mutex_t    cmd_lock;
 
@@ -103,6 +102,8 @@ struct ipcp {
         pthread_cond_t     alloc_cond;
         pthread_mutex_t    alloc_lock;
 
+        struct tpm *       tpm;
+
         pthread_t          acceptor;
 } ipcpi;
 
diff --git a/src/ipcpd/normal/dht.c b/src/ipcpd/normal/dht.c
index 548ae03a..93fd4e4e 100644
--- a/src/ipcpd/normal/dht.c
+++ b/src/ipcpd/normal/dht.c
@@ -34,6 +34,7 @@
 #include <ouroboros/notifier.h>
 #include <ouroboros/random.h>
 #include <ouroboros/time_utils.h>
+#include <ouroboros/tpm.h>
 #include <ouroboros/utils.h>
 
 #include "connmgr.h"
@@ -67,6 +68,7 @@ typedef KadContactMsg kad_contact_msg_t;
 #define KAD_RESP_RETR 6    /* Number of retries on sending a response.   */
 #define KAD_JOIN_RETR 5    /* Number of retries sending a join.          */
 #define KAD_JOIN_INTV 1    /* Time (seconds) between join retries.       */
+#define HANDLE_TIMEO  1000 /* Timeout for dht_handle_sdu tpm check (ms)  */
 
 enum dht_state {
         DHT_INIT = 0,
@@ -187,6 +189,12 @@ struct bucket {
         struct bucket *  children[1L << KAD_BETA];
 };
 
+struct cmd {
+        struct list_head     next;
+
+        struct shm_du_buff * sdb;
+};
+
 struct dht {
         size_t           alpha;
         size_t           b;
@@ -212,6 +220,7 @@ struct dht {
         struct bmp *     cookies;
 
         enum dht_state   state;
+        struct list_head cmds;
         pthread_cond_t   cond;
         pthread_mutex_t  mtx;
 
@@ -219,6 +228,8 @@ struct dht {
 
         int              fd;
 
+        struct tpm *     tpm;
+
         pthread_t        worker;
 };
 
@@ -1428,7 +1439,9 @@ static int send_msg(struct dht * dht,
         ipcp_sdb_release(sdb);
 #endif
  fail_msg:
+        pthread_rwlock_wrlock(&dht->lock);
         bmp_release(dht->cookies, msg->cookie);
+        pthread_rwlock_unlock(&dht->lock);
  fail_bmp_alloc:
         return -1;
 }
@@ -1838,7 +1851,7 @@ static ssize_t dht_get_contacts(struct dht *          dht,
 
         list_head_init(&l);
 
-        pthread_rwlock_rdlock(&dht->lock);
+        pthread_rwlock_wrlock(&dht->lock);
 
         len = dht_contact_list(dht, &l, key);
         if (len == 0) {
@@ -1898,9 +1911,13 @@ static void * work(void * o)
 
         dht = (struct dht *) o;
 
+        pthread_rwlock_rdlock(&dht->lock);
+
         intv = gcd(dht->t_expire, dht->t_repub);
         intv = gcd(intv, gcd(KAD_T_REPL, KAD_T_REFR)) / 2;
 
+        pthread_rwlock_unlock(&dht->lock);
+
         list_head_init(&reflist);
 
         while (true) {
@@ -2189,7 +2206,7 @@ int dht_reg(struct dht *    dht,
 
         pthread_rwlock_unlock(&dht->lock);
 
-        kad_publish(dht, key, >addr, t_expire);
+        kad_publish(dht, key, addr, t_expire);
 
         return 0;
 }
@@ -2271,163 +2288,192 @@ uint64_t dht_query(struct dht *    dht,
 
 static void * dht_handle_sdu(void * o)
 {
-        struct dht *         dht;
-        struct shm_du_buff * sdb;
-        kad_msg_t *          msg;
-        kad_contact_msg_t ** cmsgs;
-        kad_msg_t            resp_msg = KAD_MSG__INIT;
-        uint64_t             addr;
-        buffer_t             buf;
-        size_t               i;
-        size_t               b;
-        size_t               t_expire;
+        struct dht *    dht = (struct dht *) o;
+        struct timespec dl;
+        struct timespec to = {(HANDLE_TIMEO / 1000),
+                              (HANDLE_TIMEO % 1000) * MILLION};
+        assert(dht);
 
