Use void pointers for opaque data blobs in the SPTPS code.
[tinc] / src / net_packet.c
index c0be8c4..7ca1894 100644 (file)
@@ -1,7 +1,7 @@
 /*
     net_packet.c -- Handles in- and outgoing VPN packets
     Copyright (C) 1998-2005 Ivo Timmermans,
-                  2000-2012 Guus Sliepen <guus@tinc-vpn.org>
+                  2000-2014 Guus Sliepen <guus@tinc-vpn.org>
                   2010      Timothy Redaelli <timothy@redaelli.eu>
                   2010      Brandon Black <blblack@gmail.com>
 
 
 #include "system.h"
 
-#include <openssl/rand.h>
-#include <openssl/err.h>
-#include <openssl/evp.h>
-#include <openssl/pem.h>
-#include <openssl/hmac.h>
-
 #ifdef HAVE_ZLIB
 #include <zlib.h>
 #endif
@@ -48,7 +42,6 @@
 #include "net.h"
 #include "netutl.h"
 #include "protocol.h"
-#include "process.h"
 #include "route.h"
 #include "utils.h"
 #include "xalloc.h"
@@ -61,7 +54,7 @@ static char lzo_wrkmem[LZO1X_999_MEM_COMPRESS > LZO1X_1_MEM_COMPRESS ? LZO1X_999
 static void send_udppacket(node_t *, vpn_packet_t *);
 
 unsigned replaywin = 16;
-bool localdiscovery = false;
+bool localdiscovery = true;
 
 #define MAX_SEQNO 1073741824
 
@@ -70,11 +63,15 @@ bool localdiscovery = false;
    mtuprobes ==    32: send 1 burst, sleep pingtimeout second
    mtuprobes ==    33: no response from other side, restart PMTU discovery process
 
-   Probes are sent in batches of three, with random sizes between the lower and
-   upper boundaries for the MTU thus far discovered.
+   Probes are sent in batches of at least three, with random sizes between the
+   lower and upper boundaries for the MTU thus far discovered.
+
+   After the initial discovery, a fourth packet is added to each batch with a
+   size larger than the currently known PMTU, to test if the PMTU has increased.
 
-   In case local discovery is enabled, a fourth packet is added to each batch,
+   In case local discovery is enabled, another packet is added to each batch,
    which will be broadcast to the local network.
+
 */
 
 static void send_mtu_probe_handler(void *data) {
@@ -125,13 +122,18 @@ static void send_mtu_probe_handler(void *data) {
                timeout = pingtimeout;
        }
 
-       for(int i = 0; i < 3 + localdiscovery; i++) {
+       for(int i = 0; i < 4 + localdiscovery; i++) {
                int len;
 
-               if(n->maxmtu <= n->minmtu)
+               if(i == 0) {
+                       if(n->mtuprobes < 30 || n->maxmtu + 8 >= MTU)
+                               continue;
+                       len = n->maxmtu + 8;
+               } else if(n->maxmtu <= n->minmtu) {
                        len = n->maxmtu;
-               else
+               } else {
                        len = n->minmtu + 1 + rand() % (n->maxmtu - n->minmtu);
+               }
 
                if(len < 64)
                        len = 64;
@@ -140,16 +142,30 @@ static void send_mtu_probe_handler(void *data) {
                memset(packet.data, 0, 14);
                randomize(packet.data + 14, len - 14);
                packet.len = len;
-               if(i >= 3 && n->mtuprobes <= 10)
-                       packet.priority = -1;
-               else
-                       packet.priority = 0;
+               packet.priority = 0;
+               n->status.send_locally = i >= 4 && n->mtuprobes <= 10 && n->prevedge;
 
                logger(DEBUG_TRAFFIC, LOG_INFO, "Sending MTU probe length %d to %s (%s)", len, n->name, n->hostname);
 
                send_udppacket(n, &packet);
        }
 
+       n->status.send_locally = false;
+       n->probe_counter = 0;
+       gettimeofday(&n->probe_time, NULL);
+
+       /* Calculate the packet loss of incoming traffic by comparing the rate of
+          packets received to the rate with which the sequence number has increased.
+        */
+
+       if(n->received > n->prev_received)
+               n->packetloss = 1.0 - (n->received - n->prev_received) / (float)(n->received_seqno - n->prev_received_seqno);
+       else
+               n->packetloss = n->received_seqno <= n->prev_received_seqno;
+
+       n->prev_received_seqno = n->received_seqno;
+       n->prev_received = n->received;
+
 end:
        timeout_set(&n->mtutimeout, &(struct timeval){timeout, rand() % 100000});
 }
@@ -160,12 +176,25 @@ void send_mtu_probe(node_t *n) {
 }
 
 static void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
-       logger(DEBUG_TRAFFIC, LOG_INFO, "Got MTU probe length %d from %s (%s)", packet->len, n->name, n->hostname);
-
        if(!packet->data[0]) {
+               logger(DEBUG_TRAFFIC, LOG_INFO, "Got MTU probe request %d from %s (%s)", packet->len, n->name, n->hostname);
+
                /* It's a probe request, send back a reply */
 
