aodv中处理处理RREQ分组的流程及协议.doc

第一部分：RREQ分组的处理流程图：第二部分 与流程图对应的程序解析部分：voidAODV:recvRequest(Packet *p) struct hdr_ip *ih = HDR_IP(p);struct hdr_aodv_request *rq = HDR_AODV_REQUEST(p);aodv_rt_entry *rt;/*=*/该分组是否由自己产生 if(rq-rq_src = index) #ifdef DEBUG fprintf(stderr, %s: got my own REQUESTn, _FUNCTION_);#endif / DEBUG/如果是，回收分组 Packet:free(p); return; /如果不是，判断是否已经收到该分组 if (id_lookup(rq-rq_src, rq-rq_bcast_id) #ifdef DEBUG fprintf(stderr, %s: discarding requestn, _FUNCTION_);#endif / DEBUG/如果收到过该分组，回收分组 Packet:free(p); return; /*=*/如果没收到过该分组/将收到的广播分组存入Broadcast ID Cache中 /* * Cache the broadcast ID */ id_insert(rq-rq_src, rq-rq_bcast_id); aodv_rt_entry *rt0; / rt0 is the reverse route /是否存在反向路由项？ rt0 = rtable.rt_lookup(rq-rq_src);/如果不存在反向路由项，新建反向路由 if(rt0 = 0) /* if not in the route table / create an entry for the reverse route. rt0 = rtable.rt_add(rq-rq_src); rt0-rt_expire = max(rt0-rt_expire, (CURRENT_TIME + REV_ROUTE_LIFE);/若存在反向路由项/判断反向路由是否需要更新 ？ if ( (rq-rq_src_seqno rt0-rt_seqno ) | (rq-rq_src_seqno = rt0-rt_seqno) & (rq-rq_hop_count rt_hops) ) /这里就是路由判据，当遇到新的RREQ的时候，比较在路由表中已经存在的到目的节点的路由，比较目的节点的序列号（用来保证使用最新路由防止路由环），在目的节点序列号相同的情况下，采用跳数较小的。在这种情况下就更新路由表。/若需要更新,更新路由表项rt_update(rt0, rq-rq_src_seqno, rq-rq_hop_count, ih-saddr(), max(rt0-rt_expire, (CURRENT_TIME + REV_ROUTE_LIFE) ); if (rt0-rt_req_timeout 0.0) / Reset the soft state and / Set expiry time to CURRENT_TIME + ACTIVE_ROUTE_TIMEOUT / This is because route is used in the forward direction, / but only sources get benefited by this change rt0-rt_req_cnt = 0; rt0-rt_req_timeout = 0.0; rt0-rt_req_last_ttl = rq-rq_hop_count; rt0-rt_expire = CURRENT_TIME + ACTIVE_ROUTE_TIMEOUT; /判断节点是否有发往反向路由目的节点的数据分组，并且路由是否有效 /* Find out whether any buffered packet can benefit from the * reverse route. * May need some change in the following code - Mahesh 09/11/99 */ assert (rt0-rt_flags = RTF_UP);/若有发往反向路由目的节点 的分组 Packet *buffered_pkt; while (buffered_pkt = rqueue.deque(rt0-rt_dst) if (rt0 & (rt0-rt_flags = RTF_UP) /若路由有效assert(rt0-rt_hops != INFINITY2);/将数据分组转发 forward(rt0, buffered_pkt, NO_DELAY); / End for putting reverse route in rt table/*=*/若没有发往反向路由目的节点的数据分组，或者路由无效/或者原来的路由项不需要更新，转发或处理路由请求分组 * We have taken care of the reverse route stuff. * Now see whether we can send a route reply. */* 在这种情况下我们有两种选择，一种是将RREQ继续传播下去，一种是产生RREP。在这之前我们要确定，反向路由已经在路由表中存在。如果存在反向路由，在考虑是否应该想源节点发送RREP */ rt = rtable.rt_lookup(rq-rq_dst);/判断节点本身是路由请求分组的目的地址 if(rq-rq_dst = index) /如果节点本身是目的地址，向源节点发送路由应答分组并且回收请求分组#ifdef DEBUG fprintf(stderr, %d - %s: destination sending replyn, index, _FUNCTION_);#endif / DEBUGseqno = max(seqno, rq-rq_dst_seqno)+1; if (seqno%2) seqno+; sendReply(rq-rq_src, / IP Destination 1, / Hop Count index, / Dest IP Address seqno, / Dest Sequence Num MY_ROUTE_TIMEOUT, / Lifetime rq-rq_timestamp); / timestamp Packet:free(p); /*=*/判断节点是否有到达目的节点足够新的路由？else if (rt & (rt-rt_hops != INFINITY2) & (rt-rt_seqno = rq-rq_dst_seqno) ) /如果不是目的地址，但是有足够新的路由 /assert (rt-rt_flags = RTF_UP); assert(rq-rq_dst = rt-rt_dst); /assert (rt-rt_seqno%2) = 0);/ is the seqno even?/向源节点发送路由应答分组 sendReply(rq-rq_src, rt-rt_hops + 1, /如果是目的节点的话就设成一，这里不是目的节点就在个RREQ中的跳数加1； rq-rq_dst, /如果是目的节点这一项就是目的节点的IP地址（这个节点本身的地址），这里是RREQ中的目的节点IP地址 rt-rt_seqno, (u_int32_t) (rt-rt_expire - CURRENT_TIME), / rt-rt_expire - CURRENT_TIME, rq-rq_timestamp); / Insert nexthops to RREQ source and RREQ destination in the / precursor lists of destination and source respectively/ /更新正向路由项和反向路由项的前驱列表 rt-pc_insert(rt0-rt_nexthop); / nexthop to RREQ source rt0-pc_insert(rt-rt_nexthop); / nexthop to RREQ destination#ifdef RREQ_GRAT_RREP / /向目的节点发送路由应答分组，并且回收路由请求分组 sendReply(rq-rq_dst, rq-rq_hop_count, rq-rq_src, rq-rq_src_seqno, (u_int32_t) (rt-rt_expire - CURRENT_TIME), / rt-rt_expire - CURRENT_TIME, rq-rq_timestamp);#endif / TODO: send grat RREP to dst if G flag set in RREQ using rq-rq_src_seqno, rq-rq_hop_counT / DONE: Included gratuitous replies to be sent as per IETF aodv draft specification. As of now, G flag has not been dynamically used and is always set or reset in aodv-packet.h - Anant Utgikar, 09/16/02.Packet:free(p); /*=*/ /* * Cant reply. So forward the Route Request */如果没有到达目的节点足够新的路由，继续转发路由请求分组 e