build: Move connmgr and enrolment to common ground

The connection manager and enrolment components of the unicast and
broadcast IPCP have a lot in common, as conjectured in the paper. The
initial implementation of the broadcast IPCP just duplicated the
code. This moves the shared functionality to common ground.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

5 files changed, 1070 insertions, 0 deletions

diff --git a/src/ipcpd/common/comp.h b/src/ipcpd/common/comp.h
new file mode 100644
index 00000000..95e59b24
--- /dev/null
+++ b/src/ipcpd/common/comp.h
@@ -0,0 +1,46 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2021
+ *
+ * Components for the unicast/broadcast IPC process
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_IPCPD_COMMON_COMP_H
+#define OUROBOROS_IPCPD_COMMON_COMP_H
+
+#include <ouroboros/cacep.h>
+
+#define DST_MAX_STRLEN 64
+
+enum comp_id {
+        COMPID_DT = 0,
+        COMPID_ENROLL,
+        COMPID_MGMT,
+        COMPID_MAX
+};
+
+struct conn {
+        struct conn_info conn_info;
+        struct {
+                char      dst[DST_MAX_STRLEN + 1];
+                int       fd;
+                qosspec_t qs;
+        } flow_info;
+};
+
+#endif /* OUROBOROS_IPCPD_COMMON_COMP_H */
diff --git a/src/ipcpd/common/connmgr.c b/src/ipcpd/common/connmgr.c
new file mode 100644
index 00000000..9002467c
--- /dev/null
+++ b/src/ipcpd/common/connmgr.c
@@ -0,0 +1,518 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2021
+ *
+ * Handles connections between components
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#define OUROBOROS_PREFIX "connection-manager"
+
+#include <ouroboros/dev.h>
+#include <ouroboros/cacep.h>
+#include <ouroboros/errno.h>
+#include <ouroboros/list.h>
+#include <ouroboros/logs.h>
+#include <ouroboros/notifier.h>
+
+#include "connmgr.h"
+#include "ipcp.h"
+
+#include <pthread.h>
+#include <string.h>
+#include <stdlib.h>
+#include <assert.h>
+
+enum connmgr_state {
+        CONNMGR_NULL = 0,
+        CONNMGR_INIT,
+        CONNMGR_RUNNING
+};
+
+struct conn_el {
+        struct list_head next;
+        struct conn      conn;
+};
+
+struct comp {
+        struct conn_info info;
+
+        struct list_head conns;
+        struct list_head pending;
+
+        pthread_cond_t   cond;
+        pthread_mutex_t  lock;
+};
+
+struct {
+        struct comp        comps[COMPID_MAX];
+        enum connmgr_state state;
+
+        pthread_t          acceptor;
+} connmgr;
+
+static int get_id_by_name(const char * name)
+{
+        enum comp_id i;
+
+        for (i = 0; i < COMPID_MAX; ++i)
+                if (strcmp(name, connmgr.comps[i].info.comp_name) == 0)
+                        return i;
+
+        return -1;
+}
+
+static int get_conn_by_fd(int           fd,
+                          enum comp_id  id,
+                          struct conn * conn)
+{
+        struct list_head * p;
+
+        pthread_mutex_lock(&connmgr.comps[id].lock);
+
+        list_for_each(p, &connmgr.comps[id].conns) {
+                struct conn_el * c =
+                        list_entry(p, struct conn_el, next);
+                if (c->conn.flow_info.fd == fd) {
+                        *conn = c->conn;
+                        pthread_mutex_unlock(&connmgr.comps[id].lock);
+                        return 0;
+                }
+        }
+
+        pthread_mutex_unlock(&connmgr.comps[id].lock);
+
+        return -1;
+}
+
+static int add_comp_conn(enum comp_id       id,
+                         int                fd,
+                         qosspec_t          qs,
+                         struct conn_info * rcv_info)
+{
+        struct conn_el * el;
