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

#include "u.h"
#include "../port/lib.h"
#include "mem.h"
#include "dat.h"
#include "fns.h"
#include "../port/error.h"

#include "ip.h"
#include "ipv6.h"

#define DPRINT if(0)print

enum {
	Maxmedia	= 32,
	Nself		= Maxmedia*5,
	NHASH		= (1<<6),
	NCACHE		= 256,
	QMAX		= 64*1024-1,
};

Medium *media[Maxmedia] =
{
	0
};

/*
 *  cache of local addresses (addresses we answer to)
 */
struct Ipself
{
	uchar	a[IPaddrlen];
	Ipself	*hnext;		/* next address in the hash table */
	Iplink	*link;		/* binding twixt Ipself and Ipifc */
	ulong	expire;
	uchar	type;		/* type of address */
	int	ref;
	Ipself	*next;		/* free list */
};

struct Ipselftab
{
	QLock;
	int	inited;
	int	acceptall;	/* true if an interface has the null address */
	Ipself	*hash[NHASH];	/* hash chains */
};

/*
 *  Multicast addresses are chained onto a Chan so that
 *  we can remove them when the Chan is closed.
 */
typedef struct Ipmcast Ipmcast;
struct Ipmcast
{
	Ipmcast	*next;
	uchar	ma[IPaddrlen];	/* multicast address */
	uchar	ia[IPaddrlen];	/* interface address */
};

/* quick hash for ip addresses */
#define hashipa(a) ( ( ((a)[IPaddrlen-2]<<8) | (a)[IPaddrlen-1] )%NHASH )

static char tifc[] = "ifc ";

static void	addselfcache(Fs *f, Ipifc *ifc, Iplifc *lifc, uchar *a, int type);
static void	remselfcache(Fs *f, Ipifc *ifc, Iplifc *lifc, uchar *a);
static char*	ipifcjoinmulti(Ipifc *ifc, char **argv, int argc);
static char*	ipifcleavemulti(Ipifc *ifc, char **argv, int argc);
static void	ipifcregisterproxy(Fs*, Ipifc*, uchar*);
static char*	ipifcremlifc(Ipifc*, Iplifc*);

/*
 *  link in a new medium
 */
void
addipmedium(Medium *med)
{
	int i;

	for(i = 0; i < nelem(media)-1; i++)
		if(media[i] == nil){
			media[i] = med;
			break;
		}
}

/*
 *  find the medium with this name
 */
Medium*
ipfindmedium(char *name)
{
	Medium **mp;

	for(mp = media; *mp != nil; mp++)
		if(strcmp((*mp)->name, name) == 0)
			break;
	return *mp;
}

/*
 *  attach a device (or pkt driver) to the interface.
 *  called with c locked
 */
static char*
ipifcbind(Conv *c, char **argv, int argc)
{
	Ipifc *ifc;
	Medium *m;

	if(argc < 2)
		return Ebadarg;

	ifc = (Ipifc*)c->ptcl;

	/* bind the device to the interface */
	m = ipfindmedium(argv[1]);
	if(m == nil)
		return "unknown interface type";

	wlock(ifc);
	if(ifc->m != nil){
		wunlock(ifc);
		return "interface already bound";
	}
	if(waserror()){
		wunlock(ifc);
		nexterror();
	}

	/* do medium specific binding */
	(*m->bind)(ifc, argc, argv);

	/* set the bound device name */
	if(argc > 2)
		strncpy(ifc->dev, argv[2], sizeof(ifc->dev));
	else
		sprint(ifc->dev, "%s%d", m->name, c->x);
	ifc->dev[sizeof(ifc->dev)-1] = 0;

	/* set up parameters */
	ifc->m = m;
	ifc->mintu = ifc->m->mintu;
	ifc->maxtu = ifc->m->maxtu;
	if(ifc->m->unbindonclose == 0)
		ifc->conv->inuse++;
	ifc->rp.mflag = 0;		// default not managed
	ifc->rp.oflag = 0;
	ifc->rp.maxraint = 600000;	// millisecs
	ifc->rp.minraint = 200000;
	ifc->rp.linkmtu = 0;		// no mtu sent
	ifc->rp.reachtime = 0;
	ifc->rp.rxmitra = 0;
	ifc->rp.ttl = MAXTTL;
	ifc->rp.routerlt = 3*(ifc->rp.maxraint);

