4 files changed, 30 insertions, 15 deletions
diff --git a/mullvad-daemon/src/logging.rs b/mullvad-daemon/src/logging.rs
index 958d5321e6..9988ea6be2 100644
--- a/mullvad-daemon/src/logging.rs
+++ b/mullvad-daemon/src/logging.rs
@@ -6,9 +6,10 @@ use chrono;
 use log;
 
 use std::fmt;
-use std::fs;
 use std::io;
-use std::path::{Path, PathBuf};
+use std::path::PathBuf;
+
+use talpid_core::logging::rotate_log;
 
 error_chain! {
     errors {
@@ -17,6 +18,9 @@ error_chain! {
             display("Unable to open log file for writing: {}", path.display())
         }
     }
+    links {
+        RotateLog(::talpid_core::logging::Error, ::talpid_core::logging::ErrorKind);
+    }
     foreign_links {
         SetLoggerError(log::SetLoggerError);
         Io(io::Error);
@@ -138,15 +142,3 @@ fn escape_newlines(text: String) -> String {
 fn escape_newlines(text: String) -> String {
     text.replace("\n", LINE_SEPARATOR)
 }
-
-pub fn rotate_log(file: &Path) -> Result<()> {
-    let backup = file.with_extension("old.log");
-    fs::rename(file, backup).unwrap_or_else(|error| {
-        if error.kind() != io::ErrorKind::NotFound {
-            warn!("Failed to rotate log file ({})", error);
-        }
-    });
-
-    fs::File::create(file).chain_err(|| "Unable to create new log file")?;
-    Ok(())
-}
diff --git a/mullvad-daemon/src/tunnel_state_machine/connecting_state.rs b/mullvad-daemon/src/tunnel_state_machine/connecting_state.rs
index c05d85d217..9175fe3239 100644
--- a/mullvad-daemon/src/tunnel_state_machine/connecting_state.rs
+++ b/mullvad-daemon/src/tunnel_state_machine/connecting_state.rs
@@ -8,6 +8,7 @@ use futures::sink::Wait;
 use futures::sync::{mpsc, oneshot};
 use futures::{Async, Future, Sink, Stream};
 
+use talpid_core::logging;
 use talpid_core::security::{NetworkSecurity, SecurityPolicy};
 use talpid_core::tunnel::{CloseHandle, TunnelEvent, TunnelMetadata, TunnelMonitor};
 use talpid_types::net::{TunnelEndpoint, TunnelEndpointData};
@@ -17,7 +18,6 @@ use super::{
     DisconnectingState, EventConsequence, Result, ResultExt, SharedTunnelStateValues,
     StateEntryResult, TunnelCommand, TunnelParameters, TunnelState, TunnelStateWrapper,
 };
-use logging;
 
 const MIN_TUNNEL_ALIVE_TIME: Duration = Duration::from_millis(1000);
 
diff --git a/talpid-core/src/lib.rs b/talpid-core/src/lib.rs
index 1ee4d3b6ad..b96764848f 100644
--- a/talpid-core/src/lib.rs
+++ b/talpid-core/src/lib.rs
@@ -47,6 +47,9 @@ pub mod process;
 /// Abstracts over different VPN tunnel technologies
 pub mod tunnel;
 
+/// Helper function to preserve previous log files.
+pub mod logging;
+
 /// Abstractions and extra features on `std::mpsc`
 pub mod mpsc;
 
diff --git a/talpid-core/src/logging.rs b/talpid-core/src/logging.rs
new file mode 100644
index 0000000000..fe77297b84
--- /dev/null
+++ b/talpid-core/src/logging.rs
@@ -0,0 +1,20 @@
+use std::path::Path;
+use std::{fs, io};
+
+error_chain!{}
+
+/// Create a new log file while backing up a previous version of it.
+///
+/// A new log file is created with the given file name, but if a file with that name already exists
+/// it is backed up with the extension changed to `.old.log`.
+pub fn rotate_log(file: &Path) -> Result<()> {
+    let backup = file.with_extension("old.log");
+    fs::rename(file, backup).unwrap_or_else(|error| {
+        if error.kind() != io::ErrorKind::NotFound {
+            warn!("Failed to rotate log file ({})", error);
+        }
+    });
+
+    fs::File::create(file).chain_err(|| "Unable to create new log file")?;
+    Ok(())
+}