Simple Linux and UNIX system monitoring with ping command and scripts

@shilpa: PING using icmp protocol. You can read more here:
http://www.iana.org/assignments/icmp-parameters

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hi,
i am doing a small program on the working of ping command in linux using icmp protocol. here is the code but its giving an error at getuid()

#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
char dst_addr[20];
char src_addr[20];
unsigned short in_cksum(unsigned short*,int);
void parse_argvs(char**,char*,char*);
void usage();
char *getip();
char *toip(char*);
int main(int argc, char *argv[])
{
struct iphdr *ip;
struct iphdr *ip_reply;
struct icmphdr *icmp;
struct sockaddr_in connection;
char *packet=NULL;
char *buffer=NULL;
int sockfd;
int optval;
int addrlen;
int siz;
printf(“%d”,getuid());
if(getuid()!=0)
{
fprintf(stderr,”%s:rot privileges needed\n”,*(argv+0));
exit(EXIT_FAILURE);
}
parse_argvs(argv,dst_addr,src_addr);
strncpy(dst_addr,toip(dst_addr),20);
strncpy(src_addr,toip(src_addr),20);
printf(“src addr is %s\n”,src_addr);
printf(“dest addre is %s\n”,dst_addr);
packet=malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
buffer=malloc(sizeof(struct iphdr) + sizeof(struct icmphdr));
ip=(struct iphdr *)packet;
icmp=(struct icmphdr *)(packet + sizeof(struct iphdr));
ip->ihl=5;
ip->version=4;
ip->tos=0;
ip->tot_len=sizeof(struct iphdr) + sizeof(struct icmphdr);
ip->id=htons(0);
ip->frag_off=0;
ip->ttl=64;
ip->protocol=IPPROTO_ICMP;
ip->saddr=inet_addr(src_addr);
ip->daddr=inet_addr(dst_addr);
ip->check=in_cksum((unsigned short *)ip,sizeof(struct iphdr));
if((sockfd=socket(AF_INET,SOCK_RAW,IPPROTO_ICMP))==-1)
{
perror(“socket”);
exit(EXIT_FAILURE);
}
setsockopt(sockfd,IPPROTO_IP,IP_HDRINCL,&optval,sizeof(int));
icmp->type=ICMP_ECHO;
icmp->code=0;
icmp->un.echo.id=random();
icmp->un.echo.sequence=0;
icmp->checksum=in_cksum((unsigned short *)icmp,sizeof(struct icmphdr));
connection.sin_family=AF_INET;
connection.sin_addr.s_addr=inet_addr(dst_addr);
sendto(sockfd,packet,ip->tot_len,0,(struct sockaddr *)&connection,sizeof(struct sockaddr));
printf(“sent %d byte packet to %s\n”,ip->tot_len,dst_addr);
addrlen=sizeof(connection);
if((siz=recvfrom(sockfd,buffer,sizeof(struct iphdr) + sizeof(struct icmphdr),0,(struct sockaddr *)&connection,&addrlen))==-1)
{
perror(“recv”);
}
else
{
printf(“received %d byte reply from %s\n”,siz,dst_addr);
ip_reply=(struct iphdr *)buffer;
printf(“ID: %d\n”,ntohs(ip_reply->id));
printf(“ttl:%d\n”,ip_reply->ttl);
}
free(packet);
free(buffer);
close(sockfd);
return 0;
}

void parse_argvs(char **argv,char *dst,char *src)
{
int i;
if(!(*(argv + 1 ) ) )
{
usage();
exit(EXIT_FAILURE);
}
if(*(argv + 1) && (!(*(argv + 2 ) ) ) )
{
strncpy(dst,*(argv + 1),15);
return;
}
else if((*(argv + 1 ) && (* ( argv + 2 ) ) ) )
{
strncpy(dst,*(argv + 1 ),15);
i=2;
while(*(argv + i + 1 ) )
{
if(strncmp(*(argv + i),”-s”,2)==0)
{
strncpy(src,*(argv + i + 1),15);
break;
}
i++;
}
}
}

void usage()
{
fprintf(stderr, “\n usage:ping [destination] \n”);
fprintf(stderr,”destination must be provided\n”);
fprintf(stderr,”source is optional \n \n”);
}
char * getup()
{
char buffer[256];
struct hostent *h;
gethostname(buffer,256);
h=gethostbyname(buffer);
return inet_ntoa(*(struct in_addr *)h->h_addr);
}
char * toip(char * address)
{
struct hostent *h;
h=gethostbyname(address);
return inet_ntoa(*(struct in_addr *)h->h_addr);
}
unsigned short in_cksum(unsigned short *addr, int len)
{
register int sum=0;
u_short answer=0;
register u_short *w=addr;
register int nleft=len;
while(nleft > 1)
{
sum+=*w++;
nleft-=2;
}
if(nleft==1)
{
*(u_char*) (&answer)=*(u_char*)w;
sum+=answer;
}
sum=(sum>>16) + (sum & 0xffff);
sum+=(sum>>16);
answer=~sum;
return(answer);
}

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Hi coders

What would i use if i needed 1 timestamp when “Ping up again” ?

Thanks

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thanks , this work :D

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@Константин Кръстев
I love your line, but could you explain the bit after the “>” I don’t get that.

It does work I just don’t know why!

Thanks,
Der

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