-               packet->data[0] = 1;
+               /* Type 2 probe replies were introduced in protocol 17.3 */
+               if ((n->options >> 24) >= 3) {
+                       uint8_t* data = packet->data;
+                       *data++ = 2;
+                       uint16_t len16 = htons(len); memcpy(data, &len16, 2); data += 2;
+                       struct timeval now;
+                       gettimeofday(&now, NULL);
+                       uint32_t sec = htonl(now.tv_sec); memcpy(data, &sec, 4); data += 4;
+                       uint32_t usec = htonl(now.tv_usec); memcpy(data, &usec, 4); data += 4;
+                       packet->len = data - packet->data;
+               } else {
+                       /* Legacy protocol: n won't understand type 2 probe replies. */
+                       packet->data[0] = 1;
+               }
 
                /* Temporarily set udp_confirmed, so that the reply is sent
                   back exactly the way it came in. */
@@ -175,6 +204,16 @@ static void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
                send_udppacket(n, packet);
                n->status.udp_confirmed = udp_confirmed;
        } else {
+               length_t probelen = len;
+               if (packet->data[0] == 2) {
+                       if (len < 3)
+                               logger(DEBUG_TRAFFIC, LOG_WARNING, "Received invalid (too short) MTU probe reply from %s (%s)", n->name, n->hostname);
+                       else {
+                               uint16_t probelen16; memcpy(&probelen16, packet->data + 1, 2); probelen = ntohs(probelen16);
+                       }
+               }
+               logger(DEBUG_TRAFFIC, LOG_INFO, "Got type %d MTU probe reply %d from %s (%s)", packet->data[0], probelen, n->name, n->hostname);
+
                /* It's a valid reply: now we know bidirectional communication
                   is possible using the address and socket that the reply
                   packet used. */
@@ -184,6 +223,13 @@ static void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
                /* If we haven't established the PMTU yet, restart the discovery process. */
 
                if(n->mtuprobes > 30) {
+                       if (probelen == n->maxmtu + 8) {
+                               logger(DEBUG_TRAFFIC, LOG_INFO, "Increase in PMTU to %s (%s) detected, restarting PMTU discovery", n->name, n->hostname);
+                               n->maxmtu = MTU;
+                               n->mtuprobes = 10;
+                               return;
+                       }
+
                        if(n->minmtu)
                                n->mtuprobes = 30;
                        else
@@ -192,10 +238,40 @@ static void mtu_probe_h(node_t *n, vpn_packet_t *packet, length_t len) {
 
                /* If applicable, raise the minimum supported MTU */
 
-               if(len > n->maxmtu)
-                       len = n->maxmtu;
-               if(n->minmtu < len)
-                       n->minmtu = len;
+               if(probelen > n->maxmtu)
+                       probelen = n->maxmtu;
+               if(n->minmtu < probelen)
+                       n->minmtu = probelen;
+
+               /* Calculate RTT and bandwidth.
+                  The RTT is the time between the MTU probe burst was sent and the first
+                  reply is received. The bandwidth is measured using the time between the
+                  arrival of the first and third probe reply (or type 2 probe requests).
+                */
+
+               struct timeval now, diff;
+               gettimeofday(&now, NULL);
+               timersub(&now, &n->probe_time, &diff);
+
+               struct timeval probe_timestamp = now;
+               if (packet->data[0] == 2 && packet->len >= 11) {
+                       uint32_t sec; memcpy(&sec, packet->data + 3, 4);
+                       uint32_t usec; memcpy(&usec, packet->data + 7, 4);
+                       probe_timestamp.tv_sec = ntohl(sec);
+                       probe_timestamp.tv_usec = ntohl(usec);
+               }
+               
+               n->probe_counter++;
+
+               if(n->probe_counter == 1) {
+                       n->rtt = diff.tv_sec + diff.tv_usec * 1e-6;
+                       n->probe_time = probe_timestamp;
+               } else if(n->probe_counter == 3) {
+                       struct timeval probe_timestamp_diff;
+                       timersub(&probe_timestamp, &n->probe_time, &probe_timestamp_diff);
+                       n->bandwidth = 2.0 * probelen / (probe_timestamp_diff.tv_sec + probe_timestamp_diff.tv_usec * 1e-6);
+                       logger(DEBUG_TRAFFIC, LOG_DEBUG, "%s (%s) RTT %.2f ms, burst bandwidth %.3f Mbit/s, rx packet loss %.2f %%", n->name, n->hostname, n->rtt * 1e3, n->bandwidth * 8e-6, n->packetloss * 1e2);
+               }
        }
 }
 
