--- /sys/src/9k/ip/arp.c
+++ /sys/src/9k/ip/arp.c
@@ -523,10 +523,10 @@ enum
 char *aformat = "%-6.6s %-8.8s %-40.40I %-32.32s\n";
 
 static void
-convmac(char *p, uchar *mac, int n)
+convmac(char *p, char *ep, uchar *mac, int n)
 {
 	while(n-- > 0)
-		p += sprint(p, "%2.2ux", *mac++);
+		p = seprint(p, ep, "%2.2ux", *mac++);
 }
 
 int
@@ -552,8 +552,9 @@ arpread(Arp *arp, char *p, ulong offset, int len)
 		}
 		len--;
 		qlock(arp);
-		convmac(mac, a->mac, a->type->maclen);
-		n += sprint(p+n, aformat, a->type->name, arpstate[a->state], a->ip, mac);
+		convmac(mac, &mac[sizeof mac], a->mac, a->type->maclen);
+		n += snprint(p+n, Alinelen+1, aformat, a->type->name,
+			arpstate[a->state], a->ip, mac);	/* +1 for NUL */
 		qunlock(arp);
 	}
 
--- /sys/src/9k/ip/chandial.c
+++ /sys/src/9k/ip/chandial.c
@@ -66,7 +66,7 @@ call(char *clone, char *dest, DS *ds)
 	name[n] = 0;
 	for(p = name; *p == ' '; p++)
 		;
-	sprint(name, "%lud", strtoul(p, 0, 0));
+	snprint(name, sizeof name, "%lud", strtoul(p, 0, 0));
 	p = strrchr(clone, '/');
 	*p = 0;
 	if(ds->dir)
--- /sys/src/9k/ip/ethermedium.c
+++ /sys/src/9k/ip/ethermedium.c
@@ -9,6 +9,8 @@
 #include "ip.h"
 #include "ipv6.h"
 
+#include "etherif.h"
+
 typedef struct Etherhdr Etherhdr;
 struct Etherhdr
 {
@@ -94,9 +96,6 @@ struct Etherrock
  */
 enum
 {
-	ETARP		= 0x0806,
-	ETIP4		= 0x0800,
-	ETIP6		= 0x86DD,
 	ARPREQUEST	= 1,
 	ARPREPLY	= 2,
 };
@@ -415,7 +414,7 @@ etheraddmulti(Ipifc *ifc, uchar *a, uchar *)
 	int version;
 
 	version = multicastea(mac, a);
-	sprint(buf, "addmulti %E", mac);
+	snprint(buf, sizeof buf, "addmulti %E", mac);
 	switch(version){
 	case V4:
 		er->cchan4->dev->write(er->cchan4, buf, strlen(buf), 0);
@@ -437,7 +436,7 @@ etherremmulti(Ipifc *ifc, uchar *a, uchar *)
 	int version;
 
 	version = multicastea(mac, a);
-	sprint(buf, "remmulti %E", mac);
+	snprint(buf, sizeof buf, "remmulti %E", mac);
 	switch(version){
 	case V4:
 		er->cchan4->dev->write(er->cchan4, buf, strlen(buf), 0);
--- /sys/src/9k/ip/icmp.c
+++ /sys/src/9k/ip/icmp.c
@@ -368,7 +368,7 @@ icmpiput(Proto *icmp, Ipifc*, Block *bp)
 	case EchoRequest:
 		if (iplen < n)
 			bp = trimblock(bp, 0, iplen);
-		r = mkechoreply(bp);
+		r = mkechoreply(concatblock(bp));
 		ipriv->out[EchoReply]++;
 		ipoput4(icmp->f, r, 0, MAXTTL, DFLTTOS, nil);
 		break;
@@ -395,7 +395,7 @@ icmpiput(Proto *icmp, Ipifc*, Block *bp)
 		break;
 	case TimeExceed:
 		if(p->code == 0){
-			sprint(m2, "ttl exceeded at %V", p->src);
+			snprint(m2, sizeof m2, "ttl exceeded at %V", p->src);
 
 			bp->rp += ICMP_IPSIZE+ICMP_HDRSIZE;
 			if(blocklen(bp) < MinAdvise){
--- /sys/src/9k/ip/icmp6.c
+++ /sys/src/9k/ip/icmp6.c
@@ -418,39 +418,37 @@ icmpna(Fs *f, uchar* src, uchar* dst, uchar* targ, uchar* mac, uchar flags)
 	ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
 }
 