+
+        el = malloc(sizeof(*el));
+        if (el == NULL) {
+                log_err("Not enough memory.");
+                return -1;
+        }
+
+        el->conn.conn_info    = *rcv_info;
+        el->conn.flow_info.fd = fd;
+        el->conn.flow_info.qs = qs;
+
+        pthread_mutex_lock(&connmgr.comps[id].lock);
+
+        list_add(&el->next, &connmgr.comps[id].pending);
+        pthread_cond_signal(&connmgr.comps[id].cond);
+
+        pthread_mutex_unlock(&connmgr.comps[id].lock);
+
+        return 0;
+}
+
+static void * flow_acceptor(void * o)
+{
+        int               fd;
+        qosspec_t         qs;
+        struct conn_info  rcv_info;
+        struct conn_info  fail_info;
+
+        (void) o;
+
+        memset(&fail_info, 0, sizeof(fail_info));
+
+        while (true) {
+                int id;
+
+                fd = flow_accept(&qs, NULL);
+                if (fd < 0) {
+                        if (fd != -EIRMD)
+                                log_warn("Flow accept failed: %d", fd);
+                        continue;
+                }
+
+                if (cacep_rcv(fd, &rcv_info)) {
+                        log_dbg("Error establishing application connection.");
+                        flow_dealloc(fd);
+                        continue;
+                }
+
+                id = get_id_by_name(rcv_info.comp_name);
+                if (id < 0) {
+                        log_dbg("Connection request for unknown component %s.",
+                                rcv_info.comp_name);
+                        cacep_snd(fd, &fail_info);
+                        flow_dealloc(fd);
+                        continue;
+                }
+
+                assert(id < COMPID_MAX);
+
+                if (cacep_snd(fd, &connmgr.comps[id].info)) {
+                        log_dbg("Failed to respond to request.");
+                        flow_dealloc(fd);
+                        continue;
+                }
+
+                if (add_comp_conn(id, fd, qs, &rcv_info)) {
+                        log_dbg("Failed to add new connection.");
+                        flow_dealloc(fd);
+                        continue;
+                }
+        }
+
+        return (void *) 0;
+}
+
+static void handle_event(void *       self,
+                         int          event,
+                         const void * o)
+{
+        struct conn conn;
+
+        (void) self;
+
+        if (!(event == NOTIFY_DT_FLOW_UP ||
+              event == NOTIFY_DT_FLOW_DOWN ||
+              event == NOTIFY_DT_FLOW_DEALLOC))
+                return;
+
+        if (get_conn_by_fd(*((int *) o), COMPID_DT, &conn))
+                return;
+
+        switch (event) {
+        case NOTIFY_DT_FLOW_UP:
+                notifier_event(NOTIFY_DT_CONN_UP, &conn);
+                break;
+        case NOTIFY_DT_FLOW_DOWN:
+                notifier_event(NOTIFY_DT_CONN_DOWN, &conn);
+                break;
+        case NOTIFY_DT_FLOW_DEALLOC:
+                notifier_event(NOTIFY_DT_CONN_DEL, &conn);
+                break;
+        default:
+                break;
+        }
+}
+
+int connmgr_init(void)
+{
+        connmgr.state = CONNMGR_INIT;
+
+        if (notifier_reg(handle_event, NULL))
+                return -1;
+
+        return 0;
+}
+
+void connmgr_fini(void)
+{
+        int i;
+
+        notifier_unreg(handle_event);
+
+        if (connmgr.state == CONNMGR_RUNNING)
+                pthread_join(connmgr.acceptor, NULL);
+
+        for (i = 0; i < COMPID_MAX; ++i)
+                connmgr_comp_fini(i);
+}
+
+int connmgr_start(void)
+{
+        if (pthread_create(&connmgr.acceptor, NULL, flow_acceptor, NULL))
