ipcpd: Revise UDP IPCP

The UDP IPCP now uses a fixed server UDP port (default 3435) for all
communications. This allows passing firewalls more easily since only a
single port needs to be opened. The client port can be fixed as well
if needed (default random). It uses an internal eid, so the MTU of the
UDP layer is reduced by 4 bytes, similar to the Ethernet IPCPs.

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

9 files changed, 435 insertions, 446 deletions

diff --git a/doc/man/ouroboros.8 b/doc/man/ouroboros.8
index 9c622639..618418c2 100644
--- a/doc/man/ouroboros.8
+++ b/doc/man/ouroboros.8
@@ -209,6 +209,18 @@ ip \fIip\fR specifies the local IP address to bind to
 .PP
 [dns \fdns\fR] specifies an optional DDNS server that will be used for
 the directory.
+.PP
+[cport \fcport\fR] specifies a client UDP port that will be used for
+sending packets.
+.br
+default: A random UDP port in the ephemeral range
+.PP
+[sport \fsport\fR] specifies a server UDP port that is used for
+receiving ouroboros traffic. This must be the same for the entire UDP
+layer. Parallel UDP layers should use different ports. This UDP port
+needs to be forwarded if the server is behind a NAT.
+.br
+default: 3435
 .RE
 
 .PP
diff --git a/include/ouroboros/ipcp.h b/include/ouroboros/ipcp.h
index b2c0fca0..11e2699b 100644
--- a/include/ouroboros/ipcp.h
+++ b/include/ouroboros/ipcp.h
@@ -90,6 +90,8 @@ struct ipcp_config {
         /* UDP */
         uint32_t           ip_addr;
         uint32_t           dns_addr;
+        uint16_t           clt_port;
+        uint16_t           srv_port;
 
         /* Ethernet */
         char *             dev;
diff --git a/src/ipcpd/config.h.in b/src/ipcpd/config.h.in
index ddd0d56e..8545021b 100644
--- a/src/ipcpd/config.h.in
+++ b/src/ipcpd/config.h.in
@@ -39,7 +39,7 @@
 #define IPCP_ADD_THREADS    @IPCP_ADD_THREADS@
 #cmakedefine HAVE_LIBGCRYPT
 
-/* normal IPCP */
+/* unicast IPCP */
 #define QOS_PRIO_BE         @IPCP_QOS_CUBE_BE_PRIO@
 #define QOS_PRIO_VIDEO      @IPCP_QOS_CUBE_VIDEO_PRIO@
 #define QOS_PRIO_VOICE      @IPCP_QOS_CUBE_VOICE_PRIO@
@@ -55,11 +55,13 @@
 #cmakedefine HAVE_DDNS
 #define NSUPDATE_EXEC       "@NSUPDATE_EXECUTABLE@"
 #define NSLOOKUP_EXEC       "@NSLOOKUP_EXECUTABLE@"
+#define IPCP_UDP_RD_THR     @IPCP_UDP_RD_THR@
+#define IPCP_UDP_WR_THR     @IPCP_UDP_WR_THR@
 
 /* eth-llc */
 #cmakedefine HAVE_NETMAP
 #cmakedefine HAVE_BPF
 #cmakedefine HAVE_RAW_SOCKETS
-#define IPCP_ETH_RD_THR  @IPCP_ETH_RD_THR@
-#define IPCP_ETH_WR_THR  @IPCP_ETH_WR_THR@
 #cmakedefine IPCP_ETH_QDISC_BYPASS
+#define IPCP_ETH_RD_THR     @IPCP_ETH_RD_THR@
+#define IPCP_ETH_WR_THR     @IPCP_ETH_WR_THR@
diff --git a/src/ipcpd/ipcp.c b/src/ipcpd/ipcp.c
index 8e0cd189..bd0aeee5 100644
--- a/src/ipcpd/ipcp.c
+++ b/src/ipcpd/ipcp.c
@@ -231,37 +231,39 @@ static void * mainloop(void * o)
                         conf.type = conf_msg->ipcp_type;
                         strcpy(conf.layer_info.layer_name,
                                conf_msg->layer_info->layer_name);
-                        if (conf_msg->ipcp_type == IPCP_NORMAL) {
+
+                        switch(conf_msg->ipcp_type) {
+                        case IPCP_NORMAL:
                                 conf.addr_size      = conf_msg->addr_size;
                                 conf.eid_size       = conf_msg->eid_size;
                                 conf.max_ttl        = conf_msg->max_ttl;
                                 conf.addr_auth_type = conf_msg->addr_auth_type;
                                 conf.routing_type   = conf_msg->routing_type;
                                 conf.pff_type       = conf_msg->pff_type;
-                        }
-
-                        if (conf_msg->ipcp_type == IPCP_ETH_LLC)
-                                conf.dev = conf_msg->dev;
-
-                        if (conf_msg->ipcp_type == IPCP_ETH_DIX) {
-                                conf.dev = conf_msg->dev;
+                                break;
+                        case IPCP_ETH_DIX:
                                 conf.ethertype = conf_msg->ethertype;
-                        }
-
-                        if (conf_msg->ipcp_type == IPCP_UDP) {
+                                /* FALLTHRU */
+                        case IPCP_ETH_LLC:
+                                conf.dev = conf_msg->dev;
+                                break;
+                        case IPCP_UDP:
                                 conf.ip_addr  = conf_msg->ip_addr;
                                 conf.dns_addr = conf_msg->dns_addr;
-
+                                conf.clt_port = conf_msg->clt_port;
+                                conf.srv_port = conf_msg->srv_port;
                                 conf.layer_info.dir_hash_algo = HASH_MD5;
                                 layer_info.dir_hash_algo      = HASH_MD5;
-                        }
-
-                        if (conf_msg->ipcp_type == IPCP_BROADCAST) {
+                                break;
+                        case IPCP_BROADCAST:
                                 conf.layer_info.dir_hash_algo = HASH_SHA3_256;
                                 layer_info.dir_hash_algo      = HASH_SHA3_256;
+                                break;
+                        default:
+                                log_err("Unknown IPCP type.");
                         }
 
-                        /* UDP and broadcast have a fixed hash algorithm. */
+                        /* UDP and broadcast use fixed hash algorithm. */
                         if (conf_msg->ipcp_type != IPCP_UDP &&
                             conf_msg->ipcp_type != IPCP_BROADCAST) {
                                 switch(conf_msg->layer_info->dir_hash_algo) {
diff --git a/src/ipcpd/udp/CMakeLists.txt b/src/ipcpd/udp/CMakeLists.txt
index b21afe75..f1a29ef6 100644
--- a/src/ipcpd/udp/CMakeLists.txt
+++ b/src/ipcpd/udp/CMakeLists.txt
@@ -16,9 +16,11 @@ set(IPCP_UDP_TARGET ipcpd-udp CACHE INTERNAL "")
 
 set(UDP_SOURCES
   # Add source files here
-  ${CMAKE_CURRENT_SOURCE_DIR}/main.c)
+  ${CMAKE_CURRENT_SOURCE_DIR}/main.c
+  )
 
 add_executable(ipcpd-udp ${UDP_SOURCES} ${IPCP_SOURCES})
+
 target_link_libraries(ipcpd-udp LINK_PUBLIC ouroboros-dev)
 
 # Find the nsupdate executable
@@ -52,6 +54,11 @@ else ()
   endif ()
 endif ()
 
+set(IPCP_UDP_RD_THR 3 CACHE STRING
+  "Number of reader threads in UDP IPCP")
+set(IPCP_UDP_WR_THR 3 CACHE STRING
+  "Number of writer threads in UDP IPCP")
+
 include(AddCompileFlags)
 if (CMAKE_BUILD_TYPE MATCHES "Debug*")
   add_compile_flags(ipcpd-udp -DCONFIG_OUROBOROS_DEBUG)
diff --git a/src/ipcpd/udp/main.c b/src/ipcpd/udp/main.c
index f45a18cb..559be55a 100644
--- a/src/ipcpd/udp/main.c
+++ b/src/ipcpd/udp/main.c
@@ -30,6 +30,7 @@
 
