Happy Eyeballs (HE) started out by describing a mechanism that prefers IPv6 connections while ensuring a fast fallback to IPv4 when IPv6 fails. The IETF is currently working on the third version of HE. While the standards include recommendations for HE parameters choices, it is up to the client and OS to implement HE. In this paper we investigate the state of HE in various clients, particularly web browsers and recursive resolvers. We introduce a framework to analyze and measure client's HE implementations and parameter choices. According to our evaluation, only Safari supports all HE features. Safari is also the only client implementation in our study that uses a dynamic IPv4 connection attempt delay, a resolution delay, and interlaces addresses. We further show that problems with the DNS A record lookup can even delay and interrupt the network connectivity despite a fully functional IPv6 setup with Chrome and Firefox. We publish our testbed measurement framework and a web-based tool to test HE properties on arbitrary browsers.

翻译：Happy Eyeballs（HE）最初被描述为一种优先选择IPv6连接、同时在IPv6失败时确保快速回退至IPv4的机制。IETF目前正在制定HE的第三个版本。虽然标准中包含了对HE参数选择的建议，但具体实现仍取决于客户端与操作系统。本文研究了各类客户端（特别是网页浏览器与递归解析器）中HE的实现现状。我们提出了一种用于分析与测量客户端HE实现及参数选择的框架。根据评估结果，仅Safari支持所有HE特性。Safari同时也是本研究中唯一采用动态IPv4连接尝试延迟、解析延迟及地址交错机制的客户端实现。我们进一步指出，在Chrome和Firefox完全正常的IPv6配置环境下，DNS A记录查询问题仍可能导致网络连接延迟甚至中断。我们公开了测试床测量框架及基于网页的工具，用于检测任意浏览器的HE特性。