tcp ports ftp hangs in CLOSE_WAIT state with NMAP scanner

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  • 1. Region allocation and tasks under vxworks-memory mgmnt query
    dear all, I read in psos document that dynamically requesting for regions are possible and also one thing which i could not understand is its given in psos manual (unaware of vxworks!!!) that the task requested the region is not the owner of it and it can pass segments and regions allocated(which is returned after region/segment creation/request call)across tasks.so my query is,the how is memory protection done?and for that case since theres no owner ship of regions as mentioned in manual of psos,then how is safety ensured when a task requesting region and once its given ,its used simultanously by other tasks and how racing is prevented?I have no documents relating to mgmnt of vxworks memory,but psos is available and i could not come to a conclusion of how this is possible? It will be helpful if some one could help me understand how this is implemented both in psos as well as vxworks. I have both psos/vxworks in our co and i am dealing with both and i have following environments: vxworks: windows 2k host/vxworks 5.4,tornado2.0,x86 target board. psos: prism+1.2,psos2.2.7,windows98 host,x86 target board. advanced thanks for all your replies, regards, s.subbarayan
  • 2. regarding PowerPC
    Dear All, We are using PMC module on PowerPC,in Intel we will use sysMumMapAdd to map the physical memory to virtual memory,such mapping is required for PowerPC,if so, should I do the same thing for PowerPc? or should i use any other function to do the same. Thanks and regards Rajesh
  • 3. about zbufSockBufSend
    There is following depiction In Chapter7.3, Zbuf Sockets of VxWorks Network Programmer's Guide: " The zbuf socket calls are particularly useful when large data transfer is a significant part of your socket application. For example, many socket applications contain sections of code like the following fragment: pBuffer = malloc (BUFLEN); while ((readLen = read (fdDevice, pBuffer, BUFLEN)) > 0) write (fdSock, pBuffer, readLen); You can eliminate the overhead of copying from the application buffer pBuffer into the internal socket buffers by changing the code to use zbuf socket calls. " I wonder what scale of the data can be called "large". Errors occurred when I called zbufSockBufSend(s, buf, len, (VOIDFUNCPTR)freeCallback, 0, 0)) where parameter len is larger than the default size of a socket(8192 Bytes), No error happened when I called send() to send data larger than 8192 Bytes or zbufSockBufSend() to send data less than 8192 Bytes. In one of my earlier program,I use send() to send data of 1K Bytes.And I found that it takes cpu 53 us to executes send() (packing TCP package, copying data into socket buffers...), I want to call zbufSockBufSend() instead to reduce the cpu time, but it seems useless. The cpu time didn't decrease. I want to know more about zbuf, when it works usefully? And how I can reduce the cpu time of sending data through a TCP socket? Thanks ZhuHaitao
  • 4. memory management and vxworks
    Dear gurus, Have any one got any document or know how vxworks manages memory?Basically i am looking for something like region and buffer allocation algorithms present in psos.I have searched all the vxworks manual supplied but could not get this info. can anyone point me to this document also let me know,what memory related calls are offered in vxworks?in psos we have getreg,setreg,getsegment like this.I am looking for similar calls here also.i.e to get a region,segment,buffer etc. advanced thanks to all ur replies, Regards, s.subbarayan

tcp ports ftp hangs in CLOSE_WAIT state with NMAP scanner

Postby lstrong » Sun, 11 Mar 2007 02:58:49 GMT

I have been using NMAP to scan all the open ports on my equipment
which runs VxWorks Version 5.3.1. The scanner some times causes hung
CLOSE_WAITS on the FTP port 21.
Eventually after 8 such CLOSE_WAIT connections, FTP server hangs.

I came across this posting:
 http://www.**--****.com/ %2Fgroup%2Fcomp.os.vxworks%2Fbrowse_frm%2Fthread%2Fb372bdd8faafe028%2F9d5ba83a4c9a769c%3Fhl%3Den%26#doc_f07a1f9ffd8b886c

I'm seeing the same problem with my FTP server too. Whenever I run
NMAP to
scan the ports, my FTP server hangs with 8 connections in CLOSE_WAIT
state.

I could not find the fix for this problem.

If you have come across the same problem or know the fix for this
problem please let me know.

Thanks in advance.


Re: tcp ports ftp hangs in CLOSE_WAIT state with NMAP scanner

Postby Bill Pringlemeir » Sun, 11 Mar 2007 07:36:08 GMT





You can reproduce the same thing on Linux, etc.  However the amount of
connections would likely be higher.  If NMAP (or anything) cause a
hanging CLOSE state, the TCP rfc say that this should remain in the
CLOSE_WAIT state for six hours or something insane like that.

You can increase the amount of sockets available.  There might also be
a "CLOSE_WAIT" timer variable that can be changed to not wait for the
full close handshaking.  I think that Windows might also perform a
truncated CLOSE sequence.

fwiw,
Bill Pringlemeir.

-- 
My cousin is an agoraphobic {*filter*}, which makes it kind of hard
for him to come out of the closet. - Bill Kelly
 
vxWorks FAQ, " http://www.**--****.com/ ~borkhuis/vxworks/vxworks.html"

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