[PATCH v8 02/14] passt, pasta: Introduce unified multi-address data structures

[Jon Maloy <jmaloy@redhat.com>]

As preparation for supporting multiple addresses per interface,
we replace the single addr/prefix_len fields with an array. The
array consists of a new struct inany_addr_entry containing an
address and prefix length, both in inany_addr format.

Despite some code refactoring, there are only two real functional
changes:
- The indicated IPv6 prefix length is now properly stored, instead
  of being ignored and overridden with the hardcoded value 64, as
  has been the case until now.
- Since even IPv4 addresses now are stored in IPv6 format, we
  also store the corresponding prefix length in that format,
  i.e. using the range [96,128] instead of [0,32].

In conf_ip6(), the explicit IN6_IS_ADDR_UNSPECIFIED() check on the
address at the end of the function is no longer needed: for
host-discovered addresses, it is now checked inside the if (!a) block
before calling fwd_set_addr(); for user-provided addresses (via -a),
validation already rejects unspecified addresses at parse time.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>

---
v2: -Using inany_addr instead of protocol specific addresses as
     entry address field.

v3: -Merging into one array, directly in struct ctx
    -Changed prefix_len and flags fields in struct inany_addr_entry
     to uint8_t, since that makes the struct directly migratable

v4: -Updated according to changes in previous commits
    -Updated according to feedback from David G.
    -Squashed IP4_MASK macro commit into this one

v6: -Renamed and moved some definitions
    -Introduced fwd_set_addr() and fwd_get_addr() already in this commit
    -Eliminated first_v4/v6() functions, replaced with fwd_get_addr()
    -Some other changes as suggested by David G.
    -I kept the flag CONF_ADDR_LINKLOCAL, since it will be
     needed later in an address selection function.

v7: -Introduced CONF_ADDR_GENERATED flag
    -Other fixes based on feedback from David and Stefano.
    -I changed signature of inany_prefix_len(), but I did not change
     its semantics, since the premise of David's comment is wrong: the
     caller does *not* explicitly know he is dealing with an IPv4 address.
     In fact, there are examples later in this series where it may be an
     IPv6 address, and the caller just trusts he gets the return value in
     the appropriate format.
    -Intoduced the inverse of inany_prefix_len(), called inany_prefix_len6()
     which always returns the prefix in IPv6 or mapped IPv4 format.
     The name of the function isn't great, but any alternative I came up
     with became too long to be practical.

v8: -Added inany_prefix_v4() (David G.) to extract IPv4 address and
     prefix length simultaneously, replacing inany_prefix_len().
    -Removed both inany_prefix_len() and inany_prefix_len6()
     auto-detecting functions. Prefix length attached to an inany is
     now always stored in IPv6 format (96-128 for IPv4-mapped).
    -fwd_set_addr() now requires prefix_len in IPv6 format; callers
     updated to pass prefix_len + 96 for IPv4 addresses.
    -Fixed -n option to store prefix_len in IPv6 format.
    -Fixed addr_seen regression: when address was set via -a,
     addr_seen was not initialised in conf_ip4().
    -Replaced assert() with graceful no-op in dhcp.c and ndp.c when
     no address is configured (David G.).
    -Note: addr_seen is still initialised both at conf_ip*() time
     and at DHCP/DHCPv6 send time (David's concern). This
     inconsistency will be addressed in a follow-up.
    -Introduced a new CONF_ADDR_ANY macro tobe used for address
     selection, as suggested by Stefano.
    -Deferred introduction of an explicit scope field (replacing
     CONF_ADDR_LINKLOCAL flag) to a later commit or series.
---
 arp.c    |  12 ++++-
 conf.c   | 142 +++++++++++++++++++++++++++++++------------------------
 dhcp.c   |  19 ++++++--
 dhcpv6.c |  15 ++++--
 fwd.c    | 111 +++++++++++++++++++++++++++++++++++--------
 fwd.h    |   4 ++
 inany.h  |  28 +++++++++++
 ip.h     |   2 +
 ndp.c    |  19 ++++++--
 passt.h  |  66 +++++++++++++++++++++++---
 pasta.c  |  26 ++++++----
 tap.c    |   8 +++-
 12 files changed, 342 insertions(+), 110 deletions(-)

diff --git a/arp.c b/arp.c
index bb042e95..0392861d 100644
--- a/arp.c
+++ b/arp.c
@@ -41,6 +41,8 @@
 static bool ignore_arp(const struct ctx *c,
 		       const struct arphdr *ah, const struct arpmsg *am)
 {
+	const struct guest_addr *a;
+
 	if (ah->ar_hrd != htons(ARPHRD_ETHER)	||
 	    ah->ar_pro != htons(ETH_P_IP)	||
 	    ah->ar_hln != ETH_ALEN		||
@@ -54,7 +56,8 @@ static bool ignore_arp(const struct ctx *c,
 		return true;
 
 	/* Don't resolve the guest's assigned address, either. */
-	if (!memcmp(am->tip, &c->ip4.addr, sizeof(am->tip)))
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	if (a && !memcmp(am->tip, inany_v4(&a->addr), sizeof(am->tip)))
 		return true;
 
 	return false;
@@ -123,12 +126,17 @@ int arp(const struct ctx *c, struct iov_tail *data)
  */
 void arp_send_init_req(const struct ctx *c)
 {
+	const struct guest_addr *a;
 	struct {
 		struct ethhdr eh;
 		struct arphdr ah;
 		struct arpmsg am;
 	} __attribute__((__packed__)) req;
 
