ippool: Implement and use blacklist instead of blindly using IPPOOL_NOGATEWAYpespin/ippool

Commit dda21ed7d4a897c9284c69175d0da598598eae40 modified previous calls
to ippool_new() removing the pass of flags to avoid allocating certain
problematic IPs from the pool to MS, such as the network, gateway and
broadcast IPs.

Today I did some unsucessful tests with osmo-ggsn with a pool "ip prefix
dynamic 176.16.222.0/24", and thus IP 176.16.222.0 was being assigned to
the MS. De-capsulated DNS packets were received in the tun interface,
but the Linux system in there was unable to correctly forward the
packets to the gateway interface connected to the Internet. However,
adding a second MS which got 176.16.222.1 had its packets forwarded
correctly.

However, previous implementation relies on flag IPPOOL_NOGATEWAY flag to
blindly blacklist first IP after the network ip (ie, .0 and .1 are
removed), which limits the IP reserved for the tun device to be .1. If a
different IP in the range is assigned, it may cause issues. As a result,
a blacklist is introduced in this commit to dynamically fetch the tun IP
address and exlucde it from the pool of available IPs.

Change-Id: I8e91f7280d60490c858a769dd578c1c8e54e9243

1 files changed, 44 insertions, 4 deletions

diff --git a/lib/tun.c b/lib/tun.c
index 7662146..2ebb96d 100644
--- a/lib/tun.c
+++ b/lib/tun.c
@@ -751,8 +751,40 @@ int tun_runscript(struct tun_t *tun, char *script)
 
 #include <ifaddrs.h>
 
-/* obtain the link-local address of the tun device */
-int tun_ipv6_linklocal_get(const struct tun_t *tun, struct in6_addr *ia)
+/* Obtain the local address of the tun device */
+int tun_ipv4_local_get(const struct tun_t *tun, struct in46_prefix *prefix)
+{
+	struct ifaddrs *ifaddr, *ifa;
+
+	if (getifaddrs(&ifaddr) == -1) {
+		return -1;
+	}
+
+	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
+		struct sockaddr_in *sin4 = (struct sockaddr_in *) ifa->ifa_addr;
+		struct sockaddr_in *netmask4 = (struct sockaddr_in *) ifa->ifa_netmask;
+		if (ifa->ifa_addr == NULL)
+			continue;
+
+		if (ifa->ifa_addr->sa_family != AF_INET)
+			continue;
+
+		if (strcmp(ifa->ifa_name, tun->devname))
+			continue;
+
+		prefix->addr.len = sizeof(sin4->sin_addr);
+		prefix->addr.v4 = sin4->sin_addr;
+		prefix->prefixlen = netmask_ipv4_prefixlen(&netmask4->sin_addr);
+		freeifaddrs(ifaddr);
+		return 0;
+	}
+	freeifaddrs(ifaddr);
+	return -1;
+}
+
+/* Obtain the local address of the tun device.
+   Type of IPv6 address can be specified with "flags = IPV6_TYPE_LINK | IPV6_TYPE_GLOBAL" */
+int tun_ipv6_local_get(const struct tun_t *tun, struct in46_prefix *prefix, int flags)
 {
 	struct ifaddrs *ifaddr, *ifa;
 	static const uint8_t ll_prefix[] = { 0xfe,0x80, 0,0, 0,0, 0,0 };
@@ -763,6 +795,7 @@ int tun_ipv6_linklocal_get(const struct tun_t *tun, struct in6_addr *ia)
 
 	for (ifa = ifaddr; ifa != NULL; ifa = ifa->ifa_next) {
 		struct sockaddr_in6 *sin6 = (struct sockaddr_in6 *) ifa->ifa_addr;
+		struct sockaddr_in6 *netmask6 = (struct sockaddr_in6 *) ifa->ifa_netmask;
 		if (ifa->ifa_addr == NULL)
 			continue;
 
@@ -772,10 +805,17 @@ int tun_ipv6_linklocal_get(const struct tun_t *tun, struct in6_addr *ia)
 		if (strcmp(ifa->ifa_name, tun->devname))
 			continue;
 
-		if (memcmp(sin6->sin6_addr.s6_addr, ll_prefix, sizeof(ll_prefix)))
+		if (!(flags & IPV6_TYPE_LINK) &&
+		    !memcmp(sin6->sin6_addr.s6_addr, ll_prefix, sizeof(ll_prefix)))
+			continue;
+
+		if (!(flags & IPV6_TYPE_GLOBAL) &&
+		    memcmp(sin6->sin6_addr.s6_addr, ll_prefix, sizeof(ll_prefix)))
 			continue;
 
-		*ia = sin6->sin6_addr;
+		prefix->addr.len = sizeof(sin6->sin6_addr);
+		prefix->addr.v6 = sin6->sin6_addr;
+		prefix->prefixlen = netmask_ipv6_prefixlen(&netmask6->sin6_addr);
 		freeifaddrs(ifaddr);
 		return 0;
 	}