On Mon, Sep 6, 2010 at 7:19 AM, Nicola Padovano <nicola.padovano@xxxxxxxxx> wrote: > the default value for mtu (in hping) is 16 bytes!!! what does it mean? > maybe hping (against the rfc) use the fragmentation on the IP > __payload__ and not on the whole IP packet...what do you think? you > can check this with wireshark! > in fact i typed this hping line: > > hping -m 160 -d 140 -c 1 localhost Since you use hping, I think it has noting to do with the kernel. Hping fragments packets in user space other than kernel space. > > so we have a IP DATAGRAM size = 140data+20ipheader+20tcpheader > MTU=160 > > but there isn't fragmentation (check it with wireshark) but ip > datagram size is greater than mtu! > > So why there isn't fragmentation? because (i suppose) the > fragmentation work only on the IP payload: > IP paylaod = 140data + 20tcpheader = 160 = MTU => no fragmentation! Fragmentation is in IP layer. sizeof(ip packet) <= MTU. In your case, 140data + 20ipheader = 160 = MTU => no fragmentation. > > what do you think? i'm pretty sure of what i say.... > -- Regards, Changli Gao(xiaosuo@xxxxxxxxx) -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
