XHTTP transport: Add BBR and brutal-force congestion control for H3

[Katze-942]

I noticed that VLESS TLS with XHTTP transport and ALPN H3 is significantly slower (~2x) compared to regular HTTP/2, and decided to investigate.

Turns out quic-go uses Reno congestion control by default, while TCP gets BBR from the Linux kernel - likely a contributing factor. On top of that, quic.ListenEarly was called with nil config, so all QUIC parameters were left at quic-go defaults. The default receive windows (512 KB) can also become a bottleneck on high-bandwidth or high-latency links. (removed: keeping quic-go default window sizes) Hard to say which of these matters most, but together they should make a noticeable difference.

Both BBR and Brutal implementations reuse the existing transport/internet/hysteria/congestion package (BBR is a port of Google's BBR v1 from Chromium, Brutal is from Hysteria2) to avoid code duplication and build on what's already in the codebase.

Also added a "congestion" setting to tlsSettings:

• "bbr" (default) — BBR congestion control
• "reno" — quic-go default
• "force-brutal" — Brutal congestion control (requires "up" field)

"force-brutal" reuses the existing brutal-force sender from the Hysteria transport (transport/internet/hysteria/congestion/brutal). It sends at a fixed rate regardless of packet loss. Requires the "up" field specifying the target upload bandwidth (same format as Hysteria2, e.g. "100 mbps").

{
  "tlsSettings": {
    "alpn": ["h3"],
    "quic": {
      "congestion": "force-brutal",
      "up": "100 mbps"
    }
  }
}

[Fangliding]

这事在加hy传输的时候就该弄了
不过调整QUIC参数是可以被外部观察到的 最开始设计的时候甚至都考虑keepalive特征了改这个是不是有点不太好
我觉得服务端加几行默认bbr就行了 别的不改
cc @RPRX

[LjhAUMEM]

客户端 dialer 可以先不动，服务端可以先默认设个 bbr 先用着，反正目前也没有 cdn 可以 h3 回源

conn window 那些没必要过度追求 hy，保持默认值就好，congestion 可以在以后动客户端 dialer 的时候再加，也就是 protoc 可以先不用修改

[RPRX]

目前用的人不多，两边都默认 bbr 就行，quic-go 也不至于一直不加 bbr 吧

[RPRX]

@Fangliding @LjhAUMEM 话说 Xray-core 加了 hy2 入站后真的还会有人直接起 XHTTP/3 入站吗，又不是 CDN 支持 h3 回源

所以我觉得给客户端加 bbr 会更有用一些，如果有人弄个 brutal 的话到 CDN 的上行拉满

[LjhAUMEM]

@Fangliding @LjhAUMEM 话说 Xray-core 加了 hy2 入站后真的还会有人直接起 XHTTP/3 入站吗，又不是 CDN 支持 h3 回源

hy 的传输层要求设置个 auth，可能不想设置的会用 xhttph3 吧

目前用的人不多，两边都默认 bbr 就行，quic-go 也不至于一直不加 bbr 吧

两边都默认也行，不过我觉得国内上行 bbr 没啥用

[Fangliding]

#5549 (comment)

[RPRX]

#5549 (comment)

那咋说，XHTTP/3 改成默认上行 cubic、下行 bbr 吗

[gumiruo]

@RPRX xhttp h3也准备能吃bbr了？

[Fangliding]

我感觉下行默认BBR就行了 别的不用改 就几行代码

[gfw-killer]

不过调整QUIC参数是可以被外部观察到的 最开始设计的时候甚至都考虑keepalive特征了改这个是不是有点不太好

You like to have no options to tune and the PR has hardcoded parameters to tune
Why not have options so user can tune it the way he likes/needs? like Hy2

Xray-core/transport/internet/hysteria/dialer.go

Lines 196 to 207 in efdf21e

	QUICConfig: &quic.Config{
	InitialStreamReceiveWindow: c.config.InitStreamReceiveWindow,
	MaxStreamReceiveWindow: c.config.MaxStreamReceiveWindow,
	InitialConnectionReceiveWindow: c.config.InitConnReceiveWindow,
	MaxConnectionReceiveWindow: c.config.MaxConnReceiveWindow,
	MaxIdleTimeout: time.Duration(c.config.MaxIdleTimeout) * time.Second,
	KeepAlivePeriod: time.Duration(c.config.KeepAlivePeriod) * time.Second,
	DisablePathMTUDiscovery: c.config.DisablePathMtuDiscovery,
	EnableDatagrams: true,
	MaxDatagramFrameSize: MaxDatagramFrameSize,
	DisablePathManager: true,
	},

#5549 (comment)

那咋说，XHTTP/3 改成默认上行 cubic、下行 bbr 吗

I see no CUBIC CC here, quic-go default is Reno and the added CC is BBR
am i missing something?

[Fangliding]

Why not have options so user can tune it the way he likes/needs? like Hy2

暴露无意义的参数只会使配置选项越来越臃肿 你这么喜欢tune你知道bbr里也有一堆硬编码的经验主义参数吗？
HY2让改只是因为官端让改 实际99%的人不会去动这个配置

[RPRX]

不过对于 QUIC 来说长远来看本来就应该可以自己配置 congestion 参数，可能应该搞 tlsSessings 里面

这个 PR 的话先把两端都改为默认 bbr 吧，其它的以后再说

[Katze-942]

Should I remove the custom QUIC receive window sizes (2/16/5/32 MB) and revert to quic-go defaults to avoid an externally observable fingerprint?