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	if (!a)
+		return;
+
 	/* Ethernet header */
 	req.eh.h_proto = htons(ETH_P_ARP);
 	memcpy(req.eh.h_dest, MAC_BROADCAST, sizeof(req.eh.h_dest));
@@ -145,7 +153,7 @@ void arp_send_init_req(const struct ctx *c)
 	memcpy(req.am.sha,	c->our_tap_mac,		sizeof(req.am.sha));
 	memcpy(req.am.sip,	&c->ip4.our_tap_addr,	sizeof(req.am.sip));
 	memcpy(req.am.tha,	MAC_BROADCAST,		sizeof(req.am.tha));
-	memcpy(req.am.tip,	&c->ip4.addr,		sizeof(req.am.tip));
+	memcpy(req.am.tip,	inany_v4(&a->addr),	sizeof(req.am.tip));
 
 	debug("Sending initial ARP request for guest MAC address");
 	tap_send_single(c, &req, sizeof(req));
diff --git a/conf.c b/conf.c
index 4755a9f4..ac8facc8 100644
--- a/conf.c
+++ b/conf.c
@@ -373,13 +373,16 @@ static int conf_ip4_prefix(const char *arg)
 
 /**
  * conf_ip4() - Verify or detect IPv4 support, get relevant addresses
+ * @c:		Execution context
  * @ifi:	Host interface to attempt (0 to determine one)
- * @ip4:	IPv4 context (will be written)
  *
  * Return: interface index for IPv4, or 0 on failure.
  */
-static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4)
+static unsigned int conf_ip4(struct ctx *c, unsigned int ifi)
 {
+	const struct guest_addr *a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	struct ip4_ctx *ip4 = &c->ip4;
+
 	if (!ifi)
 		ifi = nl_get_ext_if(nl_sock, AF_INET);
 
@@ -398,60 +401,58 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4)
 		}
 	}
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr)) {
+	if (!a) {
+		struct in_addr addr;
+		int prefix_len;
 		int rc = nl_addr_get(nl_sock, ifi, AF_INET,
-				     &ip4->addr, &ip4->prefix_len, NULL);
+				     &addr, &prefix_len, NULL);
 		if (rc < 0) {
 			debug("Couldn't discover IPv4 address: %s",
 			      strerror_(-rc));
 			return 0;
 		}
-	}
+		if (IN4_IS_ADDR_UNSPECIFIED(&addr))
+			return 0;
 
-	if (!ip4->prefix_len) {
-		in_addr_t addr = ntohl(ip4->addr.s_addr);
-		if (IN_CLASSA(addr))
-			ip4->prefix_len = (32 - IN_CLASSA_NSHIFT);
-		else if (IN_CLASSB(addr))
-			ip4->prefix_len = (32 - IN_CLASSB_NSHIFT);
-		else if (IN_CLASSC(addr))
-			ip4->prefix_len = (32 - IN_CLASSC_NSHIFT);
-		else
-			ip4->prefix_len = 32;
+		fwd_set_addr(c, &inany_from_v4(addr), CONF_ADDR_HOST,
+			     prefix_len + 96);
 	}
 
-	ip4->addr_seen = ip4->addr;
-
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	ip4->addr_seen = *inany_v4(&a->addr);
 	ip4->our_tap_addr = ip4->guest_gw;
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr))
-		return 0;
-
 	return ifi;
 }
 
 /**
  * conf_ip4_local() - Configure IPv4 addresses and attributes for local mode
- * @ip4:	IPv4 context (will be written)
+ * @c:		Execution context (will be written)
  */
-static void conf_ip4_local(struct ip4_ctx *ip4)
+static void conf_ip4_local(struct ctx *c)
 {
-	ip4->addr_seen = ip4->addr = IP4_LL_GUEST_ADDR;
-	ip4->our_tap_addr = ip4->guest_gw = IP4_LL_GUEST_GW;
-	ip4->prefix_len = IP4_LL_PREFIX_LEN;
+	struct ip4_ctx *ip4 = &c->ip4;
 
+	ip4->addr_seen = IP4_LL_GUEST_ADDR;
+	ip4->our_tap_addr = ip4->guest_gw = IP4_LL_GUEST_GW;
 	ip4->no_copy_addrs = ip4->no_copy_routes = true;
+	fwd_set_addr(c, &inany_from_v4(IP4_LL_GUEST_ADDR),
+		     CONF_ADDR_GENERATED | CONF_ADDR_LINKLOCAL,
+		     IP4_LL_PREFIX_LEN + 96);
 }
 
 /**
  * conf_ip6() - Verify or detect IPv6 support, get relevant addresses
+ * @c:		Execution context
  * @ifi:	Host interface to attempt (0 to determine one)
- * @ip6:	IPv6 context (will be written)
  *
  * Return: interface index for IPv6, or 0 on failure.
  */
-static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6)
+static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
 {
+	struct ip6_ctx *ip6 = &c->ip6;
+	const struct guest_addr *a;
+	union inany_addr addr;
 	int prefix_len = 0;
 	int rc;
 
@@ -472,21 +473,28 @@ static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6)
 		}
 	}
 
-	rc = nl_addr_get(nl_sock, ifi, AF_INET6,
-			 IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ? &ip6->addr : NULL,
+	rc = nl_addr_get(nl_sock, ifi, AF_INET6, &addr.a6,
 			 &prefix_len, &ip6->our_tap_ll);
 	if (rc < 0) {
 		debug("Couldn't discover IPv6 address: %s", strerror_(-rc));
 		return 0;
 	}
 