@@ -272,58 +348,68 @@ static void receive_packet(node_t *n, vpn_packet_t *packet) {
 
 static bool try_mac(node_t *n, const vpn_packet_t *inpkt) {
        if(n->status.sptps)
-               return sptps_verify_datagram(&n->sptps, (char *)&inpkt->seqno, inpkt->len);
+               return sptps_verify_datagram(&n->sptps, ((sptps_packet_t *)inpkt)->data, inpkt->len);
 
-       if(!digest_active(&n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest))
+       if(!digest_active(n->indigest) || inpkt->len < sizeof inpkt->seqno + digest_length(n->indigest))
                return false;
 
-       return digest_verify(&n->indigest, &inpkt->seqno, inpkt->len - n->indigest.maclength, (const char *)&inpkt->seqno + inpkt->len - n->indigest.maclength);
+       return digest_verify(n->indigest, (const char *)&inpkt->seqno, inpkt->len - digest_length(n->indigest), (const char *)&inpkt->seqno + inpkt->len - digest_length(n->indigest));
 }
 
-static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
+static bool receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
        vpn_packet_t pkt1, pkt2;
        vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
        int nextpkt = 0;
-       vpn_packet_t *outpkt = pkt[0];
        size_t outlen;
 
        if(n->status.sptps) {
-               sptps_receive_data(&n->sptps, (char *)&inpkt->seqno, inpkt->len);
-               return;
+               if(!n->sptps.state) {
+                       if(!n->status.waitingforkey) {
+                               logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but we haven't exchanged keys yet", n->name, n->hostname);
+                               send_req_key(n);
+                       } else {
+                               logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet", n->name, n->hostname);
+                       }
+                       return false;
+               }
+               if(!sptps_receive_data(&n->sptps, ((sptps_packet_t *)inpkt)->data, inpkt->len)) {
+                       logger(DEBUG_TRAFFIC, LOG_ERR, "Got bad packet from %s (%s)", n->name, n->hostname);
+                       return false;
+               }
+               return true;
        }
 
-       if(!cipher_active(&n->incipher)) {
-               logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet",
-                                       n->name, n->hostname);
-               return;
+       if(!n->status.validkey) {
+               logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got packet from %s (%s) but he hasn't got our key yet", n->name, n->hostname);
+               return false;
        }
 
        /* Check packet length */
 
-       if(inpkt->len < sizeof inpkt->seqno + digest_length(&n->indigest)) {
+       if(inpkt->len < sizeof inpkt->seqno + digest_length(n->indigest)) {
                logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got too short packet from %s (%s)",
                                        n->name, n->hostname);
-               return;
+               return false;
        }
 
        /* Check the message authentication code */
 
-       if(digest_active(&n->indigest)) {
-               inpkt->len -= n->indigest.maclength;
-               if(!digest_verify(&n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
+       if(digest_active(n->indigest)) {
+               inpkt->len -= digest_length(n->indigest);
+               if(!digest_verify(n->indigest, &inpkt->seqno, inpkt->len, (const char *)&inpkt->seqno + inpkt->len)) {
                        logger(DEBUG_TRAFFIC, LOG_DEBUG, "Got unauthenticated packet from %s (%s)", n->name, n->hostname);
-                       return;
+                       return false;
                }
        }
        /* Decrypt the packet */
 
-       if(cipher_active(&n->incipher)) {
-               outpkt = pkt[nextpkt++];
+       if(cipher_active(n->incipher)) {
+               vpn_packet_t *outpkt = pkt[nextpkt++];
                outlen = MAXSIZE;
 
