The introduction of IPv6 support from NetBSD's mountd invalidated

a number of assumptions related to the parsing of options in
/etc/exports, and missed a few necessary new error checks.

The main problems related to netmasks: an IPv6 network address
missing a netmask would result in the filesystem being exported to
the whole IPv6 world, non-continuous netmasks would be made continuous
without any warnings, and nothing prevented you specifying an IPv4
mask with an IPv6 address.

This change addresses these issues. As a side-effect we now store
netmasks in sockaddr structs (this matches the kernel interface,
and is closer to the way it used to be). Add a flag OP_HAVEMASK to
keep track of whether or not we have successfully got a mask from
any source. Replace some mask-related helper functions with versions
that use the sockaddr-based masks.

Also tidy up get_net() and fix the code that interprets IPv4 partial
networks such as "127.1" as network rather than host addresses.
Properly zero out some structures that were ending up partially
containing junk from the stack, fix a few formatting issues, and
add a comment noting some assumptions about export arguments.

1 files changed, 207 insertions, 243 deletions

diff --git a/usr.sbin/mountd/mountd.c b/usr.sbin/mountd/mountd.c
index f1c56ff..303896c 100644
--- a/usr.sbin/mountd/mountd.c
+++ b/usr.sbin/mountd/mountd.c
@@ -125,7 +125,7 @@ struct exportlist {
 
 struct netmsk {
 	struct sockaddr_storage nt_net;
-	u_int32_t	nt_mask;
+	struct sockaddr_storage nt_mask;
 	char		*nt_name;
 };
 
@@ -165,6 +165,7 @@ void	add_dlist __P((struct dirlist **, struct dirlist *,
 void	add_mlist __P((char *, char *));
 int	check_dirpath __P((char *));
 int	check_options __P((struct dirlist *));
+int	checkmask(struct sockaddr *sa);
 int	chk_host __P((struct dirlist *, struct sockaddr *, int *, int *));
 void	del_mlist(char *hostp, char *dirp);
 struct dirlist *dirp_search __P((struct dirlist *, char *));
@@ -189,11 +190,15 @@ struct grouplist *get_grp __P((void));
 void	hang_dirp __P((struct dirlist *, struct grouplist *,
 				struct exportlist *, int));
 void	huphandler(int sig);
+int	makemask(struct sockaddr_storage *ssp, int bitlen);
 void	mntsrv __P((struct svc_req *, SVCXPRT *));
 void	nextfield __P((char **, char **));
 void	out_of_mem __P((void));
 void	parsecred __P((char *, struct xucred *));
 int	put_exlist __P((struct dirlist *, XDR *, struct dirlist *, int *));
+void	*sa_rawaddr(struct sockaddr *sa, int *nbytes);
+int	sacmp(struct sockaddr *sa1, struct sockaddr *sa2,
+    struct sockaddr *samask);
 int	scan_tree __P((struct dirlist *, struct sockaddr *));
 static void usage __P((void));
 int	xdr_dir __P((XDR *, char *));
@@ -202,12 +207,6 @@ int	xdr_fhs __P((XDR *, caddr_t));
 int	xdr_mlist __P((XDR *, caddr_t));
 void	terminate __P((int));
 
-static int bitcmp __P((void *, void *, int));
-static int netpartcmp __P((struct sockaddr *, struct sockaddr *, int));
-static int sacmp __P((struct sockaddr *, struct sockaddr *));
-static int allones __P((struct sockaddr_storage *, int));
-static int countones __P((struct sockaddr *));
-
 struct exportlist *exphead;
 struct mountlist *mlhead;
 struct grouplist *grphead;
@@ -234,13 +233,14 @@ static const int ninumeric = NI_NUMERICHOST;
 #endif
 
 int mountdlockfd;
-/* Bits for above */
+/* Bits for opt_flags above */
 #define	OP_MAPROOT	0x01
 #define	OP_MAPALL	0x02
 #define	OP_KERB		0x04
 #define	OP_MASK		0x08
 #define	OP_NET		0x10
 #define	OP_ALLDIRS	0x40
+#define	OP_HAVEMASK	0x80	/* A mask was specified or inferred. */
 #define OP_MASKLEN	0x200
 
