icmp6.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"

typedef struct ICMPpkt ICMPpkt;
typedef struct IPICMP IPICMP;
typedef struct Ndpkt Ndpkt;
typedef struct NdiscC NdiscC;

struct ICMPpkt {
	uchar	type;
	uchar	code;
	uchar	cksum[2];
	uchar	icmpid[2];
	uchar	seq[2];
};

struct IPICMP {
	Ip6hdr;
	ICMPpkt;
};

struct NdiscC
{
	IPICMP;
	uchar target[IPaddrlen];
};

struct Ndpkt
{
	NdiscC;
	uchar otype;
	uchar olen;	// length in units of 8 octets(incl type, code),
				// 1 for IEEE 802 addresses
	uchar lnaddr[6];	// link-layer address
};

enum {	
	// ICMPv6 types
	EchoReply	= 0,
	UnreachableV6	= 1,
	PacketTooBigV6	= 2,
	TimeExceedV6	= 3,
	SrcQuench	= 4,
	ParamProblemV6	= 4,
	Redirect	= 5,
	EchoRequest	= 8,
	TimeExceed	= 11,
	InParmProblem	= 12,
	Timestamp	= 13,
	TimestampReply	= 14,
	InfoRequest	= 15,
	InfoReply	= 16,
	AddrMaskRequest = 17,
	AddrMaskReply   = 18,
	EchoRequestV6	= 128,
	EchoReplyV6	= 129,
	RouterSolicit	= 133,
	RouterAdvert	= 134,
	NbrSolicit	= 135,
	NbrAdvert	= 136,
	RedirectV6	= 137,

	Maxtype6	= 137,
};

char *icmpnames6[Maxtype6+1] =
{
[EchoReply]		"EchoReply",
[UnreachableV6]		"UnreachableV6",
[PacketTooBigV6]	"PacketTooBigV6",
[TimeExceedV6]		"TimeExceedV6",
[SrcQuench]		"SrcQuench",
[Redirect]		"Redirect",
[EchoRequest]		"EchoRequest",
[TimeExceed]		"TimeExceed",
[InParmProblem]		"InParmProblem",
[Timestamp]		"Timestamp",
[TimestampReply]	"TimestampReply",
[InfoRequest]		"InfoRequest",
[InfoReply]		"InfoReply",
[AddrMaskRequest]	"AddrMaskRequest",
[AddrMaskReply]		"AddrMaskReply",
[EchoRequestV6]		"EchoRequestV6",
[EchoReplyV6]		"EchoReplyV6",
[RouterSolicit]		"RouterSolicit",
[RouterAdvert]		"RouterAdvert",
[NbrSolicit]		"NbrSolicit",
[NbrAdvert]		"NbrAdvert",
[RedirectV6]		"RedirectV6",
};

enum
{
	InMsgs6,
	InErrors6,
	OutMsgs6,
	CsumErrs6,
	LenErrs6,
	HlenErrs6,
	HoplimErrs6,
	IcmpCodeErrs6,
	TargetErrs6,
	OptlenErrs6,
	AddrmxpErrs6,
	RouterAddrErrs6,

	Nstats6,
};

static char *statnames6[Nstats6] =
{
[InMsgs6]	"InMsgs",
[InErrors6]	"InErrors",
[OutMsgs6]	"OutMsgs",
[CsumErrs6]	"CsumErrs",
[LenErrs6]	"LenErrs",
[HlenErrs6]	"HlenErrs",
[HoplimErrs6]	"HoplimErrs",
[IcmpCodeErrs6]	"IcmpCodeErrs",
[TargetErrs6]	"TargetErrs",
[OptlenErrs6]	"OptlenErrs",
[AddrmxpErrs6]	"AddrmxpErrs",
[RouterAddrErrs6]	"RouterAddrErrs",
};

typedef struct Icmppriv6
{
	ulong	stats[Nstats6];

