UnixDomainSocketEndPoint should set length instead of null-terminating

[tmds]

I've used (a copy of) UnixDomainSocketEndPoint to connect to a unix socket with an abstract address (path starts with a zero-byte). The connect call failed with ECONNREFUSED. When I changed the implementation to pass 2 + _encodedPath.Length instead of s_nativeAddressSize in Serialize the connect works.

\cc @stephentoub

[tmds]

This class is internal, so there is no hurry to fix this.

[ericeil]

From the Linux "unix (7)" man page:

   *  abstract: an abstract socket address is distinguished (from a
      pathname socket) by the fact that sun_path[0] is a null byte
      ('\0').  The socket's address in this namespace is given by the
      additional bytes in sun_path that are covered by the specified
      length of the address structure.  (Null bytes in the name have no
      special significance.)  The name has no connection with filesystem
      pathnames.  When the address of an abstract socket is returned,
      the returned addrlen is greater than sizeof(sa_family_t) (i.e.,
      greater than 2), and the name of the socket is contained in the
      first (addrlen - sizeof(sa_family_t)) bytes of sun_path.  The
      abstract socket namespace is a nonportable Linux extension.

So, this is a Linux-specific, and special-purpose, usage of UNIX-domain sockets. I think this is outside of the scope of the (internal) UnixDomainSocketEndPoint type.

[tmds]

@ericeil the null terminating is idependent of the socket being abstract. Please also have a look at the BUGS section in the man page you referenced.