If UdpFrame fails when sending, it cannot flush or send any new message #7648
Description
Version
├── tokio v1.47.1
│ └── tokio-macros v2.5.0 (proc-macro)
└── tokio-util v0.7.16
└── tokio v1.47.1 (*)
Platform
Reproduced on
24.6.0 Darwin Kernel Version 24.6.0: Mon Aug 11 21:11:04 PDT 2025; root:xnu-11417.140.69.701.11~1/RELEASE_ARM64_T6031 arm64
and on
Linux 6.1.0-23-amd64 #1 SMP PREEMPT_DYNAMIC Debian 6.1.99-1 (2024-07-15) x86_64 GNU/Linux
Description
If an error happens when using send from SinkEx on an UdpFramed, it doesn't seem to flush/discard the internal buffer, so any new attempt to use it will fail, even with different message and address:
Example:
use bytes::Bytes;
use futures::SinkExt;
use std::{net::SocketAddr, str::FromStr};
use tokio::net::UdpSocket;
use tokio_util::{codec::BytesCodec, udp::UdpFramed};
#[tokio::main]
async fn main() {
let udp_socket = UdpSocket::bind(SocketAddr::from_str("127.0.0.1:8080").unwrap()).await.unwrap();
let mut framed = UdpFramed::new(udp_socket, BytesCodec::new());
let msg = Bytes::from_static(b"UdpFramed test!");
let invalid_address = SocketAddr::from_str("0.0.0.0:80").unwrap();
let valid_address = SocketAddr::from_str("127.0.0.1:80").unwrap();
// 1st. Sending to a valid address. This works.
send(&mut framed, msg.clone(), valid_address).await;
// 2nd. Send to invalid address, this fails.
send(&mut framed, msg.clone(), invalid_address).await;
// 3rd. Sending to the same previous valid address. This keeps failing :(
send(&mut framed, msg.clone(), valid_address).await;
}
async fn send(framed: &mut UdpFramed<BytesCodec>, msg: Bytes, addr: SocketAddr) {
match framed.send((msg, addr)).await {
Ok(_) => println!("OK, sent msg to address {}", addr),
Err(e) => println!("Error trying to send msg to address {}: {}", addr, e),
}
}I expected first and third send to work, and second to fail, instead, only first worked and second and third failed:
OK, sent msg to address 127.0.0.1:80
Error trying to send msg to address 0.0.0.0:80: No route to host (os error 65)
Error trying to send msg to address 127.0.0.1:80: No route to host (os error 65)
Note: this is independent from the underlying Error that causes the failure. I found the problem when trying to send messages to a list of IP addresses, and an IPv6 address slipped in.
I got
"Address family not supported by protocol"
when it tried the IPv6 address, and then the same error for all the following IPv4 addresses