Use source address in get_nexthop() call

Otherwise the nexthop returned might belong to a different route than
the one actually used with the current source address.

src/libhydra/plugins/kernel_klips/kernel_klips_ipsec.c

@@ -2174,7 +2174,7 @@ METHOD(kernel_ipsec_t, add_policy, status_t,
 
 		/* get the nexthop to dst */
 		route->gateway = hydra->kernel_interface->get_nexthop(
-												hydra->kernel_interface, dst);
+								hydra->kernel_interface, dst, route->src_ip);
 		route->dst_net = chunk_clone(policy->dst.net->get_address(policy->dst.net));
 		route->prefixlen = policy->dst.mask;
 

src/libhydra/plugins/kernel_netlink/kernel_netlink_ipsec.c

@@ -2167,7 +2167,8 @@ static status_t add_policy_internal(private_kernel_netlink_ipsec_t *this,
 		{
 			/* get the nexthop to src (src as we are in POLICY_FWD) */
 			route->gateway = hydra->kernel_interface->get_nexthop(
-										hydra->kernel_interface, ipsec->src);
+											hydra->kernel_interface, ipsec->src,
+											ipsec->dst);
 			/* install route via outgoing interface */
 			route->if_name = hydra->kernel_interface->get_interface(
 										hydra->kernel_interface, ipsec->dst);

src/libhydra/plugins/kernel_netlink/kernel_netlink_net.c

@@ -1443,9 +1443,9 @@ METHOD(kernel_net_t, get_source_addr, host_t*,
 }
 
 METHOD(kernel_net_t, get_nexthop, host_t*,
-	private_kernel_netlink_net_t *this, host_t *dest)
+	private_kernel_netlink_net_t *this, host_t *dest, host_t *src)
 {
-	return get_route(this, dest, TRUE, NULL);
+	return get_route(this, dest, TRUE, src);
 }
 
 /**

src/libhydra/plugins/kernel_pfkey/kernel_pfkey_ipsec.c

@@ -2026,7 +2026,8 @@ static status_t add_policy_internal(private_kernel_pfkey_ipsec_t *this,
 		{
 			/* get the nexthop to src (src as we are in POLICY_FWD).*/
 			route->gateway = hydra->kernel_interface->get_nexthop(
-										hydra->kernel_interface, ipsec->src);
+											hydra->kernel_interface, ipsec->src,
+											ipsec->dst);
 			/* install route via outgoing interface */
 			route->if_name = hydra->kernel_interface->get_interface(
 										hydra->kernel_interface, ipsec->dst);

src/libhydra/plugins/kernel_pfroute/kernel_pfroute_net.c

@@ -520,7 +520,7 @@ 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)
+	private_kernel_pfroute_net_t *this, host_t *dest, host_t *src)
 {
 	return NULL;
 }