 #define OUROBOROS_PREFIX "ipcpd/udp"
 
+#include <ouroboros/bitmap.h>
 #include <ouroboros/hash.h>
 #include <ouroboros/list.h>
 #include <ouroboros/utils.h>
@@ -58,34 +59,50 @@
 #define FLOW_REPLY               2
 
 #define THIS_TYPE                IPCP_UDP
-#define LISTEN_PORT              htons(0x0D1F)
-#define SHIM_UDP_BUF_SIZE        256
-#define SHIM_UDP_MSG_SIZE        256
-#define SHIM_UDP_MAX_PACKET_SIZE 8980
+#define IPCP_UDP_MAX_PACKET_SIZE 8980
+#define OUR_HEADER_LEN           sizeof(uint32_t) /* adds eid */
+
+#define IPCP_UDP_BUF_SIZE        256
+#define IPCP_UDP_MSG_SIZE        256
 #define DNS_TTL                  86400
 #define FD_UPDATE_TIMEOUT        100 /* microseconds */
 
-#define local_ip                 (udp_data.s_saddr.sin_addr.s_addr)
+#define SERV_PORT                udp_data.s_saddr.sin_port;
+#define SERV_SADDR               ((struct sockaddr *) &udp_data.s_saddr)
+#define CLNT_SADDR               ((struct sockaddr *) &udp_data.c_saddr)
+#define SERV_SADDR_SIZE          (sizeof(udp_data.s_saddr))
+#define LOCAL_IP                 (udp_data.s_saddr.sin_addr.s_addr)
 
-#define UDP_MAX_PORTS            0xFFFF
+#define MGMT_EID                 0
+#define MGMT_FRAME_SIZE          512
 
+/* Keep order for alignment. */
 struct mgmt_msg {
-        uint16_t src_udp_port;
-        uint16_t dst_udp_port;
+        uint32_t eid;
+        uint32_t s_eid;
+        uint32_t d_eid;
         uint8_t  code;
-        uint8_t  response;
-        /* QoS parameters from spec, aligned */
+        int8_t   response;
+        /* QoS parameters from spec */
         uint8_t  availability;
         uint8_t  in_order;
-        uint32_t delay;
         uint64_t bandwidth;
+        uint32_t delay;
         uint32_t loss;
         uint32_t ber;
         uint32_t max_gap;
 } __attribute__((packed));
 
+struct mgmt_frame {
+        struct list_head   next;
+        struct sockaddr_in r_saddr;
+        uint8_t            buf[MGMT_FRAME_SIZE];
+};
+
+/* UDP flow */
 struct uf {
-        int udp;
+        int d_eid;
+        /* IP details are stored through connect(). */
         int skfd;
 };
 
@@ -94,25 +111,25 @@ struct {
 
         uint32_t           ip_addr;
         uint32_t           dns_addr;
-        /* listen server */
+        /* server socket */
         struct sockaddr_in s_saddr;
         int                s_fd;
+        /* client port */
+        int                clt_port;
 
         fset_t *           np1_flows;
         fqueue_t *         fq;
-        fd_set             flow_fd_s;
-        /* bidir mappings of (n - 1) file descriptor to (n) flow descriptor */
-        int                uf_to_fd[FD_SETSIZE];
         struct uf          fd_to_uf[SYS_MAX_FLOWS];
         pthread_rwlock_t   flows_lock;
 
-        pthread_t          packet_loop;
-        pthread_t          handler;
-        pthread_t          packet_reader;
+        pthread_t          packet_writer[IPCP_UDP_WR_THR];
+        pthread_t          packet_reader[IPCP_UDP_RD_THR];
 
-        bool               fd_set_mod;
-        pthread_cond_t     fd_set_cond;
-        pthread_mutex_t    fd_set_lock;
+        /* Handle mgmt frames in a different thread */
+        pthread_t          mgmt_handler;
+        pthread_mutex_t    mgmt_lock;
+        pthread_cond_t     mgmt_cond;
+        struct list_head   mgmt_frames;
 } udp_data;
 
 static int udp_data_init(void)
@@ -120,24 +137,19 @@ static int udp_data_init(void)
         int i;
 
         if (pthread_rwlock_init(&udp_data.flows_lock, NULL))
-                return -1;
-
-        if (pthread_cond_init(&udp_data.fd_set_cond, NULL))
-                goto fail_set_cond;
+                goto fail_rwlock_init;
 
-        if (pthread_mutex_init(&udp_data.fd_set_lock, NULL))
-                goto fail_set_lock;
+        if (pthread_cond_init(&udp_data.mgmt_cond, NULL))
+                goto fail_mgmt_cond;
 
-        for (i = 0; i < FD_SETSIZE; ++i)
-                udp_data.uf_to_fd[i] = -1;
+        if (pthread_mutex_init(&udp_data.mgmt_lock, NULL))
+                goto fail_mgmt_lock;
 
         for (i = 0; i < SYS_MAX_FLOWS; ++i) {
-                udp_data.fd_to_uf[i].skfd = -1;
-                udp_data.fd_to_uf[i].udp = -1;
+                udp_data.fd_to_uf[i].skfd  = -1;
+                udp_data.fd_to_uf[i].d_eid = -1;
         }
 
-        FD_ZERO(&udp_data.flow_fd_s);
-
         udp_data.np1_flows = fset_create();
         if (udp_data.np1_flows == NULL)
                 goto fail_fset;
@@ -150,88 +162,43 @@ static int udp_data_init(void)
         if (udp_data.shim_data == NULL)
                 goto fail_data;
 
+        list_head_init(&udp_data.mgmt_frames);
+
         return 0;
  fail_data:
         fqueue_destroy(udp_data.fq);
  fail_fqueue:
         fset_destroy(udp_data.np1_flows);
  fail_fset:
-        pthread_mutex_destroy(&udp_data.fd_set_lock);
- fail_set_lock:
-        pthread_cond_destroy(&udp_data.fd_set_cond);
- fail_set_cond:
+        pthread_mutex_destroy(&udp_data.mgmt_lock);
+ fail_mgmt_lock:
+        pthread_cond_destroy(&udp_data.mgmt_cond);
+ fail_mgmt_cond:
         pthread_rwlock_destroy(&udp_data.flows_lock);
+ fail_rwlock_init:
         return -1;
 }
 
 static void udp_data_fini(void)
 {
-        fset_destroy(udp_data.np1_flows);
-        fqueue_destroy(udp_data.fq);
-
         shim_data_destroy(udp_data.shim_data);
 
-        pthread_rwlock_destroy(&udp_data.flows_lock);
-        pthread_mutex_destroy(&udp_data.fd_set_lock);
-        pthread_cond_destroy(&udp_data.fd_set_cond);
-}
-
-static void set_fd(int fd)
-{
-        pthread_mutex_lock(&udp_data.fd_set_lock);
-
-        udp_data.fd_set_mod = true;
-        FD_SET(fd, &udp_data.flow_fd_s);
-
-        while (udp_data.fd_set_mod)
-                pthread_cond_wait(&udp_data.fd_set_cond, &udp_data.fd_set_lock);
-
-        pthread_mutex_unlock(&udp_data.fd_set_lock);
-}
-
-static void clr_fd(int fd)
-{
-        pthread_mutex_lock(&udp_data.fd_set_lock);
-
-        udp_data.fd_set_mod = true;
-        FD_CLR(fd, &udp_data.flow_fd_s);
-
-        while (udp_data.fd_set_mod)
-                pthread_cond_wait(&udp_data.fd_set_cond, &udp_data.fd_set_lock);
-
-        pthread_mutex_unlock(&udp_data.fd_set_lock);
-}
-
-static int send_shim_udp_msg(uint8_t * buf,
-                             size_t    len,
-                             uint32_t  dst_ip_addr)
-{
-       struct sockaddr_in r_saddr;
-
-       memset((char *)&r_saddr, 0, sizeof(r_saddr));
-       r_saddr.sin_family      = AF_INET;
-       r_saddr.sin_addr.s_addr = dst_ip_addr;
-       r_saddr.sin_port        = LISTEN_PORT;
-
-       if (sendto(udp_data.s_fd, buf, len, 0,
-                  (struct sockaddr *) &r_saddr,
-                  sizeof(r_saddr)) == -1) {
-               log_err("Failed to send message.");
-               return -1;
-       }
+        fqueue_destroy(udp_data.fq);
+        fset_destroy(udp_data.np1_flows);
 