+                return -1;
+
+        connmgr.state = CONNMGR_RUNNING;
+
+        return 0;
+}
+
+void connmgr_stop(void)
+{
+        if (connmgr.state == CONNMGR_RUNNING)
+                pthread_cancel(connmgr.acceptor);
+}
+
+int connmgr_comp_init(enum comp_id             id,
+                      const struct conn_info * info)
+{
+        struct comp * comp;
+
+        assert(id >= 0 && id < COMPID_MAX);
+
+        comp = connmgr.comps + id;
+
+        if (pthread_mutex_init(&comp->lock, NULL))
+                return -1;
+
+        if (pthread_cond_init(&comp->cond, NULL)) {
+                pthread_mutex_destroy(&comp->lock);
+                return -1;
+        }
+
+        list_head_init(&comp->conns);
+        list_head_init(&comp->pending);
+
+        memcpy(&connmgr.comps[id].info, info, sizeof(connmgr.comps[id].info));
+
+        return 0;
+}
+
+void connmgr_comp_fini(enum comp_id id)
+{
+        struct list_head * p;
+        struct list_head * h;
+        struct comp *      comp;
+
+        assert(id >= 0 && id < COMPID_MAX);
+
+        if (strlen(connmgr.comps[id].info.comp_name) == 0)
+                return;
+
+        comp = connmgr.comps + id;
+
+        pthread_mutex_lock(&comp->lock);
+
+        list_for_each_safe(p, h, &comp->conns) {
+                struct conn_el * e = list_entry(p, struct conn_el, next);
+                list_del(&e->next);
+                free(e);
+        }
+
+        list_for_each_safe(p, h, &comp->pending) {
+                struct conn_el * e = list_entry(p, struct conn_el, next);
+                list_del(&e->next);
+                free(e);
+        }
+
+        pthread_mutex_unlock(&comp->lock);
+
+        pthread_cond_destroy(&comp->cond);
+        pthread_mutex_destroy(&comp->lock);
+
+        memset(&connmgr.comps[id].info, 0, sizeof(connmgr.comps[id].info));
+}
+
+int connmgr_ipcp_connect(const char * dst,
+                         const char * component,
+                         qosspec_t    qs)
+{
+        struct conn_el * ce;
+        int              id;
+
+        assert(dst);
+        assert(component);
+
+        ce = malloc(sizeof(*ce));
+        if (ce == NULL) {
+                log_dbg("Out of memory.");
+                return -1;
+        }
+
+        id = get_id_by_name(component);
+        if (id < 0) {
+                log_dbg("No such component: %s", component);
+                free(ce);
+                return -1;
+        }
+
+        if (connmgr_alloc(id, dst, &qs, &ce->conn)) {
+                free(ce);
+                return -1;
+        }
+
+        if (strlen(dst) > DST_MAX_STRLEN) {
+                log_warn("Truncating dst length for connection.");
+                memcpy(ce->conn.flow_info.dst, dst, DST_MAX_STRLEN);
+                ce->conn.flow_info.dst[DST_MAX_STRLEN] = '\0';
+        } else {
+                strcpy(ce->conn.flow_info.dst, dst);
+        }
+
+        pthread_mutex_lock(&connmgr.comps[id].lock);
+
+        list_add(&ce->next, &connmgr.comps[id].conns);
+
+        pthread_mutex_unlock(&connmgr.comps[id].lock);
+
+        return 0;
+}
+
+int connmgr_ipcp_disconnect(const char * dst,
+                            const char * component)
+{
+        struct list_head * p;
+        struct list_head * h;
+        int                id;
+
+        assert(dst);
+        assert(component);
+
+        id = get_id_by_name(component);
+        if (id < 0)
+                return -1;
+
+        pthread_mutex_lock(&connmgr.comps[id].lock);
+
+        list_for_each_safe(p,h, &connmgr.comps[id].conns) {
+                struct conn_el * el = list_entry(p, struct conn_el, next);