-               if(!cipher_decrypt(&n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
+               if(!cipher_decrypt(n->incipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
                        logger(DEBUG_TRAFFIC, LOG_DEBUG, "Error decrypting packet from %s (%s)", n->name, n->hostname);
-                       return;
+                       return false;
                }
 
                outpkt->len = outlen;
@@ -333,37 +419,37 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
        /* Check the sequence number */
 
        inpkt->len -= sizeof inpkt->seqno;
-       inpkt->seqno = ntohl(inpkt->seqno);
+       uint32_t seqno = ntohl(inpkt->seqno);
 
        if(replaywin) {
-               if(inpkt->seqno != n->received_seqno + 1) {
-                       if(inpkt->seqno >= n->received_seqno + replaywin * 8) {
+               if(seqno != n->received_seqno + 1) {
+                       if(seqno >= n->received_seqno + replaywin * 8) {
                                if(n->farfuture++ < replaywin >> 2) {
                                        logger(DEBUG_ALWAYS, LOG_WARNING, "Packet from %s (%s) is %d seqs in the future, dropped (%u)",
-                                               n->name, n->hostname, inpkt->seqno - n->received_seqno - 1, n->farfuture);
-                                       return;
+                                               n->name, n->hostname, seqno - n->received_seqno - 1, n->farfuture);
+                                       return false;
                                }
                                logger(DEBUG_ALWAYS, LOG_WARNING, "Lost %d packets from %s (%s)",
-                                               inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
+                                               seqno - n->received_seqno - 1, n->name, n->hostname);
                                memset(n->late, 0, replaywin);
-                       } else if (inpkt->seqno <= n->received_seqno) {
-                               if((n->received_seqno >= replaywin * 8 && inpkt->seqno <= n->received_seqno - replaywin * 8) || !(n->late[(inpkt->seqno / 8) % replaywin] & (1 << inpkt->seqno % 8))) {
+                       } else if (seqno <= n->received_seqno) {
+                               if((n->received_seqno >= replaywin * 8 && seqno <= n->received_seqno - replaywin * 8) || !(n->late[(seqno / 8) % replaywin] & (1 << seqno % 8))) {
                                        logger(DEBUG_ALWAYS, LOG_WARNING, "Got late or replayed packet from %s (%s), seqno %d, last received %d",
-                                               n->name, n->hostname, inpkt->seqno, n->received_seqno);
-                                       return;
+                                               n->name, n->hostname, seqno, n->received_seqno);
+                                       return false;
                                }
                        } else {
-                               for(int i = n->received_seqno + 1; i < inpkt->seqno; i++)
+                               for(int i = n->received_seqno + 1; i < seqno; i++)
                                        n->late[(i / 8) % replaywin] |= 1 << i % 8;
                        }
                }
 
                n->farfuture = 0;
-               n->late[(inpkt->seqno / 8) % replaywin] &= ~(1 << inpkt->seqno % 8);
+               n->late[(seqno / 8) % replaywin] &= ~(1 << seqno % 8);
        }
 
-       if(inpkt->seqno > n->received_seqno)
-               n->received_seqno = inpkt->seqno;
+       if(seqno > n->received_seqno)
+               n->received_seqno = seqno;
 
        n->received++;
 
@@ -375,12 +461,12 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
        length_t origlen = inpkt->len;
 
        if(n->incompression) {
-               outpkt = pkt[nextpkt++];
+               vpn_packet_t *outpkt = pkt[nextpkt++];
 
                if((outpkt->len = uncompress_packet(outpkt->data, inpkt->data, inpkt->len, n->incompression)) < 0) {
                        logger(DEBUG_TRAFFIC, LOG_ERR, "Error while uncompressing packet from %s (%s)",
                                                 n->name, n->hostname);
-                       return;
+                       return false;
                }
 
                inpkt = outpkt;
@@ -394,11 +480,15 @@ static void receive_udppacket(node_t *n, vpn_packet_t *inpkt) {
                mtu_probe_h(n, inpkt, origlen);
        else
                receive_packet(n, inpkt);
+       return true;
 }
 
 void receive_tcppacket(connection_t *c, const char *buffer, int len) {
        vpn_packet_t outpkt;
 
+       if(len > sizeof outpkt.data)
+               return;
+
        outpkt.len = len;
        if(c->options & OPTION_TCPONLY)
                outpkt.priority = 0;
@@ -409,19 +499,27 @@ void receive_tcppacket(connection_t *c, const char *buffer, int len) {
        receive_packet(c->node, &outpkt);
 }
 
