[PATCH v5 08/13] ip: Track observed guest IPv6 addresses in unified address array

[Jon Maloy <jmaloy@redhat.com>]

We remove the addr_seen and addr_ll_seen fields in struct ip6_ctx
and replace them by setting CONF_ADDR_OBSERVED and CONF_ADDR_LINKLOCAL
flags in the corresponding entry in the unified address array.

The observed IPv6 address is always added/moved to position 0
in the array, improving chances for fast lookup.

This completes the unification of address storage for both IPv4 and
IPv6, enabling future support for multiple guest addresses per family.

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

---
v5: - Made to use same algorithm and function as IPv4 for inserting
      observed into the array.
---
 conf.c    |  2 --
 dhcpv6.c  |  6 +-----
 dhcpv6.h  |  2 +-
 migrate.c | 27 +++++++++++++++++++-------
 passt.h   |  4 ----
 pasta.c   | 17 +++++++++++++----
 tap.c     | 57 +++++++++++++++++++++++++++++++++----------------------
 7 files changed, 69 insertions(+), 46 deletions(-)

diff --git a/conf.c b/conf.c
index faa60ec..f622424 100644
--- a/conf.c
+++ b/conf.c
@@ -816,8 +816,6 @@ static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
 		e->flags = CONF_ADDR_HOST;
 	}
 
-	ip6->addr_seen = e->addr.a6;
-
 	if (IN6_IS_ADDR_LINKLOCAL(&ip6->guest_gw))
 		ip6->our_tap_ll = ip6->guest_gw;
 
diff --git a/dhcpv6.c b/dhcpv6.c
index 55c17cf..ba200e5 100644
--- a/dhcpv6.c
+++ b/dhcpv6.c
@@ -549,7 +549,7 @@ static size_t dhcpv6_client_fqdn_fill(const struct iov_tail *data,
  * Return: 0 if it's not a DHCPv6 message, 1 if handled, -1 on failure
  */
 int dhcpv6(struct ctx *c, struct iov_tail *data,
-	   const struct in6_addr *saddr, const struct in6_addr *daddr)
+	   const struct in6_addr *daddr)
 {
 	const struct opt_server_id *server_id = NULL;
 	struct inany_addr_entry *e = first_v6(c);
@@ -591,8 +591,6 @@ int dhcpv6(struct ctx *c, struct iov_tail *data,
 	if (mlen + sizeof(*uh) != ntohs(uh->len) || mlen < sizeof(*mh))
 		return -1;
 
-	c->ip6.addr_ll_seen = *saddr;
-
 	src = &c->ip6.our_tap_ll;
 
 	mh = IOV_REMOVE_HEADER(data, mh_storage);
@@ -683,8 +681,6 @@ 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);
-	if (e)
-		c->ip6.addr_seen = e->addr.a6;
 
 	return 1;
 }
diff --git a/dhcpv6.h b/dhcpv6.h
index c706dfd..8cbc769 100644
--- a/dhcpv6.h
+++ b/dhcpv6.h
@@ -7,7 +7,7 @@
 #define DHCPV6_H
 
 int dhcpv6(struct ctx *c, struct iov_tail *data,
-	   struct in6_addr *saddr, struct in6_addr *daddr);
+	   struct in6_addr *daddr);
 void dhcpv6_init(const struct ctx *c);
 
 #endif /* DHCPV6_H */
diff --git a/migrate.c b/migrate.c
index f026e95..1e2830f 100644
--- a/migrate.c
+++ b/migrate.c
@@ -56,10 +56,7 @@ struct migrate_seen_addrs_v1 {
 static int seen_addrs_source_v1(struct ctx *c,
 				const struct migrate_stage *stage, int fd)
 {
-	struct migrate_seen_addrs_v1 addrs = {
-		.addr6 = c->ip6.addr_seen,
-		.addr6_ll = c->ip6.addr_ll_seen,
-	};
+	struct migrate_seen_addrs_v1 addrs = { 0 };
 	const struct inany_addr_entry *e;
 
 	(void)stage;
@@ -69,6 +66,15 @@ static int seen_addrs_source_v1(struct ctx *c,
 	if (e)
 		addrs.addr4 = *inany_v4(&e->addr);
 
