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/kernel/kernel_interface.c

@@ -269,13 +269,13 @@ 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)
+	private_kernel_interface_t *this, host_t *dest, host_t *src)
 {
 	if (!this->net)
 	{
 		return NULL;
 	}
-	return this->net->get_nexthop(this->net, dest);
+	return this->net->get_nexthop(this->net, dest, src);
 }
 
 METHOD(kernel_interface_t, get_interface, char*,

src/libhydra/kernel/kernel_interface.h

@@ -282,7 +282,7 @@ struct kernel_interface_t {
 	 * Does a route lookup to get the source address used to reach dest.
 	 * The returned host is allocated and must be destroyed.
 	 * An optional src address can be used to check if a route is available
-	 * for given source to dest.
+	 * for the given source to dest.
 	 *
 	 * @param dest			target destination address
 	 * @param src			source address to check, or NULL
@@ -296,11 +296,13 @@ struct kernel_interface_t {
 	 *
 	 * Does a route lookup to get the next hop used to reach dest.
 	 * The returned host is allocated and must be destroyed.
+	 * An optional src address can be used to check if a route is available
+	 * for the given source to dest.
 	 *
 	 * @param dest			target destination address
 	 * @return				next hop address, NULL if unreachable
 	 */
-	host_t* (*get_nexthop)(kernel_interface_t *this, host_t *dest);
+	host_t* (*get_nexthop)(kernel_interface_t *this, host_t *dest, host_t *src);
 
 	/**
 	 * Get the interface name of a local address.

src/libhydra/kernel/kernel_net.h

@@ -42,7 +42,7 @@ struct kernel_net_t {
 	 * Does a route lookup to get the source address used to reach dest.
 	 * The returned host is allocated and must be destroyed.
 	 * An optional src address can be used to check if a route is available
-	 * for given source to dest.
+	 * for the given source to dest.
 	 *
 	 * @param dest			target destination address
 	 * @param src			source address to check, or NULL
@@ -55,11 +55,14 @@ struct kernel_net_t {
 	 *
 	 * Does a route lookup to get the next hop used to reach dest.
 	 * The returned host is allocated and must be destroyed.
+	 * An optional src address can be used to check if a route is available
+	 * for the given source to dest.
 	 *
 	 * @param dest			target destination address
+	 * @param src			source address to check, or NULL
 	 * @return				next hop address, NULL if unreachable
 	 */
-	host_t* (*get_nexthop)(kernel_net_t *this, host_t *dest);
+	host_t* (*get_nexthop)(kernel_net_t *this, host_t *dest, host_t *src);
 
 	/**
 	 * Get the interface name of a local address.