[erlang-questions] R13B02 on 8/16 core box: all TCP communication hangs/frozen

Per Hedeland <>
Fri Nov 20 21:54:12 CET 2009


Luke Gorrie <> wrote:
>
>The SYN_RECV sockets make me curious. Linux seems to have a second
>backlog queue for when the normal one fills up. Connections in this
>queue seem to send a SYN+ACK (because the client reaches ESTABLISHED)
>but wait in SYN_RECV. The code in net/ipv4/tcp_ipv4.c's
>tcp_v4_conn_request refers to this as a "syn queue" containing "warm
>entries", but I haven't dug deep enough to see how it really works.
>Does anyone know? (Per Hedeland? :-))

Sorry Luke, I'm losing touch with the Linux kernel internals these days
(though I don't really mean that I'm sorry about that:-). Up until what
you wrote in this paragraph, I was assuming that you were seeing
syncookies in action, and that they were now enabled by default on
Linux, and you just didn't realize it (they are on FreeBSD - they even
have their own man page!:-). But I guess not...

--Per


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