From 9350a7520d28d1a38be1f4de0c869b08ceb892eb Mon Sep 17 00:00:00 2001
From: Alex Zenla <alex@edera.dev>
Date: Mon, 4 Mar 2024 07:59:37 +0000
Subject: [PATCH] network: performance tuning and IPv6 checksum fixups

---
 network/src/lib.rs          |  2 +-
 network/src/proxynat/tcp.rs |  4 ++--
 network/src/vbridge.rs      | 22 ++++++++++++++++------
 3 files changed, 19 insertions(+), 9 deletions(-)

diff --git a/network/src/lib.rs b/network/src/lib.rs
index 28ae784..68a82ac 100644
--- a/network/src/lib.rs
+++ b/network/src/lib.rs
@@ -22,7 +22,7 @@ pub mod proxynat;
 pub mod raw_socket;
 pub mod vbridge;
 
-pub const FORCE_MTU: usize = 20000;
+pub const FORCE_MTU: usize = 65521;
 
 pub struct NetworkService {
     pub backends: HashMap<Uuid, JoinHandle<()>>,
diff --git a/network/src/proxynat/tcp.rs b/network/src/proxynat/tcp.rs
index bcc97c4..c348bf3 100644
--- a/network/src/proxynat/tcp.rs
+++ b/network/src/proxynat/tcp.rs
@@ -194,7 +194,7 @@ impl ProxyTcpHandler {
                 }
 
                 ProxyTcpAcceptSelect::DoNothing => {
-                    sleeper = Some(tokio::time::sleep(Duration::from_millis(50)));
+                    sleeper = Some(tokio::time::sleep(Duration::from_micros(100)));
                 }
 
                 ProxyTcpAcceptSelect::Internal(data) => {
@@ -398,7 +398,7 @@ impl ProxyTcpHandler {
                 }
 
                 ProxyTcpDataSelect::DoNothing => {
-                    sleeper = Some(tokio::time::sleep(Duration::from_millis(50)));
+                    sleeper = Some(tokio::time::sleep(Duration::from_micros(100)));
                 }
 
                 ProxyTcpDataSelect::Close => {
diff --git a/network/src/vbridge.rs b/network/src/vbridge.rs
index bcd2afc..c0102c4 100644
--- a/network/src/vbridge.rs
+++ b/network/src/vbridge.rs
@@ -1,6 +1,6 @@
 use anyhow::{anyhow, Result};
 use bytes::BytesMut;
-use etherparse::{EtherType, Ethernet2Header, IpNumber, Ipv4Header, TcpHeader};
+use etherparse::{EtherType, Ethernet2Header, IpNumber, Ipv4Header, Ipv6Header, TcpHeader};
 use log::{debug, trace, warn};
 use smoltcp::wire::EthernetAddress;
 use std::{
@@ -148,13 +148,12 @@ impl VirtualBridge {
                         }
                     };
 
+                    // recalculate TCP checksums when routing packets.
+                    // the xen network backend / frontend drivers for linux
+                    // use checksum offloading but since we bypass some layers
+                    // of the kernel we have to do it ourselves.
                     if header.ether_type == EtherType::IPV4 {
                         let (ipv4, payload) = Ipv4Header::from_slice(payload)?;
-
-                        // recalculate TCP checksums when routing packets.
-                        // the xen network backend / frontend drivers for linux
-                        // are very stupid and do not calculate these properly
-                        // despite all best attempts at making it do so.
                         if ipv4.protocol == IpNumber::TCP {
                             let (mut tcp, payload) = TcpHeader::from_slice(payload)?;
                             tcp.checksum = tcp.calc_checksum_ipv4(&ipv4, payload)?;
@@ -164,6 +163,17 @@ impl VirtualBridge {
                                 packet[tcp_header_offset + i] = *b;
                             }
                         }
+                    } else if header.ether_type == EtherType::IPV6 {
+                        let (ipv6, payload) = Ipv6Header::from_slice(payload)?;
+                        if ipv6.next_header == IpNumber::TCP {
+                            let (mut tcp, payload) = TcpHeader::from_slice(payload)?;
+                            tcp.checksum = tcp.calc_checksum_ipv6(&ipv6, payload)?;
+                            let tcp_header_offset = Ethernet2Header::LEN + ipv6.header_len();
+                            let tcp_header_bytes = tcp.to_bytes();
+                            for (i, b) in tcp_header_bytes.iter().enumerate() {
+                                packet[tcp_header_offset + i] = *b;
+                            }
+                        }
                     }
 
                     let destination = EthernetAddress(header.destination);