-        assert(o);
+        while (true) {
+                kad_msg_t *          msg;
+                kad_contact_msg_t ** cmsgs;
+                kad_msg_t            resp_msg = KAD_MSG__INIT;
+                uint64_t             addr;
+                buffer_t             buf;
+                size_t               i;
+                size_t               b;
+                size_t               t_expire;
+                struct cmd *         cmd;
+                int                  ret = 0;
+
+                clock_gettime(PTHREAD_COND_CLOCK, &dl);
+                ts_add(&dl, &to, &dl);
+
+                pthread_mutex_lock(&dht->mtx);
+
+                while(list_is_empty(&dht->cmds) && ret != -ETIMEDOUT)
+                        ret = -pthread_cond_timedwait(&dht->cond,
+                                                      &dht->mtx, &dl);
+
+                if (ret == -ETIMEDOUT) {
+                        pthread_mutex_unlock(&dht->mtx);
+                        if (tpm_check(dht->tpm))
+                                break;
+                        continue;
+                }
 
-        memset(&buf, 0, sizeof(buf));
+                cmd = list_last_entry(&dht->cmds, struct cmd, next);
+                list_del(&cmd->next);
 
-        dht = ((struct sdu_info *) o)->dht;
-        sdb = ((struct sdu_info *) o)->sdb;
+                pthread_mutex_unlock(&dht->mtx);
 
-        assert(dht);
-        assert(sdb);
+                i = shm_du_buff_tail(cmd->sdb) - shm_du_buff_head(cmd->sdb);
 
-        msg = kad_msg__unpack(NULL,
-                              shm_du_buff_tail(sdb) - shm_du_buff_head(sdb),
-                              shm_du_buff_head(sdb));
+                msg = kad_msg__unpack(NULL, i, shm_du_buff_head(cmd->sdb));
 
-        ipcp_sdb_release(sdb);
+                ipcp_sdb_release(cmd->sdb);
+                free(cmd);
 
-        free(o);
+                if (msg == NULL) {
+                        log_err("Failed to unpack message.");
+                        continue;
+                }
 
-        if (msg == NULL) {
-                log_err("Failed to unpack message.");
-                return (void *) -1;
-        }
+                pthread_rwlock_rdlock(&dht->lock);
 
-        pthread_rwlock_rdlock(&dht->lock);
+                b        = dht->b;
+                t_expire = dht->t_expire;
 
-        b        = dht->b;
-        t_expire = dht->t_expire;
+                pthread_rwlock_unlock(&dht->lock);
 
-        pthread_rwlock_unlock(&dht->lock);
+                if (msg->has_key && msg->key.len != b) {
+                        kad_msg__free_unpacked(msg, NULL);
+                        log_warn("Bad key in message.");
+                        continue;
+                }
 
-        if (msg->has_key && msg->key.len != b) {
-                kad_msg__free_unpacked(msg, NULL);
-                log_warn("Bad key in message.");
-                return (void *) -1;
-        }
+                if (msg->has_s_id && !msg->has_b && msg->s_id.len != b) {
+                        kad_msg__free_unpacked(msg, NULL);
+                        log_warn("Bad source ID in message of type %d.",
+                                 msg->code);
+                        continue;
+                }
 
-        if (msg->has_s_id && !msg->has_b && msg->s_id.len != b) {
-                kad_msg__free_unpacked(msg, NULL);
-                log_warn("Bad source ID in message of type %d.", msg->code);
-                return (void *) -1;
-        }
+                if (msg->code != KAD_RESPONSE && dht_wait_running(dht)) {
+                        kad_msg__free_unpacked(msg, NULL);
+                        log_dbg("Got a request message when not running.");
+                        continue;
+                }
 
-        if (msg->code != KAD_RESPONSE && dht_wait_running(dht)) {
-                kad_msg__free_unpacked(msg, NULL);
-                log_dbg("Got a request message when not running.");
-                return (void *) -1;
-        }
+                tpm_dec(dht->tpm);
 
-        addr = msg->s_addr;
+                addr = msg->s_addr;
 
-        resp_msg.code   = KAD_RESPONSE;
-        resp_msg.cookie = msg->cookie;
+                resp_msg.code   = KAD_RESPONSE;
+                resp_msg.cookie = msg->cookie;
 
-        switch(msg->code) {
-        case KAD_JOIN:
-                /* Refuse enrollee on check fails. */
-                if (msg->alpha != KAD_ALPHA || msg->k != KAD_K) {
-                        log_warn("Parameter mismatch. "
-                                 "DHT enrolment refused.");
-                        break;
-                }
+                switch(msg->code) {
+                case KAD_JOIN:
+                        /* Refuse enrollee on check fails. */
+                        if (msg->alpha != KAD_ALPHA || msg->k != KAD_K) {
+                                log_warn("Parameter mismatch. "
+                                         "DHT enrolment refused.");
+                                break;
+                        }
 
-                if (msg->t_replicate != KAD_T_REPL) {
-                        log_warn("Replication time mismatch. "
-                                 "DHT enrolment refused.");
+                        if (msg->t_replicate != KAD_T_REPL) {
+                                log_warn("Replication time mismatch. "
+                                         "DHT enrolment refused.");
 