-       return 0;
+        pthread_rwlock_destroy(&udp_data.flows_lock);
+        pthread_cond_destroy(&udp_data.mgmt_cond);
+        pthread_mutex_destroy(&udp_data.mgmt_lock);
 }
 
-static int ipcp_udp_port_alloc(uint32_t        dst_ip_addr,
-                               uint16_t        src_udp_port,
+static int ipcp_udp_port_alloc(int             skfd,
+                               uint32_t        s_eid,
                                const uint8_t * dst,
                                qosspec_t       qs)
 {
         uint8_t *         buf;
         struct mgmt_msg * msg;
         size_t            len;
-        int               ret;
 
         len = sizeof(*msg) + ipcp_dir_hash_len();
 
@@ -240,8 +207,9 @@ static int ipcp_udp_port_alloc(uint32_t        dst_ip_addr,
                 return -1;
 
         msg               = (struct mgmt_msg *) buf;
+        msg->eid          = hton32(MGMT_EID);
         msg->code         = FLOW_REQ;
-        msg->src_udp_port = src_udp_port;
+        msg->s_eid        = hton32(s_eid);
         msg->delay        = hton32(qs.delay);
         msg->bandwidth    = hton64(qs.bandwidth);
         msg->availability = qs.availability;
@@ -252,73 +220,63 @@ static int ipcp_udp_port_alloc(uint32_t        dst_ip_addr,
 
         memcpy(msg + 1, dst, ipcp_dir_hash_len());
 
-        ret = send_shim_udp_msg(buf, len, dst_ip_addr);
+        if (write(skfd, msg, len) < 0) {
+                free(buf);
+                return -1;
+        }
 
         free(buf);
 
-        return ret;
+        return 0;
 }
 
-static int ipcp_udp_port_alloc_resp(uint32_t dst_ip_addr,
-                                    uint16_t src_udp_port,
-                                    uint16_t dst_udp_port,
-                                    int      response)
+static int ipcp_udp_port_alloc_resp(int      skfd,
+                                    uint32_t s_eid,
+                                    uint32_t d_eid,
+                                    int8_t   response)
 {
-        struct mgmt_msg * msg;
-        int               ret;
+        struct mgmt_msg *  msg;
 
         msg = malloc(sizeof(*msg));
         if (msg == NULL)
                 return -1;
 
-        msg->code         = FLOW_REPLY;
-        msg->src_udp_port = src_udp_port;
-        msg->dst_udp_port = dst_udp_port;
-        msg->response     = response;
+        msg->eid      = hton32(MGMT_EID);
+        msg->code     = FLOW_REPLY;
+        msg->s_eid    = hton32(s_eid);
+        msg->d_eid    = hton32(d_eid);
+        msg->response = response;
 
-        ret = send_shim_udp_msg((uint8_t *) msg, sizeof(*msg), dst_ip_addr);
+        if (write(skfd, msg, sizeof(*msg)) < 0) {
+                free(msg);
+                return -1;
+        }
 
         free(msg);
 
-        return ret;
+        return 0;
 }
 
 static int ipcp_udp_port_req(struct sockaddr_in * c_saddr,
+                             int                  d_eid,
                              const uint8_t *      dst,
                              qosspec_t            qs)
 {
-        struct timespec    ts          = {0, FD_UPDATE_TIMEOUT * 1000};
-        struct timespec    abstime;
-        struct sockaddr_in f_saddr;
-        socklen_t          f_saddr_len = sizeof(f_saddr);
-        int                skfd;
-        int                fd;
+        struct timespec ts        = {0, FD_UPDATE_TIMEOUT * 1000};
+        struct timespec abstime;
+        int             skfd;
+        int             fd;
 
-        log_dbg("Port request arrived from UDP port %d",
-                 ntohs(c_saddr->sin_port));
-
-        if ((skfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
+        skfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+        if (skfd < 0) {
                 log_err("Could not create UDP socket.");
                 return -1;
         }
 
-        memset((char *) &f_saddr, 0, sizeof(f_saddr));
-        f_saddr.sin_family      = AF_INET;
-        f_saddr.sin_addr.s_addr = local_ip;
-        f_saddr.sin_port        = 0;
-
-        if (bind(skfd, (struct sockaddr *) &f_saddr, sizeof(f_saddr)) < 0) {
-                log_err("Could not bind to socket.");
-                close(skfd);
-                return -1;
-        }
+        /* Remote listens on server port. Mod of c_saddr allowed. */
+        c_saddr->sin_port = udp_data.s_saddr.sin_port;
 
-        if (getsockname(skfd, (struct sockaddr *) &f_saddr, &f_saddr_len) < 0) {
-                log_err("Could not get address from fd.");
-                return -1;
-        }
-
-        /* connect stores the remote address in the file descriptor */
+        /* Connect stores the remote address in the file descriptor. */
         if (connect(skfd, (struct sockaddr *) c_saddr, sizeof(*c_saddr)) < 0) {
                 log_err("Could not connect to remote UDP client.");
                 close(skfd);
@@ -331,8 +289,7 @@ static int ipcp_udp_port_req(struct sockaddr_in * c_saddr,
 
         while (ipcpi.alloc_id != -1 && ipcp_get_state() == IPCP_OPERATIONAL) {
                 ts_add(&abstime, &ts, &abstime);
-                pthread_cond_timedwait(&ipcpi.alloc_cond,
-                                       &ipcpi.alloc_lock,
+                pthread_cond_timedwait(&ipcpi.alloc_cond, &ipcpi.alloc_lock,
                                        &abstime);
         }
 
@@ -354,9 +311,8 @@ static int ipcp_udp_port_req(struct sockaddr_in * c_saddr,
 
         pthread_rwlock_wrlock(&udp_data.flows_lock);
 
-        udp_data.uf_to_fd[skfd]    = fd;
-        udp_data.fd_to_uf[fd].skfd = skfd;
-        udp_data.fd_to_uf[fd].udp  = f_saddr.sin_port;
+        udp_data.fd_to_uf[fd].skfd  = skfd;
+        udp_data.fd_to_uf[fd].d_eid = d_eid;
 
         pthread_rwlock_unlock(&udp_data.flows_lock);
 
@@ -365,224 +321,228 @@ static int ipcp_udp_port_req(struct sockaddr_in * c_saddr,
 
         pthread_mutex_unlock(&ipcpi.alloc_lock);
 
