cs.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

 *  the service '*' needs no translation.
 */
char*
ipserv(Network *np, char *name, char *buf, int blen)
{
	char *p;
	int alpha = 0;
	int restr = 0;
	char port[10];
	Ndbtuple *t, *nt;
	Ndbs s;

	/* '*' means any service */
	if(strcmp(name, "*")==0){
		strcpy(buf, name);
		return buf;
	}

	/*  see if it's numeric or symbolic */
	port[0] = 0;
	for(p = name; *p; p++){
		if(isdigit(*p))
			{}
		else if(isalpha(*p) || *p == '-' || *p == '$')
			alpha = 1;
		else 
			return 0;
	}
	t = nil;
	p = nil;
	if(alpha){
		p = ndbgetvalue(db, &s, np->net, name, "port", &t);
		if(p == nil)
			return 0;
	} else {
		/* look up only for tcp ports < 1024 to get the restricted
		 * attribute
		 */
		if(atoi(name) < 1024 && strcmp(np->net, "tcp") == 0)
			p = ndbgetvalue(db, &s, "port", name, "port", &t);
		if(p == nil)
			p = strdup(name);
	}

	if(t){
		for(nt = t; nt; nt = nt->entry)
			if(strcmp(nt->attr, "restricted") == 0)
				restr = 1;
		ndbfree(t);
	}
	snprint(buf, blen, "%s%s", p, restr ? "!r" : "");
	free(p);

	return buf;
}

/*
 *  lookup an ip attribute
 */
int
ipattrlookup(Ndb *db, char *ipa, char *attr, char *val, int vlen)
{
	
	Ndbtuple *t, *nt;
	char *alist[2];

	alist[0] = attr;
	t = ndbipinfo(db, "ip", ipa, alist, 1);
	if(t == nil)
		return 0;
	for(nt = t; nt != nil; nt = nt->entry){
		if(strcmp(nt->attr, attr) == 0){
			nstrcpy(val, nt->val, vlen);
			ndbfree(t);
			return 1;
		}
	}

	/* we shouldn't get here */
	ndbfree(t);
	return 0;
}

/*
 *  lookup (and translate) an ip destination
 */
Ndbtuple*
iplookup(Network *np, char *host, char *serv, int nolookup)
{
	char *attr, *dnsname;
	Ndbtuple *t, *nt;
	Ndbs s;
	char ts[Maxservice];
	char dollar[Maxhost];
	uchar ip[IPaddrlen];
	uchar net[IPaddrlen];
	uchar tnet[IPaddrlen];
	Ipifc *ifc;
	Iplifc *lifc;

	USED(nolookup);

	/*
	 *  start with the service since it's the most likely to fail
	 *  and costs the least
	 */
	werrstr("can't translate address");
	if(serv==0 || ipserv(np, serv, ts, sizeof ts) == 0){
		werrstr("can't translate service");
		return 0;
	}

	/* for dial strings with no host */
	if(strcmp(host, "*") == 0)
		return ndbnew("ip", "*");

	/*
	 *  hack till we go v6 :: = 0.0.0.0
	 */
	if(strcmp("::", host) == 0)
		return ndbnew("ip", "*");

	/*
	 *  '$' means the rest of the name is an attribute that we
	 *  need to search for
	 */
	if(*host == '$'){
		if(ipattrlookup(db, ipaddr, host+1, dollar, sizeof dollar))
			host = dollar;
	}

	/*
	 *  turn '[ip address]' into just 'ip address'
	 */
	if(*host == '[' && host[strlen(host)-1] == ']'){
		host++;
		host[strlen(host)-1] = 0;
	}

	/*
	 *  just accept addresses
	 */
	attr = ipattr(host);
	if(strcmp(attr, "ip") == 0)
		return ndbnew("ip", host);

	/*
	 *  give the domain name server the first opportunity to
	 *  resolve domain names.  if that fails try the database.
	 */
	t = 0;
	werrstr("can't translate address");
	if(strcmp(attr, "dom") == 0)
		t = dnsiplookup(host, &s);
	if(t == 0)
		free(ndbgetvalue(db, &s, attr, host, "ip", &t));
	if(t == 0){
		dnsname = ndbgetvalue(db, &s, attr, host, "dom", nil);
		if(dnsname){
			t = dnsiplookup(dnsname, &s);
			free(dnsname);
		}
	}
	if(t == 0)
		t = dnsiplookup(host, &s);
	if(t == 0)
		return 0;

	/*
	 *  reorder the tuple to have the matched line first and
	 *  save that in the request structure.
	 */
	t = reorder(t, s.t);

