From aad52572c3a53f08dbc76d26d6b23b9eead049b9 Mon Sep 17 00:00:00 2001
From: Kroese <kroese@users.noreply.github.com>
Date: Tue, 30 Apr 2024 00:32:18 +0200
Subject: [PATCH] feat: Improved networking (#51)

---
 src/network.sh | 28 ++++++++++++++++++----------
 src/reset.sh   |  2 +-
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/src/network.sh b/src/network.sh
index b909727..6f849b6 100644
--- a/src/network.sh
+++ b/src/network.sh
@@ -36,8 +36,8 @@ configureDHCP() {
   { ip link add link "$VM_NET_DEV" name "$VM_NET_TAP" address "$VM_NET_MAC" type macvtap mode bridge ; rc=$?; } || :
 
   if (( rc != 0 )); then
-    error "Cannot create macvtap interface. Please make sure the network type is 'macvlan' and not 'ipvlan',"
-    error "and that the NET_ADMIN capability has been added to the container: --cap-add NET_ADMIN" && exit 16
+    error "Cannot create macvtap interface. Please make sure that the network type is 'macvlan' and not 'ipvlan',"
+    error "that your kernel is recent (>4) and supports it, and that the container has the NET_ADMIN capability set." && exit 16
   fi
 
   while ! ip link set "$VM_NET_TAP" up; do
@@ -116,7 +116,7 @@ getPorts() {
     [ -z "$list" ] && list="$vnc" || list="$list,$vnc"
   fi
 
-  [ -z "$list" ] && return 0
+  [ -z "$list" ] && echo "" && return 0
 
   if [[ "$list" != *","* ]]; then
     echo " ! --dport $list"
@@ -143,12 +143,15 @@ configureNAT() {
 
   # Check port forwarding flag
   if [[ $(< /proc/sys/net/ipv4/ip_forward) -eq 0 ]]; then
-    { sysctl -w net.ipv4.ip_forward=1 ; rc=$?; } || :
-    if (( rc != 0 )); then
+    { sysctl -w net.ipv4.ip_forward=1 > /dev/null; rc=$?; } || :
+    if (( rc != 0 )) || [[ $(< /proc/sys/net/ipv4/ip_forward) -eq 0 ]]; then
       error "IP forwarding is disabled. $ADD_ERR --sysctl net.ipv4.ip_forward=1" && exit 24
     fi
   fi
 
+  local tables="The 'ip_tables' kernel module is not loaded. Try this command: sudo modprobe ip_tables iptable_nat"
+  local tuntap="The 'tun' kernel module is not available. Try this command: 'sudo modprobe tun' or run the container with 'privileged: true'."
+
   # Create a bridge with a static IP for the VM guest
 
   VM_NET_IP='20.20.20.21'
@@ -167,7 +170,9 @@ configureNAT() {
   done
 
   # QEMU Works with taps, set tap to the bridge created
-  ip tuntap add dev "$VM_NET_TAP" mode tap
+  if ! ip tuntap add dev "$VM_NET_TAP" mode tap; then
+    error "$tuntap" && exit 31
+  fi
 
   while ! ip link set "$VM_NET_TAP" up promisc on; do
     info "Waiting for TAP to become available..."
@@ -182,14 +187,17 @@ configureNAT() {
 
   exclude=$(getPorts "$HOST_PORTS")
 
-  iptables -t nat -A POSTROUTING -o "$VM_NET_DEV" -j MASQUERADE
+  if ! iptables -t nat -A POSTROUTING -o "$VM_NET_DEV" -j MASQUERADE; then
+    error "$tables" && exit 30
+  fi
+
   # shellcheck disable=SC2086
   iptables -t nat -A PREROUTING -i "$VM_NET_DEV" -d "$IP" -p tcp${exclude} -j DNAT --to "$VM_NET_IP"
   iptables -t nat -A PREROUTING -i "$VM_NET_DEV" -d "$IP" -p udp  -j DNAT --to "$VM_NET_IP"
 
   if (( KERNEL > 4 )); then
     # Hack for guest VMs complaining about "bad udp checksums in 5 packets"
-    iptables -A POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill || true
+    iptables -A POSTROUTING -t mangle -p udp --dport bootpc -j CHECKSUM --checksum-fill > /dev/null 2>&1 || true
   fi
 
   NET_OPTS="-netdev tap,ifname=$VM_NET_TAP,script=no,downscript=no,id=hostnet0"
@@ -297,8 +305,8 @@ fi
 
 if [[ "$DHCP" == [Yy1]* ]]; then
 
-  if [[ "$GATEWAY" == "172."* ]] && [[ "$DEBUG" != [Yy1]* ]]; then
-    error "You can only enable DHCP while the container is on a macvlan network!" && exit 26
+  if [[ "$GATEWAY" == "172."* ]]; then
+    warn "your gateway IP starts with 172.* which is often a sign that you are not on a macvlan network (required for DHCP)!"
   fi
 
   # Configuration for DHCP IP
diff --git a/src/reset.sh b/src/reset.sh
index 736f0f4..0f1842e 100644
--- a/src/reset.sh
+++ b/src/reset.sh
@@ -45,7 +45,7 @@ KERNEL=$(echo "$SYS" | cut -b 1)
 MINOR=$(echo "$SYS" | cut -d '.' -f2)
 ARCH=$(dpkg --print-architecture)
 RAM="$(free -g | grep Mem: | awk '{print $7}')/$(free -g | grep Mem: | awk '{print $2}') GB"
-CPU=$(lscpu | grep 'Model name' | cut -f 2 -d ":" | awk '{$1=$1}1' | sed 's# @.*##g' | sed s/"(R)"//g | sed 's/[^[:alnum:] ]\+/ /g' | sed 's/  */ /g')
+CPU=$(lscpu | grep -m 1 'Model name' | cut -f 2 -d ":" | awk '{$1=$1}1' | sed 's# @.*##g' | sed s/"(R)"//g | sed 's/[^[:alnum:] ]\+/ /g' | sed 's/  */ /g')
 
 # Check system