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https://github.com/servalproject/serval-dna.git
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Add window size to ACK, ensure only one new degree of freedom per packet
This commit is contained in:
Jeremy Lakeman
parent
8bc4c27ab2
commit
82d9da2171
143
network_coding.c
143
network_coding.c
@ -25,9 +25,13 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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#include <inttypes.h>
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#include <stdarg.h>
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#define FLAG_NEW 1
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#define HEADER_LEN 16
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struct nc_packet{
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uint32_t sequence;
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uint32_t combination;
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uint8_t flags;
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uint8_t *payload;
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};
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@ -96,6 +100,7 @@ struct nc *nc_new(uint32_t max_window_size, uint32_t datagram_size)
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return NULL;
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}
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n->tx.max_queue_size = max_window_size;
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n->tx.window_size = 4;
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n->rx.packets = calloc(sizeof(struct nc_packet)*max_window_size*2,1);
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if (!n->rx.packets){
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free(n->tx.packets);
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@ -142,12 +147,13 @@ int nc_tx_enqueue_datagram(struct nc *n, unsigned char *d, int len)
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n->tx.packets[index].payload = malloc(len);
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n->tx.packets[index].sequence = seq;
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n->tx.packets[index].combination = 0x80000000;
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n->tx.packets[index].flags = FLAG_NEW;
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bcopy(d, n->tx.packets[index].payload, len);
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n->tx.queue_size++;
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return 0;
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}
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static int _nc_get_ack(struct nc_half *n, uint32_t *first_unseen)
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static int _nc_get_ack(struct nc_half *n, uint32_t *first_unseen, uint32_t *window_size)
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{
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uint32_t seq;
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@ -156,15 +162,21 @@ static int _nc_get_ack(struct nc_half *n, uint32_t *first_unseen)
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if (n->packets[index].sequence != seq || !n->packets[index].payload)
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break;
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}
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if (seq > n->deliver_next+16){
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seq = n->deliver_next+16;
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}
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int blocked = seq - (int)n->deliver_next;
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if (blocked>=n->max_queue_size)
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*window_size = 1;
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else
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*window_size = n->max_queue_size - blocked;
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*first_unseen = seq;
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return 0;
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}
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static int _nc_ack(struct nc_half *n, uint32_t first_unseen)
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static int _nc_ack(struct nc_half *n, uint32_t first_unseen, uint32_t window_size)
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{
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if (window_size>n->max_queue_size)
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window_size=n->max_queue_size;
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n->window_size = window_size;
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// ignore invalid input or no new information
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if (first_unseen <= n->window_start ||
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first_unseen > n->window_start + n->queue_size)
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@ -208,29 +220,36 @@ static int _nc_tx_combine_random_payloads(struct nc_half *n, struct nc_packet *p
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// TODO: Check that combination is linearly independent of recently produced
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// combinations, i.e., that it contributes information.
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// get 32 bit random number. random() only returns 31 bits,
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// hence the double call and shift
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uint32_t combination;
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combination=random()^(random()<<1);
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// restrict set bits to only those in the window
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// i.e., zero lower (32-n->window_used) bits
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combination=(combination>>(32-n->queue_size))<<(32-n->queue_size);
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// Never send all zeros, since that conveys no information.
