Choose client ports in a well-known range #134
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Instead of letting the kernel assign us a port number, request a specific port number and increment until one is available. This makes writing firewall rules easier, when a known number of clients will be in use.
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I'm undecided if this should be a configure option (or at least the starting port number) vs. always-on. |
| @@ -38,17 +39,20 @@ ZOpenPort(u_short *port) | |||
| if (setsockopt(__Zephyr_fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof val) < 0) | |||
| return errno; | |||
| } else { | |||
| bindin.sin_port = 0; | |||
| bindin.sin_port = htons(60000); | |||
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Note that Mosh uses almost the same port range, picking the first available port in 60001–60999.
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Mosh's range was prominent in shaping my initial choice here (though I find it amusing that I was off by one for the start port!). Probably I was thinking that a single hole in the firewall would cover both, but some amount of discussion is appropriate before a choice is made.
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I’m a little worried it might break Mosh for users who only open one firewall port for it instead of a range. Only a little, since those users are probably smart enough to figure out what happened. Maybe that risk can be avoided by starting at 60500 or something.
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We had a bit of discussion about this involving Keith from the mosh side and a few other folks. The conclusion (if there could be said to be one) was:
To the extent it matters, though, I guess it's probably better for
every random UDP app that needs a range of port numbers (instead of a
single port that can be multiplexed because each peer will use a
different IP address or port) to 'standardize' on 60000-61000 than for
us all to go separately. So, go for it if you want.
Instead of letting the kernel assign us a port number, request
a specific port number and increment until one is available.
This makes writing firewall rules easier, when a known number
of clients will be in use.