From 503f475ca5ee44e8a02fa82d077e422f64848f85 Mon Sep 17 00:00:00 2001
From: Mark Qvist <mark@unsigned.io>
Date: Sat, 11 Jan 2025 03:12:31 +0100
Subject: [PATCH] Read link MTU from link request packet

---
 RNS/Interfaces/LocalInterface.py |  2 +-
 RNS/Interfaces/TCPInterface.py   |  2 +-
 RNS/Link.py                      | 18 ++++++++++++++----
 3 files changed, 16 insertions(+), 6 deletions(-)

diff --git a/RNS/Interfaces/LocalInterface.py b/RNS/Interfaces/LocalInterface.py
index f007cc9f..9dff4c26 100644
--- a/RNS/Interfaces/LocalInterface.py
+++ b/RNS/Interfaces/LocalInterface.py
@@ -59,7 +59,7 @@ def __init__(self, owner, name, target_port = None, connected_socket=None):
         # TODO: Remove at some point
         # self.rxptime = 0
         
-        self.HW_MTU = 1064
+        self.HW_MTU = 32768
 
         self.online  = False
         
diff --git a/RNS/Interfaces/TCPInterface.py b/RNS/Interfaces/TCPInterface.py
index 563e38b6..bd601494 100644
--- a/RNS/Interfaces/TCPInterface.py
+++ b/RNS/Interfaces/TCPInterface.py
@@ -96,7 +96,7 @@ def __init__(self, owner, configuration, connected_socket=None):
         connect_timeout = c.as_int("connect_timeout") if "connect_timeout" in c else None
         max_reconnect_tries = c.as_int("max_reconnect_tries") if "max_reconnect_tries" in c else None
         
-        self.HW_MTU = 1064
+        self.HW_MTU = 32768
         
         self.IN               = True
         self.OUT              = False
diff --git a/RNS/Link.py b/RNS/Link.py
index c53fb959..f90adadc 100644
--- a/RNS/Link.py
+++ b/RNS/Link.py
@@ -68,8 +68,9 @@ class Link:
     Timeout for link establishment in seconds per hop to destination.
     """
 
-    TRAFFIC_TIMEOUT_MIN_MS = 5
-    TRAFFIC_TIMEOUT_FACTOR = 6
+    LINK_MTU_SIZE            = 3
+    TRAFFIC_TIMEOUT_MIN_MS   = 5
+    TRAFFIC_TIMEOUT_FACTOR   = 6
     KEEPALIVE_TIMEOUT_FACTOR = 4
     """
     RTT timeout factor used in link timeout calculation.
@@ -108,14 +109,22 @@ class Link:
 
     @staticmethod
     def validate_request(owner, data, packet):
-        if len(data) == (Link.ECPUBSIZE):
+        if len(data) == Link.ECPUBSIZE or len(data) == Link.ECPUBSIZE+Link.LINK_MTU_SIZE:
             try:
                 link = Link(owner = owner, peer_pub_bytes=data[:Link.ECPUBSIZE//2], peer_sig_pub_bytes=data[Link.ECPUBSIZE//2:Link.ECPUBSIZE])
                 link.set_link_id(packet)
+
+                if len(data) == Link.ECPUBSIZE+Link.LINK_MTU_SIZE:
+                    try:
+                        link.mtu = (ord(a[Link.ECPUBSIZE]) << 16) + (ord(a[Link.ECPUBSIZE+1]) << 8) + (ord(a[Link.ECPUBSIZE+2]))
+                    except Exception as e:
+                        link.mtu = Reticulum.MTU
+
                 link.destination = packet.destination
                 link.establishment_timeout = Link.ESTABLISHMENT_TIMEOUT_PER_HOP * max(1, packet.hops) + Link.KEEPALIVE
                 link.establishment_cost += len(packet.raw)
-                RNS.log("Validating link request "+RNS.prettyhexrep(link.link_id), RNS.LOG_VERBOSE)
+                RNS.log(f"Validating link request {RNS.prettyhexrep(link.link_id), RNS.LOG_VERBOSE}")
+                RNS.log(f"Link MTU configured to {RNS.prettysize(link.mtu)}", RNS.LOG_EXTREME)
                 RNS.log(f"Establishment timeout is {RNS.prettytime(link.establishment_timeout)} for incoming link request "+RNS.prettyhexrep(link.link_id), RNS.LOG_EXTREME)
                 link.handshake()
                 link.attached_interface = packet.receiving_interface
@@ -142,6 +151,7 @@ def __init__(self, destination=None, established_callback = None, closed_callbac
         if destination != None and destination.type != RNS.Destination.SINGLE:
             raise TypeError("Links can only be established to the \"single\" destination type")
         self.rtt = None
+        self.mtu = Reticulum.MTU
         self.establishment_cost = 0
         self.establishment_rate = None
         self.callbacks = LinkCallbacks()