+static bool try_sptps(node_t *n) {
+       if(n->status.validkey)
+               return true;
+
+       logger(DEBUG_TRAFFIC, LOG_INFO, "No valid key known yet for %s (%s)", n->name, n->hostname);
+
+       if(!n->status.waitingforkey)
+               send_req_key(n);
+       else if(n->last_req_key + 10 < now.tv_sec) {
+               logger(DEBUG_ALWAYS, LOG_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
+               sptps_stop(&n->sptps);
+               n->status.waitingforkey = false;
+               send_req_key(n);
+       }
+
+       return false;
+}
+
 static void send_sptps_packet(node_t *n, vpn_packet_t *origpkt) {
-       if(!n->status.validkey) {
-               logger(DEBUG_TRAFFIC, LOG_INFO, "No valid key known yet for %s (%s)", n->name, n->hostname);
-               if(!n->status.waitingforkey)
-                       send_req_key(n);
-               else if(n->last_req_key + 10 < time(NULL)) {
-                       logger(DEBUG_ALWAYS, LOG_DEBUG, "No key from %s after 10 seconds, restarting SPTPS", n->name);
-                       sptps_stop(&n->sptps);
-                       n->status.waitingforkey = false;
-                       send_req_key(n);
-               }
+       if (!try_sptps(n))
                return;
-       }
 
        uint8_t type = 0;
        int offset = 0;
@@ -456,6 +554,18 @@ static void send_sptps_packet(node_t *n, vpn_packet_t *origpkt) {
        return;
 }
 
+static void adapt_socket(const sockaddr_t *sa, int *sock) {
+       /* Make sure we have a suitable socket for the chosen address */
+       if(listen_socket[*sock].sa.sa.sa_family != sa->sa.sa_family) {
+               for(int i = 0; i < listen_sockets; i++) {
+                       if(listen_socket[i].sa.sa.sa_family == sa->sa.sa_family) {
+                               *sock = i;
+                               break;
+                       }
+               }
+       }
+}
+
 static void choose_udp_address(const node_t *n, const sockaddr_t **sa, int *sock) {
        /* Latest guess */
        *sa = &n->address;
@@ -494,43 +604,29 @@ static void choose_udp_address(const node_t *n, const sockaddr_t **sa, int *sock
                *sock = rand() % listen_sockets;
        }
 
-       /* Make sure we have a suitable socket for the chosen address */
-       if(listen_socket[*sock].sa.sa.sa_family != (*sa)->sa.sa_family) {
-               for(int i = 0; i < listen_sockets; i++) {
-                       if(listen_socket[i].sa.sa.sa_family == (*sa)->sa.sa_family) {
-                               *sock = i;
-                               break;
-                       }
-               }
-       }
+       adapt_socket(*sa, sock);
 }
 
-static void choose_broadcast_address(const node_t *n, const sockaddr_t **sa, int *sock) {
-       static sockaddr_t broadcast_ipv4 = {
-               .in = {
-                       .sin_family = AF_INET,
-                       .sin_addr.s_addr = -1,
-               }
-       };
+static void choose_local_address(const node_t *n, const sockaddr_t **sa, int *sock) {
+       *sa = NULL;
 
-       static sockaddr_t broadcast_ipv6 = {
-               .in6 = {
-                       .sin6_family = AF_INET6,
-                       .sin6_addr.s6_addr[0x0] = 0xff,
-                       .sin6_addr.s6_addr[0x1] = 0x02,
-                       .sin6_addr.s6_addr[0xf] = 0x01,
-               }
-       };
+       /* Pick one of the edges from this node at random, then use its local address. */
 
-       *sock = rand() % listen_sockets;
+       int i = 0;
+       int j = rand() % n->edge_tree->count;
+       edge_t *candidate = NULL;
 
-       if(listen_socket[*sock].sa.sa.sa_family == AF_INET6) {
-               broadcast_ipv6.in6.sin6_port = n->prevedge->address.in.sin_port;
-               broadcast_ipv6.in6.sin6_scope_id = listen_socket[*sock].sa.in6.sin6_scope_id;
-               *sa = &broadcast_ipv6;
-       } else {
-               broadcast_ipv4.in.sin_port = n->prevedge->address.in.sin_port;
-               *sa = &broadcast_ipv4;
+       for splay_each(edge_t, e, n->edge_tree) {
+               if(i++ == j) {
+                       candidate = e;
+                       break;
+               }
+       }
+
+       if (candidate && candidate->local_address.sa.sa_family) {
+               *sa = &candidate->local_address;
+               *sock = rand() % listen_sockets;
+               adapt_socket(*sa, sock);
        }
 }
 
@@ -544,8 +640,8 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
        size_t outlen;
 #if defined(SOL_IP) && defined(IP_TOS)
        static int priority = 0;
-#endif
        int origpriority = origpkt->priority;
+#endif
 
        if(!n->status.reachable) {
                logger(DEBUG_TRAFFIC, LOG_INFO, "Trying to send UDP packet to unreachable node %s (%s)", n->name, n->hostname);
@@ -606,11 +702,11 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 
        /* Encrypt the packet */
 
