kernel-net: Let get_nexthop() return an optional interface name

The returned name should be the interface over which the destination
address/net is reachable.

src/libcharon/kernel/kernel_interface.c

@@ -524,13 +524,14 @@ METHOD(kernel_interface_t, get_source_addr, host_t*,
 }
 
 METHOD(kernel_interface_t, get_nexthop, host_t*,
-	private_kernel_interface_t *this, host_t *dest, int prefix, host_t *src)
+	private_kernel_interface_t *this, host_t *dest, int prefix, host_t *src,
+	char **iface)
 {
 	if (!this->net)
 	{
 		return NULL;
 	}
-	return this->net->get_nexthop(this->net, dest, prefix, src);
+	return this->net->get_nexthop(this->net, dest, prefix, src, iface);
 }
 
 METHOD(kernel_interface_t, get_interface, bool,

src/libcharon/kernel/kernel_interface.h

@@ -285,10 +285,12 @@ struct kernel_interface_t {
 	 * @param dest			target destination address
 	 * @param prefix		prefix length if dest is a subnet, -1 for auto
 	 * @param src			source address to check, or NULL
+	 * @param[out] iface	allocated name of the interface to reach dest, if
+	 *						available (optional)
 	 * @return				next hop address, NULL if unreachable
 	 */
 	host_t* (*get_nexthop)(kernel_interface_t *this, host_t *dest,
-						   int prefix, host_t *src);
+						   int prefix, host_t *src, char **iface);
 
 	/**
 	 * Get the interface name of a local address. Interfaces that are down or

src/libcharon/kernel/kernel_net.h

@@ -1,7 +1,7 @@
 /*
- * Copyright (C) 2008-2012 Tobias Brunner
+ * Copyright (C) 2008-2016 Tobias Brunner
  * Copyright (C) 2007 Martin Willi
- * Hochschule fuer Technik Rapperswil
+ * HSR Hochschule fuer Technik Rapperswil
  *
  * This program is free software; you can redistribute it and/or modify it
  * under the terms of the GNU General Public License as published by the
@@ -88,10 +88,12 @@ struct kernel_net_t {
 	 * @param dest			target destination address
 	 * @param prefix		prefix length if dest is a subnet, -1 for auto
 	 * @param src			source address to check, or NULL
+	 * @param[out] iface	allocated name of the interface to reach dest, if
+	 *						available (optional)
 	 * @return				next hop address, NULL if unreachable
 	 */
 	host_t* (*get_nexthop)(kernel_net_t *this, host_t *dest, int prefix,
-						   host_t *src);
+						   host_t *src, char **iface);
 
 	/**
 	 * Get the interface name of a local address. Interfaces that are down or

src/libcharon/plugins/kernel_iph/kernel_iph_net.c

@@ -562,7 +562,8 @@ METHOD(kernel_net_t, get_source_addr, host_t*,
 }
 
 METHOD(kernel_net_t, get_nexthop, host_t*,
-	private_kernel_iph_net_t *this, host_t *dest, int prefix, host_t *src)
+	private_kernel_iph_net_t *this, host_t *dest, int prefix, host_t *src,
+	char **iface)
 {
 	MIB_IPFORWARD_ROW2 route;
 	SOCKADDR_INET best, *sai_dst, *sai_src = NULL;
@@ -592,6 +593,10 @@ METHOD(kernel_net_t, get_nexthop, host_t*,
 	{
 		if (!nexthop->is_anyaddr(nexthop))
 		{
+			if (iface)
+			{
+				*iface = NULL;
+			}
 			return nexthop;
 		}
 		nexthop->destroy(nexthop);

src/libcharon/plugins/kernel_libipsec/kernel_libipsec_ipsec.c

@@ -308,7 +308,7 @@ static void add_exclude_route(private_kernel_libipsec_ipsec_t *this,
 	if (!route->exclude)
 	{
 		DBG2(DBG_KNL, "installing new exclude route for %H src %H", dst, src);
-		gtw = charon->kernel->get_nexthop(charon->kernel, dst, -1, NULL);
+		gtw = charon->kernel->get_nexthop(charon->kernel, dst, -1, NULL, NULL);
 		if (gtw)
 		{
 			char *if_name = NULL;
@@ -434,7 +434,8 @@ static bool install_route(private_kernel_libipsec_ipsec_t *this,
 	);
 #ifndef __linux__
 	/* on Linux we cant't install a gateway */
-	route->gateway = charon->kernel->get_nexthop(charon->kernel, dst, -1, src);
+	route->gateway = charon->kernel->get_nexthop(charon->kernel, dst, -1, src,
+												 NULL);
 #endif
 
 	if (policy->route)

src/libcharon/plugins/kernel_netlink/kernel_netlink_ipsec.c

@@ -2320,14 +2320,14 @@ static status_t add_policy_internal(private_kernel_netlink_ipsec_t *this,
 			if (!ipsec->src->is_anyaddr(ipsec->src))
 			{
 				route->gateway = charon->kernel->get_nexthop(charon->kernel,
-													ipsec->src, -1, ipsec->dst);
+											ipsec->src, -1, ipsec->dst, NULL);
 			}
 			else
 			{	/* for shunt policies */
 				iface = xfrm2host(policy->sel.family, &policy->sel.saddr, 0);
 				route->gateway = charon->kernel->get_nexthop(charon->kernel,
 												iface, policy->sel.prefixlen_s,
-												route->src_ip);
+												route->src_ip, NULL);
 				iface->destroy(iface);
 			}
 			route->dst_net = chunk_alloc(policy->sel.family == AF_INET ? 4 : 16);

