lpdaemon.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

#include <sys/types.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <signal.h>
#include <errno.h>
#include <time.h>
#include <string.h>
#include <stdarg.h>

/* for Plan 9 */
#ifdef PLAN9
#define LP	"/bin/lp"
#define TMPDIR "/sys/lib/lp/tmp"
#define LPDAEMONLOG	"/sys/lib/lp/log/lpdaemonl"
#endif
/* for Tenth Edition systems */
#ifdef V10
#define LP	"/usr/bin/lp"
#define TMPDIR "/tmp"
#define LPDAEMONLOG	"/tmp/lpdaemonl"
#endif
/* for System V or BSD systems */
#if defined(SYSV) || defined(BSD)
#define LP	"/v/bin/lp"
#define TMPDIR "/tmp"
#define LPDAEMONLOG	"/tmp/lpdaemonl"
#endif

#define ARGSIZ 4096
#define NAMELEN 30

unsigned char argvstr[ARGSIZ];		/* arguments after parsing */
unsigned char *argvals[ARGSIZ/2+1];	/* pointers to arguments after parsing */
int ascnt = 0, argcnt = 0;	/* number of arguments parsed */
/* for 'stuff' gleened from lpr cntrl file */
struct jobinfo {
	char user[NAMELEN+1];
	char host[NAMELEN+1];
} *getjobinfo();

#define MIN(a,b)	((a<b)?a:b)

#define	CPYFIELD(src, dst)	{ while (*(src)!=' ' && *(src)!='\t' && *(src)!='\r' && *(src)!='\n' && *(src)!='\0') *(dst)++ = *(src)++; }

#define	ACK()	write(1, "", 1)
#define NAK()	write(1, "\001", 1)

#define LNBFSZ	4096
unsigned char lnbuf[LNBFSZ];

#define	RDSIZE 512
unsigned char jobbuf[RDSIZE];

int datafd[400], cntrlfd = -1;

int dbgstate = 0;
char *dbgstrings[] = {
	"",
	"sendack1",
	"send",
	"rcvack",
	"sendack2",
	"done"
};

void
error(char *s1, ...)
{
	FILE *fp;
	long thetime;
	char *chartime;
	va_list ap;
	char *args[8];
	int argno = 0;

	if((fp=fopen(LPDAEMONLOG, "a"))==NULL) {
		fprintf(stderr, "cannot open %s in append mode\n", LPDAEMONLOG);
		return;
	}
	time(&thetime);
	chartime = ctime(&thetime);
	fprintf(fp, "%.15s [%5.5d] ", &(chartime[4]), getpid());
	va_start(ap, s1);
	while((args[argno++] = va_arg(ap, char*)) && argno<8);
	va_end(ap);
	fprintf(fp, s1, args[0], args[1], args[2], args[3], args[4], args[5], args[6], args[7]);
	fflush(fp);
	fclose(fp);
	return;
}

void
forklp(int inputfd)
{
	int i, cpid;
	unsigned char *bp, *cp;
	unsigned char logent[LNBFSZ];

	/* log this call to lp */
	cp = logent;
	for (i=1; i<argcnt; i++) {
		bp = argvals[i];
		if (cp+strlen((const char *)bp)+1 < logent+LNBFSZ-1) {
			CPYFIELD(bp, cp);
			*cp++ = ' ';
		}
	}
	*--cp = '\n';
	*++cp = '\0';
	error((const char *)logent);
	switch((cpid=fork())){
	case -1:
		error("fork error\n");
		exit(2);
	case 0:
		if (inputfd != 0)
			dup2(inputfd, 0);
		dup2(1, 2);
		lseek(0, 0L, 0);
		execvp(LP, (const char **)argvals);
		error("exec failed\n");
		exit(3);
	default:
		while(wait((int *)0) != cpid);
	}
}

int
tempfile(void)
{
	static tindx = 0;
	char tmpf[sizeof(TMPDIR)+64];
	int crtfd, tmpfd;

	sprintf(tmpf, "%s/lp%d.%d", TMPDIR, getpid(), tindx++);
	if((crtfd=creat(tmpf, 0666)) < 0) {
		error("cannot create temp file %s\n", tmpf);
		NAK();
		exit(3);
	}
	if((tmpfd=open(tmpf, 2)) < 0) {
		error("cannot open temp file %s\n", tmpf);
		NAK();
		exit(3);
	}
	close(crtfd);
	unlink(tmpf);	/* comment out for debugging */
	return(tmpfd);
}

int
readfile(int outfd, int bsize)
{
	int rv;