-       if(cipher_active(&n->outcipher)) {
+       if(cipher_active(n->outcipher)) {
                outpkt = pkt[nextpkt++];
                outlen = MAXSIZE;
 
-               if(!cipher_encrypt(&n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
+               if(!cipher_encrypt(n->outcipher, &inpkt->seqno, inpkt->len, &outpkt->seqno, &outlen, true)) {
                        logger(DEBUG_TRAFFIC, LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
                        goto end;
                }
@@ -621,21 +717,23 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
 
        /* Add the message authentication code */
 
-       if(digest_active(&n->outdigest)) {
-               digest_create(&n->outdigest, &inpkt->seqno, inpkt->len, (char *)&inpkt->seqno + inpkt->len);
-               inpkt->len += digest_length(&n->outdigest);
+       if(digest_active(n->outdigest)) {
+               if(!digest_create(n->outdigest, &inpkt->seqno, inpkt->len, &inpkt->seqno + inpkt->len)) {
+                       logger(DEBUG_TRAFFIC, LOG_ERR, "Error while encrypting packet to %s (%s)", n->name, n->hostname);
+                       goto end;
+               }
+
+               inpkt->len += digest_length(n->outdigest);
        }
 
        /* Send the packet */
 
-       const sockaddr_t *sa;
+       const sockaddr_t *sa = NULL;
        int sock;
 
-       /* Overloaded use of priority field: -1 means local broadcast */
-
-       if(origpriority == -1 && n->prevedge)
-               choose_broadcast_address(n, &sa, &sock);
-       else
+       if(n->status.send_locally)
+               choose_local_address(n, &sa, &sock);
+       if(!sa)
                choose_udp_address(n, &sa, &sock);
 
 #if defined(SOL_IP) && defined(IP_TOS)
@@ -644,11 +742,11 @@ static void send_udppacket(node_t *n, vpn_packet_t *origpkt) {
                priority = origpriority;
                logger(DEBUG_TRAFFIC, LOG_DEBUG, "Setting outgoing packet priority to %d", priority);
                if(setsockopt(listen_socket[n->sock].udp.fd, SOL_IP, IP_TOS, &priority, sizeof(priority))) /* SO_PRIORITY doesn't seem to work */
-                       logger(DEBUG_ALWAYS, LOG_ERR, "System call `%s' failed: %s", "setsockopt", strerror(errno));
+                       logger(DEBUG_ALWAYS, LOG_ERR, "System call `%s' failed: %s", "setsockopt", sockstrerror(sockerrno));
        }
 #endif
 
-       if(sendto(listen_socket[sock].udp.fd, (char *) &inpkt->seqno, inpkt->len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
+       if(sendto(listen_socket[sock].udp.fd, &inpkt->seqno, inpkt->len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
                if(sockmsgsize(sockerrno)) {
                        if(n->maxmtu >= origlen)
                                n->maxmtu = origlen - 1;
@@ -662,37 +760,67 @@ end:
        origpkt->len = origlen;
 }
 
-bool send_sptps_data(void *handle, uint8_t type, const char *data, size_t len) {
-       node_t *to = handle;
+static bool send_sptps_data_priv(node_t *to, node_t *from, int type, const void *data, size_t len) {
+       node_t *relay = (to->via != myself && (type == PKT_PROBE || (len - SPTPS_DATAGRAM_OVERHEAD) <= to->via->minmtu)) ? to->via : to->nexthop;
+       bool direct = from == myself && to == relay;
+       bool relay_supported = (relay->options >> 24) >= 4;
+       bool tcponly = (myself->options | relay->options) & OPTION_TCPONLY;
+
+       /* We don't really need the relay's key, but we need to establish a UDP tunnel with it and discover its MTU. */
+       if (!direct && relay_supported && !tcponly)
+               try_sptps(relay);
 
-       /* Send it via TCP if it is a handshake packet, TCPOnly is in use, or this packet is larger than the MTU. */
+       /* Send it via TCP if it is a handshake packet, TCPOnly is in use, this is a relay packet that the other node cannot understand, or this packet is larger than the MTU.
+          TODO: When relaying, the original sender does not know the end-to-end PMTU (it only knows the PMTU of the first hop).
+                This can lead to scenarios where large packets are sent over UDP to relay, but then relay has no choice but fall back to TCP. */
 