src/libcharon/plugins/kernel_netlink/kernel_netlink_net.c

@@ -1659,7 +1659,7 @@ static rt_entry_t *parse_route(struct nlmsghdr *hdr, rt_entry_t *route)
  */
 static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
 						 int prefix, bool nexthop, host_t *candidate,
-						 u_int recursion)
+						 char **iface, u_int recursion)
 {
 	netlink_buf_t request;
 	struct nlmsghdr *hdr, *out, *current;
@@ -1861,7 +1861,7 @@ static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
 			if (gtw && !gtw->ip_equals(gtw, dest))
 			{
 				route->src_host = get_route(this, gtw, -1, FALSE, candidate,
-											recursion + 1);
+											iface, recursion + 1);
 			}
 			DESTROY_IF(gtw);
 			if (route->src_host)
@@ -1880,6 +1880,10 @@ static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
 
 	if (nexthop)
 	{	/* nexthop lookup, return gateway if any */
+		if (iface)
+		{
+			*iface = NULL;
+		}
 		if (best || routes->get_first(routes, (void**)&best) == SUCCESS)
 		{
 			addr = host_create_from_chunk(msg->rtm_family, best->gtw, 0);
@@ -1916,13 +1920,14 @@ static host_t *get_route(private_kernel_netlink_net_t *this, host_t *dest,
 METHOD(kernel_net_t, get_source_addr, host_t*,
 	private_kernel_netlink_net_t *this, host_t *dest, host_t *src)
 {
-	return get_route(this, dest, -1, FALSE, src, 0);
+	return get_route(this, dest, -1, FALSE, src, NULL, 0);
 }
 
 METHOD(kernel_net_t, get_nexthop, host_t*,
-	private_kernel_netlink_net_t *this, host_t *dest, int prefix, host_t *src)
+	private_kernel_netlink_net_t *this, host_t *dest, int prefix, host_t *src,
+	char **iface)
 {
-	return get_route(this, dest, prefix, TRUE, src, 0);
+	return get_route(this, dest, prefix, TRUE, src, iface, 0);
 }
 
 /**

src/libcharon/plugins/kernel_pfkey/kernel_pfkey_ipsec.c

@@ -2199,7 +2199,7 @@ static void add_exclude_route(private_kernel_pfkey_ipsec_t *this,
 	if (!route->exclude)
 	{
 		DBG2(DBG_KNL, "installing new exclude route for %H src %H", dst, src);
-		gtw = charon->kernel->get_nexthop(charon->kernel, dst, -1, NULL);
+		gtw = charon->kernel->get_nexthop(charon->kernel, dst, -1, NULL, NULL);
 		if (gtw)
 		{
 			char *if_name = NULL;
@@ -2315,7 +2315,7 @@ static bool install_route(private_kernel_pfkey_ipsec_t *this,
 	if (!dst->is_anyaddr(dst))
 	{
 		route->gateway = charon->kernel->get_nexthop(charon->kernel, dst, -1,
-													 src);
+													 src, NULL);
 
 		/* if the IP is virtual, we install the route over the interface it has
 		 * been installed on. Otherwise we use the interface we use for IKE, as
@@ -2329,7 +2329,7 @@ static bool install_route(private_kernel_pfkey_ipsec_t *this,
 	{	/* for shunt policies */
 		route->gateway = charon->kernel->get_nexthop(charon->kernel,
 											policy->src.net, policy->src.mask,
-											route->src_ip);
+											route->src_ip, NULL);
 
 		/* we don't have a source address, use the address we found */
 		src = route->src_ip;

src/libcharon/plugins/kernel_pfroute/kernel_pfroute_net.c

@@ -1684,8 +1684,13 @@ METHOD(kernel_net_t, get_source_addr, host_t*,
 }
 
 METHOD(kernel_net_t, get_nexthop, host_t*,
-	private_kernel_pfroute_net_t *this, host_t *dest, int prefix, host_t *src)
+	private_kernel_pfroute_net_t *this, host_t *dest, int prefix, host_t *src,
+	char **iface)
 {
+	if (iface)
+	{
+		*iface = NULL;
+	}
 	return get_route(this, TRUE, dest, src);
 }
 

src/libcharon/plugins/kernel_wfp/kernel_wfp_ipsec.c

@@ -1489,7 +1489,7 @@ static bool manage_route(private_kernel_wfp_ipsec_t *this,
 		dst->destroy(dst);
 		return FALSE;
 	}
-	gtw = charon->kernel->get_nexthop(charon->kernel, remote, -1, local);
+	gtw = charon->kernel->get_nexthop(charon->kernel, remote, -1, local, NULL);
 	if (add)
 	{
 		done = install_route(this, dst, mask, src, gtw);