	/* any ancillary structures (like routes) no longer pertain */
	ifc->ifcid++;

	/* reopen all the queues closed by a previous unbind */
	qreopen(c->rq);
	qreopen(c->eq);
	qreopen(c->sq);

	wunlock(ifc);
	poperror();

	return nil;
}

/*
 *  detach a device from an interface, close the interface
 *  called with ifc->conv closed
 */
static char*
ipifcunbind(Ipifc *ifc)
{
	char *err;

	if(waserror()){
		wunlock(ifc);
		nexterror();
	}
	wlock(ifc);

	/* dissociate routes */
	if(ifc->m != nil && ifc->m->unbindonclose == 0)
		ifc->conv->inuse--;
	ifc->ifcid++;

	/* disassociate device */
	if(ifc->m != nil && ifc->m->unbind)
		(*ifc->m->unbind)(ifc);
	memset(ifc->dev, 0, sizeof(ifc->dev));
	ifc->arg = nil;
	ifc->reassemble = 0;

	/* close queues to stop queuing of packets */
	qclose(ifc->conv->rq);
	qclose(ifc->conv->wq);
	qclose(ifc->conv->sq);

	/* disassociate logical interfaces */
	while(ifc->lifc){
		err = ipifcremlifc(ifc, ifc->lifc);
		if(err)
			error(err);
	}

	ifc->m = nil;
	wunlock(ifc);
	poperror();
	return nil;
}

char sfixedformat[] = "device %s maxtu %d sendra %d recvra %d mflag %d oflag %d maxraint %d minraint %d linkmtu %d reachtime %d rxmitra %d ttl %d routerlt %d pktin %lud pktout %lud errin %lud errout %lud\n";

char slineformat[] = "	%-40I %-10M %-40I %-12lud %-12lud\n";

static int
ipifcstate(Conv *c, char *state, int n)
{
	Ipifc *ifc;
	Iplifc *lifc;
	int m;

	ifc = (Ipifc*)c->ptcl;

	m = snprint(state, n, sfixedformat,
		ifc->dev, ifc->maxtu, ifc->sendra6, ifc->recvra6,
		ifc->rp.mflag, ifc->rp.oflag, ifc->rp.maxraint,
		ifc->rp.minraint, ifc->rp.linkmtu, ifc->rp.reachtime,
		ifc->rp.rxmitra, ifc->rp.ttl, ifc->rp.routerlt,
		ifc->in, ifc->out, ifc->inerr, ifc->outerr);

	rlock(ifc);
	for(lifc = ifc->lifc; lifc && n > m; lifc = lifc->next)
		m += snprint(state+m, n - m, slineformat,
			lifc->local, lifc->mask, lifc->remote,
			lifc->validlt, lifc->preflt);
	if(ifc->lifc == nil)
		m += snprint(state+m, n - m, "\n");
	runlock(ifc);
	return m;
}

static int
ipifclocal(Conv *c, char *state, int n)
{
	Ipifc *ifc;
	Iplifc *lifc;
	Iplink *link;
	int m;

	ifc = (Ipifc*)c->ptcl;

	m = 0;

	rlock(ifc);
	for(lifc = ifc->lifc; lifc; lifc = lifc->next){
		m += snprint(state+m, n - m, "%-40.40I ->", lifc->local);
		for(link = lifc->link; link; link = link->lifclink)
			m += snprint(state+m, n - m, " %-40.40I", link->self->a);
		m += snprint(state+m, n - m, "\n");
	}
	runlock(ifc);
	return m;
}

static int
ipifcinuse(Conv *c)
{
	Ipifc *ifc;

	ifc = (Ipifc*)c->ptcl;
	return ifc->m != nil;
}

/*
 *  called when a process writes to an interface's 'data'
 */
static void
ipifckick(void *x)
{
	Conv *c = x;
	Block *bp;
	Ipifc *ifc;

	bp = qget(c->wq);
	if(bp == nil)
		return;

	ifc = (Ipifc*)c->ptcl;
	if(!canrlock(ifc)){
		freeb(bp);
		return;
	}
	if(waserror()){
		runlock(ifc);
		nexterror();
	}
	if(ifc->m == nil || ifc->m->pktin == nil)
		freeb(bp);
	else
		(*ifc->m->pktin)(c->p->f, ifc, bp);
	runlock(ifc);
	poperror();
}