	/* message counts */
	ulong	in[Maxtype6+1];
	ulong	out[Maxtype6+1];
} Icmppriv6;

typedef struct Icmpcb6 
{
	QLock;
	uchar headers;
} Icmpcb6;

static char *unreachcode[] =
{
[icmp6_no_route]	"no route to destination",
[icmp6_ad_prohib]	"comm with destination administratively prohibited",
[icmp6_unassigned]	"icmp unreachable: unassigned error code (2)",
[icmp6_adr_unreach]	"address unreachable",
[icmp6_port_unreach]	"port unreachable",
[icmp6_unkn_code]	"icmp unreachable: unknown code",
};

enum {
	ICMP_USEAD6	= 40,
};

enum {
	Oflag	= 1<<5,
	Sflag	= 1<<6,
	Rflag	= 1<<7,
};

enum {
	slladd	= 1,
	tlladd	= 2,
	prfinfo	= 3,
	redhdr	= 4,
	mtuopt	= 5,
};

static void icmpkick6(void *x, Block *bp);

static void
icmpcreate6(Conv *c)
{
	c->rq = qopen(64*1024, Qmsg, 0, c);
	c->wq = qbypass(icmpkick6, c);
}

static void
set_cksum(Block *bp)
{
	IPICMP *p = (IPICMP *)(bp->rp);

	hnputl(p->vcf, 0);  // borrow IP header as pseudoheader
	hnputs(p->ploadlen, blocklen(bp)-IPV6HDR_LEN);
	p->proto = 0;
	p->ttl = ICMPv6;	// ttl gets set later
	hnputs(p->cksum, 0);
	hnputs(p->cksum, ptclcsum(bp, 0, blocklen(bp)));
	p->proto = ICMPv6;
}

static Block *
newIPICMP(int packetlen)
{
	Block	*nbp;
	nbp = allocb(packetlen);
	nbp->wp += packetlen;
	memset(nbp->rp, 0, packetlen);
	return nbp;
}

void
icmpadvise6(Proto *icmp, Block *bp, char *msg)
{
	Conv	**c, *s;
	IPICMP	*p;
	ushort	recid;

	p = (IPICMP *) bp->rp;
	recid = nhgets(p->icmpid);

	for(c = icmp->conv; *c; c++) {
		s = *c;
		if(s->lport == recid)
		if(ipcmp(s->raddr, p->dst) == 0){
			qhangup(s->rq, msg);
			qhangup(s->wq, msg);
			break;
		}
	}
	freeblist(bp);
}

static void
icmpkick6(void *x, Block *bp)
{
	Conv *c = x;
	IPICMP *p;
	uchar laddr[IPaddrlen], raddr[IPaddrlen];
	Icmppriv6 *ipriv = c->p->priv;
	Icmpcb6 *icb = (Icmpcb6*)c->ptcl;

	if(bp == nil)
		return;

	if(icb->headers==6) {
		/* get user specified addresses */
		bp = pullupblock(bp, ICMP_USEAD6);
		if(bp == nil)
			return;
		bp->rp += 8;
		ipmove(laddr, bp->rp);
		bp->rp += IPaddrlen;
		ipmove(raddr, bp->rp);
		bp->rp += IPaddrlen;
		bp = padblock(bp, sizeof(Ip6hdr));
	}

	if(blocklen(bp) < sizeof(IPICMP)){
		freeblist(bp);
		return;
	}
	p = (IPICMP *)(bp->rp);
	if(icb->headers == 6) {
		ipmove(p->dst, raddr);
		ipmove(p->src, laddr);
	} else {
		ipmove(p->dst, c->raddr);
		ipmove(p->src, c->laddr);
		hnputs(p->icmpid, c->lport);
	}

	set_cksum(bp);
	p->vcf[0] = 0x06 << 4;
	if(p->type <= Maxtype6)	
		ipriv->out[p->type]++;
	ipoput6(c->p->f, bp, 0, c->ttl, c->tos, nil);
}

char*
icmpctl6(Conv *c, char **argv, int argc)
{
	Icmpcb6 *icb;

	icb = (Icmpcb6*) c->ptcl;

	if(argc==1) {
		if(strcmp(argv[0], "headers")==0) {
			icb->headers = 6;
			return nil;
		}
	}
	return "unknown control request";
}

static void
goticmpkt6(Proto *icmp, Block *bp, int muxkey)
{
	Conv	**c, *s;
	IPICMP	*p = (IPICMP *)bp->rp;
	ushort	recid; 
	uchar 	*addr;

	if(muxkey == 0) {
		recid = nhgets(p->icmpid);
		addr = p->src;
	}
	else {
		recid = muxkey;
		addr = p->dst;
	}

	for(c = icmp->conv; *c; c++){
		s = *c;
		if(s->lport == recid && ipcmp(s->raddr, addr) == 0){
			bp = concatblock(bp);
			if(bp != nil)
				qpass(s->rq, bp);
			return;
		}
	}

	freeblist(bp);
}

static Block *
mkechoreply6(Block *bp)
{
	IPICMP *p = (IPICMP *)(bp->rp);
	uchar	addr[IPaddrlen];

	ipmove(addr, p->src);
	ipmove(p->src, p->dst);
	ipmove(p->dst, addr);
	p->type = EchoReplyV6;
	set_cksum(bp);
	return bp;
}

