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Since the introduction of speculative I/O, it was not always possible to correctly detect a connection establishment. Particularly, in TCP mode, there is no data to send and getsockopt() returns no error. The solution consists in trying a connect() again to get its diagnostic.
29 lines
1.2 KiB
Plaintext
29 lines
1.2 KiB
Plaintext
Normally, we should use getsockopt(fd, SOL_SOCKET, SO_ERROR) on a pending
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connect() to detect whether the connection correctly established or not.
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Unfortunately, getsockopt() does not report the status of a pending connection,
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which means that it returns 0 if the connection is still pending. This has to
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be expected, because as the name implies it, it only returns errors.
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With the speculative I/O, a new problem was introduced : if we pretend the
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socket was indicated as ready and we go to the socket's write() function,
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a pending connection will then inevitably be identified as established.
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In fact, there are solutions to this issue :
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- send() returns -EAGAIN if it cannot write, so that as long as there are
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pending data in the buffer, we'll be informed about the status of the
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connection
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- connect() on an already pending connection will return -1 with errno set to
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one of the following values :
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- EALREADY : connection already in progress
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- EISCONN : connection already established
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- anything else will indicate an error.
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=> So instead of using getsockopt() on a pending connection with no data, we
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will switch to connect(). This implies that the connection address must be
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known within the socket's write() function.
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