+/* if free is true, freeblist(bp) before return. */
 extern void
 icmphostunr(Fs *f, Ipifc *ifc, Block *bp, int code, int free)
 {
-	int osz = BLEN(bp);
-	int sz = MIN(IPICMPSZ + osz, v6MINTU);
+	int osz, sz;
 	Block *nbp;
 	IPICMP *np;
+	Icmppriv6 *ipriv;
 	Ip6hdr *p;
-	Proto *icmp = f->t2p[ICMPv6];
-	Icmppriv6 *ipriv = icmp->priv;
+	Proto *icmp;
 
+	osz = BLEN(bp);
+	sz = MIN(IPICMPSZ + osz, v6MINTU);
+	icmp = f->t2p[ICMPv6];
+	ipriv = icmp->priv;
 	p = (Ip6hdr *)bp->rp;
-
 	if(isv6mcast(p->src))
-		goto clean;
-
+		goto freebl;
 	nbp = newIPICMP(sz);
 	np = (IPICMP *)nbp->rp;
 
 	rlock(ifc);
-	if(ipv6anylocal(ifc, np->src))
-		netlog(f, Logicmp, "send icmphostunr -> src %I dst %I\n",
-			p->src, p->dst);
-	else {
+	if(!ipv6anylocal(ifc, np->src)){
 		netlog(f, Logicmp, "icmphostunr fail -> src %I dst %I\n",
 			p->src, p->dst);
+		runlock(ifc);
 		freeblist(nbp);
-		if(free)
-			goto clean;
-		else
-			return;
+		goto freebl;
 	}
 
+	netlog(f, Logicmp, "send icmphostunr -> src %I dst %I\n", p->src, p->dst);
 	memmove(np->dst, p->src, IPaddrlen);
 	np->type = UnreachableV6;
 	np->code = code;
@@ -462,14 +460,12 @@ icmphostunr(Fs *f, Ipifc *ifc, Block *bp, int code, int free)
 
 	if(free)
 		ipiput6(f, ifc, nbp);
-	else {
+	else
 		ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
-		return;
-	}
-
-clean:
 	runlock(ifc);
-	freeblist(bp);
+freebl:
+	if(free)
+		freeblist(bp);
 }
 
 extern void
@@ -484,13 +480,11 @@ icmpttlexceeded6(Fs *f, Ipifc *ifc, Block *bp)
 	Icmppriv6 *ipriv = icmp->priv;
 
 	p = (Ip6hdr *)bp->rp;
-
 	if(isv6mcast(p->src))
 		return;
 
 	nbp = newIPICMP(sz);
 	np = (IPICMP *) nbp->rp;
-
 	if(ipv6anylocal(ifc, np->src))
 		netlog(f, Logicmp, "send icmpttlexceeded6 -> src %I dst %I\n",
 			p->src, p->dst);
@@ -523,13 +517,11 @@ icmppkttoobig6(Fs *f, Ipifc *ifc, Block *bp)
 	Icmppriv6 *ipriv = icmp->priv;
 
 	p = (Ip6hdr *)bp->rp;
-
 	if(isv6mcast(p->src))
 		return;
 
 	nbp = newIPICMP(sz);
 	np = (IPICMP *)nbp->rp;
-
 	if(ipv6anylocal(ifc, np->src))
 		netlog(f, Logicmp, "send icmppkttoobig6 -> src %I dst %I\n",
 			p->src, p->dst);
@@ -555,15 +547,13 @@ icmppkttoobig6(Fs *f, Ipifc *ifc, Block *bp)
  * RFC 2461, pages 39-40, pages 57-58.
  */
 static int
-valid(Proto *icmp, Ipifc *ifc, Block *bp, Icmppriv6 *ipriv)
+valid(Proto *icmp, Ipifc *, Block *bp, Icmppriv6 *ipriv)
 {
-	int sz, osz, unsp, n, ttl, iplen;
-	int pktsz = BLEN(bp);
-	uchar *packet = bp->rp;
-	IPICMP *p = (IPICMP *) packet;
+	int sz, osz, unsp, n, ttl, iplen, pktsz;
+	uchar *packet;
+	IPICMP *p;
 	Ndpkt *np;
 