-        log_dbg("Pending allocation request, fd %d, UDP port (%d, %d).",
-                fd, ntohs(f_saddr.sin_port), ntohs(c_saddr->sin_port));
+        log_dbg("Pending allocation request, fd %d, remote eid %d.",
+                fd, d_eid);
 
         return 0;
 }
 
-/* returns the n flow descriptor */
-static int udp_port_to_fd(int udp_port)
+static int ipcp_udp_port_alloc_reply(uint32_t s_eid,
+                                     uint32_t d_eid,
+                                     int8_t   response)
 {
-        int i;
-
-        for (i = 0; i < SYS_MAX_FLOWS; ++i)
-                if (udp_data.fd_to_uf[i].udp == udp_port)
-                        return i;
-
-        return -1;
-}
-
-static int ipcp_udp_port_alloc_reply(uint16_t src_udp_port,
-                                     uint16_t dst_udp_port,
-                                     int      response)
-{
-        int fd   = -1;
-        int ret  =  0;
-        int skfd = -1;
-
         struct sockaddr_in t_saddr;
-        socklen_t          t_saddr_len = sizeof(t_saddr);
+        socklen_t          t_saddr_len;
+        int                ret         = 0;
+        int                skfd        = -1;
 
-        log_dbg("Received reply for flow on udp port %d.",
-                ntohs(dst_udp_port));
+        t_saddr_len = sizeof(t_saddr);
 
-        pthread_rwlock_rdlock(&udp_data.flows_lock);
+        pthread_rwlock_wrlock(&udp_data.flows_lock);
 
-        fd = udp_port_to_fd(dst_udp_port);
-        if (fd < 0) {
+        skfd = udp_data.fd_to_uf[s_eid].skfd;
+        if (skfd < 0) {
                 pthread_rwlock_unlock(&udp_data.flows_lock);
+                log_err("Got reply for unknown UDP eid: %u.", s_eid);
                 return -1;
         }
 
-        skfd = udp_data.fd_to_uf[fd].skfd;
+        udp_data.fd_to_uf[s_eid].d_eid = d_eid;
 
         pthread_rwlock_unlock(&udp_data.flows_lock);
 
-        /* get the original address with the LISTEN PORT */
         if (getpeername(skfd, (struct sockaddr *) &t_saddr, &t_saddr_len) < 0) {
-                log_dbg("Flow with fd %d has no peer.", fd);
+                log_dbg("Flow with fd %d has no peer.", s_eid);
+                close(skfd);
                 return -1;
         }
 
-        /* connect to the flow udp port */
-        t_saddr.sin_port = src_udp_port;
-
         if (connect(skfd, (struct sockaddr *) &t_saddr, sizeof(t_saddr)) < 0) {
+                log_dbg("Could not connect flow to remote.");
                 close(skfd);
                 return -1;
         }
 
-        pthread_rwlock_rdlock(&udp_data.flows_lock);
-
-        set_fd(skfd);
-
-        pthread_rwlock_unlock(&udp_data.flows_lock);
-
-        if (ipcp_flow_alloc_reply(fd, response) < 0)
+        if (ipcp_flow_alloc_reply(s_eid, response) < 0) {
+                log_dbg("Failed to reply to flow allocation.");
                 return -1;
+        }
 
-        log_dbg("Flow allocation completed, UDP ports: (%d, %d).",
-                 ntohs(dst_udp_port), ntohs(src_udp_port));
+        log_dbg("Flow allocation completed on eids (%d, %d).",
+                 s_eid, d_eid);
 
         return ret;
 }
 
-static void * ipcp_udp_listener(void * o)
+static int ipcp_udp_mgmt_frame(const uint8_t *    buf,
+                               struct sockaddr_in c_saddr)
 {
-        uint8_t            buf[SHIM_UDP_MSG_SIZE];
-        ssize_t            n   = 0;
-        struct sockaddr_in c_saddr;
-        int                sfd = udp_data.s_fd;
+        struct mgmt_msg * msg;
+        qosspec_t         qs;
+
+        msg = (struct mgmt_msg *) buf;
+
+        switch (msg->code) {
+        case FLOW_REQ:
+                qs.delay        = ntoh32(msg->delay);
+                qs.bandwidth    = ntoh64(msg->bandwidth);
+                qs.availability = msg->availability;
+                qs.loss         = ntoh32(msg->loss);
+                qs.ber          = ntoh32(msg->ber);
+                qs.in_order     = msg->in_order;
+                qs.max_gap      = ntoh32(msg->max_gap);
+                return ipcp_udp_port_req(&c_saddr, ntoh32(msg->s_eid),
+                                         (uint8_t *) (msg + 1), qs);
+        case FLOW_REPLY:
+                return ipcp_udp_port_alloc_reply(ntoh32(msg->s_eid),
+                                                 ntoh32(msg->d_eid),
+                                                 msg->response);
+        default:
+                log_err("Unknown message received %d.", msg->code);
+                return -1;
+        }
+}
 
+static void * ipcp_udp_mgmt_handler(void * o)
+{
         (void) o;
 
+        pthread_cleanup_push((void (*)(void *)) pthread_mutex_unlock,
+                             (void *) &udp_data.mgmt_lock);
+
         while (true) {
-                struct mgmt_msg * msg = NULL;
-                qosspec_t         qs;
-                memset(&buf, 0, SHIM_UDP_MSG_SIZE);
-                n = recvfrom(sfd, buf, SHIM_UDP_MSG_SIZE, 0,
-                             (struct sockaddr *) &c_saddr,
-                             (socklen_t *) sizeof(c_saddr));
-                if (n < 0)
-                        continue;
+                struct mgmt_frame * frame;
 
-                /* flow alloc request from other host */
-                if (gethostbyaddr((const char *) &c_saddr.sin_addr.s_addr,
-                                  sizeof(c_saddr.sin_addr.s_addr), AF_INET)
-                    == NULL)
-                        continue;
+                pthread_mutex_lock(&udp_data.mgmt_lock);
 
-                msg = (struct mgmt_msg *) buf;
-
-                switch (msg->code) {
-                case FLOW_REQ:
-                        c_saddr.sin_port = msg->src_udp_port;
-                        qs.delay = ntoh32(msg->delay);
-                        qs.bandwidth = ntoh64(msg->bandwidth);
-                        qs.availability = msg->availability;
-                        qs.loss = ntoh32(msg->loss);
-                        qs.ber = ntoh32(msg->ber);
-                        qs.in_order = msg->in_order;
-                        qs.max_gap = ntoh32(msg->max_gap);
-                        ipcp_udp_port_req(&c_saddr,
-                                          (uint8_t *) (msg + 1),
-                                          qs);
-                        break;
-                case FLOW_REPLY:
-                        ipcp_udp_port_alloc_reply(msg->src_udp_port,
-                                                  msg->dst_udp_port,
-                                                  msg->response);
-                        break;
-                default:
-                        log_err("Unknown message received %d.", msg->code);
-                        continue;
-                }
+                while (list_is_empty(&udp_data.mgmt_frames))
+                        pthread_cond_wait(&udp_data.mgmt_cond,
+                                          &udp_data.mgmt_lock);
+
+                frame = list_first_entry((&udp_data.mgmt_frames),
+                                         struct mgmt_frame, next);
+                assert(frame != NULL);
+                list_del(&frame->next);
+
+                pthread_mutex_unlock(&udp_data.mgmt_lock);
 
-                c_saddr.sin_port = LISTEN_PORT;
+                ipcp_udp_mgmt_frame(frame->buf, frame->r_saddr);
+
+                free(frame);
         }
 
-        return 0;
+        pthread_cleanup_pop(false);
+
+        return (void *) 0;
 }
 
 static void * ipcp_udp_packet_reader(void * o)
 {
-        ssize_t            n;
-        int                skfd;
-        int                fd;
-        /* FIXME: avoid this copy */
-        char               buf[SHIM_UDP_MAX_PACKET_SIZE];
-        struct sockaddr_in r_saddr;
-        struct timeval     tv = {0, FD_UPDATE_TIMEOUT};
-        fd_set             read_fds;
-        int                flags;
+        uint8_t   buf[IPCP_UDP_MAX_PACKET_SIZE];
+        uint8_t * data;
+        ssize_t   n;
+        uint32_t  eid;
 
         (void) o;
 