-                        break;
+                                break;
                 }
 
-                if (msg->t_refresh != KAD_T_REFR) {
-                        log_warn("Refresh time mismatch. "
-                                 "DHT enrolment refused.");
+                        if (msg->t_refresh != KAD_T_REFR) {
+                                log_warn("Refresh time mismatch. "
+                                         "DHT enrolment refused.");
+                                break;
+                        }
+
+                        resp_msg.has_alpha       = true;
+                        resp_msg.has_b           = true;
+                        resp_msg.has_k           = true;
+                        resp_msg.has_t_expire    = true;
+                        resp_msg.has_t_refresh   = true;
+                        resp_msg.has_t_replicate = true;
+                        resp_msg.alpha           = KAD_ALPHA;
+                        resp_msg.b               = b;
+                        resp_msg.k               = KAD_K;
+                        resp_msg.t_expire        = t_expire;
+                        resp_msg.t_refresh       = KAD_T_REFR;
+                        resp_msg.t_replicate     = KAD_T_REPL;
                         break;
-                }
+                case KAD_FIND_VALUE:
+                        buf = dht_retrieve(dht, msg->key.data);
+                        if (buf.len != 0) {
+                                resp_msg.n_addrs = buf.len;
+                                resp_msg.addrs   = (uint64_t *) buf.data;
+                                break;
+                        }
+                        /* FALLTHRU */
+                case KAD_FIND_NODE:
+                        /* Return k closest contacts. */
+                        resp_msg.n_contacts =
+                                dht_get_contacts(dht, msg->key.data, &cmsgs);
+                        resp_msg.contacts = cmsgs;
+                        break;
+                case KAD_STORE:
+                        if (msg->n_contacts < 1) {
+                                log_warn("No contacts in store message.");
+                                break;
+                        }
 
-                resp_msg.has_alpha       = true;
-                resp_msg.has_b           = true;
-                resp_msg.has_k           = true;
-                resp_msg.has_t_expire    = true;
-                resp_msg.has_t_refresh   = true;
-                resp_msg.has_t_replicate = true;
-                resp_msg.alpha           = KAD_ALPHA;
-                resp_msg.b               = b;
-                resp_msg.k               = KAD_K;
-                resp_msg.t_expire        = t_expire;
-                resp_msg.t_refresh       = KAD_T_REFR;
-                resp_msg.t_replicate     = KAD_T_REPL;
-                break;
-        case KAD_FIND_VALUE:
-                buf = dht_retrieve(dht, msg->key.data);
-                if (buf.len != 0) {
-                        resp_msg.n_addrs = buf.len;
-                        resp_msg.addrs   = (uint64_t *) buf.data;
+                        if (!msg->has_t_expire) {
+                                log_warn("No expiry time in store message.");
+                                break;
+                        }
+
+                        kad_add(dht, *msg->contacts, msg->n_contacts,
+                                msg->t_expire);
                         break;
-                }
-                /* FALLTHRU */
-        case KAD_FIND_NODE:
-                /* Return k closest contacts. */
-                resp_msg.n_contacts =
-                        dht_get_contacts(dht, msg->key.data, &cmsgs);
-                resp_msg.contacts = cmsgs;
-                break;
-        case KAD_STORE:
-                if (msg->n_contacts < 1) {
-                        log_warn("No contacts in store message.");
+                case KAD_RESPONSE:
+                        kad_handle_response(dht, msg);
+                        break;
+                default:
+                        assert(false);
                         break;
                 }
 
-                if (!msg->has_t_expire) {
-                        log_warn("No expiry time in store message.");
-                        break;
+                if (msg->code != KAD_JOIN) {
+                        pthread_rwlock_wrlock(&dht->lock);
+                        if (dht_update_bucket(dht, msg->s_id.data, addr))
+                                log_warn("Failed to update bucket.");
+                        pthread_rwlock_unlock(&dht->lock);
                 }
 
-                kad_add(dht, *msg->contacts, msg->n_contacts, msg->t_expire);
-                break;
-        case KAD_RESPONSE:
-                kad_handle_response(dht, msg);
-                break;
-        default:
-                assert(false);
-                break;
-        }
+                if (msg->code < KAD_STORE) {
+                        if (send_msg(dht, &resp_msg, addr))
+                                log_warn("Failed to send response.");
+                }
 
-        if (msg->code != KAD_JOIN) {
-                pthread_rwlock_wrlock(&dht->lock);
-                if (dht_update_bucket(dht, msg->s_id.data, addr))
-                        log_warn("Failed to update bucket.");
-                pthread_rwlock_unlock(&dht->lock);
-        }
+                kad_msg__free_unpacked(msg, NULL);
 