-	USED(ifc);
 	n = blocklen(bp);
 	if(n < IPICMPSZ) {
 		ipriv->stats[HlenErrs6]++;
@@ -571,6 +561,9 @@ valid(Proto *icmp, Ipifc *ifc, Block *bp, Icmppriv6 *ipriv)
 		goto err;
 	}
 
+	packet = bp->rp;
+	p = (IPICMP *)packet;
+	pktsz = BLEN(bp);
 	iplen = nhgets(p->ploadlen);
 	if(iplen > n - IP6HDR) {
 		ipriv->stats[LenErrs6]++;
@@ -597,91 +590,78 @@ valid(Proto *icmp, Ipifc *ifc, Block *bp, Icmppriv6 *ipriv)
 	p->ttl = ttl;
 
 	/* additional tests for some pkt types */
-	if (p->type == NbrSolicit   || p->type == NbrAdvert ||
-	    p->type == RouterAdvert || p->type == RouterSolicit ||
-	    p->type == RedirectV6) {
-		if(p->ttl != HOP_LIMIT) {
-			ipriv->stats[HoplimErrs6]++;
+	if (p->type != NbrSolicit   && p->type != NbrAdvert &&
+	    p->type != RouterAdvert && p->type != RouterSolicit &&
+	    p->type != RedirectV6)
+		return 1;	/* TODO: unknown, presumed valid; why? */
+	if(p->ttl != HOP_LIMIT) {
+		ipriv->stats[HoplimErrs6]++;
+		goto err;
+	}
+	if(p->code != 0) {
+		ipriv->stats[IcmpCodeErrs6]++;
+		goto err;
+	}
+
+	switch (p->type) {
+	case NbrSolicit:
+	case NbrAdvert:
+		np = (Ndpkt*) p;
+		if(isv6mcast(np->target)) {
+			ipriv->stats[TargetErrs6]++;
 			goto err;
 		}
-		if(p->code != 0) {
-			ipriv->stats[IcmpCodeErrs6]++;
+		if(optexsts(np) && np->olen == 0) {
+			ipriv->stats[OptlenErrs6]++;
 			goto err;
 		}
-
-		switch (p->type) {
-		case NbrSolicit:
-		case NbrAdvert:
-			np = (Ndpkt*) p;
-			if(isv6mcast(np->target)) {
-				ipriv->stats[TargetErrs6]++;
+		if (p->type == NbrSolicit && ipcmp(np->src, v6Unspecified) == 0)
+			if(!issmcast(np->dst) || optexsts(np)) {
+				ipriv->stats[AddrmxpErrs6]++;
 				goto err;
 			}
-			if(optexsts(np) && np->olen == 0) {
+		if(p->type == NbrAdvert && isv6mcast(np->dst) &&
+		    nhgets(np->icmpid) & Sflag){
+			ipriv->stats[AddrmxpErrs6]++;
+			goto err;
+		}
+		break;
+	case RouterAdvert:
+		if(pktsz - IP6HDR < 16) {
+			ipriv->stats[HlenErrs6]++;
+			goto err;
+		}
+		if(!islinklocal(p->src)) {
+			ipriv->stats[RouterAddrErrs6]++;
+			goto err;
+		}
+		for (sz = IPICMPSZ + 8; sz+1 < pktsz; sz += 8*osz) {
+			osz = packet[sz+1];
+			if(osz <= 0) {
 				ipriv->stats[OptlenErrs6]++;
 				goto err;
 			}
-
-			if (p->type == NbrSolicit &&
-			    ipcmp(np->src, v6Unspecified) == 0)
-				if(!issmcast(np->dst) || optexsts(np)) {
-					ipriv->stats[AddrmxpErrs6]++;
-					goto err;
-				}
-
-			if(p->type == NbrAdvert)
-				if(isv6mcast(np->dst) &&
-				    (nhgets(np->icmpid) & Sflag)){
-					ipriv->stats[AddrmxpErrs6]++;
-					goto err;
-				}
-			break;
-
-		case RouterAdvert:
-			if(pktsz - IP6HDR < 16) {
-				ipriv->stats[HlenErrs6]++;
-				goto err;
-			}
-			if(!islinklocal(p->src)) {
-				ipriv->stats[RouterAddrErrs6]++;
-				goto err;
-			}
-			sz = IPICMPSZ + 8;
-			while (sz+1 < pktsz) {
-				osz = packet[sz+1];
-				if(osz <= 0) {
-					ipriv->stats[OptlenErrs6]++;
-					goto err;
-				}
-				sz += 8*osz;
-			}
-			break;
-
-		case RouterSolicit:
-			if(pktsz - IP6HDR < 8) {
-				ipriv->stats[HlenErrs6]++;
+		}
+		break;
+	case RouterSolicit:
+		if(pktsz - IP6HDR < 8) {
+			ipriv->stats[HlenErrs6]++;
+			goto err;
+		}
+		unsp = (ipcmp(p->src, v6Unspecified) == 0);
+		for (sz = IPICMPSZ + 8; sz+1 < pktsz; sz += 8*osz) {
+			osz = packet[sz+1];
+			if(osz <= 0 || (unsp && packet[sz] == SRC_LLADDR)) {
+				ipriv->stats[OptlenErrs6]++;
 				goto err;
 			}
-			unsp = (ipcmp(p->src, v6Unspecified) == 0);
-			sz = IPICMPSZ + 8;
-			while (sz+1 < pktsz) {
-				osz = packet[sz+1];
-				if(osz <= 0 ||
-				    (unsp && packet[sz] == SRC_LLADDR)) {
-					ipriv->stats[OptlenErrs6]++;
-					goto err;
-				}
-				sz += 8*osz;
-			}
-			break;
-
-		case RedirectV6:
-			/* to be filled in */
-			break;
-
-		default:
-			goto err;
 		}
+		break;
+	case RedirectV6:
+		/* TODO: fill in */
+		break;
+	default:
+		goto err;
 	}
 	return 1;
 err:
@@ -712,35 +692,39 @@ targettype(Fs *f, Ipifc *ifc, uchar *target)
 	return 0;
 }
 
