optimize(mtu): Set lowest MTU among bound interfaces to dae0/dae0peer #827
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要做 newlinkCallback 动态更新 mtu 😟 先 draft 之后再改 |
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Background
0.5 -> 0.6 引入 dae0 有个被忽视的变化——mtu 可能被缩小了，因为 dae0/dae0peer mtu 被硬编码为 1500. 这可能导致了 #509.
考虑 0.5 的 lan 劫持流量场景，假如 lan interface mtu 是 9000，那么被劫持流量的 tcp 握手协商 mss 为 9000 (9000-tcphdr-iphdr, 不要在意细节)，最终能有 9000 大包到达 lan；但是 0.6 由于 dae0peer mtu 1500，导致握手 mss 协商为 1500，最终 tcp 会拆成小包抵达 lan。这不仅导致性能有所下降，而且触发了 tls 嗅探的 bug (#555).
这个 pr 尝试修复这种现象，让 dae0/dae0peer mtu 设置到 min(lan_interfaces..., wan_interfaces...) ，这样保底 1500，但允许 >1500 的 mtu。
理论上 wan 代理不受 dae0/dae0peer mtu 影响，因为有 gso。
扩大 mtu 是一件容易崩坏的事情，多测测再合并。
Checklist
Full Changelogs
Issue Reference
Closes #509
Test Result