-	ip6->addr_seen = ip6->addr;
+	a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+	if (!a) {
+		if (IN6_IS_ADDR_UNSPECIFIED(&addr))
+			return 0;
+
+		fwd_set_addr(c, &addr, CONF_ADDR_HOST, prefix_len);
+		ip6->addr_seen = addr.a6;
+	} else {
+		ip6->addr_seen = a->addr.a6;
+	}
 
 	if (IN6_IS_ADDR_LINKLOCAL(&ip6->guest_gw))
 		ip6->our_tap_ll = ip6->guest_gw;
 
-	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ||
-	    IN6_IS_ADDR_UNSPECIFIED(&ip6->our_tap_ll))
+	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->our_tap_ll))
 		return 0;
 
 	return ifi;
@@ -494,13 +502,13 @@ static unsigned int conf_ip6(unsigned int ifi, struct ip6_ctx *ip6)
 
 /**
  * conf_ip6_local() - Configure IPv6 addresses and attributes for local mode
- * @ip6:	IPv6 context (will be written)
+ * @c:		Execution context (will be written)
  */
-static void conf_ip6_local(struct ip6_ctx *ip6)
+static void conf_ip6_local(struct ctx *c)
 {
-	ip6->our_tap_ll = ip6->guest_gw = IP6_LL_GUEST_GW;
+	c->ip6.our_tap_ll = c->ip6.guest_gw = IP6_LL_GUEST_GW;
 
-	ip6->no_copy_addrs = ip6->no_copy_routes = true;
+	c->ip6.no_copy_addrs = c->ip6.no_copy_routes = true;
 }
 
 /**
@@ -784,6 +792,7 @@ enum passt_modes conf_mode(int argc, char *argv[])
 static void conf_print(const struct ctx *c)
 {
 	char buf[INANY_ADDRSTRLEN];
+	const struct guest_addr *a;
 	int i;
 
 	if (c->fd_control_listen >= 0)
@@ -831,16 +840,19 @@ static void conf_print(const struct ctx *c)
 			     inet_ntop(AF_INET, &c->ip4.map_host_loopback,
 				       buf, sizeof(buf)));
 
-		if (!c->no_dhcp) {
+		a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+		if (a && !c->no_dhcp) {
 			uint32_t mask;
+			int plen = 0;
 
-			mask = htonl(0xffffffff << (32 - c->ip4.prefix_len));
+			inany_prefix_v4(&a->addr, a->prefix_len, &plen);
+			mask = IN4_MASK(plen);
 
 			info("DHCP:");
 			info("    assign: %s",
-			     inet_ntop(AF_INET, &c->ip4.addr, buf, sizeof(buf)));
+			     inany_ntop(&a->addr, buf, sizeof(buf)));
 			info("    mask: %s",
-			     inet_ntop(AF_INET, &mask,        buf, sizeof(buf)));
+			     inet_ntop(AF_INET, &mask, buf, sizeof(buf)));
 			info("    router: %s",
 			     inet_ntop(AF_INET, &c->ip4.guest_gw,
 				       buf, sizeof(buf)));
@@ -851,8 +863,8 @@ static void conf_print(const struct ctx *c)
 				break;
 			if (!i)
 				info("DNS:");
-			inet_ntop(AF_INET, &c->ip4.dns[i], buf, sizeof(buf));
-			info("    %s", buf);
+			info("    %s", inet_ntop(AF_INET, &c->ip4.dns[i],
+						 buf, sizeof(buf)));
 		}
 
 		for (i = 0; *c->dns_search[i].n; i++) {
@@ -877,13 +889,15 @@ static void conf_print(const struct ctx *c)
 		else
 			goto dns6;
 
-		info("    assign: %s",
-		     inet_ntop(AF_INET6, &c->ip6.addr, buf, sizeof(buf)));
+		a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY,
+				 CONF_ADDR_LINKLOCAL);
+		if (a)
+			info("    assign: %s",
+			     inany_ntop(&a->addr, buf, sizeof(buf)));
 		info("    router: %s",
 		     inet_ntop(AF_INET6, &c->ip6.guest_gw, buf, sizeof(buf)));
 		info("    our link-local: %s",
-		     inet_ntop(AF_INET6, &c->ip6.our_tap_ll,
-			       buf, sizeof(buf)));
+		     inet_ntop(AF_INET6, &c->ip6.our_tap_ll, buf, sizeof(buf)));
 
 dns6:
 		for (i = 0; i < ARRAY_SIZE(c->ip6.dns); i++) {
@@ -891,8 +905,10 @@ dns6:
 			    break;
 			if (!i)
 				info("DNS:");
-			inet_ntop(AF_INET6, &c->ip6.dns[i], buf, sizeof(buf));
-			info("    %s", buf);
+			info("    %s",
+			     inet_ntop(AF_INET6, &c->ip6.dns[i],
+				       buf, sizeof(buf)));
+
 		}
 
 		for (i = 0; *c->dns_search[i].n; i++) {
@@ -1580,21 +1596,19 @@ void conf(struct ctx *c, int argc, char **argv)
 			    IN6_IS_ADDR_V4COMPAT(&addr.a6))
 				die("Invalid address: %s", optarg);
 
