lwIP - A Lightweight TCP/IP stack - Bugs: bug #20075, A problem with keep-alive timer...
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bug #20075: A problem with keep-alive timer and TCP flags
Submitter: | Srinivas Gollakota <gollakota> | ||
Submitted: | Mon 04 Jun 2007 08:49:13 PM UTC | ||
Category: | TCP | Severity: | 3 - Normal |
Item Group: | Faulty Behaviour | Status: | Fixed |
Privacy: | Public | Assigned to: | fbernon |
Open/Closed: | Closed | Planned Release: | None |
lwIP version: | None |
Jump to the original submission
Fri 04 Apr 2008 05:12:40 PM UTC, comment #7: |
Oleg Tyshev <olegreen> |
Mon 11 Jun 2007 01:54:39 PM UTC, comment #6:
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Frédéric Bernon <fbernon> |
Mon 11 Jun 2007 01:45:52 PM UTC, comment #5: Patch file for Srinivas & Oleg if they want to test it...
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Frédéric Bernon <fbernon> |
Mon 11 Jun 2007 01:35:55 PM UTC, comment #4: I have set in tcp_keepalive a TCPH_FLAGS_SET(tcphdr, 0);
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Frédéric Bernon <fbernon> |
Mon 11 Jun 2007 09:31:58 AM UTC, comment #3: In http://www.freesoft.org/CIE/RFC/1122/114.htm, there is no lot of information about TCP header flags.
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Frédéric Bernon <fbernon> |
Wed 06 Jun 2007 10:10:02 AM UTC, comment #2: I think keep-alive packets should not send ACK flag.
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Oleg Tyshev <olegreen> |
Tue 05 Jun 2007 07:39:37 AM UTC, comment #1: Looks like a bug to me, and a correct diagnosis and suggested fix. Thanks.
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Kieran Mansley <kieranm> |
Mon 04 Jun 2007 08:49:13 PM UTC, original submission:
Hello,
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Srinivas Gollakota <gollakota> |
Depends on the following items: None found
Items that depend on this one: None found
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Follow 6 latest changes.
Date | Changed by | Updated Field | Previous Value | => | Replaced by |
---|---|---|---|---|---|
2007-06-11 | fbernon | Status | Confirmed | Fixed | |
Open/Closed | Open | Closed | |||
2007-06-11 | fbernon | Attached File | - | Added tcp_out.c.patch, #13013 | |
Status | None | Confirmed | |||
Assigned to | None | fbernon | |||
2007-06-11 | fbernon | Attached File | - | Added KeepAlive.cap, #13012 |
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Corresponding source code
I have tested lwip keep-alive again.
Shrinivas suggested to send ACK and it was right.
At least Windows XP does not send [TCP Keep-Alive ACK] in reply to [TCP Keep-Alive] packets if [TCP Keep-Alive] packet does not have ACK flag.
And without reply after 9 try connection is broken.
If we see once more
4.2.3.6 TCP Keep-Alives http://www.freesoft.org/CIE/RFC/1122/114.htm
"It is extremely important to remember that ACK segments that contain no data are not reliably transmitted by TCP."
It means indirect, that Keep-Alive packets should have ACK flag.