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aa543e1766
MDP clients can now request the set of local addresses. Framework is improved to avoid info leaks by sending more bytes in an MDP frame than are necessary, but without having to bzero almost 2KB each time.
383 lines
16 KiB
C
383 lines
16 KiB
C
/*
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Serval Distributed Numbering Architecture (DNA)
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Copyright (C) 2010 Paul Gardner-Stephen
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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/*
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Serval Overlay Mesh Network.
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Basically we use UDP broadcast to send link-local, and then implement a BATMAN-like protocol over the top of that.
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Each overlay packet can contain one or more encapsulated packets each addressed using Serval DNA SIDs, with source,
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destination and next-hop addresses.
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The use of an overlay also lets us be a bit clever about using irregular transports, such as an ISM915 modem attached via ethernet
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(which we are planning to build in coming months), by paring off the IP and UDP headers that would otherwise dominate. Even on
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regular WiFi and ethernet we can aggregate packets in a way similar to IAX, but not just for voice frames.
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The use of long (relative to IPv4 or even IPv6) 256 bit Curve25519 addresses means that it is a really good idea to
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have neighbouring nodes exchange lists of peer aliases so that addresses can be summarised, possibly using less space than IPv4
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would have.
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One approach to handle address shortening is to have the periodic TTL=255 BATMAN-style hello packets include an epoch number.
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This epoch number can be used by immediate neighbours of the originator to reference the neighbours listed in that packet by
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their ordinal position in the packet instead of by their full address. This gets us address shortening to 1 byte in most cases
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in return for no new packets, but the periodic hello packets will now be larger. We might deal with this issue by having these
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hello packets reference the previous epoch for common neighbours. Unresolved neighbour addresses could be resolved by a simple
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DNA request, which should only need to occur ocassionally, and other link-local neighbours could sniff and cache the responses
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to avoid duplicated traffic. Indeed, during quiet times nodes could preemptively advertise address resolutions if they wished,
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or similarly advertise the full address of a few (possibly randomly selected) neighbours in each epoch.
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Byzantine Robustness is a goal, so we have to think about all sorts of malicious failure modes.
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One approach to help byzantine robustness is to have multiple signature shells for each hop for mesh topology packets.
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Thus forging a report of closeness requires forging a signature. As such frames are forwarded, the outermost signature
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shell is removed. This is really only needed for more paranoid uses.
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We want to have different traffic classes for voice/video calls versus regular traffic, e.g., MeshMS frames. Thus we need to have
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separate traffic queues for these items. Aside from allowing us to prioritise isochronous data, it also allows us to expire old
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isochronous frames that are in-queue once there is no longer any point delivering them (e.g after holding them more than 200ms).
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We can also be clever about round-robin fair-sharing or even prioritising among isochronous streams. Since we also know about the
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DNA isochronous protocols and the forward error correction and other redundancy measures we also get smart about dropping, say, 1 in 3
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frames from every call if we know that this can be safely done. That is, when traffic is low, we maximise redundancy, and when we
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start to hit the limit of traffic, we start to throw away some of the redundancy. This of course relies on us knowing when the
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network channel is getting too full.
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Smart-flooding of broadcast information is also a requirement. The long addresses help here, as we can make any address that begins
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with the first 192 bits all ones be broadcast, and use the remaining 64 bits as a "broadcast packet identifier" (BPI).
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Nodes can remember recently seen BPIs and not forward broadcast frames that have been seen recently. This should get us smart flooding
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of the majority of a mesh (with some node mobility issues being a factor). We could refine this later, but it will do for now, especially
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since for things like number resolution we are happy to send repeat requests.
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This file currently seems to exist solely to contain this introduction, which is fine with me. Functions land in here until their
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proper place becomes apparent.
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*/
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#include "serval.h"
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int overlayMode=0;
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overlay_txqueue overlay_tx[OQ_MAX];
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int overlayServerMode()
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{
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/* In overlay mode we need to listen to all of our sockets, and also to
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send periodic traffic. This means we need to */
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fprintf(stderr,"Running in overlay mode.\n");
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/* Set default congestion levels for queues */
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int i;
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for(i=0;i<OQ_MAX;i++) {
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overlay_tx[i].maxLength=100;
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overlay_tx[i].latencyTarget=5000; /* Keep packets in queue for 5 seconds by default */
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}
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/* But expire voice/video call packets much sooner, as they just aren't any use if late */
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overlay_tx[OQ_ISOCHRONOUS_VOICE].latencyTarget=500;
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overlay_tx[OQ_ISOCHRONOUS_VIDEO].latencyTarget=500;
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/* Get the set of socket file descriptors we need to monitor.
