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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 09:35:11 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-28 09:35:11 +0000 |
commit | da76459dc21b5af2449af2d36eb95226cb186ce2 (patch) | |
tree | 542ebb3c1e796fac2742495b8437331727bbbfa0 /doc/internals/connect-status.txt | |
parent | Initial commit. (diff) | |
download | haproxy-upstream.tar.xz haproxy-upstream.zip |
Adding upstream version 2.6.12.upstream/2.6.12upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'doc/internals/connect-status.txt')
-rw-r--r-- | doc/internals/connect-status.txt | 28 |
1 files changed, 28 insertions, 0 deletions
diff --git a/doc/internals/connect-status.txt b/doc/internals/connect-status.txt new file mode 100644 index 0000000..70bbcc5 --- /dev/null +++ b/doc/internals/connect-status.txt @@ -0,0 +1,28 @@ +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. + + |