+/* bp needs to be freed with freeblist or passed on. */
 static void
 icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
 {
-	int refresh = 1;
+	int type;
 	char *msg, m2[128];
 	uchar pktflags;
-	uchar *packet = bp->rp;
+	uchar *packet, *src;
 	uchar lsrc[IPaddrlen];
 	Block *r;
-	IPICMP *p = (IPICMP *)packet;
-	Icmppriv6 *ipriv = icmp->priv;
+	IPICMP *p;
+	Icmppriv6 *ipriv;
 	Iplifc *lifc;
 	Ndpkt* np;
 	Proto *pr;
 
-	if(!valid(icmp, ipifc, bp, ipriv) || p->type > Maxtype6)
+	packet = bp->rp;
+	p = (IPICMP *)packet;
+	type = p->type;
+	ipriv = icmp->priv;
+	if(!valid(icmp, ipifc, bp, ipriv) || type > Maxtype6)
 		goto raise;
 
-	ipriv->in[p->type]++;
-
-	switch(p->type) {
+	ipriv->in[type]++;
+	switch(type) {
 	case EchoRequestV6:
+		bp = concatblock(bp);
 		r = mkechoreply6(bp, ipifc);
 		if(r == nil)
 			goto raise;
 		ipriv->out[EchoReply]++;
 		ipoput6(icmp->f, r, 0, MAXTTL, DFLTTOS, nil);
 		break;
-
 	case UnreachableV6:
 		if(p->code >= nelem(unreachcode))
 			msg = unreachcode[Icmp6_unknown];
@@ -762,11 +746,9 @@ icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
 		bp->rp -= IPICMPSZ;
 		goticmpkt6(icmp, bp, 0);
 		break;
-
 	case TimeExceedV6:
 		if(p->code == 0){
-			sprint(m2, "ttl exceeded at %I", p->src);
-
+			snprint(m2, sizeof m2, "ttl exceeded at %I", p->src);
 			bp->rp += IPICMPSZ;
 			if(blocklen(bp) < 8){
 				ipriv->stats[LenErrs6]++;
@@ -780,10 +762,8 @@ icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
 			}
 			bp->rp -= IPICMPSZ;
 		}
-
 		goticmpkt6(icmp, bp, 0);
 		break;
-
 	case RouterAdvert:
 	case RouterSolicit:
 		/* using lsrc as a temp, munge hdr for goticmp6 */
@@ -792,43 +772,39 @@ icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
 			memmove(p->src, p->dst, IPaddrlen);
 			memmove(p->dst, lsrc, IPaddrlen);
 		}
-		goticmpkt6(icmp, bp, p->type);
+		goticmpkt6(icmp, bp, type);
 		break;
-
 	case NbrSolicit:
-		np = (Ndpkt*) p;
+		np = (Ndpkt*)p;			/* within bp */
 		pktflags = 0;
 		switch (targettype(icmp->f, ipifc, np->target)) {
 		case Tunirany:
 			pktflags |= Oflag;
 			/* fall through */
-
 		case Tuniproxy:
 			if(ipcmp(np->src, v6Unspecified) != 0) {
 				arpenter(icmp->f, V6, np->src, np->lnaddr,
 					8*np->olen-2, 0);
 				pktflags |= Sflag;
 			}
-			if(ipv6local(ipifc, lsrc))
-				icmpna(icmp->f, lsrc,
-					(ipcmp(np->src, v6Unspecified) == 0?
-						v6allnodesL: np->src),