 #ifdef DEBUG
@@ -1116,6 +1116,7 @@ get_exportlist()
 		 * host(s) on the same line.
 		 */
 		} else if ((opt_flags & OP_NET) && tgrp->gr_next) {
+			syslog(LOG_ERR, "network/host conflict");
 			getexp_err(ep, tgrp);
 			goto nextline;
 
@@ -1397,47 +1398,6 @@ dirp_search(dp, dirp)
 }
 
 /*
- * Some helper functions for netmasks. They all assume masks in network
- * order (big endian).
- */
-static int
-bitcmp(void *dst, void *src, int bitlen)
-{
-	int i;
-	u_int8_t *p1 = dst, *p2 = src;
-	u_int8_t bitmask;
-	int bytelen, bitsleft;
-
-	bytelen = bitlen / 8;
-	bitsleft = bitlen % 8;
-
-	if (debug) {
-		printf("comparing:\n");
-		for (i = 0; i < (bitsleft ? bytelen + 1 : bytelen); i++)
-			printf("%02x", p1[i]);
-		printf("\n");
-		for (i = 0; i < (bitsleft ? bytelen + 1 : bytelen); i++)
-			printf("%02x", p2[i]);
-		printf("\n");
-	}
-
-	for (i = 0; i < bytelen; i++) {
-		if (*p1 != *p2)
-			return 1;
-		p1++;
-		p2++;
-	}
-
-	for (i = 0; i < bitsleft; i++) {
-		bitmask = 1 << (7 - i);
-		if ((*p1 & bitmask) != (*p2 & bitmask))
-			return 1;
-	}
-
-	return 0;
-}
-
-/*
  * Scan for a host match in a directory tree.
  */
 int
@@ -1461,22 +1421,23 @@ chk_host(dp, saddr, defsetp, hostsetp)
 			case GT_HOST:
 				ai = grp->gr_ptr.gt_addrinfo;
 				for (; ai; ai = ai->ai_next) {
-					if (!sacmp(ai->ai_addr, saddr)) {
+					if (!sacmp(ai->ai_addr, saddr, NULL)) {
 						*hostsetp =
 						    (hp->ht_flag | DP_HOSTSET);
 						return (1);
 					}
 				}
-			    break;
+				break;
 			case GT_NET:
-				if (!netpartcmp(saddr,
-				    (struct sockaddr *) &grp->gr_ptr.gt_net.nt_net,
-				     grp->gr_ptr.gt_net.nt_mask)) {
+				if (!sacmp(saddr, (struct sockaddr *)
+				    &grp->gr_ptr.gt_net.nt_net,
+				    (struct sockaddr *)
+				    &grp->gr_ptr.gt_net.nt_mask)) {
 					*hostsetp = (hp->ht_flag | DP_HOSTSET);
 					return (1);
 				}
-			    break;
-			};
+				break;
+			}
 			hp = hp->ht_next;
 		}
 	}
@@ -1582,7 +1543,7 @@ do_opt(cpp, endcpp, ep, grp, has_hostp, exflagsp, cr)
 			*exflagsp |= MNT_EXKERB;
 			opt_flags |= OP_KERB;
 		} else if (cpoptarg && (!strcmp(cpopt, "mask") ||
-			!strcmp(cpopt, "m"))) {
+		    !strcmp(cpopt, "m"))) {
 			if (get_net(cpoptarg, &grp->gr_ptr.gt_net, 1)) {
 				syslog(LOG_ERR, "bad mask: %s", cpoptarg);
 				return (1);
@@ -1683,7 +1644,7 @@ get_host(cp, grp, tgrp)
 				continue;
 			for (tai = checkgrp->gr_ptr.gt_addrinfo; tai != NULL;
 			    tai = tai->ai_next) {
-				if (sacmp(tai->ai_addr, ai->ai_addr) != 0)
+				if (sacmp(tai->ai_addr, ai->ai_addr, NULL) != 0)
 					continue;
 				if (debug)
 					fprintf(stderr,
@@ -1773,8 +1734,8 @@ do_mount(ep, grp, exflags, anoncrp, dirp, dirplen, fsb)
 	int dirplen;
 	struct statfs *fsb;
 {
-	struct sockaddr_storage ss;
 	struct addrinfo *ai;
+	struct export_args *eap;
 	char *cp = NULL;
 	int done;
 	char savedc = '\0';
@@ -1782,17 +1743,18 @@ do_mount(ep, grp, exflags, anoncrp, dirp, dirplen, fsb)
 		struct ufs_args ua;
 		struct iso_args ia;
 		struct mfs_args ma;
-#ifdef __NetBSD__
 		struct msdosfs_args da;
-		struct adosfs_args aa;
-#endif
 		struct ntfs_args na;
 	} args;
 