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Note that end-of-file will trigger select(), so we cannot run select() if we
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have any dummy interfaces running. So we do an ugly hack of just waiting no more than
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5ms between checks if we have a dummy interface running. This is a reasonable simulation
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of wifi latency anyway, so we'll live with it. Larger values will affect voice transport,
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and smaller values would affect CPU and energy use, and make the simulation less realistic. */
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struct pollfd fds[128];
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int fdcount;
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/* Create structures to use 1MB of RAM for testing */
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overlay_route_init(1);
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/* Add all local SIDs to our cache */
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int ofs=0;
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while(findHlr(hlr,&ofs,NULL,NULL)) {
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int i;
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if (debug&DEBUG_OVERLAYINTERFACES) {
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fprintf(stderr,"Adding ");
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for(i=0;i<SID_SIZE;i++) fprintf(stderr,"%02x",hlr[ofs+4+i]);
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fprintf(stderr," to list of local addresses.\n");
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}
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overlay_add_local_identity(&hlr[ofs+4]);
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overlay_abbreviate_cache_address(&hlr[ofs+4]);
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if (nextHlr(hlr,&ofs)) break;
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}
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/* Get rhizome server started BEFORE populating fd list so that
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the server's listen socket is in the list for poll() */
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if (rhizome_datastore_path) rhizome_server_poll();
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while(1) {
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if (servalShutdown) servalShutdownCleanly();
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/* Work out how long we can wait before we need to tick */
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long long ms=overlay_time_until_next_tick();
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memabuseCheck();
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int filesPresent=0;
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fds[0].fd=sock; fds[0].events=POLLIN;
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fdcount=1;
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rhizome_server_get_fds(fds,&fdcount,128);
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rhizome_fetching_get_fds(fds,&fdcount,128);
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overlay_mdp_get_fds(fds,&fdcount,128);
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for(i=0;i<overlay_interface_count;i++)
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{
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/* Make socket non-blocking so that poll() behaves correctly.
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We then set non-blocking before actually reading from it */
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fcntl(overlay_interfaces[i].fd, F_SETFL,
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fcntl(overlay_interfaces[i].fd, F_GETFL, NULL)&(~O_NONBLOCK));
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if ((!overlay_interfaces[i].fileP)&&(fdcount<128))
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{
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if (debug&DEBUG_IO) {
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fprintf(stderr,"Interface %s is poll() slot #%d (fd %d)\n",
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overlay_interfaces[i].name,
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fdcount,
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overlay_interfaces[i].fd);
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}
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fds[fdcount].fd=overlay_interfaces[i].fd;
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fds[fdcount].events=POLLRDNORM;
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fds[fdcount].revents=0;
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fdcount++;
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}
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if (overlay_interfaces[i].fileP)
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{ filesPresent=1; if (ms>5) ms=5; }
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}
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/* Progressively update link scores to neighbours etc, and find out how long before
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we should next tick the route table.
