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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 12:18:05 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-13 12:18:05 +0000
commitb46aad6df449445a9fc4aa7b32bd40005438e3f7 (patch)
tree751aa858ca01f35de800164516b298887382919d /doc/internals/connect-status.txt
parentInitial commit. (diff)
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Adding upstream version 2.9.5.upstream/2.9.5
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+Normally, we should use getsockopt(fd, SOL_SOCKET, SO_ERROR) on a pending
+connect() to detect whether the connection correctly established or not.
+
+Unfortunately, getsockopt() does not report the status of a pending connection,
+which means that it returns 0 if the connection is still pending. This has to
+be expected, because as the name implies it, it only returns errors.
+
+With the speculative I/O, a new problem was introduced : if we pretend the
+socket was indicated as ready and we go to the socket's write() function,
+a pending connection will then inevitably be identified as established.
+
+In fact, there are solutions to this issue :
+
+ - send() returns -EAGAIN if it cannot write, so that as long as there are
+ pending data in the buffer, we'll be informed about the status of the
+ connection
+
+ - connect() on an already pending connection will return -1 with errno set to
+ one of the following values :
+ - EALREADY : connection already in progress
+ - EISCONN : connection already established
+ - anything else will indicate an error.
+
+=> So instead of using getsockopt() on a pending connection with no data, we
+ will switch to connect(). This implies that the connection address must be
+ known within the socket's write() function.
+
+