-        if (msg->code < KAD_STORE) {
-                if (send_msg(dht, &resp_msg, addr))
-                        log_warn("Failed to send response.");
-        }
+                if (resp_msg.n_addrs > 0)
+                        free(resp_msg.addrs);
 
-        kad_msg__free_unpacked(msg, NULL);
+                if (resp_msg.n_contacts == 0) {
+                        tpm_inc(dht->tpm);
+                        continue;
+                }
 
-        if (resp_msg.n_addrs > 0)
-                free(resp_msg.addrs);
+                for (i = 0; i < resp_msg.n_contacts; ++i)
+                        kad_contact_msg__free_unpacked(resp_msg.contacts[i],
+                                                       NULL);
+                free(resp_msg.contacts);
 
-        if (resp_msg.n_contacts == 0)
-                return (void *) -1;
+                tpm_inc(dht->tpm);
+        }
 
-        for (i = 0; i < resp_msg.n_contacts; ++i)
-                kad_contact_msg__free_unpacked(resp_msg.contacts[i], NULL);
-        free(resp_msg.contacts);
+        tpm_exit(dht->tpm);
 
         return (void *) 0;
 }
@@ -2435,22 +2481,24 @@ static void * dht_handle_sdu(void * o)
 static void dht_post_sdu(void *               comp,
                          struct shm_du_buff * sdb)
 {
-        pthread_t         thr;
-        struct sdu_info * info;
+        struct cmd * cmd;
+        struct dht * dht = (struct dht *) comp;
 
-        info = malloc(sizeof(*info));
-        if (info == NULL)
+        cmd = malloc(sizeof(*cmd));
+        if (cmd == NULL) {
+                log_err("Command failed. Out of memory.");
                 return;
+        }
 
-        info->dht = (struct dht *) comp;
-        info->sdb = sdb;
+        cmd->sdb = sdb;
 
-        if (pthread_create(&thr, NULL, dht_handle_sdu, info)) {
-                free(info);
-                return;
-        }
+        pthread_mutex_lock(&dht->mtx);
+
+        list_add(&cmd->next, &dht->cmds);
 
-        pthread_detach(thr);
+        pthread_cond_signal(&dht->cond);
+
+        pthread_mutex_unlock(&dht->mtx);
 }
 
 void dht_destroy(struct dht * dht)
@@ -2461,6 +2509,11 @@ void dht_destroy(struct dht * dht)
         if (dht == NULL)
                 return;
 
+#ifndef __DHT_TEST__
+        tpm_stop(dht->tpm);
+
+        tpm_destroy(dht->tpm);
+#endif
         if (dht_get_state(dht) == DHT_RUNNING) {
                 dht_set_state(dht, DHT_SHUTDOWN);
                 pthread_cancel(dht->worker);
@@ -2594,6 +2647,7 @@ struct dht * dht_create(uint64_t addr)
         list_head_init(&dht->requests);
         list_head_init(&dht->refs);
         list_head_init(&dht->lookups);
+        list_head_init(&dht->cmds);
 
         if (pthread_rwlock_init(&dht->lock, NULL))
                 goto fail_rwlock;
@@ -2612,16 +2666,29 @@ struct dht * dht_create(uint64_t addr)
         dht->addr = addr;
         dht->id   = NULL;
 #ifndef __DHT_TEST__
+        dht->tpm = tpm_create(2, 1, dht_handle_sdu, dht);
+        if (dht->tpm == NULL)
+                goto fail_tpm_create;
+
+        if (tpm_start(dht->tpm))
+                goto fail_tpm_start;
+
         dht->fd   = dt_reg_ae(dht, &dht_post_sdu);
         notifier_reg(handle_event, dht);
 #else
         (void) handle_event;
+        (void) dht_handle_sdu;
         (void) dht_post_sdu;
 #endif
         dht->state = DHT_INIT;
 
         return dht;
-
+#ifndef __DHT_TEST__
+ fail_tpm_start:
+        tpm_destroy(dht->tpm);
+ fail_tpm_create:
+        bmp_destroy(dht->cookies);
+#endif
  fail_bmp:
         pthread_cond_destroy(&dht->cond);
  fail_cond:
diff --git a/src/irmd/main.c b/src/irmd/main.c
index 27c771a6..3fceadb6 100644
--- a/src/irmd/main.c
+++ b/src/irmd/main.c
@@ -93,6 +93,14 @@ enum irm_state {
         IRMD_RUNNING
 };
 
+struct cmd {
+        struct list_head next;
+
+        uint8_t          cbuf[IB_LEN];
+        size_t           len;
+        int              fd;
+};
+
 struct {
         struct list_head     registry;     /* registered names known     */
 
