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usyslog.c
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usyslog.c
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// usyslog.c - Send message to remote UDP SYSLOG server
//
// Marquette University - COEN 4840
// Fred J. Frigo
// 18-Mar-2021
//
// 09-May-2023 - Updates for RFC 5424 format
//
// To compile: gcc -Wall -o usyslog usyslog.c
//
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#include <time.h>
#include <arpa/inet.h>
#define MAX 256
#define PORT 514
#define SA struct sockaddr
void func(int sockfd, struct sockaddr_in *servaddr)
{
char rfc3164_syslog_msg[4*MAX];
char rfc5424_syslog_msg[4*MAX];
char *syslog_msg;
char rfc3164_time[MAX];
char rfc5424_time[MAX];
char myHost[MAX];
char myMessage[MAX];
char *username;
int pri = (13*8)+6; // RFC 3164: priority 13 = log audit, priority = 6 infoa
int version = 1; // RFC 5424: version
struct timespec current_time;
int pid, usec;
struct tm *time;
int tz_hour, tz_min;
char* c_time_string;
// Get username and local host name
username = getenv("USER");
gethostname(myHost, MAX);
// Get message
printf("Enter message to send to server: ");
fgets(myMessage, sizeof(myMessage), stdin);
myMessage[strlen(myMessage)-1] = 0; // get rid of the '/n' character
// Obtain current time.
clock_gettime( CLOCK_REALTIME, ¤t_time);
// RFC 3164 message (not used)
c_time_string = ctime(¤t_time.tv_sec);
strncpy(rfc3164_time, &c_time_string[4], 15); // copy only characters needed
sprintf(rfc3164_syslog_msg, "<%d>%s %s UDP: RFC3164 message from %s: %s", pri, rfc3164_time, myHost, username, myMessage );
// RFC 5424 message with NO Structured Data
time = localtime(¤t_time.tv_sec);
tz_hour = (int)(time->tm_gmtoff/(60*60));
tz_min = (int)(labs(time->tm_gmtoff/60) - labs(tz_hour*60));
pid = (int)getpid();
usec = (int)current_time.tv_nsec/1000;
sprintf(rfc5424_time,"%4.4d%c%2.2d%c%2.2dT%2.2d:%2.2d:%2.2d.%6.6d%+2.2d:%2.2d",
time->tm_year+1900, '-', time->tm_mon+1, '-', time->tm_mday, time->tm_hour, time->tm_min, time->tm_sec, usec, tz_hour, tz_min );
sprintf(rfc5424_syslog_msg, "<%d>%d %s %s UDP %s %d %c RFC5424 message from %s: %s",
pri, version, rfc5424_time, myHost, "usyslog", pid, '-', username, myMessage );
// Send Syslog mesage
//syslog_msg = rfc3164_syslog_msg;
syslog_msg = rfc5424_syslog_msg;
sendto(sockfd, (const char *)syslog_msg, strlen(syslog_msg),
MSG_DONTWAIT, (const struct sockaddr *) servaddr,
sizeof(struct sockaddr_in));
printf("SYSLOG message sent: %s\n",syslog_msg);
}
int main(int argc, char *argv[])
{
int sockfd;
struct sockaddr_in servaddr;
struct addrinfo hints, *infoptr;
struct addrinfo *p;
char host[256];
// Validate the parameters
if (argc != 2) {
printf("usage: %s server-name\n", argv[0]);
return 1;
}
memset(&hints, 0, sizeof hints);
hints.ai_family = AF_UNSPEC; // use AF_INET6 to force IPv6
hints.ai_socktype = SOCK_STREAM;
int result = getaddrinfo(argv[1], NULL, &hints, &infoptr);
if (result)
{
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(result));
exit(1);
}
for (p = infoptr; p != NULL; p = p->ai_next)
{
getnameinfo(p->ai_addr, p->ai_addrlen, host, sizeof (host), NULL, 0, NI_NUMERICHOST);
puts(host);
}
freeaddrinfo(infoptr);
// socket create and varification
sockfd = socket(AF_INET, SOCK_DGRAM, 0);
if (sockfd == -1) {
printf("socket creation to SYSLOG server failed...\n");
exit(0);
}
else
printf("Socket successfully created..\n");
bzero(&servaddr, sizeof(servaddr));
// assign IP, PORT
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = inet_addr(host);
servaddr.sin_port = htons(PORT);
// function to ask user to input the test message
func(sockfd, &servaddr);
// close the socket
close(sockfd);
}