+	/* IPv6 observed address */
+	e = fwd_get_addr(c, AF_INET6, CONF_ADDR_OBSERVED, 0);
+	if (e) {
+		if (e->flags & CONF_ADDR_LINKLOCAL)
+			addrs.addr6_ll = e->addr.a6;
+		else
+			addrs.addr6 = e->addr.a6;
+	}
+
 	memcpy(addrs.mac, c->guest_mac, sizeof(addrs.mac));
 
 	if (write_all_buf(fd, &addrs, sizeof(addrs)))
@@ -89,6 +95,7 @@ static int seen_addrs_target_v1(struct ctx *c,
 				const struct migrate_stage *stage, int fd)
 {
 	struct migrate_seen_addrs_v1 addrs;
+	struct in6_addr addr6, addr6_ll;
 	struct in_addr addr4;
 
 	(void)stage;
@@ -96,14 +103,20 @@ static int seen_addrs_target_v1(struct ctx *c,
 	if (read_all_buf(fd, &addrs, sizeof(addrs)))
 		return errno;
 
-	c->ip6.addr_seen = addrs.addr6;
-	c->ip6.addr_ll_seen = addrs.addr6_ll;
-
 	/* Copy from packed struct to avoid alignment issues */
 	addr4 = addrs.addr4;
+	addr6 = addrs.addr6;
+	addr6_ll = addrs.addr6_ll;
+
 	if (addr4.s_addr)
 		fwd_set_addr(c, &inany_from_v4(addr4), CONF_ADDR_OBSERVED, 0);
 
+	/* Prefer global over link-local if both present */
+	if (!IN6_IS_ADDR_UNSPECIFIED(&addr6))
+		fwd_set_addr(c, &inany_from_v6(addr6), CONF_ADDR_OBSERVED, 0);
+	else if (!IN6_IS_ADDR_UNSPECIFIED(&addr6_ll))
+		fwd_set_addr(c, &inany_from_v6(addr6_ll), CONF_ADDR_OBSERVED, 0);
+
 	memcpy(c->guest_mac, addrs.mac, sizeof(c->guest_mac));
 
 	return 0;
diff --git a/passt.h b/passt.h
index b808a19..e7489ca 100644
--- a/passt.h
+++ b/passt.h
@@ -112,8 +112,6 @@ struct ip4_ctx {
 
 /**
  * struct ip6_ctx - IPv6 execution context
- * @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
  * @map_host_loopback:	Outbound connections to this address are NATted to the
  *                      host's [::1]
@@ -129,8 +127,6 @@ struct ip4_ctx {
  * @no_copy_addrs:	Don't copy all addresses when configuring namespace
  */
 struct ip6_ctx {
-	struct in6_addr addr_seen;
-	struct in6_addr addr_ll_seen;
 	struct in6_addr guest_gw;
 	struct in6_addr map_host_loopback;
 	struct in6_addr map_guest_addr;
diff --git a/pasta.c b/pasta.c
index 7a081e7..56b2e0a 100644
--- a/pasta.c
+++ b/pasta.c
@@ -46,6 +46,8 @@
 
 #include "util.h"
 #include "passt.h"
+#include "conf.h"
+#include "fwd.h"
 #include "isolation.h"
 #include "netlink.h"
 #include "log.h"
@@ -384,12 +386,15 @@ void pasta_ns_conf(struct ctx *c)
 ipv4_done:
 
 		if (c->ifi6) {
-			rc = nl_addr_get_ll(nl_sock_ns, c->pasta_ifi,
-					    &c->ip6.addr_ll_seen);
-			if (rc < 0) {
+			struct in6_addr addr_ll;
+
+			rc = nl_addr_get_ll(nl_sock_ns, c->pasta_ifi, &addr_ll);
+			if (rc < 0)
 				warn("Can't get LL address from namespace: %s",
 				    strerror_(-rc));
-			}
+			else
+				fwd_set_addr(c, &inany_from_v6(addr_ll),
+					     CONF_ADDR_OBSERVED, 0);
 
 			rc = nl_addr_set_ll_nodad(nl_sock_ns, c->pasta_ifi);
 			if (rc < 0) {
@@ -403,6 +408,10 @@ ipv4_done:
 