	/*
	 * reorder according to our interfaces
	 */
	lock(&ipifclock);
	for(ifc = ipifcs; ifc != nil; ifc = ifc->next){
		for(lifc = ifc->lifc; lifc != nil; lifc = lifc->next){ 
			maskip(lifc->ip, lifc->mask, net);
			for(nt = t; nt; nt = nt->entry){
				if(strcmp(nt->attr, "ip") != 0)
					continue;
				parseip(ip, nt->val);
				maskip(ip, lifc->mask, tnet);
				if(memcmp(net, tnet, IPaddrlen) == 0){
					t = reorder(t, nt);
					unlock(&ipifclock);
					return t;
				}
			}
		}
	}
	unlock(&ipifclock);

	return t;
}

/*
 *  translate an ip address
 */
char*
iptrans(Ndbtuple *t, Network *np, char *serv, char *rem, int hack)
{
	char ts[Maxservice];
	char reply[Maxreply];
	char x[Maxservice];

	if(strcmp(t->attr, "ip") != 0)
		return 0;

	if(serv == 0 || ipserv(np, serv, ts, sizeof ts) == 0){
		werrstr("can't translate service");
		return 0;
	}
	if(rem != nil)
		snprint(x, sizeof(x), "!%s", rem);
	else
		*x = 0;

	if(*t->val == '*')
		snprint(reply, sizeof(reply), "%s/%s/clone %s%s",
			mntpt, np->net, ts, x);
	else
		snprint(reply, sizeof(reply), "%s/%s/clone %s!%s%s%s",
			mntpt, np->net, t->val, ts, x, hack?"!fasttimeout":"");

	return strdup(reply);
}

/*
 *  lookup a telephone number
 */
Ndbtuple*
telcolookup(Network *np, char *host, char *serv, int nolookup)
{
	Ndbtuple *t;
	Ndbs s;

	USED(np, nolookup, serv);

	werrstr("can't translate address");
	free(ndbgetvalue(db, &s, "sys", host, "telco", &t));
	if(t == 0)
		return ndbnew("telco", host);

	return reorder(t, s.t);
}

/*
 *  translate a telephone address
 */
char*
telcotrans(Ndbtuple *t, Network *np, char *serv, char *rem, int)
{
	char reply[Maxreply];
	char x[Maxservice];

	if(strcmp(t->attr, "telco") != 0)
		return 0;

	if(rem != nil)
		snprint(x, sizeof(x), "!%s", rem);
	else
		*x = 0;
	if(serv)
		snprint(reply, sizeof(reply), "%s/%s/clone %s!%s%s", mntpt, np->net,
			t->val, serv, x);
	else
		snprint(reply, sizeof(reply), "%s/%s/clone %s%s", mntpt, np->net,
			t->val, x);
	return strdup(reply);
}

/*
 *  reorder the tuple to put x's line first in the entry
 */
Ndbtuple*
reorder(Ndbtuple *t, Ndbtuple *x)
{
	Ndbtuple *nt;
	Ndbtuple *line;

	/* find start of this entry's line */
	for(line = x; line->entry == line->line; line = line->line)
		;
	line = line->line;
	if(line == t)
		return t;	/* already the first line */

	/* remove this line and everything after it from the entry */
	for(nt = t; nt->entry != line; nt = nt->entry)
		;
	nt->entry = 0;

	/* make that the start of the entry */
	for(nt = line; nt->entry; nt = nt->entry)
		;
	nt->entry = t;
	return line;
}

/*
 *  create a slave process to handle a request to avoid one request blocking
 *  another.  parent returns to job loop.
 */
void
slave(void)
{
	if(*isslave)
		return;		/* we're already a slave process */

	switch(rfork(RFPROC|RFNOTEG|RFMEM|RFNOWAIT)){
	case -1:
		break;
	case 0:
		if(debug)
			syslog(0, logfile, "slave %d", getpid());
		*isslave = 1;
		break;
	default:
		longjmp(masterjmp, 1);
	}

}

/*
 *  call the dns process and have it try to translate a name
 */
Ndbtuple*
dnsiplookup(char *host, Ndbs *s)
{
	char buf[Maxreply];
	Ndbtuple *t;

	unlock(&dblock);

	/* save the name before starting a slave */
	snprint(buf, sizeof(buf), "%s", host);

	slave();

	if(strcmp(ipattr(buf), "ip") == 0)
		t = dnsquery(mntpt, buf, "ptr");
	else
		t = dnsquery(mntpt, buf, "ip");
	s->t = t;

	if(t == nil){
		rerrstr(buf, sizeof buf);
		if(strstr(buf, "exist"))
			werrstr("can't translate address: %s", buf);
		else if(strstr(buf, "dns failure"))
			werrstr("temporary problem: %s", buf);
	}

	lock(&dblock);
	return t;
}

int
qmatch(Ndbtuple *t, char **attr, char **val, int n)
{
	int i, found;
	Ndbtuple *nt;

	for(i = 1; i < n; i++){
		found = 0;
		for(nt = t; nt; nt = nt->entry)
			if(strcmp(attr[i], nt->attr) == 0)
				if(strcmp(val[i], "*") == 0
				|| strcmp(val[i], nt->val) == 0){
					found = 1;
					break;
				}
		if(found == 0)
			break;
	}
	return i == n;
}

void
qreply(Mfile *mf, Ndbtuple *t)
{
	Ndbtuple *nt;
	String *s;

	s = s_new();
	for(nt = t; mf->nreply < Nreply && nt; nt = nt->entry){
		s_append(s, nt->attr);
		s_append(s, "=");
		s_append(s, nt->val);

		if(nt->line != nt->entry){
			mf->replylen[mf->nreply] = s_len(s);
			mf->reply[mf->nreply++] = strdup(s_to_c(s));
			s_restart(s);
		} else
			s_append(s, " ");
	}
	s_free(s);
}

enum
{
	Maxattr=	32,
};