	dbgstate = 1;
	alarm(60);
	ACK();
	dbgstate = 2;
	for(; bsize > 0; bsize -= rv) {
		alarm(60);
		if((rv=read(0, jobbuf, MIN(bsize,RDSIZE))) < 0) {
			error("error reading input, %d unread\n", bsize);
			exit(4);
		} else if (rv == 0) {
			error("connection closed prematurely\n");
			exit(4);
		} else if((write(outfd, jobbuf, rv)) != rv) {
			error("error writing temp file, %d unread\n", bsize);
			exit(5);
		}
	}
	dbgstate = 3;
	alarm(60);
	if (((rv=read(0, jobbuf, 1))==1) && (*jobbuf=='\0')) {
		alarm(60);
		ACK();
		dbgstate = 4;
		alarm(0);
		return(outfd);
	}
	alarm(0);
	error("received bad status <%d> from sender\n", *jobbuf);
	error("rv=%d\n", rv);
	NAK();
	return(-1);
}

/* reads a line from the input into lnbuf
 * if there is no error, it returns
 *   the number of characters in the buffer
 * if there is an error and there where characters
 *   read, it returns the negative value of the
 *   number of characters read
 * if there is an error and no characters were read,
 *   it returns the negative value of 1 greater than
 *   the size of the line buffer
 */
int
readline(int inpfd)
{
	unsigned char *ap;
	int i, rv;

	ap = lnbuf;
	lnbuf[0] = '\0';
	i = 0;
	alarm(60);
	do {
		rv = read(inpfd, ap, 1);
	} while (rv==1 && ++i && *ap != '\n' && ap++ && (i < LNBFSZ - 2));
	alarm(0);
	if (i != 0 && *ap != '\n') {
		*++ap = '\n';
		i++;
	}
	*++ap = '\0';
	if (rv < 0) {
		error("read error; lost connection\n");
		if (i==0) i = -(LNBFSZ+1);
		else i = -i;
	}
	return(i);
}

int
getfiles(void)
{
	unsigned char *ap;
	int filecnt, bsize, rv;

	filecnt = 0;
	/* get a line, hopefully containing a ctrl char, size, and name */
	for(;;) {
		ap = lnbuf;
		if ((rv=readline(0)) < 0) NAK();
		if (rv <= 0) {
			return(filecnt);
		}
		switch(*ap++) {
		case '\1':		/* cleanup - data sent was bad (whatever that means) */
			break;
		case '\2':		/* read control file */
			bsize = atoi((const char *)ap);
			cntrlfd = tempfile();
			if (readfile(cntrlfd, bsize) < 0) {
				close(cntrlfd);
				NAK();
				return(0);
			}
			break;
		case '\3':		/* read data file */
			bsize = atoi((const char *)ap);
			datafd[filecnt] = tempfile();
			if (readfile(datafd[filecnt], bsize) < 0) {
				close(datafd[filecnt]);
				NAK();
				return(0);
			}
			filecnt++;
			break;
		default:
			error("protocol error <%d>\n", *(ap-1));
			NAK();
		}
	}
	return(filecnt);
}

struct jobinfo *
getjobinfo(int fd)
{
	unsigned char *ap;
	int rv;
	static struct jobinfo info;

	if (fd < 0) error("getjobinfo: bad file descriptor\n");
	if (lseek(fd, 0L, 0) < 0) {
		error("error seeking in temp file\n");
		exit(7);
	}
	/* the following strings should be < NAMELEN or else they will not
	 * be null terminated.
	 */
	strncpy(info.user, "daemon", NAMELEN);
	strncpy(info.host, "nowhere", NAMELEN);
	/* there may be a space after the name and host.  It will be filtered out
	 * by CPYFIELD.
	 */
	while ((rv=readline(fd)) > 0) {
		ap = lnbuf;
		ap[rv-1] = '\0';	/* remove newline from string */
		switch (*ap) {
		case 'H':
			if (ap[1] == '\0')
				strncpy(info.host, "unknown", NAMELEN);
			else
				strncpy(info.host, (const char *)&ap[1], NAMELEN);
			info.host[strlen(info.host)] = '\0';
			break;
		case 'P':
			if (ap[1] == '\0')
				strncpy(info.user, "unknown", NAMELEN);
			else
				strncpy(info.user, (const char *)&ap[1], NAMELEN);
			info.user[strlen(info.user)] = '\0';
			break;
		}
	}
	return(&info);
}

void
alarmhandler(int sig) {
	signal(sig, alarmhandler);
	error("alarm at %d - %s\n", dbgstate, dbgstrings[dbgstate]);
}

