BjKXvHKK

1/*
2
3
4 * mypingd.c
5 *
6 *  Created on: Sep 17, 2016
7 *      Author: prashantravi
8 */
9#define _DEFAULT_SOURCE
10#include <stdio.h>
11#include <stdlib.h>
12#include <unistd.h>
13#include <errno.h>
14#include <string.h>
15#include <sys/types.h>
16#include <sys/socket.h>
17#include <netinet/in.h>
18#include <arpa/inet.h>
19#include <netdb.h>
20#include <sys/time.h>
21#include <time.h>
22#include <unistd.h>
23#include <fcntl.h>
24#include <signal.h>
25
26typedef int bool;
27#define true 1
28#define false 0
29
30#define MAX_BUF 1000
31#define EXPECTED_RESPONSE "terve"
32#define TIME_OUT 550000
33#define INTERVAL 50000
34
35volatile bool received = false;
36volatile sig_atomic_t got_interrupt = 0;
37pid_t current_pid = -1 ;
38
39void make_alphanumeric_string(char *s, const int len);
40int sendPingRequest(char* hostname, char* hostUDPport, char* secretKey);
41void validateCommandLineArguments(int argc, char ** argv);
42void printTimeDifference(struct timeval *t1 , struct timeval *t2);
43void handle_signal_alarm(int sig);
44
45void handle_signal_alarm(int sig)
46{
47	int saved_errno = errno;
48	if (sig != SIGALRM) {
49		perror("Caught wrong signal\n");
50	}
51	if(received == false && got_interrupt++ == 40){
52		printf( "no response from ping server\n" );
53		kill(current_pid,SIGKILL);
54	}
55	errno = saved_errno;
56}
57
58
59void make_alphanumeric_string(char *s, const int len) {
60	static const char alphanum[] =
61			"0123456789"
62			"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
63			"abcdefghijklmnopqrstuvwxyz";
64
65	int i;
66	for ( i = 0; i < len; ++i) {
67		s[i] = alphanum[rand() % (sizeof(alphanum) - 1)];
68	}
69	s[len] = 0;
70}
71
72void printTimeDifference(struct timeval *t1 , struct timeval *t2)
73{
74	struct timeval tv1 = *t1;
75	struct timeval tv2 = *t2;
76	long milliseconds;
77	milliseconds = (tv2.tv_usec - tv1.tv_usec) / 1000;
78	milliseconds += (tv2.tv_sec - tv1.tv_sec) *1000;
79	printf("Round trip time was : %3ld ms\n",milliseconds);
80}
81
82void validateCommandLineArguments(int argc, char ** argv)
83{
84	// Write this validation properly TODO
85	if(argc != 4)
86	{
87		printf("\nERROR! usage: %s receiver_hostname receiver_port secret_key\n\n", argv[0]);
88		exit(1);
89	}
90}
91
92
93int sendPingRequest(char* hostname, char* hostUDPport, char* secretKey)
94{
95	int sockfd;
96	struct addrinfo hints, *servinfo;
97	int rv;
98	int numbytes;
99
100	memset(&hints, 0, sizeof hints);
101	hints.ai_family = AF_INET;
102	hints.ai_socktype = SOCK_DGRAM;
103
104	if ((rv = getaddrinfo(hostname, hostUDPport, &hints, &servinfo)) != 0) {
105		fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
106		return 2;
107	}
108
109	struct addrinfo *availableServerSockets = servinfo;
110	bool connectionSuccessful = false;
111	while(availableServerSockets != NULL)
112	{
113		bool error = false;
114
115		if ((sockfd = socket(availableServerSockets->ai_family, availableServerSockets->ai_socktype,availableServerSockets->ai_protocol)) == -1) {//If it fails...
116			error = true;
117		}
118		if(error)
119			availableServerSockets = availableServerSockets->ai_next;
120		else
121		{
122			connectionSuccessful = true;
123			break;
124		}
125	}
126
127	if(!connectionSuccessful)
128	{
129		printf("Could not connect to host \n");
130		return 2;
131	}
132	else
133	{
134		// Successfully connected to server
135	}
136	int tr = 1;
137	setsockopt(sockfd, SOL_SOCKET, SO_RCVTIMEO, &tr, sizeof(int));
138
139	// Construct message with format $secretKey$pad to be 1000 bytes
140	char str[MAX_BUF];
141	//Get length of secret key.
142	int dlen = (strlen(secretKey)) * sizeof(char);
143	sprintf(str, "$%s$", secretKey);
144	dlen = dlen + 2*sizeof(char);
145	//Find how many alphanumeric characters we need to pad
146	int dpad = MAX_BUF - dlen;
147	//Our final sending buffer
148	char fSendBuffer[MAX_BUF] = {0};
149	memcpy(fSendBuffer, str , dlen);
150	make_alphanumeric_string(fSendBuffer+dlen, dpad );
151
152	char recv_response[6];
153	struct timeval tv1;
154	struct timezone tz1;
155	struct timeval tv2;
156	struct timezone tz2;
157	struct sockaddr_in from;
158	socklen_t addr_len = sizeof from;
159	socklen_t sin_size = sizeof(struct sockaddr);
160	signal(SIGALRM, handle_signal_alarm);
161	ualarm(TIME_OUT,INTERVAL);
162	if (-1 == gettimeofday(&tv1, &tz1)) {
163		perror("resettimeofday: gettimeofday");
164		exit(-1);
165	}
166	if(sendto(sockfd, fSendBuffer, strlen(fSendBuffer), 0, availableServerSockets->ai_addr, availableServerSockets->ai_addrlen) == -1)
167	{
168		perror("sendto: failed\n");
169	}
170	socklen_t addrlen = sizeof(from); /* must be initialized */
171	recvfrom(sockfd, recv_response, sizeof(recv_response), 0, (struct sockaddr *)&from, &addrlen);
172	received = true;
173	if (-1 == gettimeofday(&tv2, &tz2)) {
174		perror("resettimeofday: gettimeofday");
175		exit(-1);
176	}
177	recv_response[5] = '\0';
178	struct hostent *hostp; /* server host info */
179	hostp = gethostbyaddr((const char *)&from.sin_addr.s_addr,
180			sizeof(from.sin_addr.s_addr), AF_INET);
181	if (hostp == NULL)
182		perror("ERROR on gethostbyaddr");
183	char *hostaddrp; /* dotted decimal server host addr string */
184	hostaddrp = inet_ntoa(from.sin_addr);
185	if (hostaddrp == NULL)
186		perror("ERROR on inet_ntoa\n");
187	if(strcmp(EXPECTED_RESPONSE, recv_response ) == 0)
188	{
189		printTimeDifference(&tv1, &tv2);
190	}
191	else
192		printf("Packet received was corrupt : %s\n", recv_response);
193	printf("Client received datagram from %s (%s)\n",hostp->h_name, hostaddrp);
194	close(sockfd);
195	return EXIT_SUCCESS;
196}
197
198int main(int argc, char** argv)
199{
200	validateCommandLineArguments(argc, argv);
201	current_pid = getpid();
202	return sendPingRequest(argv[1], argv[2], argv[3]);
203}