+	bzero(&args, sizeof args);
+	/* XXX, we assume that all xx_args look like ufs_args. */
 	args.ua.fspec = 0;
-	args.ua.export.ex_flags = exflags;
-	args.ua.export.ex_anon = *anoncrp;
-	args.ua.export.ex_indexfile = ep->ex_indexfile;
+	eap = &args.ua.export;
+
+	eap->ex_flags = exflags;
+	eap->ex_anon = *anoncrp;
+	eap->ex_indexfile = ep->ex_indexfile;
 	if (grp->gr_type == GT_HOST)
 		ai = grp->gr_ptr.gt_addrinfo;
 	else
@@ -1803,35 +1765,26 @@ do_mount(ep, grp, exflags, anoncrp, dirp, dirplen, fsb)
 		case GT_HOST:
 			if (ai->ai_addr->sa_family == AF_INET6 && have_v6 == 0)
 				goto skip;
-			args.ua.export.ex_addr = ai->ai_addr;
-			args.ua.export.ex_addrlen = ai->ai_addrlen;
-			args.ua.export.ex_masklen = 0;
+			eap->ex_addr = ai->ai_addr;
+			eap->ex_addrlen = ai->ai_addrlen;
+			eap->ex_masklen = 0;
 			break;
 		case GT_NET:
-			args.ua.export.ex_addr = (struct sockaddr *)
-			    &grp->gr_ptr.gt_net.nt_net;
-			if (args.ua.export.ex_addr->sa_family == AF_INET6 &&
+			if (grp->gr_ptr.gt_net.nt_net.ss_family == AF_INET6 &&
 			    have_v6 == 0)
 				goto skip;
-			args.ua.export.ex_addrlen =
-			    args.ua.export.ex_addr->sa_len;
-			memset(&ss, 0, sizeof ss);
-			ss.ss_family = args.ua.export.ex_addr->sa_family;
-			ss.ss_len = args.ua.export.ex_addr->sa_len;
-			if (allones(&ss, grp->gr_ptr.gt_net.nt_mask) != 0) {
-				syslog(LOG_ERR, "Bad network flag");
-				if (cp)
-					*cp = savedc;
-				return (1);
-			}
-			args.ua.export.ex_mask = (struct sockaddr *)&ss;
-			args.ua.export.ex_masklen = ss.ss_len;
+			eap->ex_addr =
+			    (struct sockaddr *)&grp->gr_ptr.gt_net.nt_net;
+			eap->ex_addrlen = args.ua.export.ex_addr->sa_len;
+			eap->ex_mask =
+			    (struct sockaddr *)&grp->gr_ptr.gt_net.nt_mask;
+			eap->ex_masklen = args.ua.export.ex_mask->sa_len;
 			break;
 		case GT_DEFAULT:
-			args.ua.export.ex_addr = NULL;
-			args.ua.export.ex_addrlen = 0;
-			args.ua.export.ex_mask = NULL;
-			args.ua.export.ex_masklen = 0;
+			eap->ex_addr = NULL;
+			eap->ex_addrlen = 0;
+			eap->ex_mask = NULL;
+			eap->ex_masklen = 0;
 			break;
 		case GT_IGNORE:
 			return(0);
@@ -1896,6 +1849,8 @@ skip:
 
