[PATCH v6 06/13] netlink, conf: Read all addresses from template interface at startup

[Jon Maloy <jmaloy@redhat.com>]

Add nl_addr_get_all() to read all addresses from the template interface
into c->addrs[] array, rather than just selecting the "best" one.

This allows multi-address configurations where the template interface
has multiple IPv4 or IPv6 addresses assigned to it, all of which
will now be copied to the guest namespace when using --config-net.

For IPv6, the function also captures the link-local address into
c->ip6.our_tap_ll as a side effect.

Update conf_ip4() and conf_ip6() to use nl_addr_get_all() when no
user-specified addresses are present.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
---
 conf.c    | 51 ++++++++++++++++++++++++++++-----------------------
 netlink.c | 53 +++++++++++++++++++++++++++++------------------------
 netlink.h |  3 +--
 3 files changed, 58 insertions(+), 49 deletions(-)

diff --git a/conf.c b/conf.c
index 95f09cb..70435d3 100644
--- a/conf.c
+++ b/conf.c
@@ -736,6 +736,7 @@ static int conf_ip4_prefix(const char *arg)
 static unsigned int conf_ip4(struct ctx *c, unsigned int ifi)
 {
 	struct ip4_ctx *ip4 = &c->ip4;
+	const struct guest_addr *a;
 
 	if (!ifi)
 		ifi = nl_get_ext_if(nl_sock, AF_INET);
@@ -755,24 +756,24 @@ static unsigned int conf_ip4(struct ctx *c, unsigned int ifi)
 		}
 	}
 
-	if (!fwd_get_addr(c, AF_INET, 0, 0)) {
-		struct in_addr addr;
-		int prefix_len;
-		int rc = nl_addr_get(nl_sock, ifi, AF_INET,
-				     &addr, &prefix_len, NULL);
+	a = fwd_get_addr(c, AF_INET, CONF_ADDR_USER, 0);
+	if (!a) {
+		int rc = nl_addr_get_all(c, nl_sock, ifi, AF_INET);
+
 		if (rc < 0) {
-			debug("Couldn't discover IPv4 address: %s",
+			debug("Couldn't discover IPv4 addresses: %s",
 			      strerror_(-rc));
 			return 0;
 		}
-		if (IN4_IS_ADDR_UNSPECIFIED(&addr))
+		if (!rc || !fwd_get_addr(c, AF_INET, 0, 0))
 			return 0;
 
-		fwd_set_addr(c, &inany_from_v4(addr), CONF_ADDR_HOST,
-			     prefix_len + 96);
-		ip4->addr_seen = addr;
+		a = fwd_get_addr(c, AF_INET, CONF_ADDR_HOST, 0);
 	}
 
+	if (a)
+		ip4->addr_seen = *inany_v4(&a->addr);
+
 	ip4->our_tap_addr = ip4->guest_gw;
 
 	return ifi;
@@ -803,10 +804,8 @@ static void conf_ip4_local(struct ctx *c)
  */
 static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
 {
-	const struct guest_addr *a = fwd_get_addr(c, AF_INET6, 0, 0);
 	struct ip6_ctx *ip6 = &c->ip6;
-	union inany_addr addr;
-	int prefix_len = 0;
+	const struct guest_addr *a;
 	int rc;
 
 	if (!ifi)
@@ -826,20 +825,26 @@ static unsigned int conf_ip6(struct ctx *c, unsigned int ifi)
 		}
 	}
 
-	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;
-	}
-
+	a = fwd_get_addr(c, AF_INET6, CONF_ADDR_USER, 0);
 	if (!a) {
-		fwd_set_addr(c, &addr, CONF_ADDR_HOST, prefix_len);
-		ip6->addr_seen = addr.a6;
+		rc = nl_addr_get_all(c, nl_sock, ifi, AF_INET6);
+		if (rc < 0) {
+			debug("Couldn't discover IPv6 addresses: %s",
+			      strerror_(-rc));
+			return 0;
+		}
+		a = fwd_get_addr(c, AF_INET6, CONF_ADDR_HOST, 0);
 	} else {
-		ip6->addr_seen = a->addr.a6;
+		rc = nl_addr_get_ll(nl_sock, ifi, &ip6->our_tap_ll);
+		if (rc < 0) {
+			debug("Couldn't get link-local address: %s",
+			      strerror_(-rc));
+		}
 	}
 
+	if (a)
+		ip6->addr_seen = a->addr.a6;
+
 	if (IN6_IS_ADDR_LINKLOCAL(&ip6->guest_gw))
 		ip6->our_tap_ll = ip6->guest_gw;
 
diff --git a/netlink.c b/netlink.c
index e07b47f..2727eec 100644
--- a/netlink.c
+++ b/netlink.c
@@ -747,20 +747,20 @@ int nl_addr_set_ll_nodad(int s, unsigned int ifi)
 }
 