+			/* Legacy behaviour: replace existing address if any */
+			fwd_set_addr(c, &addr, CONF_ADDR_USER, prefix_len);
 			if (inany_v4(&addr)) {
-				c->ip4.addr = *inany_v4(&addr);
-				c->ip4.prefix_len = prefix_len - 96;
+				c->ip4.no_copy_addrs = true;
 				c->ip4.addr_fixed = true;
-				if (c->mode == MODE_PASTA)
-					c->ip4.no_copy_addrs = true;
 			} else {
-				c->ip6.addr = addr.a6;
+				c->ip6.no_copy_addrs = true;
 				c->ip6.addr_fixed = true;
-				if (c->mode == MODE_PASTA)
-					c->ip6.no_copy_addrs = true;
 			}
 			break;
 		}
 		case 'n': {
+			struct guest_addr *a;
 			int plen;
 
 			if (addr_has_prefix_len)
@@ -1604,8 +1618,12 @@ void conf(struct ctx *c, int argc, char **argv)
 			if (plen < 0)
 				die("Invalid prefix length: %s", optarg);
 
-			prefix_len_from_opt = plen + 96;
-			c->ip4.prefix_len = plen;
+			prefix_len_from_opt = plen;
+
+			for_each_addr(a, c->addrs, c->addr_count, AF_INET) {
+				a->prefix_len = plen + 96;
+				break;
+			}
 			break;
 		}
 		case 'M':
@@ -1801,9 +1819,9 @@ void conf(struct ctx *c, int argc, char **argv)
 
 	nl_sock_init(c, false);
 	if (!v6_only && !c->splice_only)
-		c->ifi4 = conf_ip4(ifi4, &c->ip4);
+		c->ifi4 = conf_ip4(c, ifi4);
 	if (!v4_only && !c->splice_only)
-		c->ifi6 = conf_ip6(ifi6, &c->ip6);
+		c->ifi6 = conf_ip6(c, ifi6);
 
 	if (c->ifi4 && c->mtu < IPV4_MIN_MTU) {
 		warn("MTU %"PRIu16" is too small for IPv4 (minimum %u)",
@@ -1826,7 +1844,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	if (!c->ifi4 && !v6_only) {
 		if (!c->splice_only) {
 			info("IPv4: no external interface as template, use local mode");
-			conf_ip4_local(&c->ip4);
+			conf_ip4_local(c);
 		}
 		c->ifi4 = -1;
 	}
@@ -1834,7 +1852,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	if (!c->ifi6 && !v4_only) {
 		if (!c->splice_only) {
 			info("IPv6: no external interface as template, use local mode");
-			conf_ip6_local(&c->ip6);
+			conf_ip6_local(c);
 		}
 		c->ifi6 = -1;
 	}
@@ -1905,7 +1923,7 @@ void conf(struct ctx *c, int argc, char **argv)
 	if (!c->ifi6) {
 		c->no_ndp = 1;
 		c->no_dhcpv6 = 1;
-	} else if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) {
+	} else if (!fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0)) {
 		c->no_dhcpv6 = 1;
 	}
 
diff --git a/dhcp.c b/dhcp.c
index 1ff8cba9..727485f7 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -303,6 +303,7 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
 int dhcp(const struct ctx *c, struct iov_tail *data)
 {
 	char macstr[ETH_ADDRSTRLEN];
+	const struct guest_addr *a;
 	size_t mlen, dlen, opt_len;
 	struct in_addr mask, dst;
 	struct ethhdr eh_storage;
@@ -313,8 +314,10 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	const struct udphdr *uh;
 	struct msg m_storage;
 	struct msg const *m;
+	struct in_addr addr;
 	struct msg reply;
 	unsigned int i;
+	int plen;
 
 	eh = IOV_REMOVE_HEADER(data, eh_storage);
 	iph = IOV_PEEK_HEADER(data, iph_storage);
@@ -344,6 +347,14 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	    m->op != BOOTREQUEST)
 		return -1;
 
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_USER, 0);
+	if (!a)
+		a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	if (!a)
+		return -1;
+
+	addr = *inany_prefix_v4(&a->addr, a->prefix_len, &plen);
+
 	reply.op		= BOOTREPLY;
 	reply.htype		= m->htype;
 	reply.hlen		= m->hlen;
@@ -352,7 +363,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	reply.secs		= 0;
 	reply.flags		= m->flags;
 	reply.ciaddr		= m->ciaddr;
-	reply.yiaddr		= c->ip4.addr;
+	reply.yiaddr		= addr;
 	reply.siaddr		= 0;
 	reply.giaddr		= m->giaddr;
 	memcpy(&reply.chaddr,	m->chaddr,	sizeof(reply.chaddr));
@@ -404,7 +415,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 
 	info("    from %s", eth_ntop(m->chaddr, macstr, sizeof(macstr)));
 
-	mask.s_addr = htonl(0xffffffff << (32 - c->ip4.prefix_len));
+	mask.s_addr = IN4_MASK(plen);
 	memcpy(opts[1].s,  &mask,                sizeof(mask));
 	memcpy(opts[3].s,  &c->ip4.guest_gw,     sizeof(c->ip4.guest_gw));
 	memcpy(opts[54].s, &c->ip4.our_tap_addr, sizeof(c->ip4.our_tap_addr));
@@ -412,7 +423,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	/* If the gateway is not on the assigned subnet, send an option 121
 	 * (Classless Static Routing) adding a dummy route to it.
 	 */
-	if ((c->ip4.addr.s_addr & mask.s_addr)
+	if ((addr.s_addr & mask.s_addr)
 	    != (c->ip4.guest_gw.s_addr & mask.s_addr)) {
 		/* a.b.c.d/32:0.0.0.0, 0:a.b.c.d */
 		opts[121].slen = 14;
@@ -471,7 +482,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	if (m->flags & FLAG_BROADCAST)
 		dst = in4addr_broadcast;
 	else
-		dst = c->ip4.addr;
+		dst = addr;
 
 	tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, &reply, dlen);
 