+                if (strcmp(el->conn.flow_info.dst, dst) == 0) {
+                        int ret;
+                        pthread_mutex_unlock(&connmgr.comps[id].lock);
+                        list_del(&el->next);
+                        ret = connmgr_dealloc(id, &el->conn);
+                        free(el);
+                        return ret;
+                }
+        }
+
+        pthread_mutex_unlock(&connmgr.comps[id].lock);
+
+        return 0;
+}
+
+int connmgr_alloc(enum comp_id  id,
+                  const char *  dst,
+                  qosspec_t *   qs,
+                  struct conn * conn)
+{
+        assert(id >= 0 && id < COMPID_MAX);
+        assert(dst);
+
+        conn->flow_info.fd = flow_alloc(dst, qs, NULL);
+        if (conn->flow_info.fd < 0) {
+                log_dbg("Failed to allocate flow to %s.", dst);
+                return -1;
+        }
+
+        if (qs != NULL)
+                conn->flow_info.qs = *qs;
+        else
+                memset(&conn->flow_info.qs, 0, sizeof(conn->flow_info.qs));
+
+        log_dbg("Sending cacep info for protocol %s to fd %d.",
+                connmgr.comps[id].info.protocol, conn->flow_info.fd);
+
+        if (cacep_snd(conn->flow_info.fd, &connmgr.comps[id].info)) {
+                log_dbg("Failed to create application connection.");
+                flow_dealloc(conn->flow_info.fd);
+                return -1;
+        }
+
+        if (cacep_rcv(conn->flow_info.fd, &conn->conn_info)) {
+                log_dbg("Failed to connect to application.");
+                flow_dealloc(conn->flow_info.fd);
+                return -1;
+        }
+
+        if (strcmp(connmgr.comps[id].info.protocol, conn->conn_info.protocol)) {
+                log_dbg("Unknown protocol (requested %s, got %s).",
+                        connmgr.comps[id].info.protocol,
+                        conn->conn_info.protocol);
+                flow_dealloc(conn->flow_info.fd);
+                return -1;
+        }
+
+        if (connmgr.comps[id].info.pref_version !=
+            conn->conn_info.pref_version) {
+                log_dbg("Unknown protocol version.");
+                flow_dealloc(conn->flow_info.fd);
+                return -1;
+        }
+
+        if (connmgr.comps[id].info.pref_syntax != conn->conn_info.pref_syntax) {
+                log_dbg("Unknown protocol syntax.");
+                flow_dealloc(conn->flow_info.fd);
+                return -1;
+        }
+
+        switch (id) {
+        case COMPID_DT:
+                notifier_event(NOTIFY_DT_CONN_ADD, conn);
+#if defined(BUILD_IPCP_UNICAST) && defined(IPCP_CONN_WAIT_DIR)
+                dir_wait_running();
+#endif
+                break;
+        case COMPID_MGMT:
+                notifier_event(NOTIFY_MGMT_CONN_ADD, conn);
+                break;
+        default:
+                break;
+        }
+
+        return 0;
+}
+
+int connmgr_dealloc(enum comp_id  id,
+                    struct conn * conn)
+{
+        switch (id) {
+        case COMPID_DT:
+                notifier_event(NOTIFY_DT_CONN_DEL, conn);
+                break;
+#if defined(BUILD_IPCP_UNICAST) && defined(IPCP_CONN_WAIT_DIR)
+        case COMPID_MGMT:
+                notifier_event(NOTIFY_MGMT_CONN_DEL, conn);
+                break;
+#endif
+        default:
+                break;
+        }
+
+        return flow_dealloc(conn->flow_info.fd);
+}
+
+
+int connmgr_wait(enum comp_id  id,
+                 struct conn * conn)
+{
+        struct conn_el * el;
+        struct comp *    comp;
+
+        assert(id >= 0 && id < COMPID_MAX);
+        assert(conn);
+
