ipifc.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

			v6delroute(f, v6allnodesN, v6allnodesNmask, 1);
		else if(memcmp(lifc->local, v6linklocal, v6llpreflen) == 0)
			/* remove route for all link multicast */
			v6delroute(f, v6allnodesL, v6allnodesLmask, 1);
	}

	free(lifc);
	return nil;

}

/*
 *  remove an address from an interface.
 *  called with c->car locked
 */
char*
ipifcrem(Ipifc *ifc, char **argv, int argc)
{
	uchar ip[IPaddrlen];
	uchar mask[IPaddrlen];
	uchar rem[IPaddrlen];
	Iplifc *lifc;
	char *rv;

	if(argc < 3)
		return Ebadarg;

	parseip(ip, argv[1]);
	parseipmask(mask, argv[2]);
	if(argc < 4)
		maskip(ip, mask, rem);
	else
		parseip(rem, argv[3]);

	wlock(ifc);

	/*
	 *  find address on this interface and remove from chain.
	 *  for pt to pt we actually specify the remote address as the
	 *  addresss to remove.
	 */
	for(lifc = ifc->lifc; lifc != nil; lifc = lifc->next) {
		if (memcmp(ip, lifc->local, IPaddrlen) == 0
		&& memcmp(mask, lifc->mask, IPaddrlen) == 0
		&& memcmp(rem, lifc->remote, IPaddrlen) == 0)
			break;
	}

	rv = ipifcremlifc(ifc, lifc);
	wunlock(ifc);
	return rv;
}

/*
 * distribute routes to active interfaces like the
 * TRIP linecards
 */
void
ipifcaddroute(Fs *f, int vers, uchar *addr, uchar *mask, uchar *gate, int type)
{
	Medium *m;
	Conv **cp, **e;
	Ipifc *ifc;

	e = &f->ipifc->conv[f->ipifc->nc];
	for(cp = f->ipifc->conv; cp < e; cp++){
		if(*cp != nil) {
			ifc = (Ipifc*)(*cp)->ptcl;
			m = ifc->m;
			if(m == nil)
				continue;
			if(m->addroute != nil)
				m->addroute(ifc, vers, addr, mask, gate, type);
		}
	}
}

void
ipifcremroute(Fs *f, int vers, uchar *addr, uchar *mask)
{
	Medium *m;
	Conv **cp, **e;
	Ipifc *ifc;

	e = &f->ipifc->conv[f->ipifc->nc];
	for(cp = f->ipifc->conv; cp < e; cp++){
		if(*cp != nil) {
			ifc = (Ipifc*)(*cp)->ptcl;
			m = ifc->m;
			if(m == nil)
				continue;
			if(m->remroute != nil)
				m->remroute(ifc, vers, addr, mask);
		}
	}
}

/*
 *  associate an address with the interface.  This wipes out any previous
 *  addresses.  This is a macro that means, remove all the old interfaces
 *  and add a new one.
 */
static char*
ipifcconnect(Conv* c, char **argv, int argc)
{
	char *err;
	Ipifc *ifc;

	ifc = (Ipifc*)c->ptcl;

	if(ifc->m == nil)
		 return "ipifc not yet bound to device";

	if(waserror()){
		wunlock(ifc);
		nexterror();
	}
	wlock(ifc);
	while(ifc->lifc){
		err = ipifcremlifc(ifc, ifc->lifc);
		if(err)
			error(err);
	}
	wunlock(ifc);
	poperror();

	err = ipifcadd(ifc, argv, argc, 0, nil);
	if(err)
		return err;

