Don't tug on that, you never know what it might be attached to

Re:Don't tug on that, you never know what it might be attach... by JoshTriplett on Friday July 01, 2016 @08:48PM (#12020840)

That does something entirely different; see Documentation/networking/ip-sysctl.txt (online version at https://www.kernel.org/doc/Documentation/networking/ip-sysct...). ip_local_port_range sets the range of ports used as source ports for outbound connections that don't bind to a specific port.

I checked for a sysctl controlling the ability to bind to privileged ports before writing my comment. The relevant code in the kernel compares against a hardcoded #define PROT_SOCK 1024, and doesn't have any means to disable that check. See inet_bind in net/ipv4/af_inet.c .

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Re:Don't tug on that, you never know what it might be attach... by rxseger on Saturday July 02, 2016 @03:14AM (#12021723)

FreeBSD has the sysctls you are looking for to control the reserved port range, allowing unprivileged users to bind (curious that Linux doesn't):

    $ sudo sysctl net.inet.ip.portrange.reservedlow=10
    net.inet.ip.portrange.reservedlow: 0 -> 10
    $ nc -vvl 1
    ^C
    $ sudo sysctl net.inet.ip.portrange.reservedlow=0 
    net.inet.ip.portrange.reservedlow: 10 -> 0
    $ nc -vvl 1
    nc: Permission denied

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