diff --git a/dhcpv6.c b/dhcpv6.c
index 29c7e320..f64cbc24 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -318,7 +318,7 @@ static bool dhcpv6_opt(struct iov_tail *data, uint16_t type)
  *         false otherwise and @data is unmodified
  */
 static bool dhcpv6_ia_notonlink(struct iov_tail *data,
-				struct in6_addr *la)
+				const struct in6_addr *la)
 {
 	int ia_types[2] = { OPT_IA_NA, OPT_IA_TA };
 	struct opt_ia_addr opt_addr_storage;
@@ -567,6 +567,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 	struct opt_hdr client_id_storage;
 	/* cppcheck-suppress [variableScope,unmatchedSuppression] */
 	struct opt_ia_na ia_storage;
+	const struct guest_addr *a;
 	const struct in6_addr *src;
 	struct msg_hdr mh_storage;
 	const struct msg_hdr *mh;
@@ -574,6 +575,8 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 	const struct udphdr *uh;
 	size_t mlen, n;
 
+	a = fwd_get_addr(c, AF_INET6, 0, CONF_ADDR_LINKLOCAL);
+
 	uh = IOV_REMOVE_HEADER(data, uh_storage);
 	if (!uh)
 		return -1;
@@ -627,7 +630,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 		if (mh->type == TYPE_CONFIRM && server_id)
 			return -1;
 
-		if (dhcpv6_ia_notonlink(data, &c->ip6.addr)) {
+		if (a && dhcpv6_ia_notonlink(data, &a->addr.a6)) {
 
 			dhcpv6_send_ia_notonlink(c, saddr, data,
 						 &client_id_base,
@@ -682,7 +685,8 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 	resp.hdr.xid = mh->xid;
 
 	tap_udp6_send(c, src, 547, saddr, 546, mh->xid, &resp, n);
-	c->ip6.addr_seen = c->ip6.addr;
+	if (a)
+		c->ip6.addr_seen = a->addr.a6;
 
 	return 1;
 }
@@ -694,6 +698,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 void dhcpv6_init(const struct ctx *c)
 {
 	time_t y2k = 946684800; /* Epoch to 2000-01-01T00:00:00Z, no mktime() */
+	const struct guest_addr *a;
 	uint32_t duid_time;
 
 	duid_time = htonl(difftime(time(NULL), y2k));
@@ -706,5 +711,7 @@ void dhcpv6_init(const struct ctx *c)
 	memcpy(resp_not_on_link.server_id.duid_lladdr,
 	       c->our_tap_mac, sizeof(c->our_tap_mac));
 
-	resp.ia_addr.addr	= c->ip6.addr;
+	a = fwd_get_addr(c, AF_INET6, 0, CONF_ADDR_LINKLOCAL);
+	if (a)
+		resp.ia_addr.addr = a->addr.a6;
 }
diff --git a/fwd.c b/fwd.c
index 042158cf..f2ca34c2 100644
--- a/fwd.c
+++ b/fwd.c
@@ -243,6 +243,61 @@ void fwd_neigh_table_init(const struct ctx *c)
 		fwd_neigh_table_update(c, &mga, c->our_tap_mac, true);
 }
 
+/**
+ * fwd_set_addr() - Add or update an address in the unified address array
+ * @c:		Execution context
+ * @addr:	Address to add (IPv4-mapped or IPv6)
+ * @flags:	CONF_ADDR_* flags for this address
+ * @prefix_len:	Prefix length in IPv6 format (96-128 for IPv4-mapped)
+ *
+ * Find the first existing entry of the same address family and
+ * overwrite it, or create a new one if none exists
+ */
+void fwd_set_addr(struct ctx *c, const union inany_addr *addr,
+		  uint8_t flags, int prefix_len)
+{
+	struct guest_addr *a;
+
+	for_each_addr(a, c->addrs, c->addr_count, inany_af(addr)) {
+		goto found;
+	}
+
+	if (c->addr_count >= MAX_GUEST_ADDRS)
+		return;
+
+	a = &c->addrs[c->addr_count++];
+
+found:
+	a->addr = *addr;
+	a->prefix_len = prefix_len;
+	a->flags = flags;
+}
+
+/**
+ * fwd_get_addr() - Get guest address entry matching criteria
+ * @c:		Execution context
+ * @af:		Address family (AF_INET, AF_INET6, or AF_UNSPEC for any)
+ * @incl:	Required flags (any-match), CONF_ADDR_ANY for any
+ * @excl:	Flags that must not be present
+ *
+ * Return: first address entry matching criteria, or NULL
+ */
+const struct guest_addr *fwd_get_addr(const struct ctx *c, sa_family_t af,
+				      uint8_t incl, uint8_t excl)
+{
+	const struct guest_addr *a;
+
+	for_each_addr(a, c->addrs, c->addr_count, af) {
+		if (!(a->flags & incl))
+			continue;
+		if (a->flags & excl)
+			continue;
+		return a;
+	}
+
+	return NULL;
+}
+
 /* Forwarding table storage, generally accessed via pointers in struct ctx */
 static struct fwd_table fwd_in;
 static struct fwd_table fwd_out;
@@ -794,8 +849,10 @@ static bool is_dns_flow(uint8_t proto, const struct flowside *ini)
  *         translation, false otherwise
  */
 static bool fwd_guest_accessible4(const struct ctx *c,
-				    const struct in_addr *addr)
+				  const struct in_addr *addr)
 {
+	const struct guest_addr *a;
+
 	if (IN4_IS_ADDR_LOOPBACK(addr))
 		return false;
 
