smtp.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

		return Giveup;
	default:
		return Retry;
	}
	return 0;
}

static char hex[] = "0123456789abcdef";

/*
 *  send the damn thing
 */
char *
data(String *from, Biobuf *b)
{
	char *buf, *cp;
	int i, n, nbytes, bufsize, eof, r;
	String *fromline;
	char errmsg[Errlen];
	char id[40];

	/*
	 *  input the header.
	 */

	buf = malloc(1);
	if(buf == 0){
		s_append(s_restart(reply), "out of memory");
		return Retry;
	}
	n = 0;
	eof = 0;
	for(;;){
		cp = Brdline(b, '\n');
		if(cp == nil){
			eof = 1;
			break;
		}
		nbytes = Blinelen(b);
		buf = realloc(buf, n+nbytes+1);
		if(buf == 0){
			s_append(s_restart(reply), "out of memory");
			return Retry;
		}
		strncpy(buf+n, cp, nbytes);
		n += nbytes;
		if(nbytes == 1)		/* end of header */
			break;
	}
	buf[n] = 0;
	bufsize = n;

	/*
	 *  parse the header, turn all addresses into @ format
	 */
	yyinit(buf, n);
	yyparse();

	/*
	 *  print message observing '.' escapes and using \r\n for \n
	 */
	alarm(20*alarmscale);
	if(!filter){
		dBprint("DATA\r\n");
		switch(getreply()){
		case 3:
			break;
		case 5:
			free(buf);
			return Giveup;
		default:
			free(buf);
			return Retry;
		}
	}
	/*
	 *  send header.  add a message-id, a sender, and a date if there
	 *  isn't one
	 */
	nbytes = 0;
	fromline = convertheader(from);
	uneaten = buf;

	srand(truerand());
	if(messageid == 0){
		for(i=0; i<16; i++){
			r = rand()&0xFF;
			id[2*i] = hex[r&0xF];
			id[2*i+1] = hex[(r>>4)&0xF];
		}
		id[2*i] = '\0';
		nbytes += Bprint(&bout, "Message-ID: <%s@%s>\r\n", id, hostdomain);
		if(debug)
			Bprint(&berr, "Message-ID: <%s@%s>\r\n", id, hostdomain);
	}	

	if(originator==0){
		nbytes += Bprint(&bout, "From: %s\r\n", s_to_c(fromline));
		if(debug)
			Bprint(&berr, "From: %s\r\n", s_to_c(fromline));
	}
	s_free(fromline);

	if(destination == 0 && toline)
		if(*s_to_c(toline) == '@'){	/* route addr */
			nbytes += Bprint(&bout, "To: <%s>\r\n", s_to_c(toline));
			if(debug)
				Bprint(&berr, "To: <%s>\r\n", s_to_c(toline));
		} else {
			nbytes += Bprint(&bout, "To: %s\r\n", s_to_c(toline));
			if(debug)
				Bprint(&berr, "To: %s\r\n", s_to_c(toline));
		}

	if(date==0 && udate)
		nbytes += printdate(udate);
	if (usys)
		uneaten = usys->end + 1;
	nbytes += printheader();
	if (*uneaten != '\n')
		putcrnl("\n", 1);

	/*
	 *  send body
	 */
		
	putcrnl(uneaten, buf+n - uneaten);
	nbytes += buf+n - uneaten;
	if(eof == 0){
		for(;;){
			n = Bread(b, buf, bufsize);
			if(n < 0){
				rerrstr(errmsg, sizeof(errmsg));
				s_append(s_restart(reply), errmsg);
				free(buf);
				return Retry;
			}
			if(n == 0)
				break;
			alarm(10*alarmscale);
			putcrnl(buf, n);
			nbytes += n;
		}
	}
	free(buf);
	if(!filter){
		if(last != '\n')
			dBprint("\r\n.\r\n");
		else
			dBprint(".\r\n");
		alarm(10*alarmscale);
		switch(getreply()){
		case 2:
			break;
		case 5:
			return Giveup;
		default:
			return Retry;
		}
		syslog(0, "smtp", "%s sent %d bytes to %s", s_to_c(from),
				nbytes, s_to_c(toline));/**/
	}
	return 0;
}