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Basically the faster the CPU and the sparser the route table, the less often we
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will need to tick in order to keep each tick nice and fast. */
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int route_tick_interval=overlay_route_tick();
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if (ms>route_tick_interval) ms=route_tick_interval;
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if (debug&DEBUG_VERBOSE_IO)
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fprintf(stderr,"Waiting via poll() for up to %lldms\n",ms);
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int r=poll(fds,fdcount,ms);
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if (r<0) {
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/* select had a problem */
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if (debug&DEBUG_IO) perror("poll()");
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WHY("select() complained.");
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} else if (r>0) {
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/* We have data, so try to receive it */
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if (debug&DEBUG_IO) {
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fprintf(stderr,"poll() reports %d fds ready\n",r);
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int i;
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for(i=0;i<fdcount;i++) {
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if (fds[i].revents)
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{
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fprintf(stderr," #%d (fd %d): %d (",i,fds[i].fd,fds[i].revents);
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if ((fds[i].revents&POLL_IN)==POLL_IN) fprintf(stderr,"POLL_IN,");
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if ((fds[i].revents&POLLRDNORM)==POLLRDNORM) fprintf(stderr,"POLLRDNORM,");
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if ((fds[i].revents&POLL_OUT)==POLL_OUT) fprintf(stderr,"POLL_OUT,");
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if ((fds[i].revents&POLL_ERR)==POLL_ERR) fprintf(stderr,"POLL_ERR,");
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if ((fds[i].revents&POLL_HUP)==POLL_HUP) fprintf(stderr,"POLL_HUP,");
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if ((fds[i].revents&POLLNVAL)==POLLNVAL) fprintf(stderr,"POLL_NVAL,");
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fprintf(stderr,")\n");
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}
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}
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}
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overlay_rx_messages();
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if (rhizome_datastore_path) {
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rhizome_server_poll();
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rhizome_fetch_poll();
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overlay_mdp_poll();
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}
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} else {
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/* No data before tick occurred, so do nothing.
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Well, for now let's just check anyway. */
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if (debug&DEBUG_IO) fprintf(stderr,"poll() timeout.\n");
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overlay_rx_messages();
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if (rhizome_datastore_path) {
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rhizome_server_poll();
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rhizome_fetch_poll();
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overlay_mdp_poll();
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}
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}
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/* Check if we need to trigger any ticks on any interfaces */
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overlay_check_ticks();
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}
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return 0;
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}
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int overlay_frame_process(int interface,overlay_frame *f)
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{
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if (!f) return WHY("f==NULL");
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long long now=overlay_gettime_ms();
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if (f->source_address_status==OA_RESOLVED&&overlay_address_is_local(f->source))
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return WHY("Dropping frame claiming to come from myself.");
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if (debug&DEBUG_OVERLAYFRAMES) fprintf(stderr,">>> Received frame (type=%02x)\n",f->type);
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/* First order of business is whether the nexthop address has been resolved.
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If not, we need to think about asking for it to be resolved.
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The trouble is that we do not want to trigger a Hanson Event (a storm of
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please explains/resolution requests). Yet, we do not want to delay
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communications unnecessarily.
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The simple solution for now is to queue the address for resolution request
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in our next tick. If we see another resolution request for the same
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address in the mean time, then we can cancel our request */
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switch (f->nexthop_address_status)
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{
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case OA_UNINITIALISED:
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/* Um? Right. */
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return WHY("frame passed with ununitialised nexthop address");
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break;
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case OA_RESOLVED:
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/* Great, we have the address, so we can get on with things */
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break;
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case OA_PLEASEEXPLAIN:
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return WHY("Address cannot be resolved -- aborting packet processing.");
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/* XXX Should send a please explain to get this address resolved. */
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break;
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case OA_UNSUPPORTED:
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default:
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/* If we don't support the address format, we should probably tell
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the sender. Again, we queue this up, and cancel it if someone else
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tells them in the meantime to avoid an Opposition Event (like a Hanson
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Event, but repeatedly berating any node that holds a different policy
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to itself. */
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overlay_interface_repeat_abbreviation_policy[interface]=1;
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return -1;
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break;
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}
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/* Okay, nexthop is valid, so let's see if it is us */
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int forMe=0,i;
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int ultimatelyForMe=0;
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int broadcast=overlay_address_is_broadcast(f->nexthop);
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int duplicateBroadcast=0;
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if (broadcast) {
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if (overlay_broadcast_drop_check(f->destination)) duplicateBroadcast=1;
