dhcpv6-ia: fix invalid IPv6/hostname entries in statefile

Statefull IPv6 addresses are assigned to DHCPv6 clients from a
local prefix based on criteria which need to be fulfilled.
One of those criteria requires the IPv6 address still having
preferred lifetime which was not checked when constructing
the contents of the statefile.
Another criteria requires the prefix length not being smaller
than or equal to 64 when ra_management equals 0 or 1 which was
neither correctly checked when constructing the statefile.
This can lead to invalid hostname/IPv6 entries in the statefile
and thus possible connectivity issues when using DNS resolving.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

1 files changed, 26 insertions, 21 deletions

diff --git a/src/dhcpv6-ia.c b/src/dhcpv6-ia.c
index 17294f0..df69759 100644
--- a/src/dhcpv6-ia.c
+++ b/src/dhcpv6-ia.c
@@ -141,6 +141,25 @@ static void free_dhcpv6_assignment(struct dhcpv6_assignment *c)
 	free(c);
 }
 
+static inline bool valid_addr(const struct odhcpd_ipaddr *addr, time_t now)
+{
+	return (addr->prefix <= 96 && addr->preferred > (uint32_t)now);
+}
+
+static size_t elect_addr(const struct odhcpd_ipaddr *addrs, const size_t addrlen)
+{
+	size_t i, m;
+
+	for (i = 0, m = 0; i < addrlen; ++i) {
+		if (addrs[i].preferred > addrs[m].preferred ||
+			(addrs[i].preferred == addrs[m].preferred &&
+			 memcmp(&addrs[i].addr, &addrs[m].addr, 16) > 0))
+			m = i;
+	}
+
+	return m;
+}
+
 static int send_reconf(struct interface *iface, struct dhcpv6_assignment *assign)
 {
 	struct {
@@ -252,18 +271,12 @@ void dhcpv6_write_statefile(void)
 					struct in6_addr addr;
 					struct odhcpd_ipaddr *addrs = (c->managed) ? c->managed : iface->ia_addr;
 					size_t addrlen = (c->managed) ? (size_t)c->managed_size : iface->ia_addr_len;
-					size_t m = 0;
-
-					for (size_t i = 0; i < addrlen; ++i)
-						if (addrs[i].preferred > addrs[m].preferred ||
-								(addrs[i].preferred == addrs[m].preferred &&
-										memcmp(&addrs[i].addr, &addrs[m].addr, 16) > 0))
-							m = i;
+					size_t m = elect_addr(addrs, addrlen);
 
 					for (size_t i = 0; i < addrlen; ++i) {
-						if (addrs[i].prefix > 96 || (!INFINITE_VALID(c->valid_until) && c->valid_until <= now) ||
+						if (!valid_addr(&addrs[i], now) || (!INFINITE_VALID(c->valid_until) && c->valid_until <= now) ||
 								(iface->managed < RELAYD_MANAGED_NO_AFLAG && i != m &&
-										addrs[i].prefix == 64))
+										addrs[i].prefix <= 64))
 							continue;
 
 						addr = addrs[i].addr;
@@ -693,20 +706,13 @@ static size_t append_reply(uint8_t *buf, size_t buflen, uint16_t status,
 
 			struct odhcpd_ipaddr *addrs = (a->managed) ? a->managed : iface->ia_addr;
 			size_t addrlen = (a->managed) ? (size_t)a->managed_size : iface->ia_addr_len;
-			size_t m = 0;
-
-			for (size_t i = 0; i < addrlen; ++i)
-				if (addrs[i].preferred > addrs[m].preferred ||
-						(addrs[i].preferred == addrs[m].preferred &&
-								memcmp(&addrs[i].addr, &addrs[m].addr, 16) > 0))
-					m = i;
+			size_t m = elect_addr(addrs, addrlen);
 
 			for (size_t i = 0; i < addrlen; ++i) {
 				uint32_t prefix_pref = addrs[i].preferred;
 				uint32_t prefix_valid = addrs[i].valid;
 
-				if (addrs[i].prefix > 96 ||
-						addrs[i].preferred <= (uint32_t)now)
+				if (!valid_addr(&addrs[i], now))
 					continue;
 
 				if (prefix_pref != UINT32_MAX)
@@ -797,8 +803,7 @@ static size_t append_reply(uint8_t *buf, size_t buflen, uint16_t status,
 					size_t addrlen = (a->managed) ? (size_t)a->managed_size : iface->ia_addr_len;
 
 					for (size_t i = 0; i < addrlen; ++i) {
-						if (addrs[i].prefix > 96 ||
-								addrs[i].preferred <= (uint32_t)now)
+						if (!valid_addr(&addrs[i], now))
 							continue;
 
 						struct in6_addr addr = addrs[i].addr;
@@ -918,7 +923,7 @@ static void dhcpv6_log(uint8_t msgtype, struct interface *iface, time_t now,
 		char addrbuf[INET6_ADDRSTRLEN];
 
 		for (size_t i = 0; i < addrlen; ++i) {
-			if (addrs[i].prefix > 96 || addrs[i].preferred <= (uint32_t)now)
+			if (!valid_addr(&addrs[i], now))
 				continue;
 
 			struct in6_addr addr = addrs[i].addr;