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// (always send the first packet in the window)
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uint32_t combination=1;
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int i;
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// give every other packet about 1/4 chance of being included
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for (i=0;i<8;i++)
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combination|=(1<<(random()&31));
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bzero(packet->payload, n->datagram_size);
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int added_new=0;
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int i;
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for(i=0;i<n->max_queue_size;i++) {
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for(i=0;i<n->window_size;i++) {
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int index = (n->window_start + i) & (n->max_queue_size -1);
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// assume we might have gaps in the payload list if we are a retransmitter in the network path
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if (!n->packets[index].payload)
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continue;
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// always send the first packet in the window
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if ((combination&0x80000000)||n->packets[index].sequence==packet->sequence)
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// there's no point including more than one new packet
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// only if we have some packet loss will we need to send more combinations of packets
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if (n->packets[index].flags & FLAG_NEW){
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if (added_new)
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continue;
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_combine_packets(&n->packets[index], packet, n->datagram_size);
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combination<<=1;
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added_new = 1;
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n->packets[index].flags =0;
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continue;
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}
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if (combination&1)
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_combine_packets(&n->packets[index], packet, n->datagram_size);
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combination>>=1;
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}
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return 0;
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@ -240,26 +259,27 @@ static int _nc_tx_combine_random_payloads(struct nc_half *n, struct nc_packet *p
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int nc_tx_produce_packet(struct nc *n, uint8_t *datagram, uint32_t buffer_size)
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{
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// TODO: Don't waste more bytes than we need to on the bitmap and sequence number
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if (buffer_size < n->tx.datagram_size+12)
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if (buffer_size < n->tx.datagram_size+HEADER_LEN)
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return -1;
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uint32_t unseen;
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if (_nc_get_ack(&n->rx, &unseen))
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uint32_t unseen, window_size;
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if (_nc_get_ack(&n->rx, &unseen, &window_size))
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return -1;
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write_uint32(&datagram[0], unseen);
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write_uint32(&datagram[4], window_size);
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if (!n->tx.queue_size){
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// No data to send, just send an ack
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// TODO don't ack too often
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return 4;
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return 8;
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}
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// Produce linear combination
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struct nc_packet packet={
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.sequence = n->tx.window_start,
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.combination = 0,
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.payload = &datagram[12],
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.payload = &datagram[HEADER_LEN],
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};
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if (_nc_tx_combine_random_payloads(&n->tx, &packet))
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@ -267,9 +287,9 @@ int nc_tx_produce_packet(struct nc *n, uint8_t *datagram, uint32_t buffer_size)
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// TODO assert actual_combination? (should never be zero)
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// Write out bitmap of actual combinations involved
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write_uint32(&datagram[4], packet.sequence);
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write_uint32(&datagram[8], packet.combination);
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return 12+n->tx.datagram_size;
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write_uint32(&datagram[8], packet.sequence);
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write_uint32(&datagram[12], packet.combination);
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return HEADER_LEN+n->tx.datagram_size;
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}
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static int _nc_rx_combine_packet(struct nc_half *n, struct nc_packet *packet)
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@ -350,22 +370,23 @@ static void _nc_rx_advance_window(struct nc_half *n, uint32_t new_window_start)
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int nc_rx_packet(struct nc *n, uint8_t *payload, int len)
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{
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if (len!=4 && len != 12+n->rx.datagram_size)
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if (len!=8 && len != HEADER_LEN+n->rx.datagram_size)
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return -1;
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uint32_t unseen = read_uint32(payload);
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uint32_t window_size = read_uint32(&payload[4]);
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_nc_ack(&n->tx, unseen);
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_nc_ack(&n->tx, unseen, window_size);
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if (len < 12+n->rx.datagram_size){
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if (len < HEADER_LEN+n->rx.datagram_size){
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return 0;
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}
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uint32_t new_window_start = read_uint32(&payload[4]);
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uint32_t new_window_start = read_uint32(&payload[8]);
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struct nc_packet packet={
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.sequence = new_window_start,
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.combination = read_uint32(&payload[8]),
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.payload = &payload[12],
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.combination = read_uint32(&payload[12]),
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.payload = &payload[HEADER_LEN],
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};
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int r = _nc_rx_combine_packet(&n->rx, &packet);
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@ -490,6 +511,7 @@ int nc_test()
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// Prepare some random datagrams for subsequent tests
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int i;
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int sent =0;
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uint8_t datagrams[8][200];
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for (i=0;i<8;i++)
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nc_test_random_datagram(datagrams[i],200);
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@ -501,20 +523,20 @@ int nc_test()
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int j=0;
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for(i=0;i<10;i++) {
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uint8_t outbuffer[12+200];
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uint8_t outbuffer[HEADER_LEN+200];
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int len=sizeof(outbuffer);
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int written = nc_tx_produce_packet(tx, outbuffer, len);
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if (written==-1)
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FAIL("Produce random linear combination of single packet for TX");
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if (i==9)
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PASS("Produce random linear combination of single packet for TX");
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uint32_t combination = read_uint32(&outbuffer[8]);
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uint32_t combination = read_uint32(&outbuffer[12]);
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if (!combination)
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FAIL("Should not produce empty linear combination bitmap");
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if (i==9)
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PASS("Should not produce empty linear combination bitmap");
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if (memcmp(&outbuffer[12], datagrams[0], 200)!=0)
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if (memcmp(&outbuffer[HEADER_LEN], datagrams[0], 200)!=0)
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FAIL("Output identity datagram when only one in queue");
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if (i==9)
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PASS("Output identity datagram when only one in queue");
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@ -554,11 +576,12 @@ int nc_test()
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// now can we receive this first packet?