+        comp = connmgr.comps + id;
+
+        pthread_mutex_lock(&comp->lock);
+
+        pthread_cleanup_push((void(*)(void *))pthread_mutex_unlock,
+                             (void *) &comp->lock);
+
+        while (list_is_empty(&comp->pending))
+                pthread_cond_wait(&comp->cond, &comp->lock);
+
+        pthread_cleanup_pop(false);
+
+        el = list_first_entry((&comp->pending), struct conn_el, next);
+        if (el == NULL) {
+                pthread_mutex_unlock(&comp->lock);
+                return -1;
+        }
+
+        *conn = el->conn;
+
+        list_del(&el->next);
+        list_add(&el->next, &connmgr.comps[id].conns);
+
+        pthread_mutex_unlock(&comp->lock);
+
+        return 0;
+}
diff --git a/src/ipcpd/common/connmgr.h b/src/ipcpd/common/connmgr.h
new file mode 100644
index 00000000..5f7b557f
--- /dev/null
+++ b/src/ipcpd/common/connmgr.h
@@ -0,0 +1,74 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2021
+ *
+ * Handles the different AP connections
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_IPCPD_COMMON_CONNMGR_H
+#define OUROBOROS_IPCPD_COMMON_CONNMGR_H
+
+#include <ouroboros/cacep.h>
+#include <ouroboros/qos.h>
+
+#include "comp.h"
+
+#define NOTIFY_DT_CONN_ADD     0x00D0
+#define NOTIFY_DT_CONN_DEL     0x00D1
+#define NOTIFY_DT_CONN_QOS     0x00D2
+#define NOTIFY_DT_CONN_UP      0x00D3
+#define NOTIFY_DT_CONN_DOWN    0x00D4
+#define NOTIFY_DT_FLOW_UP      0x00D5
+#define NOTIFY_DT_FLOW_DOWN    0x00D6
+#define NOTIFY_DT_FLOW_DEALLOC 0x00D7
+
+#define NOTIFY_MGMT_CONN_ADD   0x00F0
+#define NOTIFY_MGMT_CONN_DEL   0x00F1
+
+int         connmgr_init(void);
+
+void        connmgr_fini(void);
+
+int         connmgr_start(void);
+
+void        connmgr_stop(void);
+
+int         connmgr_comp_init(enum comp_id             id,
+                              const struct conn_info * info);
+
+void        connmgr_comp_fini(enum comp_id id);
+
+int         connmgr_ipcp_connect(const char * dst,
+                                 const char * component,
+                                 qosspec_t    qs);
+
+int         connmgr_ipcp_disconnect(const char * dst,
+                                    const char * component);
+
+int         connmgr_alloc(enum comp_id  id,
+                          const char *  dst,
+                          qosspec_t *   qs,
+                          struct conn * conn);
+
+int         connmgr_dealloc(enum comp_id  id,
+                            struct conn * conn);
+
+int         connmgr_wait(enum comp_id  id,
+                         struct conn * conn);
+
+#endif /* OUROBOROS_IPCPD_COMMON_CONNMGR_H */
diff --git a/src/ipcpd/common/enroll.c b/src/ipcpd/common/enroll.c
new file mode 100644
index 00000000..090067d8
--- /dev/null
+++ b/src/ipcpd/common/enroll.c
@@ -0,0 +1,385 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2021
+ *
+ * Enrollment Task
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#if defined(__linux__) || defined(__CYGWIN__)
+#define _DEFAULT_SOURCE
+#else
+#define _POSIX_C_SOURCE 199309L
+#endif
+
+#define OUROBOROS_PREFIX "enrollment"
+
+#include <ouroboros/endian.h>
+#include <ouroboros/errno.h>
+#include <ouroboros/time_utils.h>
+#include <ouroboros/dev.h>
+#include <ouroboros/logs.h>
+#include <ouroboros/errno.h>
+#include <ouroboros/sockets.h>
+
+#include "common/connmgr.h"
+#include "common/enroll.h"
+#include "ipcp.h"
+
+#include <assert.h>
+#include <stdlib.h>
+#include <string.h>
+#include <pthread.h>
+
+#include "ipcp_config.pb-c.h"
+typedef EnrollMsg enroll_msg_t;
+
+#define ENROLL_COMP             "Enrollment"
+#define ENROLL_PROTO            "OEP" /* Ouroboros enrollment protocol */