@@ -810,7 +867,8 @@ static bool fwd_guest_accessible4(const struct ctx *c,
 	/* For IPv4, addr_seen is initialised to addr, so is always a valid
 	 * address
 	 */
-	if (IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr) ||
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+	if ((a && IN4_ARE_ADDR_EQUAL(addr, inany_v4(&a->addr))) ||
 	    IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr_seen))
 		return false;
 
@@ -828,10 +886,13 @@ static bool fwd_guest_accessible4(const struct ctx *c,
 static bool fwd_guest_accessible6(const struct ctx *c,
 				  const struct in6_addr *addr)
 {
+	const struct guest_addr *a;
+
 	if (IN6_IS_ADDR_LOOPBACK(addr))
 		return false;
 
-	if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addr))
+	a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+	if (a && IN6_ARE_ADDR_EQUAL(addr, &a->addr.a6))
 		return false;
 
 	/* For IPv6, addr_seen starts unspecified, because we don't know what LL
@@ -876,16 +937,21 @@ static bool fwd_guest_accessible(const struct ctx *c,
 static void nat_outbound(const struct ctx *c, const union inany_addr *addr,
 			 union inany_addr *translated)
 {
-	if (inany_equals4(addr, &c->ip4.map_host_loopback))
+	const struct guest_addr *ga;
+
+	if (inany_equals4(addr, &c->ip4.map_host_loopback)) {
 		*translated = inany_loopback4;
-	else if (inany_equals6(addr, &c->ip6.map_host_loopback))
+	} else if (inany_equals6(addr, &c->ip6.map_host_loopback)) {
 		*translated = inany_loopback6;
-	else if (inany_equals4(addr, &c->ip4.map_guest_addr))
-		*translated = inany_from_v4(c->ip4.addr);
-	else if (inany_equals6(addr, &c->ip6.map_guest_addr))
-		translated->a6 = c->ip6.addr;
-	else
+	} else if (inany_equals4(addr, &c->ip4.map_guest_addr)) {
+		ga = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+		*translated = ga ? ga->addr : inany_any4;
+	} else if (inany_equals6(addr, &c->ip6.map_guest_addr)) {
+		ga = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+		translated->a6 = ga ? ga->addr.a6 : in6addr_any;
+	} else {
 		*translated = *addr;
+	}
 }
 
 /**
@@ -990,16 +1056,23 @@ bool nat_inbound(const struct ctx *c, const union inany_addr *addr,
 	} else if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_host_loopback) &&
 		   inany_equals6(addr, &in6addr_loopback)) {
 		translated->a6 = c->ip6.map_host_loopback;
-	} else if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_guest_addr) &&
-		   inany_equals4(addr, &c->ip4.addr)) {
-		*translated = inany_from_v4(c->ip4.map_guest_addr);
-	} else if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_guest_addr) &&
-		   inany_equals6(addr, &c->ip6.addr)) {
-		translated->a6 = c->ip6.map_guest_addr;
-	} else if (fwd_guest_accessible(c, addr)) {
-		*translated = *addr;
 	} else {
-		return false;
+		const struct guest_addr *ga4, *ga6;
+
+		ga4 = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+		ga6 = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+
+		if (!IN4_IS_ADDR_UNSPECIFIED(&c->ip4.map_guest_addr) &&
+		    ga4 && inany_equals(addr, &ga4->addr)) {
+			*translated = inany_from_v4(c->ip4.map_guest_addr);
+		} else if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.map_guest_addr) &&
+			   ga6 && inany_equals(addr, &ga6->addr)) {
+			translated->a6 = c->ip6.map_guest_addr;
+		} else if (fwd_guest_accessible(c, addr)) {
+			*translated = *addr;
+		} else {
+			return false;
+		}
 	}
 
 	return true;
diff --git a/fwd.h b/fwd.h
index b60697d9..d677440f 100644
--- a/fwd.h
+++ b/fwd.h
@@ -79,5 +79,9 @@ void fwd_neigh_table_free(const struct ctx *c,
 void fwd_neigh_mac_get(const struct ctx *c, const union inany_addr *addr,
 		       uint8_t *mac);
 void fwd_neigh_table_init(const struct ctx *c);
+void fwd_set_addr(struct ctx *c, const union inany_addr *addr,
+		  uint8_t flags, int prefix_len);
+const struct guest_addr *fwd_get_addr(const struct ctx *c, sa_family_t af,
+				      uint8_t incl, uint8_t excl);
 
 #endif /* FWD_H */
diff --git a/inany.h b/inany.h
index 6bf3ecaa..95756eb8 100644
--- a/inany.h
+++ b/inany.h
@@ -102,6 +102,34 @@ static inline struct in_addr *inany_v4(const union inany_addr *addr)
 	return (struct in_addr *)&addr->v4mapped.a4;
 }
 
