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9cca8dfc0b
Commit 8706c8131 ("BUG/MEDIUM: mux_pt: Always set CS_FL_RCV_MORE.")
was a bit excessive in setting this flag, it refrained from removing
it after read0 unless it was on an empty call. The problem it causes
is that read0 is thus ignored on the first call :
$ strace -tts200 -e trace=recvfrom,epoll_wait,sendto ./haproxy -db -f tcp.cfg
06:34:23.956897 recvfrom(9, "blah\n", 15360, 0, NULL, NULL) = 5
06:34:23.956938 recvfrom(9, "", 15355, 0, NULL, NULL) = 0
06:34:23.956958 recvfrom(9, "", 15355, 0, NULL, NULL) = 0
06:34:23.957033 sendto(8, "blah\n", 5, MSG_DONTWAIT|MSG_NOSIGNAL, NULL, 0) = 5
06:34:23.957229 epoll_wait(3, [{EPOLLIN|EPOLLHUP|EPOLLRDHUP, {u32=8, u64=8}}], 200, 0) = 1
06:34:23.957297 recvfrom(8, "", 15360, 0, NULL, NULL) = 0
If CO_FL_SOCK_RD_SH is reported by the transport layer, it indicates the
read0 was already seen thus we must not try again and we must immedaitely
report it. The simple fix consists in removing the test on ret==0 :
$ strace -tts200 -e trace=recvfrom,epoll_wait,sendto ./haproxy -db -f tcp.cfg
06:44:21.634835 recvfrom(9, "blah\n", 15360, 0, NULL, NULL) = 5
06:44:21.635020 recvfrom(9, "", 15355, 0, NULL, NULL) = 0
06:44:21.635056 sendto(8, "blah\n", 5, MSG_DONTWAIT|MSG_NOSIGNAL, NULL, 0) = 5
06:44:21.635269 epoll_wait(3, [{EPOLLIN|EPOLLHUP|EPOLLRDHUP, {u32=8, u64=8}}], 200, 0) = 1
06:44:21.635330 recvfrom(8, "", 15360, 0, NULL, NULL) = 0
The issue is minor, it only results in extra syscalls and CPU usage.
This fix should be backported to 2.0 and 1.9.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)