Re: [PATCH net-next] selftests/net: fix bugs in cfg_port initialization

On Sun, Dec 24, 2017 at 12:23 PM, Sowmini Varadhan
[off-list ref] wrote:

If -S is not used in the command line, we should
be binding to *.<cfg-port>. Similarly, cfg_port should be
used to connect to the remote host even if it is processed
after -D. Thus we need to make sure that the cfg_port in
cfg_src_addr and cfg_dst_addr are always initialized
after all other command line options are parsed.

Thanks, Sowmini. Yes, input parsing as is is dependent on
order, which is surprising and fragile.

It would be good to also address the other instance of this at the
same time: protocol family (-4 or -6) has to be set before a call to
setup_sockaddr. Unlike this case, it hits an error() if called in the
"incorrect" order, but that is still a crutch.

The new init_sockaddr_port duplicates most of setup_sockaddr.
More concise is to add a branch to that to skip inet_pton if !str_addr.

But even better will be to save cfg_port, and src + dst addr optargs
as local variables, then call the init function only after parsing when
all state is available. Where this patch adds calls to
init_sockaddr_port, indeed.