北邮计算机网络数据链路层实验滑动窗口协议的设计与实现——选择重传协议

#include <stdio.h> #include <stdlib.h> #include <string.h> #include "protocol.h" #include "datalink.h" void printData(char *p, int size); typedef unsigned char seq_nr; typedef unsigned char frame_kind; typedef struct{unsigned char data[PKT_LEN];} packet; typedef enum{network_layer_ready, physical_layer_ready, frame_arrive, data_timout, ack_timeout, chksum_error} event_type; typedef enum{F, T} mybool; typedef struct { frame_kind kind; /* FRAME_DATA */ seq_nr ack; seq_nr seq; packet info; /* packet */ unsigned char padding[4]; /* memory space used for crc code, 32 bit */ } frame; mybool no_nak = T; /* no nak has beem yet */ static void Inc(seq_nr *seq) { *seq = (*seq + 1) % (MAX_SEQ + 1); } static mybool between(seq_nr a, seq_nr b, seq_nr c) { /*return T if a <= b circulaly; F otherwise*/ return ((a <= b) && (b < c)) || ((c < a) && (a <= b)) || ((b < c) && (c < a)); } static void send(frame_kind fk, seq_nr frame_nr, seq_nr frame_expected, packet buf[]) { /* construct frame and send */ frame s; /* tmp variable */ s.kind = fk; /* s.kind = data/ack/nak */ if (fk == FRAME_DATA) memcpy((char*)&s.info, (char*)&buf[frame_nr % NR_BUFS], PKT_LEN); /* store the packet */ s.seq = frame_nr; /* only meaning for data */ s.ack = (frame_expected + MAX_SEQ) % (MAX_SEQ + 1); if (fk == FRAME_NAK) no_nak = F; /* compute the crc code, the crc code is in the padding memory */ *(unsigned int*) ((unsigned char*)&s + PKT_LEN + 3) = crc32((unsigned char*)&s, PKT_LEN + 3); /* send the frame to the physical layer */ send_frame((unsigned char*)&s, sizeof(s)); dbg_event("组装之后的 !!\n"); printData((char*)&s, sizeof(s)); //printf("CRC send"); //printData(s.padding,4); /* warning: short may not be 2 bytes, according to the computer */ if (fk == FRAME_DATA) dbg_frame("Send DATA seq:%d ack:%d, ID %d\n", s.seq, s.ack, *(short *)(&s.info)); else if (fk == FRAME_ACK) dbg_frame("Send ACK seq:%d\n", s.seq); else if (fk == FRAME_NAK) dbg_frame("Send NAK seq:%d\n", s.seq); if (fk == FRAME_DATA) /* start the timeout, if timeout, repeat transmit */ start_timer(frame_nr % NR_BUFS, DATA_TIMER); stop_ack_timer(); /* no need for separate ack frame */ } void protocol6() { int mid,stop=0; seq_nr ack_expected = 0; /* lower edge of sender's window */ seq_nr next_frame_to_send = 0; /* upper edge of sender's window */ seq_nr frame_expected = 0; /* lower edge of receiver's window */ seq_nr too_far = NR_BUFS; /* uppder edge receiver's window + 1*/ packet out_buf[NR_BUFS]; /* buffers for the outbound stream*/ packet in_buf[NR_BUFS]; /* buffers for the inbound stream*/ mybool arrived[NR_BUFS] = {F}; /* inbound bit map, intial to all F */ seq_nr nbuffered = 0; /* the size of buffered */ frame r; /* tmp variable */ int arg = MAX_SEQ + 1; /* para */ int len = 0; /* the length of received packet*/ unsigned crc_ret = 0; event_type event; /* type of event */ enable_network_layer(); while (T) { event = (event_type)wait_for_event(&arg); /* event to be what */ switch (event) { case network_layer_ready: /* accept, save, and transmit a new frame;sender */ dbg_event("network_layer_ready; \n"); ++nbuffered; /* expand the window */ get_packet((unsigned char*)&out_buf[next_frame_to_send % NR_BUFS]); /* fetch new packet int the window */ dbg_event("从网络层来的 !!