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60 lines
2.5 KiB
C
60 lines
2.5 KiB
C
#include "mphlr.h"
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int overlay_add_selfannouncement(int interface,overlay_buffer *b)
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{
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/* Pull the first record from the HLR database and turn it into a
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self-announcment. These are shorter than regular Subscriber Observation
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Notices (SON) because they are just single-hop announcments of presence.
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Do we really need to push the whole SID (32 bytes), or will just, say,
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8 do so that we use a prefix of the SID which is still very hard to forge?
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A hearer of a self-announcement who has not previously seen the sender might
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like to get some authentication to prevent naughty people from spoofing routes.
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We can do this by having ourselves, the sender, keep track of the last few frames
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we have sent, so that we can be asked to sign them. Actually, we won't sign them,
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as that is too slow/energy intensive, but we could use a D-H exchange with the neighbour,
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performed once to get a shared secret that can be used to feed a stream cipher to
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produce some sort of verification.
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XXX - But this functionality really needs to move up a level to whole frame composition.
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*/
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unsigned char c;
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int zero=0;
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/* Make sure we can find our SID */
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if (!findHlr(hlr,&zero,NULL,NULL)) return WHY("Could not find first entry in HLR");
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/* Header byte */
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c=OF_SELFANNOUNCE;
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if (ob_append_bytes(b,&c,1))
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return WHY("ob_append_bytes() could not add self-announcement header");
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/* Add our SID to the announcement */
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if (ob_append_bytes(b,&hlr[zero+4],SID_SIZE)) return WHY("Could not append SID to self-announcement");
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/* A sequence number, so that others can keep track of their reception of our frames.
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These are per-interface */
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if (ob_append_int(b,overlay_interfaces[interface].sequence_number))
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return WHY("ob_append_int() could not add sequence number to self-announcement");
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/* A TTL for this frame?
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XXX - BATMAN uses various TTLs, but I think that it may just be better to have all TTL=1,
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and have the onward nodes selectively choose which nodes to on-announce. If we prioritise
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newly arrived nodes somewhat (or at least reserve some slots for them), then we can still
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get the good news travels fast property of BATMAN, but without having to flood in the formal
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sense. */
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c=1;
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if (ob_append_bytes(b,&c,1))
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return WHY("ob_append_bytes() could not add TTL to self-announcement");
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return 0;
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}
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int overlay_get_nexthop(overlay_payload *p,unsigned char *nexthop,int *nexthoplen)
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{
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return WHY("Not implemented");
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}
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