@@ -112,16 +120,15 @@ struct {
 
         int                  sockfd;       /* UNIX socket                */
 
-        uint8_t              cbuf[IB_LEN]; /* cmd message buffer         */
-        size_t               cmd_len;      /* length of cmd in cbuf      */
-        int                  csockfd;      /* cmd UNIX socket            */
-        pthread_cond_t       acc_cond;     /* cmd accepted condvar       */
+        struct list_head     cmds;         /* pending commands           */
         pthread_cond_t       cmd_cond;     /* cmd signal condvar         */
         pthread_mutex_t      cmd_lock;     /* cmd signal lock            */
 
         enum irm_state       state;        /* state of the irmd          */
         pthread_rwlock_t     state_lock;   /* lock for the entire irmd   */
 
+        struct tpm *         tpm;          /* thread pool manager        */
+
         pthread_t            irm_sanitize; /* clean up irmd resources    */
         pthread_t            shm_sanitize; /* keep track of rdrbuff use  */
         pthread_t            acceptor;     /* accept new commands        */
@@ -1631,7 +1638,6 @@ static void irm_fini(void)
                 lockfile_destroy(irmd.lf);
 
         pthread_mutex_destroy(&irmd.cmd_lock);
-        pthread_cond_destroy(&irmd.acc_cond);
         pthread_cond_destroy(&irmd.cmd_cond);
         pthread_rwlock_destroy(&irmd.reg_lock);
         pthread_rwlock_destroy(&irmd.state_lock);
@@ -1864,7 +1870,8 @@ static void * acceptloop(void * o)
         (void) o;
 
         while (irmd_get_state() == IRMD_RUNNING) {
-                ssize_t count;
+                struct cmd * cmd;
+
 #if defined(__FreeBSD__) || defined(__APPLE__)
                 FD_ZERO(&fds);
                 FD_SET(irmd.sockfd, &fds);
@@ -1879,25 +1886,28 @@ static void * acceptloop(void * o)
                                (void *) &tv, sizeof(tv)))
                         log_warn("Failed to set timeout on socket.");
 
-                pthread_mutex_lock(&irmd.cmd_lock);
+                cmd = malloc(sizeof(*cmd));
+                if (cmd == NULL) {
+                        log_err("Out of memory.");
+                        break;
+                }
 
-                assert(irmd.csockfd == -1);
+                pthread_mutex_lock(&irmd.cmd_lock);
 
-                count = read(csockfd, irmd.cbuf, IRM_MSG_BUF_SIZE);
-                if (count <= 0) {
+                cmd->len = read(csockfd, cmd->cbuf, IRM_MSG_BUF_SIZE);
+                if (cmd->len <= 0) {
                         pthread_mutex_unlock(&irmd.cmd_lock);
                         log_err("Failed to read from socket.");
                         close(csockfd);
+                        free(cmd);
                         continue;
                 }
 
-                irmd.cmd_len = count;
-                irmd.csockfd = csockfd;
+                cmd->fd  = csockfd;
 
-                pthread_cond_signal(&irmd.cmd_cond);
+                list_add(&cmd->next, &irmd.cmds);
 
-                while(irmd.csockfd != -1)
-                        pthread_cond_wait(&irmd.acc_cond, &irmd.cmd_lock);
+                pthread_cond_signal(&irmd.cmd_cond);
 
                 pthread_mutex_unlock(&irmd.cmd_lock);
         }
@@ -1923,6 +1933,7 @@ void * mainloop(void * o)
                 pid_t *           apis    = NULL;
                 struct timespec * timeo   = NULL;
                 struct timespec   ts      = {0, 0};
+                struct cmd *      cmd;
 
                 ret_msg.code = IRM_MSG_CODE__IRM_REPLY;
 
@@ -1931,33 +1942,34 @@ void * mainloop(void * o)
 
                 pthread_mutex_lock(&irmd.cmd_lock);
 
-                while (irmd.csockfd == -1 && ret != -ETIMEDOUT)
+                while (list_is_empty(&irmd.cmds) && ret != -ETIMEDOUT)
                         ret = -pthread_cond_timedwait(&irmd.cmd_cond,
                                                       &irmd.cmd_lock,
                                                       &dl);
 
-                sfd          = irmd.csockfd;
-                irmd.csockfd = -1;
-
-                if (sfd == -1) {
+                if (ret == -ETIMEDOUT) {
                         pthread_mutex_unlock(&irmd.cmd_lock);
-                        if (tpm_check())
+                        if (tpm_check(irmd.tpm))
                                 break;
                         continue;
                 }
 
-                pthread_cond_signal(&irmd.acc_cond);
+                cmd = list_last_entry(&irmd.cmds, struct cmd, next);
+                list_del(&cmd->next);
+
+                pthread_mutex_unlock(&irmd.cmd_lock);
+
+                msg = irm_msg__unpack(NULL, cmd->len, cmd->cbuf);
+                sfd = cmd->fd;
+
+                free(cmd);
 
