wrong checksum

Question

wrong checksum

MVIStank opened this issue 6 years ago · comments

I am running test pcap.
Create profile -> Import Pcap -> Select pcap ( cap2/http_browsing) -> Import
I am sniffing traffic in my DUT:
22.0.0.3.80 > 21.0.0.3.36989: Flags [P.], cksum 0x6d93 (correct), seq 1461:2921, ack 250, win 32768, length 1460: HTTP
01:45:14.755614 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 128, id 10243, offset 0, flags [none], proto TCP (6), length 40)
21.0.0.3.36989 > 22.0.0.3.80: Flags [.], cksum 0xa9d7 (correct), ack 2921, win 32768, length 0
01:45:14.755625 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 1518: (tos 0x0, ttl 126, id 10252, offset 0, flags [none], proto TCP (6), length 1500)
that's ok.
If I import pcap and replace src and dsr IP

then I see in my snif:
02:45:52.218656 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 128, id 10240, offset 0, flags [none], proto TCP (6), length 44, bad cksum e7c6 (->f4ac)!)
20.20.0.1.36989 > 10.10.0.1.80: Flags [S], cksum 0xcfc5 (incorrect -> 0xdcab), seq 2664033731, win 32768, options [mss 1460], length 0
02:45:52.218780 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 126, id 10249, offset 0, flags [none], proto TCP (6), length 44, bad cksum e9bd (->f6a3)!)
10.10.0.1.80 > 20.20.0.1.36989: Flags [S.], cksum 0x9e7b (incorrect -> 0xab61), seq 2664075886, ack 2664033732, win 32768, options [mss 1460], length 0

Did not help option --checksum-disable..
What am i doing wrong?
GUI -4.5.3
Trex - 2.5.3

Egor Blagov · Answer 1 · Wed Feb 20 2019 19:10:00 GMT+0800 (China Standard Time)

Looks like an issue, I'll address that ср, 20 февр. 2019 г. в 16:03, MVIStank <notifications@github.com>:

…

I am running test pcap. Create profile -> Import Pcap -> Select pcap ( cap2/http_browsing) -> Import I am sniffing traffic in my DUT: 22.0.0.3.80 > 21.0.0.3.36989: Flags [P.], cksum 0x6d93 (correct), seq 1461:2921, ack 250, win 32768, length 1460: HTTP 01:45:14.755614 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 128, id 10243, offset 0, flags [none], proto TCP (6), length 40) 21.0.0.3.36989 > 22.0.0.3.80: Flags [.], cksum 0xa9d7 (correct), ack 2921, win 32768, length 0 01:45:14.755625 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 1518: (tos 0x0, ttl 126, id 10252, offset 0, flags [none], proto TCP (6), length 1500) that's ok. If I import pcap and replace src and dsr IP [image: eee] <https://user-images.githubusercontent.com/38526613/53078078-fb701700-3525-11e9-97c9-90cf57a44c26.jpeg> then I see in my snif: 02:45:52.218656 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 128, id 10240, offset 0, flags [none], proto TCP (6), length 44, *bad cksum e7c6 (->f4ac)!)* 20.20.0.1.36989 > 10.10.0.1.80: Flags [S], cksum 0xcfc5 (incorrect -> 0xdcab), seq 2664033731, win 32768, options [mss 1460], length 0 02:45:52.218780 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 126, id 10249, offset 0, flags [none], proto TCP (6), length 44, *bad cksum e9bd (->f6a3)!)* 10.10.0.1.80 > 20.20.0.1.36989: Flags [S.], cksum 0x9e7b (incorrect -> 0xab61), seq 2664075886, ack 2664033732, win 32768, options [mss 1460], length 0 Did not help option --checksum-disable.. What I'm doing wrong? GUI -4.5.3 Trex - 2.5.3 — You are receiving this because you are subscribed to this thread. Reply to this email directly, view it on GitHub <#108>, or mute the thread <https://github.com/notifications/unsubscribe-auth/Aho7jYh5eOZrxKVUnCkm7xeYYtwnK--Mks5vPQ94gaJpZM4bEuoJ> .

-- *Egor Blagov* <https://www.xored.com> Software engineer at Xored Software Inc. Mobile: +7 (923) 190 2319 <//+7-923-190-2319> | Skype: i_am_union | Email: egor.blagov@xored.com

Egor Blagov · Answer 2 · Fri Feb 22 2019 00:43:19 GMT+0800 (China Standard Time)

Hi, @MVIStank

Please check our latest release, it should work fine:
https://github.com/cisco-system-traffic-generator/trex-stateless-gui/releases/tag/v4.5.4

Thanks & regards,
Egor

MVIStank · Answer 3 · Mon Feb 25 2019 17:01:41 GMT+0800 (China Standard Time)

I've checked in version 4.5.4
Unfortunately, checksum is bad.

03:15:01.443090 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), l6), length 44) 10.10.0.2.80 > 20.20.20.2.36989: Flags [S.], cksum 0x9e7b (incorrect -> 0x975f), seq 2664075886, ack 2664033732, win 32768, options [mss 1460], length 0 03:15:01.470143 90:e2:ba:df:23:c0 > a8:f9:4b:ac:43:2a, ethertype IPv4 (0x0800), length 64: (tos 0x0, ttl 128, id 10241, offset 0, flags [none], proto TCP (6), length 40) 20.20.20.2.36989 > 10.10.0.2.80: Flags [.], cksum 0xb638 (incorrect -> 0xaf1c), ack 1, win 32768, length 0

Egor Blagov · Answer 4 · Mon Feb 25 2019 17:14:29 GMT+0800 (China Standard Time)

Hi,

Please, could you attach the pcap that you use, I'll debug it.

Thanks & regards
Egor.

MVIStank · Answer 5 · Mon Feb 25 2019 17:26:32 GMT+0800 (China Standard Time)

This's default pcap file with folder /cap2

http_browsing.pcap.zip

Egor Blagov · Answer 6 · Wed May 15 2019 21:51:04 GMT+0800 (China Standard Time)

Hi, @MVIStank

Sorry for delay, I thought that's the issue was related to ipv4 checksum, now it's fixed for both TCP/UDP layers. Please validate with v4.5.5

Zeus100 · Answer 7 · Wed Jul 29 2020 04:45:28 GMT+0800 (China Standard Time)

Seeing same issue in v4.5.6.

Tried with both TCP and UDP profile. Altough I am not importing any PCAP but creating a traffic profile using GUI, not seeing issue when running from CLI.

Egor Blagov · Answer 8 · Wed Jul 29 2020 18:28:37 GMT+0800 (China Standard Time)

@zeus10000 pls share me CLI traffic profile you use, and GUI profile you use