linux - SO_REUSEPORT 与组播 UDP 的使用

Question

在关于 SO_REUSEPORT 的讨论中，以下问题已发布到 reddit ，却无人接听。我想知道 Stack Overflow 是否知道答案。

Can anyone tell me how this interacts with multicast?

I've got an application where the program should listen to multicast UDP messages, and this program may be started multiple times on the same computer. When a message comes it, all listening processes should get it.

I've noticed that on Linux, it works fine if I don't set SO_REUSEPORT, and if I understand correctly, setting SO_REUSEPORT may be the wrong thing to do -- I don't want UDP messages distributed between the processes, I want all processes to get a copy. However, on OS X, the second execution of the program fails to find a free port unless SO_REUSEPORT is set.

tl;dr: Is it expected to set SO_REUSEPORT when using multicast?

Answer 1

通过 SO_REUSEPORT，可以将多个套接字绑定(bind)到同一个端口和地址。唯一的要求是早期的套接字必须设置此选项。因此，如果我们想要两个套接字，sock1 和 sock2 绑定(bind)到同一个端口(和地址)，那么只有当 sock1 和 sock2 都设置了 SO_REUSEPORT 时，s2 才能重用端口/地址。关于多播，如果 sock1 和 sock2 都是同一个多播组的接收者，那么它们都会得到一份数据副本。

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