	Fsconnected(c, nil);

	return nil;
}

char*
ipifcsetpar6(Ipifc *ifc, char **argv, int argc)
{
	int i, argsleft, vmax = ifc->rp.maxraint, vmin = ifc->rp.minraint;

	argsleft = argc - 1;
	i = 1;

	if(argsleft % 2 != 0)
		return Ebadarg;

	while (argsleft > 1) {
		if(strcmp(argv[i],"recvra")==0)
			ifc->recvra6 = (atoi(argv[i+1]) != 0);
		else if(strcmp(argv[i],"sendra")==0)
			ifc->sendra6 = (atoi(argv[i+1]) != 0);
		else if(strcmp(argv[i],"mflag")==0)
			ifc->rp.mflag = (atoi(argv[i+1]) != 0);
		else if(strcmp(argv[i],"oflag")==0)
			ifc->rp.oflag = (atoi(argv[i+1]) != 0);
		else if(strcmp(argv[i],"maxraint")==0)
			ifc->rp.maxraint = atoi(argv[i+1]);
		else if(strcmp(argv[i],"minraint")==0)
			ifc->rp.minraint = atoi(argv[i+1]);
		else if(strcmp(argv[i],"linkmtu")==0)
			ifc->rp.linkmtu = atoi(argv[i+1]);
		else if(strcmp(argv[i],"reachtime")==0)
			ifc->rp.reachtime = atoi(argv[i+1]);
		else if(strcmp(argv[i],"rxmitra")==0)
			ifc->rp.rxmitra = atoi(argv[i+1]);
		else if(strcmp(argv[i],"ttl")==0)
			ifc->rp.ttl = atoi(argv[i+1]);
		else if(strcmp(argv[i],"routerlt")==0)
			ifc->rp.routerlt = atoi(argv[i+1]);
		else
			return Ebadarg;

		argsleft -= 2;
		i += 2;
	}

	// consistency check
	if(ifc->rp.maxraint < ifc->rp.minraint) {
		ifc->rp.maxraint = vmax;
		ifc->rp.minraint = vmin;
		return Ebadarg;
	}

	return nil;
}

char*
ipifcsendra6(Ipifc *ifc, char **argv, int argc)
{
	int i;

	i = 0;
	if(argc > 1)
		i = atoi(argv[1]);
	ifc->sendra6 = (i!=0);
	return nil;
}

char*
ipifcrecvra6(Ipifc *ifc, char **argv, int argc)
{
	int i;

	i = 0;
	if(argc > 1)
		i = atoi(argv[1]);
	ifc->recvra6 = (i!=0);
	return nil;
}

/*
 *  non-standard control messages.
 *  called with c->car locked.
 */
static char*
ipifcctl(Conv* c, char**argv, int argc)
{
	Ipifc *ifc;
	int i;

	ifc = (Ipifc*)c->ptcl;
	if(strcmp(argv[0], "add") == 0)
		return ipifcadd(ifc, argv, argc, 0, nil);
	else if(strcmp(argv[0], "try") == 0)
		return ipifcadd(ifc, argv, argc, 1, nil);
	else if(strcmp(argv[0], "remove") == 0)
		return ipifcrem(ifc, argv, argc);
	else if(strcmp(argv[0], "unbind") == 0)
		return ipifcunbind(ifc);
	else if(strcmp(argv[0], "joinmulti") == 0)
		return ipifcjoinmulti(ifc, argv, argc);
	else if(strcmp(argv[0], "leavemulti") == 0)
		return ipifcleavemulti(ifc, argv, argc);
	else if(strcmp(argv[0], "mtu") == 0)
		return ipifcsetmtu(ifc, argv, argc);
	else if(strcmp(argv[0], "reassemble") == 0){
		ifc->reassemble = 1;
		return nil;
	}
	else if(strcmp(argv[0], "iprouting") == 0){
		i = 1;
		if(argc > 1)
			i = atoi(argv[1]);
		iprouting(c->p->f, i);
		return nil;
	}
	else if(strcmp(argv[0], "addpref6") == 0)
		return ipifcaddpref6(ifc, argv, argc);
	else if(strcmp(argv[0], "setpar6") == 0)
		return ipifcsetpar6(ifc, argv, argc);
	else if(strcmp(argv[0], "sendra6") == 0)
		return ipifcsendra6(ifc, argv, argc);
	else if(strcmp(argv[0], "recvra6") == 0)
		return ipifcrecvra6(ifc, argv, argc);
	return "unsupported ctl";
}