-       if(type >= SPTPS_HANDSHAKE || ((myself->options | to->options) & OPTION_TCPONLY) || (type != PKT_PROBE && len > to->minmtu)) {
+       if(type == SPTPS_HANDSHAKE || tcponly || (!direct && !relay_supported) || (type != PKT_PROBE && (len - SPTPS_DATAGRAM_OVERHEAD) > relay->minmtu)) {
                char buf[len * 4 / 3 + 5];
                b64encode(data, buf, len);
                /* If no valid key is known yet, send the packets using ANS_KEY requests,
                   to ensure we get to learn the reflexive UDP address. */
-               if(!to->status.validkey)
-                       return send_request(to->nexthop->connection, "%d %s %s %s -1 -1 -1 %d", ANS_KEY, myself->name, to->name, buf, myself->incompression);
-               else
-                       return send_request(to->nexthop->connection, "%d %s %s %d %s", REQ_KEY, myself->name, to->name, REQ_SPTPS, buf);
+               if(from == myself && !to->status.validkey) {
+                       to->incompression = myself->incompression;
+                       return send_request(to->nexthop->connection, "%d %s %s %s -1 -1 -1 %d", ANS_KEY, from->name, to->name, buf, to->incompression);
+               } else {
+                       return send_request(to->nexthop->connection, "%d %s %s %d %s", REQ_KEY, from->name, to->name, REQ_SPTPS, buf);
+               }
        }
 
-       /* Otherwise, send the packet via UDP */
-
-       const sockaddr_t *sa;
-       int sock;
+       size_t overhead = 0;
+       if(relay_supported) overhead += sizeof to->id + sizeof from->id;
+       char buf[len + overhead]; char* buf_ptr = buf;
+       if(relay_supported) {
+               if(direct) {
+                       /* Inform the recipient that this packet was sent directly. */
+                       node_id_t nullid = {};
+                       memcpy(buf_ptr, &nullid, sizeof nullid); buf_ptr += sizeof nullid;
+               } else {
+                       memcpy(buf_ptr, &to->id, sizeof to->id); buf_ptr += sizeof to->id;
+               }
+               memcpy(buf_ptr, &from->id, sizeof from->id); buf_ptr += sizeof from->id;
 
-       choose_udp_address(to, &sa, &sock);
+       }
+       /* TODO: if this copy turns out to be a performance concern, change sptps_send_record() to add some "pre-padding" to the buffer and use that instead */
+       memcpy(buf_ptr, data, len); buf_ptr += len;
 
-       if(sendto(listen_socket[sock].udp.fd, data, len, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
+       const sockaddr_t *sa = NULL;
+       int sock;
+       if(relay->status.send_locally)
+               choose_local_address(relay, &sa, &sock);
+       if(!sa)
+               choose_udp_address(relay, &sa, &sock);
+       logger(DEBUG_TRAFFIC, LOG_INFO, "Sending packet from %s (%s) to %s (%s) via %s (%s)", from->name, from->hostname, to->name, to->hostname, relay->name, relay->hostname);
+       if(sendto(listen_socket[sock].udp.fd, buf, buf_ptr - buf, 0, &sa->sa, SALEN(sa->sa)) < 0 && !sockwouldblock(sockerrno)) {
                if(sockmsgsize(sockerrno)) {
-                       if(to->maxmtu >= len)
-                               to->maxmtu = len - 1;
-                       if(to->mtu >= len)
-                               to->mtu = len - 1;
+                       // Compensate for SPTPS overhead
+                       len -= SPTPS_DATAGRAM_OVERHEAD;
+                       if(relay->maxmtu >= len)
+                               relay->maxmtu = len - 1;
+                       if(relay->mtu >= len)
+                               relay->mtu = len - 1;
                } else {
-                       logger(DEBUG_TRAFFIC, LOG_WARNING, "Error sending UDP SPTPS packet to %s (%s): %s", to->name, to->hostname, sockstrerror(sockerrno));
+                       logger(DEBUG_TRAFFIC, LOG_WARNING, "Error sending UDP SPTPS packet to %s (%s): %s", relay->name, relay->hostname, sockstrerror(sockerrno));
                        return false;
                }
        }
@@ -700,6 +828,10 @@ bool send_sptps_data(void *handle, uint8_t type, const char *data, size_t len) {
        return true;
 }
 
+bool send_sptps_data(void *handle, uint8_t type, const char *data, size_t len) {
+       return send_sptps_data_priv(handle, myself, type, data, len);
+}
+
 bool receive_sptps_record(void *handle, uint8_t type, const char *data, uint16_t len) {
        node_t *from = handle;
 