/*
 *  generic query lookup.  The query is of one of the following
 *  forms:
 *
 *  attr1=val1 attr2=val2 attr3=val3 ...
 *
 *  returns the matching tuple
 *
 *  ipinfo attr=val attr1 attr2 attr3 ...
 *
 *  is like ipinfo and returns the attr{1-n}
 *  associated with the ip address.
 */
char*
genquery(Mfile *mf, char *query)
{
	int i, n;
	char *p;
	char *attr[Maxattr];
	char *val[Maxattr];
	Ndbtuple *t;
	Ndbs s;

	n = getfields(query, attr, 32, 1, " ");
	if(n == 0)
		return "bad query";

	if(strcmp(attr[0], "ipinfo") == 0)
		return ipinfoquery(mf, attr, n);

	/* parse pairs */
	for(i = 0; i < n; i++){
		p = strchr(attr[i], '=');
		if(p == 0)
			return "bad query";
		*p++ = 0;
		val[i] = p;
	}

	/* give dns a chance */
	if((strcmp(attr[0], "dom") == 0 || strcmp(attr[0], "ip") == 0) && val[0]){
		t = dnsiplookup(val[0], &s);
		if(t){
			if(qmatch(t, attr, val, n)){
				qreply(mf, t);
				ndbfree(t);
				return 0;
			}
			ndbfree(t);
		}
	}

	/* first pair is always the key.  It can't be a '*' */
	t = ndbsearch(db, &s, attr[0], val[0]);

	/* search is the and of all the pairs */
	while(t){
		if(qmatch(t, attr, val, n)){
			qreply(mf, t);
			ndbfree(t);
			return 0;
		}

		ndbfree(t);
		t = ndbsnext(&s, attr[0], val[0]);
	}

	return "no match";
}

/*
 *  resolve an ip address
 */
static Ndbtuple*
ipresolve(char *attr, char *host)
{
	Ndbtuple *t, *nt, **l;

	t = iplookup(&network[Ntcp], host, "*", 0);
	for(l = &t; *l != nil; ){
		nt = *l;
		if(strcmp(nt->attr, "ip") != 0){
			*l = nt->entry;
			nt->entry = nil;
			ndbfree(nt);
			continue;
		}
		strcpy(nt->attr, attr);
		l = &nt->entry;
	}
	return t;
}

char*
ipinfoquery(Mfile *mf, char **list, int n)
{
	int i, nresolve;
	int resolve[Maxattr];
	Ndbtuple *t, *nt, **l;
	char *attr, *val;

	/* skip 'ipinfo' */
	list++; n--;

	if(n < 1)
		return "bad query";

	/* get search attribute=value, or assume ip=myipaddr */
	attr = *list;
	if((val = strchr(attr, '=')) != nil){
		*val++ = 0;
		list++;
		n--;
	}else{
		attr = "ip";
		val = ipaddr;
	}

	if(n < 1)
		return "bad query";

	/*
	 *  don't let ndbipinfo resolve the addresses, we're
	 *  better at it.
	 */
	nresolve = 0;
	for(i = 0; i < n; i++)
		if(*list[i] == '@'){
			list[i]++;
			resolve[i] = 1;
			nresolve++;
		} else
			resolve[i] = 0;

	t = ndbipinfo(db, attr, val, list, n);
	if(t == nil)
		return "no match";

	if(nresolve != 0){
		for(l = &t; *l != nil;){
			nt = *l;

			/* already an address? */
			if(strcmp(ipattr(nt->val), "ip") == 0){
				l = &(*l)->entry;
				continue;
			}

			/* user wants it resolved? */
			for(i = 0; i < n; i++)
				if(strcmp(list[i], nt->attr) == 0)
					break;
			if(i >= n || resolve[i] == 0){
				l = &(*l)->entry;
				continue;
			}

			/* resolve address and replace entry */
			*l = ipresolve(nt->attr, nt->val);
			while(*l != nil)
				l = &(*l)->entry;
			*l = nt->entry;

			nt->entry = nil;
			ndbfree(nt);
		}
	}

	/* make it all one line */
	for(nt = t; nt != nil; nt = nt->entry){
		if(nt->entry == nil)
			nt->line = t;
		else
			nt->line = nt->entry;
	}

	qreply(mf, t);

	return nil;
}

void*
emalloc(int size)
{
	void *x;

	x = malloc(size);
	if(x == nil)
		abort();
	memset(x, 0, size);
	return x;
}

char*
estrdup(char *s)
{
	int size;
	char *p;

	size = strlen(s)+1;
	p = malloc(size);
	if(p == nil)
		abort();
	memmove(p, s, size);
	return p;
}