Re: [libvirt] [PATCH 06/10] Add a generic internal API for handling any FD based stream
On 11/02/2010 05:42 AM, Daniel P. Berrange wrote:
>> - VIR_FROM_AUDIT /* Error from auditing subsystem */
>> + VIR_FROM_AUDIT, /* Error from auditing subsystem */
>> + VIR_FROM_STREAMS, /* Error from I/O streams */
>> } virErrorDomain;
>
> Is the switch from C89 style (no trailing comma) to the C99 style
> (optional trailing comma permitted) intentional? Personally, I like it,
> since adding a new value at the end no longer requires a random-looking
> diff of the previous entry just to add a comma.
IMHO, leaving off the comma needlessly enlarges future patches
because 2 lines have to be changed to add an entry instead
of just one.
Sounds like we're in violent agreement here, about favoring C99 syntax.
Is it worth a generic cleanup patch for other enum declarations that
don't yet use trailing commas, or should we just save it for an
as-encountered basis?
>> +#include <sys/un.h>
>
> but this is missing on Mingw, with no gnulib replacement as of yet. Do
> we need to add some HAVE_SYS_UN_H checks?
Yes, i guess so.
>
>> +#include <netinet/in.h>
>> +#include <netinet/tcp.h>
>
> Likewise for HAVE_NETINET_TCP_H.
Doesn't gnulib take care of TCP socket portability for us ?
So far, gnulib provides <netinet/in.h>, but not <netinet/tcp.h>. But
what exactly are we using that's only in netinet/tcp.h? It may be easy
to port to gnulib, since mingw does have tcp support (sys/un.h is the
much harder task, since mingw has no notion of unix sockets).
>> +static int virFDStreamWrite(virStreamPtr st, const char
*bytes, size_t nbytes)
>
> Should this return ssize_t...
No, this has to return an int, to match the public API calling
convention.
Then we have to check for overflow, and explicitly return an error if
nbytes > INT_MAX.
>> + if ((st->flags & VIR_STREAM_NONBLOCK) &&
>> + (!S_ISCHR(sb.st_mode) &&
>> + !S_ISFIFO(sb.st_mode))) {
>
> Should we also permit S_ISSOCK as an fd that supports reliable
> non-blocking behavior?
AFAIK, there's no way to open a socket as a path on the
filesystem is there ? So there'd be no way that open(path)
could return an FD for which S_ISSOCK() is true.
You're probably right that it's not possible to bind a socket to a
standard file system. But it is possible via procfs (think
/proc/nnn/fd/nnn of a process which already has a socket open), and
there might also be some magic /dev/ or /sys/ mappings that can provide
a socket (at any rate, bash provides magic handling of
/dev/tcp/host/port, whether or not the kernel also has a magic
filesystem to provide that support automatically). So it boils down to
a question of whether we want to permit or reject sockets, on the
pre-condition that the user finds a way to hand us a filename that
resolves to a socket.
--
Eric Blake eblake(a)redhat.com +1-801-349-2682
Libvirt virtualization library http://libvirt.org
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