Add per-VM NAT and DNS config

run.sh

@@ -42,6 +42,7 @@ MAX_VCPU=16
 MIN_RAM=256
 MAX_RAM=32768
 MAX_DISK_BYTES=$((128 * 1024 * 1024 * 1024))
+DNS_SERVERS="${DNS_SERVERS:-1.1.1.1}"
 
 VCPU_COUNT="$DEFAULT_VCPU"
 RAM_MIB="$DEFAULT_RAM"
@@ -192,7 +193,7 @@ sudo -v
 VM_STARTED=0
 CLEANUP_ON_EXIT=0
 KEEP_VM_DIR_ON_FAIL=1
-DISK_PATH="$ROOTFS"
+DISK_PATH="$VM_DIR/rootfs.ext4"
 
 cleanup() {
   local exit_code=$?
@@ -241,13 +242,13 @@ else
   log "setcap not available; firecracker may need root to open TAP"
 fi
 
+cp --reflink=auto "$ROOTFS" "$DISK_PATH"
+
 if [[ -n "$DISK_BYTES" ]]; then
   if ! command -v resize2fs >/dev/null 2>&1; then
     log "resize2fs required for --disk-size"
     exit 1
   fi
-  DISK_PATH="$VM_DIR/rootfs.ext4"
-  cp --reflink=auto "$ROOTFS" "$DISK_PATH"
   BASE_BYTES="$(stat -c%s "$ROOTFS")"
   if (( DISK_BYTES < BASE_BYTES )); then
     log "disk-size must be >= base image size"
@@ -260,6 +261,20 @@ if [[ -n "$DISK_BYTES" ]]; then
   fi
 fi
 
+if ! command -v debugfs >/dev/null 2>&1; then
+  log "debugfs required to set resolv.conf"
+  exit 1
+fi
+RESOLV_TMP="$VM_DIR/resolv.conf"
+printf '' >"$RESOLV_TMP"
+for ns in ${DNS_SERVERS//,/ }; do
+  printf 'nameserver %s\n' "$ns" >>"$RESOLV_TMP"
+done
+debugfs -w -R "write $RESOLV_TMP /etc/resolv.conf" "$DISK_PATH" >/dev/null 2>&1 || {
+  log "failed to write /etc/resolv.conf into rootfs"
+  exit 1
+}
+
 # Host bridge
 if ! ip link show "$BR_DEV" >/dev/null 2>&1; then
   log "creating host bridge $BR_DEV ($BR_IP/$CIDR)"
@@ -325,7 +340,7 @@ log "configuring machine"
 
 # Boot source
 log "configuring boot source"
-KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0::eth0:off"
+KCMD="console=ttyS0 reboot=k panic=1 pci=off root=/dev/vda rw ip=${GUEST_IP}::${BR_IP}:255.255.255.0::eth0:off hostname=${VM_NAME}"
 
 "${CURL_CMD[@]}" --unix-socket "$API_SOCK" -X PUT http://localhost/boot-source \
   -H "Content-Type: application/json" \