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QuestionLooking to figure out how to design a desktop and theme for an operating system based off of Linux. Can anyone point me in the right direction on how to do this? Anyone know of any books? Any tips? Any pointers? Any Forums? etc. The other parts are a Pin
justinsloan3217-May-19 22:18
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AnswerRe: Looking to figure out how to design a desktop and theme for an operating system based off of Linux. Can anyone point me in the right direction on how to do this? Anyone know of any books? Any tips? Any pointers? Any Forums? etc. The other parts a Pin
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QuestionPARTIALLY SOLVED hcitool scan with grep pipe Pin
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QuestionHow to retrieve "terminal" output? Pin
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QuestionMessage Removed Pin
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QuestionTheoretical server/site setup Pin
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QuestionSOLVED "configure" script option PKG_CONFIG_DEBUG_SPEW fails to run on X86 Pin
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QuestionMessage Closed Pin
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Questionmissing mount.pc Pin
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QuestionBad UDP length 736 > IP payload length Len = 728 packet drop Pin
sarali8-Apr-19 18:35
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AnswerRe: Bad UDP length 736 > IP payload length Len = 728 packet drop Pin
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AnswerRe: Bad UDP length 736 > IP payload length Len = 728 packet drop Pin
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GeneralRe: Bad UDP length 736 > IP payload length Len = 728 packet drop Pin
sarali12-Apr-19 20:43
membersarali12-Apr-19 20:43 
Hi,

I tied to print the packet length calculation in my program before sending it out.
I think the UDP payload length and IP length length calculation looks fine.

APP: INFO: ip header checksum:f9b9 udp checksumBlush | :O size_udp:736 sizeof(struct udp_hdr):8,size_ApplMsg:728udphdr->dgram_len:57346 m->data_len:770 size_ip:756 l2_data_shift:14

Further I am able to transfer UDP packets of size 20bytes,40 bytes using the same program.No issues observed.So right now I do not suspect the program. But I donot understand why the wireshark says "Bad UDP payload length". Not sure how the packet length can go wrong.Whether UDP packet is hardware offloaded ? We may be dropping the packet at the Kernel level due to this bad UDP length. So I tried to increase the UDP buffer size in kernel but of no use.
The netstat -su output shows 0 send/receive buffer errors.

[root@ATCAC06_100 /]# netstat -su
IcmpMsg:
InType0: 233961
InType3: 213187
InType8: 14
OutType0: 14
OutType3: 213187
OutType8: 17
OutType69: 233944
Udp:
592800 packets received
1439 packets to unknown port received.
0 packet receive errors
501661 packets sent
0 receive buffer errors
0 send buffer errors
UdpLite:
IpExt:


In my program I am trying to read the return value of "recvFrom" call is -1 and in that case I tried to print the strerror(errno).
But I could get prints only for the successful case ( return value > 0) and not for unsuccessful case.So mostly the packet is getting dropped at the Kernel level but how do I confirm this.Any debugging steps please share. I am using DPDK 18.08 version( on RHEL 7.6 platform) for packet forwarding.Please suggest how to resolve this issue.

modified 19-Apr-19 14:47pm.

GeneralRe: Bad UDP length 736 > IP payload length Len = 728 packet drop Pin
Randor 28-Apr-19 12:50
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GeneralRe: Bad UDP length 736 > IP payload length Len = 728 packet drop Pin
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