int
ipifcstats(Proto *ipifc, char *buf, int len)
{
	return ipstats(ipifc->f, buf, len);
}

void
ipifcinit(Fs *f)
{
	Proto *ipifc;

	ipifc = smalloc(sizeof(Proto));
	ipifc->name = "ipifc";
	ipifc->connect = ipifcconnect;
	ipifc->announce = nil;
	ipifc->bind = ipifcbind;
	ipifc->state = ipifcstate;
	ipifc->create = ipifccreate;
	ipifc->close = ipifcclose;
	ipifc->rcv = nil;
	ipifc->ctl = ipifcctl;
	ipifc->advise = nil;
	ipifc->stats = ipifcstats;
	ipifc->inuse = ipifcinuse;
	ipifc->local = ipifclocal;
	ipifc->ipproto = -1;
	ipifc->nc = Maxmedia;
	ipifc->ptclsize = sizeof(Ipifc);

	f->ipifc = ipifc;			/* hack for ipifcremroute, findipifc, ... */
	f->self = smalloc(sizeof(Ipselftab));	/* hack for ipforme */

	Fsproto(f, ipifc);
}

/*
 *  add to self routing cache
 *	called with c->car locked
 */
static void
addselfcache(Fs *f, Ipifc *ifc, Iplifc *lifc, uchar *a, int type)
{
	Ipself *p;
	Iplink *lp;
	int h;

	qlock(f->self);

	/* see if the address already exists */
	h = hashipa(a);
	for(p = f->self->hash[h]; p; p = p->next)
		if(memcmp(a, p->a, IPaddrlen) == 0)
			break;

	/* allocate a local address and add to hash chain */
	if(p == nil){
		p = smalloc(sizeof(*p));
		ipmove(p->a, a);
		p->type = type;
		p->next = f->self->hash[h];
		f->self->hash[h] = p;

		/* if the null address, accept all packets */
		if(ipcmp(a, v4prefix) == 0 || ipcmp(a, IPnoaddr) == 0)
			f->self->acceptall = 1;
	}

	/* look for a link for this lifc */
	for(lp = p->link; lp; lp = lp->selflink)
		if(lp->lifc == lifc)
			break;

	/* allocate a lifc-to-local link and link to both */
	if(lp == nil){
		lp = smalloc(sizeof(*lp));
		lp->ref = 1;
		lp->lifc = lifc;
		lp->self = p;
		lp->selflink = p->link;
		p->link = lp;
		lp->lifclink = lifc->link;
		lifc->link = lp;

		/* add to routing table */
		if(isv4(a))
			v4addroute(f, tifc, a+IPv4off, IPallbits+IPv4off, a+IPv4off, type);
		else
			v6addroute(f, tifc, a, IPallbits, a, type);

		if((type & Rmulti) && ifc->m->addmulti != nil)
			(*ifc->m->addmulti)(ifc, a, lifc->local);
	} else {
		lp->ref++;
	}

	qunlock(f->self);
}

/*
 *  These structures are unlinked from their chains while
 *  other threads may be using them.  To avoid excessive locking,
 *  just put them aside for a while before freeing them.
 *	called with f->self locked
 */
static Iplink *freeiplink;
static Ipself *freeipself;

static void
iplinkfree(Iplink *p)
{
	Iplink **l, *np;
	ulong now = NOW;

	l = &freeiplink;
	for(np = *l; np; np = *l){
		if(np->expire > now){
			*l = np->next;
			free(np);
			continue;
		}
		l = &np->next;
	}
	p->expire = now + 5000;		/* give other threads 5 secs to get out */
	p->next = nil;
	*l = p;
}
static void
ipselffree(Ipself *p)
{
	Ipself **l, *np;
	ulong now = NOW;

	l = &freeipself;
	for(np = *l; np; np = *l){
		if(np->expire > now){
			*l = np->next;
			free(np);
			continue;
		}
		l = &np->next;
	}
	p->expire = now + 5000;		/* give other threads 5 secs to get out */
	p->next = nil;
	*l = p;
}

