main.c

程序实现了Linux下dhcp客户端以及autoip客户端的功能

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <net/if.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <errno.h>
#include <ctype.h>
#include "client.h"
#include "handler.h"
#include "udpipgen.h"

struct in_addr inform_ipaddr, default_router; 
char *ProgramName = NULL;
char **ProgramEnviron = NULL;
char *IfNameExt	= DEFAULT_IFNAME;
int IfNameExt_len = DEFAULT_IFNAME_LEN;
char *HostName = NULL;
int HostName_len = 0;
char *ClassID =	NULL;
int ClassID_len	= 0;
unsigned char *ClientID	= NULL;
int ClientID_len = 0;
void *(*currState)() = &Reboot;
int DebugFlag =	0;
int BeRFC1541 =	0;
unsigned LeaseTime = DEFAULT_LEASETIME;
int SetHostName	= 0;
int BroadcastResp = 0;
time_t TimeOut = DEFAULT_TIMEOUT;
int magic_cookie = 0;
unsigned short dhcpMsgSize = 0;
unsigned nleaseTime = 0;
int DoCheckSum = 0;
int SendSecondDiscover = 0;
int Persistent = 1;
int DownIfaceOnStop = 1;
int autoip_flag = 0;
int autoip_sleep = 300;
int SetDHCPDefaultRoutes= 1;
int RouteMetric	= 1;
int Window = 0;


int daemon_init(void)
{
  pid_t pid;
  if( (pid = fork()) < 0 )
    return(-1);
  else 
    if( pid != 0 )
      exit(0);
  setsid();
  chdir("/");
  umask(0);
  return(0);
}

int main(int argn, char *argc[], char *argv[])
{
  int s			=	1;
  int k			=	1;
  int i			=	1;
  int j;
/*
 * Ensure that fds 0, 1, 2 are open, to /dev/null if nowhere else.
 * This way we can close 0, 1, 2 after forking the daemon without clobbering
 * a fd that we are using (such as our sockets). This is necessary if
 * this program is run from init scripts where 0, 1, and/or 2 may be closed.
 */
  j=open("/dev/null",O_RDWR);
  while (j < 2 && j >= 0) 
    j = dup(j);
  if (j > 2) 
    close(j);
  if (geteuid()) {
    fprintf(stderr,"****  %s: not a superuser\n",argc[0]);
    exit(1);
  }
  while (argc[i])
    if (argc[i][0]=='-')
      switch (argc[i][s]) {
        case 'd':
	  i++;
	  DebugFlag=1;
	  continue;      //to see if there exists another parameter
	case 'g':
	  if (argc[i][s+1])
	    goto usage;
	  SetDHCPDefaultRoutes = 0;
	  i++;
	  if (argc[i] && inet_aton(argc[i], &default_router))
	    i++;
	  else
	    memset(&default_router, 0, sizeof(default_router));
	  s = 1;
	  break;
	case 'i':
	  if ( argc[i][s+1] ) 
	    goto usage;
	  i++;
	  IfNameExt = argc[i++];
	  if (IfNameExt == NULL || IfNameExt[0] == '-') 
	    goto usage;
	  s = 1;
	  if ((IfNameExt_len = strlen(IfNameExt) + 1) <= 5) {
	    printf("the interface name is %s\n", IfNameExt);
	    break;
	  }
	  printf("the interface name is %s\n", IfNameExt);
	  fprintf(stderr,"%s: too long Interface Name string: strlen=%d\n",argc[0], IfNameExt_len);
	  break;
	case 't':
	  if (argc[i][s+1]) 
	    goto usage;
	  i++;
	  if (argc[i])
	    TimeOut=atol(argc[i++]);
	    if (DebugFlag == 1)
	      printf("Set Timeout = %ds\n", TimeOut);
	  else
	    goto usage;
	  s=1;
	  if (TimeOut >= 0) 
	    break;
	  goto usage;
	case 'T':
	  if (argc[i][s+1]) 
	    goto usage;
	  i++;
	  if (argc[i])
	    autoip_sleep = atol(argc[i++]);
	    if (DebugFlag == 1)
	      printf("Set autoip_sleep = %ds\n", autoip_sleep);
	  else 
	    goto usage;
	  s=1;
	  if (autoip_sleep >= 0) 
	    break;
	  goto usage;  
          default:
usage:
	  fprintf(stderr,
"Usage: dhcpclient [-d(debug mode)] [-i interface name] [-t dhcp timeout] [-T AutoIP sleep time] [-g Gateway]\n");
	  exit(1);
     }
    else
      goto usage;
  
  ProgramName=argc[0];
  ProgramEnviron=argv;
  umask(022);
  signalSetup();
  magic_cookie = htonl(MAGIC_COOKIE);   
  dhcpMsgSize = htons(sizeof(dhcpMessage)+sizeof(udpiphdr));
  nleaseTime = htonl(LeaseTime);
  if (TimeOut != 0)
    alarm(TimeOut);
  while ( (currState!= &Bound) && (autoip_flag == 0)){
  if ( (currState=(*currState)()) == NULL ) 
    exit(1);
  }
  if (DebugFlag == 0) {
    if ( (i=open("/dev/null",O_RDWR,0)) >= 0 ) {
    (void)dup2(i,STDIN_FILENO);
    (void)dup2(i,STDOUT_FILENO);
    (void)dup2(i,STDERR_FILENO);
    if ( i > 2 ) (void)close(i);
    }
  } 
  daemon_init();
  if (autoip_flag == 1) {
    currState = &Init;
    while ( currState!= &Bound )
    if ( (currState=(*currState)()) == NULL ) 
      exit(1);
  }
 autoip_flag = 0;
 alarm(0);     //cancel the alarm set previously
 while ( currState )
   currState=(*currState)();
 exit(1);
}