-					np->target, ipifc->mac, pktflags);
-			else
-				freeblist(bp);
+			if(ipv6local(ipifc, lsrc)) {
+				src = np->src;
+				if(ipcmp(src, v6Unspecified) == 0)
+					src = v6allnodesL;
+				icmpna(icmp->f, lsrc, src, np->target,
+					ipifc->mac, pktflags);
+			}
 			break;
-
 		case Tunitent:
-			/* not clear what needs to be done. send up
-			 * an icmp mesg saying don't use this address? */
-		default:
-			freeblist(bp);
+			/*
+			 * not clear what needs to be done.  send up
+			 * an icmp mesg saying `don't use this address'?
+			 */
+			break;
 		}
+		freeblist(bp);
 		break;
-
 	case NbrAdvert:
-		np = (Ndpkt*) p;
-
 		/*
 		 * if the target address matches one of the local interface
 		 * addresses and the local interface address has tentative bit
@@ -836,20 +812,19 @@ icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
 		 * detection part of ipconfig can discover duplication through
 		 * the arp table.
 		 */
+		np = (Ndpkt*)p;			/* within bp */
 		lifc = iplocalonifc(ipifc, np->target);
-		if(lifc && lifc->tentative)
-			refresh = 0;
 		arpenter(icmp->f, V6, np->target, np->lnaddr, 8*np->olen-2,
-			refresh);
+			lifc && lifc->tentative);
 		freeblist(bp);
 		break;
-
 	case PacketTooBigV6:
 	default:
 		goticmpkt6(icmp, bp, 0);
 		break;
 	}
 	return;
+
 raise:
 	freeblist(bp);
 }
@@ -870,14 +845,12 @@ icmpstats6(Proto *icmp6, char *buf, int len)
 		if(icmpnames6[i])
 			p = seprint(p, e, "%s: %lud %lud\n", icmpnames6[i],
 				priv->in[i], priv->out[i]);
-/*		else
+		else if (0)
 			p = seprint(p, e, "%d: %lud %lud\n", i, priv->in[i],
 				priv->out[i]);
- */
 	return p - buf;
 }
 
-
 /* import from icmp.c */
 extern int	icmpstate(Conv *c, char *state, int n);
 extern char*	icmpannounce(Conv *c, char **argv, int argc);
--- /sys/src/9k/ip/ip.c
+++ /sys/src/9k/ip/ip.c
@@ -215,7 +215,8 @@ ipoput4(Fs *f, Block *bp, int gating, int ttl, int tos, Conv *c)
 		return 0;
 	}
 
-if((eh->frag[0] & (IP_DF>>8)) && !gating) print("%V: DF set\n", eh->dst);
+	if((eh->frag[0] & (IP_DF>>8)) && !gating)
+		print("%V: DF set\n", eh->dst);
 
 	if(eh->frag[0] & (IP_DF>>8)){
 		ip->stats[FragFails]++;
--- /sys/src/9k/ip/ip.h
+++ /sys/src/9k/ip/ip.h
@@ -38,7 +38,7 @@ enum
 	Addrlen=	64,
 	Maxproto=	20,
 	Nhash=		64,
-	Maxincall=	128,
+	Maxincall=	128,	/* max. conn.s in listen q not accepted yet */
 	Nchans=		1024,
 	MAClen=		16,		/* longest mac address */
 
