Implement read_ahead option (OTP-19199)
#8785
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I saw a strange behaviour of the MGS_PEEK flag on Linux (Ubuntu 22.04 LTS). When using MSG_PEEK through `socket` to try to avoid concatenating the header and body binaries, instead peek the header then receive the whole packet, this happened (header 2, incoming <<0,1,65>>, but one character at the time, through `gen_tcp_echo_SUITE`'s slow echo server: * recv 0 -> select ... * recv 0 -> <<0>> We are missing one byte for the header and try to peek it * recv 1 peek -> timeout * recv 1 -> select ... New attempt to peek the header * recv 1 peek -> <<1>> We conclude the length field is 1 and we are missing 2 bytes * recv 2 -> select ... Here we don't save the state that we want 2 bytes so we start over with the <<0>> we have and, again, peek for the rest of the header. * recv 1 peek -> <<1,0>> ??? we asked for 1 byte, what is the <<0>>? Here the packet decode succeeds surprisingly since we were supposed to only have the header, so we fall back to the generic path which receives one byte at the time. * recv 1 -> <<65>> ??? where did the <<1>> go? * recv 65 -> select ... We are lost and think the length field is 65= recv N peek means `socket:recv(_, N, [peek], 0)` (timeout 0). We didn't store data from a peek, just use it to figure out the packet length for a recv without peek.
CT Test Results 2 files 70 suites 1h 6m 49s ⏱️ For more details on these failures, see this check. Results for commit 0e943f4. ♻️ This comment has been updated with latest results. To speed up review, make sure that you have read Contributing to Erlang/OTP and that all checks pass. See the TESTING and DEVELOPMENT HowTo guides for details about how to run test locally. Artifacts// Erlang/OTP Github Action Bot |
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Continuation of PR #8690 that implements the
read_aheadoption ininet:setopts/2, that is; also forinet_backend=socket(gen_tcp_socket), with documentation, and test cases.