[PATCH v3 11/11] conf: Select addresses for DHCP and NDP distribution

[Jon Maloy <jmaloy@redhat.com>]

As a part of the multiple address support feature, we add a new
algorithm for DHCP/DHCPv6/NDP address selection and refactor the
conf_print() function accordingly.

The fwd_first_usable_addr() and fwd_select_addr() functions now take
a context pointer and address family parameter to work with the
unified address array using for_each_addr().

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 conf.c   | 60 +++++++++++++++++++++++++----------------
 dhcp.c   | 17 +++++++++---
 dhcp.h   |  2 +-
 dhcpv6.c | 17 ++++++++++--
 fwd.c    | 82 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 fwd.h    |  6 +++++
 ndp.c    | 15 ++++++++---
 ndp.h    |  4 +--
 passt.h  |  3 +++
 9 files changed, 171 insertions(+), 35 deletions(-)

diff --git a/conf.c b/conf.c
index 6892cea..4c53d33 100644
--- a/conf.c
+++ b/conf.c
@@ -46,6 +46,7 @@
 #include "lineread.h"
 #include "isolation.h"
 #include "log.h"
+#include "fwd.h"
 #include "vhost_user.h"
 
 #define NETNS_RUN_DIR	"/run/netns"
@@ -1099,10 +1100,12 @@ enum passt_modes conf_mode(int argc, char *argv[])
 static void conf_print(const struct ctx *c)
 {
 	char buf4[INET_ADDRSTRLEN], buf6[INET6_ADDRSTRLEN];
-	char bufmac[ETH_ADDRSTRLEN], ifn[IFNAMSIZ];
+	char bufmac[ETH_ADDRSTRLEN];
 	int i;
 
 	if (c->ifi4 > 0 || c->ifi6 > 0) {
+		char ifn[IFNAMSIZ];
+
 		info("Template interface: %s%s%s%s%s",
 		     c->ifi4 > 0 ? if_indextoname(c->ifi4, ifn) : "",
 		     c->ifi4 > 0 ? " (IPv4)" : "",
@@ -1144,20 +1147,22 @@ static void conf_print(const struct ctx *c)
 				       buf4, sizeof(buf4)));
 
 		if (!c->no_dhcp) {
-			struct inany_addr_entry *e = first_v4(c);
-			uint32_t mask;
-
-			mask = IN4_MASK(e->prefix_len);
-
-			info("DHCP:");
-			info("    assign: %s",
-			     inet_ntop(AF_INET, inany_v4(&e->addr),
-				       buf4, sizeof(buf4)));
-			info("    mask: %s",
-			     inet_ntop(AF_INET, &mask,        buf4, sizeof(buf4)));
-			info("    router: %s",
-			     inet_ntop(AF_INET, &c->ip4.guest_gw,
-				       buf4, sizeof(buf4)));
+			const struct inany_addr_entry *e;
+
+			e = fwd_first_usable_addr(c, AF_INET,
+						  INANY_ADDR_OBSERVED);
+			if (e) {
+				uint32_t mask = IN4_MASK(e->prefix_len);
+
+				info("DHCP:");
+				info("    assign: %s",
+				     inany_ntop(&e->addr, buf4, sizeof(buf4)));
+				info("    mask: %s",
+				     inet_ntop(AF_INET, &mask, buf4, sizeof(buf4)));
+				info("    router: %s",
+				     inet_ntop(AF_INET, &c->ip4.guest_gw,
+					       buf4, sizeof(buf4)));
+			}
 		}
 
 		for (i = 0; !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i]); i++) {
@@ -1189,14 +1194,23 @@ static void conf_print(const struct ctx *c)
 		else
 			goto dns6;
 
