added file I forgot to add previously.

This commit is contained in:
gardners 2012-01-12 14:08:54 +10:30
parent abb3021986
commit aeff9a4682

90
overlay_broadcast.c Normal file
View File

@ -0,0 +1,90 @@
/*
Serval Distributed Numbering Architecture (DNA)
Copyright (C) 2010 Paul Gardner-Stephen
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
*/
/*
Smart-flooding of broadcast information is also a requirement. The long addresses help here, as we can make any address that begins
with the first 192 bits all ones be broadcast, and use the remaining 64 bits as a "broadcast packet identifier" (BPI).
Nodes can remember recently seen BPIs and not forward broadcast frames that have been seen recently. This should get us smart flooding
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
since for things like number resolution we are happy to send repeat requests.
*/
#include "mphlr.h"
/* Determine if an address is broadcast */
int overlay_address_is_broadcast(unsigned char *a)
{
int i;
for(i=0;i<(SID_SIZE-8);i++)
if (a[i]!=0xff) return 0;
return 1;
}
int overlay_broadcast_generate_address(unsigned char *a)
{
int i;
for(i=0;i<(SID_SIZE-8);i++) a[i]=0xff;
for(;i<SID_SIZE;i++) a[i]=random()&0xff;
return 0;
}
#define MAX_BPIS 1024
#define BPI_MASK 0x3ff
unsigned char bpilist[MAX_BPIS][8];
int overlay_broadcast_drop_check(unsigned char *a)
{
/* Don't drop frames to non-broadcast addresses */
if (!overlay_address_is_broadcast(a)) return 0;
/* Hash the BPI and see if we have seen it recently.
If so, drop the frame.
The occassional failure to supress a broadcast frame is not
something we are going to worry about just yet. For byzantine
robustness it is however required. */
int bpi_index=0;
int i;
for(i=0;i<8;i++)
{
bpi_index=((bpi_index<<3)&0xfff8)+((bpi_index>>13)&0x7);
bpi_index^=a[24+i];
}
bpi_index&=BPI_MASK;
if (debug&DEBUG_BROADCASTS)
fprintf(stderr,"BPI %02X%02X%02X%02X%02X%02X%02X%02X resolves to hash bin %d\n",
a[24],a[25],a[26],a[27],a[28],a[29],a[30],a[31],bpi_index);
int bpiNew=0;
for(i=0;i<8;i++)
{
if (a[24+i]!=bpilist[bpi_index][i]) bpiNew=1;
bpilist[bpi_index][i]=a[24+i];
}
if (bpiNew)
{
if (debug&DEBUG_BROADCASTS) fprintf(stderr," BPI is new, so don't drop frame.\n");
return 0; /* don't drop */
}
else
{
if (debug&DEBUG_BROADCASTS) fprintf(stderr," BPI is already in our list, so drop the frame to prevent broadcast storms.\n");
return 1; /* drop frame because we have seen this BPI recently */
}
}