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Subject: [libssh2] Non-blocking vs. default mode

[libssh2] Non-blocking vs. default mode

From: James Housley <jim_at_thehousleys.net>
Date: Sun, 22 Apr 2007 09:55:32 -0400

The new code in sftp.c gets the current blocking state of libssh2 to
restore it afterwards, then sets the state to what is desired.
However, libssh2_sftp_read() will set the blocking state to 1, do
it's business and then restore the state (probably to 0). Since the
blocking/non-blocking state is setup before it is passed to libssh2,
libssh2 doesn't know what the current state is.

We can require all new programs to explicitly call
libssh2_channel_set_blocking() to ensure libssh2 knows the proper
state of the socket. But existing program my show strange behavior.
What I would like to add is a routine that is always called from
within libssh2_channel_open_session() so the libssh2 blocking
variable can be set to the same as the socket. I have started to
modify _libssh2_nonblock(), but have limited access to other systems,
so a lot default to blocking = 1.

This is the code I would like to add:

/*
  * _libssh2_get_socket_blocking() gets the given blocking or non-
blocking
  * state of the socket.
  */
static int _libssh2_get_socket_blocking(int sockfd) /* operate on
this */
{
#undef SETBLOCK
#define SETBLOCK 0
#ifdef HAVE_O_NONBLOCK
     /* most recent unix versions */
     int flags;

     if ((flags = fcntl(sockfd, F_GETFL, 0)) == -1) {
         /* Assume blocking on error */
         return 1;
     }
     return (flags & O_NONBLOCK);
#undef SETBLOCK
#define SETBLOCK 1
#endif

#if 0
#if defined(HAVE_FIONBIO) && (SETBLOCK == 0)
     /* older unix versions */
     int flags;

     flags = nonblock;
     return ioctl(sockfd, FIONBIO, &flags);
#undef SETBLOCK
#define SETBLOCK 2
#endif

#if defined(HAVE_IOCTLSOCKET) && (SETBLOCK == 0)
     /* Windows? */
     unsigned long flags;
     flags = nonblock;

     return ioctlsocket(sockfd, FIONBIO, &flags);
#undef SETBLOCK
#define SETBLOCK 3
#endif

#if defined(HAVE_IOCTLSOCKET_CASE) && (SETBLOCK == 0)
     /* presumably for Amiga */
     return IoctlSocket(sockfd, FIONBIO, (long)nonblock);
#undef SETBLOCK
#define SETBLOCK 4
#endif

#if defined(HAVE_SO_NONBLOCK) && (SETBLOCK == 0)
     /* BeOS */
     long b = nonblock ? 1 : 0;
     return setsockopt(sockfd, SOL_SOCKET, SO_NONBLOCK, &b, sizeof(b));
#undef SETBLOCK
#define SETBLOCK 5
#endif
#endif /* 0 */

#ifdef HAVE_DISABLED_NONBLOCKING
     return 1; /* returns blocking */
#undef SETBLOCK
#define SETBLOCK 6
#endif

#if (SETBLOCK == 0)
#error "no non-blocking method was found/used/get"
#endif
}

And then add to libssh2_channel_open_ex()

@@ -226,6 +295,8 @@
         channel->remote.window_size = window_size;
         channel->remote.window_size_initial = window_size;
         channel->remote.packet_size = packet_size;
+
+ channel->blocking = _libssh2_get_socket_blocking(session-
>socket_fd);
         libssh2_channel_add(session, channel);

Jim

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Received on 2007-04-22

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