ICMP Message Processing Homework Assignment #2 ICMP Message Processing

Homework Assignment #2: ICMP Message Processing In this work, you are asked to use timestamp request/reply message to simulate the ping function and calculate the RTT value Write a program that send a ICMP timestamp request packet to a host, and receive ICMP timestamp reply packet Furthermore, also calculate the round-trip time (RTT)

Flowchart Start Establish socket Establish ICMP packet Header: #include <sys/types.h> #include <sys/socket.h> Define: int socket(int domain,int type,int protocol) The third parameter, Protocol, is ICMP Establish socket Header: #include <netinet/ip_icmp.h> struct icmp *icmp_hdr=(struct icmp *)buffer; //#define ICMP_TIMESTAMP icmp_hdr->icmp_type=13; icmp_hdr->icmp_code=0; Establish ICMP packet

Flowchart (cont.) Receive ICMP reply Calculate RTT Use sendto() function Ex. sendto(sockfd,buffer,packsize,0,(struct sockaddr*)&addr,addr_len) Send ICMP request Use recvfrom() function Ex. recvfrom(sockfd,rbuf,sizeof(rbuf),0,NULL,NULL) Receive ICMP reply struct icmp *icmp_hdr_R=(struct iphdr*)(rbuf+20); 28~31 byte : original time(T1) 32~35 byte : receive time(T2) 36~40 byte : transmit time(T3) You need calculating back time by yourself (use time.h)(T4) RTT= (T4-T3) + (T2-T1) Calculate RTT

Executable Command Format: myping [addr] Ex. #myping 140.120.15.125 icmp_type= 13,icmp_code=0 Original time=11096271 Receive time=875902519 Transmit time=943274555 Back time=60140638416 RTT=-67372035 ------------------------------------------------ icmp_type=14,icmp_code=0 Receive time=11096271 Transmit time=11096271 Back time=11096276 RTT=6

Turn In Source code Executing result (snapshot)

Turn In (cont.) Deadline Ftp Filename If you want to update 23:59, May 16, 2005 Ftp IP:140.120.15.125 Username/Password: comm93/comm93 Filename HW2_ID.doc eg.HW2_79356001.doc If you want to update HW2_ID_new1.doc, HW2_ID_new2.doc …etc

Turn In (cont.) No late work is acceptable No cheat work is acceptable You get zero if you miss the due day No cheat work is acceptable You get zero if you copy other people’s version

Reference Linux C/C++ 網路程式設計,金禾 Linux C 函式庫參考手冊,旗標 Linux Socket Programming,碁峰