 /*
  * Translate a net address.
+ *
+ * If `maskflg' is nonzero, then `cp' is a netmask, not a network address.
  */
 int
 get_net(cp, net, maskflg)
@@ -1905,12 +1860,11 @@ get_net(cp, net, maskflg)
 {
 	struct netent *np;
 	char *name, *p, *prefp;
-	struct sockaddr_in sin, *sinp;
+	struct sockaddr_in sin;
 	struct sockaddr *sa;
 	struct addrinfo hints, *ai = NULL;
 	char netname[NI_MAXHOST];
 	long preflen;
-	int ecode;
 
 	p = prefp = NULL;
 	if ((opt_flags & OP_MASKLEN) && !maskflg) {
@@ -1920,80 +1874,97 @@ get_net(cp, net, maskflg)
 	}
 
 	if ((np = getnetbyname(cp)) != NULL) {
+		bzero(&sin, sizeof sin);
 		sin.sin_family = AF_INET;
 		sin.sin_len = sizeof sin;
 		sin.sin_addr = inet_makeaddr(np->n_net, 0);
 		sa = (struct sockaddr *)&sin;
-	} else if (isdigit(*cp)) {
+	} else if (isxdigit(*cp) || *cp == ':') {
 		memset(&hints, 0, sizeof hints);
-		hints.ai_family = AF_UNSPEC;
+		/* Ensure the mask and the network have the same family. */
+		if (maskflg && (opt_flags & OP_NET))
+			hints.ai_family = net->nt_net.ss_family;
+		else if (!maskflg && (opt_flags & OP_HAVEMASK))
+			hints.ai_family = net->nt_mask.ss_family;
+		else
+			hints.ai_family = AF_UNSPEC;
 		hints.ai_flags = AI_NUMERICHOST;
-		if (getaddrinfo(cp, NULL, &hints, &ai) != 0) {
+		if (getaddrinfo(cp, NULL, &hints, &ai) != 0)
+			goto fail;
+		if (ai->ai_family == AF_INET) {
 			/*
-			 * If getaddrinfo() failed, try the inet4 network
-			 * notation with less than 3 dots.
+			 * The address in `cp' is really a network address, so
+			 * use inet_network() to re-interpret this correctly.
+			 * e.g. "127.1" means 127.1.0.0, not 127.0.0.1.
 			 */
+			bzero(&sin, sizeof sin);
 			sin.sin_family = AF_INET;
 			sin.sin_len = sizeof sin;
-			sin.sin_addr = inet_makeaddr(inet_network(cp),0);
+			sin.sin_addr = inet_makeaddr(inet_network(cp), 0);
 			if (debug)
-				fprintf(stderr, "get_net: v4 addr %x\n",
-				    sin.sin_addr.s_addr);
+				fprintf(stderr, "get_net: v4 addr %s\n",
+				    inet_ntoa(sin.sin_addr));
 			sa = (struct sockaddr *)&sin;
 		} else
 			sa = ai->ai_addr;
-	} else if (isxdigit(*cp) || *cp == ':') {
-		memset(&hints, 0, sizeof hints);
-		hints.ai_family = AF_UNSPEC;
-		hints.ai_flags = AI_NUMERICHOST;
-		if (getaddrinfo(cp, NULL, &hints, &ai) == 0)
-			sa = ai->ai_addr;
-		else
-			goto fail;
 	} else
 		goto fail;
 
-	ecode = getnameinfo(sa, sa->sa_len, netname, sizeof netname,
-	    NULL, 0, ninumeric);
-	if (ecode != 0)
-		goto fail;
+	if (maskflg) {
+		/* The specified sockaddr is a mask. */
+		if (checkmask(sa) != 0)
+			goto fail;
+		bcopy(sa, &net->nt_mask, sa->sa_len);
+		opt_flags |= OP_HAVEMASK;
+	} else {
+		/* The specified sockaddr is a network address. */
+		bcopy(sa, &net->nt_net, sa->sa_len);
 
