From d258d56ceec7a54ecec7736c0bc0244f1555f77f Mon Sep 17 00:00:00 2001
From: sinanmohd <sinan@sinanmohd.com>
Date: Wed, 12 Jun 2024 15:33:37 +0530
Subject: kay/router: perform mss clamping on ppp0

---
 os/kay/modules/router.nix | 16 ++++++++++------
 1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/os/kay/modules/router.nix b/os/kay/modules/router.nix
index 2254c3b..45c9dff 100644
--- a/os/kay/modules/router.nix
+++ b/os/kay/modules/router.nix
@@ -1,15 +1,13 @@
-{ ... }:
+{ ... }: let
+  wanInterface = "ppp0";
 
-let
   lanInterface = "enp0s20u1";
-  wanInterface = "ppp0";
   subnet = "10.0.0.0";
   prefix = 24;
   host = "10.0.0.1";
   leaseRangeStart = "10.0.0.100";
   leaseRangeEnd = "10.0.0.254";
-in
-{
+in {
   imports = [
     ./wireguard.nix
     ./iperf3.nix
@@ -31,7 +29,13 @@ in
       allowedUDPPorts = [ 53 67 ];
       allowedTCPPorts = [ 53 ];
       extraCommands = ''
-        iptables -t nat -I POSTROUTING 1 -s ${subnet}/${toString prefix} -o ${wanInterface} -j MASQUERADE
+        iptables -t nat -I POSTROUTING 1 \
+            -s ${subnet}/${toString prefix} \
+            -o ${wanInterface} \
+            -j MASQUERADE
+        iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN \
+            -o ${wanInterface} \
+            -j TCPMSS --clamp-mss-to-pmtu
       '';
     };
   };
-- 
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