/*
 *  we're leaving
 */
void
quit(char *rv)
{
		/* 60 minutes to quit */
	quitting = 1;
	quitrv = rv;
	alarm(60*alarmscale);
	dBprint("QUIT\r\n");
	getreply();
	Bterm(&bout);
	Bterm(&bfile);
}

/*
 *  read a reply into a string, return the reply code
 */
int
getreply(void)
{
	char *line;
	int rv;

	reply = s_reset(reply);
	for(;;){
		line = getcrnl(reply);
		if(debug)
			Bflush(&berr);
		if(line == 0)
			return -1;
		if(!isdigit(line[0]) || !isdigit(line[1]) || !isdigit(line[2]))
			return -1;
		if(line[3] != '-')
			break;
	}
	if(debug)
		Bflush(&berr);
	rv = atoi(line)/100;
	return rv;
}
void
addhostdom(String *buf, char *host)
{
	s_append(buf, "@");
	s_append(buf, host);
}

/*
 *	Convert from `bang' to `source routing' format.
 *
 *	   a.x.y!b.p.o!c!d ->	@a.x.y:c!d@b.p.o
 */
String *
bangtoat(char *addr)
{
	String *buf;
	register int i;
	int j, d;
	char *field[128];

	/* parse the '!' format address */
	buf = s_new();
	for(i = 0; addr; i++){
		field[i] = addr;
		addr = strchr(addr, '!');
		if(addr)
			*addr++ = 0;
	}
	if (i==1) {
		s_append(buf, field[0]);
		return buf;
	}

	/*
	 *  count leading domain fields (non-domains don't count)
	 */
	for(d = 0; d<i-1; d++)
		if(strchr(field[d], '.')==0)
			break;
	/*
	 *  if there are more than 1 leading domain elements,
	 *  put them in as source routing
	 */
	if(d > 1){
		addhostdom(buf, field[0]);
		for(j=1; j<d-1; j++){
			s_append(buf, ",");
			s_append(buf, "@");
			s_append(buf, field[j]);
		}
		s_append(buf, ":");
	}

	/*
	 *  throw in the non-domain elements separated by '!'s
	 */
	s_append(buf, field[d]);
	for(j=d+1; j<=i-1; j++) {
		s_append(buf, "!");
		s_append(buf, field[j]);
	}
	if(d)
		addhostdom(buf, field[d-1]);
	return buf;
}

/*
 *  convert header addresses to @ format.
 *  if the address is a source address, and a domain is specified,
 *  make sure it falls in the domain.
 */
String*
convertheader(String *from)
{
	Field *f;
	Node *p, *lastp;
	String *a;

	if(!returnable(s_to_c(from))){
		from = s_new();
		s_append(from, "Postmaster");
		addhostdom(from, hostdomain);
	} else
	if(strchr(s_to_c(from), '@') == 0){
		a = username(from);
		if(a) {
			s_append(a, " <");
			s_append(a, s_to_c(from));
			addhostdom(a, hostdomain);
			s_append(a, ">");
			from = a;
		} else {
			from = s_copy(s_to_c(from));
			addhostdom(from, hostdomain);
		}
	} else
		from = s_copy(s_to_c(from));
	for(f = firstfield; f; f = f->next){
		lastp = 0;
		for(p = f->node; p; lastp = p, p = p->next){
			if(!p->addr)
				continue;
			a = bangtoat(s_to_c(p->s));
			s_free(p->s);
			if(strchr(s_to_c(a), '@') == 0)
				addhostdom(a, hostdomain);
			else if(*s_to_c(a) == '@')
				a = fixrouteaddr(a, p->next, lastp);
			p->s = a;
		}
	}
	return from;
}
/*
 *	ensure route addr has brackets around it
 */
String*
fixrouteaddr(String *raddr, Node *next, Node *last)
{
	String *a;

	if(last && last->c == '<' && next && next->c == '>')
		return raddr;			/* properly formed already */

	a = s_new();
	s_append(a, "<");
	s_append(a, s_to_c(raddr));
	s_append(a, ">");
	s_free(raddr);
	return a;
}

