[PATCH v2 2/9] ip: 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 arrays.

- We add an ip4_addr_entry and an ip6_addr_entry struct containing
  address and prefix length.

- We set the array sizes to IP4_MAX_ADDRS=8 and IP6_MAX_ADDRS=16,
  respectively.

The only functional change is that the IPv6 prefix length now is
properly stored instead of being hardcoded to 64 even when set
via the -a option.

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

---
v2: Using inany_addr instead of protocol specific addresses as
    entry address field.
---
 arp.c    |  4 +--
 conf.c   | 78 +++++++++++++++++++++++++++++++++++---------------------
 dhcp.c   |  8 +++---
 dhcpv6.c |  6 ++---
 fwd.c    | 12 ++++-----
 inany.h  | 16 ++++++++++++
 ip.h     |  4 +++
 ndp.c    |  6 ++---
 passt.h  | 16 +++++++-----
 pasta.c  | 12 +++++----
 tap.c    |  4 +--
 11 files changed, 106 insertions(+), 60 deletions(-)

diff --git a/arp.c b/arp.c
index bb042e9..bc77a9f 100644
--- a/arp.c
+++ b/arp.c
@@ -54,7 +54,7 @@ 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)))
+	if (!memcmp(am->tip, inany_v4(&c->ip4.addrs[0].addr), sizeof(am->tip)))
 		return true;
 
 	return false;
@@ -145,7 +145,7 @@ 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(&c->ip4.addrs[0].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 7178a0e..9fc5dca 100644
--- a/conf.c
+++ b/conf.c
@@ -763,33 +763,33 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4)
 		}
 	}
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr)) {
+	if (!ip4->addr_count) {
+		struct in_addr addr;
+		int prefix_len = 0;
 		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;
 		}
+		ip4->addrs[0].addr = inany_from_v4(addr);
+		ip4->addrs[0].prefix_len = prefix_len;
+		ip4->addrs[0].flags = INANY_ADDR_HOST;
+		ip4->addr_count = 1;
 	}
 
-	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;
+	if (!ip4->addrs[0].prefix_len) {
+		const struct in_addr *a4 = inany_v4(&ip4->addrs[0].addr);
+
+		ip4->addrs[0].prefix_len = ip4_default_prefix_len(a4);
 	}
 
-	ip4->addr_seen = ip4->addr;
+	ip4->addr_seen = *inany_v4(&ip4->addrs[0].addr);
 
 	ip4->our_tap_addr = ip4->guest_gw;
 
-	if (IN4_IS_ADDR_UNSPECIFIED(&ip4->addr))
+	if (inany_is_unspecified(&ip4->addrs[0].addr))
 		return 0;
 
 	return ifi;
@@ -801,9 +801,11 @@ static unsigned int conf_ip4(unsigned int ifi, struct ip4_ctx *ip4)
  */
 static void conf_ip4_local(struct ip4_ctx *ip4)
 {
-	ip4->addr_seen = ip4->addr = IP4_LL_GUEST_ADDR;
+	ip4->addrs[0].addr = inany_from_v4(IP4_LL_GUEST_ADDR);
+	ip4->addr_seen = *inany_v4(&ip4->addrs[0].addr);
 	ip4->our_tap_addr = ip4->guest_gw = IP4_LL_GUEST_GW;
-	ip4->prefix_len = IP4_LL_PREFIX_LEN;
+	ip4->addrs[0].prefix_len = IP4_LL_PREFIX_LEN;
+	ip4->addr_count = 1;
 
 	ip4->no_copy_addrs = ip4->no_copy_routes = true;
 }
@@ -838,19 +840,25 @@ 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,
+			 ip6->addr_count ? NULL : &ip6->addrs[0].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;
+	if (!ip6->addr_count) {
+		ip6->addrs[0].prefix_len = prefix_len ? prefix_len : 64;
+		ip6->addrs[0].flags = INANY_ADDR_HOST;
+		ip6->addr_count = 1;
+	}
+
+	ip6->addr_seen = ip6->addrs[0].addr.a6;
 
 	if (IN6_IS_ADDR_LINKLOCAL(&ip6->guest_gw))
 		ip6->our_tap_ll = ip6->guest_gw;
 
-	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->addr) ||
+	if (IN6_IS_ADDR_UNSPECIFIED(&ip6->addrs[0].addr.a6) ||
 	    IN6_IS_ADDR_UNSPECIFIED(&ip6->our_tap_ll))
 		return 0;
 