@@ -843,7 +975,7 @@ void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
                // usually distributes the sending of broadcast packets over all nodes.
                case BMODE_MST:
                        for list_each(connection_t, c, connection_list)
-                               if(c->status.active && c->status.mst && c != from->nexthop->connection)
+                               if(c->edge && c->status.mst && c != from->nexthop->connection)
                                        send_packet(c->node, packet);
                        break;
 
@@ -855,7 +987,7 @@ void broadcast_packet(const node_t *from, vpn_packet_t *packet) {
                                break;
 
                        for splay_each(node_t, n, node_tree)
-                               if(n->status.reachable && ((n->via == myself && n->nexthop == n) || n->via == n))
+                               if(n->status.reachable && n != myself && ((n->via == myself && n->nexthop == n) || n->via == n))
                                        send_packet(n, packet);
                        break;
 
@@ -896,13 +1028,15 @@ static node_t *try_harder(const sockaddr_t *from, const vpn_packet_t *pkt) {
 void handle_incoming_vpn_data(void *data, int flags) {
        listen_socket_t *ls = data;
        vpn_packet_t pkt;
+       sptps_packet_t *spkt = (sptps_packet_t *)&pkt;
        char *hostname;
-       sockaddr_t from = {{0}};
-       socklen_t fromlen = sizeof from;
-       node_t *n;
-       int len;
+       node_id_t nullid = {};
+       sockaddr_t addr = {};
+       socklen_t addrlen = sizeof addr;
+       node_t *from, *to;
+       bool direct = false;
 
-       len = recvfrom(ls->udp.fd, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);
+       int len = recvfrom(ls->udp.fd, &pkt.seqno, MAXSIZE, 0, &addr.sa, &addrlen);
 
        if(len <= 0 || len > MAXSIZE) {
                if(!sockwouldblock(sockerrno))
@@ -912,27 +1046,66 @@ void handle_incoming_vpn_data(void *data, int flags) {
 
        pkt.len = len;
 
-       sockaddrunmap(&from); /* Some braindead IPv6 implementations do stupid things. */
+       sockaddrunmap(&addr); /* Some braindead IPv6 implementations do stupid things. */
+
+       // Try to figure out who sent this packet.
 
-       n = lookup_node_udp(&from);
+       node_t *n = lookup_node_udp(&addr);
 
        if(!n) {
-               n = try_harder(&from, &pkt);
-               if(n)
-                       update_node_udp(n, &from);
-               else if(debug_level >= DEBUG_PROTOCOL) {
-                       hostname = sockaddr2hostname(&from);
+               // It might be from a 1.1 node, which might have a source ID in the packet.
+               from = lookup_node_id(&spkt->srcid);
+               if(from && !memcmp(&spkt->dstid, &nullid, sizeof nullid) && from->status.sptps) {
+                       if(sptps_verify_datagram(&from->sptps, spkt->data, spkt->len - sizeof(spkt->srcid) - sizeof(spkt->dstid)))
+                               n = from;
+                       else
+                               goto skip_harder;
+               }
+       }
+
+       if(!n)
+               n = try_harder(&addr, &pkt);
+
+skip_harder:
+       if(!n) {
+               if(debug_level >= DEBUG_PROTOCOL) {
+                       hostname = sockaddr2hostname(&addr);
                        logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from unknown source %s", hostname);
                        free(hostname);
+               }
+               return;
+       }
+
+       if(n->status.sptps) {
+               if(!memcmp(&spkt->dstid, &nullid, sizeof nullid)) {
+                       direct = true;
+                       from = n;
+                       to = myself;
+               } else {
+                       from = lookup_node_id(&spkt->srcid);
+                       to = lookup_node_id(&spkt->dstid);
+               }
+               if(!from || !to) {
+                       logger(DEBUG_PROTOCOL, LOG_WARNING, "Received UDP packet from %s (%s) with unknown source and/or destination ID", n->name, n->hostname);
                        return;
                }
-               else
+
+               spkt->len -= sizeof spkt->dstid + sizeof spkt->srcid;
+               if(to != myself) {
+                       send_sptps_data_priv(to, n, 0, spkt->data, spkt->len);
                        return;
+               }
+       } else {
+               direct = true;
+               from = n;
        }
 
-       n->sock = ls - listen_socket;
+       if(!receive_udppacket(from, &pkt))
+               return;
 
-       receive_udppacket(n, &pkt);
+       n->sock = ls - listen_socket;
+       if(direct && sockaddrcmp(&addr, &n->address))
+               update_node_udp(n, &addr);
 }
 
 void handle_device_data(void *data, int flags) {