Do not propagate TcpListener.accept() errors

Errors produced by the socket may not be necessarily fatal, meaning that
while a connection might be dropped the process should be able to resume
execution as if nothing happened and accept the next connection.

Error handling for accept() has been copied from NGINX's [1].

[1] https://stackoverflow.com/questions/76955978/which-socket-accept-errors-are-fatal

Signed-off-by: Mroik <mroik@delayed.space>

3 files changed, 23 insertions, 1 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 48808ba..bb34612 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -207,6 +207,12 @@ dependencies = [
 ]
 
 [[package]]
+name = "libc"
+version = "0.2.184"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "48f5d2a454e16a5ea0f4ced81bd44e4cfc7bd3a507b61887c99fd3538b28e4af"
+
+[[package]]
 name = "libsqlite3-sys"
 version = "0.37.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -273,6 +279,7 @@ version = "0.1.0"
 dependencies = [
  "anyhow",
  "env_logger",
+ "libc",
  "log",
  "rusqlite",
  "tokio",
diff --git a/Cargo.toml b/Cargo.toml
index 570c437..cbd5e80 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,6 +6,7 @@ edition = "2024"
 [dependencies]
 anyhow = "1.0.102"
 env_logger = "0.11.10"
+libc = "0.2.184"
 log = "0.4.29"
 rusqlite = "0.39.0"
 tokio = { version = "1.51.0", features = ["macros", "rt-multi-thread", "sync"] }
diff --git a/src/smtp_server.rs b/src/smtp_server.rs
index bacf8eb..e6c0efc 100644
--- a/src/smtp_server.rs
+++ b/src/smtp_server.rs
@@ -27,7 +27,21 @@ impl SmtpServer {
     pub async fn run(&mut self, tx_processor: Sender<Mail>) -> Result<()> {
         self.running = true;
         while self.running {
-            let (stream, addr) = self.listener.accept()?;
+            let (stream, addr) = match self.listener.accept() {
+                Ok(v) => v,
+                Err(e) => match e.raw_os_error() {
+                    Some(libc::EMFILE | libc::ENFILE) => return Err(anyhow::Error::from(e)),
+                    Some(libc::ECONNABORTED) => {
+                        log::error!("{}", e);
+                        continue;
+                    }
+                    Some(libc::EAGAIN) => continue,
+                    _ => {
+                        log::warn!("{}", e);
+                        continue;
+                    }
+                },
+            };
             let session = SessionHandler {
                 addr,
                 tx_processor: tx_processor.clone(),