/*
 *  Decrement reference for this address on this link.
 *  Unlink from selftab if this is the last ref.
 *	called with c->car locked
 */
static void
remselfcache(Fs *f, Ipifc *ifc, Iplifc *lifc, uchar *a)
{
	Ipself *p, **l;
	Iplink *link, **l_self, **l_lifc;

	qlock(f->self);

	/* find the unique selftab entry */
	l = &f->self->hash[hashipa(a)];
	for(p = *l; p; p = *l){
		if(ipcmp(p->a, a) == 0)
			break;
		l = &p->next;
	}

	if(p == nil)
		goto out;

	/*
	 *  walk down links from an ifc looking for one
	 *  that matches the selftab entry
	 */
	l_lifc = &lifc->link;
	for(link = *l_lifc; link; link = *l_lifc){
		if(link->self == p)
			break;
		l_lifc = &link->lifclink;
	}

	if(link == nil)
		goto out;

	/*
	 *  walk down the links from the selftab looking for
	 *  the one we just found
	 */
	l_self = &p->link;
	for(link = *l_self; link; link = *l_self){
		if(link == *(l_lifc))
			break;
		l_self = &link->selflink;
	}

	if(link == nil)
		panic("remselfcache");

	if(--(link->ref) != 0)
		goto out;

	if((p->type & Rmulti) && ifc->m->remmulti != nil)
		(*ifc->m->remmulti)(ifc, a, lifc->local);

	/* ref == 0, remove from both chains and free the link */
	*l_lifc = link->lifclink;
	*l_self = link->selflink;
	iplinkfree(link);

	if(p->link != nil)
		goto out;

	/* remove from routing table */
	if(isv4(a))
		v4delroute(f, a+IPv4off, IPallbits+IPv4off, 1);
	else
		v6delroute(f, a, IPallbits, 1);

	/* no more links, remove from hash and free */
	*l = p->next;
	ipselffree(p);

	/* if IPnoaddr, forget */
	if(ipcmp(a, v4prefix) == 0 || ipcmp(a, IPnoaddr) == 0)
		f->self->acceptall = 0;

out:
	qunlock(f->self);
}

static char *stformat = "%-44.44I %2.2d %4.4s\n";
enum
{
	Nstformat= 41,
};

long
ipselftabread(Fs *f, char *cp, ulong offset, int n)
{
	int i, m, nifc, off;
	Ipself *p;
	Iplink *link;
	char state[8];

	m = 0;
	off = offset;
	qlock(f->self);
	for(i = 0; i < NHASH && m < n; i++){
		for(p = f->self->hash[i]; p != nil && m < n; p = p->next){
			nifc = 0;
			for(link = p->link; link; link = link->selflink)
				nifc++;
			routetype(p->type, state);
			m += snprint(cp + m, n - m, stformat, p->a, nifc, state);
			if(off > 0){
				off -= m;
				m = 0;
			}
		}
	}
	qunlock(f->self);
	return m;
}

int
iptentative(Fs *f, uchar *addr)
{
 	Ipself *p;

	p = f->self->hash[hashipa(addr)];
	for(; p; p = p->next){
		if(ipcmp(addr, p->a) == 0) {
			return p->link->lifc->tentative;
		}
	}
	return 0;
}

/*
 *  returns
 *	0		- no match
 *	Runi
 *	Rbcast
 *	Rmcast
 */
int
ipforme(Fs *f, uchar *addr)
{
	Ipself *p;

	p = f->self->hash[hashipa(addr)];
	for(; p; p = p->next){
		if(ipcmp(addr, p->a) == 0)
			return p->type;
	}

	/* hack to say accept anything */
	if(f->self->acceptall)
		return Runi;

	return 0;
}

/*
 *  find the ifc on same net as the remote system.  If none,
 *  return nil.
 */
Ipifc*
findipifc(Fs *f, uchar *remote, int type)
{
	Ipifc *ifc, *x;
	Iplifc *lifc;
	Conv **cp, **e;
	uchar gnet[IPaddrlen];
	uchar xmask[IPaddrlen];