-                msg = irm_msg__unpack(NULL, irmd.cmd_len, irmd.cbuf);
                 if (msg == NULL) {
-                        pthread_mutex_unlock(&irmd.cmd_lock);
                         close(sfd);
                         continue;
                 }
 
-                pthread_mutex_unlock(&irmd.cmd_lock);
-
-                tpm_dec();
+                tpm_dec(irmd.tpm);
 
                 if (msg->has_timeo_sec) {
                         assert(msg->has_timeo_nsec);
@@ -2098,7 +2110,7 @@ void * mainloop(void * o)
 
                 if (ret_msg.result == -EPIPE || !ret_msg.has_result) {
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(irmd.tpm);
                         continue;
                 }
 
@@ -2108,7 +2120,7 @@ void * mainloop(void * o)
                         if (apis != NULL)
                                 free(apis);
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(irmd.tpm);
                         continue;
                 }
 
@@ -2117,7 +2129,7 @@ void * mainloop(void * o)
                         if (apis != NULL)
                                 free(apis);
                         close(sfd);
-                        tpm_inc();
+                        tpm_inc(irmd.tpm);
                         continue;
                 }
 
@@ -2133,10 +2145,10 @@ void * mainloop(void * o)
                 free(buffer.data);
                 close(sfd);
 
-                tpm_inc();
+                tpm_inc(irmd.tpm);
         }
 
-        tpm_exit();
+        tpm_exit(irmd.tpm);
 
         return (void *) 0;
 }
@@ -2184,12 +2196,6 @@ static int irm_init(void)
                 goto fail_cmd_cond;
         }
 
-        if (pthread_cond_init(&irmd.acc_cond, &cattr)) {
-                log_err("Failed to initialize condvar.");
-                pthread_condattr_destroy(&cattr);
-                goto fail_acc_cond;
-        }
-
         pthread_condattr_destroy(&cattr);
 
         list_head_init(&irmd.ipcps);
@@ -2198,6 +2204,7 @@ static int irm_init(void)
         list_head_init(&irmd.spawned_apis);
         list_head_init(&irmd.registry);
         list_head_init(&irmd.irm_flows);
+        list_head_init(&irmd.cmds);
 
         irmd.port_ids = bmp_create(SYS_MAX_FLOWS, 0);
         if (irmd.port_ids == NULL) {
@@ -2272,7 +2279,6 @@ static int irm_init(void)
         gcry_control(GCRYCTL_INITIALIZATION_FINISHED);
 #endif
 
-        irmd.csockfd = -1;
         irmd.state   = IRMD_RUNNING;
 
         log_info("Ouroboros IPC Resource Manager daemon started...");
@@ -2294,8 +2300,6 @@ static int irm_init(void)
  fail_lockfile:
         bmp_destroy(irmd.port_ids);
  fail_port_ids:
-        pthread_cond_destroy(&irmd.acc_cond);
- fail_acc_cond:
         pthread_cond_destroy(&irmd.cmd_cond);
  fail_cmd_cond:
         pthread_mutex_destroy(&irmd.cmd_lock);
@@ -2367,12 +2371,14 @@ int main(int     argc,
         if (irm_init() < 0)
                 goto fail_irm_init;
 
-        if (tpm_init(IRMD_MIN_THREADS, IRMD_ADD_THREADS, mainloop)) {
+        irmd.tpm = tpm_create(IRMD_MIN_THREADS, IRMD_ADD_THREADS,
+                              mainloop, NULL);
+        if (irmd.tpm == NULL) {
                 irmd_set_state(IRMD_NULL);
-                goto fail_tpm_init;
+                goto fail_tpm_create;
         }
 
-        if (tpm_start()) {
+        if (tpm_start(irmd.tpm)) {
                 irmd_set_state(IRMD_NULL);
                 goto fail_tpm_start;
         }
@@ -2396,9 +2402,9 @@ int main(int     argc,
         pthread_join(irmd.irm_sanitize, NULL);
         pthread_join(irmd.shm_sanitize, NULL);
 
-        tpm_stop();
+        tpm_stop(irmd.tpm);
 
-        tpm_fini();
+        tpm_destroy(irmd.tpm);
 
         pthread_sigmask(SIG_BLOCK, &sigset, NULL);
 
@@ -2417,10 +2423,10 @@ int main(int     argc,
  fail_shm_sanitize:
         pthread_join(irmd.irm_sanitize, NULL);
  fail_irm_sanitize:
-        tpm_stop();
+        tpm_stop(irmd.tpm);
  fail_tpm_start:
-        tpm_fini();
- fail_tpm_init:
+        tpm_destroy(irmd.tpm);
+ fail_tpm_create:
         irm_fini();
  fail_irm_init:
         log_fini();
diff --git a/src/lib/tpm.c b/src/lib/tpm.c
index dd71d276..c883e0a8 100644
--- a/src/lib/tpm.c
+++ b/src/lib/tpm.c
@@ -50,38 +50,38 @@ enum tpm_state {
         TPM_RUNNING
 };
 
