Add meshlink_get_pmtu() to get the path MTU to a specific node.

diff --git a/src/meshlink.c b/src/meshlink.c
index 4031075b079fe4b01f3e444241185109f58933f2..fcdaff62921275b4915a839648fcac975d0d03b7 100644 (file)
--- a/src/meshlink.c
+++ b/src/meshlink.c
@@ -944,6 +944,19 @@ void meshlink_send_from_queue(event_loop_t* el,meshlink_handle_t *mesh) {
        return ;
 }
 
+ssize_t meshlink_get_pmtu(meshlink_handle_t *mesh, meshlink_node_t *destination) {
+       if(!mesh || !destination)
+               return -1;
+
+       node_t *n = (node_t *)destination;
+       if(!n->status.reachable)
+               return 0;
+       else if(n->mtuprobes > 30 && n->minmtu)
+               return n->minmtu;
+       else
+               return MTU;
+}
+
 meshlink_node_t *meshlink_get_node(meshlink_handle_t *mesh, const char *name) {
        if(!mesh || !name)
                return NULL;

diff --git a/src/meshlink.h b/src/meshlink.h
index b938ca38ce72e78328de8846d6004e3023e4ac24..cca509c5feea04bca3f3c6eb19b8edfff3efdfcb 100644 (file)
--- a/src/meshlink.h
+++ b/src/meshlink.h
@@ -240,6 +240,20 @@ extern void meshlink_set_log_cb(meshlink_handle_t *mesh, meshlink_log_level_t le
  */
 extern bool meshlink_send(meshlink_handle_t *mesh, meshlink_node_t *destination, const void *data, size_t len);
 
+/// Query the maximum packet size that can be sent to a node.
+/** This functions returns the maximum size of packets (path MTU) that can be sent to a specific node with meshlink_send().
+ *  The path MTU is a property of the path packets will take to the destination node over the Internet.
+ *  It can be different for different destination nodes.
+ *  and the path MTU can change at any point in time due to changes in the Internet.
+ *  Therefore, although this should only occur rarely, it can still happen that packets that do not exceed this size get dropped.
+ *
+ *  @param mesh         A handle which represents an instance of MeshLink.
+ *  @param destination  A pointer to a meshlink_node_t describing the destination for the data.
+ *
+ *  @return             The recommended maximum size of packets that are to be sent to the destination node, 0 if the node is unreachable,
+ *                      or a negative value in case of an error.
+ */
+extern ssize_t meshlink_get_pmtu(meshlink_handle_t *mesh, meshlink_node_t *destination);
 
 /// Get a handle for a specific node.
 /** This function returns a handle for the node with the given name.