--- /sys/src/9k/ip/ipifc.c
+++ /sys/src/9k/ip/ipifc.c
@@ -16,6 +16,7 @@ enum {
 	NHASH		= 1<<6,
 	NCACHE		= 256,
 	QMAX		= 192*1024-1,
+	Maxv6repr	= (128/(4*4))*(4+1), /* limit of xxxx:xxxx:⋯ notation */
 };
 
 Medium *media[Maxmedia] = { 0 };
@@ -1611,7 +1612,7 @@ ipifcadd6(Ipifc *ifc, char**argv, int argc)
 {
 	int plen = 64;
 	long origint = NOW / 1000, preflt = ~0L, validlt = ~0L;
-	char addr[40], preflen[6];
+	char addr[Maxv6repr], preflen[6];
 	char *params[3];
 	uchar autoflag = 1, onlink = 1;
 	uchar prefix[IPaddrlen];
@@ -1639,9 +1640,17 @@ ipifcadd6(Ipifc *ifc, char**argv, int argc)
 		return Ebadarg;
 	}
 
-	if (parseip(prefix, argv[1]) != 6 || validlt < preflt || plen < 0 ||
-	    plen > 64 || islinklocal(prefix))
-		return Ebadarg;
+	if (parseip(prefix, argv[1]) != 6)
+		return "bad ipv6 address";
+	if (validlt < preflt)
+		return "valid ipv6 lifetime less than preferred lifetime";
+	if (plen < 0)
+		return "negative ipv6 prefix length";
+	/* i think that this length limit is bogus - geoff */
+//	if (plen > 64)
+//		return "ipv6 prefix length greater than 64;
+	if (islinklocal(prefix))
+		return "ipv6 prefix is link-local";
 
 	lifc = smalloc(sizeof(Iplifc));
 	lifc->onlink = (onlink != 0);
@@ -1652,10 +1661,10 @@ ipifcadd6(Ipifc *ifc, char**argv, int argc)
 
 	/* issue "add" ctl msg for v6 link-local addr and prefix len */
 	if(!ifc->medium->pref2addr)
-		return Ebadarg;
+		return "no pref2addr on interface";
 	ifc->medium->pref2addr(prefix, ifc->mac);	/* mac → v6 link-local addr */
-	sprint(addr, "%I", prefix);
-	sprint(preflen, "/%d", plen);
+	snprint(addr, sizeof addr, "%I", prefix);
+	snprint(preflen, sizeof preflen, "/%d", plen);
 	params[0] = "add";
 	params[1] = addr;
 	params[2] = preflen;
--- /sys/src/9k/ip/ipv6.c
+++ /sys/src/9k/ip/ipv6.c
@@ -259,7 +259,7 @@ ipiput6(Fs *f, Ipifc *ifc, Block *bp)
 	tentative = iptentative(f, v6dst);
 
 	if(tentative && h->proto != ICMPv6) {
-		print("tentative addr, drop\n");
+		print("ipv6 non-icmp tentative addr %I, drop\n", v6dst);
 		freeblist(bp);
 		return;
 	}
--- /sys/src/9k/ip/ipv6.h
+++ /sys/src/9k/ip/ipv6.h
@@ -20,10 +20,6 @@
 #define optexsts(np)	(nhgets((np)->ploadlen) > 24)
 #define issmcast(addr)	(memcmp((addr), v6solicitednode, 13) == 0)
 
-#ifndef MIN
-#define MIN(a, b) ((a) <= (b)? (a): (b))
-#endif
-
 enum {				/* Header Types */
 	HBH		= 0,	/* hop-by-hop multicast routing protocol */
 	ICMP		= 1,
--- /sys/src/9k/k10/etherif.h
+++ /sys/src/9k/k10/etherif.h
@@ -5,6 +5,11 @@ enum
 	ETHERMAXTU	= 1514,		/* maximum transmit size */
 	ETHERHDRSIZE	= 14,		/* size of an ethernet header */
 
+	/* ethernet packet types */
+	ETARP		= 0x0806,
+	ETIP4		= 0x0800,
+	ETIP6		= 0x86DD,
+
 	MaxEther	= 48,
 	Ntypes		= 8,
 };