-struct {
+struct tpm {
         size_t           min;
         size_t           inc;
         size_t           cur;
         size_t           wrk;
 
         void * (* func)(void *);
+        void *           o;
 
         struct list_head pool;
 
         enum tpm_state   state;
-
         pthread_cond_t   cond;
         pthread_mutex_t  lock;
 
         pthread_t        mgr;
-} tpm;
+};
 
-static void tpm_join(void)
+static void tpm_join(struct tpm * tpm)
 {
         struct list_head * p;
         struct list_head * h;
 
-        list_for_each_safe(p, h, &tpm.pool) {
+        list_for_each_safe(p, h, &tpm->pool) {
                 struct pthr_el * e = list_entry(p, struct pthr_el, next);
-                if (tpm.state != TPM_RUNNING) {
+                if (tpm->state != TPM_RUNNING) {
                         if (!e->kill) {
                                 e->kill = true;
-                                --tpm.cur;
+                                --tpm->cur;
                         }
                         while (!e->join)
-                                pthread_cond_wait(&tpm.cond, &tpm.lock);
+                                pthread_cond_wait(&tpm->cond, &tpm->lock);
                 }
 
                 if (e->join) {
@@ -92,12 +92,13 @@ static void tpm_join(void)
         }
 }
 
-static struct pthr_el * tpm_pthr_el(pthread_t thr)
+static struct pthr_el * tpm_pthr_el(struct tpm * tpm,
+                                    pthread_t    thr)
 {
         struct list_head * p;
         struct pthr_el *   e;
 
-        list_for_each(p, &tpm.pool) {
+        list_for_each(p, &tpm->pool) {
                 e = list_entry(p, struct pthr_el, next);
                 if (e->thr == thr)
                         return e;
@@ -109,15 +110,15 @@ static struct pthr_el * tpm_pthr_el(pthread_t thr)
         return NULL;
 }
 
-static void tpm_kill(void)
+static void tpm_kill(struct tpm * tpm)
 {
         struct list_head * p;
 
-        list_for_each(p, &tpm.pool) {
+        list_for_each(p, &tpm->pool) {
                 struct pthr_el * e = list_entry(p, struct pthr_el, next);
                 if (!e->kill) {
                         e->kill = true;
-                        --tpm.cur;
+                        --tpm->cur;
                         return;
                 }
         }
@@ -128,25 +129,25 @@ static void * tpmgr(void * o)
         struct timespec dl;
         struct timespec to = {(TPM_TIMEOUT / 1000),
                               (TPM_TIMEOUT % 1000) * MILLION};
-        (void) o;
+        struct tpm * tpm = (struct tpm *) o;
 
         while (true) {
                 clock_gettime(PTHREAD_COND_CLOCK, &dl);
                 ts_add(&dl, &to, &dl);
 
-                pthread_mutex_lock(&tpm.lock);
+                pthread_mutex_lock(&tpm->lock);
 
-                if (tpm.state != TPM_RUNNING) {
-                        tpm_join();
-                        pthread_mutex_unlock(&tpm.lock);
+                if (tpm->state != TPM_RUNNING) {
+                        tpm_join(tpm);
+                        pthread_mutex_unlock(&tpm->lock);
                         break;
                 }
 
-                tpm_join();
+                tpm_join(tpm);
 
-                if (tpm.cur - tpm.wrk < tpm.min) {
+                if (tpm->cur - tpm->wrk < tpm->min) {
                         size_t i;
-                        for (i = 0; i < tpm.inc; ++i) {
+                        for (i = 0; i < tpm->inc; ++i) {
                                 struct pthr_el * e = malloc(sizeof(*e));
                                 if (e == NULL)
                                         break;
@@ -155,35 +156,41 @@ static void * tpmgr(void * o)
                                 e->kill = false;
 
                                 if (pthread_create(&e->thr, NULL,
-                                                   tpm.func, NULL)) {
+                                                   tpm->func, tpm->o)) {
                                         free(e);
                                         break;
                                 }
 
-                                list_add(&e->next, &tpm.pool);
+                                list_add(&e->next, &tpm->pool);
                         }
 
-                        tpm.cur += i;
+                        tpm->cur += i;
                 }
 
-                if (pthread_cond_timedwait(&tpm.cond, &tpm.lock, &dl)
+                if (pthread_cond_timedwait(&tpm->cond, &tpm->lock, &dl)
                     == ETIMEDOUT)
-                        if (tpm.cur > tpm.min)
-                                tpm_kill();
+                        if (tpm->cur > tpm->min)
+                                tpm_kill(tpm);
 