-		info("    assign: %s",
-		     inet_ntop(AF_INET6, &first_v6(c)->addr.a6,
-			       buf6, sizeof(buf6)));
-		info("    router: %s",
-		     inet_ntop(AF_INET6, &c->ip6.guest_gw, buf6, sizeof(buf6)));
-		info("    our link-local: %s",
-		     inet_ntop(AF_INET6, &c->ip6.our_tap_ll,
-			       buf6, sizeof(buf6)));
+	{
+			const struct inany_addr_entry *e;
+
+			e = fwd_first_usable_addr(c, AF_INET6,
+						  INANY_ADDR_OBSERVED |
+						  INANY_ADDR_LINKLOCAL);
+			if (e) {
+				info("    assign: %s",
+				     inany_ntop(&e->addr, buf6, sizeof(buf6)));
+				info("    router: %s",
+				     inet_ntop(AF_INET6, &c->ip6.guest_gw,
+					       buf6, sizeof(buf6)));
+				info("    our link-local: %s",
+				     inet_ntop(AF_INET6, &c->ip6.our_tap_ll,
+					       buf6, sizeof(buf6)));
+			}
+		}
 
 dns6:
 		for (i = 0; !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns[i]); i++) {
diff --git a/dhcp.c b/dhcp.c
index 933a8cf..31ea4f1 100644
--- a/dhcp.c
+++ b/dhcp.c
@@ -31,6 +31,7 @@
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
+#include "fwd.h"
 #include "dhcp.h"
 
 /**
@@ -300,8 +301,9 @@ static void opt_set_dns_search(const struct ctx *c, size_t max_len)
  *
  * Return: 0 if it's not a DHCP message, 1 if handled, -1 on failure
  */
-int dhcp(const struct ctx *c, struct iov_tail *data)
+int dhcp(struct ctx *c, struct iov_tail *data)
 {
+	union inany_addr yiaddr = { 0 };
 	char macstr[ETH_ADDRSTRLEN];
 	size_t mlen, dlen, opt_len;
 	struct in_addr mask, dst;
@@ -314,7 +316,7 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	struct msg m_storage;
 	struct msg const *m;
 	struct msg reply;
-	unsigned int i;
+	int i;
 
 	eh = IOV_REMOVE_HEADER(data, eh_storage);
 	iph = IOV_PEEK_HEADER(data, iph_storage);
@@ -344,6 +346,15 @@ int dhcp(const struct ctx *c, struct iov_tail *data)
 	    m->op != BOOTREQUEST)
 		return -1;
 
+	/* Select address to offer */
+	{
+		const struct inany_addr_entry *e;
+
+		e = fwd_select_addr(c, AF_INET, INANY_ADDR_DHCP,
+				    INANY_ADDR_OBSERVED);
+		if (e)
+			yiaddr = e->addr;
+	}
 	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		= *inany_v4(&first_v4(c)->addr);
+	reply.yiaddr		= *inany_v4(&yiaddr);
 	reply.siaddr		= 0;
 	reply.giaddr		= m->giaddr;
 	memcpy(&reply.chaddr,	m->chaddr,	sizeof(reply.chaddr));
diff --git a/dhcp.h b/dhcp.h
index cd50c99..7326c7d 100644
--- a/dhcp.h
+++ b/dhcp.h
@@ -6,7 +6,7 @@
 #ifndef DHCP_H
 #define DHCP_H
 
-int dhcp(const struct ctx *c, struct iov_tail *data);
+int dhcp(struct ctx *c, struct iov_tail *data);
 void dhcp_init(void);
 
 #endif /* DHCP_H */
diff --git a/dhcpv6.c b/dhcpv6.c
index 67307d9..32494e9 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -31,6 +31,7 @@
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
+#include "fwd.h"
 
 /**
  * struct opt_hdr - DHCPv6 option header
@@ -564,6 +565,7 @@ 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;
+	struct in6_addr *ia_addr = NULL;
 	const struct in6_addr *src;
 	struct msg_hdr mh_storage;
 	const struct msg_hdr *mh;
@@ -612,6 +614,17 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 	if (ia && ntohs(ia->hdr.l) < MIN(OPT_VSIZE(ia_na), OPT_VSIZE(ia_ta)))
 		return -1;
 
+	/* Select address to assign */
+	{
+		struct inany_addr_entry *e;
+
+		e = fwd_select_addr(c, AF_INET6, INANY_ADDR_DHCP6,
+				    INANY_ADDR_OBSERVED | INANY_ADDR_LINKLOCAL);
+		if (e) {
+			ia_addr = &e->addr.a6;
+			resp.ia_addr.addr = *ia_addr;
+		}
+	}
 	resp.hdr.type = TYPE_REPLY;
 	switch (mh->type) {
 	case TYPE_REQUEST:
@@ -624,7 +637,7 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 		if (mh->type == TYPE_CONFIRM && server_id)
 			return -1;
 