@@ -1193,11 +1201,13 @@ static void conf_print(const struct ctx *c)
 		if (!c->no_dhcp) {
 			uint32_t mask;
 
-			mask = htonl(0xffffffff << (32 - c->ip4.prefix_len));
+			mask = htonl(0xffffffff <<
+				     (32 - c->ip4.addrs[0].prefix_len));
 
 			info("DHCP:");
 			info("    assign: %s",
-			     inet_ntop(AF_INET, &c->ip4.addr, buf4, sizeof(buf4)));
+			     inet_ntop(AF_INET, inany_v4(&c->ip4.addrs[0].addr),
+				       buf4, sizeof(buf4)));
 			info("    mask: %s",
 			     inet_ntop(AF_INET, &mask,        buf4, sizeof(buf4)));
 			info("    router: %s",
@@ -1235,7 +1245,8 @@ static void conf_print(const struct ctx *c)
 			goto dns6;
 
 		info("    assign: %s",
-		     inet_ntop(AF_INET6, &c->ip6.addr, buf6, sizeof(buf6)));
+		     inet_ntop(AF_INET6, &c->ip6.addrs[0].addr.a6,
+			       buf6, sizeof(buf6)));
 		info("    router: %s",
 		     inet_ntop(AF_INET6, &c->ip6.guest_gw, buf6, sizeof(buf6)));
 		info("    our link-local: %s",
@@ -1870,15 +1881,20 @@ void conf(struct ctx *c, int argc, char **argv)
 				die("Invalid address: %s", optarg);
 
 			if (af == AF_INET6) {
-				c->ip6.addr = addr.a6;
+				c->ip6.addrs[0].addr.a6 = addr.a6;
+				c->ip6.addrs[0].flags |= INANY_ADDR_CONFIGURED;
+				c->ip6.addr_count = 1;
 				if (c->mode == MODE_PASTA)
 					c->ip6.no_copy_addrs = true;
 				break;
 			}
 
 			a4 = inany_v4(&addr);
+
 			if (af == AF_INET && a4) {
-				c->ip4.addr = *a4;
+				c->ip4.addrs[0].addr = inany_from_v4(*a4);
+				c->ip4.addrs[0].flags |= INANY_ADDR_CONFIGURED;
+				c->ip4.addr_count = 1;
 				if (prefix_len) {
 					if (prefix_from_opt)
 						die("Can't mix CIDR with -n");
@@ -1886,21 +1902,25 @@ void conf(struct ctx *c, int argc, char **argv)
 				} else {
 					prefix_len = ip4_default_prefix_len(a4);
 				}
-				c->ip4.prefix_len = prefix_len;
+				c->ip4.addrs[0].prefix_len = prefix_len;
 				break;
 			}
 
 			die("Invalid address: %s", optarg);
 			break;
 		}
-		case 'n':
+		case 'n': {
+			int plen;
+
 			if (prefix_from_cidr)
 				die("Can't use both -n and CIDR prefix length");
-			c->ip4.prefix_len = conf_ip4_prefix(optarg);
-			if (c->ip4.prefix_len < 0)
+			plen = conf_ip4_prefix(optarg);
+			if (plen < 0)
 				die("Invalid netmask: %s", optarg);
+			c->ip4.addrs[0].prefix_len = plen;
 			prefix_from_opt = true;
 			break;
+		}
 		case 'M':
 			parse_mac(c->our_tap_mac, optarg);
 			break;
@@ -2185,7 +2205,7 @@ 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 (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addrs[0].addr.a6)) {
 		c->no_dhcpv6 = 1;
 	}
 
diff --git a/dhcp.c b/dhcp.c
index 6b9c2e3..d2afc3b 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -352,7 +352,7 @@ 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		= *inany_v4(&c->ip4.addrs[0].addr);
 	reply.siaddr		= 0;
 	reply.giaddr		= m->giaddr;
 	memcpy(&reply.chaddr,	m->chaddr,	sizeof(reply.chaddr));
@@ -404,7 +404,7 @@ 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 = htonl(0xffffffff << (32 - c->ip4.addrs[0].prefix_len));
 	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 +412,7 @@ 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 ((inany_v4(&c->ip4.addrs[0].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;
@@ -469,7 +469,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	if (m->flags & FLAG_BROADCAST)
 		dst = in4addr_broadcast;
 	else
-		dst = c->ip4.addr;
+		dst = *inany_v4(&c->ip4.addrs[0].addr);
 
