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SubjectRe: PROBLEM: Sending mail-attachment > 45k with Netscape via sendmail hangs
Date
Hello,

I can reproduce the stall using the code posted
by Matthias Moeller on 2.2.2-ac5, compiled with
egcs 1.1.1 running on uniprocessor PPro 166 MHz.
I was not able to reproduce it on stock 2.2.1,
but I did not try very extensively.

I have done some research on the WRITE_SIZE,
READ_SIZE and number of loops (3200 in
the original code). It does not seem to
be a race - there is a clear pattern
that seems to be deterministic. Fiddling
with tcp_sack does not change anything.

Perhaps somebody familiar with the used
algorhitms can interpret the pattern. I am
willing to test any experimental patches.


1) Server: WRITE_SIZE 1585, LOOPS 3200
Client: varying READ_SIZE
The stall occurs when READ_SIZE <= 956

2) Client: READ_SIZE 956
Server: WRITE_SIZE 1585, varying LOOPS
The stall occurs when LOOPS >= 45

3) Client: READ_SIZE 956
Server: LOOPS 45, varying WRITE_SIZE
The stall occurs, if
WRITE_SIZE >= 1480 && <= 1505
or
WRITE_SIZE >= 1554 (+74) && <= 1585 (+80)
or
WRITE_SIZE >= 1636 (+82) && <= 1673 (+88)
or
WRITE_SIZE >= 1727 (+91) && <= 1771 (+98)


Some more numbers for stalling cases:

WRITE_SIZE LOOPS READ_SIZE bytes read Send-Q
succesfully

---
1480 50 956 29600 39960
1481 50 956 29620 (+20) 39987 (+27)
1482 50 956 29640 40014
...
1488 50 956 29780 40203
1490 50 956 29800 38740
1491 50 956 29820 38766 (+26)
1492 50 956 29840 38792 (+26)
...
1505 50 956 30100 39130
---
1554 50 956 29526 38850
1555 50 956 29545 (+19) 38875 (+25)
1556 50 956 29564 38900
...
1585 50 956 30115 39625
---
1636 50 956 29448 39264
1637 50 956 29466 (+18) 39288 (+24)
...
1673 50 956 30114 40152
---
1727 50 956 29359 39721
1728 50 956 29376 (+17) 39744 (+23)
...
1771 50 956 30107 38962


Regards
--
Stano


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