 /**
- * nl_addr_get() - Get most specific global address, given interface and family
+ * nl_addr_get_all() - Get all addresses for a given interface into ctx
+ * @c:		Execution context
  * @s:		Netlink socket
- * @ifi:	Interface index in outer network namespace
- * @af:		Address family
- * @addr:	Global address to fill
- * @prefix_len:	Mask or prefix length, to fill
- * @addr_l:	Link-scoped address to fill (for IPv6)
+ * @ifi:	Interface index
+ * @af:		Address family (AF_INET or AF_INET6)
  *
- * Return: 0 on success, negative error code on failure
+ * Populates c->addrs[] with all non-deprecated addresses from the interface.
+ * For IPv6, also captures link-local address in c->ip6.our_tap_ll.
+ * Skips link-local addresses for the main array (kernel auto-configures them).
+ *
+ * Return: number of addresses added, or negative error code on failure
  */
-int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
-		void *addr, int *prefix_len, void *addr_l)
+int nl_addr_get_all(struct ctx *c, int s, unsigned int ifi, sa_family_t af)
 {
-	uint8_t prefix_max = 0, prefix_max_ll = 0;
 	struct req_t {
 		struct nlmsghdr nlh;
 		struct ifaddrmsg ifa;
@@ -771,6 +771,7 @@ int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
 	struct nlmsghdr *nh;
 	char buf[NLBUFSIZ];
 	ssize_t status;
+	int count = 0;
 	uint32_t seq;
 
 	seq = nl_send(s, &req, RTM_GETADDR, NLM_F_DUMP, sizeof(req));
@@ -784,27 +785,31 @@ int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
 
 		for (rta = IFA_RTA(ifa), na = IFA_PAYLOAD(nh); RTA_OK(rta, na);
 		     rta = RTA_NEXT(rta, na)) {
-			if ((af == AF_INET  && rta->rta_type != IFA_LOCAL) ||
-			    (af == AF_INET6 && rta->rta_type != IFA_ADDRESS))
-				continue;
+			union inany_addr addr;
+			int prefix_len;
 
-			if (ifa->ifa_prefixlen > prefix_max && addr &&
-			    (af == AF_INET || ifa->ifa_scope < RT_SCOPE_LINK)) {
-				memcpy(addr, RTA_DATA(rta), RTA_PAYLOAD(rta));
+			if (af == AF_INET && rta->rta_type != IFA_LOCAL)
+				continue;
+			if (af == AF_INET6 && rta->rta_type != IFA_ADDRESS)
+				continue;
 
-				prefix_max = *prefix_len = ifa->ifa_prefixlen;
+			if (af == AF_INET6 &&
+			    ifa->ifa_scope == RT_SCOPE_LINK) {
+				memcpy(&c->ip6.our_tap_ll, RTA_DATA(rta),
+				       sizeof(c->ip6.our_tap_ll));
+				continue;
 			}
 
-			if (addr_l &&
-			    af == AF_INET6 && ifa->ifa_scope == RT_SCOPE_LINK &&
-			    ifa->ifa_prefixlen > prefix_max_ll) {
-				memcpy(addr_l, RTA_DATA(rta), RTA_PAYLOAD(rta));
+			inany_from_af(&addr, af, RTA_DATA(rta));
+			prefix_len = ifa->ifa_prefixlen +
+				     (af == AF_INET ? 96 : 0);
 
-				prefix_max_ll = ifa->ifa_prefixlen;
-			}
+			fwd_set_addr(c, &addr, CONF_ADDR_HOST, prefix_len);
+			count++;
 		}
 	}
-	return status;
+
+	return status < 0 ? status : count;
 }
 
 /**
diff --git a/netlink.h b/netlink.h
index b22f485..3af6d58 100644
--- a/netlink.h
+++ b/netlink.h
@@ -19,8 +19,7 @@ int nl_route_get_def(int s, unsigned int ifi, sa_family_t af, void *gw);
 int nl_route_set_def(int s, unsigned int ifi, sa_family_t af, const void *gw);
 int nl_route_dup(int s_src, unsigned int ifi_src,
 		 int s_dst, unsigned int ifi_dst, sa_family_t af);
-int nl_addr_get(int s, unsigned int ifi, sa_family_t af,
-		void *addr, int *prefix_len, void *addr_l);
+int nl_addr_get_all(struct ctx *c, int s, unsigned int ifi, sa_family_t af);
 bool nl_neigh_mac_get(int s, const union inany_addr *addr, int ifi,
 		      unsigned char *mac);
 int nl_addr_set(int s, unsigned int ifi, sa_family_t af,
-- 
2.52.0