/*
 * sends out an ICMPv6 neighbor solicitation
 * 	suni == SRC_UNSPEC or SRC_UNI, 
 *	tuni == TARG_MULTI => multicast for address resolution,
 * 	and tuni == TARG_UNI => neighbor reachability.
 */

extern void
icmpns(Fs *f, uchar* src, int suni, uchar* targ, int tuni, uchar* mac)
{
	Block	*nbp;
	Ndpkt *np;
	Proto *icmp = f->t2p[ICMPv6];
	Icmppriv6 *ipriv = icmp->priv;


	nbp = newIPICMP(sizeof(Ndpkt));
	np = (Ndpkt*) nbp->rp;


	if(suni == SRC_UNSPEC) 
		memmove(np->src, v6Unspecified, IPaddrlen);
	else 
		memmove(np->src, src, IPaddrlen);

	if(tuni == TARG_UNI)
		memmove(np->dst, targ, IPaddrlen);
	else
		ipv62smcast(np->dst, targ);

	np->type = NbrSolicit;
	np->code = 0;
	memmove(np->target, targ, IPaddrlen);
	if(suni != SRC_UNSPEC) {
		np->otype = SRC_LLADDRESS;
		np->olen = 1;	/* 1+1+6 = 8 = 1 8-octet */
		memmove(np->lnaddr, mac, sizeof(np->lnaddr));
	}
	else {
		int r = sizeof(Ndpkt)-sizeof(NdiscC);
		nbp->wp -= r;
	}

	set_cksum(nbp);
	np = (Ndpkt*) nbp->rp;
	np->ttl = HOP_LIMIT;
	np->vcf[0] = 0x06 << 4;
	ipriv->out[NbrSolicit]++;
	netlog(f, Logicmp, "sending neighbor solicitation %I\n", targ);
	ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
}

/*
 * sends out an ICMPv6 neighbor advertisement. pktflags == RSO flags.
 */
extern void
icmpna(Fs *f, uchar* src, uchar* dst, uchar* targ, uchar* mac, uchar flags)
{
	Block	*nbp;
	Ndpkt *np;
	Proto *icmp = f->t2p[ICMPv6];
	Icmppriv6 *ipriv = icmp->priv;

	nbp = newIPICMP(sizeof(Ndpkt));
	np = (Ndpkt*) nbp->rp;

	memmove(np->src, src, IPaddrlen);
	memmove(np->dst, dst, IPaddrlen);

	np->type = NbrAdvert;
	np->code = 0;
	np->icmpid[0] = flags;
	memmove(np->target, targ, IPaddrlen);

	np->otype = TARGET_LLADDRESS;
	np->olen = 1;	
	memmove(np->lnaddr, mac, sizeof(np->lnaddr));

	set_cksum(nbp);
	np = (Ndpkt*) nbp->rp;
	np->ttl = HOP_LIMIT;
	np->vcf[0] = 0x06 << 4;
	ipriv->out[NbrAdvert]++;
	netlog(f, Logicmp, "sending neighbor advertisement %I\n", src);
	ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
}

extern void
icmphostunr(Fs *f, Ipifc *ifc, Block *bp, int code, int free)
{
	Block *nbp;
	IPICMP *np;
	Ip6hdr	*p;
	int osz = BLEN(bp);
	int sz = MIN(sizeof(IPICMP) + osz, v6MINTU);
	Proto	*icmp = f->t2p[ICMPv6];
	Icmppriv6 *ipriv = icmp->priv;

	p = (Ip6hdr *) bp->rp;

	if(isv6mcast(p->src)) 
		goto clean;

	nbp = newIPICMP(sz);
	np = (IPICMP *) nbp->rp;

	rlock(ifc);
	if(ipv6anylocal(ifc, np->src)) {
		netlog(f, Logicmp, "send icmphostunr -> s%I d%I\n", p->src, p->dst);
	}
	else {
		netlog(f, Logicmp, "icmphostunr fail -> s%I d%I\n", p->src, p->dst);
		freeblist(nbp);
		if(free) 
			goto clean;
		else
			return;
	}

	memmove(np->dst, p->src, IPaddrlen);
	np->type = UnreachableV6;
	np->code = code;
	memmove(nbp->rp + sizeof(IPICMP), bp->rp, sz - sizeof(IPICMP));
	set_cksum(nbp);