 	tap_udp4_send(c, c->ip4.our_tap_addr, 67, dst, 68, &reply, dlen);
 
diff --git a/dhcpv6.c b/dhcpv6.c
index e4df0db..f45dece 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -625,7 +625,7 @@ 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 (dhcpv6_ia_notonlink(data, &c->ip6.addrs[0].addr.a6)) {
 
 			dhcpv6_send_ia_notonlink(c, data, &client_id_base,
 						 ntohs(client_id->l), mh->xid);
@@ -679,7 +679,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 
 	tap_udp6_send(c, src, 547, tap_ip6_daddr(c, src), 546,
 		      mh->xid, &resp, n);
-	c->ip6.addr_seen = c->ip6.addr;
+	c->ip6.addr_seen = c->ip6.addrs[0].addr.a6;
 
 	return 1;
 }
@@ -703,5 +703,5 @@ 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;
+	resp.ia_addr.addr	= c->ip6.addrs[0].addr.a6;
 }
diff --git a/fwd.c b/fwd.c
index 44a0e10..8d8151b 100644
--- a/fwd.c
+++ b/fwd.c
@@ -516,7 +516,7 @@ 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) ||
+	if (IN4_ARE_ADDR_EQUAL(addr, inany_v4(&c->ip4.addrs[0].addr)) ||
 	    IN4_ARE_ADDR_EQUAL(addr, &c->ip4.addr_seen))
 		return false;
 
@@ -537,7 +537,7 @@ static bool fwd_guest_accessible6(const struct ctx *c,
 	if (IN6_IS_ADDR_LOOPBACK(addr))
 		return false;
 
-	if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addr))
+	if (IN6_ARE_ADDR_EQUAL(addr, &c->ip6.addrs[0].addr.a6))
 		return false;
 
 	/* For IPv6, addr_seen starts unspecified, because we don't know what LL
@@ -587,9 +587,9 @@ static void nat_outbound(const struct ctx *c, const union inany_addr *addr,
 	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);
+		*translated = c->ip4.addrs[0].addr;
 	else if (inany_equals6(addr, &c->ip6.map_guest_addr))
-		translated->a6 = c->ip6.addr;
+		translated->a6 = c->ip6.addrs[0].addr.a6;
 	else
 		*translated = *addr;
 }
@@ -710,10 +710,10 @@ bool nat_inbound(const struct ctx *c, const union inany_addr *addr,
 		   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)) {
+		   inany_equals(addr, &c->ip4.addrs[0].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)) {
+		   inany_equals6(addr, &c->ip6.addrs[0].addr.a6)) {
 		translated->a6 = c->ip6.map_guest_addr;
 	} else if (fwd_guest_accessible(c, addr)) {
 		*translated = *addr;
diff --git a/inany.h b/inany.h
index 36865f9..07bfc3d 100644
--- a/inany.h
+++ b/inany.h
@@ -297,4 +297,20 @@ const char *inany_ntop(const union inany_addr *src, char *dst, socklen_t size);
 int inany_pton(const char *src, union inany_addr *dst);
 int inany_prefix_pton(const char *src, union inany_addr *dst, int *prefix_len);
 
+/* Flags for struct inany_addr_entry */
+#define INANY_ADDR_CONFIGURED	(1 << 0)	/* User set via -a */
+#define INANY_ADDR_HOST	(1 << 1)	/* From host interface */
+
+/**
+ * struct inany_addr_entry - Unified IPv4/IPv6 address entry
+ * @addr:		IPv4 (as mapped) or IPv6 address
+ * @prefix_len:	Prefix length (0-32 for IPv4, 0-128 for IPv6)
+ * @flags:		INANY_ADDR_* flags
+ */
+struct inany_addr_entry {
+	union inany_addr	addr;
+	uint16_t		prefix_len;
+	uint16_t		flags;
+};
+
 #endif /* INANY_H */
diff --git a/ip.h b/ip.h
index e5f5198..78bd43a 100644
--- a/ip.h
+++ b/ip.h
@@ -135,6 +135,10 @@ static const struct in_addr in4addr_broadcast = { 0xffffffff };
 #define IPV6_MIN_MTU		1280
 #endif
 
+/* Maximum number of addresses per address family */
+#define IP4_MAX_ADDRS		8
+#define IP6_MAX_ADDRS		16
+
 int ip4_default_prefix_len(const struct in_addr *addr);
 