-        ipcp_lock_to_core();
+        data = buf + sizeof(uint32_t);
 
         while (true) {
-                pthread_rwlock_rdlock(&udp_data.flows_lock);
-                pthread_mutex_lock(&udp_data.fd_set_lock);
+                struct mgmt_frame * frame;
+                struct sockaddr_in  r_saddr;
+                socklen_t           len;
 
-                read_fds = udp_data.flow_fd_s;
-                udp_data.fd_set_mod = false;
-                pthread_cond_broadcast(&udp_data.fd_set_cond);
+                len = sizeof(r_saddr);
 
-                pthread_mutex_unlock(&udp_data.fd_set_lock);
-                pthread_rwlock_unlock(&udp_data.flows_lock);
+                n = recvfrom(udp_data.s_fd, buf, IPCP_UDP_MAX_PACKET_SIZE, 0,
+                             (struct sockaddr *) &r_saddr, &len);
+                if (n < 0)
+                        continue;
 
-                if (select(FD_SETSIZE, &read_fds, NULL, NULL, &tv) <= 0)
+                if (n == 0)
+                        log_dbg("Got a 0 frame.");
+
+                if ((size_t) n < sizeof(eid)) {
+                        log_dbg("Dropped bad frame.");
                         continue;
+                }
 
-                for (skfd = 0; skfd < FD_SETSIZE; ++skfd) {
-                        if (!FD_ISSET(skfd, &read_fds))
-                                continue;
-                        flags = fcntl(skfd, F_GETFL, 0);
-                        fcntl(skfd, F_SETFL, flags | O_NONBLOCK);
-                        n = sizeof(r_saddr);
-                        if ((n = recvfrom(skfd,
-                                          &buf,
-                                          SHIM_UDP_MAX_PACKET_SIZE,
-                                          0,
-                                          (struct sockaddr *) &r_saddr,
-                                          (unsigned *) &n)) <= 0)
-                                continue;
+                eid = ntoh32(*((uint32_t *) buf));
 
-                        pthread_rwlock_rdlock(&udp_data.flows_lock);
+                /* pass onto mgmt queue */
+                if (eid == MGMT_EID) {
+                        if (n > IPCP_UDP_MSG_SIZE) {
+                                log_warn("Dropped oversize management frame.");
+                                continue;
+                        }
 
-                        fd = udp_data.uf_to_fd[skfd];
+                        frame = malloc(sizeof(*frame));
+                        if (frame == NULL)
+                                continue;
 
-                        pthread_rwlock_unlock(&udp_data.flows_lock);
+                        memcpy(frame->buf, buf, n);
+                        memcpy(&frame->r_saddr, &r_saddr, sizeof(r_saddr));
 
-                        flow_write(fd, buf, n);
+                        pthread_mutex_lock(&udp_data.mgmt_lock);
+                        list_add(&frame->next, &udp_data.mgmt_frames);
+                        pthread_cond_signal(&udp_data.mgmt_cond);
+                        pthread_mutex_unlock(&udp_data.mgmt_lock);
+                        continue;
                 }
+
+                flow_write(eid, data, n - sizeof(eid));
         }
 
-        return (void *) 0;
+        return 0;
 }
 
-static void * ipcp_udp_packet_loop(void * o)
+static void * ipcp_udp_packet_writer(void * o)
 {
-        int fd;
-        struct shm_du_buff * sdb;
-
         (void) o;
 
         ipcp_lock_to_core();
 
         while (true) {
+                int fd;
+                int eid;
                 fevent(udp_data.np1_flows, udp_data.fq, NULL);
                 while ((fd = fqueue_next(udp_data.fq)) >= 0) {
+                        struct shm_du_buff * sdb;
+                        uint8_t *            buf;
+                        uint16_t             len;
                         if (ipcp_flow_read(fd, &sdb)) {
-                                log_err("Bad read from fd %d.", fd);
+                                log_dbg("Bad read from fd %d.", fd);
+                                continue;
+                        }
+
+                        len = shm_du_buff_tail(sdb) - shm_du_buff_head(sdb);
+                        if (len > IPCP_UDP_MAX_PACKET_SIZE) {
+                                log_dbg("Packet length exceeds MTU.");
+                                ipcp_sdb_release(sdb);
+                                continue;
+                        }
+
+                        buf = shm_du_buff_head_alloc(sdb, OUR_HEADER_LEN);
+                        if (buf == NULL) {
+                                log_dbg("Failed to allocate header.");
+                                ipcp_sdb_release(sdb);
                                 continue;
                         }
 
                         pthread_rwlock_rdlock(&udp_data.flows_lock);
 
+                        eid = hton32(udp_data.fd_to_uf[fd].d_eid);
                         fd = udp_data.fd_to_uf[fd].skfd;
 
                         pthread_rwlock_unlock(&udp_data.flows_lock);
 
+                        memcpy(buf, &eid, sizeof(eid));
+
                         pthread_cleanup_push((void (*)(void *))
-                                             ipcp_sdb_release,
-                                             (void *) sdb);
+                                             ipcp_sdb_release, (void *) sdb);
 
-                        if (send(fd, shm_du_buff_head(sdb),
-                                 shm_du_buff_tail(sdb) - shm_du_buff_head(sdb),
-                                 0) < 0)
-                                log_err("Failed to send PACKET.");
+                        if (write(fd, buf, len + OUR_HEADER_LEN) < 0)
+                                log_err("Failed to send packet.");
 
                         pthread_cleanup_pop(true);
                 }
@@ -593,28 +553,23 @@ static void * ipcp_udp_packet_loop(void * o)
 
 static int ipcp_udp_bootstrap(const struct ipcp_config * conf)
 {
-        struct sockaddr_in s_saddr;
         char ipstr[INET_ADDRSTRLEN];
         char dnsstr[INET_ADDRSTRLEN];
-        int  enable = 1;
-        int  fd = -1;
+        char portstr[128]; /* port is max 64535 = 5 chars */
+        int  i = 1;
 
         assert(conf);
         assert(conf->type == THIS_TYPE);
 
-        if (inet_ntop(AF_INET,
-                      &conf->ip_addr,
-                      ipstr,
-                      INET_ADDRSTRLEN) == NULL) {
+        if (inet_ntop(AF_INET, &conf->ip_addr, ipstr, INET_ADDRSTRLEN)
+            == NULL) {
                 log_err("Failed to convert IP address");
                 return -1;
         }
 
         if (conf->dns_addr != 0) {
-                if (inet_ntop(AF_INET,
-                              &conf->dns_addr,
-                              dnsstr,
-                              INET_ADDRSTRLEN) == NULL) {
+                if (inet_ntop(AF_INET, &conf->dns_addr, dnsstr, INET_ADDRSTRLEN)
+                    == NULL) {
                         log_err("Failed to convert DNS address");
                         return -1;
                 }
@@ -626,76 +581,79 @@ static int ipcp_udp_bootstrap(const struct ipcp_config * conf)
         }
 
         /* UDP listen server */
-        if ((fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == -1) {
-                log_err("Can't create socket.");
+        udp_data.s_fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
+        if (udp_data.s_fd < 0) {
+                log_err("Can't create socket: %s", strerror(errno));
                 goto fail_socket;
         }
 
-        if (setsockopt(fd,
-                       SOL_SOCKET,
-                       SO_REUSEADDR,
-                       &enable,
-                       sizeof(int)) < 0)
+        if (setsockopt(udp_data.s_fd, SOL_SOCKET, SO_REUSEADDR,
+                       &i, sizeof(i)) < 0)
                 log_warn("Failed to set SO_REUSEADDR.");
 
-        memset((char *) &s_saddr, 0, sizeof(s_saddr));
+        memset((char *) &udp_data.s_saddr, 0, sizeof(udp_data.s_saddr));
         udp_data.s_saddr.sin_family      = AF_INET;
         udp_data.s_saddr.sin_addr.s_addr = conf->ip_addr;
-        udp_data.s_saddr.sin_port        = LISTEN_PORT;
+        udp_data.s_saddr.sin_port        = htons(conf->srv_port);
 
