set reasonable TCP keepalive timeout

src/tools/socket.rs

@@ -0,0 +1,23 @@
+use std::os::unix::io::RawFd;
+
+use nix::sys::socket::sockopt::{KeepAlive, TcpKeepIdle};
+use nix::sys::socket::setsockopt;
+
+pub const PROXMOX_BACKUP_TCP_KEEPALIVE_TIME: u32 = 120;
+
+/// Set TCP keepalive time on a socket
+///
+/// See "man 7 tcp" for details.
+///
+/// The default on Linix is 7200 (2 hours) which is much too long for
+/// our backup tools.
+pub fn set_tcp_keepalive(
+    socket_fd: RawFd,
+    tcp_keepalive_time: u32,
+) -> nix::Result<()> {
+
+    setsockopt(socket_fd, KeepAlive, &true)?;
+    setsockopt(socket_fd, TcpKeepIdle, &tcp_keepalive_time)?;
+
+    Ok(())
+}