-	if (maskflg)
-		net->nt_mask = countones(sa);
-	else {
+		/* Get a network name for the export list. */
+		if (np) {
+			name = np->n_name;
+		} else if (getnameinfo(sa, sa->sa_len, netname, sizeof netname,
+		   NULL, 0, ninumeric) == 0) {
+			name = netname;
+		} else {
+			goto fail;
+		}
+		if ((net->nt_name = strdup(name)) == NULL)
+			out_of_mem();
+
+		/*
+		 * Extract a mask from either a "/<masklen>" suffix, or
+		 * from the class of an IPv4 address.
+		 */
 		if (opt_flags & OP_MASKLEN) {
 			preflen = strtol(prefp, NULL, 10);
-			if (preflen == LONG_MIN && errno == ERANGE)
+			if (preflen < 0L || preflen == LONG_MAX)
+				goto fail;
+			bcopy(sa, &net->nt_mask, sa->sa_len);
+			if (makemask(&net->nt_mask, (int)preflen) != 0)
 				goto fail;
-			net->nt_mask = (int)preflen;
+			opt_flags |= OP_HAVEMASK;
 			*p = '/';
-		}
+		} else if (sa->sa_family == AF_INET &&
+		    (opt_flags & OP_MASK) == 0) {
+			in_addr_t addr;
+
+			addr = ((struct sockaddr_in *)sa)->sin_addr.s_addr;
+			if (IN_CLASSA(addr))
+				preflen = 8;
+			else if (IN_CLASSB(addr))
+				preflen = 16;
+			else if (IN_CLASSC(addr))
+				preflen = 24;
+			else if (IN_CLASSD(addr))
+				preflen = 28;
+			else
+				preflen = 32;	/* XXX */
 
-		if (np)
-			name = np->n_name;
-		else {
-			if (getnameinfo(sa, sa->sa_len, netname, sizeof netname,
-			   NULL, 0, ninumeric) != 0)
-				strlcpy(netname, "?", sizeof(netname));
-			name = netname;
+			bcopy(sa, &net->nt_mask, sa->sa_len);
+			makemask(&net->nt_mask, (int)preflen);
+			opt_flags |= OP_HAVEMASK;
 		}
-		net->nt_name = strdup(name);
-		memcpy(&net->nt_net, sa, sa->sa_len);
-	}
-
-	if (!maskflg && sa->sa_family == AF_INET &&
-	    !(opt_flags & (OP_MASK|OP_MASKLEN))) {
-		sinp = (struct sockaddr_in *)sa;
-		if (IN_CLASSA(sinp->sin_addr.s_addr))
-			net->nt_mask = 8;
-		else if (IN_CLASSB(sinp->sin_addr.s_addr))
-			net->nt_mask = 16;
-		else if (IN_CLASSC(sinp->sin_addr.s_addr))
-			net->nt_mask = 24;
-		else if (IN_CLASSD(sinp->sin_addr.s_addr))
-			net->nt_mask = 28;
-		else
-			net->nt_mask = 32;       /* XXX */
 	}
 
 	if (ai)
@@ -2306,8 +2277,16 @@ check_options(dp)
 	    return (1);
 	}
 	if ((opt_flags & OP_MASK) && (opt_flags & OP_NET) == 0) {
-	    syslog(LOG_ERR, "-mask requires -net");
-	    return (1);
+		syslog(LOG_ERR, "-mask requires -network");
+		return (1);
+	}
+	if ((opt_flags & OP_NET) && (opt_flags & OP_HAVEMASK) == 0) {
+		syslog(LOG_ERR, "-network requires mask specification");
+		return (1);
+	}
+	if ((opt_flags & OP_MASK) && (opt_flags & OP_MASKLEN)) {
+		syslog(LOG_ERR, "-mask and /masklen are mutually exclusive");
+		return (1);
 	}
 	if ((opt_flags & OP_ALLDIRS) && dp->dp_left) {
 	    syslog(LOG_ERR, "-alldirs has multiple directories");
@@ -2342,137 +2321,122 @@ check_dirpath(dirp)
 	return (ret);
 }
 