+#define ENROLL_WARN_TIME_OFFSET 20
+#define ENROLL_BUF_LEN          1024
+
+enum enroll_state {
+        ENROLL_NULL = 0,
+        ENROLL_INIT,
+        ENROLL_RUNNING
+};
+
+struct {
+        struct ipcp_config conf;
+        enum enroll_state  state;
+        pthread_t          listener;
+} enroll;
+
+static int send_rcv_enroll_msg(int fd)
+{
+        enroll_msg_t    req = ENROLL_MSG__INIT;
+        enroll_msg_t *  reply;
+        uint8_t         buf[ENROLL_BUF_LEN];
+        ssize_t         len;
+        ssize_t         delta_t;
+        struct timespec t0;
+        struct timespec rtt;
+
+        req.code = ENROLL_CODE__ENROLL_REQ;
+
+        len = enroll_msg__get_packed_size(&req);
+        if (len < 0) {
+                log_dbg("Failed pack request message.");
+                return -1;
+        }
+
+        enroll_msg__pack(&req, buf);
+
+        clock_gettime(CLOCK_REALTIME, &t0);
+
+        if (flow_write(fd, buf, len) < 0) {
+                log_dbg("Failed to send request message.");
+                return -1;
+        }
+
+        len = flow_read(fd, buf, ENROLL_BUF_LEN);
+        if (len < 0) {
+                log_dbg("No enrollment reply received.");
+                return -1;
+        }
+
+        log_dbg("Received enrollment info (%zd bytes).", len);
+
+        reply = enroll_msg__unpack(NULL, len, buf);
+        if (reply == NULL) {
+                log_dbg("No enrollment response.");
+                return -1;
+        }
+
+        if (reply->code != ENROLL_CODE__ENROLL_BOOT) {
+                log_dbg("Failed to unpack enrollment response.");
+                enroll_msg__free_unpacked(reply, NULL);
+                return -1;
+        }
+
+        if (!(reply->has_t_sec && reply->has_t_nsec)) {
+                log_dbg("No time in response message.");
+                enroll_msg__free_unpacked(reply, NULL);
+                return -1;
+        }
+
+        clock_gettime(CLOCK_REALTIME, &rtt);
+
+        delta_t = ts_diff_ms(&t0, &rtt);
+
+        rtt.tv_sec  = reply->t_sec;
+        rtt.tv_nsec = reply->t_nsec;
+
+        if (labs(ts_diff_ms(&t0, &rtt)) - delta_t > ENROLL_WARN_TIME_OFFSET)
+                log_warn("Clock offset above threshold.");
+
+        strcpy(enroll.conf.layer_info.layer_name,
+               reply->conf->layer_info->layer_name);
+        enroll.conf.type           = reply->conf->ipcp_type;
+#ifdef BUILD_IPCP_UNICAST
+        enroll.conf.addr_size      = reply->conf->addr_size;
+        enroll.conf.eid_size       = reply->conf->eid_size;
+        enroll.conf.max_ttl        = reply->conf->max_ttl;
+        enroll.conf.addr_auth_type = reply->conf->addr_auth_type;
+        enroll.conf.routing_type   = reply->conf->routing_type;
+        enroll.conf.cong_avoid     = reply->conf->cong_avoid;
+#endif
+        enroll.conf.layer_info.dir_hash_algo
+                = reply->conf->layer_info->dir_hash_algo;
+        enroll_msg__free_unpacked(reply, NULL);
+
+        return 0;
+}
+
+static ssize_t enroll_pack(uint8_t ** buf)
+{
+        enroll_msg_t      msg        = ENROLL_MSG__INIT;
+        ipcp_config_msg_t config     = IPCP_CONFIG_MSG__INIT;
+        layer_info_msg_t  layer_info = LAYER_INFO_MSG__INIT;
+        struct timespec   now;
+        ssize_t           len;
+
+        clock_gettime(CLOCK_REALTIME, &now);
+
+        msg.code       = ENROLL_CODE__ENROLL_BOOT;
+        msg.has_t_sec  = true;
+        msg.t_sec      = now.tv_sec;
+        msg.has_t_nsec = true;
+        msg.t_nsec     = now.tv_nsec;
+        msg.conf       = &config;
+
+        config.ipcp_type          = enroll.conf.type;
+#ifdef BUILD_IPCP_UNICAST