-		if (dhcpv6_ia_notonlink(data, &first_v6(c)->addr.a6)) {
+		if (dhcpv6_ia_notonlink(data, ia_addr)) {
 
 			dhcpv6_send_ia_notonlink(c, data, &client_id_base,
 						 ntohs(client_id->l), mh->xid);
@@ -701,5 +714,5 @@ 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	= first_v6(c)->addr.a6;
+	/* Address is set dynamically in dhcpv6() */
 }
diff --git a/fwd.c b/fwd.c
index fc26eba..e41ae9b 100644
--- a/fwd.c
+++ b/fwd.c
@@ -491,6 +491,88 @@ static bool is_dns_flow(uint8_t proto, const struct flowside *ini)
 		((ini->oport == 53) || (ini->oport == 853));
 }
 
+/**
+ * fwd_first_usable_addr() - Find first assignable address (read-only)
+ * @c:		Execution context
+ * @af:		Address family (AF_INET or AF_INET6)
+ * @skip:	Flags to skip (e.g., INANY_ADDR_LINKLOCAL | INANY_ADDR_OBSERVED)
+ *
+ * Prefers CONFIGURED over HOST addresses.
+ *
+ * Return: pointer to first usable address, or NULL
+ */
+const struct inany_addr_entry *
+fwd_first_usable_addr(const struct ctx *c, int af, int skip)
+{
+	const struct inany_addr_entry *e;
+
+	for_each_addr(c, e, af) {
+		if (e->flags & skip)
+			continue;
+		if (e->flags & INANY_ADDR_CONFIGURED)
+			return e;
+	}
+
+	for_each_addr(c, e, af) {
+		if (e->flags & skip)
+			continue;
+		if (e->flags & INANY_ADDR_HOST)
+			return e;
+	}
+
+	return NULL;
+}
+
+/**
+ * fwd_select_addr() - Select address for protocol assignment (DHCP/NDP/DHCPv6)
+ * @c:		Execution context
+ * @af:		Address family (AF_INET or AF_INET6)
+ * @assign_flag: Flag to set on selected address (INANY_ADDR_DHCP, etc.)
+ * @skip:	Flags to skip (e.g., INANY_ADDR_LINKLOCAL | INANY_ADDR_OBSERVED)
+ *
+ * Selection priority:
+ *   1. Address already having @assign_flag set
+ *   2. Address with INANY_ADDR_CONFIGURED (user -a option)
+ *   3. Address with INANY_ADDR_HOST (from template interface)
+ *
+ * Return: pointer to selected address entry, or NULL if none found
+ */
+struct inany_addr_entry *fwd_select_addr(struct ctx *c, int af,
+					 int assign_flag, int skip)
+{
+	struct inany_addr_entry *e;
+
+	/* First: find address already having assign_flag */
+	for_each_addr(c, e, af) {
+		if (e->flags & skip)
+			continue;
+		if (e->flags & assign_flag)
+			return e;
+	}
+
+	/* Second: find CONFIGURED address, set assign_flag */
+	for_each_addr(c, e, af) {
+		if (e->flags & skip)
+			continue;
+		if (e->flags & INANY_ADDR_CONFIGURED) {
+			e->flags |= assign_flag;
+			return e;
+		}
+	}
+
+	/* Third: find HOST address, set assign_flag */
+	for_each_addr(c, e, af) {
+		if (e->flags & skip)
+			continue;
+		if (e->flags & INANY_ADDR_HOST) {
+			e->flags |= assign_flag;
+			return e;
+		}
+	}
+
+	return NULL;
+}
+
 /**
  * fwd_guest_addr4() - Get first observed IPv4 guest address
  * @c:		Execution context
diff --git a/fwd.h b/fwd.h
index 7792582..91b15dc 100644
--- a/fwd.h
+++ b/fwd.h
@@ -9,6 +9,7 @@
 
 union inany_addr;
 struct flowside;
+struct inany_addr_entry;
 
 /* Number of ports for both TCP and UDP */
 #define	NUM_PORTS	(1U << 16)
@@ -63,4 +64,9 @@ 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);
 
