choose clamped mss correctly: minimum of original mss and mtu - 400.1.3

3 files changed, 6 insertions, 4 deletions

diff --git a/Cargo.lock b/Cargo.lock
index e27dea2..87c6a4b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -940,7 +940,7 @@ dependencies = [
 
 [[package]]
 name = "rsdsl_pppoe"
-version = "0.1.2"
+version = "0.1.3"
 dependencies = [
  "byteorder",
  "etherparse",
diff --git a/Cargo.toml b/Cargo.toml
index 341d8e4..fddb082 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "rsdsl_pppoe"
-version = "0.1.2"
+version = "0.1.3"
 authors = ["HimbeerserverDE <himbeerserverde@gmail.com>"]
 license = "MIT"
 edition = "2021"
diff --git a/src/main.rs b/src/main.rs
index 1be7d5f..d062d5d 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,6 +2,7 @@ use rsdsl_pppoe::client::Client;
 use rsdsl_pppoe::config::Config;
 use rsdsl_pppoe::error::{Error, Result};
 
+use std::cmp::min;
 use std::fs::File;
 use std::sync::mpsc;
 use std::sync::{Arc, Mutex};
@@ -15,6 +16,7 @@ use rsdsl_netlinkd::link;
 use tun_tap::{Iface, Mode};
 
 const IPPROTO_TCP: u8 = 0x06;
+const MAX_MSS: u16 = 1452;
 
 fn prepend<T>(v: Vec<T>, s: &[T]) -> Vec<T>
 where
@@ -40,8 +42,8 @@ fn clamp_mss_if_needed(buf: &mut [u8]) -> Result<()> {
             for opt in tcp_header.options_iterator() {
                 match opt {
                     Ok(mut opt) => {
-                        if let TcpOptionElement::MaximumSegmentSize(_) = opt {
-                            opt = TcpOptionElement::MaximumSegmentSize(1492);
+                        if let TcpOptionElement::MaximumSegmentSize(mss) = opt {
+                            opt = TcpOptionElement::MaximumSegmentSize(min(mss, MAX_MSS));
                         }
 
                         opts.push(opt);