diff --git a/core/net/mac/csma.c b/core/net/mac/csma.c index de966cce6..45b8a1d6b 100644 --- a/core/net/mac/csma.c +++ b/core/net/mac/csma.c @@ -28,7 +28,7 @@ * * This file is part of the Contiki operating system. * - * $Id: csma.c,v 1.13 2010/03/09 13:23:58 adamdunkels Exp $ + * $Id: csma.c,v 1.14 2010/03/09 20:38:55 adamdunkels Exp $ */ /** @@ -38,8 +38,6 @@ * Adam Dunkels */ -#define CSMA_CONF_REXMIT 1 - #include "net/mac/csma.h" #include "net/rime/packetbuf.h" #include "net/rime/queuebuf.h" @@ -75,18 +73,27 @@ struct queued_packet { #define MAX_QUEUED_PACKETS 8 MEMB(packet_memb, struct queued_packet, MAX_QUEUED_PACKETS); +static void packet_sent(void *ptr, int status, int num_transmissions); /*---------------------------------------------------------------------------*/ -#if CSMA_CONF_REXMIT +static void +retransmit_packet(void *ptr) +{ + struct queued_packet *q = ptr; + + queuebuf_to_packetbuf(q->buf); + PRINTF("csma: resending number %d\n", q->transmissions); + NETSTACK_RDC.send(packet_sent, q); +} +/*---------------------------------------------------------------------------*/ static void free_packet(struct queued_packet *q) { queuebuf_free(q->buf); memb_free(&packet_memb, q); + ctimer_stop(&q->retransmit_timer); } - -static void retransmit_packet(void *ptr); - +/*---------------------------------------------------------------------------*/ static void packet_sent(void *ptr, int status, int num_transmissions) { @@ -115,6 +122,10 @@ packet_sent(void *ptr, int status, int num_transmissions) if(status == MAC_TX_COLLISION || status == MAC_TX_NOACK) { + + /* If the transmission was not performed because of a collision or + noack, we must retransmit the packet. */ + switch(status) { case MAC_TX_COLLISION: PRINTF("csma: rexmit collision %d\n", q->transmissions); @@ -122,17 +133,28 @@ packet_sent(void *ptr, int status, int num_transmissions) case MAC_TX_NOACK: PRINTF("csma: rexmit noack %d\n", q->transmissions); break; - default: - PRINTF("csma: rexmit err %d, %d\n", status, q->transmissions); + default: + PRINTF("csma: rexmit err %d, %d\n", status, q->transmissions); } - + + /* The retransmission time must be proportional to the channel + check interval of the underlying radio duty cycling layer. */ time = NETSTACK_RDC.channel_check_interval(); + + /* If the radio duty cycle has no channel check interval (i.e., it + does not turn the radio off), we make the retransmission time + proportional to one second. */ if(time == 0) { time = CLOCK_SECOND; } - time = time + (random_rand() % (q->transmissions * 3 * time)); + + /* The retransmission time uses a linear backoff so that the + interval between the transmissions increase with each + retransmit. */ + time = time + (random_rand() % ((q->collisions + q->transmissions) * 3 * time)); if(q->transmissions < q->max_transmissions) { + PRINTF("csma: retransmitting with time %lu\n", time); ctimer_set(&q->retransmit_timer, time, retransmit_packet, q); } else { @@ -140,94 +162,8 @@ packet_sent(void *ptr, int status, int num_transmissions) free_packet(q); mac_call_sent_callback(sent, cptr, status, num_tx); } - } else { - if(status == MAC_TX_OK) { - PRINTF("csma: rexmit ok %d\n", q->transmissions); - } else { - PRINTF("csma: rexmit err %d %d\n", status, q->transmissions); - } - free_packet(q); - mac_call_sent_callback(sent, cptr, status, num_tx); - } -} - -static void -retransmit_packet(void *ptr) -{ - struct queued_packet *q = ptr; - - queuebuf_to_packetbuf(q->buf); - PRINTF("csma: resending number %d\n", q->transmissions); - NETSTACK_RDC.send(packet_sent, q); -} -/*---------------------------------------------------------------------------*/ -static void -sent_packet(void *ptr, int status, int num_transmissions) -{ - struct queued_packet *q = ptr; - clock_time_t time; - rimeaddr_t receiver; - - rimeaddr_copy(&receiver, packetbuf_addr(PACKETBUF_ADDR_RECEIVER)); - - if(rimeaddr_cmp(&receiver, &rimeaddr_null)) { - PRINTF("broadcast/"); - } - if(status != MAC_TX_OK) { - switch(status) { - case MAC_TX_COLLISION: - PRINTF("csma 1: collision\n"); - break; - case MAC_TX_NOACK: - PRINTF("csma 1: noack\n"); - break; - default: - PRINTF("csma 1: err %d\n", status); - } - } else { - PRINTF("csma 1: ok\n"); - } - - switch(status) { - case MAC_TX_OK: - case MAC_TX_NOACK: - q->transmissions++; - break; - case MAC_TX_COLLISION: - q->collisions++; - break; - case MAC_TX_DEFERRED: - q->deferrals++; - break; - } - - /* Check if we saw a collission, and if we have a queuebuf with the - packet available. Only retransmit unicast packets. Retransmit - only once, for now. */ - if((status == MAC_TX_COLLISION || status == MAC_TX_NOACK) && - !rimeaddr_cmp(&receiver, &rimeaddr_null)) { - /* If the packet couldn't be sent because of a collision or the - lack of an ACK, we let the other transmissions get through - before we try again. */ - if(status == MAC_TX_COLLISION) { - q->collisions++; - } - time = NETSTACK_RDC.channel_check_interval(); - if(time == 0) { - time = CLOCK_SECOND; - } - time = time + (random_rand() % (3 * time)); - - ctimer_set(&q->retransmit_timer, time, - retransmit_packet, q); - } else { - mac_callback_t sent; - void *cptr; - int num_tx; - - sent = q->sent; - cptr = q->cptr; - num_tx = q->transmissions - q->collisions; + } else if(status == MAC_TX_OK) { + PRINTF("csma: rexmit ok %d\n", q->transmissions); free_packet(q); mac_call_sent_callback(sent, cptr, status, num_tx); } @@ -249,7 +185,7 @@ send_packet(mac_callback_t sent, void *ptr) q->deferrals = 0; q->sent = sent; q->cptr = ptr; - NETSTACK_RDC.send(sent_packet, q); + NETSTACK_RDC.send(packet_sent, q); return; } memb_free(&packet_memb, q); @@ -257,13 +193,6 @@ send_packet(mac_callback_t sent, void *ptr) PRINTF("csma: could not allocate queuebuf, will drop if collision or noack\n"); NETSTACK_RDC.send(sent, ptr); } -#else /* CSMA_CONF_REXMIT */ -static void -send_packet(mac_callback_t sent, void *ptr) -{ - NETSTACK_RDC.send(sent, ptr); -} -#endif /* CSMA_CONF_REXMIT */ /*---------------------------------------------------------------------------*/ static void input_packet(void)