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https://github.com/servalproject/serval-dna.git
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91 lines
3.1 KiB
C
91 lines
3.1 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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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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*/
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#include "serval.h"
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/* Determine if an address is broadcast */
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int overlay_address_is_broadcast(unsigned char *a)
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{
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int i;
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for(i=0;i<(SID_SIZE-8);i++)
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if (a[i]!=0xff) return 0;
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return 1;
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}
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int overlay_broadcast_generate_address(unsigned char *a)
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{
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int i;
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for(i=0;i<(SID_SIZE-8);i++) a[i]=0xff;
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for(;i<SID_SIZE;i++) a[i]=random()&0xff;
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return 0;
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}
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#define MAX_BPIS 1024
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#define BPI_MASK 0x3ff
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unsigned char bpilist[MAX_BPIS][8];
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int overlay_broadcast_drop_check(unsigned char *a)
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{
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/* Don't drop frames to non-broadcast addresses */
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if (!overlay_address_is_broadcast(a)) return 0;
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/* Hash the BPI and see if we have seen it recently.
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If so, drop the frame.
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The occassional failure to supress a broadcast frame is not
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something we are going to worry about just yet. For byzantine
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robustness it is however required. */
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int bpi_index=0;
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int i;
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for(i=0;i<8;i++)
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{
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bpi_index=((bpi_index<<3)&0xfff8)+((bpi_index>>13)&0x7);
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bpi_index^=a[24+i];
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}
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bpi_index&=BPI_MASK;
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if (debug&DEBUG_BROADCASTS)
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fprintf(stderr,"BPI %02X%02X%02X%02X%02X%02X%02X%02X resolves to hash bin %d\n",
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a[24],a[25],a[26],a[27],a[28],a[29],a[30],a[31],bpi_index);
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int bpiNew=0;
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for(i=0;i<8;i++)
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{
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if (a[24+i]!=bpilist[bpi_index][i]) bpiNew=1;
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bpilist[bpi_index][i]=a[24+i];
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}
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if (bpiNew)
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{
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if (debug&DEBUG_BROADCASTS) fprintf(stderr," BPI is new, so don't drop frame.\n");
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return 0; /* don't drop */
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}
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else
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{
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if (debug&DEBUG_BROADCASTS) fprintf(stderr," BPI is already in our list, so drop the frame to prevent broadcast storms.\n");
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return 1; /* drop frame because we have seen this BPI recently */
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}
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}
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