+/** inany_prefix_v4() - Extract IPv4 address and prefix length from inany
+ * @addr:	IPv4 (as mapped) or IPv6 address
+ * @prefix_len:	Prefix length in IPv6 format (96-128 for IPv4)
+ * @v4_plen:	Set to IPv4 prefix length (0-32) on success
+ *
+ * Return: IPv4 address if @addr is IPv4, NULL otherwise
+ */
+static inline struct in_addr *inany_prefix_v4(const union inany_addr *addr,
+					      int prefix_len, int *v4_plen)
+{
+	struct in_addr *v4 = inany_v4(addr);
+
+	if (!v4)
+		return NULL;
+	*v4_plen = prefix_len - 96;
+	return v4;
+}
+
+/** inany_af - Get address family of IPv[46] address
+ * @addr:	IPv4 or IPv6 address
+ *
+ * Return: AF_INET for IPv4, AF_INET6 for IPv6
+ */
+static inline sa_family_t inany_af(const union inany_addr *addr)
+{
+	return inany_v4(addr) ? AF_INET : AF_INET6;
+}
+
 /** inany_default_prefix_len() - Get default prefix length for address
  * @addr:	IPv4 or iPv6 address
  *
diff --git a/ip.h b/ip.h
index aab9b86a..ac93c543 100644
--- a/ip.h
+++ b/ip.h
@@ -19,6 +19,8 @@
 	(ntohl(((struct in_addr *)(a))->s_addr) >> IN_CLASSA_NSHIFT == IN_LOOPBACKNET)
 #define IN4_IS_ADDR_MULTICAST(a) \
 	(IN_MULTICAST(ntohl(((struct in_addr *)(a))->s_addr)))
+#define IN4_MASK(prefix) \
+	((prefix) <= 0 ? 0 : htonl(0xffffffff << (32 - (prefix))))
 #define IN4_ARE_ADDR_EQUAL(a, b) \
 	(((struct in_addr *)(a))->s_addr == ((struct in_addr *)b)->s_addr)
 #define IN4ADDR_LOOPBACK_INIT \
diff --git a/ndp.c b/ndp.c
index 1f2bcb0c..a6a79055 100644
--- a/ndp.c
+++ b/ndp.c
@@ -257,7 +257,6 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
 			.valid_lifetime		= ~0U,
 			.pref_lifetime		= ~0U,
 		},
-		.prefix = c->ip6.addr,
 		.source_ll = {
 			.header = {
 				.type		= OPT_SRC_L2_ADDR,
@@ -265,8 +264,15 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
 			},
 		},
 	};
+	const struct guest_addr *a;
 	unsigned char *ptr = NULL;
 
+	a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+	if (!a)
+		return;
+
+	ra.prefix = a->addr.a6;
+
 	ptr = &ra.var[0];
 
 	if (c->mtu) {
@@ -460,6 +466,7 @@ first:
  */
 void ndp_send_init_req(const struct ctx *c)
 {
+	const struct guest_addr *a;
 	struct ndp_ns ns = {
 		.ih = {
 			.icmp6_type		= NS,
@@ -468,8 +475,14 @@ void ndp_send_init_req(const struct ctx *c)
 			.icmp6_solicited	= 0, /* Reserved */
 			.icmp6_override		= 0, /* Reserved */
 		},
-		.target_addr = c->ip6.addr
+		.target_addr = IN6ADDR_ANY_INIT
 	};
+
+	a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+	if (!a)
+		return;
+
+	ns.target_addr = a->addr.a6;
 	debug("Sending initial NDP NS request for guest MAC address");
-	ndp_send(c, &c->ip6.addr, &ns, sizeof(ns));
+	ndp_send(c, &a->addr.a6, &ns, sizeof(ns));
 }
diff --git a/passt.h b/passt.h
index 16506dcd..cafa35ea 100644
--- a/passt.h
+++ b/passt.h
@@ -64,11 +64,29 @@ enum passt_modes {
 	MODE_VU,
 };
 
+/* Maximum number of addresses in context address array */
+#define MAX_GUEST_ADDRS		32
+
+/**
+ * struct guest_addr - Unified IPv4/IPv6 address entry
+ * @addr:	IPv4 (as mapped) or IPv6 address
+ * @prefix_len:	Prefix length in IPv6/IPv4-mapped [0,128]/[96,128] format
+ * @flags:	CONF_ADDR_* flags
+ */
+struct guest_addr {
+	union inany_addr addr;
+	uint8_t prefix_len;
+	uint8_t flags;
+#define CONF_ADDR_USER		BIT(0)		/* User set via -a */
+#define CONF_ADDR_HOST		BIT(1)		/* From host interface */
+#define CONF_ADDR_GENERATED	BIT(2)		/* Generated by PASST/PASTA */
+#define CONF_ADDR_LINKLOCAL	BIT(3)		/* Link-local address */
+#define CONF_ADDR_ANY		0xff		/* Match any flag */
+};
+
 /**
  * struct ip4_ctx - IPv4 execution context
- * @addr:		IPv4 address assigned to guest
  * @addr_seen:		Latest IPv4 address seen as source from tap
- * @prefixlen:		IPv4 prefix length (netmask)
  * @guest_gw:		IPv4 gateway as seen by the guest
  * @map_host_loopback:	Outbound connections to this address are NATted to the
  *                      host's 127.0.0.1
@@ -87,9 +105,7 @@ enum passt_modes {
  */
 struct ip4_ctx {
 	/* PIF_TAP addresses */
-	struct in_addr addr;
 	struct in_addr addr_seen;
-	int prefix_len;
 	struct in_addr guest_gw;
 	struct in_addr map_host_loopback;
 	struct in_addr map_guest_addr;
@@ -110,7 +126,6 @@ struct ip4_ctx {
 