-        if (bind(fd,
-                 (struct sockaddr *) &udp_data.s_saddr,
-                 sizeof(udp_data.s_saddr)) < 0) {
+        if (bind(udp_data.s_fd, SERV_SADDR, SERV_SADDR_SIZE) < 0) {
                 log_err("Couldn't bind to %s.", ipstr);
                 goto fail_bind;
         }
 
-        udp_data.s_fd     = fd;
         udp_data.ip_addr  = conf->ip_addr;
         udp_data.dns_addr = conf->dns_addr;
-
-        FD_CLR(udp_data.s_fd, &udp_data.flow_fd_s);
+        udp_data.clt_port = htons(conf->clt_port);
 
         ipcp_set_state(IPCP_OPERATIONAL);
 
-        if (pthread_create(&udp_data.handler,
-                           NULL,
-                           ipcp_udp_listener,
-                           NULL)) {
+        if (pthread_create(&udp_data.mgmt_handler, NULL,
+                           ipcp_udp_mgmt_handler, NULL)) {
                 ipcp_set_state(IPCP_INIT);
                 goto fail_bind;
         }
 
-        if (pthread_create(&udp_data.packet_reader,
-                           NULL,
-                           ipcp_udp_packet_reader,
-                           NULL)) {
-                ipcp_set_state(IPCP_INIT);
-                goto fail_packet_reader;
+        for (i = 0; i < IPCP_UDP_RD_THR; ++i) {
+                if (pthread_create(&udp_data.packet_reader[i], NULL,
+                                   ipcp_udp_packet_reader, NULL)) {
+                        ipcp_set_state(IPCP_INIT);
+                        goto fail_packet_reader;
+                }
         }
 
-        if (pthread_create(&udp_data.packet_loop,
-                           NULL,
-                           ipcp_udp_packet_loop,
-                           NULL)) {
-                ipcp_set_state(IPCP_INIT);
-                goto fail_packet_loop;
+        for (i = 0; i < IPCP_UDP_WR_THR; ++i) {
+                if (pthread_create(&udp_data.packet_writer[i], NULL,
+                        ipcp_udp_packet_writer, NULL)) {
+                        ipcp_set_state(IPCP_INIT);
+                        goto fail_packet_writer;
+                }
         }
 
+        sprintf(portstr, "%d", conf->clt_port);
+
         log_dbg("Bootstrapped IPCP over UDP with pid %d.", getpid());
         log_dbg("Bound to IP address %s.", ipstr);
+        log_dbg("Client port is %s.", conf->clt_port == 0 ? "random" : portstr);
+        log_dbg("Server port is %u.", conf->srv_port);
         log_dbg("DNS server address is %s.", dnsstr);
 
         return 0;
 
- fail_packet_loop:
-        pthread_cancel(udp_data.packet_reader);
-        pthread_join(udp_data.packet_reader, NULL);
+ fail_packet_writer:
+        while (i > 0) {
+                pthread_cancel(udp_data.packet_writer[--i]);
+                pthread_join(udp_data.packet_writer[i], NULL);
+        }
+        i = IPCP_UDP_RD_THR;
  fail_packet_reader:
-        pthread_cancel(udp_data.handler);
-        pthread_join(udp_data.handler, NULL);
+        while (i > 0) {
+                pthread_cancel(udp_data.packet_reader[--i]);
+                pthread_join(udp_data.packet_reader[i], NULL);
+        }
+        pthread_cancel(udp_data.mgmt_handler);
+        pthread_join(udp_data.mgmt_handler, NULL);
  fail_bind:
-        close(fd);
+        close(udp_data.s_fd);
  fail_socket:
         return -1;
 }
@@ -705,9 +663,9 @@ static int ipcp_udp_bootstrap(const struct ipcp_config * conf)
 /* NOTE: Disgusted with this crap */
 static int ddns_send(char * cmd)
 {
-        pid_t pid = -1;
-        int wstatus;
-        int pipe_fd[2];
+        pid_t pid     = -1;
+        int   wstatus;
+        int   pipe_fd[2];
         char * argv[] = {NSUPDATE_EXEC, 0};
         char * envp[] = {0};
 
@@ -743,22 +701,23 @@ static int ddns_send(char * cmd)
                 log_err("Failed to register with DNS server.");
 
         close(pipe_fd[1]);
+
         return 0;
 }
 
 static uint32_t ddns_resolve(char *   name,
                              uint32_t dns_addr)
 {
-        pid_t pid = -1;
-        int wstatus;
-        int pipe_fd[2];
-        char dnsstr[INET_ADDRSTRLEN];
-        char buf[SHIM_UDP_BUF_SIZE];
-        ssize_t count = 0;
-        char * substr = NULL;
-        char * substr2 = NULL;
-        char * addr_str = "Address:";
-        uint32_t ip_addr = 0;
+        pid_t    pid      = -1;
+        int      wstatus;
+        int      pipe_fd[2];
+        char     dnsstr[INET_ADDRSTRLEN];
+        char     buf[IPCP_UDP_BUF_SIZE];
+        ssize_t  count    = 0;
+        char *   substr   = NULL;
+        char *   substr2  = NULL;
+        char *   addr_str = "Address:";
+        uint32_t ip_addr  = 0;
 
         if (inet_ntop(AF_INET, &dns_addr, dnsstr, INET_ADDRSTRLEN) == NULL)
                 return 0;
@@ -785,7 +744,7 @@ static uint32_t ddns_resolve(char *   name,
 
         close(pipe_fd[1]);
 
-        count = read(pipe_fd[0], buf, SHIM_UDP_BUF_SIZE);
+        count = read(pipe_fd[0], buf, IPCP_UDP_BUF_SIZE);
         if (count <= 0) {
                 log_err("Failed to communicate with nslookup.");
                 close(pipe_fd[0]);
@@ -796,7 +755,7 @@ static uint32_t ddns_resolve(char *   name,
 
         waitpid(pid, &wstatus, 0);
         if (WIFEXITED(wstatus) && WEXITSTATUS(wstatus) == 0 &&
-            count != SHIM_UDP_BUF_SIZE)
+            count != IPCP_UDP_BUF_SIZE)
                 log_dbg("Succesfully communicated with nslookup.");
         else
                 log_err("Failed to resolve DNS address.");
@@ -825,13 +784,13 @@ static uint32_t ddns_resolve(char *   name,
 static int ipcp_udp_reg(const uint8_t * hash)
 {
 #ifdef HAVE_DDNS
-        char ipstr[INET_ADDRSTRLEN];
-        char dnsstr[INET_ADDRSTRLEN];
-        char cmd[1000];
+        char     ipstr[INET_ADDRSTRLEN];
+        char     dnsstr[INET_ADDRSTRLEN];
+        char     cmd[1000];
         uint32_t dns_addr;
         uint32_t ip_addr;
 #endif
-        char * hashstr;
+        char *   hashstr;
 
         hashstr = malloc(ipcp_dir_hash_strlen() + 1);
         if (hashstr == NULL)
@@ -888,12 +847,12 @@ static int ipcp_udp_reg(const uint8_t * hash)
 static int ipcp_udp_unreg(const uint8_t * hash)
 {
 #ifdef HAVE_DDNS
-        char dnsstr[INET_ADDRSTRLEN];
+        char     dnsstr[INET_ADDRSTRLEN];
         /* max DNS name length + max IP length + max command length */
-        char cmd[100];
+        char     cmd[100];
         uint32_t dns_addr;
 #endif
-        char * hashstr;
+        char *   hashstr;
 
         assert(hash);
 
