Set up a monotonic clock boot time offset in the VM

micro-activate.rs

@@ -8,6 +8,8 @@ const MS_NODEV: c_ulong = 0x04;
 const MS_RELATIME: c_ulong = 0x200000;
 const MS_STRICTATIME: c_ulong = 0x1000000;
 
+const CLONE_NEWTIME: c_int = 0x80;
+
 unsafe extern "C" {
     fn mount(
         src: *const c_char,
@@ -17,6 +19,7 @@ unsafe extern "C" {
         data: *const c_void,
     ) -> c_int;
     fn getrandom(buf: *mut u8, buflen: usize, flags: u32) -> c_int;
+    fn unshare(flags: c_int) -> c_int;
 }
 
 fn gen_machine_id() -> String {
@@ -133,6 +136,17 @@ fn main() -> Result<(), std::io::Error> {
         );
     }
 
+    if let Ok(offset) = std::env::var("BOOT_TIME_OFFSET") {
+        if unsafe { unshare(CLONE_NEWTIME) } != 0 {
+            eprintln!("[micro-activate] Could not unshare time!");
+        } else {
+            std::fs::write(
+                "/proc/self/timens_offsets",
+                format!("monotonic {offset}\nboottime {offset}\n"),
+            )?;
+        }
+    }
+
     let mut args = std::env::args_os().skip(1);
     let cmd = args.next().unwrap();
     Err(std::process::Command::new(cmd).args(args).exec())

munix

@@ -204,6 +204,10 @@ if [ "$USING_PUBLISH" -eq 1 ]; then
   printf "\n\n\n\e[1mNote: due to a \e[31mBUG\e[39m with port publishing (-p) you have to send the first outgoing packet (e.g. ping -c1 8.8.8.8) before your ports start receiving traffic. Sorry for the inconvenience!\e[39;0m\n\n\n\n" >&2
 fi
 
+# xxx: some time is lost to the starting process..
+[[ "$(</proc/uptime)" =~ ([0-9]+)\.([0-9]+) ]]
+BOOT_TIME_OFFSET="${BASH_REMATCH[1]} $(( ${BASH_REMATCH[2]} * 1000000 ))"
+
 # do not 'exec' because of cleanup :)
 bwrap --unshare-all --share-net \
   --uid $MICROVM_UID --gid $MICROVM_GID \
@@ -233,6 +237,7 @@ bwrap --unshare-all --share-net \
     -e container=munix \
     -e MICROVM_CLOSURE="$MICROVM_CLOSURE" \
     -e MICROVM_UID="$MICROVM_UID" -e MICROVM_GID="$MICROVM_GID" \
+    -e BOOT_TIME_OFFSET="$BOOT_TIME_OFFSET" \
     -i -t -- "${MICROVM_COMMAND[@]}" \
   13< /etc/resolv.conf \
   14< /etc/localtime