-static int
-netpartcmp(struct sockaddr *s1, struct sockaddr *s2, int bitlen)
+/*
+ * Make a netmask according to the specified prefix length. The ss_family
+ * and other non-address fields must be initialised before calling this.
+ */
+int
+makemask(struct sockaddr_storage *ssp, int bitlen)
 {
-	void *src, *dst;
+	u_char *p;
+	int bits, i, len;
 
-	if (s1->sa_family != s2->sa_family)
-		return 1;
+	if ((p = sa_rawaddr((struct sockaddr *)ssp, &len)) == NULL)
+		return (-1);
+	if (bitlen > len * NBBY)
+		return (-1);
 
-	switch (s1->sa_family) {
-	case AF_INET:
-		src = &((struct sockaddr_in *)s1)->sin_addr;
-		dst = &((struct sockaddr_in *)s2)->sin_addr;
-		if (bitlen > sizeof(((struct sockaddr_in *)s1)->sin_addr) * 8)
-			return 1;
-		break;
-	case AF_INET6:
-		src = &((struct sockaddr_in6 *)s1)->sin6_addr;
-		dst = &((struct sockaddr_in6 *)s2)->sin6_addr;
-		if (((struct sockaddr_in6 *)s1)->sin6_scope_id !=
-		   ((struct sockaddr_in6 *)s2)->sin6_scope_id)
-			return 1;
-		if (bitlen > sizeof(((struct sockaddr_in6 *)s1)->sin6_addr) * 8)
-			return 1;
-		break;
-	default:
-		return 1;
+	for (i = 0; i < len; i++) {
+		bits = (bitlen > NBBY) ? NBBY : bitlen;
+		*p++ = (1 << bits) - 1;
+		bitlen -= bits;
 	}
-
-	return bitcmp(src, dst, bitlen);
+	return 0;
 }
 
-static int
-allones(struct sockaddr_storage *ssp, int bitlen)
+/*
+ * Check that the sockaddr is a valid netmask. Returns 0 if the mask
+ * is acceptable (i.e. of the form 1...10....0).
+ */
+int
+checkmask(struct sockaddr *sa)
 {
-	u_int8_t *p;
-	int bytelen, bitsleft, i;
-	int zerolen;
+	u_char *mask;
+	int i, len;
 
-	switch (ssp->ss_family) {
-	case AF_INET:
-		p = (u_int8_t *)&((struct sockaddr_in *)ssp)->sin_addr;
-		zerolen = sizeof (((struct sockaddr_in *)ssp)->sin_addr);
-		break;
-	case AF_INET6:
-		p = (u_int8_t *)&((struct sockaddr_in6 *)ssp)->sin6_addr;
-		zerolen = sizeof (((struct sockaddr_in6 *)ssp)->sin6_addr);
-	break;
-	default:
-		return -1;
-	}
-
-	memset(p, 0, zerolen);
-
-	bytelen = bitlen / 8;
-	bitsleft = bitlen % 8;
-
-	if (bytelen > zerolen)
-		return -1;
+	if ((mask = sa_rawaddr(sa, &len)) == NULL)
+		return (-1);
 
-	for (i = 0; i < bytelen; i++)
-		*p++ = 0xff;
-
-	for (i = 0; i < bitsleft; i++)
-		*p |= 1 << (7 - i);
-
-	return 0;
+	for (i = 0; i < len; i++)
+		if (mask[i] != 0xff)
+			break;
+	if (i < len) {
+		if (~mask[i] & (u_char)(~mask[i] + 1))
+			return (-1);
+		i++;
+	}
+	for (; i < len; i++)
+		if (mask[i] != 0)
+			return (-1);
+	return (0);
 }
 
