Nmap Development: Re: Ncat: socket bind error on Mac OS X

[David Fifield <david () bamsoftware com>]

On Sun, Jul 27, 2008 at 01:14:40PM +0200, Dirk Loss wrote:
> on Mac OS X 10.5.4 (Intel) Ncat dies with the following error when I try 
> to put it into listening mode:
>
> $ ncat -l 22222
> bind: Invalid argument
>
> Running Ncat as root, switching to UDP or disabling IPv6 in my system 
> preferences did not help. I verified that there is no other process 
> listing on my local TCP port 22222.
>
> Apparently the bind() call in sys_wrap.c returns -1 and errno = 22 
> (EINVAL). According to the man page [1], this means that either the 
> "socket is already bound to an address and the protocol does not support 
> binding to a new address" or the "socket may have been shut down."
I think I have tracked this down. bind is being picky about the address
length. Currently do_listen is calling Bind with sizeof(srcaddr), which
is 128. If I change it to sizeof(struct sockaddr_in), which is 16, then
it works. Of course, that only works for IPv4 addresses, so it needs to
be based on the address family.

BSDs have an extra sockaddr.sa_len (and sockaddr_storage.ss_len, and
sockaddr_in.sin_len) member. Currently it's always set to 0 by memset. I
tried setting it to a proper value and it didn't seem to make a
difference. However, changing the address length passed to bind did
work.

David Fifield

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