hi, On 9/8/19 1:29 AM, Samuel Thibault wrote: >> 16:49:39.430959 IP 10.0.2.2.33294 > 10.0.2.15.19003: UDP, bad length 9000 > >> 1472 > > tcpdump seems to be showing dumb output here. The packet is fragmented > by slirp, which makes tcpdump confused and show only the first > fragment. If you let tcpdump print everything, you will see the other > fragments. In reality, everything is going fine here.
oh ok. for some reason the receiving process is not happy with these packets anyway. thanks for the hint, i'll have to look into that deeper then. >> #define IF_MRU 9000 >> >> but the resulting qemu-system-x86_64 binary did not behave differently. > > Did you explicitly remove the qemu-system-x86_64 binary? As mentioned yup, i mean no, but i initially tested by copying binary and executing it directly, so it was the patched binary. > try the attached patch? The lowest layer of slirp was indeed limited to > 1600-byte frames for no good reason. With this and the virtio driver, I > could exchange 9000-byte packets. ah, thanks! looks good: root@test-host:~# head -c 9000 /dev/zero | nc -u 127.0.0.1 19003 root@test-guest:~# tcpdump -ni eth0 port 19003 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes 12:20:56.484044 IP 10.0.2.2.37331 > 10.0.2.15.19003: UDP, bad length 9000 > 8968 root@test-host:~# head -c 8000 /dev/zero | nc -u 127.0.0.1 19003 root@test-guest:~# tcpdump -ni eth0 port 19003 tcpdump: verbose output suppressed, use -v or -vv for full protocol decode listening on eth0, link-type EN10MB (Ethernet), capture size 262144 bytes 12:25:43.967476 IP 10.0.2.2.47243 > 10.0.2.15.19003: UDP, length 8000 ...with mtu 9000 everywhere. mtu is l2, and complete frame size i assume, so: ip header = 20B, dst-mac + src-mac = 12B great, thanx 1e6! -- Mit freundlichen Grüßen / Kind regards, Chris Heinze *Network-/System-/DevOps-Engineer* *PreciBake GmbH* Gollierstr. 70 80339 München Deutschland / Germany *P:* +49-(0)-89-2154895-30 <+49.89.2154895.30> *F:* +49-(0)-89-2154895-99 *E:* c.hei...@precibake.com *W:* www.precibake.com <http://www.precibake.com/> Handelsregister / Commercial Register: Amtsgericht München, HRB 206356 Steuer-Nr. / Tax-ID143/172/11644 Umsatzsteuer-ID / VAT registration number: DE290040302 Geschäftsführer / Managing Director: Dr. Ingo Stork-Wersborg Der Inhalt dieser E-Mail ist ausschliesslich fuer den/die bezeichneten Empfaenger bestimmt. Wenn Sie nicht der vorgesehene Adressat dieser E-Mail oder dessen Vertreter sein sollten, so beachten Sie bitte, dass jede Form der Kenntnisnahme, Veroeffentlichung, Vervielfaeltigung oder Weitergabe des Inhalts dieser E-Mail unzulaessig ist. Wir bitten Sie, sich in diesem Fall mit dem Absender der E-Mail in Verbindung zu setzen. Wir moechten Sie ausserdem darauf hinweisen, dass die Kommunikation per E-Mail ueber das Internet unsicher ist, da fuer unberechtigte Dritte grundsaetzlich die Moeglichkeit der Kenntnisnahme und Manipulation besteht. The information contained in this email is intended solely for the recipient(s). Access to this email by anyone else is unauthorized. If you are not the intended recipient, any form of disclosure, reproduction, distribution or any action taken or refrained from in reliance on it, is prohibited. Please notify the sender of this email immediately. We also like to inform you that communication via email over the internet is insecure because third parties may have the possibility to access and manipulate emails.