 			if (c->ip6.no_copy_addrs) {
 				for_each_addr(e, c, AF_INET6) {
+					/* Skip, kernel auto-configures */
+					if (e->flags & CONF_ADDR_LINKLOCAL)
+						continue;
+
 					rc = nl_addr_set(nl_sock_ns,
 							 c->pasta_ifi,
 							 AF_INET6, &e->addr.a6,
diff --git a/tap.c b/tap.c
index 30e52f7..875c2bf 100644
--- a/tap.c
+++ b/tap.c
@@ -174,6 +174,17 @@ static void tap_check_src_addr4(struct ctx *c, const struct in_addr *addr)
 		fwd_set_addr(c, &inany_from_v4(*addr), CONF_ADDR_OBSERVED, 0);
 }
 
+/**
+ * tap_check_src_addr6() - Note an IPv6 address seen in guest traffic
+ * @c:		Execution context
+ * @addr:	IPv6 address seen as source from guest
+ */
+static void tap_check_src_addr6(struct ctx *c, const struct in6_addr *addr)
+{
+	if (!IN6_IS_ADDR_UNSPECIFIED(addr))
+		fwd_set_addr(c, &inany_from_v6(*addr), CONF_ADDR_OBSERVED, 0);
+}
+
 /**
  * tap_ip6_daddr() - Normal IPv6 destination address for inbound packets
  * @c:		Execution context
@@ -184,9 +195,25 @@ static void tap_check_src_addr4(struct ctx *c, const struct in_addr *addr)
 const struct in6_addr *tap_ip6_daddr(const struct ctx *c,
 				     const struct in6_addr *src)
 {
-	if (IN6_IS_ADDR_LINKLOCAL(src))
-		return &c->ip6.addr_ll_seen;
-	return &c->ip6.addr_seen;
+	const struct inany_addr_entry *e;
+
+	if (IN6_IS_ADDR_LINKLOCAL(src)) {
+		/* Link-local: first LL address (observed is at front) */
+		e = fwd_get_addr(c, AF_INET6, CONF_ADDR_LINKLOCAL, 0);
+	} else {
+		/* Global: observed non-LL first, then any non-LL */
+		e = fwd_get_addr(c, AF_INET6, CONF_ADDR_OBSERVED,
+				 CONF_ADDR_LINKLOCAL);
+		if (!e)
+			e = fwd_get_addr(c, AF_INET6, 0, CONF_ADDR_LINKLOCAL);
+	}
+
+	if (e)
+		return &e->addr.a6;
+
+	/* Last resort: first IPv6 address */
+	e = first_v6(c);
+	return e ? &e->addr.a6 : &in6addr_any;
 }
 
 /**
@@ -786,7 +813,7 @@ resume:
 
 		if (iph->saddr)
 			tap_check_src_addr4(c,
-					    (const struct in_addr *)&iph->saddr);
+					   (const struct in_addr *)&iph->saddr);
 
 		if (!iov_drop_header(&data, hlen))
 			continue;
@@ -958,24 +985,8 @@ resume:
 			continue;
 		}
 
-		if (IN6_IS_ADDR_LINKLOCAL(saddr)) {
-			c->ip6.addr_ll_seen = *saddr;
-
-			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.addr_seen)) {
-				c->ip6.addr_seen = *saddr;
-			}
-
-			if (!first_v6(c) && c->addr_count < INANY_MAX_ADDRS) {
-				struct inany_addr_entry *e;
-
-				e = &c->addrs[c->addr_count++];
-				e->addr.a6 = *saddr;
-				e->prefix_len = 64;
-				e->flags = CONF_ADDR_LINKLOCAL;
-			}
-		} else if (!IN6_IS_ADDR_UNSPECIFIED(saddr)){
-			c->ip6.addr_seen = *saddr;
-		}
+		if (!IN6_IS_ADDR_UNSPECIFIED(saddr))
+			tap_check_src_addr6(c, saddr);
 
 		if (proto == IPPROTO_ICMPV6) {
 			struct iov_tail ndp_data;
@@ -1006,7 +1017,7 @@ resume:
 		if (proto == IPPROTO_UDP) {
 			struct iov_tail uh_data = data;
 
-			if (dhcpv6(c, &uh_data, saddr, daddr))
+			if (dhcpv6(c, &uh_data, daddr))
 				continue;
 		}
 
-- 
2.52.0