/*
 *  called when a new ipifc structure is created
 */
static void
ipifccreate(Conv *c)
{
	Ipifc *ifc;

	c->rq = qopen(QMAX, 0, 0, 0);
	c->sq = qopen(2*QMAX, 0, 0, 0);
	c->wq = qopen(QMAX, Qkick, ipifckick, c);
	ifc = (Ipifc*)c->ptcl;
	ifc->conv = c;
	ifc->unbinding = 0;
	ifc->m = nil;
	ifc->reassemble = 0;
}

/*
 *  called after last close of ipifc data or ctl
 *  called with c locked, we must unlock
 */
static void
ipifcclose(Conv *c)
{
	Ipifc *ifc;
	Medium *m;

	ifc = (Ipifc*)c->ptcl;
	m = ifc->m;
	if(m != nil && m->unbindonclose)
		ipifcunbind(ifc);
}

/*
 *  change an interface's mtu
 */
char*
ipifcsetmtu(Ipifc *ifc, char **argv, int argc)
{
	int mtu;

	if(argc < 2)
		return Ebadarg;
	if(ifc->m == nil)
		return Ebadarg;
	mtu = strtoul(argv[1], 0, 0);
	if(mtu < ifc->m->mintu || mtu > ifc->m->maxtu)
		return Ebadarg;
	ifc->maxtu = mtu;
	return nil;
}

/*
 *  add an address to an interface.
 */
char*
ipifcadd(Ipifc *ifc, char **argv, int argc, int tentative, Iplifc *lifcp)
{
	uchar ip[IPaddrlen], mask[IPaddrlen], rem[IPaddrlen];
	uchar bcast[IPaddrlen], net[IPaddrlen];
	Iplifc *lifc, **l;
	int i, type, mtu;
	Fs *f;
	int sendnbrdisc = 0;

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

	f = ifc->conv->p->f;

	type = Rifc;
	memset(ip, 0, IPaddrlen);
	memset(mask, 0, IPaddrlen);
	memset(rem, 0, IPaddrlen);
	switch(argc){
	case 6:
		if(strcmp(argv[5], "proxy") == 0)
			type |= Rproxy;
		/* fall through */
	case 5:
		mtu = strtoul(argv[4], 0, 0);
		if(mtu >= ifc->m->mintu && mtu <= ifc->m->maxtu)
			ifc->maxtu = mtu;
		/* fall through */
	case 4:
		parseip(ip, argv[1]);
		parseipmask(mask, argv[2]);
		parseip(rem, argv[3]);
		maskip(rem, mask, net);
		break;
	case 3:
		parseip(ip, argv[1]);
		parseipmask(mask, argv[2]);
		maskip(ip, mask, rem);
		maskip(rem, mask, net);
		break;
	case 2:
		parseip(ip, argv[1]);
		memmove(mask, defmask(ip), IPaddrlen);
		maskip(ip, mask, rem);
		maskip(rem, mask, net);
		break;
	default:
		return Ebadarg;
		break;
	}
	if(isv4(ip))
		tentative = 0;
	wlock(ifc);

	/* ignore if this is already a local address for this ifc */
	for(lifc = ifc->lifc; lifc; lifc = lifc->next) {
		if(ipcmp(lifc->local, ip) == 0) {
			if(lifc->tentative != tentative)
				lifc->tentative = tentative;
			if(lifcp != nil) {
				lifc->onlink = lifcp->onlink;
				lifc->autoflag = lifcp->autoflag;
				lifc->validlt = lifcp->validlt;
				lifc->preflt = lifcp->preflt;
				lifc->origint = lifcp->origint;
			}
			goto out;
		}
	}

	/* add the address to the list of logical ifc's for this ifc */
	lifc = smalloc(sizeof(Iplifc));
	ipmove(lifc->local, ip);
	ipmove(lifc->mask, mask);
	ipmove(lifc->remote, rem);
	ipmove(lifc->net, net);
	lifc->tentative = tentative;
	if(lifcp != nil) {
		lifc->onlink = lifcp->onlink;
		lifc->autoflag = lifcp->autoflag;
		lifc->validlt = lifcp->validlt;
		lifc->preflt = lifcp->preflt;
		lifc->origint = lifcp->origint;
	}
	else {		// default values
		lifc->onlink = 1;
		lifc->autoflag = 1;
		lifc->validlt = 0xffffffff;
		lifc->preflt = 0xffffffff;
		lifc->origint = NOW / 10^3;
	}
	lifc->next = nil;

	for(l = &ifc->lifc; *l; l = &(*l)->next)
		;
	*l = lifc;