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forMe=1; }
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if (overlay_address_is_local(f->nexthop)) forMe=1;
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if (forMe) {
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/* It's for us, so resolve the addresses */
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if (overlay_frame_resolve_addresses(interface,f))
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return WHY("Failed to resolve destination and sender addresses in frame");
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if (debug&DEBUG_OVERLAYFRAMES) {
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fprintf(stderr,"Destination for this frame is (resolve code=%d): ",f->destination_address_status);
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if (f->destination_address_status==OA_RESOLVED) for(i=0;i<SID_SIZE;i++) fprintf(stderr,"%02x",f->destination[i]); else fprintf(stderr,"???");
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fprintf(stderr,"\n");
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fprintf(stderr,"Source for this frame is (resolve code=%d): ",f->source_address_status);
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if (f->source_address_status==OA_RESOLVED) for(i=0;i<SID_SIZE;i++) fprintf(stderr,"%02x",f->source[i]); else fprintf(stderr,"???");
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fprintf(stderr,"\n");
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}
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if (f->source_address_status!=OA_RESOLVED) {
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if (debug&DEBUG_OVERLAYFRAMES) WHY("Source address could not be resolved, so dropping frame.");
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return -1;
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}
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if (overlay_address_is_local(f->source))
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{
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if (debug&DEBUG_OVERLAYROUTING)
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WHY("Dropping frame claiming to come from myself.");
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return -1;
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}
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if (f->destination_address_status==OA_RESOLVED) {
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if (overlay_address_is_broadcast(f->destination))
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{ ultimatelyForMe=1; broadcast=1;
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if (overlay_broadcast_drop_check(f->destination)) duplicateBroadcast=1; }
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if (overlay_address_is_local(f->destination)) ultimatelyForMe=1;
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} else {
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if (debug&DEBUG_OVERLAYFRAMES) WHY("Destination address could not be resolved, so dropping frame.");
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return -1;
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}
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}
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if (debug&DEBUG_OVERLAYFRAMES) {
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fprintf(stderr,"This frame does%s have me listed as next hop.\n",forMe?"":" not");
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fprintf(stderr,"This frame is%s for me.\n",ultimatelyForMe?"":" not");
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fprintf(stderr,"This frame is%s broadcast.\n",broadcast?"":" not");
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}
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/* Not for us? Then just ignore it */
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if (!forMe) return 0;
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/* Is this a frame we have to forward on? */
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if (((!ultimatelyForMe)||broadcast)&&(f->ttl>1))
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{
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/* Yes, it is. */
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int len=0;
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if (broadcast&&(!duplicateBroadcast)&&
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((f->type==OF_TYPE_SELFANNOUNCE)
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||(f->type==OF_TYPE_RHIZOME_ADVERT)
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))
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{
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// Don't forward broadcast self-announcement packets as that is O(n^2) with
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// traffic. We have other means to propagating the mesh topology information.
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// Similarly, rhizome advertisement traffic is always link local, so don't
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// forward that either.
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if (debug&DEBUG_BROADCASTS)
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if (duplicateBroadcast)
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fprintf(stderr,"Dropping broadcast frame (BPI seen before)\n");
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} else {
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if (debug&DEBUG_OVERLAYFRAMES) fprintf(stderr,"\nForwarding frame.\n");
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if (overlay_get_nexthop(f->destination,f->nexthop,&len,&f->nexthop_interface))
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return WHY("Could not find next hop for host - dropping frame");
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f->ttl--;
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/* Queue frame for dispatch.
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Don't forget to put packet in the correct queue based on type.
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(e.g., mesh management, voice, video, ordinary or opportunistic). */
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WHY("forwarding of frames not implemented");
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/* If the frame was a broadcast frame, then we need to hang around
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so that we can process it, since we are one of the recipients.
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Otherwise, return triumphant. */
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if (!broadcast) return 0;
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}
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}
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switch(f->type)
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{
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case OF_TYPE_SELFANNOUNCE:
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overlay_route_saw_selfannounce(interface,f,now);
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break;
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case OF_TYPE_SELFANNOUNCE_ACK:
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overlay_route_saw_selfannounce_ack(interface,f,now);
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break;
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case OF_TYPE_NODEANNOUNCE:
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overlay_route_saw_advertisements(interface,f,now);
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break;
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case OF_TYPE_RHIZOME_ADVERT:
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overlay_rhizome_saw_advertisements(interface,f,now);
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break;
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case OF_TYPE_DATA:
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overlay_saw_mdp_containing_frame(interface,f,now);
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break;
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default:
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fprintf(stderr,"Unsupported f->type=0x%x\n",f->type);
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return WHY("Support for that f->type not yet implemented");
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break;
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}
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return 0;
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}
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