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{
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uint8_t outbuffer[12+200];
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uint8_t outbuffer[HEADER_LEN+200];
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int written = nc_tx_produce_packet(tx, outbuffer, sizeof(outbuffer));
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ASSERT(written!=-1, "Produce packet");
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int r=nc_rx_packet(rx, outbuffer, written);
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ASSERT(r!=-1, "Receive packet");
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sent ++;
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}
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// can we decode it?
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@ -572,7 +595,7 @@ int nc_test()
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// acknowledging this first packet advances the window
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{
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uint8_t outbuffer[12+200];
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uint8_t outbuffer[HEADER_LEN+200];
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int written = nc_tx_produce_packet(rx, outbuffer, sizeof(outbuffer));
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ASSERT(written!=-1, "Produce ACK");
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int r=nc_rx_packet(tx, outbuffer, written);
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@ -590,14 +613,14 @@ int nc_test()
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int decoded=0;
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for(i=0;i<100;i++) {
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uint8_t outbuffer[12+200];
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uint8_t outbuffer[HEADER_LEN+200];
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int len=sizeof(outbuffer);
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int written = nc_tx_produce_packet(tx, outbuffer, len);
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if (written==-1)
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FAIL("Produce random linear combination of multiple packets for TX");
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if (i==0)
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PASS("Produce random linear combination of multiple packets for TX");
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uint32_t combination = read_uint32(&outbuffer[8]);
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uint32_t combination = read_uint32(&outbuffer[12]);
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if (!combination)
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FAIL("Should not produce empty linear combination bitmap");
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if (i==0)
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@ -605,7 +628,7 @@ int nc_test()
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for(j=0;j<200;j++) {
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int k;
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uint8_t x = outbuffer[12+j];
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uint8_t x = outbuffer[HEADER_LEN+j];
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for (k=0;k<8;k++){
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if (combination&(0x80000000>>k))
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x^=datagrams[k+1][j];
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@ -616,7 +639,9 @@ int nc_test()
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if (i==0)
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PASS("Output linear combination from multiple packets in the queue");
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nc_rx_packet(rx, outbuffer, written);
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if (nc_rx_packet(rx, outbuffer, written)!=1)
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sent ++;
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while(1){
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uint8_t out[200];
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int size = nc_rx_next_delivered(rx, out, sizeof(out));
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@ -635,7 +660,7 @@ int nc_test()
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// acknowledging first 8 packets advances the tx window
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{
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uint8_t outbuffer[12+200];
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uint8_t outbuffer[HEADER_LEN+200];
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int written = nc_tx_produce_packet(rx, outbuffer, sizeof(outbuffer));
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ASSERT(written!=-1, "Produce ACK");
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int r=nc_rx_packet(tx, outbuffer, written);
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@ -644,7 +669,11 @@ int nc_test()
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ASSERT(tx->tx.queue_size==0, "ACK causes packets to be discarded");
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}
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int sent =0;
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int histogram[64];
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int uninteresting=0;
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int dropped=0;
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bzero(histogram, sizeof(histogram));
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while(rx->rx.deliver_next < 10000){
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// fill the transmit window whenever there is space
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while(tx->tx.queue_size<tx->tx.max_queue_size){
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@ -653,17 +682,18 @@ int nc_test()
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}
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// generate a packet in each direction
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uint8_t one[12+200];
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uint8_t two[12+200];
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uint8_t one[HEADER_LEN+200];
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uint8_t two[HEADER_LEN+200];
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sent++;
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int wone = nc_tx_produce_packet(tx, one, sizeof(one));
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int wtwo = nc_tx_produce_packet(rx, two, sizeof(two));
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// receive each packet
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int rone=nc_rx_packet(rx, one, wone);
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if (!(random()&7))
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nc_rx_packet(tx, two, wtwo);
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if (rone!=1){
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if (!(random()&7)){
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if (nc_rx_packet(rx, one, wone)!=1){
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int burst_len=0;
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// deliver anything that can be decoded
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while(1){
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uint8_t out[200];
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@ -671,11 +701,22 @@ int nc_test()
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if (size!=200)
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break;
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decoded++;
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burst_len++;
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}
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}
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histogram[burst_len]++;
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}else
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uninteresting++;
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}else
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dropped++;
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}
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PASS("Delivered 10000 packets after sending %d", sent);
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fprintf(stderr, "Received = %d\n", sent - dropped);
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fprintf(stderr, "Unint = %d\n", uninteresting);
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fprintf(stderr, "Delivery burst histogram;\n");
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for (i=0;i<64;i++)
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if (histogram[i])
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fprintf(stderr, "%d = %d (%d)\n", i, histogram[i], i*histogram[i]);
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nc_free(tx);
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nc_free(rx);
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PASS("Release memory");
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