RequestCtx.IsTLS() doesn't recognizeperIPConn when TLS is used

[tysg]

Steps To Reproduce: See gofiber/fiber#1456

Description:

When Server.MaxConnsPerIP is set to a non-zero value, the server wraps every incoming connection to a perIPConn in acquirePerIPConn. perIPConn has the struct definition:

type perIPConn struct {
	net.Conn

	ip               uint32
	perIPConnCounter *perIPConnCounter
}

When a tls.Conn comes in, acquirePerIPConn assigns the tls.Conn to the field Conn in the return value, which restricts the tls.Conn to net.Conn.

fasthttp/peripconn.go

Lines 48 to 59 in 9466cd7

	func acquirePerIPConn(conn net.Conn, ip uint32, counter *perIPConnCounter) *perIPConn {
	v := counter.pool.Get()
	if v == nil {
	v = &perIPConn{
	perIPConnCounter: counter,
	}
	}
	c := v.(*perIPConn)
	c.Conn = conn
	c.ip = ip
	return c
	}

Therefore, the IsTLS() check on perIPConn will fail, as it doesn't implement the connTLSer any more.

fasthttp/server.go

Lines 709 to 720 in 9466cd7

	func (ctx *RequestCtx) IsTLS() bool {
	// cast to (connTLSer) instead of (*tls.Conn), since it catches
	// cases with overridden tls.Conn such as:
	//
	// type customConn struct {
	// *tls.Conn
	//
	// // other custom fields here
	// }
	_, ok := ctx.c.(connTLSer)
	return ok
	}

Furthermore, adding the following failing test in server_test.go confirmed the discovery:

func TestRequestCtxIsTLS(t *testing.T) {
	t.Parallel()

	var ctx RequestCtx

        // ... omitted

	ctx.c = &struct {
		net.Conn
		fooBar bool
	}{Conn: &tls.Conn{}}
	if !ctx.IsTLS() {
		t.Fatal("IsTLS must return true") // fails
	}
}

[tysg]

I would love to work on this if the maintainers can point me the correct direction :)

[erikdubbelboer]

@tysg the simplest way is probably for RequestCtx.IsTLS to check for perIPConn like this example: https://play.golang.org/p/p6zHsqpKhyC
If you can make a pull request for this including the test from above that would be great! 🙏

[tysg]

@erikdubbelboer Thanks for the code snippet! I submitted the PR under #1064