+const struct inany_addr_entry *fwd_first_usable_addr(const struct ctx *c,
+						     int af, int skip);
+struct inany_addr_entry *fwd_select_addr(struct ctx *c, int af,
+					 int assign_flag, int skip);
+
 #endif /* FWD_H */
diff --git a/ndp.c b/ndp.c
index f60c298..2211f86 100644
--- a/ndp.c
+++ b/ndp.c
@@ -32,6 +32,7 @@
 #include "passt.h"
 #include "tap.h"
 #include "log.h"
+#include "fwd.h"
 
 #define	RT_LIFETIME	65535
 
@@ -236,7 +237,7 @@ void ndp_unsolicited_na(const struct ctx *c, const struct in6_addr *addr)
  * @c:		Execution context
  * @dst:	IPv6 address to send the RA to
  */
-static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
+static void ndp_ra(struct ctx *c, const struct in6_addr *dst)
 {
 	struct ndp_ra ra = {
 		.ih = {
@@ -257,7 +258,7 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
 			.valid_lifetime		= ~0U,
 			.pref_lifetime		= ~0U,
 		},
-		.prefix = first_v6(c)->addr.a6,
+		.prefix = IN6ADDR_ANY_INIT,
 		.source_ll = {
 			.header = {
 				.type		= OPT_SRC_L2_ADDR,
@@ -265,8 +266,14 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
 			},
 		},
 	};
+	struct inany_addr_entry *e;
 	unsigned char *ptr = NULL;
 
+	/* Select address/prefix to advertise */
+	e = fwd_select_addr(c, AF_INET6, INANY_ADDR_NDP, INANY_ADDR_LINKLOCAL);
+	if (e)
+		ra.prefix = e->addr.a6;
+
 	ptr = &ra.var[0];
 
 	if (c->mtu) {
@@ -353,7 +360,7 @@ static void ndp_ra(const struct ctx *c, const struct in6_addr *dst)
  *
  * Return: 0 if not handled here, 1 if handled, -1 on failure
  */
-int ndp(const struct ctx *c, const struct in6_addr *saddr,
+int ndp(struct ctx *c, const struct in6_addr *saddr,
 	struct iov_tail *data)
 {
 	struct icmp6hdr ih_storage;
@@ -407,7 +414,7 @@ static time_t next_ra;
  * @c:		Execution context
  * @now:	Current (monotonic) time
  */
-void ndp_timer(const struct ctx *c, const struct timespec *now)
+void ndp_timer(struct ctx *c, const struct timespec *now)
 {
 	time_t max_rtr_adv_interval = DEFAULT_MAX_RTR_ADV_INTERVAL;
 	time_t min_rtr_adv_interval, interval;
diff --git a/ndp.h b/ndp.h
index 56b756d..726aef6 100644
--- a/ndp.h
+++ b/ndp.h
@@ -8,9 +8,9 @@
 
 struct icmp6hdr;
 
-int ndp(const struct ctx *c, const struct in6_addr *saddr,
+int ndp(struct ctx *c, const struct in6_addr *saddr,
 	struct iov_tail *data);
-void ndp_timer(const struct ctx *c, const struct timespec *now);
+void ndp_timer(struct ctx *c, const struct timespec *now);
 void ndp_send_init_req(const struct ctx *c);
 void ndp_unsolicited_na(const struct ctx *c, const struct in6_addr *addr);
 
diff --git a/passt.h b/passt.h
index 7040781..f5f8c68 100644
--- a/passt.h
+++ b/passt.h
@@ -71,6 +71,9 @@ enum passt_modes {
 #define INANY_ADDR_HOST		BIT(1)		/* From host interface */
 #define INANY_ADDR_OBSERVED	BIT(2)		/* Seen in guest traffic */
 #define INANY_ADDR_LINKLOCAL	BIT(3)		/* Link-local address */
+#define INANY_ADDR_DHCP		BIT(4)		/* IPv4: assigned via DHCP */
+#define INANY_ADDR_DHCP6	BIT(5)		/* IPv6: assigned via DHCPv6 */
+#define INANY_ADDR_NDP		BIT(6)		/* IPv6: prefix via NDP/RA */
 
 /**
  * for_each_addr() - Iterate over addresses in unified array
-- 
2.52.0