监控网络链接

/*
 * check net
 */
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/time.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
#include <sys/signal.h>

#define PACKET_SIZE 512
#define TRYCONT     59

char sendpacket[PACKET_SIZE];
char recvpacket[PACKET_SIZE];

int sockfd, datalen = 56;

struct sockaddr_in dest_addr;
struct sockaddr_in from;
pid_t pid;

int my_sequence = 0;
int g_try = TRYCONT;

void handle_sigalrm(int signo);
void handle_sigint(int signum);
void send_pack(void);
void recv_pack(void);
unsigned short check_sum(unsigned short *addr, int len);

void reboot_sys()
{
if(!(g_try%10))
{
system("ifconfig eth0 down");
printf("Restart net\n");
system("ifconfig eth0 up");
}

if(!g_try)
{
printf("System reboot now ......\n");
system("reboot");
}
printf("\nHas -> %d times last\n", g_try);
g_try--;
}

/*signal producure for sending icmp */
void handle_sigalrm(int signo)
{
send_pack();
alarm(2); //produce a signal for sending icmp
}

/*signal producure for finishing ping */
void handle_sigint(int signum) {
printf("\texit\n");
close(sockfd);
exit(0);
}
/* Check Sum */
unsigned short check_sum(unsigned short *addr, int len)
{
int nleft = len;
unsigned short *w = addr;
int sum = 0;
unsigned short answer = 0;

while (nleft > 1)
{
sum += *w++;
nleft -= 2;
}

if (nleft == 1)
{
*(unsigned char *)(&answer)=*(unsigned char *)w;
sum += answer;
}

sum = (sum >> 16) + (sum & 0xffff); /* add hi 16 to low 16 */
sum += (sum >> 16); /* add carry */
answer = ~sum; /* truncate to 16 bits */

return (answer);
}
/*packet*/
int pack(int pack_no)
{
int i, packsize;
struct icmp *icmp;
struct timeval *tval;

icmp = (struct icmp*)sendpacket;
icmp->icmp_type = ICMP_ECHO;
icmp->icmp_code = 0;
icmp->icmp_cksum = 0;
icmp->icmp_seq = pack_no;
icmp->icmp_id = pid;
packsize = 8+datalen;
tval = (struct timeval *)icmp->icmp_data;
gettimeofday(tval,NULL);
icmp->icmp_cksum = check_sum((unsigned short *)icmp,packsize);
return packsize;
}
/*send icmp packet*/
void send_pack(void)
{
int len = 0;
int packetsize = pack(my_sequence);
len = sendto(sockfd,sendpacket,packetsize,0,(struct sockaddr *)&dest_addr,sizeof(struct sockaddr));
if(len < 0)
{
perror("sendto error");
reboot_sys();
}
//printf("%s:len=%d\n",__func__,len);

++my_sequence;
printf("Sendto %s\n", inet_ntoa(dest_addr.sin_addr));
}

/*unpacket*/
int unpack(char *buf, int len)
{
int i;
int iphdrlen;
struct ip *ip;
struct icmp *icmp;
struct timeval *tvsend;
double rtt;

ip = (struct ip *)buf;
iphdrlen = ip->ip_hl << 2;
icmp = (struct icmp *)(buf+iphdrlen);
len -= iphdrlen;
if(len < 8)
{
printf("ICMP packet\'s length is less than 8\n");
return -1;
}

if((icmp->icmp_type == ICMP_ECHOREPLY) && (icmp->icmp_id == pid))
{
tvsend = (struct timeval *)icmp->icmp_data;
printf("Internet ......OK!!\n");
g_try = TRYCONT;
}
else return -1;

return 0;
}

void recv_pack(void)
{
int len, fromlen, res;
fromlen = sizeof(from);

while(1)
{
len = recvfrom(sockfd, recvpacket, sizeof(recvpacket),0,(struct sockaddr *)&from, &fromlen);
if(len < 0)
{
perror("recvform eorror");
reboot_sys();
}
printf("len = %d\n", len);

if(unpack(recvpacket,len) == -1) continue;
sleep(2);
}
}

int main(int argc, char **argv)
{
struct protoent *protocol;
struct sigaction act;
struct sigaction act2;

if (2 != argc)
{
printf("Parameter is Wrong!\n");
printf("\tusage [param]\n");
printf("\tparam:ip address\n");
exit(-1);
}

if((protocol = getprotobyname("icmp")) == NULL)
{
perror("getprotobyname");
exit(0);
}
if ((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP)) < 0)
{
perror("fail to socket!");
exit(-1);
}

memset(&act, 0, sizeof(act));
act.sa_handler = handle_sigalrm;
sigemptyset(&act.sa_mask);
act.sa_flags = 0;

if (-1 == sigaction(SIGALRM, &act, NULL))
perror("sigaction-1");

pid = getpid();

bzero(&dest_addr, sizeof(struct sockaddr_in));
dest_addr.sin_family = AF_INET;
inet_pton(AF_INET, argv[1], &dest_addr.sin_addr.s_addr);

struct sigaction sa2;
memset(&sa2, 0, sizeof(sa2));
sa2.sa_handler = handle_sigint;//catch_sigint;
sigemptyset(&sa2.sa_mask);
sa2.sa_flags = 0;
if(sigaction(SIGINT, &sa2, NULL) == -1)
perror("sigaction-2");

alarm(2);
sleep(2);
recv_pack();

return 0;

}