 #endif /* IP_H */
diff --git a/ndp.c b/ndp.c
index eb9e313..5248fd6 100644
--- a/ndp.c
+++ b/ndp.c
@@ -257,7 +257,7 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
 			.valid_lifetime		= ~0U,
 			.pref_lifetime		= ~0U,
 		},
-		.prefix = c->ip6.addr,
+		.prefix = c->ip6.addrs[0].addr.a6,
 		.source_ll = {
 			.header = {
 				.type		= OPT_SRC_L2_ADDR,
@@ -466,8 +466,8 @@ void ndp_send_init_req(const struct ctx *c)
 			.icmp6_solicited	= 0, /* Reserved */
 			.icmp6_override		= 0, /* Reserved */
 		},
-		.target_addr = c->ip6.addr
+		.target_addr = c->ip6.addrs[0].addr.a6
 	};
 	debug("Sending initial NDP NS request for guest MAC address");
-	ndp_send(c, &c->ip6.addr, &ns, sizeof(ns));
+	ndp_send(c, &c->ip6.addrs[0].addr.a6, &ns, sizeof(ns));
 }
diff --git a/passt.h b/passt.h
index 79d01dd..9c0c3fe 100644
--- a/passt.h
+++ b/passt.h
@@ -66,9 +66,9 @@ enum passt_modes {
 
 /**
  * struct ip4_ctx - IPv4 execution context
- * @addr:		IPv4 address assigned to guest
+ * @addrs:		IPv4 addresses assigned to guest
+ * @addr_count:	Number of addresses in addrs[] array
  * @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
@@ -85,9 +85,10 @@ enum passt_modes {
  */
 struct ip4_ctx {
 	/* PIF_TAP addresses */
-	struct in_addr addr;
+	struct inany_addr_entry addrs[IP4_MAX_ADDRS];
+	int addr_count;
+
 	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;
@@ -107,7 +108,8 @@ struct ip4_ctx {
 
 /**
  * struct ip6_ctx - IPv6 execution context
- * @addr:		IPv6 address assigned to guest
+ * @addrs:		IPv6 addresses assigned to guest
+ * @addr_count:		Number of addresses in addrs[] array
  * @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
@@ -126,7 +128,9 @@ struct ip4_ctx {
  */
 struct ip6_ctx {
 	/* PIF_TAP addresses */
-	struct in6_addr addr;
+	struct inany_addr_entry addrs[IP6_MAX_ADDRS];
+	int addr_count;
+
 	struct in6_addr addr_seen;
 	struct in6_addr addr_ll_seen;
 	struct in6_addr guest_gw;
diff --git a/pasta.c b/pasta.c
index c307b8a..1bb3dd0 100644
--- a/pasta.c
+++ b/pasta.c
@@ -340,8 +340,8 @@ void pasta_ns_conf(struct ctx *c)
 			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);
+						 inany_v4(&c->ip4.addrs[0].addr),
+						 c->ip4.addrs[0].prefix_len);
 			} else {
 				rc = nl_addr_dup(nl_sock, c->ifi4,
 						 nl_sock_ns, c->pasta_ifi,
@@ -387,10 +387,12 @@ void pasta_ns_conf(struct ctx *c)
 					  0, IFF_NOARP);
 
 			if (c->ip6.no_copy_addrs) {
-				if (!IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr)) {
+				struct in6_addr *a = &c->ip6.addrs[0].addr.a6;
+
+				if (!IN6_IS_ADDR_UNSPECIFIED(a)) {
 					rc = nl_addr_set(nl_sock_ns,
-							 c->pasta_ifi, AF_INET6,
-							 &c->ip6.addr, 64);
+							 c->pasta_ifi,
+							 AF_INET6, a, 64);
 				}
 			} else {
 				rc = nl_addr_dup(nl_sock, c->ifi6,
diff --git a/tap.c b/tap.c
index 9d1344b..7c50013 100644
--- a/tap.c
+++ b/tap.c
@@ -951,8 +951,8 @@ resume:
 				c->ip6.addr_seen = *saddr;
 			}
 
-			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr))
-				c->ip6.addr = *saddr;
+			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addrs[0].addr.a6))
+				c->ip6.addrs[0].addr.a6 = *saddr;
 		} else if (!IN6_IS_ADDR_UNSPECIFIED(saddr)){
 			c->ip6.addr_seen = *saddr;
 		}
-- 
2.52.0