@@ -932,13 +891,12 @@ static int ipcp_udp_unreg(const uint8_t * hash)
 
 static int ipcp_udp_query(const uint8_t * hash)
 {
-        uint32_t           ip_addr = 0;
-        char *             hashstr;
-        struct hostent *   h;
+        uint32_t         ip_addr  = 0;
+        char *           hashstr;
+        struct hostent * h;
 #ifdef HAVE_DDNS
-        uint32_t           dns_addr = 0;
+        uint32_t         dns_addr = 0;
 #endif
-
         assert(hash);
 
         hashstr = malloc(ipcp_dir_hash_strlen() + 1);
@@ -991,11 +949,14 @@ static int ipcp_udp_flow_alloc(int             fd,
                                const uint8_t * dst,
                                qosspec_t       qs)
 {
-        struct sockaddr_in r_saddr; /* server address */
-        struct sockaddr_in f_saddr; /* flow */
-        socklen_t          f_saddr_len = sizeof(f_saddr);
+        struct sockaddr_in r_saddr; /* Server address */
+        struct sockaddr_in c_saddr; /* Client address */
+        socklen_t          c_saddr_len;
         int                skfd;
         uint32_t           ip_addr = 0;
+        char               ip_str[INET_ADDRSTRLEN];
+
+        c_saddr_len = sizeof(c_saddr);
 
         log_dbg("Allocating flow to " HASH_FMT ".", HASH_VAL(dst));
 
@@ -1004,21 +965,24 @@ static int ipcp_udp_flow_alloc(int             fd,
         assert(dst);
 
         skfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
-        if (skfd < 0)
+        if (skfd < 0) {
+                log_err("Could not create socket.");
                 return -1;
+        }
 
-        /* this socket is for the flow */
-        memset((char *) &f_saddr, 0, sizeof(f_saddr));
-        f_saddr.sin_family      = AF_INET;
-        f_saddr.sin_addr.s_addr = local_ip;
-        f_saddr.sin_port        = 0;
+        /* This socket is for the flow. */
+        memset((char *) &c_saddr, 0, sizeof(c_saddr));
+        c_saddr.sin_family      = AF_INET;
+        c_saddr.sin_addr.s_addr = LOCAL_IP;
+        c_saddr.sin_port        = udp_data.clt_port;
 
-        if (bind(skfd, (struct sockaddr *) &f_saddr, sizeof(f_saddr)) < 0) {
+        if (bind(skfd, (struct sockaddr *) &c_saddr, sizeof(c_saddr)) < 0) {
+                log_dbg("Could not bind socket to client address.");
                 close(skfd);
                 return -1;
         }
 
-        if (getsockname(skfd, (struct sockaddr *) &f_saddr, &f_saddr_len) < 0) {
+        if (getsockname(skfd, (struct sockaddr *) &c_saddr, &c_saddr_len) < 0) {
                 log_err("Could not get address from fd.");
                 close(skfd);
                 return -1;
@@ -1029,43 +993,41 @@ static int ipcp_udp_flow_alloc(int             fd,
                 close(skfd);
                 return -1;
         }
+
         ip_addr = (uint32_t) shim_data_dir_get_addr(udp_data.shim_data, dst);
 
-        /* connect to server (store the remote IP address in the fd) */
+        inet_ntop(AF_INET, &ip_addr, ip_str, INET_ADDRSTRLEN);
+        log_dbg("Destination UDP ipcp resolved at %s.", ip_str);
+
+        /* Connect to server and store the remote IP address in the skfd. */
         memset((char *) &r_saddr, 0, sizeof(r_saddr));
         r_saddr.sin_family      = AF_INET;
         r_saddr.sin_addr.s_addr = ip_addr;
-        r_saddr.sin_port        = LISTEN_PORT;
+        r_saddr.sin_port        = udp_data.s_saddr.sin_port;
 
         if (connect(skfd, (struct sockaddr *) &r_saddr, sizeof(r_saddr)) < 0) {
+                log_dbg("Could not connect socket to remote.");
+                close(skfd);
+                return -1;
+        }
+
+        if (ipcp_udp_port_alloc(skfd, fd, dst, qs) < 0) {
+                log_err("Could not allocate port.");
                 close(skfd);
                 return -1;
         }
 
         pthread_rwlock_wrlock(&udp_data.flows_lock);
 
-        udp_data.fd_to_uf[fd].udp  = f_saddr.sin_port;
-        udp_data.fd_to_uf[fd].skfd = skfd;
-        udp_data.uf_to_fd[skfd]    = fd;
+        udp_data.fd_to_uf[fd].d_eid = -1;
+        udp_data.fd_to_uf[fd].skfd  = skfd;
 
         fset_add(udp_data.np1_flows, fd);
 
         pthread_rwlock_unlock(&udp_data.flows_lock);
 
-        if (ipcp_udp_port_alloc(ip_addr, f_saddr.sin_port, dst, qs) < 0) {
-                pthread_rwlock_wrlock(&udp_data.flows_lock);
-
-                udp_data.fd_to_uf[fd].udp  = -1;
-                udp_data.fd_to_uf[fd].skfd = -1;
-                udp_data.uf_to_fd[skfd]    = -1;
-
-                pthread_rwlock_unlock(&udp_data.flows_lock);
-                close(skfd);
-                return -1;
-        }
-
-        log_dbg("Flow pending on fd %d, UDP port %d.",
-                fd, ntohs(f_saddr.sin_port));
+        log_dbg("Flow pending on fd %d, UDP src port %d, dst port %d.",
+                fd, ntohs(c_saddr.sin_port), ntohs(r_saddr.sin_port));
 
         return 0;
 }
@@ -1073,12 +1035,10 @@ static int ipcp_udp_flow_alloc(int             fd,
 static int ipcp_udp_flow_alloc_resp(int fd,
                                     int response)
 {
-        struct timespec    ts   = {0, FD_UPDATE_TIMEOUT * 1000};
-        struct timespec    abstime;
-        int                skfd = -1;
-        struct sockaddr_in f_saddr;
-        struct sockaddr_in r_saddr;
-        socklen_t          len  = sizeof(r_saddr);
+        struct timespec ts  = {0, FD_UPDATE_TIMEOUT * 1000};
+        struct timespec abstime;
+        int             skfd;
+        int             d_eid;
 
         if (response)
                 return 0;
@@ -1106,38 +1066,23 @@ static int ipcp_udp_flow_alloc_resp(int fd,
 
         pthread_rwlock_rdlock(&udp_data.flows_lock);
 
-        skfd = udp_data.fd_to_uf[fd].skfd;
-
-        pthread_rwlock_unlock(&udp_data.flows_lock);
-
-        if (getsockname(skfd, (struct sockaddr *) &f_saddr, &len) < 0) {
-                log_dbg("Socket with fd %d has no address.", skfd);
-                return -1;
-        }
-
-        if (getpeername(skfd, (struct sockaddr *) &r_saddr, &len) < 0) {
-                log_dbg("Socket with fd %d has no peer.", skfd);
-                return -1;
-        }
-
-        pthread_rwlock_rdlock(&udp_data.flows_lock);
-
-        set_fd(skfd);
+        skfd  = udp_data.fd_to_uf[fd].skfd;
+        d_eid = udp_data.fd_to_uf[fd].d_eid;
 
         fset_add(udp_data.np1_flows, fd);
 
         pthread_rwlock_unlock(&udp_data.flows_lock);
 
-        if (ipcp_udp_port_alloc_resp(r_saddr.sin_addr.s_addr, f_saddr.sin_port,
-                                     r_saddr.sin_port, response) < 0) {
+        if (ipcp_udp_port_alloc_resp(skfd, d_eid, fd, response) < 0) {
                 pthread_rwlock_rdlock(&udp_data.flows_lock);
-                clr_fd(skfd);
+                fset_del(udp_data.np1_flows, fd);
                 pthread_rwlock_unlock(&udp_data.flows_lock);
+                log_err("Failed to respond to flow request.");
                 return -1;
         }
 