\n"); printData((char*)&out_buf[next_frame_to_send % NR_BUFS], sizeof(out_buf[next_frame_to_send % NR_BUFS])); send(FRAME_DATA, next_frame_to_send, frame_expected, out_buf); /* transmit the new frame */ Inc(&next_frame_to_send); /* advance the upper window edge */ break; case frame_arrive: /* a data or control frame has arrived */ dbg_event("\nframe_arrival; \n"); /* fetch incoming frame from physical layer, len get the size of the recevied frame */ len = recv_frame((unsigned char*)&r, sizeof(r)); dbg_event("从链路层收来的 !!\n"); printData((char*)&r, sizeof(r)); /* warning: short may not be 2 bytes, according to the computer */ if (r.kind == FRAME_DATA) dbg_frame("Recv DATA seq:%d ack:%d, ID %d\n", r.seq, r.ack, *(short *)(&r.info)); else if (r.kind == FRAME_ACK) dbg_frame("Recv ACK seq:%d\n", r.seq); else if (r.kind == FRAME_NAK) dbg_frame("Recv NAK seq:%d\n", r.seq); //dbg_frame("CRC receive:"); //printData(r.padding,4);//打印CRC if (r.kind == FRAME_DATA) /* if it's a data frame, check seq and whether it should be received */ { /* check the crc code */ crc_ret = crc32((unsigned char*)&r, len); if (crc_ret != 0) /* check crc code error, goto chksum_error */ { goto crc_error; } //printf("crc correct!\n"); /* an undamage frame has arrived*/ if (r.seq != frame_expected && no_nak) /* it's not the expected frame, send back a nak frame */ { send(FRAME_NAK, 0, frame_expected, out_buf); /* send nak, 0 has no meanings */ } else { start_ack_timer(ACK_TIMER); /* right frame, start the ack timer, whether to send back ack by a sepatate frame */ } /* the receiver's window */ if (between(frame_expected, r.seq, too_far) && arrived[r.seq % NR_BUFS] == F) /* in the window and has't ever arrived */ { /* frame may be received in any order */ arrived[r.seq % NR_BUFS] = T; /* record in the bit map the arrival of some frame */ memcpy(&in_buf[r.seq % NR_BUFS], &r.info, sizeof(packet)); /* store the frame */ while (arrived[frame_expected % NR_BUFS]) /* the expected frame has successfully arrived, welcome it */ { /* pass the frame and advance the window */ put_packet((unsigned char*)&in_buf[frame_expected % NR_BUFS], sizeof(packet)); //dbg_frame("RIGHT RECEIVE！　Recv DATA %d %d, ID %d\n", frame_expected % NR_BUFS, r.ack, *(short *)(&r.info)); /* clear the state variable */ no_nak = T; arrived[frame_expected % NR_BUFS] = F; Inc(&frame_expected); /* update the expected frame */ Inc(&too_far); /* advance the window */ start_ack_timer(ACK_TIMER); /* to see if a separate ack is needed */ } } /* this code has two start_ack_timer(), again will not reset */ } /* selective retransmit */ if (r.kind == FRAME_NAK && between(ack_expected, (seq_nr)((r.ack + 1) % (MAX_SEQ + 1)), next_frame_to_send)) send(FRAME_DATA, (seq_nr)((r.ack + 1) % (MAX_SEQ + 1)), frame_expected, out_buf); /* if(*(short *)(&r.info)==20007) { scanf("%d",&mid); stop=1; } */ /* check the confirm seq, if it has been received successfully, advance the sender's window */ while (between(ack_expected, r.ack, next_frame_to_send)) { --nbuffered; /* handle piggbacked ack */ stop_timer(ack_expected % NR_BUFS); /* frame arrived intact */ Inc(&ack_expected); /* advance the sender's window */ } break; case data_timout: /* timeout retransmit */ dbg_event("\ndata_timout; \n"); /* arg hold the seq of the timeout timer */ send(FRAME_DATA, (seq_nr)arg, frame_expected, out_buf); dbg_event("arg=%d; \n",arg); break; case ack_timeout: dbg_event("\nack_timout; \n"); send(FRAME_ACK, 0, frame_expected, out_buf); /* ack timeout, send ack */ break; case chksum_error: /* damaged frame */ crc_error: dbg_event("checksum_error; \n"); if (no_nak) { send(FRAME_NAK, 0, frame_expected, out_buf); /* damaged frame */ } break; default: break;