CODEWITHSUNDEEP
swiftmacossocketsunixposix
Antwan van Houdt
Antwan van Houdt

Reputation: 6991

Listening socket max connections hit early, while having increased the limit

I have a simple listening socket, that stops accepting socket, returing EN_FILE after only 13 connections. I have tried using sysctl in the following manner:

$ sysctl kern.maxfiles
kern.maxfiles: 12288
$ sysctl kern.maxfilesperproc
kern.maxfilesperproc: 10240
$ sudo sysctl -w kern.maxfiles=1048600
kern.maxfiles: 12288 -> 1048600
$ sudo sysctl -w kern.maxfilesperproc=1048576
kern.maxfilesperproc: 10240 -> 1048576
$ ulimit -S -n
256
$ ulimit -S -n 1048576
$ ulimit -S -n
1048576

But this doesn't seem to solve the issue, is a reboot required specifically on OSX? I need it for a singular test so I wasn't planning on making it permanent in /etc/sysctl.conf

Socket creation:

 #if os(Linux)
            fileDescriptor = Glibc.socket(AF_INET, Int32(SOCK_STREAM.rawValue), 0)
        #else
            fileDescriptor = Darwin.socket(AF_INET, SOCK_STREAM, 0)
        #endif

And the accepting part:

let result = withUnsafePointer(to: &address) {
            $0.withMemoryRebound(to: sockaddr.self, capacity: 1) { sockAddress in
                // Do nothing
                bind(fileDescriptor, sockAddress, UInt32(MemoryLayout<sockaddr_in>.size))
            }
        }

'

let clientFD = accept(fileDescriptor, nil, nil)
        if( clientFD == EMFILE || clientFD == ENFILE ) {
            print("[\(type(of: self))] WARNING: Maximum number of open connections has been reached")
            close(clientFD)
            return nil
        }

Notes

libtls ( LibreSSL 2.5.5 ) is used after accept().

EN_FILE is the value returned, where I'd personally expect EM_FILE

Upvotes: 1

Views: 61

Answers (1)

Ken Thomases
Ken Thomases

Reputation: 90581

You're comparing the accepted file descriptor against error codes. That doesn't make sense. Since file descriptors and error codes are both typically small integers, of course you're going to get a "match" eventually.

You want to compare clientFD to -1 and then check errno against EMFILE or ENFILE.

Upvotes: 1

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