/*
 *  print out the parsed header
 */
int
printheader(void)
{
	int n, len;
	Field *f;
	Node *p;
	char *cp;
	char c[1];

	n = 0;
	for(f = firstfield; f; f = f->next){
		for(p = f->node; p; p = p->next){
			if(p->s)
				n += dBprint("%s", s_to_c(p->s));
			else {
				c[0] = p->c;
				putcrnl(c, 1);
				n++;
			}
			if(p->white){
				cp = s_to_c(p->white);
				len = strlen(cp);
				putcrnl(cp, len);
				n += len;
			}
			uneaten = p->end;
		}
		putcrnl("\n", 1);
		n++;
		uneaten++;		/* skip newline */
	}
	return n;
}

/*
 *  add a domain onto an name, return the new name
 */
char *
domainify(char *name, char *domain)
{
	static String *s;
	char *p;

	if(domain==0 || strchr(name, '.')!=0)
		return name;

	s = s_reset(s);
	s_append(s, name);
	p = strchr(domain, '.');
	if(p == 0){
		s_append(s, ".");
		p = domain;
	}
	s_append(s, p);
	return s_to_c(s);
}

/*
 *  print message observing '.' escapes and using \r\n for \n
 */
void
putcrnl(char *cp, int n)
{
	int c;

	for(; n; n--, cp++){
		c = *cp;
		if(c == '\n')
			dBputc('\r');
		else if(c == '.' && last=='\n')
			dBputc('.');
		dBputc(c);
		last = c;
	}
}

/*
 *  Get a line including a crnl into a string.  Convert crnl into nl.
 */
char *
getcrnl(String *s)
{
	int c;
	int count;

	count = 0;
	for(;;){
		c = Bgetc(&bin);
		if(debug)
			Bputc(&berr, c);
		switch(c){
		case -1:
			s_append(s, "connection closed unexpectedly by remote system");
			s_terminate(s);
			return 0;
		case '\r':
			c = Bgetc(&bin);
			if(c == '\n'){
		case '\n':
				s_putc(s, c);
				if(debug)
					Bputc(&berr, c);
				count++;
				s_terminate(s);
				return s->ptr - count;
			}
			Bungetc(&bin);
			s_putc(s, '\r');
			if(debug)
				Bputc(&berr, '\r');
			count++;
			break;
		default:
			s_putc(s, c);
			count++;
			break;
		}
	}
}

/*
 *  print out a parsed date
 */
int
printdate(Node *p)
{
	int n, sep = 0;

	n = dBprint("Date: %s,", s_to_c(p->s));
	for(p = p->next; p; p = p->next){
		if(p->s){
			if(sep == 0) {
				dBputc(' ');
				n++;
			}
			if (p->next)
				n += dBprint("%s", s_to_c(p->s));
			else
				n += dBprint("%s", rewritezone(s_to_c(p->s)));
			sep = 0;
		} else {
			dBputc(p->c);
			n++;
			sep = 1;
		}
	}
	n += dBprint("\r\n");
	return n;
}

char *
rewritezone(char *z)
{
	int mindiff;
	char s;
	Tm *tm;
	static char x[7];

	tm = localtime(time(0));
	mindiff = tm->tzoff/60;

	/* if not in my timezone, don't change anything */
	if(strcmp(tm->zone, z) != 0)
		return z;

	if(mindiff < 0){
		s = '-';
		mindiff = -mindiff;
	} else
		s = '+';

	sprint(x, "%c%.2d%.2d", s, mindiff/60, mindiff%60);
	return x;
}

/*
 *  stolen from libc/port/print.c
 */
#define	SIZE	4096
int
dBprint(char *fmt, ...)
{
	char buf[SIZE], *out;
	va_list arg;
	int n;

	va_start(arg, fmt);
	out = vseprint(buf, buf+SIZE, fmt, arg);
	va_end(arg);
	if(debug){
		Bwrite(&berr, buf, (long)(out-buf));
		Bflush(&berr);
	}
	n = Bwrite(&bout, buf, (long)(out-buf));
	Bflush(&bout);
	return n;
}

int
dBputc(int x)
{
	if(debug)
		Bputc(&berr, x);
	return Bputc(&bout, x);
}