 /**
  * struct ip6_ctx - IPv6 execution context
- * @addr:		IPv6 address assigned to guest
  * @addr_seen:		Latest IPv6 global/site address seen as source from tap
  * @addr_ll_seen:	Latest IPv6 link-local address seen as source from tap
  * @guest_gw:		IPv6 gateway as seen by the guest
@@ -131,7 +146,6 @@ struct ip4_ctx {
  */
 struct ip6_ctx {
 	/* PIF_TAP addresses */
-	struct in6_addr addr;
 	struct in6_addr addr_seen;
 	struct in6_addr addr_ll_seen;
 	struct in6_addr guest_gw;
@@ -190,6 +204,8 @@ struct ip6_ctx {
  * @fqdn:		Guest FQDN
  * @ifi6:		Template interface for IPv6, -1: none, 0: IPv6 disabled
  * @ip6:		IPv6 configuration
+ * @addrs:		Unified address array for both IPv4 (mapped) and IPv6
+ * @addr_count:		Number of active entries in @addrs array
  * @pasta_ifn:		Name of namespace interface for pasta
  * @pasta_ifi:		Index of namespace interface for pasta
  * @pasta_conf_ns:	Configure namespace after creating it
@@ -273,6 +289,9 @@ struct ctx {
 	int ifi6;
 	struct ip6_ctx ip6;
 
+	struct guest_addr addrs[MAX_GUEST_ADDRS];
+	int addr_count;
+
 	char pasta_ifn[IF_NAMESIZE];
 	unsigned int pasta_ifi;
 	int pasta_conf_ns;
@@ -317,6 +336,41 @@ struct ctx {
 
 extern struct ctx passt_ctx;
 
+/**
+ * next_addr_idx_() - Find next address index matching family filter
+ * @addrs:	Array of guest addresses
+ * @count:	Number of addresses in array
+ * @i:		Starting index
+ * @af:		Address family filter: AF_INET, AF_INET6, or AF_UNSPEC for all
+ *
+ * Return: next matching index, or count if none found
+ */
+static inline int next_addr_idx_(const struct guest_addr *addrs, int count,
+				 int i, sa_family_t af)
+{
+	for (; i < count; i++) {
+		sa_family_t entry_af;
+
+		entry_af = inany_v4(&addrs[i].addr) ? AF_INET : AF_INET6;
+
+		if (af == AF_UNSPEC || af == entry_af)
+			return i;
+	}
+	return i;
+}
+
+/**
+ * for_each_addr() - Iterate over addresses in array
+ * @a:		Pointer variable for current entry (struct guest_addr *)
+ * @addrs:	Array of guest addresses (e.g., c->addrs)
+ * @count:	Number of addresses (e.g., c->addr_count)
+ * @af:		Address family filter: AF_INET, AF_INET6, or 0 for all
+ */
+#define for_each_addr(a, addrs, count, af)				\
+	for (int i_ = next_addr_idx_((addrs), (count), 0, (af));	\
+	     i_ < (count) && ((a) = &(addrs)[i_], true);		\
+	     i_ = next_addr_idx_((addrs), (count), i_ + 1, (af)))
+
 void proto_update_l2_buf(const unsigned char *eth_d);
 
 #endif /* PASST_H */
diff --git a/pasta.c b/pasta.c
index 4e7ee542..9ef3ac00 100644
--- a/pasta.c
+++ b/pasta.c
@@ -330,6 +330,8 @@ void pasta_ns_conf(struct ctx *c)
 
 	if (c->pasta_conf_ns) {
 		unsigned int flags = IFF_UP;
+		const struct guest_addr *a;
+		int plen = 0;
 
 		if (c->mtu)
 			nl_link_set_mtu(nl_sock_ns, c->pasta_ifi, c->mtu);
@@ -341,10 +343,17 @@ void pasta_ns_conf(struct ctx *c)
 
 		if (c->ifi4) {
 			if (c->ip4.no_copy_addrs) {
-				rc = nl_addr_set(nl_sock_ns, c->pasta_ifi,
-						 AF_INET,
-						 &c->ip4.addr,
-						 c->ip4.prefix_len);
+				a = fwd_get_addr(c, AF_INET, CONF_ADDR_ANY, 0);
+				if (a) {
+					const struct in_addr *v4;
+
+					v4 = inany_prefix_v4(&a->addr,
+							     a->prefix_len,
+							     &plen);
+					rc = nl_addr_set(nl_sock_ns,
+							 c->pasta_ifi, AF_INET,
+							 v4, plen);
+				}
 			} else {
 				rc = nl_addr_dup(nl_sock, c->ifi4,
 						 nl_sock_ns, c->pasta_ifi,
@@ -397,11 +406,12 @@ ipv4_done:
 					  0, IFF_NOARP);
 
 			if (c->ip6.no_copy_addrs) {
-				if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) {
+				a = fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0);
+				if (a)
 					rc = nl_addr_set(nl_sock_ns,
-							 c->pasta_ifi, AF_INET6,
-							 &c->ip6.addr, 64);
-				}
+							 c->pasta_ifi,
+							 AF_INET6, &a->addr.a6,
+							 a->prefix_len);
 			} else {
 				rc = nl_addr_dup(nl_sock, c->ifi6,
 						 nl_sock_ns, c->pasta_ifi,
diff --git a/tap.c b/tap.c
index d4189617..12630f58 100644
--- a/tap.c
+++ b/tap.c
@@ -1005,8 +1005,12 @@ resume:
 				c->ip6.addr_seen = *saddr;
 			}
 
-			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr))
-				c->ip6.addr = *saddr;
+			if (!c->ip6.addr_fixed &&
+			    !fwd_get_addr(c, AF_INET6, CONF_ADDR_ANY, 0)) {
+				union inany_addr addr = { .a6 = *saddr };
+
+				fwd_set_addr(c, &addr, CONF_ADDR_LINKLOCAL, 64);
+			}
 		} else if (!c->ip6.addr_fixed &&
 			   !IN6_IS_ADDR_UNSPECIFIED(saddr)) {
 			c->ip6.addr_seen = *saddr;
-- 
2.52.0