-                pthread_mutex_unlock(&tpm.lock);
+                pthread_mutex_unlock(&tpm->lock);
         }
 
         return (void *) 0;
 }
 
-int tpm_init(size_t min,
-             size_t inc,
-             void * (* func)(void *))
+struct tpm * tpm_create(size_t min,
+                        size_t inc,
+                        void * (* func)(void *),
+                        void * o)
 {
+        struct tpm *       tpm;
         pthread_condattr_t cattr;
 
-        if (pthread_mutex_init(&tpm.lock, NULL))
+        tpm = malloc(sizeof(*tpm));
+        if (tpm == NULL)
+                goto fail_malloc;
+
+        if (pthread_mutex_init(&tpm->lock, NULL))
                 goto fail_lock;
 
         if (pthread_condattr_init(&cattr))
@@ -192,103 +199,108 @@ int tpm_init(size_t min,
 #ifndef __APPLE__
         pthread_condattr_setclock(&cattr, PTHREAD_COND_CLOCK);
 #endif
-        if (pthread_cond_init(&tpm.cond, &cattr))
+        if (pthread_cond_init(&tpm->cond, &cattr))
                 goto fail_cond;
 
-        list_head_init(&tpm.pool);
+        list_head_init(&tpm->pool);
 
         pthread_condattr_destroy(&cattr);
 
-        tpm.state = TPM_INIT;
-        tpm.func  = func;
-        tpm.min   = min;
-        tpm.inc   = inc;
-        tpm.cur   = 0;
-        tpm.wrk   = 0;
+        tpm->state = TPM_INIT;
+        tpm->func  = func;
+        tpm->o     = o;
+        tpm->min   = min;
+        tpm->inc   = inc;
+        tpm->cur   = 0;
+        tpm->wrk   = 0;
 
-        return 0;
+        return tpm;
 
  fail_cond:
         pthread_condattr_destroy(&cattr);
  fail_cattr:
-        pthread_mutex_destroy(&tpm.lock);
+        pthread_mutex_destroy(&tpm->lock);
  fail_lock:
-        return -1;
+        free(tpm);
+ fail_malloc:
+        return NULL;
 }
 
-int tpm_start(void)
+int tpm_start(struct tpm * tpm)
 {
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        if (pthread_create(&tpm.mgr, NULL, tpmgr, NULL)) {
-                pthread_mutex_unlock(&tpm.lock);
+        if (pthread_create(&tpm->mgr, NULL, tpmgr, tpm)) {
+                pthread_mutex_unlock(&tpm->lock);
                 return -1;
         }
 
-        tpm.state = TPM_RUNNING;
+        tpm->state = TPM_RUNNING;
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 
         return 0;
 }
 
-void tpm_stop(void)
+void tpm_stop(struct tpm * tpm)
 {
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        tpm.state = TPM_NULL;
+        tpm->state = TPM_NULL;
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 }
 
-void tpm_fini(void)
+void tpm_destroy(struct tpm * tpm)
 {
-        pthread_join(tpm.mgr, NULL);
+        pthread_join(tpm->mgr, NULL);
+
+        pthread_mutex_destroy(&tpm->lock);
+        pthread_cond_destroy(&tpm->cond);
 
-        pthread_mutex_destroy(&tpm.lock);
-        pthread_cond_destroy(&tpm.cond);
+        free(tpm);
 }
 
-bool tpm_check(void)
+bool tpm_check(struct tpm * tpm)
 {
         bool ret;
 
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        ret = tpm_pthr_el(pthread_self())->kill;
+        ret = tpm_pthr_el(tpm, pthread_self())->kill;
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 
         return ret;
 }
 
-void tpm_inc(void)
+void tpm_inc(struct tpm * tpm)
 {
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        --tpm.wrk;
+        --tpm->wrk;
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 }
 
-void tpm_dec(void)
+void tpm_dec(struct tpm * tpm)
 {
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        ++tpm.wrk;
+        ++tpm->wrk;
 
-        pthread_cond_signal(&tpm.cond);
+        pthread_cond_signal(&tpm->cond);
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 }
 
-void tpm_exit(void)
+void tpm_exit(struct tpm * tpm)
 {
-        pthread_mutex_lock(&tpm.lock);
+        pthread_mutex_lock(&tpm->lock);
 
-        tpm_pthr_el(pthread_self())->join = true;
+        tpm_pthr_el(tpm, pthread_self())->join = true;
 
-        pthread_cond_signal(&tpm.cond);
+        pthread_cond_signal(&tpm->cond);
 
-        pthread_mutex_unlock(&tpm.lock);
+        pthread_mutex_unlock(&tpm->lock);
 }