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UDP packet dropped by kernel

Posted by M_JRIBI 
UDP packet dropped by kernel
February 01, 2017 06:08AM
Hi,
There's this problem that I am facing with linux kernel 2.6.32. The issue arises randomly also on load condition. I have an Network application which sends and receive the UDP packets. At some instant it is observed that the packet which I send are dropped by kernel and sendto API return me an error as EPERM.
After digging dipper i found that the kernel drops these packets when it tires to confirm the nf_conntack entries (nf_conntack_confirm). Now I still went into detailing of it and found that the problem is within the API __nf_contrack_confirm, in this it actually checks whether the nf_conntrack entries which my sk_buff holds is available in conntrack hash table and it say ooops its present hence discard these packet.

Going step further I had also determine that __nf_contrack_confirm fails when it compares the DIR_ORIGINAL entry in hash table.


I did determine that the conntrack entires of sk_buff is alter by nat hooks. But then it only modifies the DIR_REPLY entries. So there could be still some part of kernel which modifies the entries which i am missing. Or else it could be that my understanding(direction of looking at problem) is getting wrong.

I request all the members if you have any observation/review regarding the same problem the please guide me.



Edited 1 time(s). Last edit at 02/01/2017 06:13AM by M_JRIBI.
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