+        config.has_addr_size      = true;
+        config.addr_size          = enroll.conf.addr_size;
+        config.has_eid_size       = true;
+        config.eid_size           = enroll.conf.eid_size;
+        config.has_max_ttl        = true;
+        config.max_ttl            = enroll.conf.max_ttl;
+        config.has_addr_auth_type = true;
+        config.addr_auth_type     = enroll.conf.addr_auth_type;
+        config.has_routing_type   = true;
+        config.routing_type       = enroll.conf.routing_type;
+        config.has_cong_avoid     = true;
+        config.cong_avoid         = enroll.conf.cong_avoid;
+#endif
+        config.layer_info         = &layer_info;
+
+        layer_info.layer_name     = (char *) enroll.conf.layer_info.layer_name;
+        layer_info.dir_hash_algo  = enroll.conf.layer_info.dir_hash_algo;
+
+        len = enroll_msg__get_packed_size(&msg);
+
+        *buf = malloc(len);
+        if (*buf == NULL)
+                return -1;
+
+        enroll_msg__pack(&msg, *buf);
+
+        return len;
+}
+
+static void * enroll_handle(void * o)
+{
+        struct conn    conn;
+        uint8_t        buf[ENROLL_BUF_LEN];
+        uint8_t *      reply;
+        ssize_t        len;
+        enroll_msg_t * msg;
+
+        (void) o;
+
+        while (true) {
+                if (connmgr_wait(COMPID_ENROLL, &conn)) {
+                        log_err("Failed to get next connection.");
+                        continue;
+                }
+
+                len = flow_read(conn.flow_info.fd, buf, ENROLL_BUF_LEN);
+                if (len < 0) {
+                        log_err("Failed to read from flow.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                msg = enroll_msg__unpack(NULL, len, buf);
+                if (msg == NULL) {
+                        log_err("Failed to unpack message.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                if (msg->code != ENROLL_CODE__ENROLL_REQ) {
+                        log_err("Wrong message type.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        enroll_msg__free_unpacked(msg, NULL);
+                        continue;
+                }
+
+                log_dbg("Enrolling a new neighbor.");
+
+                enroll_msg__free_unpacked(msg, NULL);
+
+                len = enroll_pack(&reply);
+                if (reply == NULL) {
+                        log_err("Failed to pack enrollment message.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                log_dbg("Sending enrollment info (%zd bytes).", len);
+
+                if (flow_write(conn.flow_info.fd, reply, len) < 0) {
+                        log_err("Failed respond to enrollment request.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        free(reply);
+                        continue;
+                }
+
+                free(reply);
+
+                len = flow_read(conn.flow_info.fd, buf, ENROLL_BUF_LEN);
+                if (len < 0) {
+                        log_err("Failed to read from flow.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                msg = enroll_msg__unpack(NULL, len, buf);
+                if (msg == NULL) {
+                        log_err("Failed to unpack message.");
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                if (msg->code != ENROLL_CODE__ENROLL_DONE || !msg->has_result) {
+                        log_err("Wrong message type.");
+                        enroll_msg__free_unpacked(msg, NULL);
+                        connmgr_dealloc(COMPID_ENROLL, &conn);
+                        continue;
+                }
+
+                if (msg->result == 0)
