Describe the bug

The Connection header is a hop-by-hop header, and proxy servers should not forward it. However, Pingora appears to forward the Connection header from the client directly to the upstream server.

For example, if a client sends Connection: close, Pingora will forward Connection: close to the upstream server. In some environments, this may cause the connection between Pingora and the upstream to be closed, which can lead to performance issues.

I also tested the hop-by-hop headers listed in RFC 2616, and all of them were forwarded to the upstream server without modification.

Pingora info

Pingora version: 0.6.0
Rust version: 1.90.0
Operating system version: Ubuntu 22.04

Steps to reproduce

This is the source code of the load balancer. It simply proxies the request to localhost:3000.

use async_trait::async_trait;
use pingora::prelude::*;

struct LB;

#[async_trait]
impl ProxyHttp for LB {
    type CTX = ();
    fn new_ctx(&self) -> Self::CTX {}

    async fn upstream_peer(&self, _session: &mut Session, _ctx: &mut ()) -> Result<Box<HttpPeer>> {
        let peer = HttpPeer::new("127.0.0.1:3000", false, "".to_string());
        Ok(Box::new(peer))
    }
}

fn main() -> pingora::Result<()> {
    env_logger::init();

    let mut my_server = Server::new(None)?;
    my_server.bootstrap();

    let mut lb = http_proxy_service(&my_server.configuration, LB);
    lb.add_tcp("[::]:8000");
    my_server.add_service(lb);

    my_server.run_forever();
}

Start this server.

In another shell, start a TCP server by using socat. Note that this server never returns a response.

socat TCP-LISTEN:3000,reuseaddr,fork -

Send an HTTP request like the following from another shell. Then, socat will print the HTTP request sent from Pingora.

nc -C localhost 8000 <<'EOF'
GET / HTTP/1.1
Host: example.com
Connection: close

EOF

Expected results

The upstream server should not receive Connection: close header given by the client.

GET / HTTP/1.1
Host: example.com

Observed results

socat outputs the following text, which is a HTTP request sent from Pingora to the upstream server.

GET / HTTP/1.1
Host: example.com
Connection: close

Connection: close is included in the request.