---

请问是否需要移除自定义的 QUIC 接收窗口大小（2/16/5/32 MB），恢复为 quic-go 默认值，以避免外部可观测的指纹特征？

[Katze-942]

不过对于 QUIC 来说长远来看本来就应该可以自己配置 congestion 参数，可能应该搞 tlsSessings 里面

这个 PR 的话先把两端都改为默认 bbr 吧，其它的以后再说

In the current PR, BBR is already set as the default for both sides. I can move the congestion setting to tlsSettings if needed.

---

在当前 PR 中，两端已默认使用 BBR。如果需要，我可以将 congestion 配置移到 tlsSettings 中。

[RPRX]

其实我觉得 quic-go 本身就很特征了，加上 Hy2 搞出的运营商 UDP QoS，XHTTP/3 现在没多少人用所以还好吧

往 tlsSettings 里加 QUIC 参数的话 Hy2 传输层也要改，所以我的意思是这个 PR 先别管这些，晚点交给 @LjhAUMEM

[LjhAUMEM]

在这里改我也没啥问题，要不直接把 hy 的 congestion 逻辑复制一个过来，也别移到 tls 设置里了

只是对于 conn window 那些我有点犹豫，默认值应该就行，应该没必要完全对齐

[Katze-942]

Should I make the window sizes configurable in the config rather than hardcoded?

---

是否需要将 window sizes 做成可配置的，而不是硬编码在代码中？

[LjhAUMEM]

Should I make the window sizes configurable in the config rather than hardcoded?

是否需要将 window sizes 做成可配置的，而不是硬编码在代码中？

Simply remove these hard-coded conn windows.

If you want congestion configuration, add the force-brutal option as well (this may require an additional up/rate/bandwidth field); otherwise, removing the congestion configuration only retains the default bbr.

[Katze-942]

Removed custom QUIC receive window sizes, using quic-go defaults now.

I can add force-brutal too. Hysteria2 uses up with a string like "100 mbps" for the bandwidth field. Should I do the same here?

---

已移除自定义 QUIC 接收窗口大小，改用 quic-go 默认值。

我可以加上 force-brutal。Hysteria2 的带宽字段叫 up，格式是 "100 mbps" 这样的字符串。这里也这样做可以吗？

[LjhAUMEM]

@RPRX 我想的是除了协商的 brutal 剩下的都可以接过来，但 force 可能要一个新的字段，和 hy 一样 up 还是

[Katze-942]

Ok, I've added the force-brutal algorithm with the "up" field for now.

---

好的，我暂时添加了 force-brutal 算法和 "up" 字段。

[RPRX]

卧槽一会儿没看把 brutal 加给 XHTTP/3 了

要不把所有这些东西都在 tlsSettings 里开一个 "quic": {} 放进去吧，@LjhAUMEM 这样是否可行

[Katze-942]

卧槽一会儿没看把 brutal 加给 XHTTP/3 了

Haha, it's not exactly brutal. It's force-brutal, I'll add brutal support in another PR.

---

哈哈，这不完全是 brutal。这是 force-brutal，我会在另一个 PR 中添加 brutal 的支持。

[Katze-942]

要不把所有这些东西都在 tlsSettings 里开一个 "quic": {} 放进去吧，@LjhAUMEM 这样是否可行

I'd really like to move this to quic, because right now these settings look a bit out of place in xhttpSettings:

---

我确实想把这些移到 quic 里，因为目前这些设置放在 xhttpSettings 里看起来不太合适：

  "xhttpSettings": {                                                                          
    "quic": {                                                                                 
      "congestion": "force-brutal",
      "up": "100 mbps"
    }
  }

[LjhAUMEM]

卧槽一会儿没看把 brutal 加给 XHTTP/3 了

要不把所有这些东西都在 tlsSettings 里开一个 "quic": {} 放进去吧，@LjhAUMEM 这样是否可行

也可以，如果他愿意做的话

I'll add brutal support in another PR.

no need to add brutal, xhttp3 is an unauth transport, but force-brutal can be added

I'd really like to move this to quic, because right now these settings look a bit out of place in xhttpSettings:

Then move the settings to TLS, or keep only the default bbr part (including temporarily removing force-brutal, congestion configuration) and this PR can be merged.

[Katze-942]

Moved settings to "tlsSettings": { "quic": {} }

---

将设置移至 "tlsSettings": { "quic": {} }

[LjhAUMEM]

looks good to me

@RPRX 剩下的我再移也行，对话效率有点低

[Fangliding]

looks good to me

@RPRX 剩下的我再移也行，对话效率有点低

话说你看过 #5712 没

[LjhAUMEM]

话说你看过 #5712 没

刚刚才看到，最近没关注 issue，那个艾特不知道是我邮件没有还是看漏了，应该是 break 了配置导致 udpmask 没设置上