+                        log_dbg("Neighbor enrollment successful.");
+                else
+                        log_dbg("Neigbor reported failed enrollment.");
+
+                enroll_msg__free_unpacked(msg, NULL);
+
+                connmgr_dealloc(COMPID_ENROLL, &conn);
+        }
+
+        return 0;
+}
+
+int enroll_boot(struct conn * conn)
+{
+        log_dbg("Getting boot information.");
+
+        if (send_rcv_enroll_msg(conn->flow_info.fd)) {
+                log_err("Failed to enroll.");
+                return -1;
+        }
+
+        return 0;
+}
+
+int enroll_done(struct conn * conn,
+                int           result)
+{
+        enroll_msg_t msg = ENROLL_MSG__INIT;
+        uint8_t      buf[ENROLL_BUF_LEN];
+        ssize_t       len;
+
+        msg.code       = ENROLL_CODE__ENROLL_DONE;
+        msg.has_result = true;
+        msg.result     = result;
+
+        len = enroll_msg__get_packed_size(&msg);
+        if (len < 0) {
+                log_dbg("Failed pack request message.");
+                return -1;
+        }
+
+        enroll_msg__pack(&msg, buf);
+
+        if (flow_write(conn->flow_info.fd, buf, len) < 0) {
+                log_dbg("Failed to send acknowledgment.");
+                return -1;
+        }
+
+        return 0;
+}
+
+void enroll_bootstrap(const struct ipcp_config * conf)
+{
+        assert(conf);
+
+        memcpy(&enroll.conf, conf, sizeof(enroll.conf));
+}
+
+struct ipcp_config * enroll_get_conf(void)
+{
+        return &enroll.conf;
+}
+
+int enroll_init(void)
+{
+        struct conn_info info;
+
+        memset(&info, 0, sizeof(info));
+
+        strcpy(info.comp_name, ENROLL_COMP);
+        strcpy(info.protocol, ENROLL_PROTO);
+        info.pref_version = 1;
+        info.pref_syntax  = PROTO_GPB;
+        info.addr         = 0;
+
+        if (connmgr_comp_init(COMPID_ENROLL, &info)) {
+                log_err("Failed to register with connmgr.");
+                return -1;
+        }
+
+        enroll.state = ENROLL_INIT;
+
+        return 0;
+}
+
+void enroll_fini(void)
+{
+        if (enroll.state == ENROLL_RUNNING)
+                pthread_join(enroll.listener, NULL);
+
+        connmgr_comp_fini(COMPID_ENROLL);
+}
+
+int enroll_start(void)
+{
+        if (pthread_create(&enroll.listener, NULL, enroll_handle, NULL))
+                return -1;
+
+        enroll.state = ENROLL_RUNNING;
+
+        return 0;
+}
+
+void enroll_stop(void)
+{
+        if (enroll.state == ENROLL_RUNNING)
+                pthread_cancel(enroll.listener);
+}
diff --git a/src/ipcpd/common/enroll.h b/src/ipcpd/common/enroll.h
new file mode 100644
index 00000000..fb866416
--- /dev/null
+++ b/src/ipcpd/common/enroll.h
@@ -0,0 +1,47 @@
+/*
+ * Ouroboros - Copyright (C) 2016 - 2021
+ *
+ * Enrollment Task
+ *
+ *    Dimitri Staessens <dimitri@ouroboros.rocks>
+ *    Sander Vrijders   <sander@ouroboros.rocks>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., http://www.fsf.org/about/contact/.
+ */
+
+#ifndef OUROBOROS_IPCPD_COMMON_ENROLL_H
+#define OUROBOROS_IPCPD_COMMON_ENROLL_H
+
+#include <ouroboros/ipcp.h>
+
+#include "comp.h"
+
+int                  enroll_init(void);
+
+void                 enroll_fini(void);
+
+int                  enroll_start(void);
+
+void                 enroll_stop(void);
+
+void                 enroll_bootstrap(const struct ipcp_config * conf);
+
+int                  enroll_boot(struct conn * conn);
+
+int                  enroll_done(struct conn * conn,
+                                 int           result);
+
+struct ipcp_config * enroll_get_conf(void);
+
+#endif /* OUROBOROS_IPCPD_COMMON_ENROLL_H */