-        log_dbg("Accepted flow, fd %d on UDP port %d.",
-                fd, ntohs(f_saddr.sin_port));
+        log_dbg("Accepted flow, fd %d on eid %d.",
+                fd, d_eid);
 
         return 0;
 }
@@ -1154,18 +1099,12 @@ static int ipcp_udp_flow_dealloc(int fd)
 
         skfd = udp_data.fd_to_uf[fd].skfd;
 
-        udp_data.uf_to_fd[skfd]    = -1;
-        udp_data.fd_to_uf[fd].udp  = -1;
-        udp_data.fd_to_uf[fd].skfd = -1;
+        udp_data.fd_to_uf[fd].d_eid = -1;
+        udp_data.fd_to_uf[fd].skfd  = -1;
 
         close(skfd);
 
         pthread_rwlock_unlock(&udp_data.flows_lock);
-        pthread_rwlock_rdlock(&udp_data.flows_lock);
-
-        clr_fd(skfd);
-
-        pthread_rwlock_unlock(&udp_data.flows_lock);
 
         flow_dealloc(fd);
 
@@ -1191,6 +1130,8 @@ static struct ipcp_ops udp_ops = {
 int main(int    argc,
          char * argv[])
 {
+        int i;
+
         if (ipcp_init(argc, argv, &udp_ops) < 0)
                 goto fail_init;
 
@@ -1212,13 +1153,17 @@ int main(int    argc,
         ipcp_shutdown();
 
         if (ipcp_get_state() == IPCP_SHUTDOWN) {
-                pthread_cancel(udp_data.packet_loop);
-                pthread_cancel(udp_data.handler);
-                pthread_cancel(udp_data.packet_reader);
-
-                pthread_join(udp_data.packet_loop, NULL);
-                pthread_join(udp_data.handler, NULL);
-                pthread_join(udp_data.packet_reader, NULL);
+                for (i = 0; i < IPCP_UDP_RD_THR; ++i)
+                        pthread_cancel(udp_data.packet_reader[i]);
+                for (i = 0; i < IPCP_UDP_WR_THR; ++i)
+                        pthread_cancel(udp_data.packet_writer[i]);
+                pthread_cancel(udp_data.mgmt_handler);
+
+                for (i = 0; i < IPCP_UDP_RD_THR; ++i)
+                        pthread_join(udp_data.packet_reader[i], NULL);
+                for (i = 0; i < IPCP_UDP_WR_THR; ++i)
+                        pthread_join(udp_data.packet_writer[i], NULL);
+                pthread_join(udp_data.mgmt_handler, NULL);
         }
 
         udp_data_fini();
diff --git a/src/lib/ipcp_config.proto b/src/lib/ipcp_config.proto
index f54e78a0..051a3888 100644
--- a/src/lib/ipcp_config.proto
+++ b/src/lib/ipcp_config.proto
@@ -40,10 +40,12 @@ message ipcp_config_msg {
         // Config for UDP
         optional uint32 ip_addr            =  9;
         optional uint32 dns_addr           = 10;
+        optional uint32 clt_port           = 11;
+        optional uint32 srv_port           = 12;
         // Config for the Ethernet
-        optional string dev                = 11;
+        optional string dev                = 13;
         // Config for DIX Ethernet
-        optional uint32 ethertype          = 12;
+        optional uint32 ethertype          = 14;
 }
 
 enum enroll_code {
diff --git a/src/lib/irm.c b/src/lib/irm.c
index 28864546..6356443f 100644
--- a/src/lib/irm.c
+++ b/src/lib/irm.c
@@ -140,6 +140,10 @@ int irm_bootstrap_ipcp(pid_t                      pid,
                 config.ip_addr      = conf->ip_addr;
                 config.has_dns_addr = true;
                 config.dns_addr     = conf->dns_addr;
+                config.has_srv_port = true;
+                config.srv_port     = conf->srv_port;
+                config.has_clt_port = true;
+                config.clt_port     = conf->clt_port;
                 break;
         case IPCP_LOCAL:
         case IPCP_BROADCAST:
diff --git a/src/tools/irm/irm_ipcp_bootstrap.c b/src/tools/irm/irm_ipcp_bootstrap.c
index 259b4325..7134bf64 100644
--- a/src/tools/irm/irm_ipcp_bootstrap.c
+++ b/src/tools/irm/irm_ipcp_bootstrap.c
@@ -73,6 +73,8 @@
 #define DEFAULT_PFF            PFF_SIMPLE
 #define DEFAULT_HASH_ALGO      DIR_HASH_SHA3_256
 #define DEFAULT_ETHERTYPE      0xA000
+#define DEFAULT_CLIENT_PORT    0x0000 /* random port */
+#define DEFAULT_SERVER_PORT    0x0D6B /* 3435 */
 
 #define FLAT_RANDOM_ADDR_AUTH  "flat"
 #define LINK_STATE_ROUTING     "link_state"
@@ -106,6 +108,8 @@ static void usage(void)
                SHA3_384 " " SHA3_512 "}\n\n"
                "if TYPE == " UDP "\n"
                "                ip <IP address in dotted notation>\n"
+               "                [cport <client port> (default: random)]\n"
+               "                [sport <server port> (default: %d)]\n"
                "                [dns <DDNS IP address in dotted notation>"
                " (default: none)]\n\n"
                "if TYPE == " ETH_LLC "\n"
@@ -126,12 +130,13 @@ static void usage(void)
                "if TYPE == " RAPTOR "\n"
                "                [hash [ALGORITHM] (default: %s)]\n"
                "where ALGORITHM = {" SHA3_224 " " SHA3_256 " "
-               SHA3_384 " " SHA3_512 "}\n"
+               SHA3_384 " " SHA3_512 "}\n\n"
                "if TYPE == " BROADCAST "\n"
                "                [autobind]\n\n",
                DEFAULT_ADDR_SIZE, DEFAULT_EID_SIZE, DEFAULT_TTL,
                FLAT_RANDOM_ADDR_AUTH, LINK_STATE_ROUTING, SIMPLE_PFF,
-               SHA3_256, SHA3_256, 0xA000, SHA3_256, SHA3_256, SHA3_256);
+               SHA3_256, DEFAULT_SERVER_PORT, SHA3_256, 0xA000, SHA3_256,
+               SHA3_256, SHA3_256);
 }
 
 int do_bootstrap_ipcp(int     argc,
@@ -159,6 +164,8 @@ int do_bootstrap_ipcp(int     argc,
         int                i              = 0;
         bool               autobind       = false;
         int                cargs;
+        int                cport          = DEFAULT_CLIENT_PORT;
+        int                sport          = DEFAULT_SERVER_PORT;
 
         while (argc > 0) {
                 cargs = 2;
@@ -205,6 +212,10 @@ int do_bootstrap_ipcp(int     argc,
                         eid_size = atoi(*(argv + 1));
                 } else if (matches(*argv, "ttl") == 0) {
                         max_ttl = atoi(*(argv + 1));
+                } else if (matches(*argv, "cport") == 0) {
+                        cport = atoi(*(argv + 1));
+                } else if (matches(*argv, "sport") == 0) {
+                        sport = atoi(*(argv + 1));
                 } else if (matches(*argv, "autobind") == 0) {
                         autobind = true;
                         cargs = 1;
@@ -318,8 +329,10 @@ int do_bootstrap_ipcp(int     argc,
                         case IPCP_UDP:
                                 if (ip_addr == 0)
                                         goto fail_usage;
-                                conf.ip_addr = ip_addr;
+                                conf.ip_addr  = ip_addr;
                                 conf.dns_addr = dns_addr;
+                                conf.clt_port    = cport;
+                                conf.srv_port    = sport;
                                 break;
                         case IPCP_ETH_LLC:
                                 if (dev == NULL)