-static int
-countones(struct sockaddr *sa)
+/*
+ * Compare two sockaddrs according to a specified mask. Return zero if
+ * `sa1' matches `sa2' when filtered by the netmask in `samask'.
+ * If samask is NULL, perform a full comparision.
+ */
+int
+sacmp(struct sockaddr *sa1, struct sockaddr *sa2, struct sockaddr *samask)
 {
-	void *mask;
-	int i, bits = 0, bytelen;
-	u_int8_t *p;
+	unsigned char *p1, *p2, *mask;
+	int len, i;
 
-	switch (sa->sa_family) {
-	case AF_INET:
-		mask = (u_int8_t *)&((struct sockaddr_in *)sa)->sin_addr;
-		bytelen = 4;
-		break;
+	if (sa1->sa_family != sa2->sa_family ||
+	    (p1 = sa_rawaddr(sa1, &len)) == NULL ||
+	    (p2 = sa_rawaddr(sa2, NULL)) == NULL)
+		return (1);
+
+	switch (sa1->sa_family) {
 	case AF_INET6:
-		mask = (u_int8_t *)&((struct sockaddr_in6 *)sa)->sin6_addr;
-		bytelen = 16;
+		if (((struct sockaddr_in6 *)sa1)->sin6_scope_id !=
+		    ((struct sockaddr_in6 *)sa2)->sin6_scope_id)
+			return (1);
 		break;
-	default:
-		return 0;
 	}
 
-	p = mask;
+	/* Simple binary comparison if no mask specified. */
+	if (samask == NULL)
+		return (memcmp(p1, p2, len));
 
-	for (i = 0; i < bytelen; i++, p++) {
-		if (*p != 0xff) {
-			for (bits = 0; bits < 8; bits++) {
-				if (!(*p & (1 << (7 - bits))))
-					break;
-			}
-			break;
-		}
-	}
+	/* Set up the mask, and do a mask-based comparison. */
+	if (sa1->sa_family != samask->sa_family ||
+	    (mask = sa_rawaddr(samask, NULL)) == NULL)
+		return (1);
 
-	return (i * 8 + bits);
+	for (i = 0; i < len; i++)
+		if ((p1[i] & mask[i]) != (p2[i] & mask[i]))
+			return (1);
+	return (0);
 }
 
-static int
-sacmp(struct sockaddr *sa1, struct sockaddr *sa2)
-{
-	void *p1, *p2;
+/*
+ * Return a pointer to the part of the sockaddr that contains the
+ * raw address, and set *nbytes to its length in bytes. Returns
+ * NULL if the address family is unknown.
+ */
+void *
+sa_rawaddr(struct sockaddr *sa, int *nbytes) {
+	void *p;
 	int len;
 
-	if (sa1->sa_family != sa2->sa_family)
-		return 1;
-
-	switch (sa1->sa_family) {
+	switch (sa->sa_family) {
 	case AF_INET:
-		p1 = &((struct sockaddr_in *)sa1)->sin_addr;
-		p2 = &((struct sockaddr_in *)sa2)->sin_addr;
-		len = 4;
+		len = sizeof(((struct sockaddr_in *)sa)->sin_addr);
+		p = &((struct sockaddr_in *)sa)->sin_addr;
 		break;
 	case AF_INET6:
-		p1 = &((struct sockaddr_in6 *)sa1)->sin6_addr;
-		p2 = &((struct sockaddr_in6 *)sa2)->sin6_addr;
-		len = 16;
-		if (((struct sockaddr_in6 *)sa1)->sin6_scope_id !=
-		    ((struct sockaddr_in6 *)sa2)->sin6_scope_id)
-			return 1;
+		len = sizeof(((struct sockaddr_in6 *)sa)->sin6_addr);
+		p = &((struct sockaddr_in6 *)sa)->sin6_addr;
 		break;
 	default:
-		return 1;
+		p = NULL;
+		len = 0;
 	}
 
-	return memcmp(p1, p2, len);
+	if (nbytes != NULL)
+		*nbytes = len;
+	return (p);
 }
 
 void