main()
{
	unsigned char *ap, *bp, *cp, *savbufpnt;
	int i, blen, rv, saveflg, savargcnt;
	struct jobinfo *jinfop;

	signal(1, SIG_IGN);		/* SIGHUP not in lcc */
	signal(14, alarmhandler);	/* SIGALRM not in lcc */
	cp = argvstr;
	/* setup argv[0] for exec */
	argvals[argcnt++] = cp;
	for (bp = (unsigned char *)LP, i = 0; (*bp != '\0') && (i < ARGSIZ-1); *cp++ = *bp++, i++);
	*cp++ = '\0';
	/* get the first line sent and parse it as arguments for lp */
	if ((rv=readline(0)) < 0)
		exit(1);
	bp = lnbuf;
	/* setup the remaining arguments */
	/* check for BSD style request */
	/* ^A, ^B, ^C, ^D, ^E (for BSD lpr) */
	switch (*bp) {
	case '\001':
	case '\003':
	case '\004':
		bp++;	/* drop the ctrl character from the input */
		argvals[argcnt++] = cp;
		*cp++ = '-'; *cp++ = 'q'; *cp++ = '\0';		/* -q */
		argvals[argcnt++] = cp;
		*cp++ = '-'; *cp++ = 'd'; 			/* -d */
		CPYFIELD(bp, cp);				/* printer */
		*cp++ = '\0';
		break;
	case '\002':
		bp++;	/* drop the ctrl character from the input */
		argvals[argcnt++] = cp;
		*cp++ = '-'; *cp++ = 'd'; 			/* -d */
		CPYFIELD(bp, cp);				/* printer */
		*cp++ = '\0';
		ACK();
		savargcnt = argcnt;
		savbufpnt = cp;
		while ((rv=getfiles())) {
			jinfop = getjobinfo(cntrlfd);
			close(cntrlfd);
			argcnt = savargcnt;
			cp = savbufpnt;
			argvals[argcnt++] = cp;
			*cp++ = '-'; *cp++ = 'M'; 			/* -M */
			bp = (unsigned char *)jinfop->host;
			CPYFIELD(bp, cp);				/* host name */
			*cp++ = '\0';
			argvals[argcnt++] = cp;
			*cp++ = '-'; *cp++ = 'u'; 			/* -u */
			bp = (unsigned char *)jinfop->user;
			CPYFIELD(bp, cp);				/* user name */
			*cp++ = '\0';
			for(i=0;i<rv;i++)
				forklp(datafd[i]);
		}
		exit(0);
	case '\005':
		bp++;	/* drop the ctrl character from the input */
		argvals[argcnt++] = cp;
		*cp++ = '-'; *cp++ = 'k'; *cp++ = '\0';		/* -k */
		argvals[argcnt++] = cp;
		*cp++ = '-'; *cp++ = 'd'; 			/* -d */
		CPYFIELD(bp, cp);				/* printer */
		*cp++ = '\0';
		argvals[argcnt++] = cp;
		*cp++ = '-'; ap = cp; *cp++ = 'u'; 		/* -u */
		CPYFIELD(bp, cp);				/* username */

		/* deal with bug in lprng where the username is not supplied
		 */
		if (ap == (cp-1)) {
			ap = (unsigned char *)"none";
			CPYFIELD(ap, cp);
		}

		*cp++ = '\0';
		datafd[0] = tempfile();
		blen = strlen((const char *)bp);
		if (write(datafd[0], bp, blen) != blen) {
			error("write error\n");
			exit(6);
		}
		if (write(datafd[0], "\n", 1) != 1) {
			error("write error\n");
			exit(6);
		}
		break;
	default:
		/* otherwise get my lp arguments */
		do {
			/* move to next non-white space */
			while (*bp==' '||*bp=='\t')
				++bp;
			if (*bp=='\n') continue;
			/* only accept arguments beginning with -
			 * this is done to prevent the printing of
			 * local files from the destination host
			 */
			if (*bp=='-') {
				argvals[argcnt++] = cp;
				saveflg = 1;
			} else
				saveflg = 0;
			/* move to next white space copying text to argument buffer */
			while (*bp!=' ' && *bp!='\t' && *bp!='\n'
			    && *bp!='\0') {
				*cp = *bp++;
				cp += saveflg;
			}
			*cp = '\0';
			cp += saveflg;
		} while (*bp!='\n' && *bp!='\0');
		if (readline(0) < 0) exit(7);
		datafd[0] = tempfile();
		if(readfile(datafd[0], atoi((const char *)lnbuf)) < 0) {
			error("readfile failed\n");
			exit(8);
		}
	}
	forklp(datafd[0]);
	exit(0);
}