TJU计网RDT实验代码和报告

#include <stdio.h> #include <stdlib.h> #include <stdbool.h> /* ****************************************************************** ALTERNATING BIT AND GO-BACK-N NETWORK EMULATOR: VERSION 1.1 J.F.Kurose This code should be used for PA2, unidirectional or bidirectional data transfer protocols (from A to B. Bidirectional transfer of data is for extra credit and is not required). Network properties: - one way network delay averages five time units (longer if there are other messages in the channel for GBN), but can be larger - packets can be corrupted (either the header or the data portion) or lost, according to user-defined probabilities - packets will be delivered in the order in which they were sent (although some can be lost). **********************************************************************/ #define BIDIRECTIONAL 0 /* change to 1 if you're doing extra credit */ /* and write a routine called B_output */ /* a "msg" is the data unit passed from layer 5 (teachers code) to layer */ /* 4 (students' code). It contains the data (characters) to be delivered */ /* to layer 5 via the students transport level protocol entities. */ struct msg { char data[20]; }; /* a packet is the data unit passed from layer 4 (students code) to layer */ /* 3 (teachers code). Note the pre-defined packet structure, which all */ /* students must follow. */ struct pkt { int seqnum; int acknum; int checksum; char payload[20]; }; struct event { float evtime; /* event time */ int evtype; /* event type code */ int eventity; /* entity where event occurs */ struct pkt *pktptr; /* ptr to packet (if any) assoc w/ this event */ struct event *prev; struct event *next; }; /* possible events: */ #define TIMER_INTERRUPT 0 #define FROM_LAYER5 1 #define FROM_LAYER3 2 #define OFF 0 #define ON 1 #define A 0 #define B 1 /********* STUDENTS WRITE THE NEXT SEVEN ROUTINES *********/ //框架函数声明 void init(); void generate_next_arrival(); void printevlist(); void insertevent(struct event *p); void stoptimer(int AorB); void starttimer(int AorB, float increment); void tolayer3(int AorB, struct pkt packet); void tolayer5(int AorB, struct msg message); //根据FSM图定义A和B的状态 #define A_wait_for_call_0_from_above 0 #define A_wait_for_ACK_0 1 #define A_wait_for_call_1_from_above 2 #define A_wait_for_ACK_1 3 #define B_wait_for_0_from_below 0 #define B_wait_for_1_from_below 1 #define MAXTIME 100.0 //最大等待时间 int A_status, B_status; struct pkt buffer_pkt; //用来备份当前传输的包 //做包 struct pkt* make_pkt(int seqnum, int acknum, struct msg message) { struct pkt* mypkt = (struct pkt*)malloc(sizeof(struct pkt)); mypkt->seqnum = seqnum; mypkt->acknum = acknum; for (int i = 0; i < 20; i++) mypkt->payload[i] = message.data[i]; //计算校验和 int sum = 0; for (int i = 0; i < 20; i++) sum += (seqnum + acknum + (int) message.data[i]); mypkt->checksum = sum; return mypkt; } //判断包是否损坏 bool notCorrupt(struct pkt mypkt) { int sum = 0; for (int i = 0; i < 20; i++) sum += (mypkt.seqnum + mypkt.acknum + (int) mypkt.payload[i]); if (sum == mypkt.checksum) return true; else return false; } //缓存备份当前包 void buffer(struct pkt* mypkt) { buffer_pkt.seqnum = mypkt->seqnum; buffer_pkt.acknum = mypkt->acknum; buffer_pkt.checksum = mypkt->checksum; for (int i = 0; i < 20; i++) buffer_pkt.payload[i] = mypkt->payload[i]; } //B端拆包 void extract(struct pkt mypkt, struct msg *message) { for (int i = 0; i < 20; i++) message->data[i] = mypkt.payload[i]; } /* called from layer 5, passed the data to be sent to other side */ void A_output(struct msg message) //接收应用层的message { //等待应用层传入0号数据 if(A_status == A_wait_for_call_0_from_above) { struct pkt* sndpkt = make_pkt(0, 0, message); buffer(sndpkt); tolayer3(A, *sndpkt); starttimer(A, MAXTIME); A_status = A_wait_for_ACK_0; //更新状态，等待ack0 free (sndpkt); } //等待应用层传入1号数据 else if (A_status == A_wait_for_call_1_from_above) { struct pkt* sndpkt = make_pkt(1, 1, message); buffer(sndpkt); tolayer3(A, *sndpkt); starttimer(A, MAXTIME); A_status = A_wait_for_ACK_1; //更新状态，等待ack1 free (sndpkt); } //其他情况为等待ack的状态，不做处置 } void B_output(struct msg message) /* need be completed only for extra credit */ { //不做处理 } /* called from layer 3, when a packet arrives for layer 4 */ void A_input(struct pkt mypkt) //接收网络层的pkt，检验ack { if (A_status == A_wait_for_ACK_0) { printf("-----A looking forword ack 0,recive ack %d-----\n", mypkt.acknum); if(notCorrupt(mypkt) && mypkt.acknum == 0) //正确回应 { stoptimer(A); A_status = A_wait_for_call_1_from_above; } else printf("-----Wrong pkt-----\n"); } else if (A_status == A_wait_for_ACK_1) { printf("-----A looking forword ack 1,recive ack %d-----\n", mypkt.acknum); if(notCorrupt(mypkt) && mypkt.acknum == 1) //正确回应 { stoptimer(A); A_status = A_wait_for_call_0_from_above; } else printf("-----Wrong pkt-----\n"); } //其他情况为等待应用层传输，不做处置 } /* called when A's timer goes off */ void A_timerinterrupt() { tolayer3(A, buffer_pkt); starttimer(A, MAXTIME); } /* the following routine will be called once (only) before any other */ /* entity A routines are called. You can use it to do any initialization */ void A_init() { A_status = A_wait_for_call_0_from_above; } /* Note that with simplex transfer from a-to-B, there is no B_output() */ /* called from layer 3, when a packet arrives for layer 4 at B*/ void B_input(struct pkt mypkt) { struct msg message; struct pkt* sndpkt; extract(mypkt, &message); if(B_status == B_wait_for_0_from_below) //期望收到0号包 { printf("-----B looking forword pkt 0,recive seq %d-----\n", mypkt.seqnum); if(notCorrupt(mypkt) && mypkt.seqnum == 0) { //收到正确0号包 tolayer5(B, message); sndpkt = make_pkt(0, 0, message); //这里的seqnum不影响，可随意赋值 B_status = B_wait_for_1_from_below; } else if(!(notCorrupt(mypkt)) || mypkt.seqnum == 1) { //收到错误包 sndpkt = make_pkt(0, 1, message); //这里的seqnum不影响，可随意赋值 printf("-----Wrong pkt-----\n"); } else { //其他错误 sndpkt = make_pkt(0, 1, message); //这里的seqnum不影响，可随意赋值 } tolayer3(B, *sndpkt); free (sndpkt); } else if(B_status == B_wait_for_1_from_below) //期望收到1号包 { printf("-----B looking forword pkt 1,recive seq %d-----\n", mypkt.seqnum); if(notCorrupt(mypkt) && mypkt.seqnum == 1) { //收到正确1号包 tolayer5(B, message); sndpkt = make_pkt(0, 1, message); //这里的seqnum不影响，可随意赋值 B_status = B_wait_for_0_from_below; } else if(!(notCorrupt(mypkt)) || mypkt.seqnum == 0) { //收到错误包 sndpkt = make_pkt(0, 0, message); //这里的seqnum不影响，可随意赋值 printf("-----Wrong pkt-----\n"); } else { //其他错误 sndpkt = make_pkt(0, 0, message); //这里的seqnum不影响，