/proc/net/tcp not updated fast enough?

From: Henrik Christian Grove (grove_at_fsr.ku.dk)
Date: 10/27/04

  • Next message: Florian Schmidt: "Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0" 
    To: linux-kernel@vger.kernel.org
Date:	27 Oct 2004 12:21:07 +0200

    Hi

    I'm writing a SMTP proxy that needs to know the uid of the user
    connecting (only connections from the same machine is supposed to work).

    I find the uid by searching /proc/net/tcp, for a line having a
    0100007F:<port I get from accept on the socket I listen on> as
    local_address and <any-ip>:<the port I listen on> as rem_address, and
    that works perfectly -- most of the time.

    I have it running on 11[1] machines and since midnight (it's 11:47 here
    now) I have 2397 succesfull connections, but in 31 cases (that's 1,29%
    of the connections - and thus not totally ignorable) I had to read
    through /proc/net/tcp twice to find the uid. Does that sound plausible,
    or more like I'm doing something wrong?

    If it's plausible, how long can it take for /proc/net/tcp to get the
    info? I'm asking because I see one connection (again since midnight)
    where I don't find any uid in the 5 attempts I do as a max.

    If it's plausible could it explain why I have 9 connections apparently
    coming from root, although they seem to come from a program _not_
    running as root? Here "seem" means that I have tried logging the
    (relevant parts of the) output from `netstat -tnp` when I got these
    connections and the pid was the pid of a program I've written myself,
    that would complain in the log if it were running as root.
    (There's also a single connection from uid 33 (that's a uid apache runs
    as) and one from uid 99 (unused), but they are so rare I haven't tried
    tracing them yet).

    It wasn't until yesterday that I started suspecting /proc/net/tcp from
    "lagging", so I don't have reliable numbers from yesterday.

    The machines run a 2.4.25 kernel with vserver-patches (the proxy
    actually runs in a vserver).

    .Henrik

    [1] Actually one of them has only been running since around 4:45 this
    morning, but that shouldn't matter. 

    -- 
"Det er fundamentalt noget humanistisk vås, at der er noget, 
 der hedder blød matematik."
   --- citat Henrik Jeppesen, dekan for det naturvidenskabelige fakultet
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/
  • Next message: Florian Schmidt: "Re: [patch] Real-Time Preemption, -RT-2.6.9-mm1-V0"

    Relevant Pages

    • Re: Moving from java to python.
      ... I have recently been learning python, ... [uid - an identifier for comparisons.] ... for i in connections: ... def getConnected: ...
      (comp.lang.python)
    • Re: Moving from java to python.
      ... I have recently been learning python, ... [uid - an identifier for comparisons.] ... for i in connections: ... def getConnected: ...
      (comp.lang.python)
    • Moving from java to python.
      ... I have recently been learning python, ... [uid - an identifier for comparisons.] ... for i in connections: ... def getConnected: ...
      (comp.lang.python)
    • Re: Moving from java to python.
      ... > for i in connections: ... > if not uid: ... the need for anything other than the idis suspect. ... > def getConnected: ...
      (comp.lang.python)