	/* check for point-to-point interface */
	if(ipcmp(ip, v6loopback))	/* skip v6 loopback, it's a special address */
	if(ipcmp(mask, IPallbits) == 0)
		type |= Rptpt;

	/* add local routes */
	if(isv4(ip))
		v4addroute(f, tifc, rem+IPv4off, mask+IPv4off, rem+IPv4off, type);
	else
		v6addroute(f, tifc, rem, mask, rem, type);

	addselfcache(f, ifc, lifc, ip, Runi);

	if((type & (Rproxy|Rptpt)) == (Rproxy|Rptpt)){
		ipifcregisterproxy(f, ifc, rem);
		goto out;
	}

	if(isv4(ip) || ipcmp(ip, IPnoaddr) == 0) {
		/* add subnet directed broadcast address to the self cache */
		for(i = 0; i < IPaddrlen; i++)
			bcast[i] = (ip[i] & mask[i]) | ~mask[i];
		addselfcache(f, ifc, lifc, bcast, Rbcast);

		/* add subnet directed network address to the self cache */
		for(i = 0; i < IPaddrlen; i++)
			bcast[i] = (ip[i] & mask[i]) & mask[i];
		addselfcache(f, ifc, lifc, bcast, Rbcast);

		/* add network directed broadcast address to the self cache */
		memmove(mask, defmask(ip), IPaddrlen);
		for(i = 0; i < IPaddrlen; i++)
			bcast[i] = (ip[i] & mask[i]) | ~mask[i];
		addselfcache(f, ifc, lifc, bcast, Rbcast);

		/* add network directed network address to the self cache */
		memmove(mask, defmask(ip), IPaddrlen);
		for(i = 0; i < IPaddrlen; i++)
			bcast[i] = (ip[i] & mask[i]) & mask[i];
		addselfcache(f, ifc, lifc, bcast, Rbcast);

		addselfcache(f, ifc, lifc, IPv4bcast, Rbcast);
	}
	else {
		if(ipcmp(ip, v6loopback) == 0) {
			/* add node-local mcast address */
			addselfcache(f, ifc, lifc, v6allnodesN, Rmulti);

			/* add route for all node multicast */
			v6addroute(f, tifc, v6allnodesN, v6allnodesNmask, v6allnodesN, Rmulti);
		}

		/* add all nodes multicast address */
		addselfcache(f, ifc, lifc, v6allnodesL, Rmulti);

		/* add route for all nodes multicast */
		v6addroute(f, tifc, v6allnodesL, v6allnodesLmask, v6allnodesL, Rmulti);

		/* add solicited-node multicast address */
		ipv62smcast(bcast, ip);
		addselfcache(f, ifc, lifc, bcast, Rmulti);

		sendnbrdisc = 1;
	}

	/* register the address on this network for address resolution */
	if(isv4(ip) && ifc->m->areg != nil)
		(*ifc->m->areg)(ifc, ip);

out:
	wunlock(ifc);
	if(tentative && sendnbrdisc)
		icmpns(f, 0, SRC_UNSPEC, ip, TARG_MULTI, ifc->mac);
	return nil;
}

/*
 *  remove a logical interface from an ifc
 *  always called with ifc wlock'd
 */
static char*
ipifcremlifc(Ipifc *ifc, Iplifc *lifc)
{
	Iplifc **l;
	Fs *f;

	f = ifc->conv->p->f;

	/*
	 *  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(l = &ifc->lifc; *l != nil && *l != lifc; l = &(*l)->next)
		;
	if(*l == nil)
		return "address not on this interface";
	*l = lifc->next;

	/* disassociate any addresses */
	while(lifc->link)
		remselfcache(f, ifc, lifc, lifc->link->self->a);

	/* remove the route for this logical interface */
	if(isv4(lifc->local))
		v4delroute(f, lifc->remote+IPv4off, lifc->mask+IPv4off, 1);
	else {
		v6delroute(f, lifc->remote, lifc->mask, 1);
		if(ipcmp(lifc->local, v6loopback) == 0)
			/* remove route for all node multicast */