Check if resolvconf generates contents of /etc/resolv.conf

1 files changed, 40 insertions, 1 deletions

diff --git a/talpid-core/src/dns/linux/resolvconf.rs b/talpid-core/src/dns/linux/resolvconf.rs
index 3a32eaf406..8bb2c0b885 100644
--- a/talpid-core/src/dns/linux/resolvconf.rs
+++ b/talpid-core/src/dns/linux/resolvconf.rs
@@ -29,6 +29,9 @@ pub enum Error {
 
     #[error(display = "Detected dnsmasq is runing and misconfigured")]
     DnsmasqMisconfigurationError,
+
+    #[error(display = "Current /etc/resolv.conf is not generated by resolvconf")]
+    ResolvconfNotInUseError,
 }
 
 pub struct Resolvconf {
@@ -43,7 +46,18 @@ impl Resolvconf {
             return Err(Error::ResolvconfUsesResolved);
         }
 
-        if Self::is_dnsmasq_running() && Self::is_dnsmasq_configured_wrong() {
+        let is_dnsmasq_running = Self::is_dnsmasq_running();
+
+        // Check if resolvconf is managing DNS by /etc/resolv.conf
+        if !is_dnsmasq_running
+            && !(Self::check_if_resolvconf_is_symlinked_correctly()
+                || Self::check_if_resolvconf_was_generated())
+        {
+            return Err(Error::ResolvconfNotInUseError);
+        }
+
+        // Check if resolvconf can manage DNS via dnsmasq
+        if is_dnsmasq_running && Self::is_dnsmasq_configured_wrong() {
             return Err(Error::DnsmasqMisconfigurationError);
         }
 
@@ -146,4 +160,29 @@ impl Resolvconf {
                     .any(|line| line.trim().starts_with("no-resolv"))
             })
     }
+
+    // Returns true if /etc/resolv.conf contents indicate that they've been generated by resolvconf
+    fn check_if_resolvconf_was_generated() -> bool {
+        match fs::read_to_string("/etc/resolv.conf") {
+            Ok(contents) => contents.contains("Generated by resolvconf"),
+            Err(err) => {
+                log::error!("Couldn't read /etc/resolv.conf - {}", err);
+                return false;
+            }
+        }
+    }
+
+    // Returns true if /etc/resolv.conf is symlinked to resolvconf's runtime directory
+    // (`/var/run/resolvconf`)
+    fn check_if_resolvconf_is_symlinked_correctly() -> bool {
+        match fs::canonicalize("/etc/resolv.conf") {
+            Err(err) => {
+                if err.kind() != io::ErrorKind::NotFound {
+                    log::error!("Failed to canonicalize /etc/resolv.conf - {}", err);
+                }
+                false
+            }
+            Ok(path) => path.starts_with("/var/run/resolvconf"),
+        }
+    }
 }