Re: spipe optimization: avoid socketpair(2) when unnecessary

[Bill Trost <trost@cloud.rain.com>]

Colin Percival wrote:
    On 04/14/13 16:02, Bill Trost wrote:
    > Below is a quick hack to eliminate the socket pair used to
    > pushbits in the case that file descriptor 0 really is a socket.

    Interesting -- do you have a use case where this optimization
    is likely to matter? It seems to me that this is only relevant
    if you are pushing a very large number of bits through; and
    even then, I'd expect the cryptographic work to overwhelm the
    data-copying and keep the speedup from this to a minimum.

I agree. My plan was to use this between thunderbird and an
spipe connection to my IMAP client, using a little wrapper
around spipe to verify that the connecting client has the
same user ID as the wrapper. It seemed easier than trying to
convince thunderbird to connect to a unix-domain socket....

    > [...]
    >         /* Set up a connection. */
    > -       if (proto_conn_create(s[1], sas_t, 0, opt_f, K, opt_o,
    > +       if (proto_conn_create(socket0 ? 0 : s[1], sas_t, 0, opt_f, K, opt_o,

    This is a bug.... In some cases spipe will be called with
    descriptors 0 and 1 being the same socket, but not always...

Wow, talk about obscure use cases!  :-)

Yeah, I can see where someone might want to do that. OK, never
mind, I never claimed it was a particularly good idea....

Thanks,
Bill